TOMOYO Linux Cross Reference
Linux/mm/rmap.c

   /*
    * mm/rmap.c - physical to virtual reverse mappings
    *
    * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
    * Released under the General Public License (GPL).
    *
    * Simple, low overhead reverse mapping scheme.
    * Please try to keep this thing as modular as possible.
    *
   * Provides methods for unmapping each kind of mapped page:
   * the anon methods track anonymous pages, and
   * the file methods track pages belonging to an inode.
   *
   * Original design by Rik van Riel <riel@conectiva.com.br> 2001
   * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
   * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
   * Contributions by Hugh Dickins 2003, 2004
   */
  
  /*
   * Lock ordering in mm:
   *
   * inode->i_rwsem       (while writing or truncating, not reading or faulting)
   *   mm->mmap_lock
   *     mapping->invalidate_lock (in filemap_fault)
   *       folio_lock
   *         hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below)
   *           vma_start_write
   *             mapping->i_mmap_rwsem
   *               anon_vma->rwsem
   *                 mm->page_table_lock or pte_lock
   *                   swap_lock (in swap_duplicate, swap_info_get)
   *                     mmlist_lock (in mmput, drain_mmlist and others)
   *                     mapping->private_lock (in block_dirty_folio)
   *                       folio_lock_memcg move_lock (in block_dirty_folio)
   *                         i_pages lock (widely used)
   *                           lruvec->lru_lock (in folio_lruvec_lock_irq)
   *                     inode->i_lock (in set_page_dirty's __mark_inode_dirty)
   *                     bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
   *                       sb_lock (within inode_lock in fs/fs-writeback.c)
   *                       i_pages lock (widely used, in set_page_dirty,
   *                                 in arch-dependent flush_dcache_mmap_lock,
   *                                 within bdi.wb->list_lock in __sync_single_inode)
   *
   * anon_vma->rwsem,mapping->i_mmap_rwsem   (memory_failure, collect_procs_anon)
   *   ->tasklist_lock
   *     pte map lock
   *
   * hugetlbfs PageHuge() take locks in this order:
   *   hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
   *     vma_lock (hugetlb specific lock for pmd_sharing)
   *       mapping->i_mmap_rwsem (also used for hugetlb pmd sharing)
   *         folio_lock
   */
  
  #include <linux/mm.h>
  #include <linux/sched/mm.h>
  #include <linux/sched/task.h>
  #include <linux/pagemap.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/slab.h>
  #include <linux/init.h>
  #include <linux/ksm.h>
  #include <linux/rmap.h>
  #include <linux/rcupdate.h>
  #include <linux/export.h>
  #include <linux/memcontrol.h>
  #include <linux/mmu_notifier.h>
  #include <linux/migrate.h>
  #include <linux/hugetlb.h>
  #include <linux/huge_mm.h>
  #include <linux/backing-dev.h>
  #include <linux/page_idle.h>
  #include <linux/memremap.h>
  #include <linux/userfaultfd_k.h>
  #include <linux/mm_inline.h>
  
  #include <asm/tlbflush.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/tlb.h>
  #include <trace/events/migrate.h>
  
  #include "internal.h"
  
  static struct kmem_cache *anon_vma_cachep;
  static struct kmem_cache *anon_vma_chain_cachep;
  
  static inline struct anon_vma *anon_vma_alloc(void)
  {
          struct anon_vma *anon_vma;
  
          anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
          if (anon_vma) {
                  atomic_set(&anon_vma->refcount, 1);
                  anon_vma->num_children = 0;
                  anon_vma->num_active_vmas = 0;
                  anon_vma->parent = anon_vma;
                 /*
                  * Initialise the anon_vma root to point to itself. If called
                  * from fork, the root will be reset to the parents anon_vma.
                  */
                 anon_vma->root = anon_vma;
         }
 
         return anon_vma;
 }
 
 static inline void anon_vma_free(struct anon_vma *anon_vma)
 {
         VM_BUG_ON(atomic_read(&anon_vma->refcount));
 
         /*
          * Synchronize against folio_lock_anon_vma_read() such that
          * we can safely hold the lock without the anon_vma getting
          * freed.
          *
          * Relies on the full mb implied by the atomic_dec_and_test() from
          * put_anon_vma() against the acquire barrier implied by
          * down_read_trylock() from folio_lock_anon_vma_read(). This orders:
          *
          * folio_lock_anon_vma_read()   VS      put_anon_vma()
          *   down_read_trylock()                  atomic_dec_and_test()
          *   LOCK                                 MB
          *   atomic_read()                        rwsem_is_locked()
          *
          * LOCK should suffice since the actual taking of the lock must
          * happen _before_ what follows.
          */
         might_sleep();
         if (rwsem_is_locked(&anon_vma->root->rwsem)) {
                 anon_vma_lock_write(anon_vma);
                 anon_vma_unlock_write(anon_vma);
         }
 
         kmem_cache_free(anon_vma_cachep, anon_vma);
 }
 
 static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
 {
         return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
 }
 
 static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
 {
         kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
 }
 
 static void anon_vma_chain_link(struct vm_area_struct *vma,
                                 struct anon_vma_chain *avc,
                                 struct anon_vma *anon_vma)
 {
         avc->vma = vma;
         avc->anon_vma = anon_vma;
         list_add(&avc->same_vma, &vma->anon_vma_chain);
         anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
 }
 
 /**
  * __anon_vma_prepare - attach an anon_vma to a memory region
  * @vma: the memory region in question
  *
  * This makes sure the memory mapping described by 'vma' has
  * an 'anon_vma' attached to it, so that we can associate the
  * anonymous pages mapped into it with that anon_vma.
  *
  * The common case will be that we already have one, which
  * is handled inline by anon_vma_prepare(). But if
  * not we either need to find an adjacent mapping that we
  * can re-use the anon_vma from (very common when the only
  * reason for splitting a vma has been mprotect()), or we
  * allocate a new one.
  *
  * Anon-vma allocations are very subtle, because we may have
  * optimistically looked up an anon_vma in folio_lock_anon_vma_read()
  * and that may actually touch the rwsem even in the newly
  * allocated vma (it depends on RCU to make sure that the
  * anon_vma isn't actually destroyed).
  *
  * As a result, we need to do proper anon_vma locking even
  * for the new allocation. At the same time, we do not want
  * to do any locking for the common case of already having
  * an anon_vma.
  */
 int __anon_vma_prepare(struct vm_area_struct *vma)
 {
         struct mm_struct *mm = vma->vm_mm;
         struct anon_vma *anon_vma, *allocated;
         struct anon_vma_chain *avc;
 
         mmap_assert_locked(mm);
         might_sleep();
 
         avc = anon_vma_chain_alloc(GFP_KERNEL);
         if (!avc)
                 goto out_enomem;
 
         anon_vma = find_mergeable_anon_vma(vma);
         allocated = NULL;
         if (!anon_vma) {
                 anon_vma = anon_vma_alloc();
                 if (unlikely(!anon_vma))
                         goto out_enomem_free_avc;
                 anon_vma->num_children++; /* self-parent link for new root */
                 allocated = anon_vma;
         }
 
         anon_vma_lock_write(anon_vma);
         /* page_table_lock to protect against threads */
         spin_lock(&mm->page_table_lock);
         if (likely(!vma->anon_vma)) {
                 vma->anon_vma = anon_vma;
                 anon_vma_chain_link(vma, avc, anon_vma);
                 anon_vma->num_active_vmas++;
                 allocated = NULL;
                 avc = NULL;
         }
         spin_unlock(&mm->page_table_lock);
         anon_vma_unlock_write(anon_vma);
 
         if (unlikely(allocated))
                 put_anon_vma(allocated);
         if (unlikely(avc))
                 anon_vma_chain_free(avc);
 
         return 0;
 
  out_enomem_free_avc:
         anon_vma_chain_free(avc);
  out_enomem:
         return -ENOMEM;
 }
 
 /*
  * This is a useful helper function for locking the anon_vma root as
  * we traverse the vma->anon_vma_chain, looping over anon_vma's that
  * have the same vma.
  *
  * Such anon_vma's should have the same root, so you'd expect to see
  * just a single mutex_lock for the whole traversal.
  */
 static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
 {
         struct anon_vma *new_root = anon_vma->root;
         if (new_root != root) {
                 if (WARN_ON_ONCE(root))
                         up_write(&root->rwsem);
                 root = new_root;
                 down_write(&root->rwsem);
         }
         return root;
 }
 
 static inline void unlock_anon_vma_root(struct anon_vma *root)
 {
         if (root)
                 up_write(&root->rwsem);
 }
 
 /*
  * Attach the anon_vmas from src to dst.
  * Returns 0 on success, -ENOMEM on failure.
  *
  * anon_vma_clone() is called by vma_expand(), vma_merge(), __split_vma(),
  * copy_vma() and anon_vma_fork(). The first four want an exact copy of src,
  * while the last one, anon_vma_fork(), may try to reuse an existing anon_vma to
  * prevent endless growth of anon_vma. Since dst->anon_vma is set to NULL before
  * call, we can identify this case by checking (!dst->anon_vma &&
  * src->anon_vma).
  *
  * If (!dst->anon_vma && src->anon_vma) is true, this function tries to find
  * and reuse existing anon_vma which has no vmas and only one child anon_vma.
  * This prevents degradation of anon_vma hierarchy to endless linear chain in
  * case of constantly forking task. On the other hand, an anon_vma with more
  * than one child isn't reused even if there was no alive vma, thus rmap
  * walker has a good chance of avoiding scanning the whole hierarchy when it
  * searches where page is mapped.
  */
 int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
 {
         struct anon_vma_chain *avc, *pavc;
         struct anon_vma *root = NULL;
 
         list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
                 struct anon_vma *anon_vma;
 
                 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
                 if (unlikely(!avc)) {
                         unlock_anon_vma_root(root);
                         root = NULL;
                         avc = anon_vma_chain_alloc(GFP_KERNEL);
                         if (!avc)
                                 goto enomem_failure;
                 }
                 anon_vma = pavc->anon_vma;
                 root = lock_anon_vma_root(root, anon_vma);
                 anon_vma_chain_link(dst, avc, anon_vma);
 
                 /*
                  * Reuse existing anon_vma if it has no vma and only one
                  * anon_vma child.
                  *
                  * Root anon_vma is never reused:
                  * it has self-parent reference and at least one child.
                  */
                 if (!dst->anon_vma && src->anon_vma &&
                     anon_vma->num_children < 2 &&
                     anon_vma->num_active_vmas == 0)
                         dst->anon_vma = anon_vma;
         }
         if (dst->anon_vma)
                 dst->anon_vma->num_active_vmas++;
         unlock_anon_vma_root(root);
         return 0;
 
  enomem_failure:
         /*
          * dst->anon_vma is dropped here otherwise its num_active_vmas can
          * be incorrectly decremented in unlink_anon_vmas().
          * We can safely do this because callers of anon_vma_clone() don't care
          * about dst->anon_vma if anon_vma_clone() failed.
          */
         dst->anon_vma = NULL;
         unlink_anon_vmas(dst);
         return -ENOMEM;
 }
 
