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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
  * All Rights Reserved.
  */
 #include "xfs.h"
 #include "xfs_fs.h"
 #include "xfs_shared.h"
 #include "xfs_format.h"
 #include "xfs_log_format.h"
 #include "xfs_trans_resv.h"
 #include "xfs_mount.h"
 #include "xfs_inode.h"
 #include "xfs_trans.h"
 #include "xfs_trans_priv.h"
 #include "xfs_inode_item.h"
 #include "xfs_quota.h"
 #include "xfs_trace.h"
 #include "xfs_icache.h"
 #include "xfs_bmap_util.h"
 #include "xfs_dquot_item.h"
 #include "xfs_dquot.h"
 #include "xfs_reflink.h"
 #include "xfs_ialloc.h"
 #include "xfs_ag.h"
 #include "xfs_log_priv.h"
 
 #include <linux/iversion.h>
 
 /* Radix tree tags for incore inode tree. */
 
 /* inode is to be reclaimed */
 #define XFS_ICI_RECLAIM_TAG 0
 /* Inode has speculative preallocations (posteof or cow) to clean. */
 #define XFS_ICI_BLOCKGC_TAG 1
 
 /*
  * The goal for walking incore inodes.  These can correspond with incore inode
  * radix tree tags when convenient.  Avoid existing XFS_IWALK namespace.
  */
 enum xfs_icwalk_goal {
     /* Goals directly associated with tagged inodes. */
     XFS_ICWALK_BLOCKGC  = XFS_ICI_BLOCKGC_TAG,
     XFS_ICWALK_RECLAIM  = XFS_ICI_RECLAIM_TAG,
 };
 
 static int xfs_icwalk(struct xfs_mount *mp,
         enum xfs_icwalk_goal goal, struct xfs_icwalk *icw);
 static int xfs_icwalk_ag(struct xfs_perag *pag,
         enum xfs_icwalk_goal goal, struct xfs_icwalk *icw);
 
 /*
  * Private inode cache walk flags for struct xfs_icwalk.  Must not
  * coincide with XFS_ICWALK_FLAGS_VALID.
  */
 
 /* Stop scanning after icw_scan_limit inodes. */
 #define XFS_ICWALK_FLAG_SCAN_LIMIT  (1U << 28)
 
 #define XFS_ICWALK_FLAG_RECLAIM_SICK    (1U << 27)
 #define XFS_ICWALK_FLAG_UNION       (1U << 26) /* union filter algorithm */
 
 #define XFS_ICWALK_PRIVATE_FLAGS    (XFS_ICWALK_FLAG_SCAN_LIMIT | \
                      XFS_ICWALK_FLAG_RECLAIM_SICK | \
                      XFS_ICWALK_FLAG_UNION)
 
 /*
  * Allocate and initialise an xfs_inode.
  */
 struct xfs_inode *
 xfs_inode_alloc(
     struct xfs_mount    *mp,
     xfs_ino_t       ino)
 {
     struct xfs_inode    *ip;
 
     /*
      * XXX: If this didn't occur in transactions, we could drop GFP_NOFAIL
      * and return NULL here on ENOMEM.
      */
     ip = alloc_inode_sb(mp->m_super, xfs_inode_cache, GFP_KERNEL | __GFP_NOFAIL);
 
     if (inode_init_always(mp->m_super, VFS_I(ip))) {
         kmem_cache_free(xfs_inode_cache, ip);
         return NULL;
     }
 
     /* VFS doesn't initialise i_mode or i_state! */
     VFS_I(ip)->i_mode = 0;
     VFS_I(ip)->i_state = 0;
     mapping_set_large_folios(VFS_I(ip)->i_mapping);
 
     XFS_STATS_INC(mp, vn_active);
     ASSERT(atomic_read(&ip->i_pincount) == 0);
     ASSERT(ip->i_ino == 0);
 
     /* initialise the xfs inode */
     ip->i_ino = ino;
     ip->i_mount = mp;
     memset(&ip->i_imap, 0, sizeof(struct xfs_imap));
     ip->i_cowfp = NULL;
     memset(&ip->i_af, 0, sizeof(ip->i_af));
     ip->i_af.if_format = XFS_DINODE_FMT_EXTENTS;
     memset(&ip->i_df, 0, sizeof(ip->i_df));
     ip->i_flags = 0;
     ip->i_delayed_blks = 0;
     ip->i_diflags2 = mp->m_ino_geo.new_diflags2;
     ip->i_nblocks = 0;
     ip->i_forkoff = 0;
     ip->i_sick = 0;
     ip->i_checked = 0;
     INIT_WORK(&ip->i_ioend_work, xfs_end_io);
     INIT_LIST_HEAD(&ip->i_ioend_list);
     spin_lock_init(&ip->i_ioend_lock);
     ip->i_next_unlinked = NULLAGINO;
     ip->i_prev_unlinked = NULLAGINO;
 
     return ip;
 }
 
 STATIC void
 xfs_inode_free_callback(
     struct rcu_head     *head)
 {
     struct inode        *inode = container_of(head, struct inode, i_rcu);
     struct xfs_inode    *ip = XFS_I(inode);
 
     switch (VFS_I(ip)->i_mode & S_IFMT) {
     case S_IFREG:
     case S_IFDIR:
     case S_IFLNK:
         xfs_idestroy_fork(&ip->i_df);
         break;
     }
 
     xfs_ifork_zap_attr(ip);
 
     if (ip->i_cowfp) {
         xfs_idestroy_fork(ip->i_cowfp);
         kmem_cache_free(xfs_ifork_cache, ip->i_cowfp);
     }
     if (ip->i_itemp) {
         ASSERT(!test_bit(XFS_LI_IN_AIL,
                  &ip->i_itemp->ili_item.li_flags));
         xfs_inode_item_destroy(ip);
         ip->i_itemp = NULL;
     }
 
     kmem_cache_free(xfs_inode_cache, ip);
 }
 
 static void
 __xfs_inode_free(
     struct xfs_inode    *ip)
 {
     /* asserts to verify all state is correct here */
     ASSERT(atomic_read(&ip->i_pincount) == 0);
     ASSERT(!ip->i_itemp || list_empty(&ip->i_itemp->ili_item.li_bio_list));
     XFS_STATS_DEC(ip->i_mount, vn_active);
 
     call_rcu(&VFS_I(ip)->i_rcu, xfs_inode_free_callback);
 }
 
 void
 xfs_inode_free(
     struct xfs_inode    *ip)
 {
     ASSERT(!xfs_iflags_test(ip, XFS_IFLUSHING));
 
     /*
      * Because we use RCU freeing we need to ensure the inode always
      * appears to be reclaimed with an invalid inode number when in the
      * free state. The ip->i_flags_lock provides the barrier against lookup
      * races.
      */
     spin_lock(&ip->i_flags_lock);
     ip->i_flags = XFS_IRECLAIM;
     ip->i_ino = 0;
     spin_unlock(&ip->i_flags_lock);
 
     __xfs_inode_free(ip);
 }
 
 /*
  * Queue background inode reclaim work if there are reclaimable inodes and there
  * isn't reclaim work already scheduled or in progress.
  */
 static void
 xfs_reclaim_work_queue(
     struct xfs_mount        *mp)
 {
 
     rcu_read_lock();
     if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
         queue_delayed_work(mp->m_reclaim_workqueue, &mp->m_reclaim_work,
             msecs_to_jiffies(xfs_syncd_centisecs / 6 * 10));
     }
     rcu_read_unlock();
 }
 
 /*
  * Background scanning to trim preallocated space. This is queued based on the
  * 'speculative_prealloc_lifetime' tunable (5m by default).
  */
 static inline void
 xfs_blockgc_queue(
     struct xfs_perag    *pag)
 {
     struct xfs_mount    *mp = pag->pag_mount;
 
     if (!xfs_is_blockgc_enabled(mp))
         return;
 
     rcu_read_lock();
     if (radix_tree_tagged(&pag->pag_ici_root, XFS_ICI_BLOCKGC_TAG))
         queue_delayed_work(pag->pag_mount->m_blockgc_wq,
                    &pag->pag_blockgc_work,
                    msecs_to_jiffies(xfs_blockgc_secs * 1000));
     rcu_read_unlock();
 }
 
 /* Set a tag on both the AG incore inode tree and the AG radix tree. */
 static void
 xfs_perag_set_inode_tag(
     struct xfs_perag    *pag,
     xfs_agino_t     agino,
     unsigned int        tag)
 {
     struct xfs_mount    *mp = pag->pag_mount;
     bool            was_tagged;
 
     lockdep_assert_held(&pag->pag_ici_lock);
 
     was_tagged = radix_tree_tagged(&pag->pag_ici_root, tag);
     radix_tree_tag_set(&pag->pag_ici_root, agino, tag);
 
     if (tag == XFS_ICI_RECLAIM_TAG)
         pag->pag_ici_reclaimable++;
 
     if (was_tagged)
         return;
 
     /* propagate the tag up into the perag radix tree */
     spin_lock(&mp->m_perag_lock);
     radix_tree_tag_set(&mp->m_perag_tree, pag->pag_agno, tag);
     spin_unlock(&mp->m_perag_lock);
 
