text: /*
   * Copyright (c) 2000-2005 Silicon Graphics, Inc.
   * All Rights Reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it would be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write the Free Software Foundation,
   * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   */
  #include "xfs.h"
  #include "xfs_fs.h"
  #include "xfs_format.h"
  #include "xfs_log_format.h"
  #include "xfs_trans_resv.h"
  #include "xfs_sb.h"
  #include "xfs_mount.h"
  #include "xfs_inode.h"
  #include "xfs_error.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 <linux/kthread.h>
  #include <linux/freezer.h>
  
  /*
   * Allocate and initialise an xfs_inode.
   */
  struct xfs_inode *
  xfs_inode_alloc(
  	struct xfs_mount	*mp,
  	xfs_ino_t		ino)
  {
  	struct xfs_inode	*ip;
  
  	/*
  	 * if this didn't occur in transactions, we could use
  	 * KM_MAYFAIL and return NULL here on ENOMEM. Set the
  	 * code up to do this anyway.
  	 */
  	ip = kmem_zone_alloc(xfs_inode_zone, KM_SLEEP);
  	if (!ip)
  		return NULL;
  	if (inode_init_always(mp->m_super, VFS_I(ip))) {
  		kmem_zone_free(xfs_inode_zone, ip);
  		return NULL;
  	}
  
  	/* VFS doesn't initialise i_mode! */
  	VFS_I(ip)->i_mode = 0;
  
  	XFS_STATS_INC(mp, vn_active);
  	ASSERT(atomic_read(&ip->i_pincount) == 0);
  	ASSERT(!spin_is_locked(&ip->i_flags_lock));
  	ASSERT(!xfs_isiflocked(ip));
  	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_afp = NULL;
  	ip->i_cowfp = NULL;
  	ip->i_cnextents = 0;
  	ip->i_cformat = XFS_DINODE_FMT_EXTENTS;
  	memset(&ip->i_df, 0, sizeof(xfs_ifork_t));
  	ip->i_flags = 0;
  	ip->i_delayed_blks = 0;
  	memset(&ip->i_d, 0, sizeof(ip->i_d));
  
  	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, XFS_DATA_FORK);
  		break;
  	}
  
  	if (ip->i_afp)
  		xfs_idestroy_fork(ip, XFS_ATTR_FORK);
  	if (ip->i_cowfp)
  		xfs_idestroy_fork(ip, XFS_COW_FORK);
  
  	if (ip->i_itemp) {
  		ASSERT(!(ip->i_itemp->ili_item.li_flags & XFS_LI_IN_AIL));
  		xfs_inode_item_destroy(ip);
  		ip->i_itemp = NULL;
  	}
  
  	kmem_zone_free(xfs_inode_zone, 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);
  	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_isiflocked(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. 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 a new inode reclaim pass if there are reclaimable inodes and there
   * isn't a reclaim pass already in progress. By default it runs every 5s based
   * on the xfs periodic sync default of 30s. Perhaps this should have it's own
   * tunable, but that can be done if this method proves to be ineffective or too
   * aggressive.
   */
  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();
  }
  
  /*
   * 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. It scans as quickly as possible avoiding locked inodes or those
   * already being flushed, and once done schedules a future pass.
   */
  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_reclaim_inodes(mp, SYNC_TRYLOCK);
  	xfs_reclaim_work_queue(mp);
  }
  
  static void
  xfs_perag_set_reclaim_tag(
  	struct xfs_perag	*pag)
  {
  	struct xfs_mount	*mp = pag->pag_mount;
  
  	ASSERT(spin_is_locked(&pag->pag_ici_lock));
  	if (pag->pag_ici_reclaimable++)
  		return;
  
  	/* propagate the reclaim tag up into the perag radix tree */
  	spin_lock(&mp->m_perag_lock);
  	radix_tree_tag_set(&mp->m_perag_tree, pag->pag_agno,
  			   XFS_ICI_RECLAIM_TAG);
  	spin_unlock(&mp->m_perag_lock);
  