 /*
  * Attach vma to its own anon_vma, as well as to the anon_vmas that
  * the corresponding VMA in the parent process is attached to.
  * Returns 0 on success, non-zero on failure.
  */
 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
 {
         struct anon_vma_chain *avc;
         struct anon_vma *anon_vma;
         int error;
 
         /* Don't bother if the parent process has no anon_vma here. */
         if (!pvma->anon_vma)
                 return 0;
 
         /* Drop inherited anon_vma, we'll reuse existing or allocate new. */
         vma->anon_vma = NULL;
 
         /*
          * First, attach the new VMA to the parent VMA's anon_vmas,
          * so rmap can find non-COWed pages in child processes.
          */
         error = anon_vma_clone(vma, pvma);
         if (error)
                 return error;
 
         /* An existing anon_vma has been reused, all done then. */
         if (vma->anon_vma)
                 return 0;
 
         /* Then add our own anon_vma. */
         anon_vma = anon_vma_alloc();
         if (!anon_vma)
                 goto out_error;
         anon_vma->num_active_vmas++;
         avc = anon_vma_chain_alloc(GFP_KERNEL);
         if (!avc)
                 goto out_error_free_anon_vma;
 
         /*
          * The root anon_vma's rwsem is the lock actually used when we
          * lock any of the anon_vmas in this anon_vma tree.
          */
         anon_vma->root = pvma->anon_vma->root;
         anon_vma->parent = pvma->anon_vma;
         /*
          * With refcounts, an anon_vma can stay around longer than the
          * process it belongs to. The root anon_vma needs to be pinned until
          * this anon_vma is freed, because the lock lives in the root.
          */
         get_anon_vma(anon_vma->root);
         /* Mark this anon_vma as the one where our new (COWed) pages go. */
         vma->anon_vma = anon_vma;
         anon_vma_lock_write(anon_vma);
         anon_vma_chain_link(vma, avc, anon_vma);
         anon_vma->parent->num_children++;
         anon_vma_unlock_write(anon_vma);
 
         return 0;
 
  out_error_free_anon_vma:
         put_anon_vma(anon_vma);
  out_error:
         unlink_anon_vmas(vma);
         return -ENOMEM;
 }
 
 void unlink_anon_vmas(struct vm_area_struct *vma)
 {
         struct anon_vma_chain *avc, *next;
         struct anon_vma *root = NULL;
 
         /*
          * Unlink each anon_vma chained to the VMA.  This list is ordered
          * from newest to oldest, ensuring the root anon_vma gets freed last.
          */
         list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
                 struct anon_vma *anon_vma = avc->anon_vma;
 
                 root = lock_anon_vma_root(root, anon_vma);
                 anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
 
                 /*
                  * Leave empty anon_vmas on the list - we'll need
                  * to free them outside the lock.
                  */
                 if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
                         anon_vma->parent->num_children--;
                         continue;
                 }
 
                 list_del(&avc->same_vma);
                 anon_vma_chain_free(avc);
         }
         if (vma->anon_vma) {
                 vma->anon_vma->num_active_vmas--;
 
                 /*
                  * vma would still be needed after unlink, and anon_vma will be prepared
                  * when handle fault.
                  */
                 vma->anon_vma = NULL;
         }
         unlock_anon_vma_root(root);
 
         /*
          * Iterate the list once more, it now only contains empty and unlinked
          * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
          * needing to write-acquire the anon_vma->root->rwsem.
          */
         list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
                 struct anon_vma *anon_vma = avc->anon_vma;
 
                 VM_WARN_ON(anon_vma->num_children);
                 VM_WARN_ON(anon_vma->num_active_vmas);
                 put_anon_vma(anon_vma);
 
                 list_del(&avc->same_vma);
                 anon_vma_chain_free(avc);
         }
 }
 
 static void anon_vma_ctor(void *data)
 {
         struct anon_vma *anon_vma = data;
 
         init_rwsem(&anon_vma->rwsem);
         atomic_set(&anon_vma->refcount, 0);
         anon_vma->rb_root = RB_ROOT_CACHED;
 }
 
 void __init anon_vma_init(void)
 {
         anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
                         0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
                         anon_vma_ctor);
         anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
                         SLAB_PANIC|SLAB_ACCOUNT);
 }
 
 /*
  * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
  *
  * Since there is no serialization what so ever against folio_remove_rmap_*()
  * the best this function can do is return a refcount increased anon_vma
  * that might have been relevant to this page.
  *
  * The page might have been remapped to a different anon_vma or the anon_vma
  * returned may already be freed (and even reused).
  *
  * In case it was remapped to a different anon_vma, the new anon_vma will be a
  * child of the old anon_vma, and the anon_vma lifetime rules will therefore
  * ensure that any anon_vma obtained from the page will still be valid for as
  * long as we observe page_mapped() [ hence all those page_mapped() tests ].
  *
  * All users of this function must be very careful when walking the anon_vma
  * chain and verify that the page in question is indeed mapped in it
  * [ something equivalent to page_mapped_in_vma() ].
  *
  * Since anon_vma's slab is SLAB_TYPESAFE_BY_RCU and we know from
  * folio_remove_rmap_*() that the anon_vma pointer from page->mapping is valid
  * if there is a mapcount, we can dereference the anon_vma after observing
  * those.
  *
  * NOTE: the caller should normally hold folio lock when calling this.  If
  * not, the caller needs to double check the anon_vma didn't change after
  * taking the anon_vma lock for either read or write (UFFDIO_MOVE can modify it
  * concurrently without folio lock protection). See folio_lock_anon_vma_read()
  * which has already covered that, and comment above remap_pages().
  */
 struct anon_vma *folio_get_anon_vma(struct folio *folio)
 {
         struct anon_vma *anon_vma = NULL;
         unsigned long anon_mapping;
 
         rcu_read_lock();
         anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
         if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
                 goto out;
         if (!folio_mapped(folio))
                 goto out;
 
         anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
         if (!atomic_inc_not_zero(&anon_vma->refcount)) {
                 anon_vma = NULL;
                 goto out;
         }
 
         /*
          * If this folio is still mapped, then its anon_vma cannot have been
          * freed.  But if it has been unmapped, we have no security against the
          * anon_vma structure being freed and reused (for another anon_vma:
          * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
          * above cannot corrupt).
          */
         if (!folio_mapped(folio)) {
                 rcu_read_unlock();
                 put_anon_vma(anon_vma);
                 return NULL;
         }
 out:
         rcu_read_unlock();
 
         return anon_vma;
 }
 
 /*
  * Similar to folio_get_anon_vma() except it locks the anon_vma.
  *
  * Its a little more complex as it tries to keep the fast path to a single
  * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
  * reference like with folio_get_anon_vma() and then block on the mutex
  * on !rwc->try_lock case.
  */
 struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
                                           struct rmap_walk_control *rwc)
 {
         struct anon_vma *anon_vma = NULL;
         struct anon_vma *root_anon_vma;
         unsigned long anon_mapping;
 
 retry:
         rcu_read_lock();
         anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
         if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
                 goto out;
         if (!folio_mapped(folio))
                 goto out;
 
         anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
         root_anon_vma = READ_ONCE(anon_vma->root);
         if (down_read_trylock(&root_anon_vma->rwsem)) {
                 /*
                  * folio_move_anon_rmap() might have changed the anon_vma as we
                  * might not hold the folio lock here.
                  */
                 if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
                              anon_mapping)) {
                         up_read(&root_anon_vma->rwsem);
                         rcu_read_unlock();
                         goto retry;
                 }
 
                 /*
                  * If the folio is still mapped, then this anon_vma is still
                  * its anon_vma, and holding the mutex ensures that it will
                  * not go away, see anon_vma_free().
                  */
                 if (!folio_mapped(folio)) {
                         up_read(&root_anon_vma->rwsem);
                         anon_vma = NULL;
                 }
                 goto out;
         }
 
         if (rwc && rwc->try_lock) {
                 anon_vma = NULL;
                 rwc->contended = true;
                 goto out;
         }
 
         /* trylock failed, we got to sleep */
         if (!atomic_inc_not_zero(&anon_vma->refcount)) {
                 anon_vma = NULL;
                 goto out;
         }
 
         if (!folio_mapped(folio)) {
                 rcu_read_unlock();
                 put_anon_vma(anon_vma);
                 return NULL;
         }
 
         /* we pinned the anon_vma, its safe to sleep */
         rcu_read_unlock();
         anon_vma_lock_read(anon_vma);
 
         /*
          * folio_move_anon_rmap() might have changed the anon_vma as we might
          * not hold the folio lock here.
          */
         if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
                      anon_mapping)) {
                 anon_vma_unlock_read(anon_vma);
                 put_anon_vma(anon_vma);
                 anon_vma = NULL;
                 goto retry;
         }
 
         if (atomic_dec_and_test(&anon_vma->refcount)) {
                 /*
                  * Oops, we held the last refcount, release the lock
                  * and bail -- can't simply use put_anon_vma() because
                  * we'll deadlock on the anon_vma_lock_write() recursion.
                  */
                 anon_vma_unlock_read(anon_vma);
                 __put_anon_vma(anon_vma);
                 anon_vma = NULL;
         }
 
         return anon_vma;
 
 out:
         rcu_read_unlock();
         return anon_vma;
 }
 
 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 /*
  * Flush TLB entries for recently unmapped pages from remote CPUs. It is
  * important if a PTE was dirty when it was unmapped that it's flushed
  * before any IO is initiated on the page to prevent lost writes. Similarly,
  * it must be flushed before freeing to prevent data leakage.
  */
 void try_to_unmap_flush(void)
 {
         struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
 
         if (!tlb_ubc->flush_required)
                 return;
 
         arch_tlbbatch_flush(&tlb_ubc->arch);
         tlb_ubc->flush_required = false;
         tlb_ubc->writable = false;
 }
 
 /* Flush iff there are potentially writable TLB entries that can race with IO */
 void try_to_unmap_flush_dirty(void)
 {
         struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
 
         if (tlb_ubc->writable)
                 try_to_unmap_flush();
 }
 
 /*
  * Bits 0-14 of mm->tlb_flush_batched record pending generations.
  * Bits 16-30 of mm->tlb_flush_batched bit record flushed generations.
  */
 #define TLB_FLUSH_BATCH_FLUSHED_SHIFT   16
 #define TLB_FLUSH_BATCH_PENDING_MASK                    \
         ((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1)
 #define TLB_FLUSH_BATCH_PENDING_LARGE                   \
         (TLB_FLUSH_BATCH_PENDING_MASK / 2)
 
 static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
                                       unsigned long uaddr)
 {
         struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
         int batch;
         bool writable = pte_dirty(pteval);
 
         if (!pte_accessible(mm, pteval))
                 return;
 
         arch_tlbbatch_add_pending(&tlb_ubc->arch, mm, uaddr);
         tlb_ubc->flush_required = true;
 
