TOMOYO Linux Cross Reference
Linux/fs/locks.c

   // SPDX-License-Identifier: GPL-2.0-only
   /*
    *  linux/fs/locks.c
    *
    * We implement four types of file locks: BSD locks, posix locks, open
    * file description locks, and leases.  For details about BSD locks,
    * see the flock(2) man page; for details about the other three, see
    * fcntl(2).
    *
   *
   * Locking conflicts and dependencies:
   * If multiple threads attempt to lock the same byte (or flock the same file)
   * only one can be granted the lock, and other must wait their turn.
   * The first lock has been "applied" or "granted", the others are "waiting"
   * and are "blocked" by the "applied" lock..
   *
   * Waiting and applied locks are all kept in trees whose properties are:
   *
   *      - the root of a tree may be an applied or waiting lock.
   *      - every other node in the tree is a waiting lock that
   *        conflicts with every ancestor of that node.
   *
   * Every such tree begins life as a waiting singleton which obviously
   * satisfies the above properties.
   *
   * The only ways we modify trees preserve these properties:
   *
   *      1. We may add a new leaf node, but only after first verifying that it
   *         conflicts with all of its ancestors.
   *      2. We may remove the root of a tree, creating a new singleton
   *         tree from the root and N new trees rooted in the immediate
   *         children.
   *      3. If the root of a tree is not currently an applied lock, we may
   *         apply it (if possible).
   *      4. We may upgrade the root of the tree (either extend its range,
   *         or upgrade its entire range from read to write).
   *
   * When an applied lock is modified in a way that reduces or downgrades any
   * part of its range, we remove all its children (2 above).  This particularly
   * happens when a lock is unlocked.
   *
   * For each of those child trees we "wake up" the thread which is
   * waiting for the lock so it can continue handling as follows: if the
   * root of the tree applies, we do so (3).  If it doesn't, it must
   * conflict with some applied lock.  We remove (wake up) all of its children
   * (2), and add it is a new leaf to the tree rooted in the applied
   * lock (1).  We then repeat the process recursively with those
   * children.
   *
   */
  #include <linux/capability.h>
  #include <linux/file.h>
  #include <linux/fdtable.h>
  #include <linux/filelock.h>
  #include <linux/fs.h>
  #include <linux/init.h>
  #include <linux/security.h>
  #include <linux/slab.h>
  #include <linux/syscalls.h>
  #include <linux/time.h>
  #include <linux/rcupdate.h>
  #include <linux/pid_namespace.h>
  #include <linux/hashtable.h>
  #include <linux/percpu.h>
  #include <linux/sysctl.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/filelock.h>
  
  #include <linux/uaccess.h>
  
  static struct file_lock *file_lock(struct file_lock_core *flc)
  {
          return container_of(flc, struct file_lock, c);
  }
  
  static struct file_lease *file_lease(struct file_lock_core *flc)
  {
          return container_of(flc, struct file_lease, c);
  }
  
  static bool lease_breaking(struct file_lease *fl)
  {
          return fl->c.flc_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
  }
  
  static int target_leasetype(struct file_lease *fl)
  {
          if (fl->c.flc_flags & FL_UNLOCK_PENDING)
                  return F_UNLCK;
          if (fl->c.flc_flags & FL_DOWNGRADE_PENDING)
                  return F_RDLCK;
          return fl->c.flc_type;
  }
  
  static int leases_enable = 1;
  static int lease_break_time = 45;
  
  #ifdef CONFIG_SYSCTL
 static struct ctl_table locks_sysctls[] = {
         {
                 .procname       = "leases-enable",
                 .data           = &leases_enable,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
         },
 #ifdef CONFIG_MMU
         {
                 .procname       = "lease-break-time",
                 .data           = &lease_break_time,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
         },
 #endif /* CONFIG_MMU */
 };
 
 static int __init init_fs_locks_sysctls(void)
 {
         register_sysctl_init("fs", locks_sysctls);
         return 0;
 }
 early_initcall(init_fs_locks_sysctls);
 #endif /* CONFIG_SYSCTL */
 
 /*
  * The global file_lock_list is only used for displaying /proc/locks, so we
  * keep a list on each CPU, with each list protected by its own spinlock.
  * Global serialization is done using file_rwsem.
  *
  * Note that alterations to the list also require that the relevant flc_lock is
  * held.
  */
 struct file_lock_list_struct {
         spinlock_t              lock;
         struct hlist_head       hlist;
 };
 static DEFINE_PER_CPU(struct file_lock_list_struct, file_lock_list);
 DEFINE_STATIC_PERCPU_RWSEM(file_rwsem);
 
 
 /*
  * The blocked_hash is used to find POSIX lock loops for deadlock detection.
  * It is protected by blocked_lock_lock.
  *
  * We hash locks by lockowner in order to optimize searching for the lock a
  * particular lockowner is waiting on.
  *
  * FIXME: make this value scale via some heuristic? We generally will want more
  * buckets when we have more lockowners holding locks, but that's a little
  * difficult to determine without knowing what the workload will look like.
  */
 #define BLOCKED_HASH_BITS       7
 static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
 
 /*
  * This lock protects the blocked_hash. Generally, if you're accessing it, you
  * want to be holding this lock.
  *
  * In addition, it also protects the fl->fl_blocked_requests list, and the
  * fl->fl_blocker pointer for file_lock structures that are acting as lock
  * requests (in contrast to those that are acting as records of acquired locks).
  *
  * Note that when we acquire this lock in order to change the above fields,
  * we often hold the flc_lock as well. In certain cases, when reading the fields
  * protected by this lock, we can skip acquiring it iff we already hold the
  * flc_lock.
  */
 static DEFINE_SPINLOCK(blocked_lock_lock);
 
 static struct kmem_cache *flctx_cache __ro_after_init;
 static struct kmem_cache *filelock_cache __ro_after_init;
 static struct kmem_cache *filelease_cache __ro_after_init;
 
 static struct file_lock_context *
 locks_get_lock_context(struct inode *inode, int type)
 {
         struct file_lock_context *ctx;
 
         /* paired with cmpxchg() below */
         ctx = locks_inode_context(inode);
         if (likely(ctx) || type == F_UNLCK)
                 goto out;
 
         ctx = kmem_cache_alloc(flctx_cache, GFP_KERNEL);
         if (!ctx)
                 goto out;
 
         spin_lock_init(&ctx->flc_lock);
         INIT_LIST_HEAD(&ctx->flc_flock);
         INIT_LIST_HEAD(&ctx->flc_posix);
         INIT_LIST_HEAD(&ctx->flc_lease);
 
         /*
          * Assign the pointer if it's not already assigned. If it is, then
          * free the context we just allocated.
          */
         if (cmpxchg(&inode->i_flctx, NULL, ctx)) {
                 kmem_cache_free(flctx_cache, ctx);
                 ctx = locks_inode_context(inode);
         }
 out:
         trace_locks_get_lock_context(inode, type, ctx);
         return ctx;
 }
 
 static void
 locks_dump_ctx_list(struct list_head *list, char *list_type)
 {
         struct file_lock_core *flc;
 
         list_for_each_entry(flc, list, flc_list)
                 pr_warn("%s: fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n",
                         list_type, flc->flc_owner, flc->flc_flags,
                         flc->flc_type, flc->flc_pid);
 }
 
 static void
 locks_check_ctx_lists(struct inode *inode)
 {
         struct file_lock_context *ctx = inode->i_flctx;
 
         if (unlikely(!list_empty(&ctx->flc_flock) ||
                      !list_empty(&ctx->flc_posix) ||
                      !list_empty(&ctx->flc_lease))) {
                 pr_warn("Leaked locks on dev=0x%x:0x%x ino=0x%lx:\n",
                         MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
                         inode->i_ino);
                 locks_dump_ctx_list(&ctx->flc_flock, "FLOCK");
                 locks_dump_ctx_list(&ctx->flc_posix, "POSIX");
                 locks_dump_ctx_list(&ctx->flc_lease, "LEASE");
         }
 }
 
 static void
 locks_check_ctx_file_list(struct file *filp, struct list_head *list, char *list_type)
 {
         struct file_lock_core *flc;
         struct inode *inode = file_inode(filp);
 
         list_for_each_entry(flc, list, flc_list)
                 if (flc->flc_file == filp)
                         pr_warn("Leaked %s lock on dev=0x%x:0x%x ino=0x%lx "
                                 " fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n",
                                 list_type, MAJOR(inode->i_sb->s_dev),
                                 MINOR(inode->i_sb->s_dev), inode->i_ino,
                                 flc->flc_owner, flc->flc_flags,
                                 flc->flc_type, flc->flc_pid);
 }
 
 void
 locks_free_lock_context(struct inode *inode)
 {
         struct file_lock_context *ctx = locks_inode_context(inode);
 
         if (unlikely(ctx)) {
                 locks_check_ctx_lists(inode);
                 kmem_cache_free(flctx_cache, ctx);
         }
 }
 
 static void locks_init_lock_heads(struct file_lock_core *flc)
 {
         INIT_HLIST_NODE(&flc->flc_link);
         INIT_LIST_HEAD(&flc->flc_list);
         INIT_LIST_HEAD(&flc->flc_blocked_requests);
         INIT_LIST_HEAD(&flc->flc_blocked_member);
         init_waitqueue_head(&flc->flc_wait);
 }
 
 /* Allocate an empty lock structure. */
 struct file_lock *locks_alloc_lock(void)
 {
         struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
 
         if (fl)
                 locks_init_lock_heads(&fl->c);
 
         return fl;
 }
 EXPORT_SYMBOL_GPL(locks_alloc_lock);
 
 /* Allocate an empty lock structure. */
 struct file_lease *locks_alloc_lease(void)
 {
         struct file_lease *fl = kmem_cache_zalloc(filelease_cache, GFP_KERNEL);
 
         if (fl)
                 locks_init_lock_heads(&fl->c);
 
         return fl;
 }
 EXPORT_SYMBOL_GPL(locks_alloc_lease);
 
 void locks_release_private(struct file_lock *fl)
 {
         struct file_lock_core *flc = &fl->c;
 
         BUG_ON(waitqueue_active(&flc->flc_wait));
         BUG_ON(!list_empty(&flc->flc_list));
         BUG_ON(!list_empty(&flc->flc_blocked_requests));
         BUG_ON(!list_empty(&flc->flc_blocked_member));
         BUG_ON(!hlist_unhashed(&flc->flc_link));
 
         if (fl->fl_ops) {
                 if (fl->fl_ops->fl_release_private)
                         fl->fl_ops->fl_release_private(fl);
                 fl->fl_ops = NULL;
         }
 
         if (fl->fl_lmops) {
                 if (fl->fl_lmops->lm_put_owner) {
                         fl->fl_lmops->lm_put_owner(flc->flc_owner);
                         flc->flc_owner = NULL;
                 }
                 fl->fl_lmops = NULL;
         }
 }
 EXPORT_SYMBOL_GPL(locks_release_private);
 
 /**
  * locks_owner_has_blockers - Check for blocking lock requests
  * @flctx: file lock context
  * @owner: lock owner
  *
  * Return values:
  *   %true: @owner has at least one blocker
  *   %false: @owner has no blockers
  */
 bool locks_owner_has_blockers(struct file_lock_context *flctx, fl_owner_t owner)
 {
         struct file_lock_core *flc;
 
         spin_lock(&flctx->flc_lock);
         list_for_each_entry(flc, &flctx->flc_posix, flc_list) {
                 if (flc->flc_owner != owner)
                         continue;
                 if (!list_empty(&flc->flc_blocked_requests)) {
                         spin_unlock(&flctx->flc_lock);
                         return true;
                 }
         }
         spin_unlock(&flctx->flc_lock);
         return false;
 }
 EXPORT_SYMBOL_GPL(locks_owner_has_blockers);
 
 /* Free a lock which is not in use. */
 void locks_free_lock(struct file_lock *fl)
 {
         locks_release_private(fl);
         kmem_cache_free(filelock_cache, fl);
 }
 EXPORT_SYMBOL(locks_free_lock);
 