     /* start background work */
     switch (tag) {
     case XFS_ICI_RECLAIM_TAG:
         xfs_reclaim_work_queue(mp);
         break;
     case XFS_ICI_BLOCKGC_TAG:
         xfs_blockgc_queue(pag);
         break;
     }
 
     trace_xfs_perag_set_inode_tag(mp, pag->pag_agno, tag, _RET_IP_);
 }
 
 /* Clear a tag on both the AG incore inode tree and the AG radix tree. */
 static void
 xfs_perag_clear_inode_tag(
     struct xfs_perag    *pag,
     xfs_agino_t     agino,
     unsigned int        tag)
 {
     struct xfs_mount    *mp = pag->pag_mount;
 
     lockdep_assert_held(&pag->pag_ici_lock);
 
     /*
      * Reclaim can signal (with a null agino) that it cleared its own tag
      * by removing the inode from the radix tree.
      */
     if (agino != NULLAGINO)
         radix_tree_tag_clear(&pag->pag_ici_root, agino, tag);
     else
         ASSERT(tag == XFS_ICI_RECLAIM_TAG);
 
     if (tag == XFS_ICI_RECLAIM_TAG)
         pag->pag_ici_reclaimable--;
 
     if (radix_tree_tagged(&pag->pag_ici_root, tag))
         return;
 
     /* clear the tag from the perag radix tree */
     spin_lock(&mp->m_perag_lock);
     radix_tree_tag_clear(&mp->m_perag_tree, pag->pag_agno, tag);
     spin_unlock(&mp->m_perag_lock);
 
     trace_xfs_perag_clear_inode_tag(mp, pag->pag_agno, tag, _RET_IP_);
 }
 
 /*
  * When we recycle a reclaimable inode, we need to re-initialise the VFS inode
  * part of the structure. This is made more complex by the fact we store
  * information about the on-disk values in the VFS inode and so we can't just
  * overwrite the values unconditionally. Hence we save the parameters we
  * need to retain across reinitialisation, and rewrite them into the VFS inode
  * after reinitialisation even if it fails.
  */
 static int
 xfs_reinit_inode(
     struct xfs_mount    *mp,
     struct inode        *inode)
 {
     int         error;
     uint32_t        nlink = inode->i_nlink;
     uint32_t        generation = inode->i_generation;
     uint64_t        version = inode_peek_iversion(inode);
     umode_t         mode = inode->i_mode;
     dev_t           dev = inode->i_rdev;
     kuid_t          uid = inode->i_uid;
     kgid_t          gid = inode->i_gid;
 
     error = inode_init_always(mp->m_super, inode);
 
     set_nlink(inode, nlink);
     inode->i_generation = generation;
     inode_set_iversion_queried(inode, version);
     inode->i_mode = mode;
     inode->i_rdev = dev;
     inode->i_uid = uid;
     inode->i_gid = gid;
     mapping_set_large_folios(inode->i_mapping);
     return error;
 }
 
 /*
  * Carefully nudge an inode whose VFS state has been torn down back into a
  * usable state.  Drops the i_flags_lock and the rcu read lock.
  */
 static int
 xfs_iget_recycle(
     struct xfs_perag    *pag,
     struct xfs_inode    *ip) __releases(&ip->i_flags_lock)
 {
     struct xfs_mount    *mp = ip->i_mount;
     struct inode        *inode = VFS_I(ip);
     int         error;
 
     trace_xfs_iget_recycle(ip);
 
     /*
      * We need to make it look like the inode is being reclaimed to prevent
      * the actual reclaim workers from stomping over us while we recycle
      * the inode.  We can't clear the radix tree tag yet as it requires
      * pag_ici_lock to be held exclusive.
      */
     ip->i_flags |= XFS_IRECLAIM;
 
     spin_unlock(&ip->i_flags_lock);
     rcu_read_unlock();
 
     ASSERT(!rwsem_is_locked(&inode->i_rwsem));
     error = xfs_reinit_inode(mp, inode);
     if (error) {
         /*
          * Re-initializing the inode failed, and we are in deep
          * trouble.  Try to re-add it to the reclaim list.
          */
         rcu_read_lock();
         spin_lock(&ip->i_flags_lock);
         ip->i_flags &= ~(XFS_INEW | XFS_IRECLAIM);
         ASSERT(ip->i_flags & XFS_IRECLAIMABLE);
         spin_unlock(&ip->i_flags_lock);
         rcu_read_unlock();
 
         trace_xfs_iget_recycle_fail(ip);
         return error;
     }
 
     spin_lock(&pag->pag_ici_lock);
     spin_lock(&ip->i_flags_lock);
 
     /*
      * Clear the per-lifetime state in the inode as we are now effectively
      * a new inode and need to return to the initial state before reuse
      * occurs.
      */
     ip->i_flags &= ~XFS_IRECLAIM_RESET_FLAGS;
     ip->i_flags |= XFS_INEW;
     xfs_perag_clear_inode_tag(pag, XFS_INO_TO_AGINO(mp, ip->i_ino),
             XFS_ICI_RECLAIM_TAG);
     inode->i_state = I_NEW;
     spin_unlock(&ip->i_flags_lock);
     spin_unlock(&pag->pag_ici_lock);
 
     return 0;
 }
 
 /*
  * If we are allocating a new inode, then check what was returned is
  * actually a free, empty inode. If we are not allocating an inode,
  * then check we didn't find a free inode.
  *
  * Returns:
  *  0       if the inode free state matches the lookup context
  *  -ENOENT     if the inode is free and we are not allocating
  *  -EFSCORRUPTED   if there is any state mismatch at all
  */
 static int
 xfs_iget_check_free_state(
     struct xfs_inode    *ip,
     int         flags)
 {
     if (flags & XFS_IGET_CREATE) {
         /* should be a free inode */
         if (VFS_I(ip)->i_mode != 0) {
             xfs_warn(ip->i_mount,
 "Corruption detected! Free inode 0x%llx not marked free! (mode 0x%x)",
                 ip->i_ino, VFS_I(ip)->i_mode);
             return -EFSCORRUPTED;
         }
 
         if (ip->i_nblocks != 0) {
             xfs_warn(ip->i_mount,
 "Corruption detected! Free inode 0x%llx has blocks allocated!",
                 ip->i_ino);
             return -EFSCORRUPTED;
         }
         return 0;
     }
 
     /* should be an allocated inode */
     if (VFS_I(ip)->i_mode == 0)
         return -ENOENT;
 
     return 0;
 }
 
 /* Make all pending inactivation work start immediately. */
 static void
 xfs_inodegc_queue_all(
     struct xfs_mount    *mp)
 {
     struct xfs_inodegc  *gc;
     int         cpu;
 
     for_each_online_cpu(cpu) {
         gc = per_cpu_ptr(mp->m_inodegc, cpu);
         if (!llist_empty(&gc->list))
             mod_delayed_work_on(cpu, mp->m_inodegc_wq, &gc->work, 0);
     }
 }
 
 /*
  * Check the validity of the inode we just found it the cache
  */
 static int
 xfs_iget_cache_hit(
     struct xfs_perag    *pag,
     struct xfs_inode    *ip,
     xfs_ino_t       ino,
     int         flags,
     int         lock_flags) __releases(RCU)
 {
     struct inode        *inode = VFS_I(ip);
     struct xfs_mount    *mp = ip->i_mount;
     int         error;
 
     /*
      * check for re-use of an inode within an RCU grace period due to the
      * radix tree nodes not being updated yet. We monitor for this by
      * setting the inode number to zero before freeing the inode structure.
      * If the inode has been reallocated and set up, then the inode number
      * will not match, so check for that, too.
      */
     spin_lock(&ip->i_flags_lock);
     if (ip->i_ino != ino)
         goto out_skip;
 
     /*
      * If we are racing with another cache hit that is currently
      * instantiating this inode or currently recycling it out of
      * reclaimable state, wait for the initialisation to complete
      * before continuing.
      *
      * If we're racing with the inactivation worker we also want to wait.
      * If we're creating a new file, it's possible that the worker
      * previously marked the inode as free on disk but hasn't finished
      * updating the incore state yet.  The AGI buffer will be dirty and
      * locked to the icreate transaction, so a synchronous push of the
      * inodegc workers would result in deadlock.  For a regular iget, the
      * worker is running already, so we might as well wait.
      *
      * XXX(hch): eventually we should do something equivalent to
      *       wait_on_inode to wait for these flags to be cleared
      *       instead of polling for it.
      */
     if (ip->i_flags & (XFS_INEW | XFS_IRECLAIM | XFS_INACTIVATING))
         goto out_skip;
 
     if (ip->i_flags & XFS_NEED_INACTIVE) {
         /* Unlinked inodes cannot be re-grabbed. */
         if (VFS_I(ip)->i_nlink == 0) {
             error = -ENOENT;
             goto out_error;
         }
         goto out_inodegc_flush;
     }
 
     /*
      * Check the inode free state is valid. This also detects lookup
      * racing with unlinks.
      */
     error = xfs_iget_check_free_state(ip, flags);
     if (error)
         goto out_error;
 
     /* Skip inodes that have no vfs state. */
     if ((flags & XFS_IGET_INCORE) &&
         (ip->i_flags & XFS_IRECLAIMABLE))
         goto out_skip;
 
     /* The inode fits the selection criteria; process it. */
     if (ip->i_flags & XFS_IRECLAIMABLE) {
         /* Drops i_flags_lock and RCU read lock. */
         error = xfs_iget_recycle(pag, ip);
         if (error)
             return error;
     } else {
         /* If the VFS inode is being torn down, pause and try again. */
         if (!igrab(inode))
             goto out_skip;
 