         /*
          * Ensure compiler does not re-order the setting of tlb_flush_batched
          * before the PTE is cleared.
          */
         barrier();
         batch = atomic_read(&mm->tlb_flush_batched);
 retry:
         if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) {
                 /*
                  * Prevent `pending' from catching up with `flushed' because of
                  * overflow.  Reset `pending' and `flushed' to be 1 and 0 if
                  * `pending' becomes large.
                  */
                 if (!atomic_try_cmpxchg(&mm->tlb_flush_batched, &batch, 1))
                         goto retry;
         } else {
                 atomic_inc(&mm->tlb_flush_batched);
         }
 
         /*
          * If the PTE was dirty then it's best to assume it's writable. The
          * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
          * before the page is queued for IO.
          */
         if (writable)
                 tlb_ubc->writable = true;
 }
 
 /*
  * Returns true if the TLB flush should be deferred to the end of a batch of
  * unmap operations to reduce IPIs.
  */
 static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 {
         if (!(flags & TTU_BATCH_FLUSH))
                 return false;
 
         return arch_tlbbatch_should_defer(mm);
 }
 
 /*
  * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
  * releasing the PTL if TLB flushes are batched. It's possible for a parallel
  * operation such as mprotect or munmap to race between reclaim unmapping
  * the page and flushing the page. If this race occurs, it potentially allows
  * access to data via a stale TLB entry. Tracking all mm's that have TLB
  * batching in flight would be expensive during reclaim so instead track
  * whether TLB batching occurred in the past and if so then do a flush here
  * if required. This will cost one additional flush per reclaim cycle paid
  * by the first operation at risk such as mprotect and mumap.
  *
  * This must be called under the PTL so that an access to tlb_flush_batched
  * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
  * via the PTL.
  */
 void flush_tlb_batched_pending(struct mm_struct *mm)
 {
         int batch = atomic_read(&mm->tlb_flush_batched);
         int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK;
         int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
 
         if (pending != flushed) {
                 arch_flush_tlb_batched_pending(mm);
                 /*
                  * If the new TLB flushing is pending during flushing, leave
                  * mm->tlb_flush_batched as is, to avoid losing flushing.
                  */
                 atomic_cmpxchg(&mm->tlb_flush_batched, batch,
                                pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT));
         }
 }
 #else
 static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
                                       unsigned long uaddr)
 {
 }
 
 static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 {
         return false;
 }
 #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
 
 /*
  * At what user virtual address is page expected in vma?
  * Caller should check the page is actually part of the vma.
  */
 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 {
         struct folio *folio = page_folio(page);
         pgoff_t pgoff;
 
         if (folio_test_anon(folio)) {
                 struct anon_vma *page__anon_vma = folio_anon_vma(folio);
                 /*
                  * Note: swapoff's unuse_vma() is more efficient with this
                  * check, and needs it to match anon_vma when KSM is active.
                  */
                 if (!vma->anon_vma || !page__anon_vma ||
                     vma->anon_vma->root != page__anon_vma->root)
                         return -EFAULT;
         } else if (!vma->vm_file) {
                 return -EFAULT;
         } else if (vma->vm_file->f_mapping != folio->mapping) {
                 return -EFAULT;
         }
 
         /* The !page__anon_vma above handles KSM folios */
         pgoff = folio->index + folio_page_idx(folio, page);
         return vma_address(vma, pgoff, 1);
 }
 
 /*
  * Returns the actual pmd_t* where we expect 'address' to be mapped from, or
  * NULL if it doesn't exist.  No guarantees / checks on what the pmd_t*
  * represents.
  */
 pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
 {
         pgd_t *pgd;
         p4d_t *p4d;
         pud_t *pud;
         pmd_t *pmd = NULL;
 
         pgd = pgd_offset(mm, address);
         if (!pgd_present(*pgd))
                 goto out;
 
         p4d = p4d_offset(pgd, address);
         if (!p4d_present(*p4d))
                 goto out;
 
         pud = pud_offset(p4d, address);
         if (!pud_present(*pud))
                 goto out;
 
         pmd = pmd_offset(pud, address);
 out:
         return pmd;
 }
 
 struct folio_referenced_arg {
         int mapcount;
         int referenced;
         unsigned long vm_flags;
         struct mem_cgroup *memcg;
 };
 
 /*
  * arg: folio_referenced_arg will be passed
  */
 static bool folio_referenced_one(struct folio *folio,
                 struct vm_area_struct *vma, unsigned long address, void *arg)
 {
         struct folio_referenced_arg *pra = arg;
         DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
         int referenced = 0;
         unsigned long start = address, ptes = 0;
 
         while (page_vma_mapped_walk(&pvmw)) {
                 address = pvmw.address;
 
                 if (vma->vm_flags & VM_LOCKED) {
                         if (!folio_test_large(folio) || !pvmw.pte) {
                                 /* Restore the mlock which got missed */
                                 mlock_vma_folio(folio, vma);
                                 page_vma_mapped_walk_done(&pvmw);
                                 pra->vm_flags |= VM_LOCKED;
                                 return false; /* To break the loop */
                         }
                         /*
                          * For large folio fully mapped to VMA, will
                          * be handled after the pvmw loop.
                          *
                          * For large folio cross VMA boundaries, it's
                          * expected to be picked  by page reclaim. But
                          * should skip reference of pages which are in
                          * the range of VM_LOCKED vma. As page reclaim
                          * should just count the reference of pages out
                          * the range of VM_LOCKED vma.
                          */
                         ptes++;
                         pra->mapcount--;
                         continue;
                 }
 
                 if (pvmw.pte) {
                         if (lru_gen_enabled() &&
                             pte_young(ptep_get(pvmw.pte))) {
                                 lru_gen_look_around(&pvmw);
                                 referenced++;
                         }
 
                         if (ptep_clear_flush_young_notify(vma, address,
                                                 pvmw.pte))
                                 referenced++;
                 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
                         if (pmdp_clear_flush_young_notify(vma, address,
                                                 pvmw.pmd))
                                 referenced++;
                 } else {
                         /* unexpected pmd-mapped folio? */
                         WARN_ON_ONCE(1);
                 }
 
                 pra->mapcount--;
         }
 
         if ((vma->vm_flags & VM_LOCKED) &&
                         folio_test_large(folio) &&
                         folio_within_vma(folio, vma)) {
                 unsigned long s_align, e_align;
 
                 s_align = ALIGN_DOWN(start, PMD_SIZE);
                 e_align = ALIGN_DOWN(start + folio_size(folio) - 1, PMD_SIZE);
 
                 /* folio doesn't cross page table boundary and fully mapped */
                 if ((s_align == e_align) && (ptes == folio_nr_pages(folio))) {
                         /* Restore the mlock which got missed */
                         mlock_vma_folio(folio, vma);
                         pra->vm_flags |= VM_LOCKED;
                         return false; /* To break the loop */
                 }
         }
 
         if (referenced)
                 folio_clear_idle(folio);
         if (folio_test_clear_young(folio))
                 referenced++;
 
         if (referenced) {
                 pra->referenced++;
                 pra->vm_flags |= vma->vm_flags & ~VM_LOCKED;
         }
 
         if (!pra->mapcount)
                 return false; /* To break the loop */
 
         return true;
 }
 
 static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
 {
         struct folio_referenced_arg *pra = arg;
         struct mem_cgroup *memcg = pra->memcg;
 
         /*
          * Ignore references from this mapping if it has no recency. If the
          * folio has been used in another mapping, we will catch it; if this
          * other mapping is already gone, the unmap path will have set the
          * referenced flag or activated the folio in zap_pte_range().
          */
         if (!vma_has_recency(vma))
                 return true;
 
         /*
          * If we are reclaiming on behalf of a cgroup, skip counting on behalf
          * of references from different cgroups.
          */
         if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
                 return true;
 
         return false;
 }
 
 /**
  * folio_referenced() - Test if the folio was referenced.
  * @folio: The folio to test.
  * @is_locked: Caller holds lock on the folio.
  * @memcg: target memory cgroup
  * @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
  *
  * Quick test_and_clear_referenced for all mappings of a folio,
  *
  * Return: The number of mappings which referenced the folio. Return -1 if
  * the function bailed out due to rmap lock contention.
  */
 int folio_referenced(struct folio *folio, int is_locked,
                      struct mem_cgroup *memcg, unsigned long *vm_flags)
 {
         bool we_locked = false;
         struct folio_referenced_arg pra = {
                 .mapcount = folio_mapcount(folio),
                 .memcg = memcg,
         };
         struct rmap_walk_control rwc = {
                 .rmap_one = folio_referenced_one,
                 .arg = (void *)&pra,
                 .anon_lock = folio_lock_anon_vma_read,
                 .try_lock = true,
                 .invalid_vma = invalid_folio_referenced_vma,
         };
 
         *vm_flags = 0;
         if (!pra.mapcount)
                 return 0;
 
         if (!folio_raw_mapping(folio))
                 return 0;
 
         if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) {
                 we_locked = folio_trylock(folio);
                 if (!we_locked)
                         return 1;
         }
 
         rmap_walk(folio, &rwc);
         *vm_flags = pra.vm_flags;
 
         if (we_locked)
                 folio_unlock(folio);
 
         return rwc.contended ? -1 : pra.referenced;
 }
 
 static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
 {
         int cleaned = 0;
         struct vm_area_struct *vma = pvmw->vma;
         struct mmu_notifier_range range;
         unsigned long address = pvmw->address;
 
         /*
          * We have to assume the worse case ie pmd for invalidation. Note that
          * the folio can not be freed from this function.
          */
         mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0,
                                 vma->vm_mm, address, vma_address_end(pvmw));
         mmu_notifier_invalidate_range_start(&range);
 
         while (page_vma_mapped_walk(pvmw)) {
                 int ret = 0;
 
                 address = pvmw->address;
                 if (pvmw->pte) {
                         pte_t *pte = pvmw->pte;
                         pte_t entry = ptep_get(pte);
 
                         if (!pte_dirty(entry) && !pte_write(entry))
                                 continue;
 
                         flush_cache_page(vma, address, pte_pfn(entry));
                         entry = ptep_clear_flush(vma, address, pte);
                         entry = pte_wrprotect(entry);
                         entry = pte_mkclean(entry);
                         set_pte_at(vma->vm_mm, address, pte, entry);
                         ret = 1;
                 } else {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
                         pmd_t *pmd = pvmw->pmd;
                         pmd_t entry;
 
                         if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
                                 continue;
 
                         flush_cache_range(vma, address,
                                           address + HPAGE_PMD_SIZE);
                         entry = pmdp_invalidate(vma, address, pmd);
                         entry = pmd_wrprotect(entry);
                         entry = pmd_mkclean(entry);
                         set_pmd_at(vma->vm_mm, address, pmd, entry);
                         ret = 1;
 #else
                         /* unexpected pmd-mapped folio? */
                         WARN_ON_ONCE(1);
 #endif
                 }
 
                 if (ret)
                         cleaned++;
         }
 
         mmu_notifier_invalidate_range_end(&range);
 
         return cleaned;
 }
 
 static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma,
                              unsigned long address, void *arg)
 {
         DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC);
         int *cleaned = arg;
 