 /* Free a lease which is not in use. */
 void locks_free_lease(struct file_lease *fl)
 {
         kmem_cache_free(filelease_cache, fl);
 }
 EXPORT_SYMBOL(locks_free_lease);
 
 static void
 locks_dispose_list(struct list_head *dispose)
 {
         struct file_lock_core *flc;
 
         while (!list_empty(dispose)) {
                 flc = list_first_entry(dispose, struct file_lock_core, flc_list);
                 list_del_init(&flc->flc_list);
                 if (flc->flc_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
                         locks_free_lease(file_lease(flc));
                 else
                         locks_free_lock(file_lock(flc));
         }
 }
 
 void locks_init_lock(struct file_lock *fl)
 {
         memset(fl, 0, sizeof(struct file_lock));
         locks_init_lock_heads(&fl->c);
 }
 EXPORT_SYMBOL(locks_init_lock);
 
 void locks_init_lease(struct file_lease *fl)
 {
         memset(fl, 0, sizeof(*fl));
         locks_init_lock_heads(&fl->c);
 }
 EXPORT_SYMBOL(locks_init_lease);
 
 /*
  * Initialize a new lock from an existing file_lock structure.
  */
 void locks_copy_conflock(struct file_lock *new, struct file_lock *fl)
 {
         new->c.flc_owner = fl->c.flc_owner;
         new->c.flc_pid = fl->c.flc_pid;
         new->c.flc_file = NULL;
         new->c.flc_flags = fl->c.flc_flags;
         new->c.flc_type = fl->c.flc_type;
         new->fl_start = fl->fl_start;
         new->fl_end = fl->fl_end;
         new->fl_lmops = fl->fl_lmops;
         new->fl_ops = NULL;
 
         if (fl->fl_lmops) {
                 if (fl->fl_lmops->lm_get_owner)
                         fl->fl_lmops->lm_get_owner(fl->c.flc_owner);
         }
 }
 EXPORT_SYMBOL(locks_copy_conflock);
 
 void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
 {
         /* "new" must be a freshly-initialized lock */
         WARN_ON_ONCE(new->fl_ops);
 
         locks_copy_conflock(new, fl);
 
         new->c.flc_file = fl->c.flc_file;
         new->fl_ops = fl->fl_ops;
 
         if (fl->fl_ops) {
                 if (fl->fl_ops->fl_copy_lock)
                         fl->fl_ops->fl_copy_lock(new, fl);
         }
 }
 EXPORT_SYMBOL(locks_copy_lock);
 
 static void locks_move_blocks(struct file_lock *new, struct file_lock *fl)
 {
         struct file_lock *f;
 
         /*
          * As ctx->flc_lock is held, new requests cannot be added to
          * ->flc_blocked_requests, so we don't need a lock to check if it
          * is empty.
          */
         if (list_empty(&fl->c.flc_blocked_requests))
                 return;
         spin_lock(&blocked_lock_lock);
         list_splice_init(&fl->c.flc_blocked_requests,
                          &new->c.flc_blocked_requests);
         list_for_each_entry(f, &new->c.flc_blocked_requests,
                             c.flc_blocked_member)
                 f->c.flc_blocker = &new->c;
         spin_unlock(&blocked_lock_lock);
 }
 
 static inline int flock_translate_cmd(int cmd) {
         switch (cmd) {
         case LOCK_SH:
                 return F_RDLCK;
         case LOCK_EX:
                 return F_WRLCK;
         case LOCK_UN:
                 return F_UNLCK;
         }
         return -EINVAL;
 }
 
 /* Fill in a file_lock structure with an appropriate FLOCK lock. */
 static void flock_make_lock(struct file *filp, struct file_lock *fl, int type)
 {
         locks_init_lock(fl);
 
         fl->c.flc_file = filp;
         fl->c.flc_owner = filp;
         fl->c.flc_pid = current->tgid;
         fl->c.flc_flags = FL_FLOCK;
         fl->c.flc_type = type;
         fl->fl_end = OFFSET_MAX;
 }
 
 static int assign_type(struct file_lock_core *flc, int type)
 {
         switch (type) {
         case F_RDLCK:
         case F_WRLCK:
         case F_UNLCK:
                 flc->flc_type = type;
                 break;
         default:
                 return -EINVAL;
         }
         return 0;
 }
 
 static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
                                  struct flock64 *l)
 {
         switch (l->l_whence) {
         case SEEK_SET:
                 fl->fl_start = 0;
                 break;
         case SEEK_CUR:
                 fl->fl_start = filp->f_pos;
                 break;
         case SEEK_END:
                 fl->fl_start = i_size_read(file_inode(filp));
                 break;
         default:
                 return -EINVAL;
         }
         if (l->l_start > OFFSET_MAX - fl->fl_start)
                 return -EOVERFLOW;
         fl->fl_start += l->l_start;
         if (fl->fl_start < 0)
                 return -EINVAL;
 
         /* POSIX-1996 leaves the case l->l_len < 0 undefined;
            POSIX-2001 defines it. */
         if (l->l_len > 0) {
                 if (l->l_len - 1 > OFFSET_MAX - fl->fl_start)
                         return -EOVERFLOW;
                 fl->fl_end = fl->fl_start + (l->l_len - 1);
 
         } else if (l->l_len < 0) {
                 if (fl->fl_start + l->l_len < 0)
                         return -EINVAL;
                 fl->fl_end = fl->fl_start - 1;
                 fl->fl_start += l->l_len;
         } else
                 fl->fl_end = OFFSET_MAX;
 
         fl->c.flc_owner = current->files;
         fl->c.flc_pid = current->tgid;
         fl->c.flc_file = filp;
         fl->c.flc_flags = FL_POSIX;
         fl->fl_ops = NULL;
         fl->fl_lmops = NULL;
 
         return assign_type(&fl->c, l->l_type);
 }
 
 /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
  * style lock.
  */
 static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
                                struct flock *l)
 {
         struct flock64 ll = {
                 .l_type = l->l_type,
                 .l_whence = l->l_whence,
                 .l_start = l->l_start,
                 .l_len = l->l_len,
         };
 
         return flock64_to_posix_lock(filp, fl, &ll);
 }
 
 /* default lease lock manager operations */
 static bool
 lease_break_callback(struct file_lease *fl)
 {
         kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
         return false;
 }
 
 static void
 lease_setup(struct file_lease *fl, void **priv)
 {
         struct file *filp = fl->c.flc_file;
         struct fasync_struct *fa = *priv;
 
         /*
          * fasync_insert_entry() returns the old entry if any. If there was no
          * old entry, then it used "priv" and inserted it into the fasync list.
          * Clear the pointer to indicate that it shouldn't be freed.
          */
         if (!fasync_insert_entry(fa->fa_fd, filp, &fl->fl_fasync, fa))
                 *priv = NULL;
 
         __f_setown(filp, task_pid(current), PIDTYPE_TGID, 0);
 }
 
 static const struct lease_manager_operations lease_manager_ops = {
         .lm_break = lease_break_callback,
         .lm_change = lease_modify,
         .lm_setup = lease_setup,
 };
 
 /*
  * Initialize a lease, use the default lock manager operations
  */
 static int lease_init(struct file *filp, int type, struct file_lease *fl)
 {
         if (assign_type(&fl->c, type) != 0)
                 return -EINVAL;
 
         fl->c.flc_owner = filp;
         fl->c.flc_pid = current->tgid;
 
         fl->c.flc_file = filp;
         fl->c.flc_flags = FL_LEASE;
         fl->fl_lmops = &lease_manager_ops;
         return 0;
 }
 
 /* Allocate a file_lock initialised to this type of lease */
 static struct file_lease *lease_alloc(struct file *filp, int type)
 {
         struct file_lease *fl = locks_alloc_lease();
         int error = -ENOMEM;
 
         if (fl == NULL)
                 return ERR_PTR(error);
 
         error = lease_init(filp, type, fl);
         if (error) {
                 locks_free_lease(fl);
                 return ERR_PTR(error);
         }
         return fl;
 }
 
 /* Check if two locks overlap each other.
  */
 static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
 {
         return ((fl1->fl_end >= fl2->fl_start) &&
                 (fl2->fl_end >= fl1->fl_start));
 }
 
 /*
  * Check whether two locks have the same owner.
  */
 static int posix_same_owner(struct file_lock_core *fl1, struct file_lock_core *fl2)
 {
         return fl1->flc_owner == fl2->flc_owner;
 }
 
 /* Must be called with the flc_lock held! */
 static void locks_insert_global_locks(struct file_lock_core *flc)
 {
         struct file_lock_list_struct *fll = this_cpu_ptr(&file_lock_list);
 
         percpu_rwsem_assert_held(&file_rwsem);
 
         spin_lock(&fll->lock);
         flc->flc_link_cpu = smp_processor_id();
         hlist_add_head(&flc->flc_link, &fll->hlist);
         spin_unlock(&fll->lock);
 }
 
 /* Must be called with the flc_lock held! */
 static void locks_delete_global_locks(struct file_lock_core *flc)
 {
         struct file_lock_list_struct *fll;
 
         percpu_rwsem_assert_held(&file_rwsem);
 
         /*
          * Avoid taking lock if already unhashed. This is safe since this check
          * is done while holding the flc_lock, and new insertions into the list
          * also require that it be held.
          */
         if (hlist_unhashed(&flc->flc_link))
                 return;
 
         fll = per_cpu_ptr(&file_lock_list, flc->flc_link_cpu);
         spin_lock(&fll->lock);
         hlist_del_init(&flc->flc_link);
         spin_unlock(&fll->lock);
 }
 
 static unsigned long
 posix_owner_key(struct file_lock_core *flc)
 {
         return (unsigned long) flc->flc_owner;
 }
 
 static void locks_insert_global_blocked(struct file_lock_core *waiter)
 {
         lockdep_assert_held(&blocked_lock_lock);
 
         hash_add(blocked_hash, &waiter->flc_link, posix_owner_key(waiter));
 }
 
 static void locks_delete_global_blocked(struct file_lock_core *waiter)
 {
         lockdep_assert_held(&blocked_lock_lock);
 
         hash_del(&waiter->flc_link);
 }
 
 /* Remove waiter from blocker's block list.
  * When blocker ends up pointing to itself then the list is empty.
  *
  * Must be called with blocked_lock_lock held.
  */
 static void __locks_unlink_block(struct file_lock_core *waiter)
 {
         locks_delete_global_blocked(waiter);
         list_del_init(&waiter->flc_blocked_member);
 }
 
 static void __locks_wake_up_blocks(struct file_lock_core *blocker)
 {
         while (!list_empty(&blocker->flc_blocked_requests)) {
                 struct file_lock_core *waiter;
                 struct file_lock *fl;
 
                 waiter = list_first_entry(&blocker->flc_blocked_requests,
                                           struct file_lock_core, flc_blocked_member);
 
                 fl = file_lock(waiter);
                 __locks_unlink_block(waiter);
                 if ((waiter->flc_flags & (FL_POSIX | FL_FLOCK)) &&
                     fl->fl_lmops && fl->fl_lmops->lm_notify)
                         fl->fl_lmops->lm_notify(fl);
                 else
                         locks_wake_up(fl);
 
                 /*
                  * The setting of flc_blocker to NULL marks the "done"
                  * point in deleting a block. Paired with acquire at the top
                  * of locks_delete_block().
                  */
                 smp_store_release(&waiter->flc_blocker, NULL);
         }
 }
 
 static int __locks_delete_block(struct file_lock_core *waiter)
 {
         int status = -ENOENT;
 
         /*
          * If fl_blocker is NULL, it won't be set again as this thread "owns"
          * the lock and is the only one that might try to claim the lock.
          *
          * We use acquire/release to manage fl_blocker so that we can
          * optimize away taking the blocked_lock_lock in many cases.
          *
          * The smp_load_acquire guarantees two things:
          *
          * 1/ that fl_blocked_requests can be tested locklessly. If something
          * was recently added to that list it must have been in a locked region
          * *before* the locked region when fl_blocker was set to NULL.
          *
          * 2/ that no other thread is accessing 'waiter', so it is safe to free
          * it.  __locks_wake_up_blocks is careful not to touch waiter after
          * fl_blocker is released.
          *
          * If a lockless check of fl_blocker shows it to be NULL, we know that
          * no new locks can be inserted into its fl_blocked_requests list, and
          * can avoid doing anything further if the list is empty.
          */
         if (!smp_load_acquire(&waiter->flc_blocker) &&
             list_empty(&waiter->flc_blocked_requests))
                 return status;
 
         spin_lock(&blocked_lock_lock);
         if (waiter->flc_blocker)
                 status = 0;
         __locks_wake_up_blocks(waiter);
         __locks_unlink_block(waiter);
 