         /* We've got a live one. */
         spin_unlock(&ip->i_flags_lock);
         rcu_read_unlock();
         trace_xfs_iget_hit(ip);
     }
 
     if (lock_flags != 0)
         xfs_ilock(ip, lock_flags);
 
     if (!(flags & XFS_IGET_INCORE))
         xfs_iflags_clear(ip, XFS_ISTALE);
     XFS_STATS_INC(mp, xs_ig_found);
 
     return 0;
 
 out_skip:
     trace_xfs_iget_skip(ip);
     XFS_STATS_INC(mp, xs_ig_frecycle);
     error = -EAGAIN;
 out_error:
     spin_unlock(&ip->i_flags_lock);
     rcu_read_unlock();
     return error;
 
 out_inodegc_flush:
     spin_unlock(&ip->i_flags_lock);
     rcu_read_unlock();
     /*
      * Do not wait for the workers, because the caller could hold an AGI
      * buffer lock.  We're just going to sleep in a loop anyway.
      */
     if (xfs_is_inodegc_enabled(mp))
         xfs_inodegc_queue_all(mp);
     return -EAGAIN;
 }
 
 static int
 xfs_iget_cache_miss(
     struct xfs_mount    *mp,
     struct xfs_perag    *pag,
     xfs_trans_t     *tp,
     xfs_ino_t       ino,
     struct xfs_inode    **ipp,
     int         flags,
     int         lock_flags)
 {
     struct xfs_inode    *ip;
     int         error;
     xfs_agino_t     agino = XFS_INO_TO_AGINO(mp, ino);
     int         iflags;
 
     ip = xfs_inode_alloc(mp, ino);
     if (!ip)
         return -ENOMEM;
 
     error = xfs_imap(mp, tp, ip->i_ino, &ip->i_imap, flags);
     if (error)
         goto out_destroy;
 
     /*
      * For version 5 superblocks, if we are initialising a new inode and we
      * are not utilising the XFS_FEAT_IKEEP inode cluster mode, we can
      * simply build the new inode core with a random generation number.
      *
      * For version 4 (and older) superblocks, log recovery is dependent on
      * the i_flushiter field being initialised from the current on-disk
      * value and hence we must also read the inode off disk even when
      * initializing new inodes.
      */
     if (xfs_has_v3inodes(mp) &&
         (flags & XFS_IGET_CREATE) && !xfs_has_ikeep(mp)) {
         VFS_I(ip)->i_generation = prandom_u32();
     } else {
         struct xfs_buf      *bp;
 
         error = xfs_imap_to_bp(mp, tp, &ip->i_imap, &bp);
         if (error)
             goto out_destroy;
 
         error = xfs_inode_from_disk(ip,
                 xfs_buf_offset(bp, ip->i_imap.im_boffset));
         if (!error)
             xfs_buf_set_ref(bp, XFS_INO_REF);
         xfs_trans_brelse(tp, bp);
 
         if (error)
             goto out_destroy;
     }
 
     trace_xfs_iget_miss(ip);
 
     /*
      * Check the inode free state is valid. This also detects lookup
      * racing with unlinks.
      */
     error = xfs_iget_check_free_state(ip, flags);
     if (error)
         goto out_destroy;
 
     /*
      * Preload the radix tree so we can insert safely under the
      * write spinlock. Note that we cannot sleep inside the preload
      * region. Since we can be called from transaction context, don't
      * recurse into the file system.
      */
     if (radix_tree_preload(GFP_NOFS)) {
         error = -EAGAIN;
         goto out_destroy;
     }
 
     /*
      * Because the inode hasn't been added to the radix-tree yet it can't
      * be found by another thread, so we can do the non-sleeping lock here.
      */
     if (lock_flags) {
         if (!xfs_ilock_nowait(ip, lock_flags))
             BUG();
     }
 
     /*
      * These values must be set before inserting the inode into the radix
      * tree as the moment it is inserted a concurrent lookup (allowed by the
      * RCU locking mechanism) can find it and that lookup must see that this
      * is an inode currently under construction (i.e. that XFS_INEW is set).
      * The ip->i_flags_lock that protects the XFS_INEW flag forms the
      * memory barrier that ensures this detection works correctly at lookup
      * time.
      */
     iflags = XFS_INEW;
     if (flags & XFS_IGET_DONTCACHE)
         d_mark_dontcache(VFS_I(ip));
     ip->i_udquot = NULL;
     ip->i_gdquot = NULL;
     ip->i_pdquot = NULL;
     xfs_iflags_set(ip, iflags);
 
     /* insert the new inode */
     spin_lock(&pag->pag_ici_lock);
     error = radix_tree_insert(&pag->pag_ici_root, agino, ip);
     if (unlikely(error)) {
         WARN_ON(error != -EEXIST);
         XFS_STATS_INC(mp, xs_ig_dup);
         error = -EAGAIN;
         goto out_preload_end;
     }
     spin_unlock(&pag->pag_ici_lock);
     radix_tree_preload_end();
 
     *ipp = ip;
     return 0;
 
 out_preload_end:
     spin_unlock(&pag->pag_ici_lock);
     radix_tree_preload_end();
     if (lock_flags)
         xfs_iunlock(ip, lock_flags);
 out_destroy:
     __destroy_inode(VFS_I(ip));
     xfs_inode_free(ip);
     return error;
 }
 
 /*
  * Look up an inode by number in the given file system.  The inode is looked up
  * in the cache held in each AG.  If the inode is found in the cache, initialise
  * the vfs inode if necessary.
  *
  * If it is not in core, read it in from the file system's device, add it to the
  * cache and initialise the vfs inode.
  *
  * The inode is locked according to the value of the lock_flags parameter.
  * Inode lookup is only done during metadata operations and not as part of the
  * data IO path. Hence we only allow locking of the XFS_ILOCK during lookup.
  */
 int
 xfs_iget(
     struct xfs_mount    *mp,
     struct xfs_trans    *tp,
     xfs_ino_t       ino,
     uint            flags,
     uint            lock_flags,
     struct xfs_inode    **ipp)
 {
     struct xfs_inode    *ip;
     struct xfs_perag    *pag;
     xfs_agino_t     agino;
     int         error;
 
     ASSERT((lock_flags & (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED)) == 0);
 
     /* reject inode numbers outside existing AGs */
     if (!ino || XFS_INO_TO_AGNO(mp, ino) >= mp->m_sb.sb_agcount)
         return -EINVAL;
 
     XFS_STATS_INC(mp, xs_ig_attempts);
 
     /* get the perag structure and ensure that it's inode capable */
     pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ino));
     agino = XFS_INO_TO_AGINO(mp, ino);
 
 again:
     error = 0;
     rcu_read_lock();
     ip = radix_tree_lookup(&pag->pag_ici_root, agino);
 
     if (ip) {
         error = xfs_iget_cache_hit(pag, ip, ino, flags, lock_flags);
         if (error)
             goto out_error_or_again;
     } else {
         rcu_read_unlock();
         if (flags & XFS_IGET_INCORE) {
             error = -ENODATA;
             goto out_error_or_again;
         }
         XFS_STATS_INC(mp, xs_ig_missed);
 
         error = xfs_iget_cache_miss(mp, pag, tp, ino, &ip,
                             flags, lock_flags);
         if (error)
             goto out_error_or_again;
     }
     xfs_perag_put(pag);
 
     *ipp = ip;
 
     /*
      * If we have a real type for an on-disk inode, we can setup the inode
      * now.  If it's a new inode being created, xfs_init_new_inode will
      * handle it.
      */
     if (xfs_iflags_test(ip, XFS_INEW) && VFS_I(ip)->i_mode != 0)
         xfs_setup_existing_inode(ip);
     return 0;
 
 out_error_or_again:
     if (!(flags & XFS_IGET_INCORE) && error == -EAGAIN) {
         delay(1);
         goto again;
     }
     xfs_perag_put(pag);
     return error;
 }
 
 /*
  * "Is this a cached inode that's also allocated?"
  *
  * Look up an inode by number in the given file system.  If the inode is
  * in cache and isn't in purgatory, return 1 if the inode is allocated
  * and 0 if it is not.  For all other cases (not in cache, being torn
  * down, etc.), return a negative error code.
  *
  * The caller has to prevent inode allocation and freeing activity,
  * presumably by locking the AGI buffer.   This is to ensure that an
  * inode cannot transition from allocated to freed until the caller is
  * ready to allow that.  If the inode is in an intermediate state (new,
  * reclaimable, or being reclaimed), -EAGAIN will be returned; if the
  * inode is not in the cache, -ENOENT will be returned.  The caller must
  * deal with these scenarios appropriately.
  *
  * This is a specialized use case for the online scrubber; if you're
  * reading this, you probably want xfs_iget.
  */
 int
 xfs_icache_inode_is_allocated(
     struct xfs_mount    *mp,
     struct xfs_trans    *tp,
     xfs_ino_t       ino,
     bool            *inuse)
 {
     struct xfs_inode    *ip;
     int         error;
 
     error = xfs_iget(mp, tp, ino, XFS_IGET_INCORE, 0, &ip);
     if (error)
         return error;
 
