TOMOYO Linux Cross Reference
Linux/mm/hugetlb.c

   // SPDX-License-Identifier: GPL-2.0-only
   /*
    * Generic hugetlb support.
    * (C) Nadia Yvette Chambers, April 2004
    */
   #include <linux/list.h>
   #include <linux/init.h>
   #include <linux/mm.h>
   #include <linux/seq_file.h>
  #include <linux/sysctl.h>
  #include <linux/highmem.h>
  #include <linux/mmu_notifier.h>
  #include <linux/nodemask.h>
  #include <linux/pagemap.h>
  #include <linux/mempolicy.h>
  #include <linux/compiler.h>
  #include <linux/cpuset.h>
  #include <linux/mutex.h>
  #include <linux/memblock.h>
  #include <linux/sysfs.h>
  #include <linux/slab.h>
  #include <linux/sched/mm.h>
  #include <linux/mmdebug.h>
  #include <linux/sched/signal.h>
  #include <linux/rmap.h>
  #include <linux/string_helpers.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/jhash.h>
  #include <linux/numa.h>
  #include <linux/llist.h>
  #include <linux/cma.h>
  #include <linux/migrate.h>
  #include <linux/nospec.h>
  #include <linux/delayacct.h>
  #include <linux/memory.h>
  #include <linux/mm_inline.h>
  #include <linux/padata.h>
  
  #include <asm/page.h>
  #include <asm/pgalloc.h>
  #include <asm/tlb.h>
  
  #include <linux/io.h>
  #include <linux/hugetlb.h>
  #include <linux/hugetlb_cgroup.h>
  #include <linux/node.h>
  #include <linux/page_owner.h>
  #include "internal.h"
  #include "hugetlb_vmemmap.h"
  
  int hugetlb_max_hstate __read_mostly;
  unsigned int default_hstate_idx;
  struct hstate hstates[HUGE_MAX_HSTATE];
  
  #ifdef CONFIG_CMA
  static struct cma *hugetlb_cma[MAX_NUMNODES];
  static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata;
  static bool hugetlb_cma_folio(struct folio *folio, unsigned int order)
  {
          return cma_pages_valid(hugetlb_cma[folio_nid(folio)], &folio->page,
                                  1 << order);
  }
  #else
  static bool hugetlb_cma_folio(struct folio *folio, unsigned int order)
  {
          return false;
  }
  #endif
  static unsigned long hugetlb_cma_size __initdata;
  
  __initdata struct list_head huge_boot_pages[MAX_NUMNODES];
  
  /* for command line parsing */
  static struct hstate * __initdata parsed_hstate;
  static unsigned long __initdata default_hstate_max_huge_pages;
  static bool __initdata parsed_valid_hugepagesz = true;
  static bool __initdata parsed_default_hugepagesz;
  static unsigned int default_hugepages_in_node[MAX_NUMNODES] __initdata;
  
  /*
   * Protects updates to hugepage_freelists, hugepage_activelist, nr_huge_pages,
   * free_huge_pages, and surplus_huge_pages.
   */
  DEFINE_SPINLOCK(hugetlb_lock);
  
  /*
   * Serializes faults on the same logical page.  This is used to
   * prevent spurious OOMs when the hugepage pool is fully utilized.
   */
  static int num_fault_mutexes;
  struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;
  
  /* Forward declaration */
  static int hugetlb_acct_memory(struct hstate *h, long delta);
  static void hugetlb_vma_lock_free(struct vm_area_struct *vma);
  static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma);
  static void __hugetlb_vma_unlock_write_free(struct vm_area_struct *vma);
  static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
                 unsigned long start, unsigned long end);
 static struct resv_map *vma_resv_map(struct vm_area_struct *vma);
 
 static inline bool subpool_is_free(struct hugepage_subpool *spool)
 {
         if (spool->count)
                 return false;
         if (spool->max_hpages != -1)
                 return spool->used_hpages == 0;
         if (spool->min_hpages != -1)
                 return spool->rsv_hpages == spool->min_hpages;
 
         return true;
 }
 
 static inline void unlock_or_release_subpool(struct hugepage_subpool *spool,
                                                 unsigned long irq_flags)
 {
         spin_unlock_irqrestore(&spool->lock, irq_flags);
 
         /* If no pages are used, and no other handles to the subpool
          * remain, give up any reservations based on minimum size and
          * free the subpool */
         if (subpool_is_free(spool)) {
                 if (spool->min_hpages != -1)
                         hugetlb_acct_memory(spool->hstate,
                                                 -spool->min_hpages);
                 kfree(spool);
         }
 }
 
 struct hugepage_subpool *hugepage_new_subpool(struct hstate *h, long max_hpages,
                                                 long min_hpages)
 {
         struct hugepage_subpool *spool;
 
         spool = kzalloc(sizeof(*spool), GFP_KERNEL);
         if (!spool)
                 return NULL;
 
         spin_lock_init(&spool->lock);
         spool->count = 1;
         spool->max_hpages = max_hpages;
         spool->hstate = h;
         spool->min_hpages = min_hpages;
 
         if (min_hpages != -1 && hugetlb_acct_memory(h, min_hpages)) {
                 kfree(spool);
                 return NULL;
         }
         spool->rsv_hpages = min_hpages;
 
         return spool;
 }
 
 void hugepage_put_subpool(struct hugepage_subpool *spool)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&spool->lock, flags);
         BUG_ON(!spool->count);
         spool->count--;
         unlock_or_release_subpool(spool, flags);
 }
 
 /*
  * Subpool accounting for allocating and reserving pages.
  * Return -ENOMEM if there are not enough resources to satisfy the
  * request.  Otherwise, return the number of pages by which the
  * global pools must be adjusted (upward).  The returned value may
  * only be different than the passed value (delta) in the case where
  * a subpool minimum size must be maintained.
  */
 static long hugepage_subpool_get_pages(struct hugepage_subpool *spool,
                                       long delta)
 {
         long ret = delta;
 
         if (!spool)
                 return ret;
 
         spin_lock_irq(&spool->lock);
 
         if (spool->max_hpages != -1) {          /* maximum size accounting */
                 if ((spool->used_hpages + delta) <= spool->max_hpages)
                         spool->used_hpages += delta;
                 else {
                         ret = -ENOMEM;
                         goto unlock_ret;
                 }
         }
 
         /* minimum size accounting */
         if (spool->min_hpages != -1 && spool->rsv_hpages) {
                 if (delta > spool->rsv_hpages) {
                         /*
                          * Asking for more reserves than those already taken on
                          * behalf of subpool.  Return difference.
                          */
                         ret = delta - spool->rsv_hpages;
                         spool->rsv_hpages = 0;
                 } else {
                         ret = 0;        /* reserves already accounted for */
                         spool->rsv_hpages -= delta;
                 }
         }
 
 unlock_ret:
         spin_unlock_irq(&spool->lock);
         return ret;
 }
 
 /*
  * Subpool accounting for freeing and unreserving pages.
  * Return the number of global page reservations that must be dropped.
  * The return value may only be different than the passed value (delta)
  * in the case where a subpool minimum size must be maintained.
  */
 static long hugepage_subpool_put_pages(struct hugepage_subpool *spool,
                                        long delta)
 {
         long ret = delta;
         unsigned long flags;
 
         if (!spool)
                 return delta;
 
         spin_lock_irqsave(&spool->lock, flags);
 
         if (spool->max_hpages != -1)            /* maximum size accounting */
                 spool->used_hpages -= delta;
 
          /* minimum size accounting */
         if (spool->min_hpages != -1 && spool->used_hpages < spool->min_hpages) {
                 if (spool->rsv_hpages + delta <= spool->min_hpages)
                         ret = 0;
                 else
                         ret = spool->rsv_hpages + delta - spool->min_hpages;
 
                 spool->rsv_hpages += delta;
                 if (spool->rsv_hpages > spool->min_hpages)
                         spool->rsv_hpages = spool->min_hpages;
         }
 
         /*
          * If hugetlbfs_put_super couldn't free spool due to an outstanding
          * quota reference, free it now.
          */
         unlock_or_release_subpool(spool, flags);
 
         return ret;
 }
 
 static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
 {
         return HUGETLBFS_SB(inode->i_sb)->spool;
 }
 
 static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
 {
         return subpool_inode(file_inode(vma->vm_file));
 }
 
 /*
  * hugetlb vma_lock helper routines
  */
 void hugetlb_vma_lock_read(struct vm_area_struct *vma)
 {
         if (__vma_shareable_lock(vma)) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 down_read(&vma_lock->rw_sema);
         } else if (__vma_private_lock(vma)) {
                 struct resv_map *resv_map = vma_resv_map(vma);
 
                 down_read(&resv_map->rw_sema);
         }
 }
 
 void hugetlb_vma_unlock_read(struct vm_area_struct *vma)
 {
         if (__vma_shareable_lock(vma)) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 up_read(&vma_lock->rw_sema);
         } else if (__vma_private_lock(vma)) {
                 struct resv_map *resv_map = vma_resv_map(vma);
 
                 up_read(&resv_map->rw_sema);
         }
 }
 
 void hugetlb_vma_lock_write(struct vm_area_struct *vma)
 {
         if (__vma_shareable_lock(vma)) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 down_write(&vma_lock->rw_sema);
         } else if (__vma_private_lock(vma)) {
                 struct resv_map *resv_map = vma_resv_map(vma);
 
                 down_write(&resv_map->rw_sema);
         }
 }
 
 void hugetlb_vma_unlock_write(struct vm_area_struct *vma)
 {
         if (__vma_shareable_lock(vma)) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 up_write(&vma_lock->rw_sema);
         } else if (__vma_private_lock(vma)) {
                 struct resv_map *resv_map = vma_resv_map(vma);
 
                 up_write(&resv_map->rw_sema);
         }
 }
 
 int hugetlb_vma_trylock_write(struct vm_area_struct *vma)
 {
 
         if (__vma_shareable_lock(vma)) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 return down_write_trylock(&vma_lock->rw_sema);
         } else if (__vma_private_lock(vma)) {
                 struct resv_map *resv_map = vma_resv_map(vma);
 
                 return down_write_trylock(&resv_map->rw_sema);
         }
 
         return 1;
 }
 
 void hugetlb_vma_assert_locked(struct vm_area_struct *vma)
 {
         if (__vma_shareable_lock(vma)) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 lockdep_assert_held(&vma_lock->rw_sema);
         } else if (__vma_private_lock(vma)) {
                 struct resv_map *resv_map = vma_resv_map(vma);
 
                 lockdep_assert_held(&resv_map->rw_sema);
         }
 }
 
 void hugetlb_vma_lock_release(struct kref *kref)
 {
         struct hugetlb_vma_lock *vma_lock = container_of(kref,
                         struct hugetlb_vma_lock, refs);
 
         kfree(vma_lock);
 }
 
 static void __hugetlb_vma_unlock_write_put(struct hugetlb_vma_lock *vma_lock)
 {
         struct vm_area_struct *vma = vma_lock->vma;
 
         /*
          * vma_lock structure may or not be released as a result of put,
          * it certainly will no longer be attached to vma so clear pointer.
          * Semaphore synchronizes access to vma_lock->vma field.
          */
         vma_lock->vma = NULL;
         vma->vm_private_data = NULL;
         up_write(&vma_lock->rw_sema);
         kref_put(&vma_lock->refs, hugetlb_vma_lock_release);
 }
 
 static void __hugetlb_vma_unlock_write_free(struct vm_area_struct *vma)
 {
         if (__vma_shareable_lock(vma)) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 __hugetlb_vma_unlock_write_put(vma_lock);
         } else if (__vma_private_lock(vma)) {
                 struct resv_map *resv_map = vma_resv_map(vma);
 
                 /* no free for anon vmas, but still need to unlock */
                 up_write(&resv_map->rw_sema);
         }
 }
 
 static void hugetlb_vma_lock_free(struct vm_area_struct *vma)
 {
         /*
          * Only present in sharable vmas.
          */
         if (!vma || !__vma_shareable_lock(vma))
                 return;
 
         if (vma->vm_private_data) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 down_write(&vma_lock->rw_sema);
                 __hugetlb_vma_unlock_write_put(vma_lock);
         }
 }
 
 static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
 {
         struct hugetlb_vma_lock *vma_lock;
 
         /* Only establish in (flags) sharable vmas */
         if (!vma || !(vma->vm_flags & VM_MAYSHARE))
                 return;
 
         /* Should never get here with non-NULL vm_private_data */
         if (vma->vm_private_data)
                 return;
 
         vma_lock = kmalloc(sizeof(*vma_lock), GFP_KERNEL);
         if (!vma_lock) {
                 /*
                  * If we can not allocate structure, then vma can not
                  * participate in pmd sharing.  This is only a possible
                  * performance enhancement and memory saving issue.
                  * However, the lock is also used to synchronize page
                  * faults with truncation.  If the lock is not present,
                  * unlikely races could leave pages in a file past i_size
                  * until the file is removed.  Warn in the unlikely case of
                  * allocation failure.
                  */
                 pr_warn_once("HugeTLB: unable to allocate vma specific lock\n");
                 return;
         }
 
         kref_init(&vma_lock->refs);
         init_rwsem(&vma_lock->rw_sema);
         vma_lock->vma = vma;
         vma->vm_private_data = vma_lock;
 }
 
 /* Helper that removes a struct file_region from the resv_map cache and returns
  * it for use.
  */
 static struct file_region *
 get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
 {
         struct file_region *nrg;
 
         VM_BUG_ON(resv->region_cache_count <= 0);
 
         resv->region_cache_count--;
         nrg = list_first_entry(&resv->region_cache, struct file_region, link);
         list_del(&nrg->link);
 
         nrg->from = from;
         nrg->to = to;
 
         return nrg;
 }
 
 static void copy_hugetlb_cgroup_uncharge_info(struct file_region *nrg,
                                               struct file_region *rg)
 {
 #ifdef CONFIG_CGROUP_HUGETLB
         nrg->reservation_counter = rg->reservation_counter;
         nrg->css = rg->css;
         if (rg->css)
                 css_get(rg->css);
 #endif
 }
 
 /* Helper that records hugetlb_cgroup uncharge info. */
 static void record_hugetlb_cgroup_uncharge_info(struct hugetlb_cgroup *h_cg,
                                                 struct hstate *h,
                                                 struct resv_map *resv,
                                                 struct file_region *nrg)
 {
 #ifdef CONFIG_CGROUP_HUGETLB
         if (h_cg) {
                 nrg->reservation_counter =
                         &h_cg->rsvd_hugepage[hstate_index(h)];
                 nrg->css = &h_cg->css;
                 /*
                  * The caller will hold exactly one h_cg->css reference for the
                  * whole contiguous reservation region. But this area might be
                  * scattered when there are already some file_regions reside in
                  * it. As a result, many file_regions may share only one css
                  * reference. In order to ensure that one file_region must hold
                  * exactly one h_cg->css reference, we should do css_get for
                  * each file_region and leave the reference held by caller
                  * untouched.
                  */
                 css_get(&h_cg->css);
                 if (!resv->pages_per_hpage)
                         resv->pages_per_hpage = pages_per_huge_page(h);
                 /* pages_per_hpage should be the same for all entries in
                  * a resv_map.
                  */
                 VM_BUG_ON(resv->pages_per_hpage != pages_per_huge_page(h));
         } else {
                 nrg->reservation_counter = NULL;
                 nrg->css = NULL;
         }
 #endif
 }
 
 static void put_uncharge_info(struct file_region *rg)
 {
 #ifdef CONFIG_CGROUP_HUGETLB
         if (rg->css)
                 css_put(rg->css);
 #endif
 }
 
 static bool has_same_uncharge_info(struct file_region *rg,
                                    struct file_region *org)
 {
 #ifdef CONFIG_CGROUP_HUGETLB
         return rg->reservation_counter == org->reservation_counter &&
                rg->css == org->css;
 
 #else
         return true;
 #endif
 }
 
 static void coalesce_file_region(struct resv_map *resv, struct file_region *rg)
 {
         struct file_region *nrg, *prg;
 
         prg = list_prev_entry(rg, link);
         if (&prg->link != &resv->regions && prg->to == rg->from &&
             has_same_uncharge_info(prg, rg)) {
                 prg->to = rg->to;
 
                 list_del(&rg->link);
                 put_uncharge_info(rg);
                 kfree(rg);
 
                 rg = prg;
         }
 
         nrg = list_next_entry(rg, link);
         if (&nrg->link != &resv->regions && nrg->from == rg->to &&
             has_same_uncharge_info(nrg, rg)) {
                 nrg->from = rg->from;
 
                 list_del(&rg->link);
                 put_uncharge_info(rg);
                 kfree(rg);
         }
 }
 
 static inline long
 hugetlb_resv_map_add(struct resv_map *map, struct list_head *rg, long from,
                      long to, struct hstate *h, struct hugetlb_cgroup *cg,
                      long *regions_needed)
 {
         struct file_region *nrg;
 
         if (!regions_needed) {
                 nrg = get_file_region_entry_from_cache(map, from, to);
                 record_hugetlb_cgroup_uncharge_info(cg, h, map, nrg);
                 list_add(&nrg->link, rg);
                 coalesce_file_region(map, nrg);
         } else
                 *regions_needed += 1;
 
         return to - from;
 }
 
 /*
  * Must be called with resv->lock held.
  *
  * Calling this with regions_needed != NULL will count the number of pages
  * to be added but will not modify the linked list. And regions_needed will
  * indicate the number of file_regions needed in the cache to carry out to add
  * the regions for this range.
  */
 static long add_reservation_in_range(struct resv_map *resv, long f, long t,
                                      struct hugetlb_cgroup *h_cg,
                                      struct hstate *h, long *regions_needed)
 {
         long add = 0;
         struct list_head *head = &resv->regions;
         long last_accounted_offset = f;
         struct file_region *iter, *trg = NULL;
         struct list_head *rg = NULL;
 
         if (regions_needed)
                 *regions_needed = 0;
 
         /* In this loop, we essentially handle an entry for the range
          * [last_accounted_offset, iter->from), at every iteration, with some
          * bounds checking.
          */
         list_for_each_entry_safe(iter, trg, head, link) {
                 /* Skip irrelevant regions that start before our range. */
                 if (iter->from < f) {
                         /* If this region ends after the last accounted offset,
                          * then we need to update last_accounted_offset.
                          */
                         if (iter->to > last_accounted_offset)
                                 last_accounted_offset = iter->to;
                         continue;
                 }
 
                 /* When we find a region that starts beyond our range, we've
                  * finished.
                  */
                 if (iter->from >= t) {
                         rg = iter->link.prev;
                         break;
                 }
 
                 /* Add an entry for last_accounted_offset -> iter->from, and
                  * update last_accounted_offset.
                  */
                 if (iter->from > last_accounted_offset)
                         add += hugetlb_resv_map_add(resv, iter->link.prev,
                                                     last_accounted_offset,
                                                     iter->from, h, h_cg,
                                                     regions_needed);
 
                 last_accounted_offset = iter->to;
         }
 
         /* Handle the case where our range extends beyond
          * last_accounted_offset.
          */
         if (!rg)
                 rg = head->prev;
         if (last_accounted_offset < t)
                 add += hugetlb_resv_map_add(resv, rg, last_accounted_offset,
                                             t, h, h_cg, regions_needed);
 
         return add;
 }
 
 /* Must be called with resv->lock acquired. Will drop lock to allocate entries.
  */
 static int allocate_file_region_entries(struct resv_map *resv,
                                         int regions_needed)
         __must_hold(&resv->lock)
 {
         LIST_HEAD(allocated_regions);
         int to_allocate = 0, i = 0;
         struct file_region *trg = NULL, *rg = NULL;
 
         VM_BUG_ON(regions_needed < 0);
 
         /*
          * Check for sufficient descriptors in the cache to accommodate
          * the number of in progress add operations plus regions_needed.
          *
          * This is a while loop because when we drop the lock, some other call
          * to region_add or region_del may have consumed some region_entries,
          * so we keep looping here until we finally have enough entries for
          * (adds_in_progress + regions_needed).
          */
         while (resv->region_cache_count <
                (resv->adds_in_progress + regions_needed)) {
                 to_allocate = resv->adds_in_progress + regions_needed -
                               resv->region_cache_count;
 
                 /* At this point, we should have enough entries in the cache
                  * for all the existing adds_in_progress. We should only be
                  * needing to allocate for regions_needed.
                  */
                 VM_BUG_ON(resv->region_cache_count < resv->adds_in_progress);
 
                 spin_unlock(&resv->lock);
                 for (i = 0; i < to_allocate; i++) {
                         trg = kmalloc(sizeof(*trg), GFP_KERNEL);
                         if (!trg)
                                 goto out_of_memory;
                         list_add(&trg->link, &allocated_regions);
                 }
 
                 spin_lock(&resv->lock);
 
                 list_splice(&allocated_regions, &resv->region_cache);
                 resv->region_cache_count += to_allocate;
         }
 
         return 0;
 
 out_of_memory:
         list_for_each_entry_safe(rg, trg, &allocated_regions, link) {
                 list_del(&rg->link);
                 kfree(rg);
         }
         return -ENOMEM;
 }
 
 /*
  * Add the huge page range represented by [f, t) to the reserve
  * map.  Regions will be taken from the cache to fill in this range.
  * Sufficient regions should exist in the cache due to the previous
  * call to region_chg with the same range, but in some cases the cache will not
  * have sufficient entries due to races with other code doing region_add or
  * region_del.  The extra needed entries will be allocated.
  *
  * regions_needed is the out value provided by a previous call to region_chg.
  *
  * Return the number of new huge pages added to the map.  This number is greater
  * than or equal to zero.  If file_region entries needed to be allocated for
  * this operation and we were not able to allocate, it returns -ENOMEM.
  * region_add of regions of length 1 never allocate file_regions and cannot
  * fail; region_chg will always allocate at least 1 entry and a region_add for
  * 1 page will only require at most 1 entry.
  */
 static long region_add(struct resv_map *resv, long f, long t,
                        long in_regions_needed, struct hstate *h,
                        struct hugetlb_cgroup *h_cg)
 {
         long add = 0, actual_regions_needed = 0;
 
         spin_lock(&resv->lock);
 retry:
 
         /* Count how many regions are actually needed to execute this add. */
         add_reservation_in_range(resv, f, t, NULL, NULL,
                                  &actual_regions_needed);
 
         /*
          * Check for sufficient descriptors in the cache to accommodate
          * this add operation. Note that actual_regions_needed may be greater
          * than in_regions_needed, as the resv_map may have been modified since
          * the region_chg call. In this case, we need to make sure that we
          * allocate extra entries, such that we have enough for all the
          * existing adds_in_progress, plus the excess needed for this
          * operation.
          */
         if (actual_regions_needed > in_regions_needed &&
             resv->region_cache_count <
                     resv->adds_in_progress +
                             (actual_regions_needed - in_regions_needed)) {
                 /* region_add operation of range 1 should never need to
                  * allocate file_region entries.
                  */
                 VM_BUG_ON(t - f <= 1);
 
                 if (allocate_file_region_entries(
                             resv, actual_regions_needed - in_regions_needed)) {
                         return -ENOMEM;
                 }
 
                 goto retry;
         }
 
         add = add_reservation_in_range(resv, f, t, h_cg, h, NULL);
 
         resv->adds_in_progress -= in_regions_needed;
 
         spin_unlock(&resv->lock);
         return add;
 }
 
 /*
  * Examine the existing reserve map and determine how many
  * huge pages in the specified range [f, t) are NOT currently
  * represented.  This routine is called before a subsequent
  * call to region_add that will actually modify the reserve
  * map to add the specified range [f, t).  region_chg does
  * not change the number of huge pages represented by the
  * map.  A number of new file_region structures is added to the cache as a
  * placeholder, for the subsequent region_add call to use. At least 1
  * file_region structure is added.
  *
  * out_regions_needed is the number of regions added to the
  * resv->adds_in_progress.  This value needs to be provided to a follow up call
  * to region_add or region_abort for proper accounting.
  *
  * Returns the number of huge pages that need to be added to the existing
  * reservation map for the range [f, t).  This number is greater or equal to
  * zero.  -ENOMEM is returned if a new file_region structure or cache entry
  * is needed and can not be allocated.
  */
 static long region_chg(struct resv_map *resv, long f, long t,
                        long *out_regions_needed)
 {
         long chg = 0;
 
         spin_lock(&resv->lock);
 
         /* Count how many hugepages in this range are NOT represented. */
         chg = add_reservation_in_range(resv, f, t, NULL, NULL,
                                        out_regions_needed);
 
         if (*out_regions_needed == 0)
                 *out_regions_needed = 1;
 
         if (allocate_file_region_entries(resv, *out_regions_needed))
                 return -ENOMEM;
 
         resv->adds_in_progress += *out_regions_needed;
 
         spin_unlock(&resv->lock);
         return chg;
 }
 
 /*
  * Abort the in progress add operation.  The adds_in_progress field
  * of the resv_map keeps track of the operations in progress between
  * calls to region_chg and region_add.  Operations are sometimes
  * aborted after the call to region_chg.  In such cases, region_abort
  * is called to decrement the adds_in_progress counter. regions_needed
  * is the value returned by the region_chg call, it is used to decrement
  * the adds_in_progress counter.
  *
  * NOTE: The range arguments [f, t) are not needed or used in this
  * routine.  They are kept to make reading the calling code easier as
  * arguments will match the associated region_chg call.
  */
 static void region_abort(struct resv_map *resv, long f, long t,
                          long regions_needed)
 {
         spin_lock(&resv->lock);
         VM_BUG_ON(!resv->region_cache_count);
         resv->adds_in_progress -= regions_needed;
         spin_unlock(&resv->lock);
 }
 
 /*
  * Delete the specified range [f, t) from the reserve map.  If the
  * t parameter is LONG_MAX, this indicates that ALL regions after f
  * should be deleted.  Locate the regions which intersect [f, t)
  * and either trim, delete or split the existing regions.
  *
  * Returns the number of huge pages deleted from the reserve map.
  * In the normal case, the return value is zero or more.  In the
  * case where a region must be split, a new region descriptor must
  * be allocated.  If the allocation fails, -ENOMEM will be returned.
  * NOTE: If the parameter t == LONG_MAX, then we will never split
  * a region and possibly return -ENOMEM.  Callers specifying
  * t == LONG_MAX do not need to check for -ENOMEM error.
  */
 static long region_del(struct resv_map *resv, long f, long t)
 {
         struct list_head *head = &resv->regions;
         struct file_region *rg, *trg;
         struct file_region *nrg = NULL;
         long del = 0;
 
 retry:
         spin_lock(&resv->lock);
         list_for_each_entry_safe(rg, trg, head, link) {
                 /*
                  * Skip regions before the range to be deleted.  file_region
                  * ranges are normally of the form [from, to).  However, there
                  * may be a "placeholder" entry in the map which is of the form
                  * (from, to) with from == to.  Check for placeholder entries
                  * at the beginning of the range to be deleted.
                  */
                 if (rg->to <= f && (rg->to != rg->from || rg->to != f))
                         continue;
 
                 if (rg->from >= t)
                         break;
 
                 if (f > rg->from && t < rg->to) { /* Must split region */
                         /*
                          * Check for an entry in the cache before dropping
                          * lock and attempting allocation.
                          */
                         if (!nrg &&
                             resv->region_cache_count > resv->adds_in_progress) {
                                 nrg = list_first_entry(&resv->region_cache,
                                                         struct file_region,
                                                         link);
                                 list_del(&nrg->link);
                                 resv->region_cache_count--;
                         }
 
                         if (!nrg) {
                                 spin_unlock(&resv->lock);
                                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
                                 if (!nrg)
                                         return -ENOMEM;
                                 goto retry;
                         }
 
                         del += t - f;
                         hugetlb_cgroup_uncharge_file_region(
                                 resv, rg, t - f, false);
 
                         /* New entry for end of split region */
                         nrg->from = t;
                         nrg->to = rg->to;
 
                         copy_hugetlb_cgroup_uncharge_info(nrg, rg);
 
                         INIT_LIST_HEAD(&nrg->link);
 
                         /* Original entry is trimmed */
                         rg->to = f;
 
                         list_add(&nrg->link, &rg->link);
                         nrg = NULL;
                         break;
                 }
 
                 if (f <= rg->from && t >= rg->to) { /* Remove entire region */
                         del += rg->to - rg->from;
                         hugetlb_cgroup_uncharge_file_region(resv, rg,
                                                             rg->to - rg->from, true);
                         list_del(&rg->link);
                         kfree(rg);
                         continue;
                 }
 
                 if (f <= rg->from) {    /* Trim beginning of region */
                         hugetlb_cgroup_uncharge_file_region(resv, rg,
                                                             t - rg->from, false);
 
                         del += t - rg->from;
                         rg->from = t;
                 } else {                /* Trim end of region */
                         hugetlb_cgroup_uncharge_file_region(resv, rg,
                                                             rg->to - f, false);
 
                         del += rg->to - f;
                         rg->to = f;
                 }
         }
 
         spin_unlock(&resv->lock);
         kfree(nrg);
         return del;
 }
 
 /*
  * A rare out of memory error was encountered which prevented removal of
  * the reserve map region for a page.  The huge page itself was free'ed
  * and removed from the page cache.  This routine will adjust the subpool
  * usage count, and the global reserve count if needed.  By incrementing
  * these counts, the reserve map entry which could not be deleted will
  * appear as a "reserved" entry instead of simply dangling with incorrect
  * counts.
  */
 void hugetlb_fix_reserve_counts(struct inode *inode)
 {
         struct hugepage_subpool *spool = subpool_inode(inode);
         long rsv_adjust;
         bool reserved = false;
 
         rsv_adjust = hugepage_subpool_get_pages(spool, 1);
         if (rsv_adjust > 0) {
                 struct hstate *h = hstate_inode(inode);
 
                 if (!hugetlb_acct_memory(h, 1))
                         reserved = true;
         } else if (!rsv_adjust) {
                 reserved = true;
         }
 
         if (!reserved)
                 pr_warn("hugetlb: Huge Page Reserved count may go negative.\n");
 }
 
 /*
  * Count and return the number of huge pages in the reserve map
  * that intersect with the range [f, t).
  */
 static long region_count(struct resv_map *resv, long f, long t)
 {
         struct list_head *head = &resv->regions;
         struct file_region *rg;
         long chg = 0;
 
         spin_lock(&resv->lock);
         /* Locate each segment we overlap with, and count that overlap. */
         list_for_each_entry(rg, head, link) {
                 long seg_from;
                 long seg_to;
 
                 if (rg->to <= f)
                         continue;
                 if (rg->from >= t)
                         break;
 
                 seg_from = max(rg->from, f);
                 seg_to = min(rg->to, t);
 
                 chg += seg_to - seg_from;
         }
         spin_unlock(&resv->lock);
 
         return chg;
 }
 
 /*
  * Convert the address within this vma to the page offset within
  * the mapping, huge page units here.
  */
 static pgoff_t vma_hugecache_offset(struct hstate *h,
                         struct vm_area_struct *vma, unsigned long address)
 {
         return ((address - vma->vm_start) >> huge_page_shift(h)) +
                         (vma->vm_pgoff >> huge_page_order(h));
 }
 
 /**
  * vma_kernel_pagesize - Page size granularity for this VMA.
  * @vma: The user mapping.
  *
  * Folios in this VMA will be aligned to, and at least the size of the
  * number of bytes returned by this function.
  *
  * Return: The default size of the folios allocated when backing a VMA.
  */
 unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
 {
         if (vma->vm_ops && vma->vm_ops->pagesize)
                 return vma->vm_ops->pagesize(vma);
         return PAGE_SIZE;
 }
 EXPORT_SYMBOL_GPL(vma_kernel_pagesize);
 
 /*
  * Return the page size being used by the MMU to back a VMA. In the majority
  * of cases, the page size used by the kernel matches the MMU size. On
  * architectures where it differs, an architecture-specific 'strong'
  * version of this symbol is required.
  */
 __weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
 {
         return vma_kernel_pagesize(vma);
 }
 
 /*
  * Flags for MAP_PRIVATE reservations.  These are stored in the bottom
  * bits of the reservation map pointer, which are always clear due to
  * alignment.
  */
 #define HPAGE_RESV_OWNER    (1UL << 0)
 #define HPAGE_RESV_UNMAPPED (1UL << 1)
 #define HPAGE_RESV_MASK (HPAGE_RESV_OWNER | HPAGE_RESV_UNMAPPED)
 