         /*
          * The setting of fl_blocker to NULL marks the "done" point in deleting
          * a block. Paired with acquire at the top of this function.
          */
         smp_store_release(&waiter->flc_blocker, NULL);
         spin_unlock(&blocked_lock_lock);
         return status;
 }
 
 /**
  *      locks_delete_block - stop waiting for a file lock
  *      @waiter: the lock which was waiting
  *
  *      lockd/nfsd need to disconnect the lock while working on it.
  */
 int locks_delete_block(struct file_lock *waiter)
 {
         return __locks_delete_block(&waiter->c);
 }
 EXPORT_SYMBOL(locks_delete_block);
 
 /* Insert waiter into blocker's block list.
  * We use a circular list so that processes can be easily woken up in
  * the order they blocked. The documentation doesn't require this but
  * it seems like the reasonable thing to do.
  *
  * Must be called with both the flc_lock and blocked_lock_lock held. The
  * fl_blocked_requests list itself is protected by the blocked_lock_lock,
  * but by ensuring that the flc_lock is also held on insertions we can avoid
  * taking the blocked_lock_lock in some cases when we see that the
  * fl_blocked_requests list is empty.
  *
  * Rather than just adding to the list, we check for conflicts with any existing
  * waiters, and add beneath any waiter that blocks the new waiter.
  * Thus wakeups don't happen until needed.
  */
 static void __locks_insert_block(struct file_lock_core *blocker,
                                  struct file_lock_core *waiter,
                                  bool conflict(struct file_lock_core *,
                                                struct file_lock_core *))
 {
         struct file_lock_core *flc;
 
         BUG_ON(!list_empty(&waiter->flc_blocked_member));
 new_blocker:
         list_for_each_entry(flc, &blocker->flc_blocked_requests, flc_blocked_member)
                 if (conflict(flc, waiter)) {
                         blocker =  flc;
                         goto new_blocker;
                 }
         waiter->flc_blocker = blocker;
         list_add_tail(&waiter->flc_blocked_member,
                       &blocker->flc_blocked_requests);
 
         if ((blocker->flc_flags & (FL_POSIX|FL_OFDLCK)) == FL_POSIX)
                 locks_insert_global_blocked(waiter);
 
         /* The requests in waiter->flc_blocked are known to conflict with
          * waiter, but might not conflict with blocker, or the requests
          * and lock which block it.  So they all need to be woken.
          */
         __locks_wake_up_blocks(waiter);
 }
 
 /* Must be called with flc_lock held. */
 static void locks_insert_block(struct file_lock_core *blocker,
                                struct file_lock_core *waiter,
                                bool conflict(struct file_lock_core *,
                                              struct file_lock_core *))
 {
         spin_lock(&blocked_lock_lock);
         __locks_insert_block(blocker, waiter, conflict);
         spin_unlock(&blocked_lock_lock);
 }
 
 /*
  * Wake up processes blocked waiting for blocker.
  *
  * Must be called with the inode->flc_lock held!
  */
 static void locks_wake_up_blocks(struct file_lock_core *blocker)
 {
         /*
          * Avoid taking global lock if list is empty. This is safe since new
          * blocked requests are only added to the list under the flc_lock, and
          * the flc_lock is always held here. Note that removal from the
          * fl_blocked_requests list does not require the flc_lock, so we must
          * recheck list_empty() after acquiring the blocked_lock_lock.
          */
         if (list_empty(&blocker->flc_blocked_requests))
                 return;
 
         spin_lock(&blocked_lock_lock);
         __locks_wake_up_blocks(blocker);
         spin_unlock(&blocked_lock_lock);
 }
 
 static void
 locks_insert_lock_ctx(struct file_lock_core *fl, struct list_head *before)
 {
         list_add_tail(&fl->flc_list, before);
         locks_insert_global_locks(fl);
 }
 
 static void
 locks_unlink_lock_ctx(struct file_lock_core *fl)
 {
         locks_delete_global_locks(fl);
         list_del_init(&fl->flc_list);
         locks_wake_up_blocks(fl);
 }
 
 static void
 locks_delete_lock_ctx(struct file_lock_core *fl, struct list_head *dispose)
 {
         locks_unlink_lock_ctx(fl);
         if (dispose)
                 list_add(&fl->flc_list, dispose);
         else
                 locks_free_lock(file_lock(fl));
 }
 
 /* Determine if lock sys_fl blocks lock caller_fl. Common functionality
  * checks for shared/exclusive status of overlapping locks.
  */
 static bool locks_conflict(struct file_lock_core *caller_flc,
                            struct file_lock_core *sys_flc)
 {
         if (sys_flc->flc_type == F_WRLCK)
                 return true;
         if (caller_flc->flc_type == F_WRLCK)
                 return true;
         return false;
 }
 
 /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
  * checking before calling the locks_conflict().
  */
 static bool posix_locks_conflict(struct file_lock_core *caller_flc,
                                  struct file_lock_core *sys_flc)
 {
         struct file_lock *caller_fl = file_lock(caller_flc);
         struct file_lock *sys_fl = file_lock(sys_flc);
 
         /* POSIX locks owned by the same process do not conflict with
          * each other.
          */
         if (posix_same_owner(caller_flc, sys_flc))
                 return false;
 
         /* Check whether they overlap */
         if (!locks_overlap(caller_fl, sys_fl))
                 return false;
 
         return locks_conflict(caller_flc, sys_flc);
 }
 
 /* Determine if lock sys_fl blocks lock caller_fl. Used on xx_GETLK
  * path so checks for additional GETLK-specific things like F_UNLCK.
  */
 static bool posix_test_locks_conflict(struct file_lock *caller_fl,
                                       struct file_lock *sys_fl)
 {
         struct file_lock_core *caller = &caller_fl->c;
         struct file_lock_core *sys = &sys_fl->c;
 
         /* F_UNLCK checks any locks on the same fd. */
         if (lock_is_unlock(caller_fl)) {
                 if (!posix_same_owner(caller, sys))
                         return false;
                 return locks_overlap(caller_fl, sys_fl);
         }
         return posix_locks_conflict(caller, sys);
 }
 
 /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
  * checking before calling the locks_conflict().
  */
 static bool flock_locks_conflict(struct file_lock_core *caller_flc,
                                  struct file_lock_core *sys_flc)
 {
         /* FLOCK locks referring to the same filp do not conflict with
          * each other.
          */
         if (caller_flc->flc_file == sys_flc->flc_file)
                 return false;
 
         return locks_conflict(caller_flc, sys_flc);
 }
 
 void
 posix_test_lock(struct file *filp, struct file_lock *fl)
 {
         struct file_lock *cfl;
         struct file_lock_context *ctx;
         struct inode *inode = file_inode(filp);
         void *owner;
         void (*func)(void);
 
         ctx = locks_inode_context(inode);
         if (!ctx || list_empty_careful(&ctx->flc_posix)) {
                 fl->c.flc_type = F_UNLCK;
                 return;
         }
 
 retry:
         spin_lock(&ctx->flc_lock);
         list_for_each_entry(cfl, &ctx->flc_posix, c.flc_list) {
                 if (!posix_test_locks_conflict(fl, cfl))
                         continue;
                 if (cfl->fl_lmops && cfl->fl_lmops->lm_lock_expirable
                         && (*cfl->fl_lmops->lm_lock_expirable)(cfl)) {
                         owner = cfl->fl_lmops->lm_mod_owner;
                         func = cfl->fl_lmops->lm_expire_lock;
                         __module_get(owner);
                         spin_unlock(&ctx->flc_lock);
                         (*func)();
                         module_put(owner);
                         goto retry;
                 }
                 locks_copy_conflock(fl, cfl);
                 goto out;
         }
         fl->c.flc_type = F_UNLCK;
 out:
         spin_unlock(&ctx->flc_lock);
         return;
 }
 EXPORT_SYMBOL(posix_test_lock);
 
 /*
  * Deadlock detection:
  *
  * We attempt to detect deadlocks that are due purely to posix file
  * locks.
  *
  * We assume that a task can be waiting for at most one lock at a time.
  * So for any acquired lock, the process holding that lock may be
  * waiting on at most one other lock.  That lock in turns may be held by
  * someone waiting for at most one other lock.  Given a requested lock
  * caller_fl which is about to wait for a conflicting lock block_fl, we
  * follow this chain of waiters to ensure we are not about to create a
  * cycle.
  *
  * Since we do this before we ever put a process to sleep on a lock, we
  * are ensured that there is never a cycle; that is what guarantees that
  * the while() loop in posix_locks_deadlock() eventually completes.
  *
  * Note: the above assumption may not be true when handling lock
  * requests from a broken NFS client. It may also fail in the presence
  * of tasks (such as posix threads) sharing the same open file table.
  * To handle those cases, we just bail out after a few iterations.
  *
  * For FL_OFDLCK locks, the owner is the filp, not the files_struct.
  * Because the owner is not even nominally tied to a thread of
  * execution, the deadlock detection below can't reasonably work well. Just
  * skip it for those.
  *
  * In principle, we could do a more limited deadlock detection on FL_OFDLCK
  * locks that just checks for the case where two tasks are attempting to
  * upgrade from read to write locks on the same inode.
  */
 
 #define MAX_DEADLK_ITERATIONS 10
 
 /* Find a lock that the owner of the given @blocker is blocking on. */
 static struct file_lock_core *what_owner_is_waiting_for(struct file_lock_core *blocker)
 {
         struct file_lock_core *flc;
 
         hash_for_each_possible(blocked_hash, flc, flc_link, posix_owner_key(blocker)) {
                 if (posix_same_owner(flc, blocker)) {
                         while (flc->flc_blocker)
                                 flc = flc->flc_blocker;
                         return flc;
                 }
         }
         return NULL;
 }
 
 /* Must be called with the blocked_lock_lock held! */
 static bool posix_locks_deadlock(struct file_lock *caller_fl,
                                  struct file_lock *block_fl)
 {
         struct file_lock_core *caller = &caller_fl->c;
         struct file_lock_core *blocker = &block_fl->c;
         int i = 0;
 
         lockdep_assert_held(&blocked_lock_lock);
 
         /*
          * This deadlock detector can't reasonably detect deadlocks with
          * FL_OFDLCK locks, since they aren't owned by a process, per-se.
          */
         if (caller->flc_flags & FL_OFDLCK)
                 return false;
 
         while ((blocker = what_owner_is_waiting_for(blocker))) {
                 if (i++ > MAX_DEADLK_ITERATIONS)
                         return false;
                 if (posix_same_owner(caller, blocker))
                         return true;
         }
         return false;
 }
 