         *cleaned += page_vma_mkclean_one(&pvmw);
 
         return true;
 }
 
 static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
 {
         if (vma->vm_flags & VM_SHARED)
                 return false;
 
         return true;
 }
 
 int folio_mkclean(struct folio *folio)
 {
         int cleaned = 0;
         struct address_space *mapping;
         struct rmap_walk_control rwc = {
                 .arg = (void *)&cleaned,
                 .rmap_one = page_mkclean_one,
                 .invalid_vma = invalid_mkclean_vma,
         };
 
         BUG_ON(!folio_test_locked(folio));
 
         if (!folio_mapped(folio))
                 return 0;
 
         mapping = folio_mapping(folio);
         if (!mapping)
                 return 0;
 
         rmap_walk(folio, &rwc);
 
         return cleaned;
 }
 EXPORT_SYMBOL_GPL(folio_mkclean);
 
 /**
  * pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of
  *                     [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff)
  *                     within the @vma of shared mappings. And since clean PTEs
  *                     should also be readonly, write protects them too.
  * @pfn: start pfn.
  * @nr_pages: number of physically contiguous pages srarting with @pfn.
  * @pgoff: page offset that the @pfn mapped with.
  * @vma: vma that @pfn mapped within.
  *
  * Returns the number of cleaned PTEs (including PMDs).
  */
 int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
                       struct vm_area_struct *vma)
 {
         struct page_vma_mapped_walk pvmw = {
                 .pfn            = pfn,
                 .nr_pages       = nr_pages,
                 .pgoff          = pgoff,
                 .vma            = vma,
                 .flags          = PVMW_SYNC,
         };
 
         if (invalid_mkclean_vma(vma, NULL))
                 return 0;
 
         pvmw.address = vma_address(vma, pgoff, nr_pages);
         VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma);
 
         return page_vma_mkclean_one(&pvmw);
 }
 
 static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
                 struct page *page, int nr_pages, enum rmap_level level,
                 int *nr_pmdmapped)
 {
         atomic_t *mapped = &folio->_nr_pages_mapped;
         const int orig_nr_pages = nr_pages;
         int first, nr = 0;
 
         __folio_rmap_sanity_checks(folio, page, nr_pages, level);
 
         switch (level) {
         case RMAP_LEVEL_PTE:
                 if (!folio_test_large(folio)) {
                         nr = atomic_inc_and_test(&page->_mapcount);
                         break;
                 }
 
                 do {
                         first = atomic_inc_and_test(&page->_mapcount);
                         if (first) {
                                 first = atomic_inc_return_relaxed(mapped);
                                 if (first < ENTIRELY_MAPPED)
                                         nr++;
                         }
                 } while (page++, --nr_pages > 0);
                 atomic_add(orig_nr_pages, &folio->_large_mapcount);
                 break;
         case RMAP_LEVEL_PMD:
                 first = atomic_inc_and_test(&folio->_entire_mapcount);
                 if (first) {
                         nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped);
                         if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) {
                                 *nr_pmdmapped = folio_nr_pages(folio);
                                 nr = *nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
                                 /* Raced ahead of a remove and another add? */
                                 if (unlikely(nr < 0))
                                         nr = 0;
                         } else {
                                 /* Raced ahead of a remove of ENTIRELY_MAPPED */
                                 nr = 0;
                         }
                 }
                 atomic_inc(&folio->_large_mapcount);
                 break;
         }
         return nr;
 }
 
 /**
  * folio_move_anon_rmap - move a folio to our anon_vma
  * @folio:      The folio to move to our anon_vma
  * @vma:        The vma the folio belongs to
  *
  * When a folio belongs exclusively to one process after a COW event,
  * that folio can be moved into the anon_vma that belongs to just that
  * process, so the rmap code will not search the parent or sibling processes.
  */
 void folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma)
 {
         void *anon_vma = vma->anon_vma;
 
         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
         VM_BUG_ON_VMA(!anon_vma, vma);
 
         anon_vma += PAGE_MAPPING_ANON;
         /*
          * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
          * simultaneously, so a concurrent reader (eg folio_referenced()'s
          * folio_test_anon()) will not see one without the other.
          */
         WRITE_ONCE(folio->mapping, anon_vma);
 }
 
 /**
  * __folio_set_anon - set up a new anonymous rmap for a folio
  * @folio:      The folio to set up the new anonymous rmap for.
  * @vma:        VM area to add the folio to.
  * @address:    User virtual address of the mapping
  * @exclusive:  Whether the folio is exclusive to the process.
  */
 static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma,
                              unsigned long address, bool exclusive)
 {
         struct anon_vma *anon_vma = vma->anon_vma;
 
         BUG_ON(!anon_vma);
 
         /*
          * If the folio isn't exclusive to this vma, we must use the _oldest_
          * possible anon_vma for the folio mapping!
          */
         if (!exclusive)
                 anon_vma = anon_vma->root;
 
         /*
          * page_idle does a lockless/optimistic rmap scan on folio->mapping.
          * Make sure the compiler doesn't split the stores of anon_vma and
          * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
          * could mistake the mapping for a struct address_space and crash.
          */
         anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
         WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma);
         folio->index = linear_page_index(vma, address);
 }
 
 /**
  * __page_check_anon_rmap - sanity check anonymous rmap addition
  * @folio:      The folio containing @page.
  * @page:       the page to check the mapping of
  * @vma:        the vm area in which the mapping is added
  * @address:    the user virtual address mapped
  */
 static void __page_check_anon_rmap(struct folio *folio, struct page *page,
         struct vm_area_struct *vma, unsigned long address)
 {
         /*
          * The page's anon-rmap details (mapping and index) are guaranteed to
          * be set up correctly at this point.
          *
          * We have exclusion against folio_add_anon_rmap_*() because the caller
          * always holds the page locked.
          *
          * We have exclusion against folio_add_new_anon_rmap because those pages
          * are initially only visible via the pagetables, and the pte is locked
          * over the call to folio_add_new_anon_rmap.
          */
         VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
                         folio);
         VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address),
                        page);
 }
 
 static void __folio_mod_stat(struct folio *folio, int nr, int nr_pmdmapped)
 {
         int idx;
 
         if (nr) {
                 idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
                 __lruvec_stat_mod_folio(folio, idx, nr);
         }
         if (nr_pmdmapped) {
                 if (folio_test_anon(folio)) {
                         idx = NR_ANON_THPS;
                         __lruvec_stat_mod_folio(folio, idx, nr_pmdmapped);
                 } else {
                         /* NR_*_PMDMAPPED are not maintained per-memcg */
                         idx = folio_test_swapbacked(folio) ?
                                 NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED;
                         __mod_node_page_state(folio_pgdat(folio), idx,
                                               nr_pmdmapped);
                 }
         }
 }
 
 static __always_inline void __folio_add_anon_rmap(struct folio *folio,
                 struct page *page, int nr_pages, struct vm_area_struct *vma,
                 unsigned long address, rmap_t flags, enum rmap_level level)
 {
         int i, nr, nr_pmdmapped = 0;
 
         VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
 
         nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
 
         if (likely(!folio_test_ksm(folio)))
                 __page_check_anon_rmap(folio, page, vma, address);
 
         __folio_mod_stat(folio, nr, nr_pmdmapped);
 
         if (flags & RMAP_EXCLUSIVE) {
                 switch (level) {
                 case RMAP_LEVEL_PTE:
                         for (i = 0; i < nr_pages; i++)
                                 SetPageAnonExclusive(page + i);
                         break;
                 case RMAP_LEVEL_PMD:
                         SetPageAnonExclusive(page);
                         break;
                 }
         }
         for (i = 0; i < nr_pages; i++) {
                 struct page *cur_page = page + i;
 
                 /* While PTE-mapping a THP we have a PMD and a PTE mapping. */
                 VM_WARN_ON_FOLIO((atomic_read(&cur_page->_mapcount) > 0 ||
                                   (folio_test_large(folio) &&
                                    folio_entire_mapcount(folio) > 1)) &&
                                  PageAnonExclusive(cur_page), folio);
         }
 
         /*
          * For large folio, only mlock it if it's fully mapped to VMA. It's
          * not easy to check whether the large folio is fully mapped to VMA
          * here. Only mlock normal 4K folio and leave page reclaim to handle
          * large folio.
          */
         if (!folio_test_large(folio))
                 mlock_vma_folio(folio, vma);
 }
 
 /**
  * folio_add_anon_rmap_ptes - add PTE mappings to a page range of an anon folio
  * @folio:      The folio to add the mappings to
  * @page:       The first page to add
  * @nr_pages:   The number of pages which will be mapped
  * @vma:        The vm area in which the mappings are added
  * @address:    The user virtual address of the first page to map
  * @flags:      The rmap flags
  *
  * The page range of folio is defined by [first_page, first_page + nr_pages)
  *
  * The caller needs to hold the page table lock, and the page must be locked in
  * the anon_vma case: to serialize mapping,index checking after setting,
  * and to ensure that an anon folio is not being upgraded racily to a KSM folio
  * (but KSM folios are never downgraded).
  */
 void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page,
                 int nr_pages, struct vm_area_struct *vma, unsigned long address,
                 rmap_t flags)
 {
         __folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags,
                               RMAP_LEVEL_PTE);
 }
 
 /**
  * folio_add_anon_rmap_pmd - add a PMD mapping to a page range of an anon folio
  * @folio:      The folio to add the mapping to
  * @page:       The first page to add
  * @vma:        The vm area in which the mapping is added
  * @address:    The user virtual address of the first page to map
  * @flags:      The rmap flags
  *
  * The page range of folio is defined by [first_page, first_page + HPAGE_PMD_NR)
  *
  * The caller needs to hold the page table lock, and the page must be locked in
  * the anon_vma case: to serialize mapping,index checking after setting.
  */
 void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
                 struct vm_area_struct *vma, unsigned long address, rmap_t flags)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         __folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags,
                               RMAP_LEVEL_PMD);
 #else
         WARN_ON_ONCE(true);
 #endif
 }
 
 /**
  * folio_add_new_anon_rmap - Add mapping to a new anonymous folio.
  * @folio:      The folio to add the mapping to.
  * @vma:        the vm area in which the mapping is added
  * @address:    the user virtual address mapped
  * @flags:      The rmap flags
  *
  * Like folio_add_anon_rmap_*() but must only be called on *new* folios.
  * This means the inc-and-test can be bypassed.
  * The folio doesn't necessarily need to be locked while it's exclusive
  * unless two threads map it concurrently. However, the folio must be
  * locked if it's shared.
  *
  * If the folio is pmd-mappable, it is accounted as a THP.
  */
 void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
                 unsigned long address, rmap_t flags)
 {
         const int nr = folio_nr_pages(folio);
         const bool exclusive = flags & RMAP_EXCLUSIVE;
         int nr_pmdmapped = 0;
 
         VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
         VM_WARN_ON_FOLIO(!exclusive && !folio_test_locked(folio), folio);
         VM_BUG_ON_VMA(address < vma->vm_start ||
                         address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
 