 /*
  * These helpers are used to track how many pages are reserved for
  * faults in a MAP_PRIVATE mapping. Only the process that called mmap()
  * is guaranteed to have their future faults succeed.
  *
  * With the exception of hugetlb_dup_vma_private() which is called at fork(),
  * the reserve counters are updated with the hugetlb_lock held. It is safe
  * to reset the VMA at fork() time as it is not in use yet and there is no
  * chance of the global counters getting corrupted as a result of the values.
  *
  * The private mapping reservation is represented in a subtly different
  * manner to a shared mapping.  A shared mapping has a region map associated
  * with the underlying file, this region map represents the backing file
  * pages which have ever had a reservation assigned which this persists even
  * after the page is instantiated.  A private mapping has a region map
  * associated with the original mmap which is attached to all VMAs which
  * reference it, this region map represents those offsets which have consumed
  * reservation ie. where pages have been instantiated.
  */
 static unsigned long get_vma_private_data(struct vm_area_struct *vma)
 {
         return (unsigned long)vma->vm_private_data;
 }
 
 static void set_vma_private_data(struct vm_area_struct *vma,
                                                         unsigned long value)
 {
         vma->vm_private_data = (void *)value;
 }
 
 static void
 resv_map_set_hugetlb_cgroup_uncharge_info(struct resv_map *resv_map,
                                           struct hugetlb_cgroup *h_cg,
                                           struct hstate *h)
 {
 #ifdef CONFIG_CGROUP_HUGETLB
         if (!h_cg || !h) {
                 resv_map->reservation_counter = NULL;
                 resv_map->pages_per_hpage = 0;
                 resv_map->css = NULL;
         } else {
                 resv_map->reservation_counter =
                         &h_cg->rsvd_hugepage[hstate_index(h)];
                 resv_map->pages_per_hpage = pages_per_huge_page(h);
                 resv_map->css = &h_cg->css;
         }
 #endif
 }
 
 struct resv_map *resv_map_alloc(void)
 {
         struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
         struct file_region *rg = kmalloc(sizeof(*rg), GFP_KERNEL);
 
         if (!resv_map || !rg) {
                 kfree(resv_map);
                 kfree(rg);
                 return NULL;
         }
 
         kref_init(&resv_map->refs);
         spin_lock_init(&resv_map->lock);
         INIT_LIST_HEAD(&resv_map->regions);
         init_rwsem(&resv_map->rw_sema);
 
         resv_map->adds_in_progress = 0;
         /*
          * Initialize these to 0. On shared mappings, 0's here indicate these
          * fields don't do cgroup accounting. On private mappings, these will be
          * re-initialized to the proper values, to indicate that hugetlb cgroup
          * reservations are to be un-charged from here.
          */
         resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, NULL, NULL);
 
         INIT_LIST_HEAD(&resv_map->region_cache);
         list_add(&rg->link, &resv_map->region_cache);
         resv_map->region_cache_count = 1;
 
         return resv_map;
 }
 
 void resv_map_release(struct kref *ref)
 {
         struct resv_map *resv_map = container_of(ref, struct resv_map, refs);
         struct list_head *head = &resv_map->region_cache;
         struct file_region *rg, *trg;
 
         /* Clear out any active regions before we release the map. */
         region_del(resv_map, 0, LONG_MAX);
 
         /* ... and any entries left in the cache */
         list_for_each_entry_safe(rg, trg, head, link) {
                 list_del(&rg->link);
                 kfree(rg);
         }
 
         VM_BUG_ON(resv_map->adds_in_progress);
 
         kfree(resv_map);
 }
 
 static inline struct resv_map *inode_resv_map(struct inode *inode)
 {
         /*
          * At inode evict time, i_mapping may not point to the original
          * address space within the inode.  This original address space
          * contains the pointer to the resv_map.  So, always use the
          * address space embedded within the inode.
          * The VERY common case is inode->mapping == &inode->i_data but,
          * this may not be true for device special inodes.
          */
         return (struct resv_map *)(&inode->i_data)->i_private_data;
 }
 
 static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
 {
         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
         if (vma->vm_flags & VM_MAYSHARE) {
                 struct address_space *mapping = vma->vm_file->f_mapping;
                 struct inode *inode = mapping->host;
 
                 return inode_resv_map(inode);
 
         } else {
                 return (struct resv_map *)(get_vma_private_data(vma) &
                                                         ~HPAGE_RESV_MASK);
         }
 }
 
 static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
 {
         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
         VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);
 
         set_vma_private_data(vma, (unsigned long)map);
 }
 
 static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
 {
         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
         VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);
 
         set_vma_private_data(vma, get_vma_private_data(vma) | flags);
 }
 
 static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
 {
         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
 
         return (get_vma_private_data(vma) & flag) != 0;
 }
 
 bool __vma_private_lock(struct vm_area_struct *vma)
 {
         return !(vma->vm_flags & VM_MAYSHARE) &&
                 get_vma_private_data(vma) & ~HPAGE_RESV_MASK &&
                 is_vma_resv_set(vma, HPAGE_RESV_OWNER);
 }
 
 void hugetlb_dup_vma_private(struct vm_area_struct *vma)
 {
         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
         /*
          * Clear vm_private_data
          * - For shared mappings this is a per-vma semaphore that may be
          *   allocated in a subsequent call to hugetlb_vm_op_open.
          *   Before clearing, make sure pointer is not associated with vma
          *   as this will leak the structure.  This is the case when called
          *   via clear_vma_resv_huge_pages() and hugetlb_vm_op_open has already
          *   been called to allocate a new structure.
          * - For MAP_PRIVATE mappings, this is the reserve map which does
          *   not apply to children.  Faults generated by the children are
          *   not guaranteed to succeed, even if read-only.
          */
         if (vma->vm_flags & VM_MAYSHARE) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 if (vma_lock && vma_lock->vma != vma)
                         vma->vm_private_data = NULL;
         } else
                 vma->vm_private_data = NULL;
 }
 
 /*
  * Reset and decrement one ref on hugepage private reservation.
  * Called with mm->mmap_lock writer semaphore held.
  * This function should be only used by move_vma() and operate on
  * same sized vma. It should never come here with last ref on the
  * reservation.
  */
 void clear_vma_resv_huge_pages(struct vm_area_struct *vma)
 {
         /*
          * Clear the old hugetlb private page reservation.
          * It has already been transferred to new_vma.
          *
          * During a mremap() operation of a hugetlb vma we call move_vma()
          * which copies vma into new_vma and unmaps vma. After the copy
          * operation both new_vma and vma share a reference to the resv_map
          * struct, and at that point vma is about to be unmapped. We don't
          * want to return the reservation to the pool at unmap of vma because
          * the reservation still lives on in new_vma, so simply decrement the
          * ref here and remove the resv_map reference from this vma.
          */
         struct resv_map *reservations = vma_resv_map(vma);
 
         if (reservations && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
                 resv_map_put_hugetlb_cgroup_uncharge_info(reservations);
                 kref_put(&reservations->refs, resv_map_release);
         }
 
         hugetlb_dup_vma_private(vma);
 }
 
 /* Returns true if the VMA has associated reserve pages */
 static bool vma_has_reserves(struct vm_area_struct *vma, long chg)
 {
         if (vma->vm_flags & VM_NORESERVE) {
                 /*
                  * This address is already reserved by other process(chg == 0),
                  * so, we should decrement reserved count. Without decrementing,
                  * reserve count remains after releasing inode, because this
                  * allocated page will go into page cache and is regarded as
                  * coming from reserved pool in releasing step.  Currently, we
                  * don't have any other solution to deal with this situation
                  * properly, so add work-around here.
                  */
                 if (vma->vm_flags & VM_MAYSHARE && chg == 0)
                         return true;
                 else
                         return false;
         }
 
         /* Shared mappings always use reserves */
         if (vma->vm_flags & VM_MAYSHARE) {
                 /*
                  * We know VM_NORESERVE is not set.  Therefore, there SHOULD
                  * be a region map for all pages.  The only situation where
                  * there is no region map is if a hole was punched via
                  * fallocate.  In this case, there really are no reserves to
                  * use.  This situation is indicated if chg != 0.
                  */
                 if (chg)
                         return false;
                 else
                         return true;
         }
 
         /*
          * Only the process that called mmap() has reserves for
          * private mappings.
          */
         if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
                 /*
                  * Like the shared case above, a hole punch or truncate
                  * could have been performed on the private mapping.
                  * Examine the value of chg to determine if reserves
                  * actually exist or were previously consumed.
                  * Very Subtle - The value of chg comes from a previous
                  * call to vma_needs_reserves().  The reserve map for
                  * private mappings has different (opposite) semantics
                  * than that of shared mappings.  vma_needs_reserves()
                  * has already taken this difference in semantics into
                  * account.  Therefore, the meaning of chg is the same
                  * as in the shared case above.  Code could easily be
                  * combined, but keeping it separate draws attention to
                  * subtle differences.
                  */
                 if (chg)
                         return false;
                 else
                         return true;
         }
 
         return false;
 }
 
 static void enqueue_hugetlb_folio(struct hstate *h, struct folio *folio)
 {
         int nid = folio_nid(folio);
 
         lockdep_assert_held(&hugetlb_lock);
         VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);
 
         list_move(&folio->lru, &h->hugepage_freelists[nid]);
         h->free_huge_pages++;
         h->free_huge_pages_node[nid]++;
         folio_set_hugetlb_freed(folio);
 }
 
 static struct folio *dequeue_hugetlb_folio_node_exact(struct hstate *h,
                                                                 int nid)
 {
         struct folio *folio;
         bool pin = !!(current->flags & PF_MEMALLOC_PIN);
 
         lockdep_assert_held(&hugetlb_lock);
         list_for_each_entry(folio, &h->hugepage_freelists[nid], lru) {
                 if (pin && !folio_is_longterm_pinnable(folio))
                         continue;
 
                 if (folio_test_hwpoison(folio))
                         continue;
 
                 list_move(&folio->lru, &h->hugepage_activelist);
                 folio_ref_unfreeze(folio, 1);
                 folio_clear_hugetlb_freed(folio);
                 h->free_huge_pages--;
                 h->free_huge_pages_node[nid]--;
                 return folio;
         }
 
         return NULL;
 }
 
 static struct folio *dequeue_hugetlb_folio_nodemask(struct hstate *h, gfp_t gfp_mask,
                                                         int nid, nodemask_t *nmask)
 {
         unsigned int cpuset_mems_cookie;
         struct zonelist *zonelist;
         struct zone *zone;
         struct zoneref *z;
         int node = NUMA_NO_NODE;
 
         /* 'nid' should not be NUMA_NO_NODE. Try to catch any misuse of it and rectifiy. */
         if (nid == NUMA_NO_NODE)
                 nid = numa_node_id();
 
         zonelist = node_zonelist(nid, gfp_mask);
 
 retry_cpuset:
         cpuset_mems_cookie = read_mems_allowed_begin();
         for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nmask) {
                 struct folio *folio;
 
                 if (!cpuset_zone_allowed(zone, gfp_mask))
                         continue;
                 /*
                  * no need to ask again on the same node. Pool is node rather than
                  * zone aware
                  */
                 if (zone_to_nid(zone) == node)
                         continue;
                 node = zone_to_nid(zone);
 
                 folio = dequeue_hugetlb_folio_node_exact(h, node);
                 if (folio)
                         return folio;
         }
         if (unlikely(read_mems_allowed_retry(cpuset_mems_cookie)))
                 goto retry_cpuset;
 
         return NULL;
 }
 
 static unsigned long available_huge_pages(struct hstate *h)
 {
         return h->free_huge_pages - h->resv_huge_pages;
 }
 
 static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
                                 struct vm_area_struct *vma,
                                 unsigned long address, int avoid_reserve,
                                 long chg)
 {
         struct folio *folio = NULL;
         struct mempolicy *mpol;
         gfp_t gfp_mask;
         nodemask_t *nodemask;
         int nid;
 
         /*
          * A child process with MAP_PRIVATE mappings created by their parent
          * have no page reserves. This check ensures that reservations are
          * not "stolen". The child may still get SIGKILLed
          */
         if (!vma_has_reserves(vma, chg) && !available_huge_pages(h))
                 goto err;
 
         /* If reserves cannot be used, ensure enough pages are in the pool */
         if (avoid_reserve && !available_huge_pages(h))
                 goto err;
 
         gfp_mask = htlb_alloc_mask(h);
         nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
 
         if (mpol_is_preferred_many(mpol)) {
                 folio = dequeue_hugetlb_folio_nodemask(h, gfp_mask,
                                                         nid, nodemask);
 
                 /* Fallback to all nodes if page==NULL */
                 nodemask = NULL;
         }
 
         if (!folio)
                 folio = dequeue_hugetlb_folio_nodemask(h, gfp_mask,
                                                         nid, nodemask);
 
         if (folio && !avoid_reserve && vma_has_reserves(vma, chg)) {
                 folio_set_hugetlb_restore_reserve(folio);
                 h->resv_huge_pages--;
         }
 
         mpol_cond_put(mpol);
         return folio;
 
 err:
         return NULL;
 }
 
 /*
  * common helper functions for hstate_next_node_to_{alloc|free}.
  * We may have allocated or freed a huge page based on a different
  * nodes_allowed previously, so h->next_node_to_{alloc|free} might
  * be outside of *nodes_allowed.  Ensure that we use an allowed
  * node for alloc or free.
  */
 static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
 {
         nid = next_node_in(nid, *nodes_allowed);
         VM_BUG_ON(nid >= MAX_NUMNODES);
 
         return nid;
 }
 
 static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
 {
         if (!node_isset(nid, *nodes_allowed))
                 nid = next_node_allowed(nid, nodes_allowed);
         return nid;
 }
 
 /*
  * returns the previously saved node ["this node"] from which to
  * allocate a persistent huge page for the pool and advance the
  * next node from which to allocate, handling wrap at end of node
  * mask.
  */
 static int hstate_next_node_to_alloc(int *next_node,
                                         nodemask_t *nodes_allowed)
 {
         int nid;
 
         VM_BUG_ON(!nodes_allowed);
 
         nid = get_valid_node_allowed(*next_node, nodes_allowed);
         *next_node = next_node_allowed(nid, nodes_allowed);
 
         return nid;
 }
 
 /*
  * helper for remove_pool_hugetlb_folio() - return the previously saved
  * node ["this node"] from which to free a huge page.  Advance the
  * next node id whether or not we find a free huge page to free so
  * that the next attempt to free addresses the next node.
  */
 static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
 {
         int nid;
 
         VM_BUG_ON(!nodes_allowed);
 
         nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
         h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);
 
         return nid;
 }
 
 #define for_each_node_mask_to_alloc(next_node, nr_nodes, node, mask)            \
         for (nr_nodes = nodes_weight(*mask);                            \
                 nr_nodes > 0 &&                                         \
                 ((node = hstate_next_node_to_alloc(next_node, mask)) || 1);     \
                 nr_nodes--)
 
 #define for_each_node_mask_to_free(hs, nr_nodes, node, mask)            \
         for (nr_nodes = nodes_weight(*mask);                            \
                 nr_nodes > 0 &&                                         \
                 ((node = hstate_next_node_to_free(hs, mask)) || 1);     \
                 nr_nodes--)
 
 /* used to demote non-gigantic_huge pages as well */
 static void __destroy_compound_gigantic_folio(struct folio *folio,
                                         unsigned int order, bool demote)
 {
         int i;
         int nr_pages = 1 << order;
         struct page *p;
 
         atomic_set(&folio->_entire_mapcount, 0);
         atomic_set(&folio->_large_mapcount, 0);
         atomic_set(&folio->_pincount, 0);
 
         for (i = 1; i < nr_pages; i++) {
                 p = folio_page(folio, i);
                 p->flags &= ~PAGE_FLAGS_CHECK_AT_FREE;
                 p->mapping = NULL;
                 clear_compound_head(p);
                 if (!demote)
                         set_page_refcounted(p);
         }
 
         __folio_clear_head(folio);
 }
 
 static void destroy_compound_hugetlb_folio_for_demote(struct folio *folio,
                                         unsigned int order)
 {
         __destroy_compound_gigantic_folio(folio, order, true);
 }
 
 #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
 static void destroy_compound_gigantic_folio(struct folio *folio,
                                         unsigned int order)
 {
         __destroy_compound_gigantic_folio(folio, order, false);
 }
 
 static void free_gigantic_folio(struct folio *folio, unsigned int order)
 {
         /*
          * If the page isn't allocated using the cma allocator,
          * cma_release() returns false.
          */
 #ifdef CONFIG_CMA
         int nid = folio_nid(folio);
 
         if (cma_release(hugetlb_cma[nid], &folio->page, 1 << order))
                 return;
 #endif
 
         free_contig_range(folio_pfn(folio), 1 << order);
 }
 
 #ifdef CONFIG_CONTIG_ALLOC
 static struct folio *alloc_gigantic_folio(struct hstate *h, gfp_t gfp_mask,
                 int nid, nodemask_t *nodemask)
 {
         struct page *page;
         unsigned long nr_pages = pages_per_huge_page(h);
         if (nid == NUMA_NO_NODE)
                 nid = numa_mem_id();
 
 #ifdef CONFIG_CMA
         {
                 int node;
 
                 if (hugetlb_cma[nid]) {
                         page = cma_alloc(hugetlb_cma[nid], nr_pages,
                                         huge_page_order(h), true);
                         if (page)
                                 return page_folio(page);
                 }
 
                 if (!(gfp_mask & __GFP_THISNODE)) {
                         for_each_node_mask(node, *nodemask) {
                                 if (node == nid || !hugetlb_cma[node])
                                         continue;
 
                                 page = cma_alloc(hugetlb_cma[node], nr_pages,
                                                 huge_page_order(h), true);
                                 if (page)
                                         return page_folio(page);
                         }
                 }
         }
 #endif
 
         page = alloc_contig_pages(nr_pages, gfp_mask, nid, nodemask);
         return page ? page_folio(page) : NULL;
 }
 
 #else /* !CONFIG_CONTIG_ALLOC */
 static struct folio *alloc_gigantic_folio(struct hstate *h, gfp_t gfp_mask,
                                         int nid, nodemask_t *nodemask)
 {
         return NULL;
 }
 #endif /* CONFIG_CONTIG_ALLOC */
 
 #else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
 static struct folio *alloc_gigantic_folio(struct hstate *h, gfp_t gfp_mask,
                                         int nid, nodemask_t *nodemask)
 {
         return NULL;
 }
 static inline void free_gigantic_folio(struct folio *folio,
                                                 unsigned int order) { }
 static inline void destroy_compound_gigantic_folio(struct folio *folio,
                                                 unsigned int order) { }
 #endif
 
 /*
  * Remove hugetlb folio from lists.
  * If vmemmap exists for the folio, clear the hugetlb flag so that the
  * folio appears as just a compound page.  Otherwise, wait until after
  * allocating vmemmap to clear the flag.
  *
  * Must be called with hugetlb lock held.
  */
 static void remove_hugetlb_folio(struct hstate *h, struct folio *folio,
                                                         bool adjust_surplus)
 {
         int nid = folio_nid(folio);
 
         VM_BUG_ON_FOLIO(hugetlb_cgroup_from_folio(folio), folio);
         VM_BUG_ON_FOLIO(hugetlb_cgroup_from_folio_rsvd(folio), folio);
 
         lockdep_assert_held(&hugetlb_lock);
         if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                 return;
 
         list_del(&folio->lru);
 
         if (folio_test_hugetlb_freed(folio)) {
                 folio_clear_hugetlb_freed(folio);
                 h->free_huge_pages--;
                 h->free_huge_pages_node[nid]--;
         }
         if (adjust_surplus) {
                 h->surplus_huge_pages--;
                 h->surplus_huge_pages_node[nid]--;
         }
 
         /*
          * We can only clear the hugetlb flag after allocating vmemmap
          * pages.  Otherwise, someone (memory error handling) may try to write
          * to tail struct pages.
          */
         if (!folio_test_hugetlb_vmemmap_optimized(folio))
                 __folio_clear_hugetlb(folio);
 
         h->nr_huge_pages--;
         h->nr_huge_pages_node[nid]--;
 }
 
 static void add_hugetlb_folio(struct hstate *h, struct folio *folio,
                              bool adjust_surplus)
 {
         int nid = folio_nid(folio);
 
         VM_BUG_ON_FOLIO(!folio_test_hugetlb_vmemmap_optimized(folio), folio);
 
         lockdep_assert_held(&hugetlb_lock);
 
         INIT_LIST_HEAD(&folio->lru);
         h->nr_huge_pages++;
         h->nr_huge_pages_node[nid]++;
 
         if (adjust_surplus) {
                 h->surplus_huge_pages++;
                 h->surplus_huge_pages_node[nid]++;
         }
 
         __folio_set_hugetlb(folio);
         folio_change_private(folio, NULL);
         /*
          * We have to set hugetlb_vmemmap_optimized again as above
          * folio_change_private(folio, NULL) cleared it.
          */
         folio_set_hugetlb_vmemmap_optimized(folio);
 
         arch_clear_hugetlb_flags(folio);
         enqueue_hugetlb_folio(h, folio);
 }
 
 static void __update_and_free_hugetlb_folio(struct hstate *h,
                                                 struct folio *folio)
 {
         bool clear_flag = folio_test_hugetlb_vmemmap_optimized(folio);
 
         if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                 return;
 
         /*
          * If we don't know which subpages are hwpoisoned, we can't free
          * the hugepage, so it's leaked intentionally.
          */
         if (folio_test_hugetlb_raw_hwp_unreliable(folio))
                 return;
 
         /*
          * If folio is not vmemmap optimized (!clear_flag), then the folio
          * is no longer identified as a hugetlb page.  hugetlb_vmemmap_restore_folio
          * can only be passed hugetlb pages and will BUG otherwise.
          */
         if (clear_flag && hugetlb_vmemmap_restore_folio(h, folio)) {
                 spin_lock_irq(&hugetlb_lock);
                 /*
                  * If we cannot allocate vmemmap pages, just refuse to free the
                  * page and put the page back on the hugetlb free list and treat
                  * as a surplus page.
                  */
                 add_hugetlb_folio(h, folio, true);
                 spin_unlock_irq(&hugetlb_lock);
                 return;
         }
 
         /*
          * If vmemmap pages were allocated above, then we need to clear the
          * hugetlb flag under the hugetlb lock.
          */
         if (folio_test_hugetlb(folio)) {
                 spin_lock_irq(&hugetlb_lock);
                 __folio_clear_hugetlb(folio);
                 spin_unlock_irq(&hugetlb_lock);
         }
 
         /*
          * Move PageHWPoison flag from head page to the raw error pages,
          * which makes any healthy subpages reusable.
          */
         if (unlikely(folio_test_hwpoison(folio)))
                 folio_clear_hugetlb_hwpoison(folio);
 
         folio_ref_unfreeze(folio, 1);
 
         /*
          * Non-gigantic pages demoted from CMA allocated gigantic pages
          * need to be given back to CMA in free_gigantic_folio.
          */
         if (hstate_is_gigantic(h) ||
             hugetlb_cma_folio(folio, huge_page_order(h))) {
                 destroy_compound_gigantic_folio(folio, huge_page_order(h));
                 free_gigantic_folio(folio, huge_page_order(h));
         } else {
                 INIT_LIST_HEAD(&folio->_deferred_list);
                 folio_put(folio);
         }
 }
 
 /*
  * As update_and_free_hugetlb_folio() can be called under any context, so we cannot
  * use GFP_KERNEL to allocate vmemmap pages. However, we can defer the
  * actual freeing in a workqueue to prevent from using GFP_ATOMIC to allocate
  * the vmemmap pages.
  *
  * free_hpage_workfn() locklessly retrieves the linked list of pages to be
  * freed and frees them one-by-one. As the page->mapping pointer is going
  * to be cleared in free_hpage_workfn() anyway, it is reused as the llist_node
  * structure of a lockless linked list of huge pages to be freed.
  */
 static LLIST_HEAD(hpage_freelist);
 
 static void free_hpage_workfn(struct work_struct *work)
 {
         struct llist_node *node;
 
         node = llist_del_all(&hpage_freelist);
 
         while (node) {
                 struct folio *folio;
                 struct hstate *h;
 
                 folio = container_of((struct address_space **)node,
                                      struct folio, mapping);
                 node = node->next;
                 folio->mapping = NULL;
                 /*
                  * The VM_BUG_ON_FOLIO(!folio_test_hugetlb(folio), folio) in
                  * folio_hstate() is going to trigger because a previous call to
                  * remove_hugetlb_folio() will clear the hugetlb bit, so do
                  * not use folio_hstate() directly.
                  */
                 h = size_to_hstate(folio_size(folio));
 
                 __update_and_free_hugetlb_folio(h, folio);
 
                 cond_resched();
         }
 }
 static DECLARE_WORK(free_hpage_work, free_hpage_workfn);
 
 static inline void flush_free_hpage_work(struct hstate *h)
 {
         if (hugetlb_vmemmap_optimizable(h))
                 flush_work(&free_hpage_work);
 }
 
 static void update_and_free_hugetlb_folio(struct hstate *h, struct folio *folio,
                                  bool atomic)
 {
         if (!folio_test_hugetlb_vmemmap_optimized(folio) || !atomic) {
                 __update_and_free_hugetlb_folio(h, folio);
                 return;
         }
 
         /*
          * Defer freeing to avoid using GFP_ATOMIC to allocate vmemmap pages.
          *
          * Only call schedule_work() if hpage_freelist is previously
          * empty. Otherwise, schedule_work() had been called but the workfn
          * hasn't retrieved the list yet.
          */
         if (llist_add((struct llist_node *)&folio->mapping, &hpage_freelist))
                 schedule_work(&free_hpage_work);
 }
 
 static void bulk_vmemmap_restore_error(struct hstate *h,
                                         struct list_head *folio_list,
                                         struct list_head *non_hvo_folios)
 {
         struct folio *folio, *t_folio;
 
         if (!list_empty(non_hvo_folios)) {
                 /*
                  * Free any restored hugetlb pages so that restore of the
                  * entire list can be retried.
                  * The idea is that in the common case of ENOMEM errors freeing
                  * hugetlb pages with vmemmap we will free up memory so that we
                  * can allocate vmemmap for more hugetlb pages.
                  */
                 list_for_each_entry_safe(folio, t_folio, non_hvo_folios, lru) {
                         list_del(&folio->lru);
                         spin_lock_irq(&hugetlb_lock);
                         __folio_clear_hugetlb(folio);
                         spin_unlock_irq(&hugetlb_lock);
                         update_and_free_hugetlb_folio(h, folio, false);
                         cond_resched();
                 }
         } else {
                 /*
                  * In the case where there are no folios which can be
                  * immediately freed, we loop through the list trying to restore
                  * vmemmap individually in the hope that someone elsewhere may
                  * have done something to cause success (such as freeing some
                  * memory).  If unable to restore a hugetlb page, the hugetlb
                  * page is made a surplus page and removed from the list.
                  * If are able to restore vmemmap and free one hugetlb page, we
                  * quit processing the list to retry the bulk operation.
                  */
                 list_for_each_entry_safe(folio, t_folio, folio_list, lru)
                         if (hugetlb_vmemmap_restore_folio(h, folio)) {
                                 list_del(&folio->lru);
                                 spin_lock_irq(&hugetlb_lock);
                                 add_hugetlb_folio(h, folio, true);
                                 spin_unlock_irq(&hugetlb_lock);
                         } else {
                                 list_del(&folio->lru);
                                 spin_lock_irq(&hugetlb_lock);
                                 __folio_clear_hugetlb(folio);
                                 spin_unlock_irq(&hugetlb_lock);
                                 update_and_free_hugetlb_folio(h, folio, false);
                                 cond_resched();
                                 break;
                         }
         }
 }
 
 static void update_and_free_pages_bulk(struct hstate *h,
                                                 struct list_head *folio_list)
 {
         long ret;
         struct folio *folio, *t_folio;
         LIST_HEAD(non_hvo_folios);
 
         /*
          * First allocate required vmemmmap (if necessary) for all folios.
          * Carefully handle errors and free up any available hugetlb pages
          * in an effort to make forward progress.
          */
 retry:
         ret = hugetlb_vmemmap_restore_folios(h, folio_list, &non_hvo_folios);
         if (ret < 0) {
                 bulk_vmemmap_restore_error(h, folio_list, &non_hvo_folios);
                 goto retry;
         }
 
         /*
          * At this point, list should be empty, ret should be >= 0 and there
          * should only be pages on the non_hvo_folios list.
          * Do note that the non_hvo_folios list could be empty.
          * Without HVO enabled, ret will be 0 and there is no need to call
          * __folio_clear_hugetlb as this was done previously.
          */
         VM_WARN_ON(!list_empty(folio_list));
         VM_WARN_ON(ret < 0);
         if (!list_empty(&non_hvo_folios) && ret) {
                 spin_lock_irq(&hugetlb_lock);
                 list_for_each_entry(folio, &non_hvo_folios, lru)
                         __folio_clear_hugetlb(folio);
                 spin_unlock_irq(&hugetlb_lock);
         }
 
         list_for_each_entry_safe(folio, t_folio, &non_hvo_folios, lru) {
                 update_and_free_hugetlb_folio(h, folio, false);
                 cond_resched();
         }
 }
 
 struct hstate *size_to_hstate(unsigned long size)
 {
         struct hstate *h;
 
         for_each_hstate(h) {
                 if (huge_page_size(h) == size)
                         return h;
         }
         return NULL;
 }
 
 void free_huge_folio(struct folio *folio)
 {
         /*
          * Can't pass hstate in here because it is called from the
          * generic mm code.
          */
         struct hstate *h = folio_hstate(folio);
         int nid = folio_nid(folio);
         struct hugepage_subpool *spool = hugetlb_folio_subpool(folio);
         bool restore_reserve;
         unsigned long flags;
 
         VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);
         VM_BUG_ON_FOLIO(folio_mapcount(folio), folio);
 
         hugetlb_set_folio_subpool(folio, NULL);
         if (folio_test_anon(folio))
                 __ClearPageAnonExclusive(&folio->page);
         folio->mapping = NULL;
         restore_reserve = folio_test_hugetlb_restore_reserve(folio);
         folio_clear_hugetlb_restore_reserve(folio);
 
         /*
          * If HPageRestoreReserve was set on page, page allocation consumed a
          * reservation.  If the page was associated with a subpool, there
          * would have been a page reserved in the subpool before allocation
          * via hugepage_subpool_get_pages().  Since we are 'restoring' the
          * reservation, do not call hugepage_subpool_put_pages() as this will
          * remove the reserved page from the subpool.
          */
         if (!restore_reserve) {
                 /*
                  * A return code of zero implies that the subpool will be
                  * under its minimum size if the reservation is not restored
                  * after page is free.  Therefore, force restore_reserve
                  * operation.
                  */
                 if (hugepage_subpool_put_pages(spool, 1) == 0)
                         restore_reserve = true;
         }
 
         spin_lock_irqsave(&hugetlb_lock, flags);
         folio_clear_hugetlb_migratable(folio);
         hugetlb_cgroup_uncharge_folio(hstate_index(h),
                                      pages_per_huge_page(h), folio);
         hugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h),
                                           pages_per_huge_page(h), folio);
         mem_cgroup_uncharge(folio);
         if (restore_reserve)
                 h->resv_huge_pages++;
 
         if (folio_test_hugetlb_temporary(folio)) {
                 remove_hugetlb_folio(h, folio, false);
                 spin_unlock_irqrestore(&hugetlb_lock, flags);
                 update_and_free_hugetlb_folio(h, folio, true);
         } else if (h->surplus_huge_pages_node[nid]) {
                 /* remove the page from active list */
                 remove_hugetlb_folio(h, folio, true);
                 spin_unlock_irqrestore(&hugetlb_lock, flags);
                 update_and_free_hugetlb_folio(h, folio, true);
         } else {
                 arch_clear_hugetlb_flags(folio);
                 enqueue_hugetlb_folio(h, folio);
                 spin_unlock_irqrestore(&hugetlb_lock, flags);
         }
 }
 
 /*
  * Must be called with the hugetlb lock held
  */
 static void __prep_account_new_huge_page(struct hstate *h, int nid)
 {
         lockdep_assert_held(&hugetlb_lock);
         h->nr_huge_pages++;
         h->nr_huge_pages_node[nid]++;
 }
 
 static void init_new_hugetlb_folio(struct hstate *h, struct folio *folio)
 {
         __folio_set_hugetlb(folio);
         INIT_LIST_HEAD(&folio->lru);
         hugetlb_set_folio_subpool(folio, NULL);
         set_hugetlb_cgroup(folio, NULL);
         set_hugetlb_cgroup_rsvd(folio, NULL);
 }
 
 static void __prep_new_hugetlb_folio(struct hstate *h, struct folio *folio)
 {
         init_new_hugetlb_folio(h, folio);
         hugetlb_vmemmap_optimize_folio(h, folio);
 }
 
 static void prep_new_hugetlb_folio(struct hstate *h, struct folio *folio, int nid)
 {
         __prep_new_hugetlb_folio(h, folio);
         spin_lock_irq(&hugetlb_lock);
         __prep_account_new_huge_page(h, nid);
         spin_unlock_irq(&hugetlb_lock);
 }
 
 static bool __prep_compound_gigantic_folio(struct folio *folio,
                                         unsigned int order, bool demote)
 {
         int i, j;
         int nr_pages = 1 << order;
         struct page *p;
 