 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
  * after any leases, but before any posix locks.
  *
  * Note that if called with an FL_EXISTS argument, the caller may determine
  * whether or not a lock was successfully freed by testing the return
  * value for -ENOENT.
  */
 static int flock_lock_inode(struct inode *inode, struct file_lock *request)
 {
         struct file_lock *new_fl = NULL;
         struct file_lock *fl;
         struct file_lock_context *ctx;
         int error = 0;
         bool found = false;
         LIST_HEAD(dispose);
 
         ctx = locks_get_lock_context(inode, request->c.flc_type);
         if (!ctx) {
                 if (request->c.flc_type != F_UNLCK)
                         return -ENOMEM;
                 return (request->c.flc_flags & FL_EXISTS) ? -ENOENT : 0;
         }
 
         if (!(request->c.flc_flags & FL_ACCESS) && (request->c.flc_type != F_UNLCK)) {
                 new_fl = locks_alloc_lock();
                 if (!new_fl)
                         return -ENOMEM;
         }
 
         percpu_down_read(&file_rwsem);
         spin_lock(&ctx->flc_lock);
         if (request->c.flc_flags & FL_ACCESS)
                 goto find_conflict;
 
         list_for_each_entry(fl, &ctx->flc_flock, c.flc_list) {
                 if (request->c.flc_file != fl->c.flc_file)
                         continue;
                 if (request->c.flc_type == fl->c.flc_type)
                         goto out;
                 found = true;
                 locks_delete_lock_ctx(&fl->c, &dispose);
                 break;
         }
 
         if (lock_is_unlock(request)) {
                 if ((request->c.flc_flags & FL_EXISTS) && !found)
                         error = -ENOENT;
                 goto out;
         }
 
 find_conflict:
         list_for_each_entry(fl, &ctx->flc_flock, c.flc_list) {
                 if (!flock_locks_conflict(&request->c, &fl->c))
                         continue;
                 error = -EAGAIN;
                 if (!(request->c.flc_flags & FL_SLEEP))
                         goto out;
                 error = FILE_LOCK_DEFERRED;
                 locks_insert_block(&fl->c, &request->c, flock_locks_conflict);
                 goto out;
         }
         if (request->c.flc_flags & FL_ACCESS)
                 goto out;
         locks_copy_lock(new_fl, request);
         locks_move_blocks(new_fl, request);
         locks_insert_lock_ctx(&new_fl->c, &ctx->flc_flock);
         new_fl = NULL;
         error = 0;
 
 out:
         spin_unlock(&ctx->flc_lock);
         percpu_up_read(&file_rwsem);
         if (new_fl)
                 locks_free_lock(new_fl);
         locks_dispose_list(&dispose);
         trace_flock_lock_inode(inode, request, error);
         return error;
 }
 
 static int posix_lock_inode(struct inode *inode, struct file_lock *request,
                             struct file_lock *conflock)
 {
         struct file_lock *fl, *tmp;
         struct file_lock *new_fl = NULL;
         struct file_lock *new_fl2 = NULL;
         struct file_lock *left = NULL;
         struct file_lock *right = NULL;
         struct file_lock_context *ctx;
         int error;
         bool added = false;
         LIST_HEAD(dispose);
         void *owner;
         void (*func)(void);
 
         ctx = locks_get_lock_context(inode, request->c.flc_type);
         if (!ctx)
                 return lock_is_unlock(request) ? 0 : -ENOMEM;
 
         /*
          * We may need two file_lock structures for this operation,
          * so we get them in advance to avoid races.
          *
          * In some cases we can be sure, that no new locks will be needed
          */
         if (!(request->c.flc_flags & FL_ACCESS) &&
             (request->c.flc_type != F_UNLCK ||
              request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
                 new_fl = locks_alloc_lock();
                 new_fl2 = locks_alloc_lock();
         }
 
 retry:
         percpu_down_read(&file_rwsem);
         spin_lock(&ctx->flc_lock);
         /*
          * New lock request. Walk all POSIX locks and look for conflicts. If
          * there are any, either return error or put the request on the
          * blocker's list of waiters and the global blocked_hash.
          */
         if (request->c.flc_type != F_UNLCK) {
                 list_for_each_entry(fl, &ctx->flc_posix, c.flc_list) {
                         if (!posix_locks_conflict(&request->c, &fl->c))
                                 continue;
                         if (fl->fl_lmops && fl->fl_lmops->lm_lock_expirable
                                 && (*fl->fl_lmops->lm_lock_expirable)(fl)) {
                                 owner = fl->fl_lmops->lm_mod_owner;
                                 func = fl->fl_lmops->lm_expire_lock;
                                 __module_get(owner);
                                 spin_unlock(&ctx->flc_lock);
                                 percpu_up_read(&file_rwsem);
                                 (*func)();
                                 module_put(owner);
                                 goto retry;
                         }
                         if (conflock)
                                 locks_copy_conflock(conflock, fl);
                         error = -EAGAIN;
                         if (!(request->c.flc_flags & FL_SLEEP))
                                 goto out;
                         /*
                          * Deadlock detection and insertion into the blocked
                          * locks list must be done while holding the same lock!
                          */
                         error = -EDEADLK;
                         spin_lock(&blocked_lock_lock);
                         /*
                          * Ensure that we don't find any locks blocked on this
                          * request during deadlock detection.
                          */
                         __locks_wake_up_blocks(&request->c);
                         if (likely(!posix_locks_deadlock(request, fl))) {
                                 error = FILE_LOCK_DEFERRED;
                                 __locks_insert_block(&fl->c, &request->c,
                                                      posix_locks_conflict);
                         }
                         spin_unlock(&blocked_lock_lock);
                         goto out;
                 }
         }
 
         /* If we're just looking for a conflict, we're done. */
         error = 0;
         if (request->c.flc_flags & FL_ACCESS)
                 goto out;
 
         /* Find the first old lock with the same owner as the new lock */
         list_for_each_entry(fl, &ctx->flc_posix, c.flc_list) {
                 if (posix_same_owner(&request->c, &fl->c))
                         break;
         }
 
         /* Process locks with this owner. */
         list_for_each_entry_safe_from(fl, tmp, &ctx->flc_posix, c.flc_list) {
                 if (!posix_same_owner(&request->c, &fl->c))
                         break;
 
                 /* Detect adjacent or overlapping regions (if same lock type) */
                 if (request->c.flc_type == fl->c.flc_type) {
                         /* In all comparisons of start vs end, use
                          * "start - 1" rather than "end + 1". If end
                          * is OFFSET_MAX, end + 1 will become negative.
                          */
                         if (fl->fl_end < request->fl_start - 1)
                                 continue;
                         /* If the next lock in the list has entirely bigger
                          * addresses than the new one, insert the lock here.
                          */
                         if (fl->fl_start - 1 > request->fl_end)
                                 break;
 
                         /* If we come here, the new and old lock are of the
                          * same type and adjacent or overlapping. Make one
                          * lock yielding from the lower start address of both
                          * locks to the higher end address.
                          */
                         if (fl->fl_start > request->fl_start)
                                 fl->fl_start = request->fl_start;
                         else
                                 request->fl_start = fl->fl_start;
                         if (fl->fl_end < request->fl_end)
                                 fl->fl_end = request->fl_end;
                         else
                                 request->fl_end = fl->fl_end;
                         if (added) {
                                 locks_delete_lock_ctx(&fl->c, &dispose);
                                 continue;
                         }
                         request = fl;
                         added = true;
                 } else {
                         /* Processing for different lock types is a bit
                          * more complex.
                          */
                         if (fl->fl_end < request->fl_start)
                                 continue;
                         if (fl->fl_start > request->fl_end)
                                 break;
                         if (lock_is_unlock(request))
                                 added = true;
                         if (fl->fl_start < request->fl_start)
                                 left = fl;
                         /* If the next lock in the list has a higher end
                          * address than the new one, insert the new one here.
                          */
                         if (fl->fl_end > request->fl_end) {
                                 right = fl;
                                 break;
                         }
                         if (fl->fl_start >= request->fl_start) {
                                 /* The new lock completely replaces an old
                                  * one (This may happen several times).
                                  */
                                 if (added) {
                                         locks_delete_lock_ctx(&fl->c, &dispose);
                                         continue;
                                 }
                                 /*
                                  * Replace the old lock with new_fl, and
                                  * remove the old one. It's safe to do the
                                  * insert here since we know that we won't be
                                  * using new_fl later, and that the lock is
                                  * just replacing an existing lock.
                                  */
                                 error = -ENOLCK;
                                 if (!new_fl)
                                         goto out;
                                 locks_copy_lock(new_fl, request);
                                 locks_move_blocks(new_fl, request);
                                 request = new_fl;
                                 new_fl = NULL;
                                 locks_insert_lock_ctx(&request->c,
                                                       &fl->c.flc_list);
                                 locks_delete_lock_ctx(&fl->c, &dispose);
                                 added = true;
                         }
                 }
         }
 
         /*
          * The above code only modifies existing locks in case of merging or
          * replacing. If new lock(s) need to be inserted all modifications are
          * done below this, so it's safe yet to bail out.
          */
         error = -ENOLCK; /* "no luck" */
         if (right && left == right && !new_fl2)
                 goto out;
 
         error = 0;
         if (!added) {
                 if (lock_is_unlock(request)) {
                         if (request->c.flc_flags & FL_EXISTS)
                                 error = -ENOENT;
                         goto out;
                 }
 
                 if (!new_fl) {
                         error = -ENOLCK;
                         goto out;
                 }
                 locks_copy_lock(new_fl, request);
                 locks_move_blocks(new_fl, request);
                 locks_insert_lock_ctx(&new_fl->c, &fl->c.flc_list);
                 fl = new_fl;
                 new_fl = NULL;
         }
         if (right) {
                 if (left == right) {
                         /* The new lock breaks the old one in two pieces,
                          * so we have to use the second new lock.
                          */
                         left = new_fl2;
                         new_fl2 = NULL;
                         locks_copy_lock(left, right);
                         locks_insert_lock_ctx(&left->c, &fl->c.flc_list);
                 }
                 right->fl_start = request->fl_end + 1;
                 locks_wake_up_blocks(&right->c);
         }
         if (left) {
                 left->fl_end = request->fl_start - 1;
                 locks_wake_up_blocks(&left->c);
         }
  out:
         trace_posix_lock_inode(inode, request, error);
         spin_unlock(&ctx->flc_lock);
         percpu_up_read(&file_rwsem);
         /*
          * Free any unused locks.
          */
         if (new_fl)
                 locks_free_lock(new_fl);
         if (new_fl2)
                 locks_free_lock(new_fl2);
         locks_dispose_list(&dispose);
 
         return error;
 }
 
 /**
  * posix_lock_file - Apply a POSIX-style lock to a file
  * @filp: The file to apply the lock to
  * @fl: The lock to be applied
  * @conflock: Place to return a copy of the conflicting lock, if found.
  *
  * Add a POSIX style lock to a file.
  * We merge adjacent & overlapping locks whenever possible.
  * POSIX locks are sorted by owner task, then by starting address
  *
  * Note that if called with an FL_EXISTS argument, the caller may determine
  * whether or not a lock was successfully freed by testing the return
  * value for -ENOENT.
  */
 int posix_lock_file(struct file *filp, struct file_lock *fl,
                         struct file_lock *conflock)
 {
         return posix_lock_inode(file_inode(filp), fl, conflock);
 }
 EXPORT_SYMBOL(posix_lock_file);
 
 /**
  * posix_lock_inode_wait - Apply a POSIX-style lock to a file
  * @inode: inode of file to which lock request should be applied
  * @fl: The lock to be applied
  *
  * Apply a POSIX style lock request to an inode.
  */
 static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl)
 {
         int error;
         might_sleep ();
         for (;;) {
                 error = posix_lock_inode(inode, fl, NULL);
                 if (error != FILE_LOCK_DEFERRED)
                         break;
                 error = wait_event_interruptible(fl->c.flc_wait,
                                                  list_empty(&fl->c.flc_blocked_member));
                 if (error)
                         break;
         }
         locks_delete_block(fl);
         return error;
 }
 
 static void lease_clear_pending(struct file_lease *fl, int arg)
 {
         switch (arg) {
         case F_UNLCK:
                 fl->c.flc_flags &= ~FL_UNLOCK_PENDING;
                 fallthrough;
         case F_RDLCK:
                 fl->c.flc_flags &= ~FL_DOWNGRADE_PENDING;
         }
 }
 