         /*
          * VM_DROPPABLE mappings don't swap; instead they're just dropped when
          * under memory pressure.
          */
         if (!folio_test_swapbacked(folio) && !(vma->vm_flags & VM_DROPPABLE))
                 __folio_set_swapbacked(folio);
         __folio_set_anon(folio, vma, address, exclusive);
 
         if (likely(!folio_test_large(folio))) {
                 /* increment count (starts at -1) */
                 atomic_set(&folio->_mapcount, 0);
                 if (exclusive)
                         SetPageAnonExclusive(&folio->page);
         } else if (!folio_test_pmd_mappable(folio)) {
                 int i;
 
                 for (i = 0; i < nr; i++) {
                         struct page *page = folio_page(folio, i);
 
                         /* increment count (starts at -1) */
                         atomic_set(&page->_mapcount, 0);
                         if (exclusive)
                                 SetPageAnonExclusive(page);
                 }
 
                 /* increment count (starts at -1) */
                 atomic_set(&folio->_large_mapcount, nr - 1);
                 atomic_set(&folio->_nr_pages_mapped, nr);
         } else {
                 /* increment count (starts at -1) */
                 atomic_set(&folio->_entire_mapcount, 0);
                 /* increment count (starts at -1) */
                 atomic_set(&folio->_large_mapcount, 0);
                 atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED);
                 if (exclusive)
                         SetPageAnonExclusive(&folio->page);
                 nr_pmdmapped = nr;
         }
 
         __folio_mod_stat(folio, nr, nr_pmdmapped);
 }
 
 static __always_inline void __folio_add_file_rmap(struct folio *folio,
                 struct page *page, int nr_pages, struct vm_area_struct *vma,
                 enum rmap_level level)
 {
         int nr, nr_pmdmapped = 0;
 
         VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
 
         nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
         __folio_mod_stat(folio, nr, nr_pmdmapped);
 
         /* See comments in folio_add_anon_rmap_*() */
         if (!folio_test_large(folio))
                 mlock_vma_folio(folio, vma);
 }
 
 /**
  * folio_add_file_rmap_ptes - add PTE mappings to a page range of a folio
  * @folio:      The folio to add the mappings to
  * @page:       The first page to add
  * @nr_pages:   The number of pages that will be mapped using PTEs
  * @vma:        The vm area in which the mappings are added
  *
  * The page range of the folio is defined by [page, page + nr_pages)
  *
  * The caller needs to hold the page table lock.
  */
 void folio_add_file_rmap_ptes(struct folio *folio, struct page *page,
                 int nr_pages, struct vm_area_struct *vma)
 {
         __folio_add_file_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
 }
 
 /**
  * folio_add_file_rmap_pmd - add a PMD mapping to a page range of a folio
  * @folio:      The folio to add the mapping to
  * @page:       The first page to add
  * @vma:        The vm area in which the mapping is added
  *
  * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
  *
  * The caller needs to hold the page table lock.
  */
 void folio_add_file_rmap_pmd(struct folio *folio, struct page *page,
                 struct vm_area_struct *vma)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         __folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
 #else
         WARN_ON_ONCE(true);
 #endif
 }
 
 static __always_inline void __folio_remove_rmap(struct folio *folio,
                 struct page *page, int nr_pages, struct vm_area_struct *vma,
                 enum rmap_level level)
 {
         atomic_t *mapped = &folio->_nr_pages_mapped;
         int last, nr = 0, nr_pmdmapped = 0;
         bool partially_mapped = false;
 
         __folio_rmap_sanity_checks(folio, page, nr_pages, level);
 
         switch (level) {
         case RMAP_LEVEL_PTE:
                 if (!folio_test_large(folio)) {
                         nr = atomic_add_negative(-1, &page->_mapcount);
                         break;
                 }
 
                 atomic_sub(nr_pages, &folio->_large_mapcount);
                 do {
                         last = atomic_add_negative(-1, &page->_mapcount);
                         if (last) {
                                 last = atomic_dec_return_relaxed(mapped);
                                 if (last < ENTIRELY_MAPPED)
                                         nr++;
                         }
                 } while (page++, --nr_pages > 0);
 
                 partially_mapped = nr && atomic_read(mapped);
                 break;
         case RMAP_LEVEL_PMD:
                 atomic_dec(&folio->_large_mapcount);
                 last = atomic_add_negative(-1, &folio->_entire_mapcount);
                 if (last) {
                         nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);
                         if (likely(nr < ENTIRELY_MAPPED)) {
                                 nr_pmdmapped = folio_nr_pages(folio);
                                 nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
                                 /* Raced ahead of another remove and an add? */
                                 if (unlikely(nr < 0))
                                         nr = 0;
                         } else {
                                 /* An add of ENTIRELY_MAPPED raced ahead */
                                 nr = 0;
                         }
                 }
 
                 partially_mapped = nr < nr_pmdmapped;
                 break;
         }
 
         if (nr) {
                 /*
                  * Queue anon large folio for deferred split if at least one
                  * page of the folio is unmapped and at least one page
                  * is still mapped.
                  *
                  * Check partially_mapped first to ensure it is a large folio.
                  */
                 if (folio_test_anon(folio) && partially_mapped &&
                     list_empty(&folio->_deferred_list))
                         deferred_split_folio(folio);
         }
         __folio_mod_stat(folio, -nr, -nr_pmdmapped);
 
         /*
          * It would be tidy to reset folio_test_anon mapping when fully
          * unmapped, but that might overwrite a racing folio_add_anon_rmap_*()
          * which increments mapcount after us but sets mapping before us:
          * so leave the reset to free_pages_prepare, and remember that
          * it's only reliable while mapped.
          */
 
         munlock_vma_folio(folio, vma);
 }
 
 /**
  * folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio
  * @folio:      The folio to remove the mappings from
  * @page:       The first page to remove
  * @nr_pages:   The number of pages that will be removed from the mapping
  * @vma:        The vm area from which the mappings are removed
  *
  * The page range of the folio is defined by [page, page + nr_pages)
  *
  * The caller needs to hold the page table lock.
  */
 void folio_remove_rmap_ptes(struct folio *folio, struct page *page,
                 int nr_pages, struct vm_area_struct *vma)
 {
         __folio_remove_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
 }
 
 /**
  * folio_remove_rmap_pmd - remove a PMD mapping from a page range of a folio
  * @folio:      The folio to remove the mapping from
  * @page:       The first page to remove
  * @vma:        The vm area from which the mapping is removed
  *
  * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
  *
  * The caller needs to hold the page table lock.
  */
 void folio_remove_rmap_pmd(struct folio *folio, struct page *page,
                 struct vm_area_struct *vma)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         __folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
 #else
         WARN_ON_ONCE(true);
 #endif
 }
 
 /*
  * @arg: enum ttu_flags will be passed to this argument
  */
 static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
                      unsigned long address, void *arg)
 {
         struct mm_struct *mm = vma->vm_mm;
         DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
         pte_t pteval;
         struct page *subpage;
         bool anon_exclusive, ret = true;
         struct mmu_notifier_range range;
         enum ttu_flags flags = (enum ttu_flags)(long)arg;
         unsigned long pfn;
         unsigned long hsz = 0;
 
         /*
          * When racing against e.g. zap_pte_range() on another cpu,
          * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
          * try_to_unmap() may return before page_mapped() has become false,
          * if page table locking is skipped: use TTU_SYNC to wait for that.
          */
         if (flags & TTU_SYNC)
                 pvmw.flags = PVMW_SYNC;
 
         /*
          * For THP, we have to assume the worse case ie pmd for invalidation.
          * For hugetlb, it could be much worse if we need to do pud
          * invalidation in the case of pmd sharing.
          *
          * Note that the folio can not be freed in this function as call of
          * try_to_unmap() must hold a reference on the folio.
          */
         range.end = vma_address_end(&pvmw);
         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
                                 address, range.end);
         if (folio_test_hugetlb(folio)) {
                 /*
                  * If sharing is possible, start and end will be adjusted
                  * accordingly.
                  */
                 adjust_range_if_pmd_sharing_possible(vma, &range.start,
                                                      &range.end);
 
                 /* We need the huge page size for set_huge_pte_at() */
                 hsz = huge_page_size(hstate_vma(vma));
         }
         mmu_notifier_invalidate_range_start(&range);
 
         while (page_vma_mapped_walk(&pvmw)) {
                 /*
                  * If the folio is in an mlock()d vma, we must not swap it out.
                  */
                 if (!(flags & TTU_IGNORE_MLOCK) &&
                     (vma->vm_flags & VM_LOCKED)) {
                         /* Restore the mlock which got missed */
                         if (!folio_test_large(folio))
                                 mlock_vma_folio(folio, vma);
                         goto walk_abort;
                 }
 
                 if (!pvmw.pte) {
                         if (unmap_huge_pmd_locked(vma, pvmw.address, pvmw.pmd,
                                                   folio))
                                 goto walk_done;
 
                         if (flags & TTU_SPLIT_HUGE_PMD) {
                                 /*
                                  * We temporarily have to drop the PTL and
                                  * restart so we can process the PTE-mapped THP.
                                  */
                                 split_huge_pmd_locked(vma, pvmw.address,
                                                       pvmw.pmd, false, folio);
                                 flags &= ~TTU_SPLIT_HUGE_PMD;
                                 page_vma_mapped_walk_restart(&pvmw);
                                 continue;
                         }
                 }
 
                 /* Unexpected PMD-mapped THP? */
                 VM_BUG_ON_FOLIO(!pvmw.pte, folio);
 
                 pfn = pte_pfn(ptep_get(pvmw.pte));
                 subpage = folio_page(folio, pfn - folio_pfn(folio));
                 address = pvmw.address;
                 anon_exclusive = folio_test_anon(folio) &&
                                  PageAnonExclusive(subpage);
 
                 if (folio_test_hugetlb(folio)) {
                         bool anon = folio_test_anon(folio);
 
                         /*
                          * The try_to_unmap() is only passed a hugetlb page
                          * in the case where the hugetlb page is poisoned.
                          */
                         VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage);
                         /*
                          * huge_pmd_unshare may unmap an entire PMD page.
                          * There is no way of knowing exactly which PMDs may
                          * be cached for this mm, so we must flush them all.
                          * start/end were already adjusted above to cover this
                          * range.
                          */
                         flush_cache_range(vma, range.start, range.end);
 
                         /*
                          * To call huge_pmd_unshare, i_mmap_rwsem must be
                          * held in write mode.  Caller needs to explicitly
                          * do this outside rmap routines.
                          *
                          * We also must hold hugetlb vma_lock in write mode.
                          * Lock order dictates acquiring vma_lock BEFORE
                          * i_mmap_rwsem.  We can only try lock here and fail
                          * if unsuccessful.
                          */
                         if (!anon) {
                                 VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
                                 if (!hugetlb_vma_trylock_write(vma))
                                         goto walk_abort;
                                 if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
                                         hugetlb_vma_unlock_write(vma);
                                         flush_tlb_range(vma,
                                                 range.start, range.end);
                                         /*
                                          * The ref count of the PMD page was
                                          * dropped which is part of the way map
                                          * counting is done for shared PMDs.
                                          * Return 'true' here.  When there is
                                          * no other sharing, huge_pmd_unshare
                                          * returns false and we will unmap the
                                          * actual page and drop map count
                                          * to zero.
                                          */
                                         goto walk_done;
                                 }
                                 hugetlb_vma_unlock_write(vma);
                         }
                         pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
                 } else {
                         flush_cache_page(vma, address, pfn);
                         /* Nuke the page table entry. */
                         if (should_defer_flush(mm, flags)) {
                                 /*
                                  * We clear the PTE but do not flush so potentially
                                  * a remote CPU could still be writing to the folio.
                                  * If the entry was previously clean then the
                                  * architecture must guarantee that a clear->dirty
                                  * transition on a cached TLB entry is written through
                                  * and traps if the PTE is unmapped.
                                  */
                                 pteval = ptep_get_and_clear(mm, address, pvmw.pte);
 