     *inuse = !!(VFS_I(ip)->i_mode);
     xfs_irele(ip);
     return 0;
 }
 
 /*
  * Grab the inode for reclaim exclusively.
  *
  * We have found this inode via a lookup under RCU, so the inode may have
  * already been freed, or it may be in the process of being recycled by
  * xfs_iget(). In both cases, the inode will have XFS_IRECLAIM set. If the inode
  * has been fully recycled by the time we get the i_flags_lock, XFS_IRECLAIMABLE
  * will not be set. Hence we need to check for both these flag conditions to
  * avoid inodes that are no longer reclaim candidates.
  *
  * Note: checking for other state flags here, under the i_flags_lock or not, is
  * racy and should be avoided. Those races should be resolved only after we have
  * ensured that we are able to reclaim this inode and the world can see that we
  * are going to reclaim it.
  *
  * Return true if we grabbed it, false otherwise.
  */
 static bool
 xfs_reclaim_igrab(
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw)
 {
     ASSERT(rcu_read_lock_held());
 
     spin_lock(&ip->i_flags_lock);
     if (!__xfs_iflags_test(ip, XFS_IRECLAIMABLE) ||
         __xfs_iflags_test(ip, XFS_IRECLAIM)) {
         /* not a reclaim candidate. */
         spin_unlock(&ip->i_flags_lock);
         return false;
     }
 
     /* Don't reclaim a sick inode unless the caller asked for it. */
     if (ip->i_sick &&
         (!icw || !(icw->icw_flags & XFS_ICWALK_FLAG_RECLAIM_SICK))) {
         spin_unlock(&ip->i_flags_lock);
         return false;
     }
 
     __xfs_iflags_set(ip, XFS_IRECLAIM);
     spin_unlock(&ip->i_flags_lock);
     return true;
 }
 
 /*
  * Inode reclaim is non-blocking, so the default action if progress cannot be
  * made is to "requeue" the inode for reclaim by unlocking it and clearing the
  * XFS_IRECLAIM flag.  If we are in a shutdown state, we don't care about
  * blocking anymore and hence we can wait for the inode to be able to reclaim
  * it.
  *
  * We do no IO here - if callers require inodes to be cleaned they must push the
  * AIL first to trigger writeback of dirty inodes.  This enables writeback to be
  * done in the background in a non-blocking manner, and enables memory reclaim
  * to make progress without blocking.
  */
 static void
 xfs_reclaim_inode(
     struct xfs_inode    *ip,
     struct xfs_perag    *pag)
 {
     xfs_ino_t       ino = ip->i_ino; /* for radix_tree_delete */
 
     if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
         goto out;
     if (xfs_iflags_test_and_set(ip, XFS_IFLUSHING))
         goto out_iunlock;
 
     /*
      * Check for log shutdown because aborting the inode can move the log
      * tail and corrupt in memory state. This is fine if the log is shut
      * down, but if the log is still active and only the mount is shut down
      * then the in-memory log tail movement caused by the abort can be
      * incorrectly propagated to disk.
      */
     if (xlog_is_shutdown(ip->i_mount->m_log)) {
         xfs_iunpin_wait(ip);
         xfs_iflush_shutdown_abort(ip);
         goto reclaim;
     }
     if (xfs_ipincount(ip))
         goto out_clear_flush;
     if (!xfs_inode_clean(ip))
         goto out_clear_flush;
 
     xfs_iflags_clear(ip, XFS_IFLUSHING);
 reclaim:
     trace_xfs_inode_reclaiming(ip);
 
     /*
      * Because we use RCU freeing we need to ensure the inode always appears
      * to be reclaimed with an invalid inode number when in the free state.
      * We do this as early as possible under the ILOCK so that
      * xfs_iflush_cluster() and xfs_ifree_cluster() can be guaranteed to
      * detect races with us here. By doing this, we guarantee that once
      * xfs_iflush_cluster() or xfs_ifree_cluster() has locked XFS_ILOCK that
      * it will see either a valid inode that will serialise correctly, or it
      * will see an invalid inode that it can skip.
      */
     spin_lock(&ip->i_flags_lock);
     ip->i_flags = XFS_IRECLAIM;
     ip->i_ino = 0;
     ip->i_sick = 0;
     ip->i_checked = 0;
     spin_unlock(&ip->i_flags_lock);
 
     ASSERT(!ip->i_itemp || ip->i_itemp->ili_item.li_buf == NULL);
     xfs_iunlock(ip, XFS_ILOCK_EXCL);
 
     XFS_STATS_INC(ip->i_mount, xs_ig_reclaims);
     /*
      * Remove the inode from the per-AG radix tree.
      *
      * Because radix_tree_delete won't complain even if the item was never
      * added to the tree assert that it's been there before to catch
      * problems with the inode life time early on.
      */
     spin_lock(&pag->pag_ici_lock);
     if (!radix_tree_delete(&pag->pag_ici_root,
                 XFS_INO_TO_AGINO(ip->i_mount, ino)))
         ASSERT(0);
     xfs_perag_clear_inode_tag(pag, NULLAGINO, XFS_ICI_RECLAIM_TAG);
     spin_unlock(&pag->pag_ici_lock);
 
     /*
      * Here we do an (almost) spurious inode lock in order to coordinate
      * with inode cache radix tree lookups.  This is because the lookup
      * can reference the inodes in the cache without taking references.
      *
      * We make that OK here by ensuring that we wait until the inode is
      * unlocked after the lookup before we go ahead and free it.
      */
     xfs_ilock(ip, XFS_ILOCK_EXCL);
     ASSERT(!ip->i_udquot && !ip->i_gdquot && !ip->i_pdquot);
     xfs_iunlock(ip, XFS_ILOCK_EXCL);
     ASSERT(xfs_inode_clean(ip));
 
     __xfs_inode_free(ip);
     return;
 
 out_clear_flush:
     xfs_iflags_clear(ip, XFS_IFLUSHING);
 out_iunlock:
     xfs_iunlock(ip, XFS_ILOCK_EXCL);
 out:
     xfs_iflags_clear(ip, XFS_IRECLAIM);
 }
 
 /* Reclaim sick inodes if we're unmounting or the fs went down. */
 static inline bool
 xfs_want_reclaim_sick(
     struct xfs_mount    *mp)
 {
     return xfs_is_unmounting(mp) || xfs_has_norecovery(mp) ||
            xfs_is_shutdown(mp);
 }
 
 void
 xfs_reclaim_inodes(
     struct xfs_mount    *mp)
 {
     struct xfs_icwalk   icw = {
         .icw_flags  = 0,
     };
 
     if (xfs_want_reclaim_sick(mp))
         icw.icw_flags |= XFS_ICWALK_FLAG_RECLAIM_SICK;
 
     while (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
         xfs_ail_push_all_sync(mp->m_ail);
         xfs_icwalk(mp, XFS_ICWALK_RECLAIM, &icw);
     }
 }
 
 /*
  * The shrinker infrastructure determines how many inodes we should scan for
  * reclaim. We want as many clean inodes ready to reclaim as possible, so we
  * push the AIL here. We also want to proactively free up memory if we can to
  * minimise the amount of work memory reclaim has to do so we kick the
  * background reclaim if it isn't already scheduled.
  */
 long
 xfs_reclaim_inodes_nr(
     struct xfs_mount    *mp,
     unsigned long       nr_to_scan)
 {
     struct xfs_icwalk   icw = {
         .icw_flags  = XFS_ICWALK_FLAG_SCAN_LIMIT,
         .icw_scan_limit = min_t(unsigned long, LONG_MAX, nr_to_scan),
     };
 
     if (xfs_want_reclaim_sick(mp))
         icw.icw_flags |= XFS_ICWALK_FLAG_RECLAIM_SICK;
 
     /* kick background reclaimer and push the AIL */
     xfs_reclaim_work_queue(mp);
     xfs_ail_push_all(mp->m_ail);
 
     xfs_icwalk(mp, XFS_ICWALK_RECLAIM, &icw);
     return 0;
 }
 
 /*
  * Return the number of reclaimable inodes in the filesystem for
  * the shrinker to determine how much to reclaim.
  */
 long
 xfs_reclaim_inodes_count(
     struct xfs_mount    *mp)
 {
     struct xfs_perag    *pag;
     xfs_agnumber_t      ag = 0;
     long            reclaimable = 0;
 
     while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
         ag = pag->pag_agno + 1;
         reclaimable += pag->pag_ici_reclaimable;
         xfs_perag_put(pag);
     }
     return reclaimable;
 }
 
 STATIC bool
 xfs_icwalk_match_id(
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw)
 {
     if ((icw->icw_flags & XFS_ICWALK_FLAG_UID) &&
         !uid_eq(VFS_I(ip)->i_uid, icw->icw_uid))
         return false;
 
     if ((icw->icw_flags & XFS_ICWALK_FLAG_GID) &&
         !gid_eq(VFS_I(ip)->i_gid, icw->icw_gid))
         return false;
 
     if ((icw->icw_flags & XFS_ICWALK_FLAG_PRID) &&
         ip->i_projid != icw->icw_prid)
         return false;
 
     return true;
 }
 
 /*
  * A union-based inode filtering algorithm. Process the inode if any of the
  * criteria match. This is for global/internal scans only.
  */
 STATIC bool
 xfs_icwalk_match_id_union(
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw)
 {
     if ((icw->icw_flags & XFS_ICWALK_FLAG_UID) &&
         uid_eq(VFS_I(ip)->i_uid, icw->icw_uid))
         return true;
 
     if ((icw->icw_flags & XFS_ICWALK_FLAG_GID) &&
         gid_eq(VFS_I(ip)->i_gid, icw->icw_gid))
         return true;
 
     if ((icw->icw_flags & XFS_ICWALK_FLAG_PRID) &&
         ip->i_projid == icw->icw_prid)
         return true;
 
     return false;
 }
 
 /*
  * Is this inode @ip eligible for eof/cow block reclamation, given some
  * filtering parameters @icw?  The inode is eligible if @icw is null or
  * if the predicate functions match.
  */
 static bool
 xfs_icwalk_match(
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw)
 {
     bool            match;
 
     if (!icw)
         return true;
 
     if (icw->icw_flags & XFS_ICWALK_FLAG_UNION)
         match = xfs_icwalk_match_id_union(ip, icw);
     else
         match = xfs_icwalk_match_id(ip, icw);
     if (!match)
         return false;
 