 /* We already had a lease on this file; just change its type */
 int lease_modify(struct file_lease *fl, int arg, struct list_head *dispose)
 {
         int error = assign_type(&fl->c, arg);
 
         if (error)
                 return error;
         lease_clear_pending(fl, arg);
         locks_wake_up_blocks(&fl->c);
         if (arg == F_UNLCK) {
                 struct file *filp = fl->c.flc_file;
 
                 f_delown(filp);
                 filp->f_owner.signum = 0;
                 fasync_helper(0, fl->c.flc_file, 0, &fl->fl_fasync);
                 if (fl->fl_fasync != NULL) {
                         printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
                         fl->fl_fasync = NULL;
                 }
                 locks_delete_lock_ctx(&fl->c, dispose);
         }
         return 0;
 }
 EXPORT_SYMBOL(lease_modify);
 
 static bool past_time(unsigned long then)
 {
         if (!then)
                 /* 0 is a special value meaning "this never expires": */
                 return false;
         return time_after(jiffies, then);
 }
 
 static void time_out_leases(struct inode *inode, struct list_head *dispose)
 {
         struct file_lock_context *ctx = inode->i_flctx;
         struct file_lease *fl, *tmp;
 
         lockdep_assert_held(&ctx->flc_lock);
 
         list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, c.flc_list) {
                 trace_time_out_leases(inode, fl);
                 if (past_time(fl->fl_downgrade_time))
                         lease_modify(fl, F_RDLCK, dispose);
                 if (past_time(fl->fl_break_time))
                         lease_modify(fl, F_UNLCK, dispose);
         }
 }
 
 static bool leases_conflict(struct file_lock_core *lc, struct file_lock_core *bc)
 {
         bool rc;
         struct file_lease *lease = file_lease(lc);
         struct file_lease *breaker = file_lease(bc);
 
         if (lease->fl_lmops->lm_breaker_owns_lease
                         && lease->fl_lmops->lm_breaker_owns_lease(lease))
                 return false;
         if ((bc->flc_flags & FL_LAYOUT) != (lc->flc_flags & FL_LAYOUT)) {
                 rc = false;
                 goto trace;
         }
         if ((bc->flc_flags & FL_DELEG) && (lc->flc_flags & FL_LEASE)) {
                 rc = false;
                 goto trace;
         }
 
         rc = locks_conflict(bc, lc);
 trace:
         trace_leases_conflict(rc, lease, breaker);
         return rc;
 }
 
 static bool
 any_leases_conflict(struct inode *inode, struct file_lease *breaker)
 {
         struct file_lock_context *ctx = inode->i_flctx;
         struct file_lock_core *flc;
 
         lockdep_assert_held(&ctx->flc_lock);
 
         list_for_each_entry(flc, &ctx->flc_lease, flc_list) {
                 if (leases_conflict(flc, &breaker->c))
                         return true;
         }
         return false;
 }
 
 /**
  *      __break_lease   -       revoke all outstanding leases on file
  *      @inode: the inode of the file to return
  *      @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR:
  *          break all leases
  *      @type: FL_LEASE: break leases and delegations; FL_DELEG: break
  *          only delegations
  *
  *      break_lease (inlined for speed) has checked there already is at least
  *      some kind of lock (maybe a lease) on this file.  Leases are broken on
  *      a call to open() or truncate().  This function can sleep unless you
  *      specified %O_NONBLOCK to your open().
  */
 int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 {
         int error = 0;
         struct file_lock_context *ctx;
         struct file_lease *new_fl, *fl, *tmp;
         unsigned long break_time;
         int want_write = (mode & O_ACCMODE) != O_RDONLY;
         LIST_HEAD(dispose);
 
         new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
         if (IS_ERR(new_fl))
                 return PTR_ERR(new_fl);
         new_fl->c.flc_flags = type;
 
         /* typically we will check that ctx is non-NULL before calling */
         ctx = locks_inode_context(inode);
         if (!ctx) {
                 WARN_ON_ONCE(1);
                 goto free_lock;
         }
 
         percpu_down_read(&file_rwsem);
         spin_lock(&ctx->flc_lock);
 
         time_out_leases(inode, &dispose);
 
         if (!any_leases_conflict(inode, new_fl))
                 goto out;
 
         break_time = 0;
         if (lease_break_time > 0) {
                 break_time = jiffies + lease_break_time * HZ;
                 if (break_time == 0)
                         break_time++;   /* so that 0 means no break time */
         }
 
         list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, c.flc_list) {
                 if (!leases_conflict(&fl->c, &new_fl->c))
                         continue;
                 if (want_write) {
                         if (fl->c.flc_flags & FL_UNLOCK_PENDING)
                                 continue;
                         fl->c.flc_flags |= FL_UNLOCK_PENDING;
                         fl->fl_break_time = break_time;
                 } else {
                         if (lease_breaking(fl))
                                 continue;
                         fl->c.flc_flags |= FL_DOWNGRADE_PENDING;
                         fl->fl_downgrade_time = break_time;
                 }
                 if (fl->fl_lmops->lm_break(fl))
                         locks_delete_lock_ctx(&fl->c, &dispose);
         }
 
         if (list_empty(&ctx->flc_lease))
                 goto out;
 
         if (mode & O_NONBLOCK) {
                 trace_break_lease_noblock(inode, new_fl);
                 error = -EWOULDBLOCK;
                 goto out;
         }
 
 restart:
         fl = list_first_entry(&ctx->flc_lease, struct file_lease, c.flc_list);
         break_time = fl->fl_break_time;
         if (break_time != 0)
                 break_time -= jiffies;
         if (break_time == 0)
                 break_time++;
         locks_insert_block(&fl->c, &new_fl->c, leases_conflict);
         trace_break_lease_block(inode, new_fl);
         spin_unlock(&ctx->flc_lock);
         percpu_up_read(&file_rwsem);
 
         locks_dispose_list(&dispose);
         error = wait_event_interruptible_timeout(new_fl->c.flc_wait,
                                                  list_empty(&new_fl->c.flc_blocked_member),
                                                  break_time);
 
         percpu_down_read(&file_rwsem);
         spin_lock(&ctx->flc_lock);
         trace_break_lease_unblock(inode, new_fl);
         __locks_delete_block(&new_fl->c);
         if (error >= 0) {
                 /*
                  * Wait for the next conflicting lease that has not been
                  * broken yet
                  */
                 if (error == 0)
                         time_out_leases(inode, &dispose);
                 if (any_leases_conflict(inode, new_fl))
                         goto restart;
                 error = 0;
         }
 out:
         spin_unlock(&ctx->flc_lock);
         percpu_up_read(&file_rwsem);
         locks_dispose_list(&dispose);
 free_lock:
         locks_free_lease(new_fl);
         return error;
 }
 EXPORT_SYMBOL(__break_lease);
 
 /**
  *      lease_get_mtime - update modified time of an inode with exclusive lease
  *      @inode: the inode
  *      @time:  pointer to a timespec which contains the last modified time
  *
  * This is to force NFS clients to flush their caches for files with
  * exclusive leases.  The justification is that if someone has an
  * exclusive lease, then they could be modifying it.
  */
 void lease_get_mtime(struct inode *inode, struct timespec64 *time)
 {
         bool has_lease = false;
         struct file_lock_context *ctx;
         struct file_lock_core *flc;
 
         ctx = locks_inode_context(inode);
         if (ctx && !list_empty_careful(&ctx->flc_lease)) {
                 spin_lock(&ctx->flc_lock);
                 flc = list_first_entry_or_null(&ctx->flc_lease,
                                                struct file_lock_core, flc_list);
                 if (flc && flc->flc_type == F_WRLCK)
                         has_lease = true;
                 spin_unlock(&ctx->flc_lock);
         }
 
         if (has_lease)
                 *time = current_time(inode);
 }
 EXPORT_SYMBOL(lease_get_mtime);
 
 /**
  *      fcntl_getlease - Enquire what lease is currently active
  *      @filp: the file
  *
  *      The value returned by this function will be one of
  *      (if no lease break is pending):
  *
  *      %F_RDLCK to indicate a shared lease is held.
  *
  *      %F_WRLCK to indicate an exclusive lease is held.
  *
  *      %F_UNLCK to indicate no lease is held.
  *
  *      (if a lease break is pending):
  *
  *      %F_RDLCK to indicate an exclusive lease needs to be
  *              changed to a shared lease (or removed).
  *
  *      %F_UNLCK to indicate the lease needs to be removed.
  *
  *      XXX: sfr & willy disagree over whether F_INPROGRESS
  *      should be returned to userspace.
  */
 int fcntl_getlease(struct file *filp)
 {
         struct file_lease *fl;
         struct inode *inode = file_inode(filp);
         struct file_lock_context *ctx;
         int type = F_UNLCK;
         LIST_HEAD(dispose);
 
         ctx = locks_inode_context(inode);
         if (ctx && !list_empty_careful(&ctx->flc_lease)) {
                 percpu_down_read(&file_rwsem);
                 spin_lock(&ctx->flc_lock);
                 time_out_leases(inode, &dispose);
                 list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
                         if (fl->c.flc_file != filp)
                                 continue;
                         type = target_leasetype(fl);
                         break;
                 }
                 spin_unlock(&ctx->flc_lock);
                 percpu_up_read(&file_rwsem);
 
                 locks_dispose_list(&dispose);
         }
         return type;
 }
 
 /**
  * check_conflicting_open - see if the given file points to an inode that has
  *                          an existing open that would conflict with the
  *                          desired lease.
  * @filp:       file to check
  * @arg:        type of lease that we're trying to acquire
  * @flags:      current lock flags
  *
  * Check to see if there's an existing open fd on this file that would
  * conflict with the lease we're trying to set.
  */
 static int
 check_conflicting_open(struct file *filp, const int arg, int flags)
 {
         struct inode *inode = file_inode(filp);
         int self_wcount = 0, self_rcount = 0;
 
         if (flags & FL_LAYOUT)
                 return 0;
         if (flags & FL_DELEG)
                 /* We leave these checks to the caller */
                 return 0;
 
         if (arg == F_RDLCK)
                 return inode_is_open_for_write(inode) ? -EAGAIN : 0;
         else if (arg != F_WRLCK)
                 return 0;
 
         /*
          * Make sure that only read/write count is from lease requestor.
          * Note that this will result in denying write leases when i_writecount
          * is negative, which is what we want.  (We shouldn't grant write leases
          * on files open for execution.)
          */
         if (filp->f_mode & FMODE_WRITE)
                 self_wcount = 1;
         else if (filp->f_mode & FMODE_READ)
                 self_rcount = 1;
 
         if (atomic_read(&inode->i_writecount) != self_wcount ||
             atomic_read(&inode->i_readcount) != self_rcount)
                 return -EAGAIN;
 
         return 0;
 }
 
 static int
 generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **priv)
 {
         struct file_lease *fl, *my_fl = NULL, *lease;
         struct inode *inode = file_inode(filp);
         struct file_lock_context *ctx;
         bool is_deleg = (*flp)->c.flc_flags & FL_DELEG;
         int error;
         LIST_HEAD(dispose);
 
         lease = *flp;
         trace_generic_add_lease(inode, lease);
 
         /* Note that arg is never F_UNLCK here */
         ctx = locks_get_lock_context(inode, arg);
         if (!ctx)
                 return -ENOMEM;
 
         /*
          * In the delegation case we need mutual exclusion with
          * a number of operations that take the i_mutex.  We trylock
          * because delegations are an optional optimization, and if
          * there's some chance of a conflict--we'd rather not
          * bother, maybe that's a sign this just isn't a good file to
          * hand out a delegation on.
          */
         if (is_deleg && !inode_trylock(inode))
                 return -EAGAIN;
 
         percpu_down_read(&file_rwsem);
         spin_lock(&ctx->flc_lock);
         time_out_leases(inode, &dispose);
         error = check_conflicting_open(filp, arg, lease->c.flc_flags);
         if (error)
                 goto out;
 
         /*
          * At this point, we know that if there is an exclusive
          * lease on this file, then we hold it on this filp
          * (otherwise our open of this file would have blocked).
          * And if we are trying to acquire an exclusive lease,
          * then the file is not open by anyone (including us)
          * except for this filp.
          */
         error = -EAGAIN;
         list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
                 if (fl->c.flc_file == filp &&
                     fl->c.flc_owner == lease->c.flc_owner) {
                         my_fl = fl;
                         continue;
                 }
 