         __folio_clear_reserved(folio);
         for (i = 0; i < nr_pages; i++) {
                 p = folio_page(folio, i);
 
                 /*
                  * For gigantic hugepages allocated through bootmem at
                  * boot, it's safer to be consistent with the not-gigantic
                  * hugepages and clear the PG_reserved bit from all tail pages
                  * too.  Otherwise drivers using get_user_pages() to access tail
                  * pages may get the reference counting wrong if they see
                  * PG_reserved set on a tail page (despite the head page not
                  * having PG_reserved set).  Enforcing this consistency between
                  * head and tail pages allows drivers to optimize away a check
                  * on the head page when they need know if put_page() is needed
                  * after get_user_pages().
                  */
                 if (i != 0)     /* head page cleared above */
                         __ClearPageReserved(p);
                 /*
                  * Subtle and very unlikely
                  *
                  * Gigantic 'page allocators' such as memblock or cma will
                  * return a set of pages with each page ref counted.  We need
                  * to turn this set of pages into a compound page with tail
                  * page ref counts set to zero.  Code such as speculative page
                  * cache adding could take a ref on a 'to be' tail page.
                  * We need to respect any increased ref count, and only set
                  * the ref count to zero if count is currently 1.  If count
                  * is not 1, we return an error.  An error return indicates
                  * the set of pages can not be converted to a gigantic page.
                  * The caller who allocated the pages should then discard the
                  * pages using the appropriate free interface.
                  *
                  * In the case of demote, the ref count will be zero.
                  */
                 if (!demote) {
                         if (!page_ref_freeze(p, 1)) {
                                 pr_warn("HugeTLB page can not be used due to unexpected inflated ref count\n");
                                 goto out_error;
                         }
                 } else {
                         VM_BUG_ON_PAGE(page_count(p), p);
                 }
                 if (i != 0)
                         set_compound_head(p, &folio->page);
         }
         __folio_set_head(folio);
         /* we rely on prep_new_hugetlb_folio to set the hugetlb flag */
         folio_set_order(folio, order);
         atomic_set(&folio->_entire_mapcount, -1);
         atomic_set(&folio->_large_mapcount, -1);
         atomic_set(&folio->_pincount, 0);
         return true;
 
 out_error:
         /* undo page modifications made above */
         for (j = 0; j < i; j++) {
                 p = folio_page(folio, j);
                 if (j != 0)
                         clear_compound_head(p);
                 set_page_refcounted(p);
         }
         /* need to clear PG_reserved on remaining tail pages  */
         for (; j < nr_pages; j++) {
                 p = folio_page(folio, j);
                 __ClearPageReserved(p);
         }
         return false;
 }
 
 static bool prep_compound_gigantic_folio(struct folio *folio,
                                                         unsigned int order)
 {
         return __prep_compound_gigantic_folio(folio, order, false);
 }
 
 static bool prep_compound_gigantic_folio_for_demote(struct folio *folio,
                                                         unsigned int order)
 {
         return __prep_compound_gigantic_folio(folio, order, true);
 }
 
 /*
  * Find and lock address space (mapping) in write mode.
  *
  * Upon entry, the folio is locked which means that folio_mapping() is
  * stable.  Due to locking order, we can only trylock_write.  If we can
  * not get the lock, simply return NULL to caller.
  */
 struct address_space *hugetlb_folio_mapping_lock_write(struct folio *folio)
 {
         struct address_space *mapping = folio_mapping(folio);
 
         if (!mapping)
                 return mapping;
 
         if (i_mmap_trylock_write(mapping))
                 return mapping;
 
         return NULL;
 }
 
 static struct folio *alloc_buddy_hugetlb_folio(struct hstate *h,
                 gfp_t gfp_mask, int nid, nodemask_t *nmask,
                 nodemask_t *node_alloc_noretry)
 {
         int order = huge_page_order(h);
         struct folio *folio;
         bool alloc_try_hard = true;
         bool retry = true;
 
         /*
          * By default we always try hard to allocate the folio with
          * __GFP_RETRY_MAYFAIL flag.  However, if we are allocating folios in
          * a loop (to adjust global huge page counts) and previous allocation
          * failed, do not continue to try hard on the same node.  Use the
          * node_alloc_noretry bitmap to manage this state information.
          */
         if (node_alloc_noretry && node_isset(nid, *node_alloc_noretry))
                 alloc_try_hard = false;
         gfp_mask |= __GFP_COMP|__GFP_NOWARN;
         if (alloc_try_hard)
                 gfp_mask |= __GFP_RETRY_MAYFAIL;
         if (nid == NUMA_NO_NODE)
                 nid = numa_mem_id();
 retry:
         folio = __folio_alloc(gfp_mask, order, nid, nmask);
         /* Ensure hugetlb folio won't have large_rmappable flag set. */
         if (folio)
                 folio_clear_large_rmappable(folio);
 
         if (folio && !folio_ref_freeze(folio, 1)) {
                 folio_put(folio);
                 if (retry) {    /* retry once */
                         retry = false;
                         goto retry;
                 }
                 /* WOW!  twice in a row. */
                 pr_warn("HugeTLB unexpected inflated folio ref count\n");
                 folio = NULL;
         }
 
         /*
          * If we did not specify __GFP_RETRY_MAYFAIL, but still got a
          * folio this indicates an overall state change.  Clear bit so
          * that we resume normal 'try hard' allocations.
          */
         if (node_alloc_noretry && folio && !alloc_try_hard)
                 node_clear(nid, *node_alloc_noretry);
 
         /*
          * If we tried hard to get a folio but failed, set bit so that
          * subsequent attempts will not try as hard until there is an
          * overall state change.
          */
         if (node_alloc_noretry && !folio && alloc_try_hard)
                 node_set(nid, *node_alloc_noretry);
 
         if (!folio) {
                 __count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
                 return NULL;
         }
 
         __count_vm_event(HTLB_BUDDY_PGALLOC);
         return folio;
 }
 
 static struct folio *__alloc_fresh_hugetlb_folio(struct hstate *h,
                                 gfp_t gfp_mask, int nid, nodemask_t *nmask,
                                 nodemask_t *node_alloc_noretry)
 {
         struct folio *folio;
         bool retry = false;
 
 retry:
         if (hstate_is_gigantic(h))
                 folio = alloc_gigantic_folio(h, gfp_mask, nid, nmask);
         else
                 folio = alloc_buddy_hugetlb_folio(h, gfp_mask,
                                 nid, nmask, node_alloc_noretry);
         if (!folio)
                 return NULL;
 
         if (hstate_is_gigantic(h)) {
                 if (!prep_compound_gigantic_folio(folio, huge_page_order(h))) {
                         /*
                          * Rare failure to convert pages to compound page.
                          * Free pages and try again - ONCE!
                          */
                         free_gigantic_folio(folio, huge_page_order(h));
                         if (!retry) {
                                 retry = true;
                                 goto retry;
                         }
                         return NULL;
                 }
         }
 
         return folio;
 }
 
 static struct folio *only_alloc_fresh_hugetlb_folio(struct hstate *h,
                 gfp_t gfp_mask, int nid, nodemask_t *nmask,
                 nodemask_t *node_alloc_noretry)
 {
         struct folio *folio;
 
         folio = __alloc_fresh_hugetlb_folio(h, gfp_mask, nid, nmask,
                                                 node_alloc_noretry);
         if (folio)
                 init_new_hugetlb_folio(h, folio);
         return folio;
 }
 
 /*
  * Common helper to allocate a fresh hugetlb page. All specific allocators
  * should use this function to get new hugetlb pages
  *
  * Note that returned page is 'frozen':  ref count of head page and all tail
  * pages is zero.
  */
 static struct folio *alloc_fresh_hugetlb_folio(struct hstate *h,
                 gfp_t gfp_mask, int nid, nodemask_t *nmask)
 {
         struct folio *folio;
 
         folio = __alloc_fresh_hugetlb_folio(h, gfp_mask, nid, nmask, NULL);
         if (!folio)
                 return NULL;
 
         prep_new_hugetlb_folio(h, folio, folio_nid(folio));
         return folio;
 }
 
 static void prep_and_add_allocated_folios(struct hstate *h,
                                         struct list_head *folio_list)
 {
         unsigned long flags;
         struct folio *folio, *tmp_f;
 
         /* Send list for bulk vmemmap optimization processing */
         hugetlb_vmemmap_optimize_folios(h, folio_list);
 
         /* Add all new pool pages to free lists in one lock cycle */
         spin_lock_irqsave(&hugetlb_lock, flags);
         list_for_each_entry_safe(folio, tmp_f, folio_list, lru) {
                 __prep_account_new_huge_page(h, folio_nid(folio));
                 enqueue_hugetlb_folio(h, folio);
         }
         spin_unlock_irqrestore(&hugetlb_lock, flags);
 }
 
 /*
  * Allocates a fresh hugetlb page in a node interleaved manner.  The page
  * will later be added to the appropriate hugetlb pool.
  */
 static struct folio *alloc_pool_huge_folio(struct hstate *h,
                                         nodemask_t *nodes_allowed,
                                         nodemask_t *node_alloc_noretry,
                                         int *next_node)
 {
         gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
         int nr_nodes, node;
 
         for_each_node_mask_to_alloc(next_node, nr_nodes, node, nodes_allowed) {
                 struct folio *folio;
 
                 folio = only_alloc_fresh_hugetlb_folio(h, gfp_mask, node,
                                         nodes_allowed, node_alloc_noretry);
                 if (folio)
                         return folio;
         }
 
         return NULL;
 }
 
 /*
  * Remove huge page from pool from next node to free.  Attempt to keep
  * persistent huge pages more or less balanced over allowed nodes.
  * This routine only 'removes' the hugetlb page.  The caller must make
  * an additional call to free the page to low level allocators.
  * Called with hugetlb_lock locked.
  */
 static struct folio *remove_pool_hugetlb_folio(struct hstate *h,
                 nodemask_t *nodes_allowed, bool acct_surplus)
 {
         int nr_nodes, node;
         struct folio *folio = NULL;
 
         lockdep_assert_held(&hugetlb_lock);
         for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
                 /*
                  * If we're returning unused surplus pages, only examine
                  * nodes with surplus pages.
                  */
                 if ((!acct_surplus || h->surplus_huge_pages_node[node]) &&
                     !list_empty(&h->hugepage_freelists[node])) {
                         folio = list_entry(h->hugepage_freelists[node].next,
                                           struct folio, lru);
                         remove_hugetlb_folio(h, folio, acct_surplus);
                         break;
                 }
         }
 
         return folio;
 }
 
 /*
  * Dissolve a given free hugetlb folio into free buddy pages. This function
  * does nothing for in-use hugetlb folios and non-hugetlb folios.
  * This function returns values like below:
  *
  *  -ENOMEM: failed to allocate vmemmap pages to free the freed hugepages
  *           when the system is under memory pressure and the feature of
  *           freeing unused vmemmap pages associated with each hugetlb page
  *           is enabled.
  *  -EBUSY:  failed to dissolved free hugepages or the hugepage is in-use
  *           (allocated or reserved.)
  *       0:  successfully dissolved free hugepages or the page is not a
  *           hugepage (considered as already dissolved)
  */
 int dissolve_free_hugetlb_folio(struct folio *folio)
 {
         int rc = -EBUSY;
 
 retry:
         /* Not to disrupt normal path by vainly holding hugetlb_lock */
         if (!folio_test_hugetlb(folio))
                 return 0;
 
         spin_lock_irq(&hugetlb_lock);
         if (!folio_test_hugetlb(folio)) {
                 rc = 0;
                 goto out;
         }
 
         if (!folio_ref_count(folio)) {
                 struct hstate *h = folio_hstate(folio);
                 if (!available_huge_pages(h))
                         goto out;
 
                 /*
                  * We should make sure that the page is already on the free list
                  * when it is dissolved.
                  */
                 if (unlikely(!folio_test_hugetlb_freed(folio))) {
                         spin_unlock_irq(&hugetlb_lock);
                         cond_resched();
 
                         /*
                          * Theoretically, we should return -EBUSY when we
                          * encounter this race. In fact, we have a chance
                          * to successfully dissolve the page if we do a
                          * retry. Because the race window is quite small.
                          * If we seize this opportunity, it is an optimization
                          * for increasing the success rate of dissolving page.
                          */
                         goto retry;
                 }
 
                 remove_hugetlb_folio(h, folio, false);
                 h->max_huge_pages--;
                 spin_unlock_irq(&hugetlb_lock);
 
                 /*
                  * Normally update_and_free_hugtlb_folio will allocate required vmemmmap
                  * before freeing the page.  update_and_free_hugtlb_folio will fail to
                  * free the page if it can not allocate required vmemmap.  We
                  * need to adjust max_huge_pages if the page is not freed.
                  * Attempt to allocate vmemmmap here so that we can take
                  * appropriate action on failure.
                  *
                  * The folio_test_hugetlb check here is because
                  * remove_hugetlb_folio will clear hugetlb folio flag for
                  * non-vmemmap optimized hugetlb folios.
                  */
                 if (folio_test_hugetlb(folio)) {
                         rc = hugetlb_vmemmap_restore_folio(h, folio);
                         if (rc) {
                                 spin_lock_irq(&hugetlb_lock);
                                 add_hugetlb_folio(h, folio, false);
                                 h->max_huge_pages++;
                                 goto out;
                         }
                 } else
                         rc = 0;
 
                 update_and_free_hugetlb_folio(h, folio, false);
                 return rc;
         }
 out:
         spin_unlock_irq(&hugetlb_lock);
         return rc;
 }
 
 /*
  * Dissolve free hugepages in a given pfn range. Used by memory hotplug to
  * make specified memory blocks removable from the system.
  * Note that this will dissolve a free gigantic hugepage completely, if any
  * part of it lies within the given range.
  * Also note that if dissolve_free_hugetlb_folio() returns with an error, all
  * free hugetlb folios that were dissolved before that error are lost.
  */
 int dissolve_free_hugetlb_folios(unsigned long start_pfn, unsigned long end_pfn)
 {
         unsigned long pfn;
         struct folio *folio;
         int rc = 0;
         unsigned int order;
         struct hstate *h;
 
         if (!hugepages_supported())
                 return rc;
 
         order = huge_page_order(&default_hstate);
         for_each_hstate(h)
                 order = min(order, huge_page_order(h));
 
         for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << order) {
                 folio = pfn_folio(pfn);
                 rc = dissolve_free_hugetlb_folio(folio);
                 if (rc)
                         break;
         }
 
         return rc;
 }
 
 /*
  * Allocates a fresh surplus page from the page allocator.
  */
 static struct folio *alloc_surplus_hugetlb_folio(struct hstate *h,
                                 gfp_t gfp_mask, int nid, nodemask_t *nmask)
 {
         struct folio *folio = NULL;
 
         if (hstate_is_gigantic(h))
                 return NULL;
 
         spin_lock_irq(&hugetlb_lock);
         if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages)
                 goto out_unlock;
         spin_unlock_irq(&hugetlb_lock);
 
         folio = alloc_fresh_hugetlb_folio(h, gfp_mask, nid, nmask);
         if (!folio)
                 return NULL;
 
         spin_lock_irq(&hugetlb_lock);
         /*
          * We could have raced with the pool size change.
          * Double check that and simply deallocate the new page
          * if we would end up overcommiting the surpluses. Abuse
          * temporary page to workaround the nasty free_huge_folio
          * codeflow
          */
         if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
                 folio_set_hugetlb_temporary(folio);
                 spin_unlock_irq(&hugetlb_lock);
                 free_huge_folio(folio);
                 return NULL;
         }
 
         h->surplus_huge_pages++;
         h->surplus_huge_pages_node[folio_nid(folio)]++;
 
 out_unlock:
         spin_unlock_irq(&hugetlb_lock);
 
         return folio;
 }
 
 static struct folio *alloc_migrate_hugetlb_folio(struct hstate *h, gfp_t gfp_mask,
                                      int nid, nodemask_t *nmask)
 {
         struct folio *folio;
 
         if (hstate_is_gigantic(h))
                 return NULL;
 
         folio = alloc_fresh_hugetlb_folio(h, gfp_mask, nid, nmask);
         if (!folio)
                 return NULL;
 
         /* fresh huge pages are frozen */
         folio_ref_unfreeze(folio, 1);
         /*
          * We do not account these pages as surplus because they are only
          * temporary and will be released properly on the last reference
          */
         folio_set_hugetlb_temporary(folio);
 
         return folio;
 }
 
 /*
  * Use the VMA's mpolicy to allocate a huge page from the buddy.
  */
 static
 struct folio *alloc_buddy_hugetlb_folio_with_mpol(struct hstate *h,
                 struct vm_area_struct *vma, unsigned long addr)
 {
         struct folio *folio = NULL;
         struct mempolicy *mpol;
         gfp_t gfp_mask = htlb_alloc_mask(h);
         int nid;
         nodemask_t *nodemask;
 
         nid = huge_node(vma, addr, gfp_mask, &mpol, &nodemask);
         if (mpol_is_preferred_many(mpol)) {
                 gfp_t gfp = gfp_mask | __GFP_NOWARN;
 
                 gfp &=  ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL);
                 folio = alloc_surplus_hugetlb_folio(h, gfp, nid, nodemask);
 
                 /* Fallback to all nodes if page==NULL */
                 nodemask = NULL;
         }
 
         if (!folio)
                 folio = alloc_surplus_hugetlb_folio(h, gfp_mask, nid, nodemask);
         mpol_cond_put(mpol);
         return folio;
 }
 
 struct folio *alloc_hugetlb_folio_reserve(struct hstate *h, int preferred_nid,
                 nodemask_t *nmask, gfp_t gfp_mask)
 {
         struct folio *folio;
 
         spin_lock_irq(&hugetlb_lock);
         folio = dequeue_hugetlb_folio_nodemask(h, gfp_mask, preferred_nid,
                                                nmask);
         if (folio) {
                 VM_BUG_ON(!h->resv_huge_pages);
                 h->resv_huge_pages--;
         }
 
         spin_unlock_irq(&hugetlb_lock);
         return folio;
 }
 
 /* folio migration callback function */
 struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid,
                 nodemask_t *nmask, gfp_t gfp_mask, bool allow_alloc_fallback)
 {
         spin_lock_irq(&hugetlb_lock);
         if (available_huge_pages(h)) {
                 struct folio *folio;
 
                 folio = dequeue_hugetlb_folio_nodemask(h, gfp_mask,
                                                 preferred_nid, nmask);
                 if (folio) {
                         spin_unlock_irq(&hugetlb_lock);
                         return folio;
                 }
         }
         spin_unlock_irq(&hugetlb_lock);
 
         /* We cannot fallback to other nodes, as we could break the per-node pool. */
         if (!allow_alloc_fallback)
                 gfp_mask |= __GFP_THISNODE;
 
         return alloc_migrate_hugetlb_folio(h, gfp_mask, preferred_nid, nmask);
 }
 
 static nodemask_t *policy_mbind_nodemask(gfp_t gfp)
 {
 #ifdef CONFIG_NUMA
         struct mempolicy *mpol = get_task_policy(current);
 
         /*
          * Only enforce MPOL_BIND policy which overlaps with cpuset policy
          * (from policy_nodemask) specifically for hugetlb case
          */
         if (mpol->mode == MPOL_BIND &&
                 (apply_policy_zone(mpol, gfp_zone(gfp)) &&
                  cpuset_nodemask_valid_mems_allowed(&mpol->nodes)))
                 return &mpol->nodes;
 #endif
         return NULL;
 }
 
 /*
  * Increase the hugetlb pool such that it can accommodate a reservation
  * of size 'delta'.
  */
 static int gather_surplus_pages(struct hstate *h, long delta)
         __must_hold(&hugetlb_lock)
 {
         LIST_HEAD(surplus_list);
         struct folio *folio, *tmp;
         int ret;
         long i;
         long needed, allocated;
         bool alloc_ok = true;
         int node;
         nodemask_t *mbind_nodemask = policy_mbind_nodemask(htlb_alloc_mask(h));
 
         lockdep_assert_held(&hugetlb_lock);
         needed = (h->resv_huge_pages + delta) - h->free_huge_pages;
         if (needed <= 0) {
                 h->resv_huge_pages += delta;
                 return 0;
         }
 
         allocated = 0;
 
         ret = -ENOMEM;
 retry:
         spin_unlock_irq(&hugetlb_lock);
         for (i = 0; i < needed; i++) {
                 folio = NULL;
                 for_each_node_mask(node, cpuset_current_mems_allowed) {
                         if (!mbind_nodemask || node_isset(node, *mbind_nodemask)) {
                                 folio = alloc_surplus_hugetlb_folio(h, htlb_alloc_mask(h),
                                                 node, NULL);
                                 if (folio)
                                         break;
                         }
                 }
                 if (!folio) {
                         alloc_ok = false;
                         break;
                 }
                 list_add(&folio->lru, &surplus_list);
                 cond_resched();
         }
         allocated += i;
 
         /*
          * After retaking hugetlb_lock, we need to recalculate 'needed'
          * because either resv_huge_pages or free_huge_pages may have changed.
          */
         spin_lock_irq(&hugetlb_lock);
         needed = (h->resv_huge_pages + delta) -
                         (h->free_huge_pages + allocated);
         if (needed > 0) {
                 if (alloc_ok)
                         goto retry;
                 /*
                  * We were not able to allocate enough pages to
                  * satisfy the entire reservation so we free what
                  * we've allocated so far.
                  */
                 goto free;
         }
         /*
          * The surplus_list now contains _at_least_ the number of extra pages
          * needed to accommodate the reservation.  Add the appropriate number
          * of pages to the hugetlb pool and free the extras back to the buddy
          * allocator.  Commit the entire reservation here to prevent another
          * process from stealing the pages as they are added to the pool but
          * before they are reserved.
          */
         needed += allocated;
         h->resv_huge_pages += delta;
         ret = 0;
 
         /* Free the needed pages to the hugetlb pool */
         list_for_each_entry_safe(folio, tmp, &surplus_list, lru) {
                 if ((--needed) < 0)
                         break;
                 /* Add the page to the hugetlb allocator */
                 enqueue_hugetlb_folio(h, folio);
         }
 free:
         spin_unlock_irq(&hugetlb_lock);
 
         /*
          * Free unnecessary surplus pages to the buddy allocator.
          * Pages have no ref count, call free_huge_folio directly.
          */
         list_for_each_entry_safe(folio, tmp, &surplus_list, lru)
                 free_huge_folio(folio);
         spin_lock_irq(&hugetlb_lock);
 
         return ret;
 }
 
 /*
  * This routine has two main purposes:
  * 1) Decrement the reservation count (resv_huge_pages) by the value passed
  *    in unused_resv_pages.  This corresponds to the prior adjustments made
  *    to the associated reservation map.
  * 2) Free any unused surplus pages that may have been allocated to satisfy
  *    the reservation.  As many as unused_resv_pages may be freed.
  */
 static void return_unused_surplus_pages(struct hstate *h,
                                         unsigned long unused_resv_pages)
 {
         unsigned long nr_pages;
         LIST_HEAD(page_list);
 
         lockdep_assert_held(&hugetlb_lock);
         /* Uncommit the reservation */
         h->resv_huge_pages -= unused_resv_pages;
 
         if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                 goto out;
 
         /*
          * Part (or even all) of the reservation could have been backed
          * by pre-allocated pages. Only free surplus pages.
          */
         nr_pages = min(unused_resv_pages, h->surplus_huge_pages);
 
         /*
          * We want to release as many surplus pages as possible, spread
          * evenly across all nodes with memory. Iterate across these nodes
          * until we can no longer free unreserved surplus pages. This occurs
          * when the nodes with surplus pages have no free pages.
          * remove_pool_hugetlb_folio() will balance the freed pages across the
          * on-line nodes with memory and will handle the hstate accounting.
          */
         while (nr_pages--) {
                 struct folio *folio;
 
                 folio = remove_pool_hugetlb_folio(h, &node_states[N_MEMORY], 1);
                 if (!folio)
                         goto out;
 
                 list_add(&folio->lru, &page_list);
         }
 
 out:
         spin_unlock_irq(&hugetlb_lock);
         update_and_free_pages_bulk(h, &page_list);
         spin_lock_irq(&hugetlb_lock);
 }
 
 
 /*
  * vma_needs_reservation, vma_commit_reservation and vma_end_reservation
  * are used by the huge page allocation routines to manage reservations.
  *
  * vma_needs_reservation is called to determine if the huge page at addr
  * within the vma has an associated reservation.  If a reservation is
  * needed, the value 1 is returned.  The caller is then responsible for
  * managing the global reservation and subpool usage counts.  After
  * the huge page has been allocated, vma_commit_reservation is called
  * to add the page to the reservation map.  If the page allocation fails,
  * the reservation must be ended instead of committed.  vma_end_reservation
  * is called in such cases.
  *
  * In the normal case, vma_commit_reservation returns the same value
  * as the preceding vma_needs_reservation call.  The only time this
  * is not the case is if a reserve map was changed between calls.  It
  * is the responsibility of the caller to notice the difference and
  * take appropriate action.
  *
  * vma_add_reservation is used in error paths where a reservation must
  * be restored when a newly allocated huge page must be freed.  It is
  * to be called after calling vma_needs_reservation to determine if a
  * reservation exists.
  *
  * vma_del_reservation is used in error paths where an entry in the reserve
  * map was created during huge page allocation and must be removed.  It is to
  * be called after calling vma_needs_reservation to determine if a reservation
  * exists.
  */
 enum vma_resv_mode {
         VMA_NEEDS_RESV,
         VMA_COMMIT_RESV,
         VMA_END_RESV,
         VMA_ADD_RESV,
         VMA_DEL_RESV,
 };
 static long __vma_reservation_common(struct hstate *h,
                                 struct vm_area_struct *vma, unsigned long addr,
                                 enum vma_resv_mode mode)
 {
         struct resv_map *resv;
         pgoff_t idx;
         long ret;
         long dummy_out_regions_needed;
 
         resv = vma_resv_map(vma);
         if (!resv)
                 return 1;
 
         idx = vma_hugecache_offset(h, vma, addr);
         switch (mode) {
         case VMA_NEEDS_RESV:
                 ret = region_chg(resv, idx, idx + 1, &dummy_out_regions_needed);
                 /* We assume that vma_reservation_* routines always operate on
                  * 1 page, and that adding to resv map a 1 page entry can only
                  * ever require 1 region.
                  */
                 VM_BUG_ON(dummy_out_regions_needed != 1);
                 break;
         case VMA_COMMIT_RESV:
                 ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
                 /* region_add calls of range 1 should never fail. */
                 VM_BUG_ON(ret < 0);
                 break;
         case VMA_END_RESV:
                 region_abort(resv, idx, idx + 1, 1);
                 ret = 0;
                 break;
         case VMA_ADD_RESV:
                 if (vma->vm_flags & VM_MAYSHARE) {
                         ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
                         /* region_add calls of range 1 should never fail. */
                         VM_BUG_ON(ret < 0);
                 } else {
                         region_abort(resv, idx, idx + 1, 1);
                         ret = region_del(resv, idx, idx + 1);
                 }
                 break;
         case VMA_DEL_RESV:
                 if (vma->vm_flags & VM_MAYSHARE) {
                         region_abort(resv, idx, idx + 1, 1);
                         ret = region_del(resv, idx, idx + 1);
                 } else {
                         ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
                         /* region_add calls of range 1 should never fail. */
                         VM_BUG_ON(ret < 0);
                 }
                 break;
         default:
                 BUG();
         }
 
         if (vma->vm_flags & VM_MAYSHARE || mode == VMA_DEL_RESV)
                 return ret;
         /*
          * We know private mapping must have HPAGE_RESV_OWNER set.
          *
          * In most cases, reserves always exist for private mappings.
          * However, a file associated with mapping could have been
          * hole punched or truncated after reserves were consumed.
          * As subsequent fault on such a range will not use reserves.
          * Subtle - The reserve map for private mappings has the
          * opposite meaning than that of shared mappings.  If NO
          * entry is in the reserve map, it means a reservation exists.
          * If an entry exists in the reserve map, it means the
          * reservation has already been consumed.  As a result, the
          * return value of this routine is the opposite of the
          * value returned from reserve map manipulation routines above.
          */
         if (ret > 0)
                 return 0;
         if (ret == 0)
                 return 1;
         return ret;
 }
 
 static long vma_needs_reservation(struct hstate *h,
                         struct vm_area_struct *vma, unsigned long addr)
 {
         return __vma_reservation_common(h, vma, addr, VMA_NEEDS_RESV);
 }
 
 static long vma_commit_reservation(struct hstate *h,
                         struct vm_area_struct *vma, unsigned long addr)
 {
         return __vma_reservation_common(h, vma, addr, VMA_COMMIT_RESV);
 }
 
 static void vma_end_reservation(struct hstate *h,
                         struct vm_area_struct *vma, unsigned long addr)
 {
         (void)__vma_reservation_common(h, vma, addr, VMA_END_RESV);
 }
 
 static long vma_add_reservation(struct hstate *h,
                         struct vm_area_struct *vma, unsigned long addr)
 {
         return __vma_reservation_common(h, vma, addr, VMA_ADD_RESV);
 }
 
 static long vma_del_reservation(struct hstate *h,
                         struct vm_area_struct *vma, unsigned long addr)
 {
         return __vma_reservation_common(h, vma, addr, VMA_DEL_RESV);
 }
 
 /*
  * This routine is called to restore reservation information on error paths.
  * It should ONLY be called for folios allocated via alloc_hugetlb_folio(),
  * and the hugetlb mutex should remain held when calling this routine.
  *
  * It handles two specific cases:
  * 1) A reservation was in place and the folio consumed the reservation.
  *    hugetlb_restore_reserve is set in the folio.
  * 2) No reservation was in place for the page, so hugetlb_restore_reserve is
  *    not set.  However, alloc_hugetlb_folio always updates the reserve map.
  *
  * In case 1, free_huge_folio later in the error path will increment the
  * global reserve count.  But, free_huge_folio does not have enough context
  * to adjust the reservation map.  This case deals primarily with private
  * mappings.  Adjust the reserve map here to be consistent with global
  * reserve count adjustments to be made by free_huge_folio.  Make sure the
  * reserve map indicates there is a reservation present.
  *
  * In case 2, simply undo reserve map modifications done by alloc_hugetlb_folio.
  */
 void restore_reserve_on_error(struct hstate *h, struct vm_area_struct *vma,
                         unsigned long address, struct folio *folio)
 {
         long rc = vma_needs_reservation(h, vma, address);
 
         if (folio_test_hugetlb_restore_reserve(folio)) {
                 if (unlikely(rc < 0))
                         /*
                          * Rare out of memory condition in reserve map
                          * manipulation.  Clear hugetlb_restore_reserve so
                          * that global reserve count will not be incremented
                          * by free_huge_folio.  This will make it appear
                          * as though the reservation for this folio was
                          * consumed.  This may prevent the task from
                          * faulting in the folio at a later time.  This
                          * is better than inconsistent global huge page
                          * accounting of reserve counts.
                          */
                         folio_clear_hugetlb_restore_reserve(folio);
                 else if (rc)
                         (void)vma_add_reservation(h, vma, address);
                 else
                         vma_end_reservation(h, vma, address);
         } else {
                 if (!rc) {
                         /*
                          * This indicates there is an entry in the reserve map
                          * not added by alloc_hugetlb_folio.  We know it was added
                          * before the alloc_hugetlb_folio call, otherwise
                          * hugetlb_restore_reserve would be set on the folio.
                          * Remove the entry so that a subsequent allocation
                          * does not consume a reservation.
                          */
                         rc = vma_del_reservation(h, vma, address);
                         if (rc < 0)
                                 /*
                                  * VERY rare out of memory condition.  Since
                                  * we can not delete the entry, set
                                  * hugetlb_restore_reserve so that the reserve
                                  * count will be incremented when the folio
                                  * is freed.  This reserve will be consumed
                                  * on a subsequent allocation.
                                  */
                                 folio_set_hugetlb_restore_reserve(folio);
                 } else if (rc < 0) {
                         /*
                          * Rare out of memory condition from
                          * vma_needs_reservation call.  Memory allocation is
                          * only attempted if a new entry is needed.  Therefore,
                          * this implies there is not an entry in the
                          * reserve map.
                          *
                          * For shared mappings, no entry in the map indicates
                          * no reservation.  We are done.
                          */
                         if (!(vma->vm_flags & VM_MAYSHARE))
                                 /*
                                  * For private mappings, no entry indicates
                                  * a reservation is present.  Since we can
                                  * not add an entry, set hugetlb_restore_reserve
                                  * on the folio so reserve count will be
                                  * incremented when freed.  This reserve will
                                  * be consumed on a subsequent allocation.
                                  */
                                 folio_set_hugetlb_restore_reserve(folio);
                 } else
                         /*
                          * No reservation present, do nothing
                          */
                          vma_end_reservation(h, vma, address);
         }
 }
 