                                 set_tlb_ubc_flush_pending(mm, pteval, address);
                         } else {
                                 pteval = ptep_clear_flush(vma, address, pvmw.pte);
                         }
                 }
 
                 /*
                  * Now the pte is cleared. If this pte was uffd-wp armed,
                  * we may want to replace a none pte with a marker pte if
                  * it's file-backed, so we don't lose the tracking info.
                  */
                 pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval);
 
                 /* Set the dirty flag on the folio now the pte is gone. */
                 if (pte_dirty(pteval))
                         folio_mark_dirty(folio);
 
                 /* Update high watermark before we lower rss */
                 update_hiwater_rss(mm);
 
                 if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) {
                         pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
                         if (folio_test_hugetlb(folio)) {
                                 hugetlb_count_sub(folio_nr_pages(folio), mm);
                                 set_huge_pte_at(mm, address, pvmw.pte, pteval,
                                                 hsz);
                         } else {
                                 dec_mm_counter(mm, mm_counter(folio));
                                 set_pte_at(mm, address, pvmw.pte, pteval);
                         }
 
                 } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
                         /*
                          * The guest indicated that the page content is of no
                          * interest anymore. Simply discard the pte, vmscan
                          * will take care of the rest.
                          * A future reference will then fault in a new zero
                          * page. When userfaultfd is active, we must not drop
                          * this page though, as its main user (postcopy
                          * migration) will not expect userfaults on already
                          * copied pages.
                          */
                         dec_mm_counter(mm, mm_counter(folio));
                 } else if (folio_test_anon(folio)) {
                         swp_entry_t entry = page_swap_entry(subpage);
                         pte_t swp_pte;
                         /*
                          * Store the swap location in the pte.
                          * See handle_pte_fault() ...
                          */
                         if (unlikely(folio_test_swapbacked(folio) !=
                                         folio_test_swapcache(folio))) {
                                 WARN_ON_ONCE(1);
                                 goto walk_abort;
                         }
 
                         /* MADV_FREE page check */
                         if (!folio_test_swapbacked(folio)) {
                                 int ref_count, map_count;
 
                                 /*
                                  * Synchronize with gup_pte_range():
                                  * - clear PTE; barrier; read refcount
                                  * - inc refcount; barrier; read PTE
                                  */
                                 smp_mb();
 
                                 ref_count = folio_ref_count(folio);
                                 map_count = folio_mapcount(folio);
 
                                 /*
                                  * Order reads for page refcount and dirty flag
                                  * (see comments in __remove_mapping()).
                                  */
                                 smp_rmb();
 
                                 /*
                                  * The only page refs must be one from isolation
                                  * plus the rmap(s) (dropped by discard:).
                                  */
                                 if (ref_count == 1 + map_count &&
                                     (!folio_test_dirty(folio) ||
                                      /*
                                       * Unlike MADV_FREE mappings, VM_DROPPABLE
                                       * ones can be dropped even if they've
                                       * been dirtied.
                                       */
                                      (vma->vm_flags & VM_DROPPABLE))) {
                                         dec_mm_counter(mm, MM_ANONPAGES);
                                         goto discard;
                                 }
 
                                 /*
                                  * If the folio was redirtied, it cannot be
                                  * discarded. Remap the page to page table.
                                  */
                                 set_pte_at(mm, address, pvmw.pte, pteval);
                                 /*
                                  * Unlike MADV_FREE mappings, VM_DROPPABLE ones
                                  * never get swap backed on failure to drop.
                                  */
                                 if (!(vma->vm_flags & VM_DROPPABLE))
                                         folio_set_swapbacked(folio);
                                 goto walk_abort;
                         }
 
                         if (swap_duplicate(entry) < 0) {
                                 set_pte_at(mm, address, pvmw.pte, pteval);
                                 goto walk_abort;
                         }
                         if (arch_unmap_one(mm, vma, address, pteval) < 0) {
                                 swap_free(entry);
                                 set_pte_at(mm, address, pvmw.pte, pteval);
                                 goto walk_abort;
                         }
 
                         /* See folio_try_share_anon_rmap(): clear PTE first. */
                         if (anon_exclusive &&
                             folio_try_share_anon_rmap_pte(folio, subpage)) {
                                 swap_free(entry);
                                 set_pte_at(mm, address, pvmw.pte, pteval);
                                 goto walk_abort;
                         }
                         if (list_empty(&mm->mmlist)) {
                                 spin_lock(&mmlist_lock);
                                 if (list_empty(&mm->mmlist))
                                         list_add(&mm->mmlist, &init_mm.mmlist);
                                 spin_unlock(&mmlist_lock);
                         }
                         dec_mm_counter(mm, MM_ANONPAGES);
                         inc_mm_counter(mm, MM_SWAPENTS);
                         swp_pte = swp_entry_to_pte(entry);
                         if (anon_exclusive)
                                 swp_pte = pte_swp_mkexclusive(swp_pte);
                         if (pte_soft_dirty(pteval))
                                 swp_pte = pte_swp_mksoft_dirty(swp_pte);
                         if (pte_uffd_wp(pteval))
                                 swp_pte = pte_swp_mkuffd_wp(swp_pte);
                         set_pte_at(mm, address, pvmw.pte, swp_pte);
                 } else {
                         /*
                          * This is a locked file-backed folio,
                          * so it cannot be removed from the page
                          * cache and replaced by a new folio before
                          * mmu_notifier_invalidate_range_end, so no
                          * concurrent thread might update its page table
                          * to point at a new folio while a device is
                          * still using this folio.
                          *
                          * See Documentation/mm/mmu_notifier.rst
                          */
                         dec_mm_counter(mm, mm_counter_file(folio));
                 }
 discard:
                 if (unlikely(folio_test_hugetlb(folio)))
                         hugetlb_remove_rmap(folio);
                 else
                         folio_remove_rmap_pte(folio, subpage, vma);
                 if (vma->vm_flags & VM_LOCKED)
                         mlock_drain_local();
                 folio_put(folio);
                 continue;
 walk_abort:
                 ret = false;
 walk_done:
                 page_vma_mapped_walk_done(&pvmw);
                 break;
         }
 
         mmu_notifier_invalidate_range_end(&range);
 
         return ret;
 }
 
 static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
 {
         return vma_is_temporary_stack(vma);
 }
 
 static int folio_not_mapped(struct folio *folio)
 {
         return !folio_mapped(folio);
 }
 
 /**
  * try_to_unmap - Try to remove all page table mappings to a folio.
  * @folio: The folio to unmap.
  * @flags: action and flags
  *
  * Tries to remove all the page table entries which are mapping this
  * folio.  It is the caller's responsibility to check if the folio is
  * still mapped if needed (use TTU_SYNC to prevent accounting races).
  *
  * Context: Caller must hold the folio lock.
  */
 void try_to_unmap(struct folio *folio, enum ttu_flags flags)
 {
         struct rmap_walk_control rwc = {
                 .rmap_one = try_to_unmap_one,
                 .arg = (void *)flags,
                 .done = folio_not_mapped,
                 .anon_lock = folio_lock_anon_vma_read,
         };
 
         if (flags & TTU_RMAP_LOCKED)
                 rmap_walk_locked(folio, &rwc);
         else
                 rmap_walk(folio, &rwc);
 }
 
 /*
  * @arg: enum ttu_flags will be passed to this argument.
  *
  * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
  * containing migration entries.
  */
 static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
                      unsigned long address, void *arg)
 {
         struct mm_struct *mm = vma->vm_mm;
         DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
         pte_t pteval;
         struct page *subpage;
         bool anon_exclusive, ret = true;
         struct mmu_notifier_range range;
         enum ttu_flags flags = (enum ttu_flags)(long)arg;
         unsigned long pfn;
         unsigned long hsz = 0;
 
         /*
          * When racing against e.g. zap_pte_range() on another cpu,
          * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
          * try_to_migrate() may return before page_mapped() has become false,
          * if page table locking is skipped: use TTU_SYNC to wait for that.
          */
         if (flags & TTU_SYNC)
                 pvmw.flags = PVMW_SYNC;
 
         /*
          * unmap_page() in mm/huge_memory.c is the only user of migration with
          * TTU_SPLIT_HUGE_PMD and it wants to freeze.
          */
         if (flags & TTU_SPLIT_HUGE_PMD)
                 split_huge_pmd_address(vma, address, true, folio);
 
         /*
          * For THP, we have to assume the worse case ie pmd for invalidation.
          * For hugetlb, it could be much worse if we need to do pud
          * invalidation in the case of pmd sharing.
          *
          * Note that the page can not be free in this function as call of
          * try_to_unmap() must hold a reference on the page.
          */
         range.end = vma_address_end(&pvmw);
         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
                                 address, range.end);
         if (folio_test_hugetlb(folio)) {
                 /*
                  * If sharing is possible, start and end will be adjusted
                  * accordingly.
                  */
                 adjust_range_if_pmd_sharing_possible(vma, &range.start,
                                                      &range.end);
 
                 /* We need the huge page size for set_huge_pte_at() */
                 hsz = huge_page_size(hstate_vma(vma));
         }
         mmu_notifier_invalidate_range_start(&range);
 
         while (page_vma_mapped_walk(&pvmw)) {
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
                 /* PMD-mapped THP migration entry */
                 if (!pvmw.pte) {
                         subpage = folio_page(folio,
                                 pmd_pfn(*pvmw.pmd) - folio_pfn(folio));
                         VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
                                         !folio_test_pmd_mappable(folio), folio);
 
                         if (set_pmd_migration_entry(&pvmw, subpage)) {
                                 ret = false;
                                 page_vma_mapped_walk_done(&pvmw);
                                 break;
                         }
                         continue;
                 }
 #endif
 
                 /* Unexpected PMD-mapped THP? */
                 VM_BUG_ON_FOLIO(!pvmw.pte, folio);
 
                 pfn = pte_pfn(ptep_get(pvmw.pte));
 
                 if (folio_is_zone_device(folio)) {
                         /*
                          * Our PTE is a non-present device exclusive entry and
                          * calculating the subpage as for the common case would
                          * result in an invalid pointer.
                          *
                          * Since only PAGE_SIZE pages can currently be
                          * migrated, just set it to page. This will need to be
                          * changed when hugepage migrations to device private
                          * memory are supported.
                          */
                         VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio);
                         subpage = &folio->page;
                 } else {
                         subpage = folio_page(folio, pfn - folio_pfn(folio));
                 }
                 address = pvmw.address;
                 anon_exclusive = folio_test_anon(folio) &&
                                  PageAnonExclusive(subpage);
 
                 if (folio_test_hugetlb(folio)) {
                         bool anon = folio_test_anon(folio);
 