                 /*
                  * No exclusive leases if someone else has a lease on
                  * this file:
                  */
                 if (arg == F_WRLCK)
                         goto out;
                 /*
                  * Modifying our existing lease is OK, but no getting a
                  * new lease if someone else is opening for write:
                  */
                 if (fl->c.flc_flags & FL_UNLOCK_PENDING)
                         goto out;
         }
 
         if (my_fl != NULL) {
                 lease = my_fl;
                 error = lease->fl_lmops->lm_change(lease, arg, &dispose);
                 if (error)
                         goto out;
                 goto out_setup;
         }
 
         error = -EINVAL;
         if (!leases_enable)
                 goto out;
 
         locks_insert_lock_ctx(&lease->c, &ctx->flc_lease);
         /*
          * The check in break_lease() is lockless. It's possible for another
          * open to race in after we did the earlier check for a conflicting
          * open but before the lease was inserted. Check again for a
          * conflicting open and cancel the lease if there is one.
          *
          * We also add a barrier here to ensure that the insertion of the lock
          * precedes these checks.
          */
         smp_mb();
         error = check_conflicting_open(filp, arg, lease->c.flc_flags);
         if (error) {
                 locks_unlink_lock_ctx(&lease->c);
                 goto out;
         }
 
 out_setup:
         if (lease->fl_lmops->lm_setup)
                 lease->fl_lmops->lm_setup(lease, priv);
 out:
         spin_unlock(&ctx->flc_lock);
         percpu_up_read(&file_rwsem);
         locks_dispose_list(&dispose);
         if (is_deleg)
                 inode_unlock(inode);
         if (!error && !my_fl)
                 *flp = NULL;
         return error;
 }
 
 static int generic_delete_lease(struct file *filp, void *owner)
 {
         int error = -EAGAIN;
         struct file_lease *fl, *victim = NULL;
         struct inode *inode = file_inode(filp);
         struct file_lock_context *ctx;
         LIST_HEAD(dispose);
 
         ctx = locks_inode_context(inode);
         if (!ctx) {
                 trace_generic_delete_lease(inode, NULL);
                 return error;
         }
 
         percpu_down_read(&file_rwsem);
         spin_lock(&ctx->flc_lock);
         list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
                 if (fl->c.flc_file == filp &&
                     fl->c.flc_owner == owner) {
                         victim = fl;
                         break;
                 }
         }
         trace_generic_delete_lease(inode, victim);
         if (victim)
                 error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
         spin_unlock(&ctx->flc_lock);
         percpu_up_read(&file_rwsem);
         locks_dispose_list(&dispose);
         return error;
 }
 
 /**
  *      generic_setlease        -       sets a lease on an open file
  *      @filp:  file pointer
  *      @arg:   type of lease to obtain
  *      @flp:   input - file_lock to use, output - file_lock inserted
  *      @priv:  private data for lm_setup (may be NULL if lm_setup
  *              doesn't require it)
  *
  *      The (input) flp->fl_lmops->lm_break function is required
  *      by break_lease().
  */
 int generic_setlease(struct file *filp, int arg, struct file_lease **flp,
                         void **priv)
 {
         switch (arg) {
         case F_UNLCK:
                 return generic_delete_lease(filp, *priv);
         case F_RDLCK:
         case F_WRLCK:
                 if (!(*flp)->fl_lmops->lm_break) {
                         WARN_ON_ONCE(1);
                         return -ENOLCK;
                 }
 
                 return generic_add_lease(filp, arg, flp, priv);
         default:
                 return -EINVAL;
         }
 }
 EXPORT_SYMBOL(generic_setlease);
 
 /*
  * Kernel subsystems can register to be notified on any attempt to set
  * a new lease with the lease_notifier_chain. This is used by (e.g.) nfsd
  * to close files that it may have cached when there is an attempt to set a
  * conflicting lease.
  */
 static struct srcu_notifier_head lease_notifier_chain;
 
 static inline void
 lease_notifier_chain_init(void)
 {
         srcu_init_notifier_head(&lease_notifier_chain);
 }
 
 static inline void
 setlease_notifier(int arg, struct file_lease *lease)
 {
         if (arg != F_UNLCK)
                 srcu_notifier_call_chain(&lease_notifier_chain, arg, lease);
 }
 
 int lease_register_notifier(struct notifier_block *nb)
 {
         return srcu_notifier_chain_register(&lease_notifier_chain, nb);
 }
 EXPORT_SYMBOL_GPL(lease_register_notifier);
 
 void lease_unregister_notifier(struct notifier_block *nb)
 {
         srcu_notifier_chain_unregister(&lease_notifier_chain, nb);
 }
 EXPORT_SYMBOL_GPL(lease_unregister_notifier);
 
 
 int
 kernel_setlease(struct file *filp, int arg, struct file_lease **lease, void **priv)
 {
         if (lease)
                 setlease_notifier(arg, *lease);
         if (filp->f_op->setlease)
                 return filp->f_op->setlease(filp, arg, lease, priv);
         else
                 return generic_setlease(filp, arg, lease, priv);
 }
 EXPORT_SYMBOL_GPL(kernel_setlease);
 
 /**
  * vfs_setlease        -       sets a lease on an open file
  * @filp:       file pointer
  * @arg:        type of lease to obtain
  * @lease:      file_lock to use when adding a lease
  * @priv:       private info for lm_setup when adding a lease (may be
  *              NULL if lm_setup doesn't require it)
  *
  * Call this to establish a lease on the file. The "lease" argument is not
  * used for F_UNLCK requests and may be NULL. For commands that set or alter
  * an existing lease, the ``(*lease)->fl_lmops->lm_break`` operation must be
  * set; if not, this function will return -ENOLCK (and generate a scary-looking
  * stack trace).
  *
  * The "priv" pointer is passed directly to the lm_setup function as-is. It
  * may be NULL if the lm_setup operation doesn't require it.
  */
 int
 vfs_setlease(struct file *filp, int arg, struct file_lease **lease, void **priv)
 {
         struct inode *inode = file_inode(filp);
         vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_idmap(filp), inode);
         int error;
 
         if ((!vfsuid_eq_kuid(vfsuid, current_fsuid())) && !capable(CAP_LEASE))
                 return -EACCES;
         if (!S_ISREG(inode->i_mode))
                 return -EINVAL;
         error = security_file_lock(filp, arg);
         if (error)
                 return error;
         return kernel_setlease(filp, arg, lease, priv);
 }
 EXPORT_SYMBOL_GPL(vfs_setlease);
 
 static int do_fcntl_add_lease(unsigned int fd, struct file *filp, int arg)
 {
         struct file_lease *fl;
         struct fasync_struct *new;
         int error;
 
         fl = lease_alloc(filp, arg);
         if (IS_ERR(fl))
                 return PTR_ERR(fl);
 
         new = fasync_alloc();
         if (!new) {
                 locks_free_lease(fl);
                 return -ENOMEM;
         }
         new->fa_fd = fd;
 
         error = vfs_setlease(filp, arg, &fl, (void **)&new);
         if (fl)
                 locks_free_lease(fl);
         if (new)
                 fasync_free(new);
         return error;
 }
 
 /**
  *      fcntl_setlease  -       sets a lease on an open file
  *      @fd: open file descriptor
  *      @filp: file pointer
  *      @arg: type of lease to obtain
  *
  *      Call this fcntl to establish a lease on the file.
  *      Note that you also need to call %F_SETSIG to
  *      receive a signal when the lease is broken.
  */
 int fcntl_setlease(unsigned int fd, struct file *filp, int arg)
 {
         if (arg == F_UNLCK)
                 return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
         return do_fcntl_add_lease(fd, filp, arg);
 }
 
 /**
  * flock_lock_inode_wait - Apply a FLOCK-style lock to a file
  * @inode: inode of the file to apply to
  * @fl: The lock to be applied
  *
  * Apply a FLOCK style lock request to an inode.
  */
 static int flock_lock_inode_wait(struct inode *inode, struct file_lock *fl)
 {
         int error;
         might_sleep();
         for (;;) {
                 error = flock_lock_inode(inode, fl);
                 if (error != FILE_LOCK_DEFERRED)
                         break;
                 error = wait_event_interruptible(fl->c.flc_wait,
                                                  list_empty(&fl->c.flc_blocked_member));
                 if (error)
                         break;
         }
         locks_delete_block(fl);
         return error;
 }
 
 /**
  * locks_lock_inode_wait - Apply a lock to an inode
  * @inode: inode of the file to apply to
  * @fl: The lock to be applied
  *
  * Apply a POSIX or FLOCK style lock request to an inode.
  */
 int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl)
 {
         int res = 0;
         switch (fl->c.flc_flags & (FL_POSIX|FL_FLOCK)) {
                 case FL_POSIX:
                         res = posix_lock_inode_wait(inode, fl);
                         break;
                 case FL_FLOCK:
                         res = flock_lock_inode_wait(inode, fl);
                         break;
                 default:
                         BUG();
         }
         return res;
 }
 EXPORT_SYMBOL(locks_lock_inode_wait);
 
 /**
  *      sys_flock: - flock() system call.
  *      @fd: the file descriptor to lock.
  *      @cmd: the type of lock to apply.
  *
  *      Apply a %FL_FLOCK style lock to an open file descriptor.
  *      The @cmd can be one of:
  *
  *      - %LOCK_SH -- a shared lock.
  *      - %LOCK_EX -- an exclusive lock.
  *      - %LOCK_UN -- remove an existing lock.
  *      - %LOCK_MAND -- a 'mandatory' flock. (DEPRECATED)
  *
  *      %LOCK_MAND support has been removed from the kernel.
  */
 SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
 {
         int can_sleep, error, type;
         struct file_lock fl;
         struct fd f;
 
         /*
          * LOCK_MAND locks were broken for a long time in that they never
          * conflicted with one another and didn't prevent any sort of open,
          * read or write activity.
          *
          * Just ignore these requests now, to preserve legacy behavior, but
          * throw a warning to let people know that they don't actually work.
          */
         if (cmd & LOCK_MAND) {
                 pr_warn_once("%s(%d): Attempt to set a LOCK_MAND lock via flock(2). This support has been removed and the request ignored.\n", current->comm, current->pid);
                 return 0;
         }
 
         type = flock_translate_cmd(cmd & ~LOCK_NB);
         if (type < 0)
                 return type;
 
         error = -EBADF;
         f = fdget(fd);
         if (!f.file)
                 return error;
 
         if (type != F_UNLCK && !(f.file->f_mode & (FMODE_READ | FMODE_WRITE)))
                 goto out_putf;
 
         flock_make_lock(f.file, &fl, type);
 
         error = security_file_lock(f.file, fl.c.flc_type);
         if (error)
                 goto out_putf;
 
         can_sleep = !(cmd & LOCK_NB);
         if (can_sleep)
                 fl.c.flc_flags |= FL_SLEEP;
 
         if (f.file->f_op->flock)
                 error = f.file->f_op->flock(f.file,
                                             (can_sleep) ? F_SETLKW : F_SETLK,
                                             &fl);
         else
                 error = locks_lock_file_wait(f.file, &fl);
 
         locks_release_private(&fl);
  out_putf:
         fdput(f);
 
         return error;
 }
 
 /**
  * vfs_test_lock - test file byte range lock
  * @filp: The file to test lock for
  * @fl: The lock to test; also used to hold result
  *
  * Returns -ERRNO on failure.  Indicates presence of conflicting lock by
  * setting conf->fl_type to something other than F_UNLCK.
  */
 int vfs_test_lock(struct file *filp, struct file_lock *fl)
 {
         WARN_ON_ONCE(filp != fl->c.flc_file);
         if (filp->f_op->lock)
                 return filp->f_op->lock(filp, F_GETLK, fl);
         posix_test_lock(filp, fl);
         return 0;
 }
 EXPORT_SYMBOL_GPL(vfs_test_lock);
 
 /**
  * locks_translate_pid - translate a file_lock's fl_pid number into a namespace
  * @fl: The file_lock who's fl_pid should be translated
  * @ns: The namespace into which the pid should be translated
  *
  * Used to translate a fl_pid into a namespace virtual pid number
  */
 static pid_t locks_translate_pid(struct file_lock_core *fl, struct pid_namespace *ns)
 {
         pid_t vnr;
         struct pid *pid;
 
         if (fl->flc_flags & FL_OFDLCK)
                 return -1;
 
         /* Remote locks report a negative pid value */
         if (fl->flc_pid <= 0)
                 return fl->flc_pid;
 