 /*
  * alloc_and_dissolve_hugetlb_folio - Allocate a new folio and dissolve
  * the old one
  * @h: struct hstate old page belongs to
  * @old_folio: Old folio to dissolve
  * @list: List to isolate the page in case we need to
  * Returns 0 on success, otherwise negated error.
  */
 static int alloc_and_dissolve_hugetlb_folio(struct hstate *h,
                         struct folio *old_folio, struct list_head *list)
 {
         gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
         int nid = folio_nid(old_folio);
         struct folio *new_folio = NULL;
         int ret = 0;
 
 retry:
         spin_lock_irq(&hugetlb_lock);
         if (!folio_test_hugetlb(old_folio)) {
                 /*
                  * Freed from under us. Drop new_folio too.
                  */
                 goto free_new;
         } else if (folio_ref_count(old_folio)) {
                 bool isolated;
 
                 /*
                  * Someone has grabbed the folio, try to isolate it here.
                  * Fail with -EBUSY if not possible.
                  */
                 spin_unlock_irq(&hugetlb_lock);
                 isolated = isolate_hugetlb(old_folio, list);
                 ret = isolated ? 0 : -EBUSY;
                 spin_lock_irq(&hugetlb_lock);
                 goto free_new;
         } else if (!folio_test_hugetlb_freed(old_folio)) {
                 /*
                  * Folio's refcount is 0 but it has not been enqueued in the
                  * freelist yet. Race window is small, so we can succeed here if
                  * we retry.
                  */
                 spin_unlock_irq(&hugetlb_lock);
                 cond_resched();
                 goto retry;
         } else {
                 if (!new_folio) {
                         spin_unlock_irq(&hugetlb_lock);
                         new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid,
                                                               NULL, NULL);
                         if (!new_folio)
                                 return -ENOMEM;
                         __prep_new_hugetlb_folio(h, new_folio);
                         goto retry;
                 }
 
                 /*
                  * Ok, old_folio is still a genuine free hugepage. Remove it from
                  * the freelist and decrease the counters. These will be
                  * incremented again when calling __prep_account_new_huge_page()
                  * and enqueue_hugetlb_folio() for new_folio. The counters will
                  * remain stable since this happens under the lock.
                  */
                 remove_hugetlb_folio(h, old_folio, false);
 
                 /*
                  * Ref count on new_folio is already zero as it was dropped
                  * earlier.  It can be directly added to the pool free list.
                  */
                 __prep_account_new_huge_page(h, nid);
                 enqueue_hugetlb_folio(h, new_folio);
 
                 /*
                  * Folio has been replaced, we can safely free the old one.
                  */
                 spin_unlock_irq(&hugetlb_lock);
                 update_and_free_hugetlb_folio(h, old_folio, false);
         }
 
         return ret;
 
 free_new:
         spin_unlock_irq(&hugetlb_lock);
         if (new_folio)
                 update_and_free_hugetlb_folio(h, new_folio, false);
 
         return ret;
 }
 
 int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
 {
         struct hstate *h;
         struct folio *folio = page_folio(page);
         int ret = -EBUSY;
 
         /*
          * The page might have been dissolved from under our feet, so make sure
          * to carefully check the state under the lock.
          * Return success when racing as if we dissolved the page ourselves.
          */
         spin_lock_irq(&hugetlb_lock);
         if (folio_test_hugetlb(folio)) {
                 h = folio_hstate(folio);
         } else {
                 spin_unlock_irq(&hugetlb_lock);
                 return 0;
         }
         spin_unlock_irq(&hugetlb_lock);
 
         /*
          * Fence off gigantic pages as there is a cyclic dependency between
          * alloc_contig_range and them. Return -ENOMEM as this has the effect
          * of bailing out right away without further retrying.
          */
         if (hstate_is_gigantic(h))
                 return -ENOMEM;
 
         if (folio_ref_count(folio) && isolate_hugetlb(folio, list))
                 ret = 0;
         else if (!folio_ref_count(folio))
                 ret = alloc_and_dissolve_hugetlb_folio(h, folio, list);
 
         return ret;
 }
 
 struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
                                     unsigned long addr, int avoid_reserve)
 {
         struct hugepage_subpool *spool = subpool_vma(vma);
         struct hstate *h = hstate_vma(vma);
         struct folio *folio;
         long map_chg, map_commit, nr_pages = pages_per_huge_page(h);
         long gbl_chg;
         int memcg_charge_ret, ret, idx;
         struct hugetlb_cgroup *h_cg = NULL;
         struct mem_cgroup *memcg;
         bool deferred_reserve;
         gfp_t gfp = htlb_alloc_mask(h) | __GFP_RETRY_MAYFAIL;
 
         memcg = get_mem_cgroup_from_current();
         memcg_charge_ret = mem_cgroup_hugetlb_try_charge(memcg, gfp, nr_pages);
         if (memcg_charge_ret == -ENOMEM) {
                 mem_cgroup_put(memcg);
                 return ERR_PTR(-ENOMEM);
         }
 
         idx = hstate_index(h);
         /*
          * Examine the region/reserve map to determine if the process
          * has a reservation for the page to be allocated.  A return
          * code of zero indicates a reservation exists (no change).
          */
         map_chg = gbl_chg = vma_needs_reservation(h, vma, addr);
         if (map_chg < 0) {
                 if (!memcg_charge_ret)
                         mem_cgroup_cancel_charge(memcg, nr_pages);
                 mem_cgroup_put(memcg);
                 return ERR_PTR(-ENOMEM);
         }
 
         /*
          * Processes that did not create the mapping will have no
          * reserves as indicated by the region/reserve map. Check
          * that the allocation will not exceed the subpool limit.
          * Allocations for MAP_NORESERVE mappings also need to be
          * checked against any subpool limit.
          */
         if (map_chg || avoid_reserve) {
                 gbl_chg = hugepage_subpool_get_pages(spool, 1);
                 if (gbl_chg < 0)
                         goto out_end_reservation;
 
                 /*
                  * Even though there was no reservation in the region/reserve
                  * map, there could be reservations associated with the
                  * subpool that can be used.  This would be indicated if the
                  * return value of hugepage_subpool_get_pages() is zero.
                  * However, if avoid_reserve is specified we still avoid even
                  * the subpool reservations.
                  */
                 if (avoid_reserve)
                         gbl_chg = 1;
         }
 
         /* If this allocation is not consuming a reservation, charge it now.
          */
         deferred_reserve = map_chg || avoid_reserve;
         if (deferred_reserve) {
                 ret = hugetlb_cgroup_charge_cgroup_rsvd(
                         idx, pages_per_huge_page(h), &h_cg);
                 if (ret)
                         goto out_subpool_put;
         }
 
         ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
         if (ret)
                 goto out_uncharge_cgroup_reservation;
 
         spin_lock_irq(&hugetlb_lock);
         /*
          * glb_chg is passed to indicate whether or not a page must be taken
          * from the global free pool (global change).  gbl_chg == 0 indicates
          * a reservation exists for the allocation.
          */
         folio = dequeue_hugetlb_folio_vma(h, vma, addr, avoid_reserve, gbl_chg);
         if (!folio) {
                 spin_unlock_irq(&hugetlb_lock);
                 folio = alloc_buddy_hugetlb_folio_with_mpol(h, vma, addr);
                 if (!folio)
                         goto out_uncharge_cgroup;
                 spin_lock_irq(&hugetlb_lock);
                 if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) {
                         folio_set_hugetlb_restore_reserve(folio);
                         h->resv_huge_pages--;
                 }
                 list_add(&folio->lru, &h->hugepage_activelist);
                 folio_ref_unfreeze(folio, 1);
                 /* Fall through */
         }
 
         hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, folio);
         /* If allocation is not consuming a reservation, also store the
          * hugetlb_cgroup pointer on the page.
          */
         if (deferred_reserve) {
                 hugetlb_cgroup_commit_charge_rsvd(idx, pages_per_huge_page(h),
                                                   h_cg, folio);
         }
 
         spin_unlock_irq(&hugetlb_lock);
 
         hugetlb_set_folio_subpool(folio, spool);
 
         map_commit = vma_commit_reservation(h, vma, addr);
         if (unlikely(map_chg > map_commit)) {
                 /*
                  * The page was added to the reservation map between
                  * vma_needs_reservation and vma_commit_reservation.
                  * This indicates a race with hugetlb_reserve_pages.
                  * Adjust for the subpool count incremented above AND
                  * in hugetlb_reserve_pages for the same page.  Also,
                  * the reservation count added in hugetlb_reserve_pages
                  * no longer applies.
                  */
                 long rsv_adjust;
 
                 rsv_adjust = hugepage_subpool_put_pages(spool, 1);
                 hugetlb_acct_memory(h, -rsv_adjust);
                 if (deferred_reserve) {
                         spin_lock_irq(&hugetlb_lock);
                         hugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h),
                                         pages_per_huge_page(h), folio);
                         spin_unlock_irq(&hugetlb_lock);
                 }
         }
 
         if (!memcg_charge_ret)
                 mem_cgroup_commit_charge(folio, memcg);
         mem_cgroup_put(memcg);
 
         return folio;
 
 out_uncharge_cgroup:
         hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg);
 out_uncharge_cgroup_reservation:
         if (deferred_reserve)
                 hugetlb_cgroup_uncharge_cgroup_rsvd(idx, pages_per_huge_page(h),
                                                     h_cg);
 out_subpool_put:
         if (map_chg || avoid_reserve)
                 hugepage_subpool_put_pages(spool, 1);
 out_end_reservation:
         vma_end_reservation(h, vma, addr);
         if (!memcg_charge_ret)
                 mem_cgroup_cancel_charge(memcg, nr_pages);
         mem_cgroup_put(memcg);
         return ERR_PTR(-ENOSPC);
 }
 
 int alloc_bootmem_huge_page(struct hstate *h, int nid)
         __attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
 int __alloc_bootmem_huge_page(struct hstate *h, int nid)
 {
         struct huge_bootmem_page *m = NULL; /* initialize for clang */
         int nr_nodes, node = nid;
 
         /* do node specific alloc */
         if (nid != NUMA_NO_NODE) {
                 m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h),
                                 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
                 if (!m)
                         return 0;
                 goto found;
         }
         /* allocate from next node when distributing huge pages */
         for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, &node_states[N_MEMORY]) {
                 m = memblock_alloc_try_nid_raw(
                                 huge_page_size(h), huge_page_size(h),
                                 0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
                 /*
                  * Use the beginning of the huge page to store the
                  * huge_bootmem_page struct (until gather_bootmem
                  * puts them into the mem_map).
                  */
                 if (!m)
                         return 0;
                 goto found;
         }
 
 found:
 
         /*
          * Only initialize the head struct page in memmap_init_reserved_pages,
          * rest of the struct pages will be initialized by the HugeTLB
          * subsystem itself.
          * The head struct page is used to get folio information by the HugeTLB
          * subsystem like zone id and node id.
          */
         memblock_reserved_mark_noinit(virt_to_phys((void *)m + PAGE_SIZE),
                 huge_page_size(h) - PAGE_SIZE);
         /* Put them into a private list first because mem_map is not up yet */
         INIT_LIST_HEAD(&m->list);
         list_add(&m->list, &huge_boot_pages[node]);
         m->hstate = h;
         return 1;
 }
 
 /* Initialize [start_page:end_page_number] tail struct pages of a hugepage */
 static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
                                         unsigned long start_page_number,
                                         unsigned long end_page_number)
 {
         enum zone_type zone = zone_idx(folio_zone(folio));
         int nid = folio_nid(folio);
         unsigned long head_pfn = folio_pfn(folio);
         unsigned long pfn, end_pfn = head_pfn + end_page_number;
         int ret;
 
         for (pfn = head_pfn + start_page_number; pfn < end_pfn; pfn++) {
                 struct page *page = pfn_to_page(pfn);
 
                 __init_single_page(page, pfn, zone, nid);
                 prep_compound_tail((struct page *)folio, pfn - head_pfn);
                 ret = page_ref_freeze(page, 1);
                 VM_BUG_ON(!ret);
         }
 }
 
 static void __init hugetlb_folio_init_vmemmap(struct folio *folio,
                                               struct hstate *h,
                                               unsigned long nr_pages)
 {
         int ret;
 
         /* Prepare folio head */
         __folio_clear_reserved(folio);
         __folio_set_head(folio);
         ret = folio_ref_freeze(folio, 1);
         VM_BUG_ON(!ret);
         /* Initialize the necessary tail struct pages */
         hugetlb_folio_init_tail_vmemmap(folio, 1, nr_pages);
         prep_compound_head((struct page *)folio, huge_page_order(h));
 }
 
 static void __init prep_and_add_bootmem_folios(struct hstate *h,
                                         struct list_head *folio_list)
 {
         unsigned long flags;
         struct folio *folio, *tmp_f;
 
         /* Send list for bulk vmemmap optimization processing */
         hugetlb_vmemmap_optimize_folios(h, folio_list);
 
         list_for_each_entry_safe(folio, tmp_f, folio_list, lru) {
                 if (!folio_test_hugetlb_vmemmap_optimized(folio)) {
                         /*
                          * If HVO fails, initialize all tail struct pages
                          * We do not worry about potential long lock hold
                          * time as this is early in boot and there should
                          * be no contention.
                          */
                         hugetlb_folio_init_tail_vmemmap(folio,
                                         HUGETLB_VMEMMAP_RESERVE_PAGES,
                                         pages_per_huge_page(h));
                 }
                 /* Subdivide locks to achieve better parallel performance */
                 spin_lock_irqsave(&hugetlb_lock, flags);
                 __prep_account_new_huge_page(h, folio_nid(folio));
                 enqueue_hugetlb_folio(h, folio);
                 spin_unlock_irqrestore(&hugetlb_lock, flags);
         }
 }
 
 /*
  * Put bootmem huge pages into the standard lists after mem_map is up.
  * Note: This only applies to gigantic (order > MAX_PAGE_ORDER) pages.
  */
 static void __init gather_bootmem_prealloc_node(unsigned long nid)
 {
         LIST_HEAD(folio_list);
         struct huge_bootmem_page *m;
         struct hstate *h = NULL, *prev_h = NULL;
 
         list_for_each_entry(m, &huge_boot_pages[nid], list) {
                 struct page *page = virt_to_page(m);
                 struct folio *folio = (void *)page;
 
                 h = m->hstate;
                 /*
                  * It is possible to have multiple huge page sizes (hstates)
                  * in this list.  If so, process each size separately.
                  */
                 if (h != prev_h && prev_h != NULL)
                         prep_and_add_bootmem_folios(prev_h, &folio_list);
                 prev_h = h;
 
                 VM_BUG_ON(!hstate_is_gigantic(h));
                 WARN_ON(folio_ref_count(folio) != 1);
 
                 hugetlb_folio_init_vmemmap(folio, h,
                                            HUGETLB_VMEMMAP_RESERVE_PAGES);
                 init_new_hugetlb_folio(h, folio);
                 list_add(&folio->lru, &folio_list);
 
                 /*
                  * We need to restore the 'stolen' pages to totalram_pages
                  * in order to fix confusing memory reports from free(1) and
                  * other side-effects, like CommitLimit going negative.
                  */
                 adjust_managed_page_count(page, pages_per_huge_page(h));
                 cond_resched();
         }
 
         prep_and_add_bootmem_folios(h, &folio_list);
 }
 
 static void __init gather_bootmem_prealloc_parallel(unsigned long start,
                                                     unsigned long end, void *arg)
 {
         int nid;
 
         for (nid = start; nid < end; nid++)
                 gather_bootmem_prealloc_node(nid);
 }
 
 static void __init gather_bootmem_prealloc(void)
 {
         struct padata_mt_job job = {
                 .thread_fn      = gather_bootmem_prealloc_parallel,
                 .fn_arg         = NULL,
                 .start          = 0,
                 .size           = num_node_state(N_MEMORY),
                 .align          = 1,
                 .min_chunk      = 1,
                 .max_threads    = num_node_state(N_MEMORY),
                 .numa_aware     = true,
         };
 
         padata_do_multithreaded(&job);
 }
 
 static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
 {
         unsigned long i;
         char buf[32];
 
         for (i = 0; i < h->max_huge_pages_node[nid]; ++i) {
                 if (hstate_is_gigantic(h)) {
                         if (!alloc_bootmem_huge_page(h, nid))
                                 break;
                 } else {
                         struct folio *folio;
                         gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
 
                         folio = alloc_fresh_hugetlb_folio(h, gfp_mask, nid,
                                         &node_states[N_MEMORY]);
                         if (!folio)
                                 break;
                         free_huge_folio(folio); /* free it into the hugepage allocator */
                 }
                 cond_resched();
         }
         if (i == h->max_huge_pages_node[nid])
                 return;
 
         string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
         pr_warn("HugeTLB: allocating %u of page size %s failed node%d.  Only allocated %lu hugepages.\n",
                 h->max_huge_pages_node[nid], buf, nid, i);
         h->max_huge_pages -= (h->max_huge_pages_node[nid] - i);
         h->max_huge_pages_node[nid] = i;
 }
 
 static bool __init hugetlb_hstate_alloc_pages_specific_nodes(struct hstate *h)
 {
         int i;
         bool node_specific_alloc = false;
 
         for_each_online_node(i) {
                 if (h->max_huge_pages_node[i] > 0) {
                         hugetlb_hstate_alloc_pages_onenode(h, i);
                         node_specific_alloc = true;
                 }
         }
 
         return node_specific_alloc;
 }
 
 static void __init hugetlb_hstate_alloc_pages_errcheck(unsigned long allocated, struct hstate *h)
 {
         if (allocated < h->max_huge_pages) {
                 char buf[32];
 
                 string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
                 pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
                         h->max_huge_pages, buf, allocated);
                 h->max_huge_pages = allocated;
         }
 }
 
 static void __init hugetlb_pages_alloc_boot_node(unsigned long start, unsigned long end, void *arg)
 {
         struct hstate *h = (struct hstate *)arg;
         int i, num = end - start;
         nodemask_t node_alloc_noretry;
         LIST_HEAD(folio_list);
         int next_node = first_online_node;
 
         /* Bit mask controlling how hard we retry per-node allocations.*/
         nodes_clear(node_alloc_noretry);
 
         for (i = 0; i < num; ++i) {
                 struct folio *folio = alloc_pool_huge_folio(h, &node_states[N_MEMORY],
                                                 &node_alloc_noretry, &next_node);
                 if (!folio)
                         break;
 
                 list_move(&folio->lru, &folio_list);
                 cond_resched();
         }
 
         prep_and_add_allocated_folios(h, &folio_list);
 }
 
 static unsigned long __init hugetlb_gigantic_pages_alloc_boot(struct hstate *h)
 {
         unsigned long i;
 
         for (i = 0; i < h->max_huge_pages; ++i) {
                 if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
                         break;
                 cond_resched();
         }
 
         return i;
 }
 
 static unsigned long __init hugetlb_pages_alloc_boot(struct hstate *h)
 {
         struct padata_mt_job job = {
                 .fn_arg         = h,
                 .align          = 1,
                 .numa_aware     = true
         };
 
         job.thread_fn   = hugetlb_pages_alloc_boot_node;
         job.start       = 0;
         job.size        = h->max_huge_pages;
 
         /*
          * job.max_threads is twice the num_node_state(N_MEMORY),
          *
          * Tests below indicate that a multiplier of 2 significantly improves
          * performance, and although larger values also provide improvements,
          * the gains are marginal.
          *
          * Therefore, choosing 2 as the multiplier strikes a good balance between
          * enhancing parallel processing capabilities and maintaining efficient
          * resource management.
          *
          * +------------+-------+-------+-------+-------+-------+
          * | multiplier |   1   |   2   |   3   |   4   |   5   |
          * +------------+-------+-------+-------+-------+-------+
          * | 256G 2node | 358ms | 215ms | 157ms | 134ms | 126ms |
          * | 2T   4node | 979ms | 679ms | 543ms | 489ms | 481ms |
          * | 50G  2node | 71ms  | 44ms  | 37ms  | 30ms  | 31ms  |
          * +------------+-------+-------+-------+-------+-------+
          */
         job.max_threads = num_node_state(N_MEMORY) * 2;
         job.min_chunk   = h->max_huge_pages / num_node_state(N_MEMORY) / 2;
         padata_do_multithreaded(&job);
 
         return h->nr_huge_pages;
 }
 
 /*
  * NOTE: this routine is called in different contexts for gigantic and
  * non-gigantic pages.
  * - For gigantic pages, this is called early in the boot process and
  *   pages are allocated from memblock allocated or something similar.
  *   Gigantic pages are actually added to pools later with the routine
  *   gather_bootmem_prealloc.
  * - For non-gigantic pages, this is called later in the boot process after
  *   all of mm is up and functional.  Pages are allocated from buddy and
  *   then added to hugetlb pools.
  */
 static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 {
         unsigned long allocated;
         static bool initialized __initdata;
 
         /* skip gigantic hugepages allocation if hugetlb_cma enabled */
         if (hstate_is_gigantic(h) && hugetlb_cma_size) {
                 pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip boot time allocation\n");
                 return;
         }
 
         /* hugetlb_hstate_alloc_pages will be called many times, initialize huge_boot_pages once */
         if (!initialized) {
                 int i = 0;
 
                 for (i = 0; i < MAX_NUMNODES; i++)
                         INIT_LIST_HEAD(&huge_boot_pages[i]);
                 initialized = true;
         }
 
         /* do node specific alloc */
         if (hugetlb_hstate_alloc_pages_specific_nodes(h))
                 return;
 
         /* below will do all node balanced alloc */
         if (hstate_is_gigantic(h))
                 allocated = hugetlb_gigantic_pages_alloc_boot(h);
         else
                 allocated = hugetlb_pages_alloc_boot(h);
 
         hugetlb_hstate_alloc_pages_errcheck(allocated, h);
 }
 
 static void __init hugetlb_init_hstates(void)
 {
         struct hstate *h, *h2;
 
         for_each_hstate(h) {
                 /* oversize hugepages were init'ed in early boot */
                 if (!hstate_is_gigantic(h))
                         hugetlb_hstate_alloc_pages(h);
 
                 /*
                  * Set demote order for each hstate.  Note that
                  * h->demote_order is initially 0.
                  * - We can not demote gigantic pages if runtime freeing
                  *   is not supported, so skip this.
                  * - If CMA allocation is possible, we can not demote
                  *   HUGETLB_PAGE_ORDER or smaller size pages.
                  */
                 if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                         continue;
                 if (hugetlb_cma_size && h->order <= HUGETLB_PAGE_ORDER)
                         continue;
                 for_each_hstate(h2) {
                         if (h2 == h)
                                 continue;
                         if (h2->order < h->order &&
                             h2->order > h->demote_order)
                                 h->demote_order = h2->order;
                 }
         }
 }
 
 static void __init report_hugepages(void)
 {
         struct hstate *h;
 
         for_each_hstate(h) {
                 char buf[32];
 
                 string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
                 pr_info("HugeTLB: registered %s page size, pre-allocated %ld pages\n",
                         buf, h->free_huge_pages);
                 pr_info("HugeTLB: %d KiB vmemmap can be freed for a %s page\n",
                         hugetlb_vmemmap_optimizable_size(h) / SZ_1K, buf);
         }
 }
 
 #ifdef CONFIG_HIGHMEM
 static void try_to_free_low(struct hstate *h, unsigned long count,
                                                 nodemask_t *nodes_allowed)
 {
         int i;
         LIST_HEAD(page_list);
 
         lockdep_assert_held(&hugetlb_lock);
         if (hstate_is_gigantic(h))
                 return;
 
         /*
          * Collect pages to be freed on a list, and free after dropping lock
          */
         for_each_node_mask(i, *nodes_allowed) {
                 struct folio *folio, *next;
                 struct list_head *freel = &h->hugepage_freelists[i];
                 list_for_each_entry_safe(folio, next, freel, lru) {
                         if (count >= h->nr_huge_pages)
                                 goto out;
                         if (folio_test_highmem(folio))
                                 continue;
                         remove_hugetlb_folio(h, folio, false);
                         list_add(&folio->lru, &page_list);
                 }
         }
 
 out:
         spin_unlock_irq(&hugetlb_lock);
         update_and_free_pages_bulk(h, &page_list);
         spin_lock_irq(&hugetlb_lock);
 }
 #else
 static inline void try_to_free_low(struct hstate *h, unsigned long count,
                                                 nodemask_t *nodes_allowed)
 {
 }
 #endif
 
 /*
  * Increment or decrement surplus_huge_pages.  Keep node-specific counters
  * balanced by operating on them in a round-robin fashion.
  * Returns 1 if an adjustment was made.
  */
 static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
                                 int delta)
 {
         int nr_nodes, node;
 
         lockdep_assert_held(&hugetlb_lock);
         VM_BUG_ON(delta != -1 && delta != 1);
 
         if (delta < 0) {
                 for_each_node_mask_to_alloc(&h->next_nid_to_alloc, nr_nodes, node, nodes_allowed) {
                         if (h->surplus_huge_pages_node[node])
                                 goto found;
                 }
         } else {
                 for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
                         if (h->surplus_huge_pages_node[node] <
                                         h->nr_huge_pages_node[node])
                                 goto found;
                 }
         }
         return 0;
 
 found:
         h->surplus_huge_pages += delta;
         h->surplus_huge_pages_node[node] += delta;
         return 1;
 }
 
 #define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
 static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
                               nodemask_t *nodes_allowed)
 {
         unsigned long min_count;
         unsigned long allocated;
         struct folio *folio;
         LIST_HEAD(page_list);
         NODEMASK_ALLOC(nodemask_t, node_alloc_noretry, GFP_KERNEL);
 
         /*
          * Bit mask controlling how hard we retry per-node allocations.
          * If we can not allocate the bit mask, do not attempt to allocate
          * the requested huge pages.
          */
         if (node_alloc_noretry)
                 nodes_clear(*node_alloc_noretry);
         else
                 return -ENOMEM;
 
         /*
          * resize_lock mutex prevents concurrent adjustments to number of
          * pages in hstate via the proc/sysfs interfaces.
          */
         mutex_lock(&h->resize_lock);
         flush_free_hpage_work(h);
         spin_lock_irq(&hugetlb_lock);
 
         /*
          * Check for a node specific request.
          * Changing node specific huge page count may require a corresponding
          * change to the global count.  In any case, the passed node mask
          * (nodes_allowed) will restrict alloc/free to the specified node.
          */
         if (nid != NUMA_NO_NODE) {
                 unsigned long old_count = count;
 
                 count += persistent_huge_pages(h) -
                          (h->nr_huge_pages_node[nid] -
                           h->surplus_huge_pages_node[nid]);
                 /*
                  * User may have specified a large count value which caused the
                  * above calculation to overflow.  In this case, they wanted
                  * to allocate as many huge pages as possible.  Set count to
                  * largest possible value to align with their intention.
                  */
                 if (count < old_count)
                         count = ULONG_MAX;
         }
 
         /*
          * Gigantic pages runtime allocation depend on the capability for large
          * page range allocation.
          * If the system does not provide this feature, return an error when
          * the user tries to allocate gigantic pages but let the user free the
          * boottime allocated gigantic pages.
          */
         if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
                 if (count > persistent_huge_pages(h)) {
                         spin_unlock_irq(&hugetlb_lock);
                         mutex_unlock(&h->resize_lock);
                         NODEMASK_FREE(node_alloc_noretry);
                         return -EINVAL;
                 }
                 /* Fall through to decrease pool */
         }
 
         /*
          * Increase the pool size
          * First take pages out of surplus state.  Then make up the
          * remaining difference by allocating fresh huge pages.
          *
          * We might race with alloc_surplus_hugetlb_folio() here and be unable
          * to convert a surplus huge page to a normal huge page. That is
          * not critical, though, it just means the overall size of the
          * pool might be one hugepage larger than it needs to be, but
          * within all the constraints specified by the sysctls.
          */
         while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
                 if (!adjust_pool_surplus(h, nodes_allowed, -1))
                         break;
         }
 
         allocated = 0;
         while (count > (persistent_huge_pages(h) + allocated)) {
                 /*
                  * If this allocation races such that we no longer need the
                  * page, free_huge_folio will handle it by freeing the page
                  * and reducing the surplus.
                  */
                 spin_unlock_irq(&hugetlb_lock);
 
                 /* yield cpu to avoid soft lockup */
                 cond_resched();
 
                 folio = alloc_pool_huge_folio(h, nodes_allowed,
                                                 node_alloc_noretry,
                                                 &h->next_nid_to_alloc);
                 if (!folio) {
                         prep_and_add_allocated_folios(h, &page_list);
                         spin_lock_irq(&hugetlb_lock);
                         goto out;
                 }
 
                 list_add(&folio->lru, &page_list);
                 allocated++;
 
                 /* Bail for signals. Probably ctrl-c from user */
                 if (signal_pending(current)) {
                         prep_and_add_allocated_folios(h, &page_list);
                         spin_lock_irq(&hugetlb_lock);
                         goto out;
                 }
 
                 spin_lock_irq(&hugetlb_lock);
         }
 
         /* Add allocated pages to the pool */
         if (!list_empty(&page_list)) {
                 spin_unlock_irq(&hugetlb_lock);
                 prep_and_add_allocated_folios(h, &page_list);
                 spin_lock_irq(&hugetlb_lock);
         }
 
         /*
          * Decrease the pool size
          * First return free pages to the buddy allocator (being careful
          * to keep enough around to satisfy reservations).  Then place
          * pages into surplus state as needed so the pool will shrink
          * to the desired size as pages become free.
          *
          * By placing pages into the surplus state independent of the
          * overcommit value, we are allowing the surplus pool size to
          * exceed overcommit. There are few sane options here. Since
          * alloc_surplus_hugetlb_folio() is checking the global counter,
          * though, we'll note that we're not allowed to exceed surplus
          * and won't grow the pool anywhere else. Not until one of the
          * sysctls are changed, or the surplus pages go out of use.
          */
         min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;
         min_count = max(count, min_count);
         try_to_free_low(h, min_count, nodes_allowed);
 
         /*
          * Collect pages to be removed on list without dropping lock
          */
         while (min_count < persistent_huge_pages(h)) {
                 folio = remove_pool_hugetlb_folio(h, nodes_allowed, 0);
                 if (!folio)
                         break;
 
                 list_add(&folio->lru, &page_list);
         }
         /* free the pages after dropping lock */
         spin_unlock_irq(&hugetlb_lock);
         update_and_free_pages_bulk(h, &page_list);
         flush_free_hpage_work(h);
         spin_lock_irq(&hugetlb_lock);
 
         while (count < persistent_huge_pages(h)) {
                 if (!adjust_pool_surplus(h, nodes_allowed, 1))
                         break;
         }
 out:
         h->max_huge_pages = persistent_huge_pages(h);
         spin_unlock_irq(&hugetlb_lock);
         mutex_unlock(&h->resize_lock);
 
         NODEMASK_FREE(node_alloc_noretry);
 
         return 0;
 }
 
 static long demote_free_hugetlb_folios(struct hstate *src, struct hstate *dst,
                                        struct list_head *src_list)
 {
         long rc;
         struct folio *folio, *next;
         LIST_HEAD(dst_list);
         LIST_HEAD(ret_list);
 
         rc = hugetlb_vmemmap_restore_folios(src, src_list, &ret_list);
         list_splice_init(&ret_list, src_list);
 