     /* skip the inode if the file size is too small */
     if ((icw->icw_flags & XFS_ICWALK_FLAG_MINFILESIZE) &&
         XFS_ISIZE(ip) < icw->icw_min_file_size)
         return false;
 
     return true;
 }
 
 /*
  * This is a fast pass over the inode cache to try to get reclaim moving on as
  * many inodes as possible in a short period of time. It kicks itself every few
  * seconds, as well as being kicked by the inode cache shrinker when memory
  * goes low.
  */
 void
 xfs_reclaim_worker(
     struct work_struct *work)
 {
     struct xfs_mount *mp = container_of(to_delayed_work(work),
                     struct xfs_mount, m_reclaim_work);
 
     xfs_icwalk(mp, XFS_ICWALK_RECLAIM, NULL);
     xfs_reclaim_work_queue(mp);
 }
 
 STATIC int
 xfs_inode_free_eofblocks(
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw,
     unsigned int        *lockflags)
 {
     bool            wait;
 
     wait = icw && (icw->icw_flags & XFS_ICWALK_FLAG_SYNC);
 
     if (!xfs_iflags_test(ip, XFS_IEOFBLOCKS))
         return 0;
 
     /*
      * If the mapping is dirty the operation can block and wait for some
      * time. Unless we are waiting, skip it.
      */
     if (!wait && mapping_tagged(VFS_I(ip)->i_mapping, PAGECACHE_TAG_DIRTY))
         return 0;
 
     if (!xfs_icwalk_match(ip, icw))
         return 0;
 
     /*
      * If the caller is waiting, return -EAGAIN to keep the background
      * scanner moving and revisit the inode in a subsequent pass.
      */
     if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
         if (wait)
             return -EAGAIN;
         return 0;
     }
     *lockflags |= XFS_IOLOCK_EXCL;
 
     if (xfs_can_free_eofblocks(ip, false))
         return xfs_free_eofblocks(ip);
 
     /* inode could be preallocated or append-only */
     trace_xfs_inode_free_eofblocks_invalid(ip);
     xfs_inode_clear_eofblocks_tag(ip);
     return 0;
 }
 
 static void
 xfs_blockgc_set_iflag(
     struct xfs_inode    *ip,
     unsigned long       iflag)
 {
     struct xfs_mount    *mp = ip->i_mount;
     struct xfs_perag    *pag;
 
     ASSERT((iflag & ~(XFS_IEOFBLOCKS | XFS_ICOWBLOCKS)) == 0);
 
     /*
      * Don't bother locking the AG and looking up in the radix trees
      * if we already know that we have the tag set.
      */
     if (ip->i_flags & iflag)
         return;
     spin_lock(&ip->i_flags_lock);
     ip->i_flags |= iflag;
     spin_unlock(&ip->i_flags_lock);
 
     pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
     spin_lock(&pag->pag_ici_lock);
 
     xfs_perag_set_inode_tag(pag, XFS_INO_TO_AGINO(mp, ip->i_ino),
             XFS_ICI_BLOCKGC_TAG);
 
     spin_unlock(&pag->pag_ici_lock);
     xfs_perag_put(pag);
 }
 
 void
 xfs_inode_set_eofblocks_tag(
     xfs_inode_t *ip)
 {
     trace_xfs_inode_set_eofblocks_tag(ip);
     return xfs_blockgc_set_iflag(ip, XFS_IEOFBLOCKS);
 }
 
 static void
 xfs_blockgc_clear_iflag(
     struct xfs_inode    *ip,
     unsigned long       iflag)
 {
     struct xfs_mount    *mp = ip->i_mount;
     struct xfs_perag    *pag;
     bool            clear_tag;
 
     ASSERT((iflag & ~(XFS_IEOFBLOCKS | XFS_ICOWBLOCKS)) == 0);
 
     spin_lock(&ip->i_flags_lock);
     ip->i_flags &= ~iflag;
     clear_tag = (ip->i_flags & (XFS_IEOFBLOCKS | XFS_ICOWBLOCKS)) == 0;
     spin_unlock(&ip->i_flags_lock);
 
     if (!clear_tag)
         return;
 
     pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
     spin_lock(&pag->pag_ici_lock);
 
     xfs_perag_clear_inode_tag(pag, XFS_INO_TO_AGINO(mp, ip->i_ino),
             XFS_ICI_BLOCKGC_TAG);
 
     spin_unlock(&pag->pag_ici_lock);
     xfs_perag_put(pag);
 }
 
 void
 xfs_inode_clear_eofblocks_tag(
     xfs_inode_t *ip)
 {
     trace_xfs_inode_clear_eofblocks_tag(ip);
     return xfs_blockgc_clear_iflag(ip, XFS_IEOFBLOCKS);
 }
 
 /*
  * Set ourselves up to free CoW blocks from this file.  If it's already clean
  * then we can bail out quickly, but otherwise we must back off if the file
  * is undergoing some kind of write.
  */
 static bool
 xfs_prep_free_cowblocks(
     struct xfs_inode    *ip)
 {
     /*
      * Just clear the tag if we have an empty cow fork or none at all. It's
      * possible the inode was fully unshared since it was originally tagged.
      */
     if (!xfs_inode_has_cow_data(ip)) {
         trace_xfs_inode_free_cowblocks_invalid(ip);
         xfs_inode_clear_cowblocks_tag(ip);
         return false;
     }
 
     /*
      * If the mapping is dirty or under writeback we cannot touch the
      * CoW fork.  Leave it alone if we're in the midst of a directio.
      */
     if ((VFS_I(ip)->i_state & I_DIRTY_PAGES) ||
         mapping_tagged(VFS_I(ip)->i_mapping, PAGECACHE_TAG_DIRTY) ||
         mapping_tagged(VFS_I(ip)->i_mapping, PAGECACHE_TAG_WRITEBACK) ||
         atomic_read(&VFS_I(ip)->i_dio_count))
         return false;
 
     return true;
 }
 
 /*
  * Automatic CoW Reservation Freeing
  *
  * These functions automatically garbage collect leftover CoW reservations
  * that were made on behalf of a cowextsize hint when we start to run out
  * of quota or when the reservations sit around for too long.  If the file
  * has dirty pages or is undergoing writeback, its CoW reservations will
  * be retained.
  *
  * The actual garbage collection piggybacks off the same code that runs
  * the speculative EOF preallocation garbage collector.
  */
 STATIC int
 xfs_inode_free_cowblocks(
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw,
     unsigned int        *lockflags)
 {
     bool            wait;
     int         ret = 0;
 
     wait = icw && (icw->icw_flags & XFS_ICWALK_FLAG_SYNC);
 
     if (!xfs_iflags_test(ip, XFS_ICOWBLOCKS))
         return 0;
 
     if (!xfs_prep_free_cowblocks(ip))
         return 0;
 
     if (!xfs_icwalk_match(ip, icw))
         return 0;
 
     /*
      * If the caller is waiting, return -EAGAIN to keep the background
      * scanner moving and revisit the inode in a subsequent pass.
      */
     if (!(*lockflags & XFS_IOLOCK_EXCL) &&
         !xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
         if (wait)
             return -EAGAIN;
         return 0;
     }
     *lockflags |= XFS_IOLOCK_EXCL;
 
     if (!xfs_ilock_nowait(ip, XFS_MMAPLOCK_EXCL)) {
         if (wait)
             return -EAGAIN;
         return 0;
     }
     *lockflags |= XFS_MMAPLOCK_EXCL;
 
     /*
      * Check again, nobody else should be able to dirty blocks or change
      * the reflink iflag now that we have the first two locks held.
      */
     if (xfs_prep_free_cowblocks(ip))
         ret = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, false);
     return ret;
 }
 
 void
 xfs_inode_set_cowblocks_tag(
     xfs_inode_t *ip)
 {
     trace_xfs_inode_set_cowblocks_tag(ip);
     return xfs_blockgc_set_iflag(ip, XFS_ICOWBLOCKS);
 }
 
 void
 xfs_inode_clear_cowblocks_tag(
     xfs_inode_t *ip)
 {
     trace_xfs_inode_clear_cowblocks_tag(ip);
     return xfs_blockgc_clear_iflag(ip, XFS_ICOWBLOCKS);
 }
 
 /* Disable post-EOF and CoW block auto-reclamation. */
 void
 xfs_blockgc_stop(
     struct xfs_mount    *mp)
 {
     struct xfs_perag    *pag;
     xfs_agnumber_t      agno;
 
     if (!xfs_clear_blockgc_enabled(mp))
         return;
 
     for_each_perag(mp, agno, pag)
         cancel_delayed_work_sync(&pag->pag_blockgc_work);
     trace_xfs_blockgc_stop(mp, __return_address);
 }
 