         /*
          * If the flock owner process is dead and its pid has been already
          * freed, the translation below won't work, but we still want to show
          * flock owner pid number in init pidns.
          */
         if (ns == &init_pid_ns)
                 return (pid_t) fl->flc_pid;
 
         rcu_read_lock();
         pid = find_pid_ns(fl->flc_pid, &init_pid_ns);
         vnr = pid_nr_ns(pid, ns);
         rcu_read_unlock();
         return vnr;
 }
 
 static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
 {
         flock->l_pid = locks_translate_pid(&fl->c, task_active_pid_ns(current));
 #if BITS_PER_LONG == 32
         /*
          * Make sure we can represent the posix lock via
          * legacy 32bit flock.
          */
         if (fl->fl_start > OFFT_OFFSET_MAX)
                 return -EOVERFLOW;
         if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
                 return -EOVERFLOW;
 #endif
         flock->l_start = fl->fl_start;
         flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
                 fl->fl_end - fl->fl_start + 1;
         flock->l_whence = 0;
         flock->l_type = fl->c.flc_type;
         return 0;
 }
 
 #if BITS_PER_LONG == 32
 static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
 {
         flock->l_pid = locks_translate_pid(&fl->c, task_active_pid_ns(current));
         flock->l_start = fl->fl_start;
         flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
                 fl->fl_end - fl->fl_start + 1;
         flock->l_whence = 0;
         flock->l_type = fl->c.flc_type;
 }
 #endif
 
 /* Report the first existing lock that would conflict with l.
  * This implements the F_GETLK command of fcntl().
  */
 int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
 {
         struct file_lock *fl;
         int error;
 
         fl = locks_alloc_lock();
         if (fl == NULL)
                 return -ENOMEM;
         error = -EINVAL;
         if (cmd != F_OFD_GETLK && flock->l_type != F_RDLCK
                         && flock->l_type != F_WRLCK)
                 goto out;
 
         error = flock_to_posix_lock(filp, fl, flock);
         if (error)
                 goto out;
 
         if (cmd == F_OFD_GETLK) {
                 error = -EINVAL;
                 if (flock->l_pid != 0)
                         goto out;
 
                 fl->c.flc_flags |= FL_OFDLCK;
                 fl->c.flc_owner = filp;
         }
 
         error = vfs_test_lock(filp, fl);
         if (error)
                 goto out;
 
         flock->l_type = fl->c.flc_type;
         if (fl->c.flc_type != F_UNLCK) {
                 error = posix_lock_to_flock(flock, fl);
                 if (error)
                         goto out;
         }
 out:
         locks_free_lock(fl);
         return error;
 }
 
 /**
  * vfs_lock_file - file byte range lock
  * @filp: The file to apply the lock to
  * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
  * @fl: The lock to be applied
  * @conf: Place to return a copy of the conflicting lock, if found.
  *
  * A caller that doesn't care about the conflicting lock may pass NULL
  * as the final argument.
  *
  * If the filesystem defines a private ->lock() method, then @conf will
  * be left unchanged; so a caller that cares should initialize it to
  * some acceptable default.
  *
  * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
  * locks, the ->lock() interface may return asynchronously, before the lock has
  * been granted or denied by the underlying filesystem, if (and only if)
  * lm_grant is set. Additionally EXPORT_OP_ASYNC_LOCK in export_operations
  * flags need to be set.
  *
  * Callers expecting ->lock() to return asynchronously will only use F_SETLK,
  * not F_SETLKW; they will set FL_SLEEP if (and only if) the request is for a
  * blocking lock. When ->lock() does return asynchronously, it must return
  * FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock request completes.
  * If the request is for non-blocking lock the file system should return
  * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
  * with the result. If the request timed out the callback routine will return a
  * nonzero return code and the file system should release the lock. The file
  * system is also responsible to keep a corresponding posix lock when it
  * grants a lock so the VFS can find out which locks are locally held and do
  * the correct lock cleanup when required.
  * The underlying filesystem must not drop the kernel lock or call
  * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
  * return code.
  */
 int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
 {
         WARN_ON_ONCE(filp != fl->c.flc_file);
         if (filp->f_op->lock)
                 return filp->f_op->lock(filp, cmd, fl);
         else
                 return posix_lock_file(filp, fl, conf);
 }
 EXPORT_SYMBOL_GPL(vfs_lock_file);
 
 static int do_lock_file_wait(struct file *filp, unsigned int cmd,
                              struct file_lock *fl)
 {
         int error;
 
         error = security_file_lock(filp, fl->c.flc_type);
         if (error)
                 return error;
 
         for (;;) {
                 error = vfs_lock_file(filp, cmd, fl, NULL);
                 if (error != FILE_LOCK_DEFERRED)
                         break;
                 error = wait_event_interruptible(fl->c.flc_wait,
                                                  list_empty(&fl->c.flc_blocked_member));
                 if (error)
                         break;
         }
         locks_delete_block(fl);
 
         return error;
 }
 
 /* Ensure that fl->fl_file has compatible f_mode for F_SETLK calls */
 static int
 check_fmode_for_setlk(struct file_lock *fl)
 {
         switch (fl->c.flc_type) {
         case F_RDLCK:
                 if (!(fl->c.flc_file->f_mode & FMODE_READ))
                         return -EBADF;
                 break;
         case F_WRLCK:
                 if (!(fl->c.flc_file->f_mode & FMODE_WRITE))
                         return -EBADF;
         }
         return 0;
 }
 
 /* Apply the lock described by l to an open file descriptor.
  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
  */
 int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
                 struct flock *flock)
 {
         struct file_lock *file_lock = locks_alloc_lock();
         struct inode *inode = file_inode(filp);
         struct file *f;
         int error;
 
         if (file_lock == NULL)
                 return -ENOLCK;
 
         error = flock_to_posix_lock(filp, file_lock, flock);
         if (error)
                 goto out;
 
         error = check_fmode_for_setlk(file_lock);
         if (error)
                 goto out;
 
         /*
          * If the cmd is requesting file-private locks, then set the
          * FL_OFDLCK flag and override the owner.
          */
         switch (cmd) {
         case F_OFD_SETLK:
                 error = -EINVAL;
                 if (flock->l_pid != 0)
                         goto out;
 
                 cmd = F_SETLK;
                 file_lock->c.flc_flags |= FL_OFDLCK;
                 file_lock->c.flc_owner = filp;
                 break;
         case F_OFD_SETLKW:
                 error = -EINVAL;
                 if (flock->l_pid != 0)
                         goto out;
 
                 cmd = F_SETLKW;
                 file_lock->c.flc_flags |= FL_OFDLCK;
                 file_lock->c.flc_owner = filp;
                 fallthrough;
         case F_SETLKW:
                 file_lock->c.flc_flags |= FL_SLEEP;
         }
 
         error = do_lock_file_wait(filp, cmd, file_lock);
 
         /*
          * Detect close/fcntl races and recover by zapping all POSIX locks
          * associated with this file and our files_struct, just like on
          * filp_flush(). There is no need to do that when we're
          * unlocking though, or for OFD locks.
          */
         if (!error && file_lock->c.flc_type != F_UNLCK &&
             !(file_lock->c.flc_flags & FL_OFDLCK)) {
                 struct files_struct *files = current->files;
                 /*
                  * We need that spin_lock here - it prevents reordering between
                  * update of i_flctx->flc_posix and check for it done in
                  * close(). rcu_read_lock() wouldn't do.
                  */
                 spin_lock(&files->file_lock);
                 f = files_lookup_fd_locked(files, fd);
                 spin_unlock(&files->file_lock);
                 if (f != filp) {
                         locks_remove_posix(filp, files);
                         error = -EBADF;
                 }
         }
 out:
         trace_fcntl_setlk(inode, file_lock, error);
         locks_free_lock(file_lock);
         return error;
 }
 
 #if BITS_PER_LONG == 32
 /* Report the first existing lock that would conflict with l.
  * This implements the F_GETLK command of fcntl().
  */
 int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
 {
         struct file_lock *fl;
         int error;
 
         fl = locks_alloc_lock();
         if (fl == NULL)
                 return -ENOMEM;
 
         error = -EINVAL;
         if (cmd != F_OFD_GETLK && flock->l_type != F_RDLCK
                         && flock->l_type != F_WRLCK)
                 goto out;
 
         error = flock64_to_posix_lock(filp, fl, flock);
         if (error)
                 goto out;
 
         if (cmd == F_OFD_GETLK) {
                 error = -EINVAL;
                 if (flock->l_pid != 0)
                         goto out;
 
                 fl->c.flc_flags |= FL_OFDLCK;
                 fl->c.flc_owner = filp;
         }
 
         error = vfs_test_lock(filp, fl);
         if (error)
                 goto out;
 
         flock->l_type = fl->c.flc_type;
         if (fl->c.flc_type != F_UNLCK)
                 posix_lock_to_flock64(flock, fl);
 
 out:
         locks_free_lock(fl);
         return error;
 }
 
 /* Apply the lock described by l to an open file descriptor.
  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
  */
 int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
                 struct flock64 *flock)
 {
         struct file_lock *file_lock = locks_alloc_lock();
         struct file *f;
         int error;
 
         if (file_lock == NULL)
                 return -ENOLCK;
 
         error = flock64_to_posix_lock(filp, file_lock, flock);
         if (error)
                 goto out;
 
         error = check_fmode_for_setlk(file_lock);
         if (error)
                 goto out;
 
         /*
          * If the cmd is requesting file-private locks, then set the
          * FL_OFDLCK flag and override the owner.
          */
         switch (cmd) {
         case F_OFD_SETLK:
                 error = -EINVAL;
                 if (flock->l_pid != 0)
                         goto out;
 
                 cmd = F_SETLK64;
                 file_lock->c.flc_flags |= FL_OFDLCK;
                 file_lock->c.flc_owner = filp;
                 break;
         case F_OFD_SETLKW:
                 error = -EINVAL;
                 if (flock->l_pid != 0)
                         goto out;
 
                 cmd = F_SETLKW64;
                 file_lock->c.flc_flags |= FL_OFDLCK;
                 file_lock->c.flc_owner = filp;
                 fallthrough;
         case F_SETLKW64:
                 file_lock->c.flc_flags |= FL_SLEEP;
         }
 
         error = do_lock_file_wait(filp, cmd, file_lock);
 
         /*
          * Detect close/fcntl races and recover by zapping all POSIX locks
          * associated with this file and our files_struct, just like on
          * filp_flush(). There is no need to do that when we're
          * unlocking though, or for OFD locks.
          */
         if (!error && file_lock->c.flc_type != F_UNLCK &&
             !(file_lock->c.flc_flags & FL_OFDLCK)) {
                 struct files_struct *files = current->files;
                 /*
                  * We need that spin_lock here - it prevents reordering between
                  * update of i_flctx->flc_posix and check for it done in
                  * close(). rcu_read_lock() wouldn't do.
                  */
                 spin_lock(&files->file_lock);
                 f = files_lookup_fd_locked(files, fd);
                 spin_unlock(&files->file_lock);
                 if (f != filp) {
                         locks_remove_posix(filp, files);
                         error = -EBADF;
                 }
         }
 out:
         locks_free_lock(file_lock);
         return error;
 }
 #endif /* BITS_PER_LONG == 32 */
 
 /*
  * This function is called when the file is being removed
  * from the task's fd array.  POSIX locks belonging to this task
  * are deleted at this time.
  */
 void locks_remove_posix(struct file *filp, fl_owner_t owner)
 {
         int error;
         struct inode *inode = file_inode(filp);
         struct file_lock lock;
         struct file_lock_context *ctx;
 