         /*
          * Taking target hstate mutex synchronizes with set_max_huge_pages.
          * Without the mutex, pages added to target hstate could be marked
          * as surplus.
          *
          * Note that we already hold src->resize_lock.  To prevent deadlock,
          * use the convention of always taking larger size hstate mutex first.
          */
         mutex_lock(&dst->resize_lock);
 
         list_for_each_entry_safe(folio, next, src_list, lru) {
                 int i;
 
                 if (folio_test_hugetlb_vmemmap_optimized(folio))
                         continue;
 
                 list_del(&folio->lru);
                 /*
                  * Use destroy_compound_hugetlb_folio_for_demote for all huge page
                  * sizes as it will not ref count folios.
                  */
                 destroy_compound_hugetlb_folio_for_demote(folio, huge_page_order(src));
 
                 for (i = 0; i < pages_per_huge_page(src); i += pages_per_huge_page(dst)) {
                         struct page *page = folio_page(folio, i);
 
                         if (hstate_is_gigantic(dst))
                                 prep_compound_gigantic_folio_for_demote(page_folio(page),
                                                                         dst->order);
                         else
                                 prep_compound_page(page, dst->order);
                         set_page_private(page, 0);
 
                         init_new_hugetlb_folio(dst, page_folio(page));
                         list_add(&page->lru, &dst_list);
                 }
         }
 
         prep_and_add_allocated_folios(dst, &dst_list);
 
         mutex_unlock(&dst->resize_lock);
 
         return rc;
 }
 
 static long demote_pool_huge_page(struct hstate *src, nodemask_t *nodes_allowed,
                                   unsigned long nr_to_demote)
         __must_hold(&hugetlb_lock)
 {
         int nr_nodes, node;
         struct hstate *dst;
         long rc = 0;
         long nr_demoted = 0;
 
         lockdep_assert_held(&hugetlb_lock);
 
         /* We should never get here if no demote order */
         if (!src->demote_order) {
                 pr_warn("HugeTLB: NULL demote order passed to demote_pool_huge_page.\n");
                 return -EINVAL;         /* internal error */
         }
         dst = size_to_hstate(PAGE_SIZE << src->demote_order);
 
         for_each_node_mask_to_free(src, nr_nodes, node, nodes_allowed) {
                 LIST_HEAD(list);
                 struct folio *folio, *next;
 
                 list_for_each_entry_safe(folio, next, &src->hugepage_freelists[node], lru) {
                         if (folio_test_hwpoison(folio))
                                 continue;
 
                         remove_hugetlb_folio(src, folio, false);
                         list_add(&folio->lru, &list);
 
                         if (++nr_demoted == nr_to_demote)
                                 break;
                 }
 
                 spin_unlock_irq(&hugetlb_lock);
 
                 rc = demote_free_hugetlb_folios(src, dst, &list);
 
                 spin_lock_irq(&hugetlb_lock);
 
                 list_for_each_entry_safe(folio, next, &list, lru) {
                         list_del(&folio->lru);
                         add_hugetlb_folio(src, folio, false);
 
                         nr_demoted--;
                 }
 
                 if (rc < 0 || nr_demoted == nr_to_demote)
                         break;
         }
 
         /*
          * Not absolutely necessary, but for consistency update max_huge_pages
          * based on pool changes for the demoted page.
          */
         src->max_huge_pages -= nr_demoted;
         dst->max_huge_pages += nr_demoted << (huge_page_order(src) - huge_page_order(dst));
 
         if (rc < 0)
                 return rc;
 
         if (nr_demoted)
                 return nr_demoted;
         /*
          * Only way to get here is if all pages on free lists are poisoned.
          * Return -EBUSY so that caller will not retry.
          */
         return -EBUSY;
 }
 
 #define HSTATE_ATTR_RO(_name) \
         static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
 
 #define HSTATE_ATTR_WO(_name) \
         static struct kobj_attribute _name##_attr = __ATTR_WO(_name)
 
 #define HSTATE_ATTR(_name) \
         static struct kobj_attribute _name##_attr = __ATTR_RW(_name)
 
 static struct kobject *hugepages_kobj;
 static struct kobject *hstate_kobjs[HUGE_MAX_HSTATE];
 
 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp);
 
 static struct hstate *kobj_to_hstate(struct kobject *kobj, int *nidp)
 {
         int i;
 
         for (i = 0; i < HUGE_MAX_HSTATE; i++)
                 if (hstate_kobjs[i] == kobj) {
                         if (nidp)
                                 *nidp = NUMA_NO_NODE;
                         return &hstates[i];
                 }
 
         return kobj_to_node_hstate(kobj, nidp);
 }
 
 static ssize_t nr_hugepages_show_common(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
         struct hstate *h;
         unsigned long nr_huge_pages;
         int nid;
 
         h = kobj_to_hstate(kobj, &nid);
         if (nid == NUMA_NO_NODE)
                 nr_huge_pages = h->nr_huge_pages;
         else
                 nr_huge_pages = h->nr_huge_pages_node[nid];
 
         return sysfs_emit(buf, "%lu\n", nr_huge_pages);
 }
 
 static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
                                            struct hstate *h, int nid,
                                            unsigned long count, size_t len)
 {
         int err;
         nodemask_t nodes_allowed, *n_mask;
 
         if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
                 return -EINVAL;
 
         if (nid == NUMA_NO_NODE) {
                 /*
                  * global hstate attribute
                  */
                 if (!(obey_mempolicy &&
                                 init_nodemask_of_mempolicy(&nodes_allowed)))
                         n_mask = &node_states[N_MEMORY];
                 else
                         n_mask = &nodes_allowed;
         } else {
                 /*
                  * Node specific request.  count adjustment happens in
                  * set_max_huge_pages() after acquiring hugetlb_lock.
                  */
                 init_nodemask_of_node(&nodes_allowed, nid);
                 n_mask = &nodes_allowed;
         }
 
         err = set_max_huge_pages(h, count, nid, n_mask);
 
         return err ? err : len;
 }
 
 static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
                                          struct kobject *kobj, const char *buf,
                                          size_t len)
 {
         struct hstate *h;
         unsigned long count;
         int nid;
         int err;
 
         err = kstrtoul(buf, 10, &count);
         if (err)
                 return err;
 
         h = kobj_to_hstate(kobj, &nid);
         return __nr_hugepages_store_common(obey_mempolicy, h, nid, count, len);
 }
 
 static ssize_t nr_hugepages_show(struct kobject *kobj,
                                        struct kobj_attribute *attr, char *buf)
 {
         return nr_hugepages_show_common(kobj, attr, buf);
 }
 
 static ssize_t nr_hugepages_store(struct kobject *kobj,
                struct kobj_attribute *attr, const char *buf, size_t len)
 {
         return nr_hugepages_store_common(false, kobj, buf, len);
 }
 HSTATE_ATTR(nr_hugepages);
 
 #ifdef CONFIG_NUMA
 
 /*
  * hstate attribute for optionally mempolicy-based constraint on persistent
  * huge page alloc/free.
  */
 static ssize_t nr_hugepages_mempolicy_show(struct kobject *kobj,
                                            struct kobj_attribute *attr,
                                            char *buf)
 {
         return nr_hugepages_show_common(kobj, attr, buf);
 }
 
 static ssize_t nr_hugepages_mempolicy_store(struct kobject *kobj,
                struct kobj_attribute *attr, const char *buf, size_t len)
 {
         return nr_hugepages_store_common(true, kobj, buf, len);
 }
 HSTATE_ATTR(nr_hugepages_mempolicy);
 #endif
 
 
 static ssize_t nr_overcommit_hugepages_show(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
         struct hstate *h = kobj_to_hstate(kobj, NULL);
         return sysfs_emit(buf, "%lu\n", h->nr_overcommit_huge_pages);
 }
 
 static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
                 struct kobj_attribute *attr, const char *buf, size_t count)
 {
         int err;
         unsigned long input;
         struct hstate *h = kobj_to_hstate(kobj, NULL);
 
         if (hstate_is_gigantic(h))
                 return -EINVAL;
 
         err = kstrtoul(buf, 10, &input);
         if (err)
                 return err;
 
         spin_lock_irq(&hugetlb_lock);
         h->nr_overcommit_huge_pages = input;
         spin_unlock_irq(&hugetlb_lock);
 
         return count;
 }
 HSTATE_ATTR(nr_overcommit_hugepages);
 
 static ssize_t free_hugepages_show(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
         struct hstate *h;
         unsigned long free_huge_pages;
         int nid;
 
         h = kobj_to_hstate(kobj, &nid);
         if (nid == NUMA_NO_NODE)
                 free_huge_pages = h->free_huge_pages;
         else
                 free_huge_pages = h->free_huge_pages_node[nid];
 
         return sysfs_emit(buf, "%lu\n", free_huge_pages);
 }
 HSTATE_ATTR_RO(free_hugepages);
 
 static ssize_t resv_hugepages_show(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
         struct hstate *h = kobj_to_hstate(kobj, NULL);
         return sysfs_emit(buf, "%lu\n", h->resv_huge_pages);
 }
 HSTATE_ATTR_RO(resv_hugepages);
 
 static ssize_t surplus_hugepages_show(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
         struct hstate *h;
         unsigned long surplus_huge_pages;
         int nid;
 
         h = kobj_to_hstate(kobj, &nid);
         if (nid == NUMA_NO_NODE)
                 surplus_huge_pages = h->surplus_huge_pages;
         else
                 surplus_huge_pages = h->surplus_huge_pages_node[nid];
 
         return sysfs_emit(buf, "%lu\n", surplus_huge_pages);
 }
 HSTATE_ATTR_RO(surplus_hugepages);
 
 static ssize_t demote_store(struct kobject *kobj,
                struct kobj_attribute *attr, const char *buf, size_t len)
 {
         unsigned long nr_demote;
         unsigned long nr_available;
         nodemask_t nodes_allowed, *n_mask;
         struct hstate *h;
         int err;
         int nid;
 
         err = kstrtoul(buf, 10, &nr_demote);
         if (err)
                 return err;
         h = kobj_to_hstate(kobj, &nid);
 
         if (nid != NUMA_NO_NODE) {
                 init_nodemask_of_node(&nodes_allowed, nid);
                 n_mask = &nodes_allowed;
         } else {
                 n_mask = &node_states[N_MEMORY];
         }
 
         /* Synchronize with other sysfs operations modifying huge pages */
         mutex_lock(&h->resize_lock);
         spin_lock_irq(&hugetlb_lock);
 
         while (nr_demote) {
                 long rc;
 
                 /*
                  * Check for available pages to demote each time thorough the
                  * loop as demote_pool_huge_page will drop hugetlb_lock.
                  */
                 if (nid != NUMA_NO_NODE)
                         nr_available = h->free_huge_pages_node[nid];
                 else
                         nr_available = h->free_huge_pages;
                 nr_available -= h->resv_huge_pages;
                 if (!nr_available)
                         break;
 
                 rc = demote_pool_huge_page(h, n_mask, nr_demote);
                 if (rc < 0) {
                         err = rc;
                         break;
                 }
 
                 nr_demote -= rc;
         }
 
         spin_unlock_irq(&hugetlb_lock);
         mutex_unlock(&h->resize_lock);
 
         if (err)
                 return err;
         return len;
 }
 HSTATE_ATTR_WO(demote);
 
 static ssize_t demote_size_show(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
         struct hstate *h = kobj_to_hstate(kobj, NULL);
         unsigned long demote_size = (PAGE_SIZE << h->demote_order) / SZ_1K;
 
         return sysfs_emit(buf, "%lukB\n", demote_size);
 }
 
 static ssize_t demote_size_store(struct kobject *kobj,
                                         struct kobj_attribute *attr,
                                         const char *buf, size_t count)
 {
         struct hstate *h, *demote_hstate;
         unsigned long demote_size;
         unsigned int demote_order;
 
         demote_size = (unsigned long)memparse(buf, NULL);
 
         demote_hstate = size_to_hstate(demote_size);
         if (!demote_hstate)
                 return -EINVAL;
         demote_order = demote_hstate->order;
         if (demote_order < HUGETLB_PAGE_ORDER)
                 return -EINVAL;
 
         /* demote order must be smaller than hstate order */
         h = kobj_to_hstate(kobj, NULL);
         if (demote_order >= h->order)
                 return -EINVAL;
 
         /* resize_lock synchronizes access to demote size and writes */
         mutex_lock(&h->resize_lock);
         h->demote_order = demote_order;
         mutex_unlock(&h->resize_lock);
 
         return count;
 }
 HSTATE_ATTR(demote_size);
 
 static struct attribute *hstate_attrs[] = {
         &nr_hugepages_attr.attr,
         &nr_overcommit_hugepages_attr.attr,
         &free_hugepages_attr.attr,
         &resv_hugepages_attr.attr,
         &surplus_hugepages_attr.attr,
 #ifdef CONFIG_NUMA
         &nr_hugepages_mempolicy_attr.attr,
 #endif
         NULL,
 };
 
 static const struct attribute_group hstate_attr_group = {
         .attrs = hstate_attrs,
 };
 
 static struct attribute *hstate_demote_attrs[] = {
         &demote_size_attr.attr,
         &demote_attr.attr,
         NULL,
 };
 
 static const struct attribute_group hstate_demote_attr_group = {
         .attrs = hstate_demote_attrs,
 };
 
 static int hugetlb_sysfs_add_hstate(struct hstate *h, struct kobject *parent,
                                     struct kobject **hstate_kobjs,
                                     const struct attribute_group *hstate_attr_group)
 {
         int retval;
         int hi = hstate_index(h);
 
         hstate_kobjs[hi] = kobject_create_and_add(h->name, parent);
         if (!hstate_kobjs[hi])
                 return -ENOMEM;
 
         retval = sysfs_create_group(hstate_kobjs[hi], hstate_attr_group);
         if (retval) {
                 kobject_put(hstate_kobjs[hi]);
                 hstate_kobjs[hi] = NULL;
                 return retval;
         }
 
         if (h->demote_order) {
                 retval = sysfs_create_group(hstate_kobjs[hi],
                                             &hstate_demote_attr_group);
                 if (retval) {
                         pr_warn("HugeTLB unable to create demote interfaces for %s\n", h->name);
                         sysfs_remove_group(hstate_kobjs[hi], hstate_attr_group);
                         kobject_put(hstate_kobjs[hi]);
                         hstate_kobjs[hi] = NULL;
                         return retval;
                 }
         }
 
         return 0;
 }
 
 #ifdef CONFIG_NUMA
 static bool hugetlb_sysfs_initialized __ro_after_init;
 
 /*
  * node_hstate/s - associate per node hstate attributes, via their kobjects,
  * with node devices in node_devices[] using a parallel array.  The array
  * index of a node device or _hstate == node id.
  * This is here to avoid any static dependency of the node device driver, in
  * the base kernel, on the hugetlb module.
  */
 struct node_hstate {
         struct kobject          *hugepages_kobj;
         struct kobject          *hstate_kobjs[HUGE_MAX_HSTATE];
 };
 static struct node_hstate node_hstates[MAX_NUMNODES];
 
 /*
  * A subset of global hstate attributes for node devices
  */
 static struct attribute *per_node_hstate_attrs[] = {
         &nr_hugepages_attr.attr,
         &free_hugepages_attr.attr,
         &surplus_hugepages_attr.attr,
         NULL,
 };
 
 static const struct attribute_group per_node_hstate_attr_group = {
         .attrs = per_node_hstate_attrs,
 };
 
 /*
  * kobj_to_node_hstate - lookup global hstate for node device hstate attr kobj.
  * Returns node id via non-NULL nidp.
  */
 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
 {
         int nid;
 
         for (nid = 0; nid < nr_node_ids; nid++) {
                 struct node_hstate *nhs = &node_hstates[nid];
                 int i;
                 for (i = 0; i < HUGE_MAX_HSTATE; i++)
                         if (nhs->hstate_kobjs[i] == kobj) {
                                 if (nidp)
                                         *nidp = nid;
                                 return &hstates[i];
                         }
         }
 
         BUG();
         return NULL;
 }
 
 /*
  * Unregister hstate attributes from a single node device.
  * No-op if no hstate attributes attached.
  */
 void hugetlb_unregister_node(struct node *node)
 {
         struct hstate *h;
         struct node_hstate *nhs = &node_hstates[node->dev.id];
 
         if (!nhs->hugepages_kobj)
                 return;         /* no hstate attributes */
 
         for_each_hstate(h) {
                 int idx = hstate_index(h);
                 struct kobject *hstate_kobj = nhs->hstate_kobjs[idx];
 
                 if (!hstate_kobj)
                         continue;
                 if (h->demote_order)
                         sysfs_remove_group(hstate_kobj, &hstate_demote_attr_group);
                 sysfs_remove_group(hstate_kobj, &per_node_hstate_attr_group);
                 kobject_put(hstate_kobj);
                 nhs->hstate_kobjs[idx] = NULL;
         }
 
         kobject_put(nhs->hugepages_kobj);
         nhs->hugepages_kobj = NULL;
 }
 
 
 /*
  * Register hstate attributes for a single node device.
  * No-op if attributes already registered.
  */
 void hugetlb_register_node(struct node *node)
 {
         struct hstate *h;
         struct node_hstate *nhs = &node_hstates[node->dev.id];
         int err;
 
         if (!hugetlb_sysfs_initialized)
                 return;
 
         if (nhs->hugepages_kobj)
                 return;         /* already allocated */
 
         nhs->hugepages_kobj = kobject_create_and_add("hugepages",
                                                         &node->dev.kobj);
         if (!nhs->hugepages_kobj)
                 return;
 
         for_each_hstate(h) {
                 err = hugetlb_sysfs_add_hstate(h, nhs->hugepages_kobj,
                                                 nhs->hstate_kobjs,
                                                 &per_node_hstate_attr_group);
                 if (err) {
                         pr_err("HugeTLB: Unable to add hstate %s for node %d\n",
                                 h->name, node->dev.id);
                         hugetlb_unregister_node(node);
                         break;
                 }
         }
 }
 
 /*
  * hugetlb init time:  register hstate attributes for all registered node
  * devices of nodes that have memory.  All on-line nodes should have
  * registered their associated device by this time.
  */
 static void __init hugetlb_register_all_nodes(void)
 {
         int nid;
 
         for_each_online_node(nid)
                 hugetlb_register_node(node_devices[nid]);
 }
 #else   /* !CONFIG_NUMA */
 
 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
 {
         BUG();
         if (nidp)
                 *nidp = -1;
         return NULL;
 }
 
 static void hugetlb_register_all_nodes(void) { }
 
 #endif
 
 #ifdef CONFIG_CMA
 static void __init hugetlb_cma_check(void);
 #else
 static inline __init void hugetlb_cma_check(void)
 {
 }
 #endif
 
 static void __init hugetlb_sysfs_init(void)
 {
         struct hstate *h;
         int err;
 
         hugepages_kobj = kobject_create_and_add("hugepages", mm_kobj);
         if (!hugepages_kobj)
                 return;
 
         for_each_hstate(h) {
                 err = hugetlb_sysfs_add_hstate(h, hugepages_kobj,
                                          hstate_kobjs, &hstate_attr_group);
                 if (err)
                         pr_err("HugeTLB: Unable to add hstate %s", h->name);
         }
 
 #ifdef CONFIG_NUMA
         hugetlb_sysfs_initialized = true;
 #endif
         hugetlb_register_all_nodes();
 }
 
 #ifdef CONFIG_SYSCTL
 static void hugetlb_sysctl_init(void);
 #else
 static inline void hugetlb_sysctl_init(void) { }
 #endif
 
 static int __init hugetlb_init(void)
 {
         int i;
 
         BUILD_BUG_ON(sizeof_field(struct page, private) * BITS_PER_BYTE <
                         __NR_HPAGEFLAGS);
 
         if (!hugepages_supported()) {
                 if (hugetlb_max_hstate || default_hstate_max_huge_pages)
                         pr_warn("HugeTLB: huge pages not supported, ignoring associated command-line parameters\n");
                 return 0;
         }
 
         /*
          * Make sure HPAGE_SIZE (HUGETLB_PAGE_ORDER) hstate exists.  Some
          * architectures depend on setup being done here.
          */
         hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
         if (!parsed_default_hugepagesz) {
                 /*
                  * If we did not parse a default huge page size, set
                  * default_hstate_idx to HPAGE_SIZE hstate. And, if the
                  * number of huge pages for this default size was implicitly
                  * specified, set that here as well.
                  * Note that the implicit setting will overwrite an explicit
                  * setting.  A warning will be printed in this case.
                  */
                 default_hstate_idx = hstate_index(size_to_hstate(HPAGE_SIZE));
                 if (default_hstate_max_huge_pages) {
                         if (default_hstate.max_huge_pages) {
                                 char buf[32];
 
                                 string_get_size(huge_page_size(&default_hstate),
                                         1, STRING_UNITS_2, buf, 32);
                                 pr_warn("HugeTLB: Ignoring hugepages=%lu associated with %s page size\n",
                                         default_hstate.max_huge_pages, buf);
                                 pr_warn("HugeTLB: Using hugepages=%lu for number of default huge pages\n",
                                         default_hstate_max_huge_pages);
                         }
                         default_hstate.max_huge_pages =
                                 default_hstate_max_huge_pages;
 
                         for_each_online_node(i)
                                 default_hstate.max_huge_pages_node[i] =
                                         default_hugepages_in_node[i];
                 }
         }
 
         hugetlb_cma_check();
         hugetlb_init_hstates();
         gather_bootmem_prealloc();
         report_hugepages();
 
         hugetlb_sysfs_init();
         hugetlb_cgroup_file_init();
         hugetlb_sysctl_init();
 
 #ifdef CONFIG_SMP
         num_fault_mutexes = roundup_pow_of_two(8 * num_possible_cpus());
 #else
         num_fault_mutexes = 1;
 #endif
         hugetlb_fault_mutex_table =
                 kmalloc_array(num_fault_mutexes, sizeof(struct mutex),
                               GFP_KERNEL);
         BUG_ON(!hugetlb_fault_mutex_table);
 
         for (i = 0; i < num_fault_mutexes; i++)
                 mutex_init(&hugetlb_fault_mutex_table[i]);
         return 0;
 }
 subsys_initcall(hugetlb_init);
 
 /* Overwritten by architectures with more huge page sizes */
 bool __init __attribute((weak)) arch_hugetlb_valid_size(unsigned long size)
 {
         return size == HPAGE_SIZE;
 }
 
 void __init hugetlb_add_hstate(unsigned int order)
 {
         struct hstate *h;
         unsigned long i;
 
         if (size_to_hstate(PAGE_SIZE << order)) {
                 return;
         }
         BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);
         BUG_ON(order < order_base_2(__NR_USED_SUBPAGE));
         h = &hstates[hugetlb_max_hstate++];
         __mutex_init(&h->resize_lock, "resize mutex", &h->resize_key);
         h->order = order;
         h->mask = ~(huge_page_size(h) - 1);
         for (i = 0; i < MAX_NUMNODES; ++i)
                 INIT_LIST_HEAD(&h->hugepage_freelists[i]);
         INIT_LIST_HEAD(&h->hugepage_activelist);
         h->next_nid_to_alloc = first_memory_node;
         h->next_nid_to_free = first_memory_node;
         snprintf(h->name, HSTATE_NAME_LEN, "hugepages-%lukB",
                                         huge_page_size(h)/SZ_1K);
 
         parsed_hstate = h;
 }
 
 bool __init __weak hugetlb_node_alloc_supported(void)
 {
         return true;
 }
 
 static void __init hugepages_clear_pages_in_node(void)
 {
         if (!hugetlb_max_hstate) {
                 default_hstate_max_huge_pages = 0;
                 memset(default_hugepages_in_node, 0,
                         sizeof(default_hugepages_in_node));
         } else {
                 parsed_hstate->max_huge_pages = 0;
                 memset(parsed_hstate->max_huge_pages_node, 0,
                         sizeof(parsed_hstate->max_huge_pages_node));
         }
 }
 
 /*
  * hugepages command line processing
  * hugepages normally follows a valid hugepagsz or default_hugepagsz
  * specification.  If not, ignore the hugepages value.  hugepages can also
  * be the first huge page command line  option in which case it implicitly
  * specifies the number of huge pages for the default size.
  */
 static int __init hugepages_setup(char *s)
 {
         unsigned long *mhp;
         static unsigned long *last_mhp;
         int node = NUMA_NO_NODE;
         int count;
         unsigned long tmp;
         char *p = s;
 
         if (!parsed_valid_hugepagesz) {
                 pr_warn("HugeTLB: hugepages=%s does not follow a valid hugepagesz, ignoring\n", s);
                 parsed_valid_hugepagesz = true;
                 return 1;
         }
 
         /*
          * !hugetlb_max_hstate means we haven't parsed a hugepagesz= parameter
          * yet, so this hugepages= parameter goes to the "default hstate".
          * Otherwise, it goes with the previously parsed hugepagesz or
          * default_hugepagesz.
          */
         else if (!hugetlb_max_hstate)
                 mhp = &default_hstate_max_huge_pages;
         else
                 mhp = &parsed_hstate->max_huge_pages;
 
         if (mhp == last_mhp) {
                 pr_warn("HugeTLB: hugepages= specified twice without interleaving hugepagesz=, ignoring hugepages=%s\n", s);
                 return 1;
         }
 
         while (*p) {
                 count = 0;
                 if (sscanf(p, "%lu%n", &tmp, &count) != 1)
                         goto invalid;
                 /* Parameter is node format */
                 if (p[count] == ':') {
                         if (!hugetlb_node_alloc_supported()) {
                                 pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
                                 return 1;
                         }
                         if (tmp >= MAX_NUMNODES || !node_online(tmp))
                                 goto invalid;
                         node = array_index_nospec(tmp, MAX_NUMNODES);
                         p += count + 1;
                         /* Parse hugepages */
                         if (sscanf(p, "%lu%n", &tmp, &count) != 1)
                                 goto invalid;
                         if (!hugetlb_max_hstate)
                                 default_hugepages_in_node[node] = tmp;
                         else
                                 parsed_hstate->max_huge_pages_node[node] = tmp;
                         *mhp += tmp;
                         /* Go to parse next node*/
                         if (p[count] == ',')
                                 p += count + 1;
                         else
                                 break;
                 } else {
                         if (p != s)
                                 goto invalid;
                         *mhp = tmp;
                         break;
                 }
         }
 
         /*
          * Global state is always initialized later in hugetlb_init.
          * But we need to allocate gigantic hstates here early to still
          * use the bootmem allocator.
          */
         if (hugetlb_max_hstate && hstate_is_gigantic(parsed_hstate))
                 hugetlb_hstate_alloc_pages(parsed_hstate);
 
         last_mhp = mhp;
 
         return 1;
 
 invalid:
         pr_warn("HugeTLB: Invalid hugepages parameter %s\n", p);
         hugepages_clear_pages_in_node();
         return 1;
 }
 __setup("hugepages=", hugepages_setup);
 
 /*
  * hugepagesz command line processing
  * A specific huge page size can only be specified once with hugepagesz.
  * hugepagesz is followed by hugepages on the command line.  The global
  * variable 'parsed_valid_hugepagesz' is used to determine if prior
  * hugepagesz argument was valid.
  */
 static int __init hugepagesz_setup(char *s)
 {
         unsigned long size;
         struct hstate *h;
 
         parsed_valid_hugepagesz = false;
         size = (unsigned long)memparse(s, NULL);
 
         if (!arch_hugetlb_valid_size(size)) {
                 pr_err("HugeTLB: unsupported hugepagesz=%s\n", s);
                 return 1;
         }
 
         h = size_to_hstate(size);
         if (h) {
                 /*
                  * hstate for this size already exists.  This is normally
                  * an error, but is allowed if the existing hstate is the
                  * default hstate.  More specifically, it is only allowed if
                  * the number of huge pages for the default hstate was not
                  * previously specified.
                  */
                 if (!parsed_default_hugepagesz ||  h != &default_hstate ||
                     default_hstate.max_huge_pages) {
                         pr_warn("HugeTLB: hugepagesz=%s specified twice, ignoring\n", s);
                         return 1;
                 }
 
                 /*
                  * No need to call hugetlb_add_hstate() as hstate already
                  * exists.  But, do set parsed_hstate so that a following
                  * hugepages= parameter will be applied to this hstate.
                  */
                 parsed_hstate = h;
                 parsed_valid_hugepagesz = true;
                 return 1;
         }
 
         hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
         parsed_valid_hugepagesz = true;
         return 1;
 }
 __setup("hugepagesz=", hugepagesz_setup);
 
 /*
  * default_hugepagesz command line input
  * Only one instance of default_hugepagesz allowed on command line.
  */
 static int __init default_hugepagesz_setup(char *s)
 {
         unsigned long size;
         int i;
 
         parsed_valid_hugepagesz = false;
         if (parsed_default_hugepagesz) {
                 pr_err("HugeTLB: default_hugepagesz previously specified, ignoring %s\n", s);
                 return 1;
         }
 
         size = (unsigned long)memparse(s, NULL);
 
         if (!arch_hugetlb_valid_size(size)) {
                 pr_err("HugeTLB: unsupported default_hugepagesz=%s\n", s);
                 return 1;
         }
 
         hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
         parsed_valid_hugepagesz = true;
         parsed_default_hugepagesz = true;
         default_hstate_idx = hstate_index(size_to_hstate(size));
 
         /*
          * The number of default huge pages (for this size) could have been
          * specified as the first hugetlb parameter: hugepages=X.  If so,
          * then default_hstate_max_huge_pages is set.  If the default huge
          * page size is gigantic (> MAX_PAGE_ORDER), then the pages must be
          * allocated here from bootmem allocator.
          */
         if (default_hstate_max_huge_pages) {
                 default_hstate.max_huge_pages = default_hstate_max_huge_pages;
                 for_each_online_node(i)
                         default_hstate.max_huge_pages_node[i] =
                                 default_hugepages_in_node[i];
                 if (hstate_is_gigantic(&default_hstate))
                         hugetlb_hstate_alloc_pages(&default_hstate);
                 default_hstate_max_huge_pages = 0;
         }
 
         return 1;
 }
 __setup("default_hugepagesz=", default_hugepagesz_setup);
 
 static unsigned int allowed_mems_nr(struct hstate *h)
 {
         int node;
         unsigned int nr = 0;
         nodemask_t *mbind_nodemask;
         unsigned int *array = h->free_huge_pages_node;
         gfp_t gfp_mask = htlb_alloc_mask(h);
 
         mbind_nodemask = policy_mbind_nodemask(gfp_mask);
         for_each_node_mask(node, cpuset_current_mems_allowed) {
                 if (!mbind_nodemask || node_isset(node, *mbind_nodemask))
                         nr += array[node];
         }
 
         return nr;
 }
 
 #ifdef CONFIG_SYSCTL
 static int proc_hugetlb_doulongvec_minmax(const struct ctl_table *table, int write,
                                           void *buffer, size_t *length,
                                           loff_t *ppos, unsigned long *out)
 {
         struct ctl_table dup_table;
 
         /*
          * In order to avoid races with __do_proc_doulongvec_minmax(), we
          * can duplicate the @table and alter the duplicate of it.
          */
         dup_table = *table;
         dup_table.data = out;
 
         return proc_doulongvec_minmax(&dup_table, write, buffer, length, ppos);
 }
 
 static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
                          const struct ctl_table *table, int write,
                          void *buffer, size_t *length, loff_t *ppos)
 {
         struct hstate *h = &default_hstate;
         unsigned long tmp = h->max_huge_pages;
         int ret;
 
         if (!hugepages_supported())
                 return -EOPNOTSUPP;
 
         ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos,
                                              &tmp);
         if (ret)
                 goto out;
 
         if (write)
                 ret = __nr_hugepages_store_common(obey_mempolicy, h,
                                                   NUMA_NO_NODE, tmp, *length);
 out:
         return ret;
 }
 
 static int hugetlb_sysctl_handler(const struct ctl_table *table, int write,
                           void *buffer, size_t *length, loff_t *ppos)
 {
 
         return hugetlb_sysctl_handler_common(false, table, write,
                                                         buffer, length, ppos);
 }
 
 #ifdef CONFIG_NUMA
 static int hugetlb_mempolicy_sysctl_handler(const struct ctl_table *table, int write,
                           void *buffer, size_t *length, loff_t *ppos)
 {
         return hugetlb_sysctl_handler_common(true, table, write,
                                                         buffer, length, ppos);
 }
 #endif /* CONFIG_NUMA */
 
 static int hugetlb_overcommit_handler(const struct ctl_table *table, int write,
                 void *buffer, size_t *length, loff_t *ppos)
 {
         struct hstate *h = &default_hstate;
         unsigned long tmp;
         int ret;
 
         if (!hugepages_supported())
                 return -EOPNOTSUPP;
 
         tmp = h->nr_overcommit_huge_pages;
 
         if (write && hstate_is_gigantic(h))
                 return -EINVAL;
 
         ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos,
                                              &tmp);
         if (ret)
                 goto out;
 
         if (write) {
                 spin_lock_irq(&hugetlb_lock);
                 h->nr_overcommit_huge_pages = tmp;
                 spin_unlock_irq(&hugetlb_lock);
         }
 out:
         return ret;
 }
 
 static struct ctl_table hugetlb_table[] = {
         {
                 .procname       = "nr_hugepages",
                 .data           = NULL,
                 .maxlen         = sizeof(unsigned long),
                 .mode           = 0644,
                 .proc_handler   = hugetlb_sysctl_handler,
         },
 #ifdef CONFIG_NUMA
         {
                 .procname       = "nr_hugepages_mempolicy",
                 .data           = NULL,
                 .maxlen         = sizeof(unsigned long),
                 .mode           = 0644,
                 .proc_handler   = &hugetlb_mempolicy_sysctl_handler,
         },
 #endif
         {
                 .procname       = "hugetlb_shm_group",
                 .data           = &sysctl_hugetlb_shm_group,
                 .maxlen         = sizeof(gid_t),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
         },
         {
                 .procname       = "nr_overcommit_hugepages",
                 .data           = NULL,
                 .maxlen         = sizeof(unsigned long),
                 .mode           = 0644,
                 .proc_handler   = hugetlb_overcommit_handler,
         },
 };
 
 static void hugetlb_sysctl_init(void)
 {
         register_sysctl_init("vm", hugetlb_table);
 }
 #endif /* CONFIG_SYSCTL */
 
 void hugetlb_report_meminfo(struct seq_file *m)
 {
         struct hstate *h;
         unsigned long total = 0;
 
         if (!hugepages_supported())
                 return;
 
         for_each_hstate(h) {
                 unsigned long count = h->nr_huge_pages;
 
                 total += huge_page_size(h) * count;
 
                 if (h == &default_hstate)
                         seq_printf(m,
                                    "HugePages_Total:   %5lu\n"
                                    "HugePages_Free:    %5lu\n"
                                    "HugePages_Rsvd:    %5lu\n"
                                    "HugePages_Surp:    %5lu\n"
                                    "Hugepagesize:   %8lu kB\n",
                                    count,
                                    h->free_huge_pages,
                                    h->resv_huge_pages,
                                    h->surplus_huge_pages,
                                    huge_page_size(h) / SZ_1K);
         }
 
         seq_printf(m, "Hugetlb:        %8lu kB\n", total / SZ_1K);
 }
 
 int hugetlb_report_node_meminfo(char *buf, int len, int nid)
 {
         struct hstate *h = &default_hstate;
 
         if (!hugepages_supported())
                 return 0;
 
         return sysfs_emit_at(buf, len,
                              "Node %d HugePages_Total: %5u\n"
                              "Node %d HugePages_Free:  %5u\n"
                              "Node %d HugePages_Surp:  %5u\n",
                              nid, h->nr_huge_pages_node[nid],
                              nid, h->free_huge_pages_node[nid],
                              nid, h->surplus_huge_pages_node[nid]);
 }
 
 void hugetlb_show_meminfo_node(int nid)
 {
         struct hstate *h;
 
         if (!hugepages_supported())
                 return;
 
         for_each_hstate(h)
                 printk("Node %d hugepages_total=%u hugepages_free=%u hugepages_surp=%u hugepages_size=%lukB\n",
                         nid,
                         h->nr_huge_pages_node[nid],
                         h->free_huge_pages_node[nid],
                         h->surplus_huge_pages_node[nid],
                         huge_page_size(h) / SZ_1K);
 }
 
 void hugetlb_report_usage(struct seq_file *m, struct mm_struct *mm)
 {
         seq_printf(m, "HugetlbPages:\t%8lu kB\n",
                    K(atomic_long_read(&mm->hugetlb_usage)));
 }
 
 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 unsigned long hugetlb_total_pages(void)
 {
         struct hstate *h;
         unsigned long nr_total_pages = 0;
 
         for_each_hstate(h)
                 nr_total_pages += h->nr_huge_pages * pages_per_huge_page(h);
         return nr_total_pages;
 }
 
 static int hugetlb_acct_memory(struct hstate *h, long delta)
 {
         int ret = -ENOMEM;
 
         if (!delta)
                 return 0;
 
         spin_lock_irq(&hugetlb_lock);
         /*
          * When cpuset is configured, it breaks the strict hugetlb page
          * reservation as the accounting is done on a global variable. Such
          * reservation is completely rubbish in the presence of cpuset because
          * the reservation is not checked against page availability for the
          * current cpuset. Application can still potentially OOM'ed by kernel
          * with lack of free htlb page in cpuset that the task is in.
          * Attempt to enforce strict accounting with cpuset is almost
          * impossible (or too ugly) because cpuset is too fluid that
          * task or memory node can be dynamically moved between cpusets.
          *
          * The change of semantics for shared hugetlb mapping with cpuset is
          * undesirable. However, in order to preserve some of the semantics,
          * we fall back to check against current free page availability as
          * a best attempt and hopefully to minimize the impact of changing
          * semantics that cpuset has.
          *
          * Apart from cpuset, we also have memory policy mechanism that
          * also determines from which node the kernel will allocate memory
          * in a NUMA system. So similar to cpuset, we also should consider
          * the memory policy of the current task. Similar to the description
          * above.
          */
         if (delta > 0) {
                 if (gather_surplus_pages(h, delta) < 0)
                         goto out;
 
                 if (delta > allowed_mems_nr(h)) {
                         return_unused_surplus_pages(h, delta);
                         goto out;
                 }
         }
 
         ret = 0;
         if (delta < 0)
                 return_unused_surplus_pages(h, (unsigned long) -delta);
 
 out:
         spin_unlock_irq(&hugetlb_lock);
         return ret;
 }
 
 static void hugetlb_vm_op_open(struct vm_area_struct *vma)
 {
         struct resv_map *resv = vma_resv_map(vma);
 
         /*
          * HPAGE_RESV_OWNER indicates a private mapping.
          * This new VMA should share its siblings reservation map if present.
          * The VMA will only ever have a valid reservation map pointer where
          * it is being copied for another still existing VMA.  As that VMA
          * has a reference to the reservation map it cannot disappear until
          * after this open call completes.  It is therefore safe to take a
          * new reference here without additional locking.
          */
         if (resv && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
                 resv_map_dup_hugetlb_cgroup_uncharge_info(resv);
                 kref_get(&resv->refs);
         }
 
         /*
          * vma_lock structure for sharable mappings is vma specific.
          * Clear old pointer (if copied via vm_area_dup) and allocate
          * new structure.  Before clearing, make sure vma_lock is not
          * for this vma.
          */
         if (vma->vm_flags & VM_MAYSHARE) {
                 struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
 
                 if (vma_lock) {
                         if (vma_lock->vma != vma) {
                                 vma->vm_private_data = NULL;
                                 hugetlb_vma_lock_alloc(vma);
                         } else
                                 pr_warn("HugeTLB: vma_lock already exists in %s.\n", __func__);
                 } else
                         hugetlb_vma_lock_alloc(vma);
         }
 }
 
 static void hugetlb_vm_op_close(struct vm_area_struct *vma)
 {
         struct hstate *h = hstate_vma(vma);
         struct resv_map *resv;
         struct hugepage_subpool *spool = subpool_vma(vma);
         unsigned long reserve, start, end;
         long gbl_reserve;
 
         hugetlb_vma_lock_free(vma);
 
         resv = vma_resv_map(vma);
         if (!resv || !is_vma_resv_set(vma, HPAGE_RESV_OWNER))
                 return;
 
         start = vma_hugecache_offset(h, vma, vma->vm_start);
         end = vma_hugecache_offset(h, vma, vma->vm_end);
 
         reserve = (end - start) - region_count(resv, start, end);
         hugetlb_cgroup_uncharge_counter(resv, start, end);
         if (reserve) {
                 /*
                  * Decrement reserve counts.  The global reserve count may be
                  * adjusted if the subpool has a minimum size.
                  */
                 gbl_reserve = hugepage_subpool_put_pages(spool, reserve);
                 hugetlb_acct_memory(h, -gbl_reserve);
         }
 
         kref_put(&resv->refs, resv_map_release);
 }
 
 static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr)
 {
         if (addr & ~(huge_page_mask(hstate_vma(vma))))
                 return -EINVAL;
 
         /*
          * PMD sharing is only possible for PUD_SIZE-aligned address ranges
          * in HugeTLB VMAs. If we will lose PUD_SIZE alignment due to this
          * split, unshare PMDs in the PUD_SIZE interval surrounding addr now.
          */
         if (addr & ~PUD_MASK) {
                 /*
                  * hugetlb_vm_op_split is called right before we attempt to
                  * split the VMA. We will need to unshare PMDs in the old and
                  * new VMAs, so let's unshare before we split.
                  */
                 unsigned long floor = addr & PUD_MASK;
                 unsigned long ceil = floor + PUD_SIZE;
 
                 if (floor >= vma->vm_start && ceil <= vma->vm_end)
                         hugetlb_unshare_pmds(vma, floor, ceil);
         }
 
         return 0;
 }
 
 static unsigned long hugetlb_vm_op_pagesize(struct vm_area_struct *vma)
 {
         return huge_page_size(hstate_vma(vma));
 }
 
 /*
  * We cannot handle pagefaults against hugetlb pages at all.  They cause
  * handle_mm_fault() to try to instantiate regular-sized pages in the
  * hugepage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
  * this far.
  */
 static vm_fault_t hugetlb_vm_op_fault(struct vm_fault *vmf)
 {
         BUG();
         return 0;
 }
 
 /*
  * When a new function is introduced to vm_operations_struct and added
  * to hugetlb_vm_ops, please consider adding the function to shm_vm_ops.
  * This is because under System V memory model, mappings created via
  * shmget/shmat with "huge page" specified are backed by hugetlbfs files,
  * their original vm_ops are overwritten with shm_vm_ops.
  */
 const struct vm_operations_struct hugetlb_vm_ops = {
         .fault = hugetlb_vm_op_fault,
         .open = hugetlb_vm_op_open,
         .close = hugetlb_vm_op_close,
         .may_split = hugetlb_vm_op_split,
         .pagesize = hugetlb_vm_op_pagesize,
 };
 
 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
                                 int writable)
 {
         pte_t entry;
         unsigned int shift = huge_page_shift(hstate_vma(vma));
 
         if (writable) {
                 entry = huge_pte_mkwrite(huge_pte_mkdirty(mk_huge_pte(page,
                                          vma->vm_page_prot)));
         } else {
                 entry = huge_pte_wrprotect(mk_huge_pte(page,
                                            vma->vm_page_prot));
         }
         entry = pte_mkyoung(entry);
         entry = arch_make_huge_pte(entry, shift, vma->vm_flags);
 
         return entry;
 }
 
 static void set_huge_ptep_writable(struct vm_area_struct *vma,
                                    unsigned long address, pte_t *ptep)
 {
         pte_t entry;
 
         entry = huge_pte_mkwrite(huge_pte_mkdirty(huge_ptep_get(vma->vm_mm, address, ptep)));
         if (huge_ptep_set_access_flags(vma, address, ptep, entry, 1))
                 update_mmu_cache(vma, address, ptep);
 }
 
 bool is_hugetlb_entry_migration(pte_t pte)
 {
         swp_entry_t swp;
 
         if (huge_pte_none(pte) || pte_present(pte))
                 return false;
         swp = pte_to_swp_entry(pte);
         if (is_migration_entry(swp))
                 return true;
         else
                 return false;
 }
 
 bool is_hugetlb_entry_hwpoisoned(pte_t pte)
 {
         swp_entry_t swp;
 
         if (huge_pte_none(pte) || pte_present(pte))
                 return false;
         swp = pte_to_swp_entry(pte);
         if (is_hwpoison_entry(swp))
                 return true;
         else
                 return false;
 }
 
 static void
 hugetlb_install_folio(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr,
                       struct folio *new_folio, pte_t old, unsigned long sz)
 {
         pte_t newpte = make_huge_pte(vma, &new_folio->page, 1);
 
         __folio_mark_uptodate(new_folio);
         hugetlb_add_new_anon_rmap(new_folio, vma, addr);
         if (userfaultfd_wp(vma) && huge_pte_uffd_wp(old))
                 newpte = huge_pte_mkuffd_wp(newpte);
         set_huge_pte_at(vma->vm_mm, addr, ptep, newpte, sz);
         hugetlb_count_add(pages_per_huge_page(hstate_vma(vma)), vma->vm_mm);
         folio_set_hugetlb_migratable(new_folio);
 }
 
 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
                             struct vm_area_struct *dst_vma,
                             struct vm_area_struct *src_vma)
 {
         pte_t *src_pte, *dst_pte, entry;
         struct folio *pte_folio;
         unsigned long addr;
         bool cow = is_cow_mapping(src_vma->vm_flags);
         struct hstate *h = hstate_vma(src_vma);
         unsigned long sz = huge_page_size(h);
         unsigned long npages = pages_per_huge_page(h);
         struct mmu_notifier_range range;
         unsigned long last_addr_mask;
         int ret = 0;
 
         if (cow) {
                 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, src,
                                         src_vma->vm_start,
                                         src_vma->vm_end);
                 mmu_notifier_invalidate_range_start(&range);
                 vma_assert_write_locked(src_vma);
                 raw_write_seqcount_begin(&src->write_protect_seq);
         } else {
                 /*
                  * For shared mappings the vma lock must be held before
                  * calling hugetlb_walk() in the src vma. Otherwise, the
                  * returned ptep could go away if part of a shared pmd and
                  * another thread calls huge_pmd_unshare.
                  */
                 hugetlb_vma_lock_read(src_vma);
         }
 
         last_addr_mask = hugetlb_mask_last_page(h);
         for (addr = src_vma->vm_start; addr < src_vma->vm_end; addr += sz) {
                 spinlock_t *src_ptl, *dst_ptl;
                 src_pte = hugetlb_walk(src_vma, addr, sz);
                 if (!src_pte) {
                         addr |= last_addr_mask;
                         continue;
                 }
                 dst_pte = huge_pte_alloc(dst, dst_vma, addr, sz);
                 if (!dst_pte) {
                         ret = -ENOMEM;
                         break;
                 }
 
                 /*
                  * If the pagetables are shared don't copy or take references.
                  *
                  * dst_pte == src_pte is the common case of src/dest sharing.
                  * However, src could have 'unshared' and dst shares with
                  * another vma. So page_count of ptep page is checked instead
                  * to reliably determine whether pte is shared.
                  */
                 if (page_count(virt_to_page(dst_pte)) > 1) {
                         addr |= last_addr_mask;
                         continue;
                 }
 
                 dst_ptl = huge_pte_lock(h, dst, dst_pte);
                 src_ptl = huge_pte_lockptr(h, src, src_pte);
                 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
                 entry = huge_ptep_get(src_vma->vm_mm, addr, src_pte);
 again:
                 if (huge_pte_none(entry)) {
                         /*
                          * Skip if src entry none.
                          */
                         ;
                 } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) {
                         if (!userfaultfd_wp(dst_vma))
                                 entry = huge_pte_clear_uffd_wp(entry);
                         set_huge_pte_at(dst, addr, dst_pte, entry, sz);
                 } else if (unlikely(is_hugetlb_entry_migration(entry))) {
                         swp_entry_t swp_entry = pte_to_swp_entry(entry);
                         bool uffd_wp = pte_swp_uffd_wp(entry);
 
                         if (!is_readable_migration_entry(swp_entry) && cow) {
                                 /*
                                  * COW mappings require pages in both
                                  * parent and child to be set to read.
                                  */
                                 swp_entry = make_readable_migration_entry(
                                                         swp_offset(swp_entry));
                                 entry = swp_entry_to_pte(swp_entry);
                                 if (userfaultfd_wp(src_vma) && uffd_wp)
                                         entry = pte_swp_mkuffd_wp(entry);
                                 set_huge_pte_at(src, addr, src_pte, entry, sz);
                         }
                         if (!userfaultfd_wp(dst_vma))
                                 entry = huge_pte_clear_uffd_wp(entry);
                         set_huge_pte_at(dst, addr, dst_pte, entry, sz);
                 } else if (unlikely(is_pte_marker(entry))) {
                         pte_marker marker = copy_pte_marker(
                                 pte_to_swp_entry(entry), dst_vma);
 
                         if (marker)
                                 set_huge_pte_at(dst, addr, dst_pte,
                                                 make_pte_marker(marker), sz);
                 } else {
                         entry = huge_ptep_get(src_vma->vm_mm, addr, src_pte);
                         pte_folio = page_folio(pte_page(entry));
                         folio_get(pte_folio);
 
                         /*
                          * Failing to duplicate the anon rmap is a rare case
                          * where we see pinned hugetlb pages while they're
                          * prone to COW. We need to do the COW earlier during
                          * fork.
                          *
                          * When pre-allocating the page or copying data, we
                          * need to be without the pgtable locks since we could
                          * sleep during the process.
                          */
                         if (!folio_test_anon(pte_folio)) {
                                 hugetlb_add_file_rmap(pte_folio);
                         } else if (hugetlb_try_dup_anon_rmap(pte_folio, src_vma)) {
                                 pte_t src_pte_old = entry;
                                 struct folio *new_folio;
 
                                 spin_unlock(src_ptl);
                                 spin_unlock(dst_ptl);
                                 /* Do not use reserve as it's private owned */
                                 new_folio = alloc_hugetlb_folio(dst_vma, addr, 1);
                                 if (IS_ERR(new_folio)) {
                                         folio_put(pte_folio);
                                         ret = PTR_ERR(new_folio);
                                         break;
                                 }
                                 ret = copy_user_large_folio(new_folio, pte_folio,
                                                 ALIGN_DOWN(addr, sz), dst_vma);
                                 folio_put(pte_folio);
                                 if (ret) {
                                         folio_put(new_folio);
                                         break;
                                 }
 
                                 /* Install the new hugetlb folio if src pte stable */
                                 dst_ptl = huge_pte_lock(h, dst, dst_pte);
                                 src_ptl = huge_pte_lockptr(h, src, src_pte);
                                 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
                                 entry = huge_ptep_get(src_vma->vm_mm, addr, src_pte);
                                 if (!pte_same(src_pte_old, entry)) {
                                         restore_reserve_on_error(h, dst_vma, addr,
                                                                 new_folio);
                                         folio_put(new_folio);
                                         /* huge_ptep of dst_pte won't change as in child */
                                         goto again;
                                 }
                                 hugetlb_install_folio(dst_vma, dst_pte, addr,
                                                       new_folio, src_pte_old, sz);
                                 spin_unlock(src_ptl);
                                 spin_unlock(dst_ptl);
                                 continue;
                         }
 
                         if (cow) {
                                 /*
                                  * No need to notify as we are downgrading page
                                  * table protection not changing it to point
                                  * to a new page.
                                  *
                                  * See Documentation/mm/mmu_notifier.rst
                                  */
                                 huge_ptep_set_wrprotect(src, addr, src_pte);
                                 entry = huge_pte_wrprotect(entry);
                         }
 
                         if (!userfaultfd_wp(dst_vma))
                                 entry = huge_pte_clear_uffd_wp(entry);
 
                         set_huge_pte_at(dst, addr, dst_pte, entry, sz);
                         hugetlb_count_add(npages, dst);
                 }
                 spin_unlock(src_ptl);
                 spin_unlock(dst_ptl);
         }
 
         if (cow) {
                 raw_write_seqcount_end(&src->write_protect_seq);
                 mmu_notifier_invalidate_range_end(&range);
         } else {
                 hugetlb_vma_unlock_read(src_vma);
         }
 
         return ret;
 }
 
 static void move_huge_pte(struct vm_area_struct *vma, unsigned long old_addr,
                           unsigned long new_addr, pte_t *src_pte, pte_t *dst_pte,
                           unsigned long sz)
 {
         struct hstate *h = hstate_vma(vma);
         struct mm_struct *mm = vma->vm_mm;
         spinlock_t *src_ptl, *dst_ptl;
         pte_t pte;
 
         dst_ptl = huge_pte_lock(h, mm, dst_pte);
         src_ptl = huge_pte_lockptr(h, mm, src_pte);
 
         /*
          * We don't have to worry about the ordering of src and dst ptlocks
          * because exclusive mmap_lock (or the i_mmap_lock) prevents deadlock.
          */
         if (src_ptl != dst_ptl)
                 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 
         pte = huge_ptep_get_and_clear(mm, old_addr, src_pte);
         set_huge_pte_at(mm, new_addr, dst_pte, pte, sz);
 
         if (src_ptl != dst_ptl)
                 spin_unlock(src_ptl);
         spin_unlock(dst_ptl);
 }
 
 int move_hugetlb_page_tables(struct vm_area_struct *vma,
                              struct vm_area_struct *new_vma,
                              unsigned long old_addr, unsigned long new_addr,
                              unsigned long len)
 {
         struct hstate *h = hstate_vma(vma);
         struct address_space *mapping = vma->vm_file->f_mapping;
         unsigned long sz = huge_page_size(h);
         struct mm_struct *mm = vma->vm_mm;
         unsigned long old_end = old_addr + len;
         unsigned long last_addr_mask;
         pte_t *src_pte, *dst_pte;
         struct mmu_notifier_range range;
         bool shared_pmd = false;
 
         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, old_addr,
                                 old_end);
         adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
         /*
          * In case of shared PMDs, we should cover the maximum possible
          * range.
          */
         flush_cache_range(vma, range.start, range.end);
 
         mmu_notifier_invalidate_range_start(&range);
         last_addr_mask = hugetlb_mask_last_page(h);
         /* Prevent race with file truncation */
         hugetlb_vma_lock_write(vma);
         i_mmap_lock_write(mapping);
         for (; old_addr < old_end; old_addr += sz, new_addr += sz) {
                 src_pte = hugetlb_walk(vma, old_addr, sz);
                 if (!src_pte) {
                         old_addr |= last_addr_mask;
                         new_addr |= last_addr_mask;
                         continue;
                 }
                 if (huge_pte_none(huge_ptep_get(mm, old_addr, src_pte)))
                         continue;
 
                 if (huge_pmd_unshare(mm, vma, old_addr, src_pte)) {
                         shared_pmd = true;
                         old_addr |= last_addr_mask;
                         new_addr |= last_addr_mask;
                         continue;
                 }
 
                 dst_pte = huge_pte_alloc(mm, new_vma, new_addr, sz);
                 if (!dst_pte)
                         break;
 
                 move_huge_pte(vma, old_addr, new_addr, src_pte, dst_pte, sz);
         }
 
         if (shared_pmd)
                 flush_hugetlb_tlb_range(vma, range.start, range.end);
         else
                 flush_hugetlb_tlb_range(vma, old_end - len, old_end);
         mmu_notifier_invalidate_range_end(&range);
         i_mmap_unlock_write(mapping);
         hugetlb_vma_unlock_write(vma);
 
         return len + old_addr - old_end;
 }
 
 void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
                             unsigned long start, unsigned long end,
                             struct page *ref_page, zap_flags_t zap_flags)
 {
         struct mm_struct *mm = vma->vm_mm;
         unsigned long address;
         pte_t *ptep;
         pte_t pte;
         spinlock_t *ptl;
         struct page *page;
         struct hstate *h = hstate_vma(vma);
         unsigned long sz = huge_page_size(h);
         bool adjust_reservation = false;
         unsigned long last_addr_mask;
         bool force_flush = false;
 
         WARN_ON(!is_vm_hugetlb_page(vma));
         BUG_ON(start & ~huge_page_mask(h));
         BUG_ON(end & ~huge_page_mask(h));
 
         /*
          * This is a hugetlb vma, all the pte entries should point
          * to huge page.
          */
         tlb_change_page_size(tlb, sz);
         tlb_start_vma(tlb, vma);
 
         last_addr_mask = hugetlb_mask_last_page(h);
         address = start;
         for (; address < end; address += sz) {
                 ptep = hugetlb_walk(vma, address, sz);
                 if (!ptep) {
                         address |= last_addr_mask;
                         continue;
                 }
 
                 ptl = huge_pte_lock(h, mm, ptep);
                 if (huge_pmd_unshare(mm, vma, address, ptep)) {
                         spin_unlock(ptl);
                         tlb_flush_pmd_range(tlb, address & PUD_MASK, PUD_SIZE);
                         force_flush = true;
                         address |= last_addr_mask;
                         continue;
                 }
 
                 pte = huge_ptep_get(mm, address, ptep);
                 if (huge_pte_none(pte)) {
                         spin_unlock(ptl);
                         continue;
                 }
 
                 /*
                  * Migrating hugepage or HWPoisoned hugepage is already
                  * unmapped and its refcount is dropped, so just clear pte here.
                  */
                 if (unlikely(!pte_present(pte))) {
                         /*
                          * If the pte was wr-protected by uffd-wp in any of the
                          * swap forms, meanwhile the caller does not want to
                          * drop the uffd-wp bit in this zap, then replace the
                          * pte with a marker.
                          */
                         if (pte_swp_uffd_wp_any(pte) &&
                             !(zap_flags & ZAP_FLAG_DROP_MARKER))
                                 set_huge_pte_at(mm, address, ptep,
                                                 make_pte_marker(PTE_MARKER_UFFD_WP),
                                                 sz);
                         else
                                 huge_pte_clear(mm, address, ptep, sz);
                         spin_unlock(ptl);
                         continue;
                 }
 
                 page = pte_page(pte);
                 /*
                  * If a reference page is supplied, it is because a specific
                  * page is being unmapped, not a range. Ensure the page we
                  * are about to unmap is the actual page of interest.
                  */
                 if (ref_page) {
                         if (page != ref_page) {
                                 spin_unlock(ptl);
                                 continue;
                         }
                         /*
                          * Mark the VMA as having unmapped its page so that
                          * future faults in this VMA will fail rather than
                          * looking like data was lost
                          */
                         set_vma_resv_flags(vma, HPAGE_RESV_UNMAPPED);
                 }
 
                 pte = huge_ptep_get_and_clear(mm, address, ptep);
                 tlb_remove_huge_tlb_entry(h, tlb, ptep, address);
                 if (huge_pte_dirty(pte))
                         set_page_dirty(page);
                 /* Leave a uffd-wp pte marker if needed */
                 if (huge_pte_uffd_wp(pte) &&
                     !(zap_flags & ZAP_FLAG_DROP_MARKER))
                         set_huge_pte_at(mm, address, ptep,
                                         make_pte_marker(PTE_MARKER_UFFD_WP),
                                         sz);
                 hugetlb_count_sub(pages_per_huge_page(h), mm);
                 hugetlb_remove_rmap(page_folio(page));
 
                 /*
                  * Restore the reservation for anonymous page, otherwise the
                  * backing page could be stolen by someone.
                  * If there we are freeing a surplus, do not set the restore
                  * reservation bit.
                  */
                 if (!h->surplus_huge_pages && __vma_private_lock(vma) &&
                     folio_test_anon(page_folio(page))) {
                         folio_set_hugetlb_restore_reserve(page_folio(page));
                         /* Reservation to be adjusted after the spin lock */
                         adjust_reservation = true;
                 }
 
                 spin_unlock(ptl);
 
                 /*
                  * Adjust the reservation for the region that will have the
                  * reserve restored. Keep in mind that vma_needs_reservation() changes
                  * resv->adds_in_progress if it succeeds. If this is not done,
                  * do_exit() will not see it, and will keep the reservation
                  * forever.
                  */
                 if (adjust_reservation) {
                         int rc = vma_needs_reservation(h, vma, address);
 
                         if (rc < 0)
                                 /* Pressumably allocate_file_region_entries failed
                                  * to allocate a file_region struct. Clear
                                  * hugetlb_restore_reserve so that global reserve
                                  * count will not be incremented by free_huge_folio.
                                  * Act as if we consumed the reservation.
                                  */
                                 folio_clear_hugetlb_restore_reserve(page_folio(page));
                         else if (rc)
                                 vma_add_reservation(h, vma, address);
                 }
 
                 tlb_remove_page_size(tlb, page, huge_page_size(h));
                 /*
                  * Bail out after unmapping reference page if supplied
                  */
                 if (ref_page)
                         break;
         }
         tlb_end_vma(tlb, vma);
 
         /*
          * If we unshared PMDs, the TLB flush was not recorded in mmu_gather. We
          * could defer the flush until now, since by holding i_mmap_rwsem we
          * guaranteed that the last refernece would not be dropped. But we must
          * do the flushing before we return, as otherwise i_mmap_rwsem will be
          * dropped and the last reference to the shared PMDs page might be
          * dropped as well.
          *
          * In theory we could defer the freeing of the PMD pages as well, but
          * huge_pmd_unshare() relies on the exact page_count for the PMD page to
          * detect sharing, so we cannot defer the release of the page either.
          * Instead, do flush now.
          */
         if (force_flush)
                 tlb_flush_mmu_tlbonly(tlb);
 }
 
 void __hugetlb_zap_begin(struct vm_area_struct *vma,
                          unsigned long *start, unsigned long *end)
 {
         if (!vma->vm_file)      /* hugetlbfs_file_mmap error */
                 return;
 
         adjust_range_if_pmd_sharing_possible(vma, start, end);
         hugetlb_vma_lock_write(vma);
         if (vma->vm_file)
                 i_mmap_lock_write(vma->vm_file->f_mapping);
 }
 
 void __hugetlb_zap_end(struct vm_area_struct *vma,
                        struct zap_details *details)
 {
         zap_flags_t zap_flags = details ? details->zap_flags : 0;
 
         if (!vma->vm_file)      /* hugetlbfs_file_mmap error */
                 return;
 
         if (zap_flags & ZAP_FLAG_UNMAP) {       /* final unmap */
                 /*
                  * Unlock and free the vma lock before releasing i_mmap_rwsem.
                  * When the vma_lock is freed, this makes the vma ineligible
                  * for pmd sharing.  And, i_mmap_rwsem is required to set up
                  * pmd sharing.  This is important as page tables for this
                  * unmapped range will be asynchrously deleted.  If the page
                  * tables are shared, there will be issues when accessed by
                  * someone else.
                  */
                 __hugetlb_vma_unlock_write_free(vma);
         } else {
                 hugetlb_vma_unlock_write(vma);
         }
 
         if (vma->vm_file)
                 i_mmap_unlock_write(vma->vm_file->f_mapping);
 }
 
 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
                           unsigned long end, struct page *ref_page,
                           zap_flags_t zap_flags)
 {
         struct mmu_notifier_range range;
         struct mmu_gather tlb;
 
         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
                                 start, end);
         adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
         mmu_notifier_invalidate_range_start(&range);
         tlb_gather_mmu(&tlb, vma->vm_mm);
 
         __unmap_hugepage_range(&tlb, vma, start, end, ref_page, zap_flags);
 
         mmu_notifier_invalidate_range_end(&range);
         tlb_finish_mmu(&tlb);
 }
 
 /*
  * This is called when the original mapper is failing to COW a MAP_PRIVATE
  * mapping it owns the reserve page for. The intention is to unmap the page
  * from other VMAs and let the children be SIGKILLed if they are faulting the
  * same region.
  */
 static void unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
                               struct page *page, unsigned long address)
 {
         struct hstate *h = hstate_vma(vma);
         struct vm_area_struct *iter_vma;
         struct address_space *mapping;
         pgoff_t pgoff;
 
         /*
          * vm_pgoff is in PAGE_SIZE units, hence the different calculation
          * from page cache lookup which is in HPAGE_SIZE units.
          */
         address = address & huge_page_mask(h);
         pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) +
                         vma->vm_pgoff;
         mapping = vma->vm_file->f_mapping;
 
         /*
          * Take the mapping lock for the duration of the table walk. As
          * this mapping should be shared between all the VMAs,
          * __unmap_hugepage_range() is called as the lock is already held
          */
         i_mmap_lock_write(mapping);
         vma_interval_tree_foreach(iter_vma, &mapping->i_mmap, pgoff, pgoff) {
                 /* Do not unmap the current VMA */
                 if (iter_vma == vma)
                         continue;
 
                 /*
                  * Shared VMAs have their own reserves and do not affect
                  * MAP_PRIVATE accounting but it is possible that a shared
                  * VMA is using the same page so check and skip such VMAs.
                  */
                 if (iter_vma->vm_flags & VM_MAYSHARE)
                         continue;
 
                 /*
                  * Unmap the page from other VMAs without their own reserves.
                  * They get marked to be SIGKILLed if they fault in these
                  * areas. This is because a future no-page fault on this VMA
                  * could insert a zeroed page instead of the data existing
                  * from the time of fork. This would look like data corruption
                  */
                 if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER))
                         unmap_hugepage_range(iter_vma, address,
                                              address + huge_page_size(h), page, 0);
         }
         i_mmap_unlock_write(mapping);
 }
 