                         /*
                          * huge_pmd_unshare may unmap an entire PMD page.
                          * There is no way of knowing exactly which PMDs may
                          * be cached for this mm, so we must flush them all.
                          * start/end were already adjusted above to cover this
                          * range.
                          */
                         flush_cache_range(vma, range.start, range.end);
 
                         /*
                          * To call huge_pmd_unshare, i_mmap_rwsem must be
                          * held in write mode.  Caller needs to explicitly
                          * do this outside rmap routines.
                          *
                          * We also must hold hugetlb vma_lock in write mode.
                          * Lock order dictates acquiring vma_lock BEFORE
                          * i_mmap_rwsem.  We can only try lock here and
                          * fail if unsuccessful.
                          */
                         if (!anon) {
                                 VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
                                 if (!hugetlb_vma_trylock_write(vma)) {
                                         page_vma_mapped_walk_done(&pvmw);
                                         ret = false;
                                         break;
                                 }
                                 if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
                                         hugetlb_vma_unlock_write(vma);
                                         flush_tlb_range(vma,
                                                 range.start, range.end);
 
                                         /*
                                          * The ref count of the PMD page was
                                          * dropped which is part of the way map
                                          * counting is done for shared PMDs.
                                          * Return 'true' here.  When there is
                                          * no other sharing, huge_pmd_unshare
                                          * returns false and we will unmap the
                                          * actual page and drop map count
                                          * to zero.
                                          */
                                         page_vma_mapped_walk_done(&pvmw);
                                         break;
                                 }
                                 hugetlb_vma_unlock_write(vma);
                         }
                         /* Nuke the hugetlb page table entry */
                         pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
                 } else {
                         flush_cache_page(vma, address, pfn);
                         /* Nuke the page table entry. */
                         if (should_defer_flush(mm, flags)) {
                                 /*
                                  * We clear the PTE but do not flush so potentially
                                  * a remote CPU could still be writing to the folio.
                                  * If the entry was previously clean then the
                                  * architecture must guarantee that a clear->dirty
                                  * transition on a cached TLB entry is written through
                                  * and traps if the PTE is unmapped.
                                  */
                                 pteval = ptep_get_and_clear(mm, address, pvmw.pte);
 
                                 set_tlb_ubc_flush_pending(mm, pteval, address);
                         } else {
                                 pteval = ptep_clear_flush(vma, address, pvmw.pte);
                         }
                 }
 
                 /* Set the dirty flag on the folio now the pte is gone. */
                 if (pte_dirty(pteval))
                         folio_mark_dirty(folio);
 
                 /* Update high watermark before we lower rss */
                 update_hiwater_rss(mm);
 
                 if (folio_is_device_private(folio)) {
                         unsigned long pfn = folio_pfn(folio);
                         swp_entry_t entry;
                         pte_t swp_pte;
 
                         if (anon_exclusive)
                                 WARN_ON_ONCE(folio_try_share_anon_rmap_pte(folio,
                                                                            subpage));
 
                         /*
                          * Store the pfn of the page in a special migration
                          * pte. do_swap_page() will wait until the migration
                          * pte is removed and then restart fault handling.
                          */
                         entry = pte_to_swp_entry(pteval);
                         if (is_writable_device_private_entry(entry))
                                 entry = make_writable_migration_entry(pfn);
                         else if (anon_exclusive)
                                 entry = make_readable_exclusive_migration_entry(pfn);
                         else
                                 entry = make_readable_migration_entry(pfn);
                         swp_pte = swp_entry_to_pte(entry);
 
                         /*
                          * pteval maps a zone device page and is therefore
                          * a swap pte.
                          */
                         if (pte_swp_soft_dirty(pteval))
                                 swp_pte = pte_swp_mksoft_dirty(swp_pte);
                         if (pte_swp_uffd_wp(pteval))
                                 swp_pte = pte_swp_mkuffd_wp(swp_pte);
                         set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
                         trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
                                                 folio_order(folio));
                         /*
                          * No need to invalidate here it will synchronize on
                          * against the special swap migration pte.
                          */
                 } else if (PageHWPoison(subpage)) {
                         pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
                         if (folio_test_hugetlb(folio)) {
                                 hugetlb_count_sub(folio_nr_pages(folio), mm);
                                 set_huge_pte_at(mm, address, pvmw.pte, pteval,
                                                 hsz);
                         } else {
                                 dec_mm_counter(mm, mm_counter(folio));
                                 set_pte_at(mm, address, pvmw.pte, pteval);
                         }
 
                 } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
                         /*
                          * The guest indicated that the page content is of no
                          * interest anymore. Simply discard the pte, vmscan
                          * will take care of the rest.
                          * A future reference will then fault in a new zero
                          * page. When userfaultfd is active, we must not drop
                          * this page though, as its main user (postcopy
                          * migration) will not expect userfaults on already
                          * copied pages.
                          */
                         dec_mm_counter(mm, mm_counter(folio));
                 } else {
                         swp_entry_t entry;
                         pte_t swp_pte;
 
                         if (arch_unmap_one(mm, vma, address, pteval) < 0) {
                                 if (folio_test_hugetlb(folio))
                                         set_huge_pte_at(mm, address, pvmw.pte,
                                                         pteval, hsz);
                                 else
                                         set_pte_at(mm, address, pvmw.pte, pteval);
                                 ret = false;
                                 page_vma_mapped_walk_done(&pvmw);
                                 break;
                         }
                         VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
                                        !anon_exclusive, subpage);
 
                         /* See folio_try_share_anon_rmap_pte(): clear PTE first. */
                         if (folio_test_hugetlb(folio)) {
                                 if (anon_exclusive &&
                                     hugetlb_try_share_anon_rmap(folio)) {
                                         set_huge_pte_at(mm, address, pvmw.pte,
                                                         pteval, hsz);
                                         ret = false;
                                         page_vma_mapped_walk_done(&pvmw);
                                         break;
                                 }
                         } else if (anon_exclusive &&
                                    folio_try_share_anon_rmap_pte(folio, subpage)) {
                                 set_pte_at(mm, address, pvmw.pte, pteval);
                                 ret = false;
                                 page_vma_mapped_walk_done(&pvmw);
                                 break;
                         }
 
                         /*
                          * Store the pfn of the page in a special migration
                          * pte. do_swap_page() will wait until the migration
                          * pte is removed and then restart fault handling.
                          */
                         if (pte_write(pteval))
                                 entry = make_writable_migration_entry(
                                                         page_to_pfn(subpage));
                         else if (anon_exclusive)
                                 entry = make_readable_exclusive_migration_entry(
                                                         page_to_pfn(subpage));
                         else
                                 entry = make_readable_migration_entry(
                                                         page_to_pfn(subpage));
                         if (pte_young(pteval))
                                 entry = make_migration_entry_young(entry);
                         if (pte_dirty(pteval))
                                 entry = make_migration_entry_dirty(entry);
                         swp_pte = swp_entry_to_pte(entry);
                         if (pte_soft_dirty(pteval))
                                 swp_pte = pte_swp_mksoft_dirty(swp_pte);
                         if (pte_uffd_wp(pteval))
                                 swp_pte = pte_swp_mkuffd_wp(swp_pte);
                         if (folio_test_hugetlb(folio))
                                 set_huge_pte_at(mm, address, pvmw.pte, swp_pte,
                                                 hsz);
                         else
                                 set_pte_at(mm, address, pvmw.pte, swp_pte);
                         trace_set_migration_pte(address, pte_val(swp_pte),
                                                 folio_order(folio));
                         /*
                          * No need to invalidate here it will synchronize on
                          * against the special swap migration pte.
                          */
                 }
 
                 if (unlikely(folio_test_hugetlb(folio)))
                         hugetlb_remove_rmap(folio);
                 else
                         folio_remove_rmap_pte(folio, subpage, vma);
                 if (vma->vm_flags & VM_LOCKED)
                         mlock_drain_local();
                 folio_put(folio);
         }
 
         mmu_notifier_invalidate_range_end(&range);
 
         return ret;
 }
 
 /**
  * try_to_migrate - try to replace all page table mappings with swap entries
  * @folio: the folio to replace page table entries for
  * @flags: action and flags
  *
  * Tries to remove all the page table entries which are mapping this folio and
  * replace them with special swap entries. Caller must hold the folio lock.
  */
 void try_to_migrate(struct folio *folio, enum ttu_flags flags)
 {
         struct rmap_walk_control rwc = {
                 .rmap_one = try_to_migrate_one,
                 .arg = (void *)flags,
                 .done = folio_not_mapped,
                 .anon_lock = folio_lock_anon_vma_read,
         };
 
         /*
          * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and
          * TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags.
          */
         if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
                                         TTU_SYNC | TTU_BATCH_FLUSH)))
                 return;
 
         if (folio_is_zone_device(folio) &&
             (!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
                 return;
 
         /*
          * During exec, a temporary VMA is setup and later moved.
          * The VMA is moved under the anon_vma lock but not the
          * page tables leading to a race where migration cannot
          * find the migration ptes. Rather than increasing the
          * locking requirements of exec(), migration skips
          * temporary VMAs until after exec() completes.
          */
         if (!folio_test_ksm(folio) && folio_test_anon(folio))
                 rwc.invalid_vma = invalid_migration_vma;
 
         if (flags & TTU_RMAP_LOCKED)
                 rmap_walk_locked(folio, &rwc);
         else
                 rmap_walk(folio, &rwc);
 }
 
 #ifdef CONFIG_DEVICE_PRIVATE
 struct make_exclusive_args {
         struct mm_struct *mm;
         unsigned long address;
         void *owner;
         bool valid;
 };
 
 static bool page_make_device_exclusive_one(struct folio *folio,
                 struct vm_area_struct *vma, unsigned long address, void *priv)
 {
         struct mm_struct *mm = vma->vm_mm;
         DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
         struct make_exclusive_args *args = priv;
         pte_t pteval;
         struct page *subpage;
         bool ret = true;
         struct mmu_notifier_range range;
         swp_entry_t entry;
         pte_t swp_pte;
         pte_t ptent;
 
         mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0,
                                       vma->vm_mm, address, min(vma->vm_end,
                                       address + folio_size(folio)),
                                       args->owner);
         mmu_notifier_invalidate_range_start(&range);
 
         while (page_vma_mapped_walk(&pvmw)) {
                 /* Unexpected PMD-mapped THP? */
                 VM_BUG_ON_FOLIO(!pvmw.pte, folio);
 
                 ptent = ptep_get(pvmw.pte);
                 if (!pte_present(ptent)) {
                         ret = false;
                         page_vma_mapped_walk_done(&pvmw);
                         break;
                 }
 
                 subpage = folio_page(folio,
                                 pte_pfn(ptent) - folio_pfn(folio));
                 address = pvmw.address;
 