 /* Enable post-EOF and CoW block auto-reclamation. */
 void
 xfs_blockgc_start(
     struct xfs_mount    *mp)
 {
     struct xfs_perag    *pag;
     xfs_agnumber_t      agno;
 
     if (xfs_set_blockgc_enabled(mp))
         return;
 
     trace_xfs_blockgc_start(mp, __return_address);
     for_each_perag_tag(mp, agno, pag, XFS_ICI_BLOCKGC_TAG)
         xfs_blockgc_queue(pag);
 }
 
 /* Don't try to run block gc on an inode that's in any of these states. */
 #define XFS_BLOCKGC_NOGRAB_IFLAGS   (XFS_INEW | \
                      XFS_NEED_INACTIVE | \
                      XFS_INACTIVATING | \
                      XFS_IRECLAIMABLE | \
                      XFS_IRECLAIM)
 /*
  * Decide if the given @ip is eligible for garbage collection of speculative
  * preallocations, and grab it if so.  Returns true if it's ready to go or
  * false if we should just ignore it.
  */
 static bool
 xfs_blockgc_igrab(
     struct xfs_inode    *ip)
 {
     struct inode        *inode = VFS_I(ip);
 
     ASSERT(rcu_read_lock_held());
 
     /* Check for stale RCU freed inode */
     spin_lock(&ip->i_flags_lock);
     if (!ip->i_ino)
         goto out_unlock_noent;
 
     if (ip->i_flags & XFS_BLOCKGC_NOGRAB_IFLAGS)
         goto out_unlock_noent;
     spin_unlock(&ip->i_flags_lock);
 
     /* nothing to sync during shutdown */
     if (xfs_is_shutdown(ip->i_mount))
         return false;
 
     /* If we can't grab the inode, it must on it's way to reclaim. */
     if (!igrab(inode))
         return false;
 
     /* inode is valid */
     return true;
 
 out_unlock_noent:
     spin_unlock(&ip->i_flags_lock);
     return false;
 }
 
 /* Scan one incore inode for block preallocations that we can remove. */
 static int
 xfs_blockgc_scan_inode(
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw)
 {
     unsigned int        lockflags = 0;
     int         error;
 
     error = xfs_inode_free_eofblocks(ip, icw, &lockflags);
     if (error)
         goto unlock;
 
     error = xfs_inode_free_cowblocks(ip, icw, &lockflags);
 unlock:
     if (lockflags)
         xfs_iunlock(ip, lockflags);
     xfs_irele(ip);
     return error;
 }
 
 /* Background worker that trims preallocated space. */
 void
 xfs_blockgc_worker(
     struct work_struct  *work)
 {
     struct xfs_perag    *pag = container_of(to_delayed_work(work),
                     struct xfs_perag, pag_blockgc_work);
     struct xfs_mount    *mp = pag->pag_mount;
     int         error;
 
     trace_xfs_blockgc_worker(mp, __return_address);
 
     error = xfs_icwalk_ag(pag, XFS_ICWALK_BLOCKGC, NULL);
     if (error)
         xfs_info(mp, "AG %u preallocation gc worker failed, err=%d",
                 pag->pag_agno, error);
     xfs_blockgc_queue(pag);
 }
 
 /*
  * Try to free space in the filesystem by purging inactive inodes, eofblocks
  * and cowblocks.
  */
 int
 xfs_blockgc_free_space(
     struct xfs_mount    *mp,
     struct xfs_icwalk   *icw)
 {
     int         error;
 
     trace_xfs_blockgc_free_space(mp, icw, _RET_IP_);
 
     error = xfs_icwalk(mp, XFS_ICWALK_BLOCKGC, icw);
     if (error)
         return error;
 
     xfs_inodegc_flush(mp);
     return 0;
 }
 
 /*
  * Reclaim all the free space that we can by scheduling the background blockgc
  * and inodegc workers immediately and waiting for them all to clear.
  */
 void
 xfs_blockgc_flush_all(
     struct xfs_mount    *mp)
 {
     struct xfs_perag    *pag;
     xfs_agnumber_t      agno;
 
     trace_xfs_blockgc_flush_all(mp, __return_address);
 
     /*
      * For each blockgc worker, move its queue time up to now.  If it
      * wasn't queued, it will not be requeued.  Then flush whatever's
      * left.
      */
     for_each_perag_tag(mp, agno, pag, XFS_ICI_BLOCKGC_TAG)
         mod_delayed_work(pag->pag_mount->m_blockgc_wq,
                 &pag->pag_blockgc_work, 0);
 
     for_each_perag_tag(mp, agno, pag, XFS_ICI_BLOCKGC_TAG)
         flush_delayed_work(&pag->pag_blockgc_work);
 
     xfs_inodegc_flush(mp);
 }
 
 /*
  * Run cow/eofblocks scans on the supplied dquots.  We don't know exactly which
  * quota caused an allocation failure, so we make a best effort by including
  * each quota under low free space conditions (less than 1% free space) in the
  * scan.
  *
  * Callers must not hold any inode's ILOCK.  If requesting a synchronous scan
  * (XFS_ICWALK_FLAG_SYNC), the caller also must not hold any inode's IOLOCK or
  * MMAPLOCK.
  */
 int
 xfs_blockgc_free_dquots(
     struct xfs_mount    *mp,
     struct xfs_dquot    *udqp,
     struct xfs_dquot    *gdqp,
     struct xfs_dquot    *pdqp,
     unsigned int        iwalk_flags)
 {
     struct xfs_icwalk   icw = {0};
     bool            do_work = false;
 
     if (!udqp && !gdqp && !pdqp)
         return 0;
 
     /*
      * Run a scan to free blocks using the union filter to cover all
      * applicable quotas in a single scan.
      */
     icw.icw_flags = XFS_ICWALK_FLAG_UNION | iwalk_flags;
 
     if (XFS_IS_UQUOTA_ENFORCED(mp) && udqp && xfs_dquot_lowsp(udqp)) {
         icw.icw_uid = make_kuid(mp->m_super->s_user_ns, udqp->q_id);
         icw.icw_flags |= XFS_ICWALK_FLAG_UID;
         do_work = true;
     }
 
     if (XFS_IS_UQUOTA_ENFORCED(mp) && gdqp && xfs_dquot_lowsp(gdqp)) {
         icw.icw_gid = make_kgid(mp->m_super->s_user_ns, gdqp->q_id);
         icw.icw_flags |= XFS_ICWALK_FLAG_GID;
         do_work = true;
     }
 
     if (XFS_IS_PQUOTA_ENFORCED(mp) && pdqp && xfs_dquot_lowsp(pdqp)) {
         icw.icw_prid = pdqp->q_id;
         icw.icw_flags |= XFS_ICWALK_FLAG_PRID;
         do_work = true;
     }
 
     if (!do_work)
         return 0;
 
     return xfs_blockgc_free_space(mp, &icw);
 }
 
 /* Run cow/eofblocks scans on the quotas attached to the inode. */
 int
 xfs_blockgc_free_quota(
     struct xfs_inode    *ip,
     unsigned int        iwalk_flags)
 {
     return xfs_blockgc_free_dquots(ip->i_mount,
             xfs_inode_dquot(ip, XFS_DQTYPE_USER),
             xfs_inode_dquot(ip, XFS_DQTYPE_GROUP),
             xfs_inode_dquot(ip, XFS_DQTYPE_PROJ), iwalk_flags);
 }
 
 /* XFS Inode Cache Walking Code */
 
 /*
  * The inode lookup is done in batches to keep the amount of lock traffic and
  * radix tree lookups to a minimum. The batch size is a trade off between
  * lookup reduction and stack usage. This is in the reclaim path, so we can't
  * be too greedy.
  */
 #define XFS_LOOKUP_BATCH    32
 
 
 /*
  * Decide if we want to grab this inode in anticipation of doing work towards
  * the goal.
  */
 static inline bool
 xfs_icwalk_igrab(
     enum xfs_icwalk_goal    goal,
     struct xfs_inode    *ip,
     struct xfs_icwalk   *icw)
 {
     switch (goal) {
     case XFS_ICWALK_BLOCKGC:
         return xfs_blockgc_igrab(ip);
     case XFS_ICWALK_RECLAIM:
         return xfs_reclaim_igrab(ip, icw);
     default:
         return false;
     }
 }
 
 /*
  * Process an inode.  Each processing function must handle any state changes
  * made by the icwalk igrab function.  Return -EAGAIN to skip an inode.
  */
 static inline int
 xfs_icwalk_process_inode(
     enum xfs_icwalk_goal    goal,
     struct xfs_inode    *ip,
     struct xfs_perag    *pag,
     struct xfs_icwalk   *icw)
 {
     int         error = 0;
 
     switch (goal) {
     case XFS_ICWALK_BLOCKGC:
         error = xfs_blockgc_scan_inode(ip, icw);
         break;
     case XFS_ICWALK_RECLAIM:
         xfs_reclaim_inode(ip, pag);
         break;
     }
     return error;
 }
 