 /*
  * hugetlb_wp() should be called with page lock of the original hugepage held.
  * Called with hugetlb_fault_mutex_table held and pte_page locked so we
  * cannot race with other handlers or page migration.
  * Keep the pte_same checks anyway to make transition from the mutex easier.
  */
 static vm_fault_t hugetlb_wp(struct folio *pagecache_folio,
                        struct vm_fault *vmf)
 {
         struct vm_area_struct *vma = vmf->vma;
         struct mm_struct *mm = vma->vm_mm;
         const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
         pte_t pte = huge_ptep_get(mm, vmf->address, vmf->pte);
         struct hstate *h = hstate_vma(vma);
         struct folio *old_folio;
         struct folio *new_folio;
         int outside_reserve = 0;
         vm_fault_t ret = 0;
         struct mmu_notifier_range range;
 
         /*
          * Never handle CoW for uffd-wp protected pages.  It should be only
          * handled when the uffd-wp protection is removed.
          *
          * Note that only the CoW optimization path (in hugetlb_no_page())
          * can trigger this, because hugetlb_fault() will always resolve
          * uffd-wp bit first.
          */
         if (!unshare && huge_pte_uffd_wp(pte))
                 return 0;
 
         /*
          * hugetlb does not support FOLL_FORCE-style write faults that keep the
          * PTE mapped R/O such as maybe_mkwrite() would do.
          */
         if (WARN_ON_ONCE(!unshare && !(vma->vm_flags & VM_WRITE)))
                 return VM_FAULT_SIGSEGV;
 
         /* Let's take out MAP_SHARED mappings first. */
         if (vma->vm_flags & VM_MAYSHARE) {
                 set_huge_ptep_writable(vma, vmf->address, vmf->pte);
                 return 0;
         }
 
         old_folio = page_folio(pte_page(pte));
 
         delayacct_wpcopy_start();
 
 retry_avoidcopy:
         /*
          * If no-one else is actually using this page, we're the exclusive
          * owner and can reuse this page.
          *
          * Note that we don't rely on the (safer) folio refcount here, because
          * copying the hugetlb folio when there are unexpected (temporary)
          * folio references could harm simple fork()+exit() users when
          * we run out of free hugetlb folios: we would have to kill processes
          * in scenarios that used to work. As a side effect, there can still
          * be leaks between processes, for example, with FOLL_GET users.
          */
         if (folio_mapcount(old_folio) == 1 && folio_test_anon(old_folio)) {
                 if (!PageAnonExclusive(&old_folio->page)) {
                         folio_move_anon_rmap(old_folio, vma);
                         SetPageAnonExclusive(&old_folio->page);
                 }
                 if (likely(!unshare))
                         set_huge_ptep_writable(vma, vmf->address, vmf->pte);
 
                 delayacct_wpcopy_end();
                 return 0;
         }
         VM_BUG_ON_PAGE(folio_test_anon(old_folio) &&
                        PageAnonExclusive(&old_folio->page), &old_folio->page);
 
         /*
          * If the process that created a MAP_PRIVATE mapping is about to
          * perform a COW due to a shared page count, attempt to satisfy
          * the allocation without using the existing reserves. The pagecache
          * page is used to determine if the reserve at this address was
          * consumed or not. If reserves were used, a partial faulted mapping
          * at the time of fork() could consume its reserves on COW instead
          * of the full address range.
          */
         if (is_vma_resv_set(vma, HPAGE_RESV_OWNER) &&
                         old_folio != pagecache_folio)
                 outside_reserve = 1;
 
         folio_get(old_folio);
 
         /*
          * Drop page table lock as buddy allocator may be called. It will
          * be acquired again before returning to the caller, as expected.
          */
         spin_unlock(vmf->ptl);
         new_folio = alloc_hugetlb_folio(vma, vmf->address, outside_reserve);
 
         if (IS_ERR(new_folio)) {
                 /*
                  * If a process owning a MAP_PRIVATE mapping fails to COW,
                  * it is due to references held by a child and an insufficient
                  * huge page pool. To guarantee the original mappers
                  * reliability, unmap the page from child processes. The child
                  * may get SIGKILLed if it later faults.
                  */
                 if (outside_reserve) {
                         struct address_space *mapping = vma->vm_file->f_mapping;
                         pgoff_t idx;
                         u32 hash;
 
                         folio_put(old_folio);
                         /*
                          * Drop hugetlb_fault_mutex and vma_lock before
                          * unmapping.  unmapping needs to hold vma_lock
                          * in write mode.  Dropping vma_lock in read mode
                          * here is OK as COW mappings do not interact with
                          * PMD sharing.
                          *
                          * Reacquire both after unmap operation.
                          */
                         idx = vma_hugecache_offset(h, vma, vmf->address);
                         hash = hugetlb_fault_mutex_hash(mapping, idx);
                         hugetlb_vma_unlock_read(vma);
                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 
                         unmap_ref_private(mm, vma, &old_folio->page,
                                         vmf->address);
 
                         mutex_lock(&hugetlb_fault_mutex_table[hash]);
                         hugetlb_vma_lock_read(vma);
                         spin_lock(vmf->ptl);
                         vmf->pte = hugetlb_walk(vma, vmf->address,
                                         huge_page_size(h));
                         if (likely(vmf->pte &&
                                    pte_same(huge_ptep_get(mm, vmf->address, vmf->pte), pte)))
                                 goto retry_avoidcopy;
                         /*
                          * race occurs while re-acquiring page table
                          * lock, and our job is done.
                          */
                         delayacct_wpcopy_end();
                         return 0;
                 }
 
                 ret = vmf_error(PTR_ERR(new_folio));
                 goto out_release_old;
         }
 
         /*
          * When the original hugepage is shared one, it does not have
          * anon_vma prepared.
          */
         ret = __vmf_anon_prepare(vmf);
         if (unlikely(ret))
                 goto out_release_all;
 
         if (copy_user_large_folio(new_folio, old_folio, vmf->real_address, vma)) {
                 ret = VM_FAULT_HWPOISON_LARGE | VM_FAULT_SET_HINDEX(hstate_index(h));
                 goto out_release_all;
         }
         __folio_mark_uptodate(new_folio);
 
         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, vmf->address,
                                 vmf->address + huge_page_size(h));
         mmu_notifier_invalidate_range_start(&range);
 
         /*
          * Retake the page table lock to check for racing updates
          * before the page tables are altered
          */
         spin_lock(vmf->ptl);
         vmf->pte = hugetlb_walk(vma, vmf->address, huge_page_size(h));
         if (likely(vmf->pte && pte_same(huge_ptep_get(mm, vmf->address, vmf->pte), pte))) {
                 pte_t newpte = make_huge_pte(vma, &new_folio->page, !unshare);
 
                 /* Break COW or unshare */
                 huge_ptep_clear_flush(vma, vmf->address, vmf->pte);
                 hugetlb_remove_rmap(old_folio);
                 hugetlb_add_new_anon_rmap(new_folio, vma, vmf->address);
                 if (huge_pte_uffd_wp(pte))
                         newpte = huge_pte_mkuffd_wp(newpte);
                 set_huge_pte_at(mm, vmf->address, vmf->pte, newpte,
                                 huge_page_size(h));
                 folio_set_hugetlb_migratable(new_folio);
                 /* Make the old page be freed below */
                 new_folio = old_folio;
         }
         spin_unlock(vmf->ptl);
         mmu_notifier_invalidate_range_end(&range);
 out_release_all:
         /*
          * No restore in case of successful pagetable update (Break COW or
          * unshare)
          */
         if (new_folio != old_folio)
                 restore_reserve_on_error(h, vma, vmf->address, new_folio);
         folio_put(new_folio);
 out_release_old:
         folio_put(old_folio);
 
         spin_lock(vmf->ptl); /* Caller expects lock to be held */
 
         delayacct_wpcopy_end();
         return ret;
 }
 
 /*
  * Return whether there is a pagecache page to back given address within VMA.
  */
 bool hugetlbfs_pagecache_present(struct hstate *h,
                                  struct vm_area_struct *vma, unsigned long address)
 {
         struct address_space *mapping = vma->vm_file->f_mapping;
         pgoff_t idx = linear_page_index(vma, address);
         struct folio *folio;
 
         folio = filemap_get_folio(mapping, idx);
         if (IS_ERR(folio))
                 return false;
         folio_put(folio);
         return true;
 }
 
 int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping,
                            pgoff_t idx)
 {
         struct inode *inode = mapping->host;
         struct hstate *h = hstate_inode(inode);
         int err;
 
         idx <<= huge_page_order(h);
         __folio_set_locked(folio);
         err = __filemap_add_folio(mapping, folio, idx, GFP_KERNEL, NULL);
 
         if (unlikely(err)) {
                 __folio_clear_locked(folio);
                 return err;
         }
         folio_clear_hugetlb_restore_reserve(folio);
 
         /*
          * mark folio dirty so that it will not be removed from cache/file
          * by non-hugetlbfs specific code paths.
          */
         folio_mark_dirty(folio);
 
         spin_lock(&inode->i_lock);
         inode->i_blocks += blocks_per_huge_page(h);
         spin_unlock(&inode->i_lock);
         return 0;
 }
 
 static inline vm_fault_t hugetlb_handle_userfault(struct vm_fault *vmf,
                                                   struct address_space *mapping,
                                                   unsigned long reason)
 {
         u32 hash;
 
         /*
          * vma_lock and hugetlb_fault_mutex must be dropped before handling
          * userfault. Also mmap_lock could be dropped due to handling
          * userfault, any vma operation should be careful from here.
          */
         hugetlb_vma_unlock_read(vmf->vma);
         hash = hugetlb_fault_mutex_hash(mapping, vmf->pgoff);
         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
         return handle_userfault(vmf, reason);
 }
 
 /*
  * Recheck pte with pgtable lock.  Returns true if pte didn't change, or
  * false if pte changed or is changing.
  */
 static bool hugetlb_pte_stable(struct hstate *h, struct mm_struct *mm, unsigned long addr,
                                pte_t *ptep, pte_t old_pte)
 {
         spinlock_t *ptl;
         bool same;
 
         ptl = huge_pte_lock(h, mm, ptep);
         same = pte_same(huge_ptep_get(mm, addr, ptep), old_pte);
         spin_unlock(ptl);
 
         return same;
 }
 
 static vm_fault_t hugetlb_no_page(struct address_space *mapping,
                         struct vm_fault *vmf)
 {
         struct vm_area_struct *vma = vmf->vma;
         struct mm_struct *mm = vma->vm_mm;
         struct hstate *h = hstate_vma(vma);
         vm_fault_t ret = VM_FAULT_SIGBUS;
         int anon_rmap = 0;
         unsigned long size;
         struct folio *folio;
         pte_t new_pte;
         bool new_folio, new_pagecache_folio = false;
         u32 hash = hugetlb_fault_mutex_hash(mapping, vmf->pgoff);
 
         /*
          * Currently, we are forced to kill the process in the event the
          * original mapper has unmapped pages from the child due to a failed
          * COW/unsharing. Warn that such a situation has occurred as it may not
          * be obvious.
          */
         if (is_vma_resv_set(vma, HPAGE_RESV_UNMAPPED)) {
                 pr_warn_ratelimited("PID %d killed due to inadequate hugepage pool\n",
                            current->pid);
                 goto out;
         }
 
         /*
          * Use page lock to guard against racing truncation
          * before we get page_table_lock.
          */
         new_folio = false;
         folio = filemap_lock_hugetlb_folio(h, mapping, vmf->pgoff);
         if (IS_ERR(folio)) {
                 size = i_size_read(mapping->host) >> huge_page_shift(h);
                 if (vmf->pgoff >= size)
                         goto out;
                 /* Check for page in userfault range */
                 if (userfaultfd_missing(vma)) {
                         /*
                          * Since hugetlb_no_page() was examining pte
                          * without pgtable lock, we need to re-test under
                          * lock because the pte may not be stable and could
                          * have changed from under us.  Try to detect
                          * either changed or during-changing ptes and retry
                          * properly when needed.
                          *
                          * Note that userfaultfd is actually fine with
                          * false positives (e.g. caused by pte changed),
                          * but not wrong logical events (e.g. caused by
                          * reading a pte during changing).  The latter can
                          * confuse the userspace, so the strictness is very
                          * much preferred.  E.g., MISSING event should
                          * never happen on the page after UFFDIO_COPY has
                          * correctly installed the page and returned.
                          */
                         if (!hugetlb_pte_stable(h, mm, vmf->address, vmf->pte, vmf->orig_pte)) {
                                 ret = 0;
                                 goto out;
                         }
 
                         return hugetlb_handle_userfault(vmf, mapping,
                                                         VM_UFFD_MISSING);
                 }
 
                 if (!(vma->vm_flags & VM_MAYSHARE)) {
                         ret = __vmf_anon_prepare(vmf);
                         if (unlikely(ret))
                                 goto out;
                 }
 
                 folio = alloc_hugetlb_folio(vma, vmf->address, 0);
                 if (IS_ERR(folio)) {
                         /*
                          * Returning error will result in faulting task being
                          * sent SIGBUS.  The hugetlb fault mutex prevents two
                          * tasks from racing to fault in the same page which
                          * could result in false unable to allocate errors.
                          * Page migration does not take the fault mutex, but
                          * does a clear then write of pte's under page table
                          * lock.  Page fault code could race with migration,
                          * notice the clear pte and try to allocate a page
                          * here.  Before returning error, get ptl and make
                          * sure there really is no pte entry.
                          */
                         if (hugetlb_pte_stable(h, mm, vmf->address, vmf->pte, vmf->orig_pte))
                                 ret = vmf_error(PTR_ERR(folio));
                         else
                                 ret = 0;
                         goto out;
                 }
                 folio_zero_user(folio, vmf->real_address);
                 __folio_mark_uptodate(folio);
                 new_folio = true;
 
                 if (vma->vm_flags & VM_MAYSHARE) {
                         int err = hugetlb_add_to_page_cache(folio, mapping,
                                                         vmf->pgoff);
                         if (err) {
                                 /*
                                  * err can't be -EEXIST which implies someone
                                  * else consumed the reservation since hugetlb
                                  * fault mutex is held when add a hugetlb page
                                  * to the page cache. So it's safe to call
                                  * restore_reserve_on_error() here.
                                  */
                                 restore_reserve_on_error(h, vma, vmf->address,
                                                         folio);
                                 folio_put(folio);
                                 ret = VM_FAULT_SIGBUS;
                                 goto out;
                         }
                         new_pagecache_folio = true;
                 } else {
                         folio_lock(folio);
                         anon_rmap = 1;
                 }
         } else {
                 /*
                  * If memory error occurs between mmap() and fault, some process
                  * don't have hwpoisoned swap entry for errored virtual address.
                  * So we need to block hugepage fault by PG_hwpoison bit check.
                  */
                 if (unlikely(folio_test_hwpoison(folio))) {
                         ret = VM_FAULT_HWPOISON_LARGE |
                                 VM_FAULT_SET_HINDEX(hstate_index(h));
                         goto backout_unlocked;
                 }
 
                 /* Check for page in userfault range. */
                 if (userfaultfd_minor(vma)) {
                         folio_unlock(folio);
                         folio_put(folio);
                         /* See comment in userfaultfd_missing() block above */
                         if (!hugetlb_pte_stable(h, mm, vmf->address, vmf->pte, vmf->orig_pte)) {
                                 ret = 0;
                                 goto out;
                         }
                         return hugetlb_handle_userfault(vmf, mapping,
                                                         VM_UFFD_MINOR);
                 }
         }
 
         /*
          * If we are going to COW a private mapping later, we examine the
          * pending reservations for this page now. This will ensure that
          * any allocations necessary to record that reservation occur outside
          * the spinlock.
          */
         if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
                 if (vma_needs_reservation(h, vma, vmf->address) < 0) {
                         ret = VM_FAULT_OOM;
                         goto backout_unlocked;
                 }
                 /* Just decrements count, does not deallocate */
                 vma_end_reservation(h, vma, vmf->address);
         }
 
         vmf->ptl = huge_pte_lock(h, mm, vmf->pte);
         ret = 0;
         /* If pte changed from under us, retry */
         if (!pte_same(huge_ptep_get(mm, vmf->address, vmf->pte), vmf->orig_pte))
                 goto backout;
 
         if (anon_rmap)
                 hugetlb_add_new_anon_rmap(folio, vma, vmf->address);
         else
                 hugetlb_add_file_rmap(folio);
         new_pte = make_huge_pte(vma, &folio->page, ((vma->vm_flags & VM_WRITE)
                                 && (vma->vm_flags & VM_SHARED)));
         /*
          * If this pte was previously wr-protected, keep it wr-protected even
          * if populated.
          */
         if (unlikely(pte_marker_uffd_wp(vmf->orig_pte)))
                 new_pte = huge_pte_mkuffd_wp(new_pte);
         set_huge_pte_at(mm, vmf->address, vmf->pte, new_pte, huge_page_size(h));
 
         hugetlb_count_add(pages_per_huge_page(h), mm);
         if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
                 /* Optimization, do the COW without a second fault */
                 ret = hugetlb_wp(folio, vmf);
         }
 
         spin_unlock(vmf->ptl);
 
         /*
          * Only set hugetlb_migratable in newly allocated pages.  Existing pages
          * found in the pagecache may not have hugetlb_migratable if they have
          * been isolated for migration.
          */
         if (new_folio)
                 folio_set_hugetlb_migratable(folio);
 
         folio_unlock(folio);
 out:
         hugetlb_vma_unlock_read(vma);
 
         /*
          * We must check to release the per-VMA lock. __vmf_anon_prepare() is
          * the only way ret can be set to VM_FAULT_RETRY.
          */
         if (unlikely(ret & VM_FAULT_RETRY))
                 vma_end_read(vma);
 
         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
         return ret;
 
 backout:
         spin_unlock(vmf->ptl);
 backout_unlocked:
         if (new_folio && !new_pagecache_folio)
                 restore_reserve_on_error(h, vma, vmf->address, folio);
 
         folio_unlock(folio);
         folio_put(folio);
         goto out;
 }
 
 #ifdef CONFIG_SMP
 u32 hugetlb_fault_mutex_hash(struct address_space *mapping, pgoff_t idx)
 {
         unsigned long key[2];
         u32 hash;
 
         key[0] = (unsigned long) mapping;
         key[1] = idx;
 
         hash = jhash2((u32 *)&key, sizeof(key)/(sizeof(u32)), 0);
 
         return hash & (num_fault_mutexes - 1);
 }
 #else
 /*
  * For uniprocessor systems we always use a single mutex, so just
  * return 0 and avoid the hashing overhead.
  */
 u32 hugetlb_fault_mutex_hash(struct address_space *mapping, pgoff_t idx)
 {
         return 0;
 }
 #endif
 
 vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                         unsigned long address, unsigned int flags)
 {
         vm_fault_t ret;
         u32 hash;
         struct folio *folio = NULL;
         struct folio *pagecache_folio = NULL;
         struct hstate *h = hstate_vma(vma);
         struct address_space *mapping;
         int need_wait_lock = 0;
         struct vm_fault vmf = {
                 .vma = vma,
                 .address = address & huge_page_mask(h),
                 .real_address = address,
                 .flags = flags,
                 .pgoff = vma_hugecache_offset(h, vma,
                                 address & huge_page_mask(h)),
                 /* TODO: Track hugetlb faults using vm_fault */
 
                 /*
                  * Some fields may not be initialized, be careful as it may
                  * be hard to debug if called functions make assumptions
                  */
         };
 
         /*
          * Serialize hugepage allocation and instantiation, so that we don't
          * get spurious allocation failures if two CPUs race to instantiate
          * the same page in the page cache.
          */
         mapping = vma->vm_file->f_mapping;
         hash = hugetlb_fault_mutex_hash(mapping, vmf.pgoff);
         mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
         /*
          * Acquire vma lock before calling huge_pte_alloc and hold
          * until finished with vmf.pte.  This prevents huge_pmd_unshare from
          * being called elsewhere and making the vmf.pte no longer valid.
          */
         hugetlb_vma_lock_read(vma);
         vmf.pte = huge_pte_alloc(mm, vma, vmf.address, huge_page_size(h));
         if (!vmf.pte) {
                 hugetlb_vma_unlock_read(vma);
                 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
                 return VM_FAULT_OOM;
         }
 
         vmf.orig_pte = huge_ptep_get(mm, vmf.address, vmf.pte);
         if (huge_pte_none_mostly(vmf.orig_pte)) {
                 if (is_pte_marker(vmf.orig_pte)) {
                         pte_marker marker =
                                 pte_marker_get(pte_to_swp_entry(vmf.orig_pte));
 
                         if (marker & PTE_MARKER_POISONED) {
                                 ret = VM_FAULT_HWPOISON_LARGE |
                                       VM_FAULT_SET_HINDEX(hstate_index(h));
                                 goto out_mutex;
                         }
                 }
 
                 /*
                  * Other PTE markers should be handled the same way as none PTE.
                  *
                  * hugetlb_no_page will drop vma lock and hugetlb fault
                  * mutex internally, which make us return immediately.
                  */
                 return hugetlb_no_page(mapping, &vmf);
         }
 
         ret = 0;
 
         /*
          * vmf.orig_pte could be a migration/hwpoison vmf.orig_pte at this
          * point, so this check prevents the kernel from going below assuming
          * that we have an active hugepage in pagecache. This goto expects
          * the 2nd page fault, and is_hugetlb_entry_(migration|hwpoisoned)
          * check will properly handle it.
          */
         if (!pte_present(vmf.orig_pte)) {
                 if (unlikely(is_hugetlb_entry_migration(vmf.orig_pte))) {
                         /*
                          * Release the hugetlb fault lock now, but retain
                          * the vma lock, because it is needed to guard the
                          * huge_pte_lockptr() later in
                          * migration_entry_wait_huge(). The vma lock will
                          * be released there.
                          */
                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
                         migration_entry_wait_huge(vma, vmf.address, vmf.pte);
                         return 0;
                 } else if (unlikely(is_hugetlb_entry_hwpoisoned(vmf.orig_pte)))
                         ret = VM_FAULT_HWPOISON_LARGE |
                             VM_FAULT_SET_HINDEX(hstate_index(h));
                 goto out_mutex;
         }
 
         /*
          * If we are going to COW/unshare the mapping later, we examine the
          * pending reservations for this page now. This will ensure that any
          * allocations necessary to record that reservation occur outside the
          * spinlock. Also lookup the pagecache page now as it is used to
          * determine if a reservation has been consumed.
          */
         if ((flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) &&
             !(vma->vm_flags & VM_MAYSHARE) && !huge_pte_write(vmf.orig_pte)) {
                 if (vma_needs_reservation(h, vma, vmf.address) < 0) {
                         ret = VM_FAULT_OOM;
                         goto out_mutex;
                 }
                 /* Just decrements count, does not deallocate */
                 vma_end_reservation(h, vma, vmf.address);
 
                 pagecache_folio = filemap_lock_hugetlb_folio(h, mapping,
                                                              vmf.pgoff);
                 if (IS_ERR(pagecache_folio))
                         pagecache_folio = NULL;
         }
 
         vmf.ptl = huge_pte_lock(h, mm, vmf.pte);
 
         /* Check for a racing update before calling hugetlb_wp() */
         if (unlikely(!pte_same(vmf.orig_pte, huge_ptep_get(mm, vmf.address, vmf.pte))))
                 goto out_ptl;
 
         /* Handle userfault-wp first, before trying to lock more pages */
         if (userfaultfd_wp(vma) && huge_pte_uffd_wp(huge_ptep_get(mm, vmf.address, vmf.pte)) &&
             (flags & FAULT_FLAG_WRITE) && !huge_pte_write(vmf.orig_pte)) {
                 if (!userfaultfd_wp_async(vma)) {
                         spin_unlock(vmf.ptl);
                         if (pagecache_folio) {
                                 folio_unlock(pagecache_folio);
                                 folio_put(pagecache_folio);
                         }
                         hugetlb_vma_unlock_read(vma);
                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
                         return handle_userfault(&vmf, VM_UFFD_WP);
                 }
 
                 vmf.orig_pte = huge_pte_clear_uffd_wp(vmf.orig_pte);
                 set_huge_pte_at(mm, vmf.address, vmf.pte, vmf.orig_pte,
                                 huge_page_size(hstate_vma(vma)));
                 /* Fallthrough to CoW */
         }
 
         /*
          * hugetlb_wp() requires page locks of pte_page(vmf.orig_pte) and
          * pagecache_folio, so here we need take the former one
          * when folio != pagecache_folio or !pagecache_folio.
          */
         folio = page_folio(pte_page(vmf.orig_pte));
         if (folio != pagecache_folio)
                 if (!folio_trylock(folio)) {
                         need_wait_lock = 1;
                         goto out_ptl;
                 }
 
         folio_get(folio);
 
         if (flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) {
                 if (!huge_pte_write(vmf.orig_pte)) {
                         ret = hugetlb_wp(pagecache_folio, &vmf);
                         goto out_put_page;
                 } else if (likely(flags & FAULT_FLAG_WRITE)) {
                         vmf.orig_pte = huge_pte_mkdirty(vmf.orig_pte);
                 }
         }
         vmf.orig_pte = pte_mkyoung(vmf.orig_pte);
         if (huge_ptep_set_access_flags(vma, vmf.address, vmf.pte, vmf.orig_pte,
                                                 flags & FAULT_FLAG_WRITE))
                 update_mmu_cache(vma, vmf.address, vmf.pte);
 out_put_page:
         if (folio != pagecache_folio)
                 folio_unlock(folio);
         folio_put(folio);
 out_ptl:
         spin_unlock(vmf.ptl);
 
         if (pagecache_folio) {
                 folio_unlock(pagecache_folio);
                 folio_put(pagecache_folio);
         }
 out_mutex:
         hugetlb_vma_unlock_read(vma);
 
         /*
          * We must check to release the per-VMA lock. __vmf_anon_prepare() in
          * hugetlb_wp() is the only way ret can be set to VM_FAULT_RETRY.
          */
         if (unlikely(ret & VM_FAULT_RETRY))
                 vma_end_read(vma);
 
         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
         /*
          * Generally it's safe to hold refcount during waiting page lock. But
          * here we just wait to defer the next page fault to avoid busy loop and
          * the page is not used after unlocked before returning from the current
          * page fault. So we are safe from accessing freed page, even if we wait
          * here without taking refcount.
          */
         if (need_wait_lock)
                 folio_wait_locked(folio);
         return ret;
 }
 
 #ifdef CONFIG_USERFAULTFD
 /*
  * Can probably be eliminated, but still used by hugetlb_mfill_atomic_pte().
  */
 static struct folio *alloc_hugetlb_folio_vma(struct hstate *h,
                 struct vm_area_struct *vma, unsigned long address)
 {
         struct mempolicy *mpol;
         nodemask_t *nodemask;
         struct folio *folio;
         gfp_t gfp_mask;
         int node;
 
         gfp_mask = htlb_alloc_mask(h);
         node = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
         /*
          * This is used to allocate a temporary hugetlb to hold the copied
          * content, which will then be copied again to the final hugetlb
          * consuming a reservation. Set the alloc_fallback to false to indicate
          * that breaking the per-node hugetlb pool is not allowed in this case.
          */
         folio = alloc_hugetlb_folio_nodemask(h, node, nodemask, gfp_mask, false);
         mpol_cond_put(mpol);
 
         return folio;
 }
 
 /*
  * Used by userfaultfd UFFDIO_* ioctls. Based on userfaultfd's mfill_atomic_pte
  * with modifications for hugetlb pages.
  */
 int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
                              struct vm_area_struct *dst_vma,
                              unsigned long dst_addr,
                              unsigned long src_addr,
                              uffd_flags_t flags,
                              struct folio **foliop)
 {
         struct mm_struct *dst_mm = dst_vma->vm_mm;
         bool is_continue = uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE);
         bool wp_enabled = (flags & MFILL_ATOMIC_WP);
         struct hstate *h = hstate_vma(dst_vma);
         struct address_space *mapping = dst_vma->vm_file->f_mapping;
         pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
         unsigned long size = huge_page_size(h);
         int vm_shared = dst_vma->vm_flags & VM_SHARED;
         pte_t _dst_pte;
         spinlock_t *ptl;
         int ret = -ENOMEM;
         struct folio *folio;
         int writable;
         bool folio_in_pagecache = false;
 
         if (uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) {
                 ptl = huge_pte_lock(h, dst_mm, dst_pte);
 
                 /* Don't overwrite any existing PTEs (even markers) */
                 if (!huge_pte_none(huge_ptep_get(dst_mm, dst_addr, dst_pte))) {
                         spin_unlock(ptl);
                         return -EEXIST;
                 }
 
                 _dst_pte = make_pte_marker(PTE_MARKER_POISONED);
                 set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte, size);
 
                 /* No need to invalidate - it was non-present before */
                 update_mmu_cache(dst_vma, dst_addr, dst_pte);
 
                 spin_unlock(ptl);
                 return 0;
         }
 
         if (is_continue) {
                 ret = -EFAULT;
                 folio = filemap_lock_hugetlb_folio(h, mapping, idx);
                 if (IS_ERR(folio))
                         goto out;
                 folio_in_pagecache = true;
         } else if (!*foliop) {
                 /* If a folio already exists, then it's UFFDIO_COPY for
                  * a non-missing case. Return -EEXIST.
                  */
                 if (vm_shared &&
                     hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) {
                         ret = -EEXIST;
                         goto out;
                 }
 
                 folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0);
                 if (IS_ERR(folio)) {
                         ret = -ENOMEM;
                         goto out;
                 }
 
                 ret = copy_folio_from_user(folio, (const void __user *) src_addr,
                                            false);
 
                 /* fallback to copy_from_user outside mmap_lock */
                 if (unlikely(ret)) {
                         ret = -ENOENT;
                         /* Free the allocated folio which may have
                          * consumed a reservation.
                          */
                         restore_reserve_on_error(h, dst_vma, dst_addr, folio);
                         folio_put(folio);
 
                         /* Allocate a temporary folio to hold the copied
                          * contents.
                          */
                         folio = alloc_hugetlb_folio_vma(h, dst_vma, dst_addr);
                         if (!folio) {
                                 ret = -ENOMEM;
                                 goto out;
                         }
                         *foliop = folio;
                         /* Set the outparam foliop and return to the caller to
                          * copy the contents outside the lock. Don't free the
                          * folio.
                          */
                         goto out;
                 }
         } else {
                 if (vm_shared &&
                     hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) {
                         folio_put(*foliop);
                         ret = -EEXIST;
                         *foliop = NULL;
                         goto out;
                 }
 
                 folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0);
                 if (IS_ERR(folio)) {
                         folio_put(*foliop);
                         ret = -ENOMEM;
                         *foliop = NULL;
                         goto out;
                 }
                 ret = copy_user_large_folio(folio, *foliop,
                                             ALIGN_DOWN(dst_addr, size), dst_vma);
                 folio_put(*foliop);
                 *foliop = NULL;
                 if (ret) {
                         folio_put(folio);
                         goto out;
                 }
         }
 
         /*
          * If we just allocated a new page, we need a memory barrier to ensure
          * that preceding stores to the page become visible before the
          * set_pte_at() write. The memory barrier inside __folio_mark_uptodate
          * is what we need.
          *
          * In the case where we have not allocated a new page (is_continue),
          * the page must already be uptodate. UFFDIO_CONTINUE already includes
          * an earlier smp_wmb() to ensure that prior stores will be visible
          * before the set_pte_at() write.
          */
         if (!is_continue)
                 __folio_mark_uptodate(folio);
         else
                 WARN_ON_ONCE(!folio_test_uptodate(folio));
 
         /* Add shared, newly allocated pages to the page cache. */
         if (vm_shared && !is_continue) {
                 ret = -EFAULT;
                 if (idx >= (i_size_read(mapping->host) >> huge_page_shift(h)))
                         goto out_release_nounlock;
 
                 /*
                  * Serialization between remove_inode_hugepages() and
                  * hugetlb_add_to_page_cache() below happens through the
                  * hugetlb_fault_mutex_table that here must be hold by
                  * the caller.
                  */
                 ret = hugetlb_add_to_page_cache(folio, mapping, idx);
                 if (ret)
                         goto out_release_nounlock;
                 folio_in_pagecache = true;
         }
 
         ptl = huge_pte_lock(h, dst_mm, dst_pte);
 
         ret = -EIO;
         if (folio_test_hwpoison(folio))
                 goto out_release_unlock;
 