                 /* Nuke the page table entry. */
                 flush_cache_page(vma, address, pte_pfn(ptent));
                 pteval = ptep_clear_flush(vma, address, pvmw.pte);
 
                 /* Set the dirty flag on the folio now the pte is gone. */
                 if (pte_dirty(pteval))
                         folio_mark_dirty(folio);
 
                 /*
                  * Check that our target page is still mapped at the expected
                  * address.
                  */
                 if (args->mm == mm && args->address == address &&
                     pte_write(pteval))
                         args->valid = true;
 
                 /*
                  * Store the pfn of the page in a special migration
                  * pte. do_swap_page() will wait until the migration
                  * pte is removed and then restart fault handling.
                  */
                 if (pte_write(pteval))
                         entry = make_writable_device_exclusive_entry(
                                                         page_to_pfn(subpage));
                 else
                         entry = make_readable_device_exclusive_entry(
                                                         page_to_pfn(subpage));
                 swp_pte = swp_entry_to_pte(entry);
                 if (pte_soft_dirty(pteval))
                         swp_pte = pte_swp_mksoft_dirty(swp_pte);
                 if (pte_uffd_wp(pteval))
                         swp_pte = pte_swp_mkuffd_wp(swp_pte);
 
                 set_pte_at(mm, address, pvmw.pte, swp_pte);
 
                 /*
                  * There is a reference on the page for the swap entry which has
                  * been removed, so shouldn't take another.
                  */
                 folio_remove_rmap_pte(folio, subpage, vma);
         }
 
         mmu_notifier_invalidate_range_end(&range);
 
         return ret;
 }
 
 /**
  * folio_make_device_exclusive - Mark the folio exclusively owned by a device.
  * @folio: The folio to replace page table entries for.
  * @mm: The mm_struct where the folio is expected to be mapped.
  * @address: Address where the folio is expected to be mapped.
  * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks
  *
  * Tries to remove all the page table entries which are mapping this
  * folio and replace them with special device exclusive swap entries to
  * grant a device exclusive access to the folio.
  *
  * Context: Caller must hold the folio lock.
  * Return: false if the page is still mapped, or if it could not be unmapped
  * from the expected address. Otherwise returns true (success).
  */
 static bool folio_make_device_exclusive(struct folio *folio,
                 struct mm_struct *mm, unsigned long address, void *owner)
 {
         struct make_exclusive_args args = {
                 .mm = mm,
                 .address = address,
                 .owner = owner,
                 .valid = false,
         };
         struct rmap_walk_control rwc = {
                 .rmap_one = page_make_device_exclusive_one,
                 .done = folio_not_mapped,
                 .anon_lock = folio_lock_anon_vma_read,
                 .arg = &args,
         };
 
         /*
          * Restrict to anonymous folios for now to avoid potential writeback
          * issues.
          */
         if (!folio_test_anon(folio))
                 return false;
 
         rmap_walk(folio, &rwc);
 
         return args.valid && !folio_mapcount(folio);
 }
 
 /**
  * make_device_exclusive_range() - Mark a range for exclusive use by a device
  * @mm: mm_struct of associated target process
  * @start: start of the region to mark for exclusive device access
  * @end: end address of region
  * @pages: returns the pages which were successfully marked for exclusive access
  * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering
  *
  * Returns: number of pages found in the range by GUP. A page is marked for
  * exclusive access only if the page pointer is non-NULL.
  *
  * This function finds ptes mapping page(s) to the given address range, locks
  * them and replaces mappings with special swap entries preventing userspace CPU
  * access. On fault these entries are replaced with the original mapping after
  * calling MMU notifiers.
  *
  * A driver using this to program access from a device must use a mmu notifier
  * critical section to hold a device specific lock during programming. Once
  * programming is complete it should drop the page lock and reference after
  * which point CPU access to the page will revoke the exclusive access.
  */
 int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
                                 unsigned long end, struct page **pages,
                                 void *owner)
 {
         long npages = (end - start) >> PAGE_SHIFT;
         long i;
 
         npages = get_user_pages_remote(mm, start, npages,
                                        FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
                                        pages, NULL);
         if (npages < 0)
                 return npages;
 
         for (i = 0; i < npages; i++, start += PAGE_SIZE) {
                 struct folio *folio = page_folio(pages[i]);
                 if (PageTail(pages[i]) || !folio_trylock(folio)) {
                         folio_put(folio);
                         pages[i] = NULL;
                         continue;
                 }
 
                 if (!folio_make_device_exclusive(folio, mm, start, owner)) {
                         folio_unlock(folio);
                         folio_put(folio);
                         pages[i] = NULL;
                 }
         }
 
         return npages;
 }
 EXPORT_SYMBOL_GPL(make_device_exclusive_range);
 #endif
 
 void __put_anon_vma(struct anon_vma *anon_vma)
 {
         struct anon_vma *root = anon_vma->root;
 
         anon_vma_free(anon_vma);
         if (root != anon_vma && atomic_dec_and_test(&root->refcount))
                 anon_vma_free(root);
 }
 
 static struct anon_vma *rmap_walk_anon_lock(struct folio *folio,
                                             struct rmap_walk_control *rwc)
 {
         struct anon_vma *anon_vma;
 
         if (rwc->anon_lock)
                 return rwc->anon_lock(folio, rwc);
 
         /*
          * Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read()
          * because that depends on page_mapped(); but not all its usages
          * are holding mmap_lock. Users without mmap_lock are required to
          * take a reference count to prevent the anon_vma disappearing
          */
         anon_vma = folio_anon_vma(folio);
         if (!anon_vma)
                 return NULL;
 
         if (anon_vma_trylock_read(anon_vma))
                 goto out;
 
         if (rwc->try_lock) {
                 anon_vma = NULL;
                 rwc->contended = true;
                 goto out;
         }
 
         anon_vma_lock_read(anon_vma);
 out:
         return anon_vma;
 }
 
 /*
  * rmap_walk_anon - do something to anonymous page using the object-based
  * rmap method
  * @folio: the folio to be handled
  * @rwc: control variable according to each walk type
  * @locked: caller holds relevant rmap lock
  *
  * Find all the mappings of a folio using the mapping pointer and the vma
  * chains contained in the anon_vma struct it points to.
  */
 static void rmap_walk_anon(struct folio *folio,
                 struct rmap_walk_control *rwc, bool locked)
 {
         struct anon_vma *anon_vma;
         pgoff_t pgoff_start, pgoff_end;
         struct anon_vma_chain *avc;
 
         if (locked) {
                 anon_vma = folio_anon_vma(folio);
                 /* anon_vma disappear under us? */
                 VM_BUG_ON_FOLIO(!anon_vma, folio);
         } else {
                 anon_vma = rmap_walk_anon_lock(folio, rwc);
         }
         if (!anon_vma)
                 return;
 
         pgoff_start = folio_pgoff(folio);
         pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
                         pgoff_start, pgoff_end) {
                 struct vm_area_struct *vma = avc->vma;
                 unsigned long address = vma_address(vma, pgoff_start,
                                 folio_nr_pages(folio));
 
                 VM_BUG_ON_VMA(address == -EFAULT, vma);
                 cond_resched();
 
                 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
                         continue;
 
                 if (!rwc->rmap_one(folio, vma, address, rwc->arg))
                         break;
                 if (rwc->done && rwc->done(folio))
                         break;
         }
 
         if (!locked)
                 anon_vma_unlock_read(anon_vma);
 }
 
 /*
  * rmap_walk_file - do something to file page using the object-based rmap method
  * @folio: the folio to be handled
  * @rwc: control variable according to each walk type
  * @locked: caller holds relevant rmap lock
  *
  * Find all the mappings of a folio using the mapping pointer and the vma chains
  * contained in the address_space struct it points to.
  */
 static void rmap_walk_file(struct folio *folio,
                 struct rmap_walk_control *rwc, bool locked)
 {
         struct address_space *mapping = folio_mapping(folio);
         pgoff_t pgoff_start, pgoff_end;
         struct vm_area_struct *vma;
 
         /*
          * The page lock not only makes sure that page->mapping cannot
          * suddenly be NULLified by truncation, it makes sure that the
          * structure at mapping cannot be freed and reused yet,
          * so we can safely take mapping->i_mmap_rwsem.
          */
         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 
         if (!mapping)
                 return;
 
         pgoff_start = folio_pgoff(folio);
         pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
         if (!locked) {
                 if (i_mmap_trylock_read(mapping))
                         goto lookup;
 
                 if (rwc->try_lock) {
                         rwc->contended = true;
                         return;
                 }
 
                 i_mmap_lock_read(mapping);
         }
 lookup:
         vma_interval_tree_foreach(vma, &mapping->i_mmap,
                         pgoff_start, pgoff_end) {
                 unsigned long address = vma_address(vma, pgoff_start,
                                folio_nr_pages(folio));
 
                 VM_BUG_ON_VMA(address == -EFAULT, vma);
                 cond_resched();
 
                 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
                         continue;
 
                 if (!rwc->rmap_one(folio, vma, address, rwc->arg))
                         goto done;
                 if (rwc->done && rwc->done(folio))
                         goto done;
         }
 
 done:
         if (!locked)
                 i_mmap_unlock_read(mapping);
 }
 
 void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc)
 {
         if (unlikely(folio_test_ksm(folio)))
                 rmap_walk_ksm(folio, rwc);
         else if (folio_test_anon(folio))
                 rmap_walk_anon(folio, rwc, false);
         else
                 rmap_walk_file(folio, rwc, false);
 }
 
 /* Like rmap_walk, but caller holds relevant rmap lock */
 void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc)
 {
         /* no ksm support for now */
         VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio);
         if (folio_test_anon(folio))
                 rmap_walk_anon(folio, rwc, true);
         else
                 rmap_walk_file(folio, rwc, true);
 }
 
 #ifdef CONFIG_HUGETLB_PAGE
 /*
  * The following two functions are for anonymous (private mapped) hugepages.
  * Unlike common anonymous pages, anonymous hugepages have no accounting code
  * and no lru code, because we handle hugepages differently from common pages.
  */
 void hugetlb_add_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
                 unsigned long address, rmap_t flags)
 {
         VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
         VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
 
         atomic_inc(&folio->_entire_mapcount);
         atomic_inc(&folio->_large_mapcount);
         if (flags & RMAP_EXCLUSIVE)
                 SetPageAnonExclusive(&folio->page);
         VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 &&
                          PageAnonExclusive(&folio->page), folio);
 }
 
 void hugetlb_add_new_anon_rmap(struct folio *folio,
                 struct vm_area_struct *vma, unsigned long address)
 {
         VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
 
         BUG_ON(address < vma->vm_start || address >= vma->vm_end);
         /* increment count (starts at -1) */
         atomic_set(&folio->_entire_mapcount, 0);
         atomic_set(&folio->_large_mapcount, 0);
         folio_clear_hugetlb_restore_reserve(folio);
         __folio_set_anon(folio, vma, address, true);
         SetPageAnonExclusive(&folio->page);
 }
 #endif /* CONFIG_HUGETLB_PAGE */
 

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