 /*
  * For a given per-AG structure @pag and a goal, grab qualifying inodes and
  * process them in some manner.
  */
 static int
 xfs_icwalk_ag(
     struct xfs_perag    *pag,
     enum xfs_icwalk_goal    goal,
     struct xfs_icwalk   *icw)
 {
     struct xfs_mount    *mp = pag->pag_mount;
     uint32_t        first_index;
     int         last_error = 0;
     int         skipped;
     bool            done;
     int         nr_found;
 
 restart:
     done = false;
     skipped = 0;
     if (goal == XFS_ICWALK_RECLAIM)
         first_index = READ_ONCE(pag->pag_ici_reclaim_cursor);
     else
         first_index = 0;
     nr_found = 0;
     do {
         struct xfs_inode *batch[XFS_LOOKUP_BATCH];
         int     error = 0;
         int     i;
 
         rcu_read_lock();
 
         nr_found = radix_tree_gang_lookup_tag(&pag->pag_ici_root,
                 (void **) batch, first_index,
                 XFS_LOOKUP_BATCH, goal);
         if (!nr_found) {
             done = true;
             rcu_read_unlock();
             break;
         }
 
         /*
          * Grab the inodes before we drop the lock. if we found
          * nothing, nr == 0 and the loop will be skipped.
          */
         for (i = 0; i < nr_found; i++) {
             struct xfs_inode *ip = batch[i];
 
             if (done || !xfs_icwalk_igrab(goal, ip, icw))
                 batch[i] = NULL;
 
             /*
              * Update the index for the next lookup. Catch
              * overflows into the next AG range which can occur if
              * we have inodes in the last block of the AG and we
              * are currently pointing to the last inode.
              *
              * Because we may see inodes that are from the wrong AG
              * due to RCU freeing and reallocation, only update the
              * index if it lies in this AG. It was a race that lead
              * us to see this inode, so another lookup from the
              * same index will not find it again.
              */
             if (XFS_INO_TO_AGNO(mp, ip->i_ino) != pag->pag_agno)
                 continue;
             first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
             if (first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
                 done = true;
         }
 
         /* unlock now we've grabbed the inodes. */
         rcu_read_unlock();
 
         for (i = 0; i < nr_found; i++) {
             if (!batch[i])
                 continue;
             error = xfs_icwalk_process_inode(goal, batch[i], pag,
                     icw);
             if (error == -EAGAIN) {
                 skipped++;
                 continue;
             }
             if (error && last_error != -EFSCORRUPTED)
                 last_error = error;
         }
 
         /* bail out if the filesystem is corrupted.  */
         if (error == -EFSCORRUPTED)
             break;
 
         cond_resched();
 
         if (icw && (icw->icw_flags & XFS_ICWALK_FLAG_SCAN_LIMIT)) {
             icw->icw_scan_limit -= XFS_LOOKUP_BATCH;
             if (icw->icw_scan_limit <= 0)
                 break;
         }
     } while (nr_found && !done);
 
     if (goal == XFS_ICWALK_RECLAIM) {
         if (done)
             first_index = 0;
         WRITE_ONCE(pag->pag_ici_reclaim_cursor, first_index);
     }
 
     if (skipped) {
         delay(1);
         goto restart;
     }
     return last_error;
 }
 
 /* Walk all incore inodes to achieve a given goal. */
 static int
 xfs_icwalk(
     struct xfs_mount    *mp,
     enum xfs_icwalk_goal    goal,
     struct xfs_icwalk   *icw)
 {
     struct xfs_perag    *pag;
     int         error = 0;
     int         last_error = 0;
     xfs_agnumber_t      agno;
 
     for_each_perag_tag(mp, agno, pag, goal) {
         error = xfs_icwalk_ag(pag, goal, icw);
         if (error) {
             last_error = error;
             if (error == -EFSCORRUPTED) {
                 xfs_perag_put(pag);
                 break;
             }
         }
     }
     return last_error;
     BUILD_BUG_ON(XFS_ICWALK_PRIVATE_FLAGS & XFS_ICWALK_FLAGS_VALID);
 }
 
 #ifdef DEBUG
 static void
 xfs_check_delalloc(
     struct xfs_inode    *ip,
     int         whichfork)
 {
     struct xfs_ifork    *ifp = xfs_ifork_ptr(ip, whichfork);
     struct xfs_bmbt_irec    got;
     struct xfs_iext_cursor  icur;
 
     if (!ifp || !xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got))
         return;
     do {
         if (isnullstartblock(got.br_startblock)) {
             xfs_warn(ip->i_mount,
     "ino %llx %s fork has delalloc extent at [0x%llx:0x%llx]",
                 ip->i_ino,
                 whichfork == XFS_DATA_FORK ? "data" : "cow",
                 got.br_startoff, got.br_blockcount);
         }
     } while (xfs_iext_next_extent(ifp, &icur, &got));
 }
 #else
 #define xfs_check_delalloc(ip, whichfork)   do { } while (0)
 #endif
 
 /* Schedule the inode for reclaim. */
 static void
 xfs_inodegc_set_reclaimable(
     struct xfs_inode    *ip)
 {
     struct xfs_mount    *mp = ip->i_mount;
     struct xfs_perag    *pag;
 
     if (!xfs_is_shutdown(mp) && ip->i_delayed_blks) {
         xfs_check_delalloc(ip, XFS_DATA_FORK);
         xfs_check_delalloc(ip, XFS_COW_FORK);
         ASSERT(0);
     }
 
     pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
     spin_lock(&pag->pag_ici_lock);
     spin_lock(&ip->i_flags_lock);
 
     trace_xfs_inode_set_reclaimable(ip);
     ip->i_flags &= ~(XFS_NEED_INACTIVE | XFS_INACTIVATING);
     ip->i_flags |= XFS_IRECLAIMABLE;
     xfs_perag_set_inode_tag(pag, XFS_INO_TO_AGINO(mp, ip->i_ino),
             XFS_ICI_RECLAIM_TAG);
 
     spin_unlock(&ip->i_flags_lock);
     spin_unlock(&pag->pag_ici_lock);
     xfs_perag_put(pag);
 }
 
 /*
  * Free all speculative preallocations and possibly even the inode itself.
  * This is the last chance to make changes to an otherwise unreferenced file
  * before incore reclamation happens.
  */
 static void
 xfs_inodegc_inactivate(
     struct xfs_inode    *ip)
 {
     trace_xfs_inode_inactivating(ip);
     xfs_inactive(ip);
     xfs_inodegc_set_reclaimable(ip);
 }
 
 void
 xfs_inodegc_worker(
     struct work_struct  *work)
 {
     struct xfs_inodegc  *gc = container_of(to_delayed_work(work),
                         struct xfs_inodegc, work);
     struct llist_node   *node = llist_del_all(&gc->list);
     struct xfs_inode    *ip, *n;
 
     WRITE_ONCE(gc->items, 0);
 
     if (!node)
         return;
 
     ip = llist_entry(node, struct xfs_inode, i_gclist);
     trace_xfs_inodegc_worker(ip->i_mount, READ_ONCE(gc->shrinker_hits));
 
     WRITE_ONCE(gc->shrinker_hits, 0);
     llist_for_each_entry_safe(ip, n, node, i_gclist) {
         xfs_iflags_set(ip, XFS_INACTIVATING);
         xfs_inodegc_inactivate(ip);
     }
 }
 
 /*
  * Expedite all pending inodegc work to run immediately. This does not wait for
  * completion of the work.
  */
 void
 xfs_inodegc_push(
     struct xfs_mount    *mp)
 {
     if (!xfs_is_inodegc_enabled(mp))
         return;
     trace_xfs_inodegc_push(mp, __return_address);
     xfs_inodegc_queue_all(mp);
 }
 
 /*
  * Force all currently queued inode inactivation work to run immediately and
  * wait for the work to finish.
  */
 void
 xfs_inodegc_flush(
     struct xfs_mount    *mp)
 {
     xfs_inodegc_push(mp);
     trace_xfs_inodegc_flush(mp, __return_address);
     flush_workqueue(mp->m_inodegc_wq);
 }
 
 /*
  * Flush all the pending work and then disable the inode inactivation background
  * workers and wait for them to stop.
  */
 void
 xfs_inodegc_stop(
     struct xfs_mount    *mp)
 {
     if (!xfs_clear_inodegc_enabled(mp))
         return;
 
     xfs_inodegc_queue_all(mp);
     drain_workqueue(mp->m_inodegc_wq);
 
     trace_xfs_inodegc_stop(mp, __return_address);
 }
 
 /*
  * Enable the inode inactivation background workers and schedule deferred inode
  * inactivation work if there is any.
  */
 void
 xfs_inodegc_start(
     struct xfs_mount    *mp)
 {
     if (xfs_set_inodegc_enabled(mp))
         return;
 
     trace_xfs_inodegc_start(mp, __return_address);
     xfs_inodegc_queue_all(mp);
 }
 
 #ifdef CONFIG_XFS_RT
 static inline bool
 xfs_inodegc_want_queue_rt_file(
     struct xfs_inode    *ip)
 {
     struct xfs_mount    *mp = ip->i_mount;
 
     if (!XFS_IS_REALTIME_INODE(ip))
         return false;
 
     if (__percpu_counter_compare(&mp->m_frextents,
                 mp->m_low_rtexts[XFS_LOWSP_5_PCNT],
                 XFS_FDBLOCKS_BATCH) < 0)
         return true;
 
     return false;
 }
 #else
 # define xfs_inodegc_want_queue_rt_file(ip) (false)
 #endif /* CONFIG_XFS_RT */
 