         /*
          * If there are no locks held on this file, we don't need to call
          * posix_lock_file().  Another process could be setting a lock on this
          * file at the same time, but we wouldn't remove that lock anyway.
          */
         ctx = locks_inode_context(inode);
         if (!ctx || list_empty(&ctx->flc_posix))
                 return;
 
         locks_init_lock(&lock);
         lock.c.flc_type = F_UNLCK;
         lock.c.flc_flags = FL_POSIX | FL_CLOSE;
         lock.fl_start = 0;
         lock.fl_end = OFFSET_MAX;
         lock.c.flc_owner = owner;
         lock.c.flc_pid = current->tgid;
         lock.c.flc_file = filp;
         lock.fl_ops = NULL;
         lock.fl_lmops = NULL;
 
         error = vfs_lock_file(filp, F_SETLK, &lock, NULL);
 
         if (lock.fl_ops && lock.fl_ops->fl_release_private)
                 lock.fl_ops->fl_release_private(&lock);
         trace_locks_remove_posix(inode, &lock, error);
 }
 EXPORT_SYMBOL(locks_remove_posix);
 
 /* The i_flctx must be valid when calling into here */
 static void
 locks_remove_flock(struct file *filp, struct file_lock_context *flctx)
 {
         struct file_lock fl;
         struct inode *inode = file_inode(filp);
 
         if (list_empty(&flctx->flc_flock))
                 return;
 
         flock_make_lock(filp, &fl, F_UNLCK);
         fl.c.flc_flags |= FL_CLOSE;
 
         if (filp->f_op->flock)
                 filp->f_op->flock(filp, F_SETLKW, &fl);
         else
                 flock_lock_inode(inode, &fl);
 
         if (fl.fl_ops && fl.fl_ops->fl_release_private)
                 fl.fl_ops->fl_release_private(&fl);
 }
 
 /* The i_flctx must be valid when calling into here */
 static void
 locks_remove_lease(struct file *filp, struct file_lock_context *ctx)
 {
         struct file_lease *fl, *tmp;
         LIST_HEAD(dispose);
 
         if (list_empty(&ctx->flc_lease))
                 return;
 
         percpu_down_read(&file_rwsem);
         spin_lock(&ctx->flc_lock);
         list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, c.flc_list)
                 if (filp == fl->c.flc_file)
                         lease_modify(fl, F_UNLCK, &dispose);
         spin_unlock(&ctx->flc_lock);
         percpu_up_read(&file_rwsem);
 
         locks_dispose_list(&dispose);
 }
 
 /*
  * This function is called on the last close of an open file.
  */
 void locks_remove_file(struct file *filp)
 {
         struct file_lock_context *ctx;
 
         ctx = locks_inode_context(file_inode(filp));
         if (!ctx)
                 return;
 
         /* remove any OFD locks */
         locks_remove_posix(filp, filp);
 
         /* remove flock locks */
         locks_remove_flock(filp, ctx);
 
         /* remove any leases */
         locks_remove_lease(filp, ctx);
 
         spin_lock(&ctx->flc_lock);
         locks_check_ctx_file_list(filp, &ctx->flc_posix, "POSIX");
         locks_check_ctx_file_list(filp, &ctx->flc_flock, "FLOCK");
         locks_check_ctx_file_list(filp, &ctx->flc_lease, "LEASE");
         spin_unlock(&ctx->flc_lock);
 }
 
 /**
  * vfs_cancel_lock - file byte range unblock lock
  * @filp: The file to apply the unblock to
  * @fl: The lock to be unblocked
  *
  * Used by lock managers to cancel blocked requests
  */
 int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
 {
         WARN_ON_ONCE(filp != fl->c.flc_file);
         if (filp->f_op->lock)
                 return filp->f_op->lock(filp, F_CANCELLK, fl);
         return 0;
 }
 EXPORT_SYMBOL_GPL(vfs_cancel_lock);
 
 /**
  * vfs_inode_has_locks - are any file locks held on @inode?
  * @inode: inode to check for locks
  *
  * Return true if there are any FL_POSIX or FL_FLOCK locks currently
  * set on @inode.
  */
 bool vfs_inode_has_locks(struct inode *inode)
 {
         struct file_lock_context *ctx;
         bool ret;
 
         ctx = locks_inode_context(inode);
         if (!ctx)
                 return false;
 
         spin_lock(&ctx->flc_lock);
         ret = !list_empty(&ctx->flc_posix) || !list_empty(&ctx->flc_flock);
         spin_unlock(&ctx->flc_lock);
         return ret;
 }
 EXPORT_SYMBOL_GPL(vfs_inode_has_locks);
 
 #ifdef CONFIG_PROC_FS
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 
 struct locks_iterator {
         int     li_cpu;
         loff_t  li_pos;
 };
 
 static void lock_get_status(struct seq_file *f, struct file_lock_core *flc,
                             loff_t id, char *pfx, int repeat)
 {
         struct inode *inode = NULL;
         unsigned int pid;
         struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
         int type = flc->flc_type;
         struct file_lock *fl = file_lock(flc);
 
         pid = locks_translate_pid(flc, proc_pidns);
 
         /*
          * If lock owner is dead (and pid is freed) or not visible in current
          * pidns, zero is shown as a pid value. Check lock info from
          * init_pid_ns to get saved lock pid value.
          */
         if (flc->flc_file != NULL)
                 inode = file_inode(flc->flc_file);
 
         seq_printf(f, "%lld: ", id);
 
         if (repeat)
                 seq_printf(f, "%*s", repeat - 1 + (int)strlen(pfx), pfx);
 
         if (flc->flc_flags & FL_POSIX) {
                 if (flc->flc_flags & FL_ACCESS)
                         seq_puts(f, "ACCESS");
                 else if (flc->flc_flags & FL_OFDLCK)
                         seq_puts(f, "OFDLCK");
                 else
                         seq_puts(f, "POSIX ");
 
                 seq_printf(f, " %s ",
                              (inode == NULL) ? "*NOINODE*" : "ADVISORY ");
         } else if (flc->flc_flags & FL_FLOCK) {
                 seq_puts(f, "FLOCK  ADVISORY  ");
         } else if (flc->flc_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT)) {
                 struct file_lease *lease = file_lease(flc);
 
                 type = target_leasetype(lease);
 
                 if (flc->flc_flags & FL_DELEG)
                         seq_puts(f, "DELEG  ");
                 else
                         seq_puts(f, "LEASE  ");
 
                 if (lease_breaking(lease))
                         seq_puts(f, "BREAKING  ");
                 else if (flc->flc_file)
                         seq_puts(f, "ACTIVE    ");
                 else
                         seq_puts(f, "BREAKER   ");
         } else {
                 seq_puts(f, "UNKNOWN UNKNOWN  ");
         }
 
         seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" :
                              (type == F_RDLCK) ? "READ" : "UNLCK");
         if (inode) {
                 /* userspace relies on this representation of dev_t */
                 seq_printf(f, "%d %02x:%02x:%lu ", pid,
                                 MAJOR(inode->i_sb->s_dev),
                                 MINOR(inode->i_sb->s_dev), inode->i_ino);
         } else {
                 seq_printf(f, "%d <none>:0 ", pid);
         }
         if (flc->flc_flags & FL_POSIX) {
                 if (fl->fl_end == OFFSET_MAX)
                         seq_printf(f, "%Ld EOF\n", fl->fl_start);
                 else
                         seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
         } else {
                 seq_puts(f, "0 EOF\n");
         }
 }
 
 static struct file_lock_core *get_next_blocked_member(struct file_lock_core *node)
 {
         struct file_lock_core *tmp;
 
         /* NULL node or root node */
         if (node == NULL || node->flc_blocker == NULL)
                 return NULL;
 
         /* Next member in the linked list could be itself */
         tmp = list_next_entry(node, flc_blocked_member);
         if (list_entry_is_head(tmp, &node->flc_blocker->flc_blocked_requests,
                                flc_blocked_member)
                 || tmp == node) {
                 return NULL;
         }
 
         return tmp;
 }
 
 static int locks_show(struct seq_file *f, void *v)
 {
         struct locks_iterator *iter = f->private;
         struct file_lock_core *cur, *tmp;
         struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
         int level = 0;
 
         cur = hlist_entry(v, struct file_lock_core, flc_link);
 
         if (locks_translate_pid(cur, proc_pidns) == 0)
                 return 0;
 
         /* View this crossed linked list as a binary tree, the first member of flc_blocked_requests
          * is the left child of current node, the next silibing in flc_blocked_member is the
          * right child, we can alse get the parent of current node from flc_blocker, so this
          * question becomes traversal of a binary tree
          */
         while (cur != NULL) {
                 if (level)
                         lock_get_status(f, cur, iter->li_pos, "-> ", level);
                 else
                         lock_get_status(f, cur, iter->li_pos, "", level);
 
                 if (!list_empty(&cur->flc_blocked_requests)) {
                         /* Turn left */
                         cur = list_first_entry_or_null(&cur->flc_blocked_requests,
                                                        struct file_lock_core,
                                                        flc_blocked_member);
                         level++;
                 } else {
                         /* Turn right */
                         tmp = get_next_blocked_member(cur);
                         /* Fall back to parent node */
                         while (tmp == NULL && cur->flc_blocker != NULL) {
                                 cur = cur->flc_blocker;
                                 level--;
                                 tmp = get_next_blocked_member(cur);
                         }
                         cur = tmp;
                 }
         }
 
         return 0;
 }
 
 static void __show_fd_locks(struct seq_file *f,
                         struct list_head *head, int *id,
                         struct file *filp, struct files_struct *files)
 {
         struct file_lock_core *fl;
 
         list_for_each_entry(fl, head, flc_list) {
 
                 if (filp != fl->flc_file)
                         continue;
                 if (fl->flc_owner != files && fl->flc_owner != filp)
                         continue;
 
                 (*id)++;
                 seq_puts(f, "lock:\t");
                 lock_get_status(f, fl, *id, "", 0);
         }
 }
 
 void show_fd_locks(struct seq_file *f,
                   struct file *filp, struct files_struct *files)
 {
         struct inode *inode = file_inode(filp);
         struct file_lock_context *ctx;
         int id = 0;
 
         ctx = locks_inode_context(inode);
         if (!ctx)
                 return;
 
         spin_lock(&ctx->flc_lock);
         __show_fd_locks(f, &ctx->flc_flock, &id, filp, files);
         __show_fd_locks(f, &ctx->flc_posix, &id, filp, files);
         __show_fd_locks(f, &ctx->flc_lease, &id, filp, files);
         spin_unlock(&ctx->flc_lock);
 }
 
 static void *locks_start(struct seq_file *f, loff_t *pos)
         __acquires(&blocked_lock_lock)
 {
         struct locks_iterator *iter = f->private;
 
         iter->li_pos = *pos + 1;
         percpu_down_write(&file_rwsem);
         spin_lock(&blocked_lock_lock);
         return seq_hlist_start_percpu(&file_lock_list.hlist, &iter->li_cpu, *pos);
 }
 
 static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
 {
         struct locks_iterator *iter = f->private;
 
         ++iter->li_pos;
         return seq_hlist_next_percpu(v, &file_lock_list.hlist, &iter->li_cpu, pos);
 }
 
 static void locks_stop(struct seq_file *f, void *v)
         __releases(&blocked_lock_lock)
 {
         spin_unlock(&blocked_lock_lock);
         percpu_up_write(&file_rwsem);
 }
 
 static const struct seq_operations locks_seq_operations = {
         .start  = locks_start,
         .next   = locks_next,
         .stop   = locks_stop,
         .show   = locks_show,
 };
 
 static int __init proc_locks_init(void)
 {
         proc_create_seq_private("locks", 0, NULL, &locks_seq_operations,
                         sizeof(struct locks_iterator), NULL);
         return 0;
 }
 fs_initcall(proc_locks_init);
 #endif
 
 static int __init filelock_init(void)
 {
         int i;
 
         flctx_cache = kmem_cache_create("file_lock_ctx",
                         sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL);
 
         filelock_cache = kmem_cache_create("file_lock_cache",
                         sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
 
         filelease_cache = kmem_cache_create("file_lease_cache",
                         sizeof(struct file_lease), 0, SLAB_PANIC, NULL);
 
         for_each_possible_cpu(i) {
                 struct file_lock_list_struct *fll = per_cpu_ptr(&file_lock_list, i);
 
                 spin_lock_init(&fll->lock);
                 INIT_HLIST_HEAD(&fll->hlist);
         }
 
         lease_notifier_chain_init();
         return 0;
 }
 core_initcall(filelock_init);
 

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