         /*
          * We allow to overwrite a pte marker: consider when both MISSING|WP
          * registered, we firstly wr-protect a none pte which has no page cache
          * page backing it, then access the page.
          */
         ret = -EEXIST;
         if (!huge_pte_none_mostly(huge_ptep_get(dst_mm, dst_addr, dst_pte)))
                 goto out_release_unlock;
 
         if (folio_in_pagecache)
                 hugetlb_add_file_rmap(folio);
         else
                 hugetlb_add_new_anon_rmap(folio, dst_vma, dst_addr);
 
         /*
          * For either: (1) CONTINUE on a non-shared VMA, or (2) UFFDIO_COPY
          * with wp flag set, don't set pte write bit.
          */
         if (wp_enabled || (is_continue && !vm_shared))
                 writable = 0;
         else
                 writable = dst_vma->vm_flags & VM_WRITE;
 
         _dst_pte = make_huge_pte(dst_vma, &folio->page, writable);
         /*
          * Always mark UFFDIO_COPY page dirty; note that this may not be
          * extremely important for hugetlbfs for now since swapping is not
          * supported, but we should still be clear in that this page cannot be
          * thrown away at will, even if write bit not set.
          */
         _dst_pte = huge_pte_mkdirty(_dst_pte);
         _dst_pte = pte_mkyoung(_dst_pte);
 
         if (wp_enabled)
                 _dst_pte = huge_pte_mkuffd_wp(_dst_pte);
 
         set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte, size);
 
         hugetlb_count_add(pages_per_huge_page(h), dst_mm);
 
         /* No need to invalidate - it was non-present before */
         update_mmu_cache(dst_vma, dst_addr, dst_pte);
 
         spin_unlock(ptl);
         if (!is_continue)
                 folio_set_hugetlb_migratable(folio);
         if (vm_shared || is_continue)
                 folio_unlock(folio);
         ret = 0;
 out:
         return ret;
 out_release_unlock:
         spin_unlock(ptl);
         if (vm_shared || is_continue)
                 folio_unlock(folio);
 out_release_nounlock:
         if (!folio_in_pagecache)
                 restore_reserve_on_error(h, dst_vma, dst_addr, folio);
         folio_put(folio);
         goto out;
 }
 #endif /* CONFIG_USERFAULTFD */
 
 long hugetlb_change_protection(struct vm_area_struct *vma,
                 unsigned long address, unsigned long end,
                 pgprot_t newprot, unsigned long cp_flags)
 {
         struct mm_struct *mm = vma->vm_mm;
         unsigned long start = address;
         pte_t *ptep;
         pte_t pte;
         struct hstate *h = hstate_vma(vma);
         long pages = 0, psize = huge_page_size(h);
         bool shared_pmd = false;
         struct mmu_notifier_range range;
         unsigned long last_addr_mask;
         bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
         bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
 
         /*
          * In the case of shared PMDs, the area to flush could be beyond
          * start/end.  Set range.start/range.end to cover the maximum possible
          * range if PMD sharing is possible.
          */
         mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA,
                                 0, mm, start, end);
         adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
 
         BUG_ON(address >= end);
         flush_cache_range(vma, range.start, range.end);
 
         mmu_notifier_invalidate_range_start(&range);
         hugetlb_vma_lock_write(vma);
         i_mmap_lock_write(vma->vm_file->f_mapping);
         last_addr_mask = hugetlb_mask_last_page(h);
         for (; address < end; address += psize) {
                 spinlock_t *ptl;
                 ptep = hugetlb_walk(vma, address, psize);
                 if (!ptep) {
                         if (!uffd_wp) {
                                 address |= last_addr_mask;
                                 continue;
                         }
                         /*
                          * Userfaultfd wr-protect requires pgtable
                          * pre-allocations to install pte markers.
                          */
                         ptep = huge_pte_alloc(mm, vma, address, psize);
                         if (!ptep) {
                                 pages = -ENOMEM;
                                 break;
                         }
                 }
                 ptl = huge_pte_lock(h, mm, ptep);
                 if (huge_pmd_unshare(mm, vma, address, ptep)) {
                         /*
                          * When uffd-wp is enabled on the vma, unshare
                          * shouldn't happen at all.  Warn about it if it
                          * happened due to some reason.
                          */
                         WARN_ON_ONCE(uffd_wp || uffd_wp_resolve);
                         pages++;
                         spin_unlock(ptl);
                         shared_pmd = true;
                         address |= last_addr_mask;
                         continue;
                 }
                 pte = huge_ptep_get(mm, address, ptep);
                 if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
                         /* Nothing to do. */
                 } else if (unlikely(is_hugetlb_entry_migration(pte))) {
                         swp_entry_t entry = pte_to_swp_entry(pte);
                         struct page *page = pfn_swap_entry_to_page(entry);
                         pte_t newpte = pte;
 
                         if (is_writable_migration_entry(entry)) {
                                 if (PageAnon(page))
                                         entry = make_readable_exclusive_migration_entry(
                                                                 swp_offset(entry));
                                 else
                                         entry = make_readable_migration_entry(
                                                                 swp_offset(entry));
                                 newpte = swp_entry_to_pte(entry);
                                 pages++;
                         }
 
                         if (uffd_wp)
                                 newpte = pte_swp_mkuffd_wp(newpte);
                         else if (uffd_wp_resolve)
                                 newpte = pte_swp_clear_uffd_wp(newpte);
                         if (!pte_same(pte, newpte))
                                 set_huge_pte_at(mm, address, ptep, newpte, psize);
                 } else if (unlikely(is_pte_marker(pte))) {
                         /*
                          * Do nothing on a poison marker; page is
                          * corrupted, permissons do not apply.  Here
                          * pte_marker_uffd_wp()==true implies !poison
                          * because they're mutual exclusive.
                          */
                         if (pte_marker_uffd_wp(pte) && uffd_wp_resolve)
                                 /* Safe to modify directly (non-present->none). */
                                 huge_pte_clear(mm, address, ptep, psize);
                 } else if (!huge_pte_none(pte)) {
                         pte_t old_pte;
                         unsigned int shift = huge_page_shift(hstate_vma(vma));
 
                         old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
                         pte = huge_pte_modify(old_pte, newprot);
                         pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
                         if (uffd_wp)
                                 pte = huge_pte_mkuffd_wp(pte);
                         else if (uffd_wp_resolve)
                                 pte = huge_pte_clear_uffd_wp(pte);
                         huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
                         pages++;
                 } else {
                         /* None pte */
                         if (unlikely(uffd_wp))
                                 /* Safe to modify directly (none->non-present). */
                                 set_huge_pte_at(mm, address, ptep,
                                                 make_pte_marker(PTE_MARKER_UFFD_WP),
                                                 psize);
                 }
                 spin_unlock(ptl);
         }
         /*
          * Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare
          * may have cleared our pud entry and done put_page on the page table:
          * once we release i_mmap_rwsem, another task can do the final put_page
          * and that page table be reused and filled with junk.  If we actually
          * did unshare a page of pmds, flush the range corresponding to the pud.
          */
         if (shared_pmd)
                 flush_hugetlb_tlb_range(vma, range.start, range.end);
         else
                 flush_hugetlb_tlb_range(vma, start, end);
         /*
          * No need to call mmu_notifier_arch_invalidate_secondary_tlbs() we are
          * downgrading page table protection not changing it to point to a new
          * page.
          *
          * See Documentation/mm/mmu_notifier.rst
          */
         i_mmap_unlock_write(vma->vm_file->f_mapping);
         hugetlb_vma_unlock_write(vma);
         mmu_notifier_invalidate_range_end(&range);
 
         return pages > 0 ? (pages << h->order) : pages;
 }
 
 /* Return true if reservation was successful, false otherwise.  */
 bool hugetlb_reserve_pages(struct inode *inode,
                                         long from, long to,
                                         struct vm_area_struct *vma,
                                         vm_flags_t vm_flags)
 {
         long chg = -1, add = -1;
         struct hstate *h = hstate_inode(inode);
         struct hugepage_subpool *spool = subpool_inode(inode);
         struct resv_map *resv_map;
         struct hugetlb_cgroup *h_cg = NULL;
         long gbl_reserve, regions_needed = 0;
 
         /* This should never happen */
         if (from > to) {
                 VM_WARN(1, "%s called with a negative range\n", __func__);
                 return false;
         }
 
         /*
          * vma specific semaphore used for pmd sharing and fault/truncation
          * synchronization
          */
         hugetlb_vma_lock_alloc(vma);
 
         /*
          * Only apply hugepage reservation if asked. At fault time, an
          * attempt will be made for VM_NORESERVE to allocate a page
          * without using reserves
          */
         if (vm_flags & VM_NORESERVE)
                 return true;
 
         /*
          * Shared mappings base their reservation on the number of pages that
          * are already allocated on behalf of the file. Private mappings need
          * to reserve the full area even if read-only as mprotect() may be
          * called to make the mapping read-write. Assume !vma is a shm mapping
          */
         if (!vma || vma->vm_flags & VM_MAYSHARE) {
                 /*
                  * resv_map can not be NULL as hugetlb_reserve_pages is only
                  * called for inodes for which resv_maps were created (see
                  * hugetlbfs_get_inode).
                  */
                 resv_map = inode_resv_map(inode);
 
                 chg = region_chg(resv_map, from, to, &regions_needed);
         } else {
                 /* Private mapping. */
                 resv_map = resv_map_alloc();
                 if (!resv_map)
                         goto out_err;
 
                 chg = to - from;
 
                 set_vma_resv_map(vma, resv_map);
                 set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
         }
 
         if (chg < 0)
                 goto out_err;
 
         if (hugetlb_cgroup_charge_cgroup_rsvd(hstate_index(h),
                                 chg * pages_per_huge_page(h), &h_cg) < 0)
                 goto out_err;
 
         if (vma && !(vma->vm_flags & VM_MAYSHARE) && h_cg) {
                 /* For private mappings, the hugetlb_cgroup uncharge info hangs
                  * of the resv_map.
                  */
                 resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, h_cg, h);
         }
 
         /*
          * There must be enough pages in the subpool for the mapping. If
          * the subpool has a minimum size, there may be some global
          * reservations already in place (gbl_reserve).
          */
         gbl_reserve = hugepage_subpool_get_pages(spool, chg);
         if (gbl_reserve < 0)
                 goto out_uncharge_cgroup;
 
         /*
          * Check enough hugepages are available for the reservation.
          * Hand the pages back to the subpool if there are not
          */
         if (hugetlb_acct_memory(h, gbl_reserve) < 0)
                 goto out_put_pages;
 
         /*
          * Account for the reservations made. Shared mappings record regions
          * that have reservations as they are shared by multiple VMAs.
          * When the last VMA disappears, the region map says how much
          * the reservation was and the page cache tells how much of
          * the reservation was consumed. Private mappings are per-VMA and
          * only the consumed reservations are tracked. When the VMA
          * disappears, the original reservation is the VMA size and the
          * consumed reservations are stored in the map. Hence, nothing
          * else has to be done for private mappings here
          */
         if (!vma || vma->vm_flags & VM_MAYSHARE) {
                 add = region_add(resv_map, from, to, regions_needed, h, h_cg);
 
                 if (unlikely(add < 0)) {
                         hugetlb_acct_memory(h, -gbl_reserve);
                         goto out_put_pages;
                 } else if (unlikely(chg > add)) {
                         /*
                          * pages in this range were added to the reserve
                          * map between region_chg and region_add.  This
                          * indicates a race with alloc_hugetlb_folio.  Adjust
                          * the subpool and reserve counts modified above
                          * based on the difference.
                          */
                         long rsv_adjust;
 
                         /*
                          * hugetlb_cgroup_uncharge_cgroup_rsvd() will put the
                          * reference to h_cg->css. See comment below for detail.
                          */
                         hugetlb_cgroup_uncharge_cgroup_rsvd(
                                 hstate_index(h),
                                 (chg - add) * pages_per_huge_page(h), h_cg);
 
                         rsv_adjust = hugepage_subpool_put_pages(spool,
                                                                 chg - add);
                         hugetlb_acct_memory(h, -rsv_adjust);
                 } else if (h_cg) {
                         /*
                          * The file_regions will hold their own reference to
                          * h_cg->css. So we should release the reference held
                          * via hugetlb_cgroup_charge_cgroup_rsvd() when we are
                          * done.
                          */
                         hugetlb_cgroup_put_rsvd_cgroup(h_cg);
                 }
         }
         return true;
 
 out_put_pages:
         /* put back original number of pages, chg */
         (void)hugepage_subpool_put_pages(spool, chg);
 out_uncharge_cgroup:
         hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h),
                                             chg * pages_per_huge_page(h), h_cg);
 out_err:
         hugetlb_vma_lock_free(vma);
         if (!vma || vma->vm_flags & VM_MAYSHARE)
                 /* Only call region_abort if the region_chg succeeded but the
                  * region_add failed or didn't run.
                  */
                 if (chg >= 0 && add < 0)
                         region_abort(resv_map, from, to, regions_needed);
         if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
                 kref_put(&resv_map->refs, resv_map_release);
                 set_vma_resv_map(vma, NULL);
         }
         return false;
 }
 
 long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
                                                                 long freed)
 {
         struct hstate *h = hstate_inode(inode);
         struct resv_map *resv_map = inode_resv_map(inode);
         long chg = 0;
         struct hugepage_subpool *spool = subpool_inode(inode);
         long gbl_reserve;
 
         /*
          * Since this routine can be called in the evict inode path for all
          * hugetlbfs inodes, resv_map could be NULL.
          */
         if (resv_map) {
                 chg = region_del(resv_map, start, end);
                 /*
                  * region_del() can fail in the rare case where a region
                  * must be split and another region descriptor can not be
                  * allocated.  If end == LONG_MAX, it will not fail.
                  */
                 if (chg < 0)
                         return chg;
         }
 
         spin_lock(&inode->i_lock);
         inode->i_blocks -= (blocks_per_huge_page(h) * freed);
         spin_unlock(&inode->i_lock);
 
         /*
          * If the subpool has a minimum size, the number of global
          * reservations to be released may be adjusted.
          *
          * Note that !resv_map implies freed == 0. So (chg - freed)
          * won't go negative.
          */
         gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed));
         hugetlb_acct_memory(h, -gbl_reserve);
 
         return 0;
 }
 
 #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
 static unsigned long page_table_shareable(struct vm_area_struct *svma,
                                 struct vm_area_struct *vma,
                                 unsigned long addr, pgoff_t idx)
 {
         unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
                                 svma->vm_start;
         unsigned long sbase = saddr & PUD_MASK;
         unsigned long s_end = sbase + PUD_SIZE;
 
         /* Allow segments to share if only one is marked locked */
         unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED_MASK;
         unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED_MASK;
 
         /*
          * match the virtual addresses, permission and the alignment of the
          * page table page.
          *
          * Also, vma_lock (vm_private_data) is required for sharing.
          */
         if (pmd_index(addr) != pmd_index(saddr) ||
             vm_flags != svm_flags ||
             !range_in_vma(svma, sbase, s_end) ||
             !svma->vm_private_data)
                 return 0;
 
         return saddr;
 }
 
 bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
 {
         unsigned long start = addr & PUD_MASK;
         unsigned long end = start + PUD_SIZE;
 
 #ifdef CONFIG_USERFAULTFD
         if (uffd_disable_huge_pmd_share(vma))
                 return false;
 #endif
         /*
          * check on proper vm_flags and page table alignment
          */
         if (!(vma->vm_flags & VM_MAYSHARE))
                 return false;
         if (!vma->vm_private_data)      /* vma lock required for sharing */
                 return false;
         if (!range_in_vma(vma, start, end))
                 return false;
         return true;
 }
 
 /*
  * Determine if start,end range within vma could be mapped by shared pmd.
  * If yes, adjust start and end to cover range associated with possible
  * shared pmd mappings.
  */
 void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
                                 unsigned long *start, unsigned long *end)
 {
         unsigned long v_start = ALIGN(vma->vm_start, PUD_SIZE),
                 v_end = ALIGN_DOWN(vma->vm_end, PUD_SIZE);
 
         /*
          * vma needs to span at least one aligned PUD size, and the range
          * must be at least partially within in.
          */
         if (!(vma->vm_flags & VM_MAYSHARE) || !(v_end > v_start) ||
                 (*end <= v_start) || (*start >= v_end))
                 return;
 
         /* Extend the range to be PUD aligned for a worst case scenario */
         if (*start > v_start)
                 *start = ALIGN_DOWN(*start, PUD_SIZE);
 
         if (*end < v_end)
                 *end = ALIGN(*end, PUD_SIZE);
 }
 
 /*
  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
  * and returns the corresponding pte. While this is not necessary for the
  * !shared pmd case because we can allocate the pmd later as well, it makes the
  * code much cleaner. pmd allocation is essential for the shared case because
  * pud has to be populated inside the same i_mmap_rwsem section - otherwise
  * racing tasks could either miss the sharing (see huge_pte_offset) or select a
  * bad pmd for sharing.
  */
 pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
                       unsigned long addr, pud_t *pud)
 {
         struct address_space *mapping = vma->vm_file->f_mapping;
         pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
                         vma->vm_pgoff;
         struct vm_area_struct *svma;
         unsigned long saddr;
         pte_t *spte = NULL;
         pte_t *pte;
 
         i_mmap_lock_read(mapping);
         vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
                 if (svma == vma)
                         continue;
 
                 saddr = page_table_shareable(svma, vma, addr, idx);
                 if (saddr) {
                         spte = hugetlb_walk(svma, saddr,
                                             vma_mmu_pagesize(svma));
                         if (spte) {
                                 get_page(virt_to_page(spte));
                                 break;
                         }
                 }
         }
 
         if (!spte)
                 goto out;
 
         spin_lock(&mm->page_table_lock);
         if (pud_none(*pud)) {
                 pud_populate(mm, pud,
                                 (pmd_t *)((unsigned long)spte & PAGE_MASK));
                 mm_inc_nr_pmds(mm);
         } else {
                 put_page(virt_to_page(spte));
         }
         spin_unlock(&mm->page_table_lock);
 out:
         pte = (pte_t *)pmd_alloc(mm, pud, addr);
         i_mmap_unlock_read(mapping);
         return pte;
 }
 
 /*
  * unmap huge page backed by shared pte.
  *
  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
  * indicated by page_count > 1, unmap is achieved by clearing pud and
  * decrementing the ref count. If count == 1, the pte page is not shared.
  *
  * Called with page table lock held.
  *
  * returns: 1 successfully unmapped a shared pte page
  *          0 the underlying pte page is not shared, or it is the last user
  */
 int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
                                         unsigned long addr, pte_t *ptep)
 {
         pgd_t *pgd = pgd_offset(mm, addr);
         p4d_t *p4d = p4d_offset(pgd, addr);
         pud_t *pud = pud_offset(p4d, addr);
 
         i_mmap_assert_write_locked(vma->vm_file->f_mapping);
         hugetlb_vma_assert_locked(vma);
         BUG_ON(page_count(virt_to_page(ptep)) == 0);
         if (page_count(virt_to_page(ptep)) == 1)
                 return 0;
 
         pud_clear(pud);
         put_page(virt_to_page(ptep));
         mm_dec_nr_pmds(mm);
         return 1;
 }
 
 #else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
 
 pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
                       unsigned long addr, pud_t *pud)
 {
         return NULL;
 }
 
 int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
                                 unsigned long addr, pte_t *ptep)
 {
         return 0;
 }
 
 void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
                                 unsigned long *start, unsigned long *end)
 {
 }
 
 bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
 {
         return false;
 }
 #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
 
 #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB
 pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
                         unsigned long addr, unsigned long sz)
 {
         pgd_t *pgd;
         p4d_t *p4d;
         pud_t *pud;
         pte_t *pte = NULL;
 
         pgd = pgd_offset(mm, addr);
         p4d = p4d_alloc(mm, pgd, addr);
         if (!p4d)
                 return NULL;
         pud = pud_alloc(mm, p4d, addr);
         if (pud) {
                 if (sz == PUD_SIZE) {
                         pte = (pte_t *)pud;
                 } else {
                         BUG_ON(sz != PMD_SIZE);
                         if (want_pmd_share(vma, addr) && pud_none(*pud))
                                 pte = huge_pmd_share(mm, vma, addr, pud);
                         else
                                 pte = (pte_t *)pmd_alloc(mm, pud, addr);
                 }
         }
 
         if (pte) {
                 pte_t pteval = ptep_get_lockless(pte);
 
                 BUG_ON(pte_present(pteval) && !pte_huge(pteval));
         }
 
         return pte;
 }
 
 /*
  * huge_pte_offset() - Walk the page table to resolve the hugepage
  * entry at address @addr
  *
  * Return: Pointer to page table entry (PUD or PMD) for
  * address @addr, or NULL if a !p*d_present() entry is encountered and the
  * size @sz doesn't match the hugepage size at this level of the page
  * table.
  */
 pte_t *huge_pte_offset(struct mm_struct *mm,
                        unsigned long addr, unsigned long sz)
 {
         pgd_t *pgd;
         p4d_t *p4d;
         pud_t *pud;
         pmd_t *pmd;
 
         pgd = pgd_offset(mm, addr);
         if (!pgd_present(*pgd))
                 return NULL;
         p4d = p4d_offset(pgd, addr);
         if (!p4d_present(*p4d))
                 return NULL;
 
         pud = pud_offset(p4d, addr);
         if (sz == PUD_SIZE)
                 /* must be pud huge, non-present or none */
                 return (pte_t *)pud;
         if (!pud_present(*pud))
                 return NULL;
         /* must have a valid entry and size to go further */
 
         pmd = pmd_offset(pud, addr);
         /* must be pmd huge, non-present or none */
         return (pte_t *)pmd;
 }
 
 /*
  * Return a mask that can be used to update an address to the last huge
  * page in a page table page mapping size.  Used to skip non-present
  * page table entries when linearly scanning address ranges.  Architectures
  * with unique huge page to page table relationships can define their own
  * version of this routine.
  */
 unsigned long hugetlb_mask_last_page(struct hstate *h)
 {
         unsigned long hp_size = huge_page_size(h);
 
         if (hp_size == PUD_SIZE)
                 return P4D_SIZE - PUD_SIZE;
         else if (hp_size == PMD_SIZE)
                 return PUD_SIZE - PMD_SIZE;
         else
                 return 0UL;
 }
 
 #else
 
 /* See description above.  Architectures can provide their own version. */
 __weak unsigned long hugetlb_mask_last_page(struct hstate *h)
 {
 #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
         if (huge_page_size(h) == PMD_SIZE)
                 return PUD_SIZE - PMD_SIZE;
 #endif
         return 0UL;
 }
 
 #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
 
 /*
  * These functions are overwritable if your architecture needs its own
  * behavior.
  */
 bool isolate_hugetlb(struct folio *folio, struct list_head *list)
 {
         bool ret = true;
 
         spin_lock_irq(&hugetlb_lock);
         if (!folio_test_hugetlb(folio) ||
             !folio_test_hugetlb_migratable(folio) ||
             !folio_try_get(folio)) {
                 ret = false;
                 goto unlock;
         }
         folio_clear_hugetlb_migratable(folio);
         list_move_tail(&folio->lru, list);
 unlock:
         spin_unlock_irq(&hugetlb_lock);
         return ret;
 }
 
 int get_hwpoison_hugetlb_folio(struct folio *folio, bool *hugetlb, bool unpoison)
 {
         int ret = 0;
 
         *hugetlb = false;
         spin_lock_irq(&hugetlb_lock);
         if (folio_test_hugetlb(folio)) {
                 *hugetlb = true;
                 if (folio_test_hugetlb_freed(folio))
                         ret = 0;
                 else if (folio_test_hugetlb_migratable(folio) || unpoison)
                         ret = folio_try_get(folio);
                 else
                         ret = -EBUSY;
         }
         spin_unlock_irq(&hugetlb_lock);
         return ret;
 }
 
 int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
                                 bool *migratable_cleared)
 {
         int ret;
 
         spin_lock_irq(&hugetlb_lock);
         ret = __get_huge_page_for_hwpoison(pfn, flags, migratable_cleared);
         spin_unlock_irq(&hugetlb_lock);
         return ret;
 }
 
 void folio_putback_active_hugetlb(struct folio *folio)
 {
         spin_lock_irq(&hugetlb_lock);
         folio_set_hugetlb_migratable(folio);
         list_move_tail(&folio->lru, &(folio_hstate(folio))->hugepage_activelist);
         spin_unlock_irq(&hugetlb_lock);
         folio_put(folio);
 }
 
 void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int reason)
 {
         struct hstate *h = folio_hstate(old_folio);
 
         hugetlb_cgroup_migrate(old_folio, new_folio);
         set_page_owner_migrate_reason(&new_folio->page, reason);
 
         /*
          * transfer temporary state of the new hugetlb folio. This is
          * reverse to other transitions because the newpage is going to
          * be final while the old one will be freed so it takes over
          * the temporary status.
          *
          * Also note that we have to transfer the per-node surplus state
          * here as well otherwise the global surplus count will not match
          * the per-node's.
          */
         if (folio_test_hugetlb_temporary(new_folio)) {
                 int old_nid = folio_nid(old_folio);
                 int new_nid = folio_nid(new_folio);
 
                 folio_set_hugetlb_temporary(old_folio);
                 folio_clear_hugetlb_temporary(new_folio);
 
 
                 /*
                  * There is no need to transfer the per-node surplus state
                  * when we do not cross the node.
                  */
                 if (new_nid == old_nid)
                         return;
                 spin_lock_irq(&hugetlb_lock);
                 if (h->surplus_huge_pages_node[old_nid]) {
                         h->surplus_huge_pages_node[old_nid]--;
                         h->surplus_huge_pages_node[new_nid]++;
                 }
                 spin_unlock_irq(&hugetlb_lock);
         }
 }
 
 static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
                                    unsigned long start,
                                    unsigned long end)
 {
         struct hstate *h = hstate_vma(vma);
         unsigned long sz = huge_page_size(h);
         struct mm_struct *mm = vma->vm_mm;
         struct mmu_notifier_range range;
         unsigned long address;
         spinlock_t *ptl;
         pte_t *ptep;
 
         if (!(vma->vm_flags & VM_MAYSHARE))
                 return;
 
         if (start >= end)
                 return;
 
         flush_cache_range(vma, start, end);
         /*
          * No need to call adjust_range_if_pmd_sharing_possible(), because
          * we have already done the PUD_SIZE alignment.
          */
         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
                                 start, end);
         mmu_notifier_invalidate_range_start(&range);
         hugetlb_vma_lock_write(vma);
         i_mmap_lock_write(vma->vm_file->f_mapping);
         for (address = start; address < end; address += PUD_SIZE) {
                 ptep = hugetlb_walk(vma, address, sz);
                 if (!ptep)
                         continue;
                 ptl = huge_pte_lock(h, mm, ptep);
                 huge_pmd_unshare(mm, vma, address, ptep);
                 spin_unlock(ptl);
         }
         flush_hugetlb_tlb_range(vma, start, end);
         i_mmap_unlock_write(vma->vm_file->f_mapping);
         hugetlb_vma_unlock_write(vma);
         /*
          * No need to call mmu_notifier_arch_invalidate_secondary_tlbs(), see
          * Documentation/mm/mmu_notifier.rst.
          */
         mmu_notifier_invalidate_range_end(&range);
 }
 
 /*
  * This function will unconditionally remove all the shared pmd pgtable entries
  * within the specific vma for a hugetlbfs memory range.
  */
 void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
 {
         hugetlb_unshare_pmds(vma, ALIGN(vma->vm_start, PUD_SIZE),
                         ALIGN_DOWN(vma->vm_end, PUD_SIZE));
 }
 
 #ifdef CONFIG_CMA
 static bool cma_reserve_called __initdata;
 
 static int __init cmdline_parse_hugetlb_cma(char *p)
 {
         int nid, count = 0;
         unsigned long tmp;
         char *s = p;
 
         while (*s) {
                 if (sscanf(s, "%lu%n", &tmp, &count) != 1)
                         break;
 
                 if (s[count] == ':') {
                         if (tmp >= MAX_NUMNODES)
                                 break;
                         nid = array_index_nospec(tmp, MAX_NUMNODES);
 
                         s += count + 1;
                         tmp = memparse(s, &s);
                         hugetlb_cma_size_in_node[nid] = tmp;
                         hugetlb_cma_size += tmp;
 
                         /*
                          * Skip the separator if have one, otherwise
                          * break the parsing.
                          */
                         if (*s == ',')
                                 s++;
                         else
                                 break;
                 } else {
                         hugetlb_cma_size = memparse(p, &p);
                         break;
                 }
         }
 
         return 0;
 }
 
 early_param("hugetlb_cma", cmdline_parse_hugetlb_cma);
 
 void __init hugetlb_cma_reserve(int order)
 {
         unsigned long size, reserved, per_node;
         bool node_specific_cma_alloc = false;
         int nid;
 
         /*
          * HugeTLB CMA reservation is required for gigantic
          * huge pages which could not be allocated via the
          * page allocator. Just warn if there is any change
          * breaking this assumption.
          */
         VM_WARN_ON(order <= MAX_PAGE_ORDER);
         cma_reserve_called = true;
 
         if (!hugetlb_cma_size)
                 return;
 
         for (nid = 0; nid < MAX_NUMNODES; nid++) {
                 if (hugetlb_cma_size_in_node[nid] == 0)
                         continue;
 
                 if (!node_online(nid)) {
                         pr_warn("hugetlb_cma: invalid node %d specified\n", nid);
                         hugetlb_cma_size -= hugetlb_cma_size_in_node[nid];
                         hugetlb_cma_size_in_node[nid] = 0;
                         continue;
                 }
 
                 if (hugetlb_cma_size_in_node[nid] < (PAGE_SIZE << order)) {
                         pr_warn("hugetlb_cma: cma area of node %d should be at least %lu MiB\n",
                                 nid, (PAGE_SIZE << order) / SZ_1M);
                         hugetlb_cma_size -= hugetlb_cma_size_in_node[nid];
                         hugetlb_cma_size_in_node[nid] = 0;
                 } else {
                         node_specific_cma_alloc = true;
                 }
         }
 
         /* Validate the CMA size again in case some invalid nodes specified. */
         if (!hugetlb_cma_size)
                 return;
 
         if (hugetlb_cma_size < (PAGE_SIZE << order)) {
                 pr_warn("hugetlb_cma: cma area should be at least %lu MiB\n",
                         (PAGE_SIZE << order) / SZ_1M);
                 hugetlb_cma_size = 0;
                 return;
         }
 
         if (!node_specific_cma_alloc) {
                 /*
                  * If 3 GB area is requested on a machine with 4 numa nodes,
                  * let's allocate 1 GB on first three nodes and ignore the last one.
                  */
                 per_node = DIV_ROUND_UP(hugetlb_cma_size, nr_online_nodes);
                 pr_info("hugetlb_cma: reserve %lu MiB, up to %lu MiB per node\n",
                         hugetlb_cma_size / SZ_1M, per_node / SZ_1M);
         }
 
         reserved = 0;
         for_each_online_node(nid) {
                 int res;
                 char name[CMA_MAX_NAME];
 
                 if (node_specific_cma_alloc) {
                         if (hugetlb_cma_size_in_node[nid] == 0)
                                 continue;
 
                         size = hugetlb_cma_size_in_node[nid];
                 } else {
                         size = min(per_node, hugetlb_cma_size - reserved);
                 }
 
                 size = round_up(size, PAGE_SIZE << order);
 
                 snprintf(name, sizeof(name), "hugetlb%d", nid);
                 /*
                  * Note that 'order per bit' is based on smallest size that
                  * may be returned to CMA allocator in the case of
                  * huge page demotion.
                  */
                 res = cma_declare_contiguous_nid(0, size, 0,
                                         PAGE_SIZE << order,
                                         HUGETLB_PAGE_ORDER, false, name,
                                         &hugetlb_cma[nid], nid);
                 if (res) {
                         pr_warn("hugetlb_cma: reservation failed: err %d, node %d",
                                 res, nid);
                         continue;
                 }
 
                 reserved += size;
                 pr_info("hugetlb_cma: reserved %lu MiB on node %d\n",
                         size / SZ_1M, nid);
 
                 if (reserved >= hugetlb_cma_size)
                         break;
         }
 
         if (!reserved)
                 /*
                  * hugetlb_cma_size is used to determine if allocations from
                  * cma are possible.  Set to zero if no cma regions are set up.
                  */
                 hugetlb_cma_size = 0;
 }
 
 static void __init hugetlb_cma_check(void)
 {
         if (!hugetlb_cma_size || cma_reserve_called)
                 return;
 
         pr_warn("hugetlb_cma: the option isn't supported by current arch\n");
 }
 
 #endif /* CONFIG_CMA */