 /*
  * Schedule the inactivation worker when:
  *
  *  - We've accumulated more than one inode cluster buffer's worth of inodes.
  *  - There is less than 5% free space left.
  *  - Any of the quotas for this inode are near an enforcement limit.
  */
 static inline bool
 xfs_inodegc_want_queue_work(
     struct xfs_inode    *ip,
     unsigned int        items)
 {
     struct xfs_mount    *mp = ip->i_mount;
 
     if (items > mp->m_ino_geo.inodes_per_cluster)
         return true;
 
     if (__percpu_counter_compare(&mp->m_fdblocks,
                 mp->m_low_space[XFS_LOWSP_5_PCNT],
                 XFS_FDBLOCKS_BATCH) < 0)
         return true;
 
     if (xfs_inodegc_want_queue_rt_file(ip))
         return true;
 
     if (xfs_inode_near_dquot_enforcement(ip, XFS_DQTYPE_USER))
         return true;
 
     if (xfs_inode_near_dquot_enforcement(ip, XFS_DQTYPE_GROUP))
         return true;
 
     if (xfs_inode_near_dquot_enforcement(ip, XFS_DQTYPE_PROJ))
         return true;
 
     return false;
 }
 
 /*
  * Upper bound on the number of inodes in each AG that can be queued for
  * inactivation at any given time, to avoid monopolizing the workqueue.
  */
 #define XFS_INODEGC_MAX_BACKLOG     (4 * XFS_INODES_PER_CHUNK)
 
 /*
  * Make the frontend wait for inactivations when:
  *
  *  - Memory shrinkers queued the inactivation worker and it hasn't finished.
  *  - The queue depth exceeds the maximum allowable percpu backlog.
  *
  * Note: If the current thread is running a transaction, we don't ever want to
  * wait for other transactions because that could introduce a deadlock.
  */
 static inline bool
 xfs_inodegc_want_flush_work(
     struct xfs_inode    *ip,
     unsigned int        items,
     unsigned int        shrinker_hits)
 {
     if (current->journal_info)
         return false;
 
     if (shrinker_hits > 0)
         return true;
 
     if (items > XFS_INODEGC_MAX_BACKLOG)
         return true;
 
     return false;
 }
 
 /*
  * Queue a background inactivation worker if there are inodes that need to be
  * inactivated and higher level xfs code hasn't disabled the background
  * workers.
  */
 static void
 xfs_inodegc_queue(
     struct xfs_inode    *ip)
 {
     struct xfs_mount    *mp = ip->i_mount;
     struct xfs_inodegc  *gc;
     int         items;
     unsigned int        shrinker_hits;
     unsigned long       queue_delay = 1;
 
     trace_xfs_inode_set_need_inactive(ip);
     spin_lock(&ip->i_flags_lock);
     ip->i_flags |= XFS_NEED_INACTIVE;
     spin_unlock(&ip->i_flags_lock);
 
     gc = get_cpu_ptr(mp->m_inodegc);
     llist_add(&ip->i_gclist, &gc->list);
     items = READ_ONCE(gc->items);
     WRITE_ONCE(gc->items, items + 1);
     shrinker_hits = READ_ONCE(gc->shrinker_hits);
 
     /*
      * We queue the work while holding the current CPU so that the work
      * is scheduled to run on this CPU.
      */
     if (!xfs_is_inodegc_enabled(mp)) {
         put_cpu_ptr(gc);
         return;
     }
 
     if (xfs_inodegc_want_queue_work(ip, items))
         queue_delay = 0;
 
     trace_xfs_inodegc_queue(mp, __return_address);
     mod_delayed_work(mp->m_inodegc_wq, &gc->work, queue_delay);
     put_cpu_ptr(gc);
 
     if (xfs_inodegc_want_flush_work(ip, items, shrinker_hits)) {
         trace_xfs_inodegc_throttle(mp, __return_address);
         flush_delayed_work(&gc->work);
     }
 }
 
 /*
  * Fold the dead CPU inodegc queue into the current CPUs queue.
  */
 void
 xfs_inodegc_cpu_dead(
     struct xfs_mount    *mp,
     unsigned int        dead_cpu)
 {
     struct xfs_inodegc  *dead_gc, *gc;
     struct llist_node   *first, *last;
     unsigned int        count = 0;
 
     dead_gc = per_cpu_ptr(mp->m_inodegc, dead_cpu);
     cancel_delayed_work_sync(&dead_gc->work);
 
     if (llist_empty(&dead_gc->list))
         return;
 
     first = dead_gc->list.first;
     last = first;
     while (last->next) {
         last = last->next;
         count++;
     }
     dead_gc->list.first = NULL;
     dead_gc->items = 0;
 
     /* Add pending work to current CPU */
     gc = get_cpu_ptr(mp->m_inodegc);
     llist_add_batch(first, last, &gc->list);
     count += READ_ONCE(gc->items);
     WRITE_ONCE(gc->items, count);
 
     if (xfs_is_inodegc_enabled(mp)) {
         trace_xfs_inodegc_queue(mp, __return_address);
         mod_delayed_work(mp->m_inodegc_wq, &gc->work, 0);
     }
     put_cpu_ptr(gc);
 }
 
 /*
  * We set the inode flag atomically with the radix tree tag.  Once we get tag
  * lookups on the radix tree, this inode flag can go away.
  *
  * We always use background reclaim here because even if the inode is clean, it
  * still may be under IO and hence we have wait for IO completion to occur
  * before we can reclaim the inode. The background reclaim path handles this
  * more efficiently than we can here, so simply let background reclaim tear down
  * all inodes.
  */
 void
 xfs_inode_mark_reclaimable(
     struct xfs_inode    *ip)
 {
     struct xfs_mount    *mp = ip->i_mount;
     bool            need_inactive;
 
     XFS_STATS_INC(mp, vn_reclaim);
 
     /*
      * We should never get here with any of the reclaim flags already set.
      */
     ASSERT_ALWAYS(!xfs_iflags_test(ip, XFS_ALL_IRECLAIM_FLAGS));
 
     need_inactive = xfs_inode_needs_inactive(ip);
     if (need_inactive) {
         xfs_inodegc_queue(ip);
         return;
     }
 
     /* Going straight to reclaim, so drop the dquots. */
     xfs_qm_dqdetach(ip);
     xfs_inodegc_set_reclaimable(ip);
 }
 
 /*
  * Register a phony shrinker so that we can run background inodegc sooner when
  * there's memory pressure.  Inactivation does not itself free any memory but
  * it does make inodes reclaimable, which eventually frees memory.
  *
  * The count function, seek value, and batch value are crafted to trigger the
  * scan function during the second round of scanning.  Hopefully this means
  * that we reclaimed enough memory that initiating metadata transactions won't
  * make things worse.
  */
 #define XFS_INODEGC_SHRINKER_COUNT  (1UL << DEF_PRIORITY)
 #define XFS_INODEGC_SHRINKER_BATCH  ((XFS_INODEGC_SHRINKER_COUNT / 2) + 1)
 
 static unsigned long
 xfs_inodegc_shrinker_count(
     struct shrinker     *shrink,
     struct shrink_control   *sc)
 {
     struct xfs_mount    *mp = container_of(shrink, struct xfs_mount,
                            m_inodegc_shrinker);
     struct xfs_inodegc  *gc;
     int         cpu;
 
     if (!xfs_is_inodegc_enabled(mp))
         return 0;
 
     for_each_online_cpu(cpu) {
         gc = per_cpu_ptr(mp->m_inodegc, cpu);
         if (!llist_empty(&gc->list))
             return XFS_INODEGC_SHRINKER_COUNT;
     }
 
     return 0;
 }
 
 static unsigned long
 xfs_inodegc_shrinker_scan(
     struct shrinker     *shrink,
     struct shrink_control   *sc)
 {
     struct xfs_mount    *mp = container_of(shrink, struct xfs_mount,
                            m_inodegc_shrinker);
     struct xfs_inodegc  *gc;
     int         cpu;
     bool            no_items = true;
 
     if (!xfs_is_inodegc_enabled(mp))
         return SHRINK_STOP;
 
     trace_xfs_inodegc_shrinker_scan(mp, sc, __return_address);
 
     for_each_online_cpu(cpu) {
         gc = per_cpu_ptr(mp->m_inodegc, cpu);
         if (!llist_empty(&gc->list)) {
             unsigned int    h = READ_ONCE(gc->shrinker_hits);
 
             WRITE_ONCE(gc->shrinker_hits, h + 1);
             mod_delayed_work_on(cpu, mp->m_inodegc_wq, &gc->work, 0);
             no_items = false;
         }
     }
 
     /*
      * If there are no inodes to inactivate, we don't want the shrinker
      * to think there's deferred work to call us back about.
      */
     if (no_items)
         return LONG_MAX;
 
     return SHRINK_STOP;
 }
 
 /* Register a shrinker so we can accelerate inodegc and throttle queuing. */
 int
 xfs_inodegc_register_shrinker(
     struct xfs_mount    *mp)
 {
     struct shrinker     *shrink = &mp->m_inodegc_shrinker;
 
     shrink->count_objects = xfs_inodegc_shrinker_count;
     shrink->scan_objects = xfs_inodegc_shrinker_scan;
     shrink->seeks = 0;
     shrink->flags = SHRINKER_NONSLAB;
     shrink->batch = XFS_INODEGC_SHRINKER_BATCH;
 
     return register_shrinker(shrink, "xfs-inodegc:%s", mp->m_super->s_id);
 }

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