  	/* schedule periodic background inode reclaim */
  	xfs_reclaim_work_queue(mp);
  
  	trace_xfs_perag_set_reclaim(mp, pag->pag_agno, -1, _RET_IP_);
  }
  
  static void
  xfs_perag_clear_reclaim_tag(
  	struct xfs_perag	*pag)
  {
  	struct xfs_mount	*mp = pag->pag_mount;
  
  	ASSERT(spin_is_locked(&pag->pag_ici_lock));
  	if (--pag->pag_ici_reclaimable)
  		return;
  
  	/* clear the reclaim tag from the perag radix tree */
  	spin_lock(&mp->m_perag_lock);
  	radix_tree_tag_clear(&mp->m_perag_tree, pag->pag_agno,
  			     XFS_ICI_RECLAIM_TAG);
  	spin_unlock(&mp->m_perag_lock);
  	trace_xfs_perag_clear_reclaim(mp, pag->pag_agno, -1, _RET_IP_);
  }
  
  
  /*
   * 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.
   */
  void
  xfs_inode_set_reclaim_tag(
  	struct xfs_inode	*ip)
  {
  	struct xfs_mount	*mp = ip->i_mount;
  	struct xfs_perag	*pag;
  
  	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);
  
  	radix_tree_tag_set(&pag->pag_ici_root, XFS_INO_TO_AGINO(mp, ip->i_ino),
  			   XFS_ICI_RECLAIM_TAG);
  	xfs_perag_set_reclaim_tag(pag);
  	__xfs_iflags_set(ip, XFS_IRECLAIMABLE);
  
  	spin_unlock(&ip->i_flags_lock);
  	spin_unlock(&pag->pag_ici_lock);
  	xfs_perag_put(pag);
  }
  
  STATIC void
  xfs_inode_clear_reclaim_tag(
  	struct xfs_perag	*pag,
  	xfs_ino_t		ino)
  {
  	radix_tree_tag_clear(&pag->pag_ici_root,
  			     XFS_INO_TO_AGINO(pag->pag_mount, ino),
  			     XFS_ICI_RECLAIM_TAG);
  	xfs_perag_clear_reclaim_tag(pag);
  }
  
  /*
   * 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->i_version;
  	umode_t		mode = inode->i_mode;
  
  	error = inode_init_always(mp->m_super, inode);
  
  	set_nlink(inode, nlink);
  	inode->i_generation = generation;
  	inode->i_version = version;
  	inode->i_mode = mode;
  	return error;
  }
  
  /*
   * 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) {
  		trace_xfs_iget_skip(ip);
  		XFS_STATS_INC(mp, xs_ig_frecycle);
  		error = -EAGAIN;
  		goto out_error;
  	}
  
  
  	/*
  	 * If we are racing with another cache hit that is currently
  	 * instantiating this inode or currently recycling it out of
  	 * reclaimabe state, wait for the initialisation to complete
  	 * before continuing.
  	 *
  	 * 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)) {
  		trace_xfs_iget_skip(ip);
  		XFS_STATS_INC(mp, xs_ig_frecycle);
  		error = -EAGAIN;
  		goto out_error;
  	}
  
  	/*
  	 * If lookup is racing with unlink return an error immediately.
  	 */
  	if (VFS_I(ip)->i_mode == 0 && !(flags & XFS_IGET_CREATE)) {
  		error = -ENOENT;
  		goto out_error;
  	}
  
  	/*
  	 * If IRECLAIMABLE is set, we've torn down the VFS inode already.
  	 * Need to carefully get it back into useable state.
  	 */
  	if (ip->i_flags & XFS_IRECLAIMABLE) {
  		trace_xfs_iget_reclaim(ip);
  
  		/*
  		 * We need to set XFS_IRECLAIM to prevent xfs_reclaim_inode
  		 * from stomping over us while we recycle the inode.  We can't
  		 * clear the radix tree reclaimable 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();
  
  		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);
  			trace_xfs_iget_reclaim_fail(ip);
  			goto out_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_inode_clear_reclaim_tag(pag, ip->i_ino);
  		inode->i_state = I_NEW;
  
  		ASSERT(!rwsem_is_locked(&inode->i_rwsem));
  		init_rwsem(&inode->i_rwsem);
  
  		spin_unlock(&ip->i_flags_lock);
  		spin_unlock(&pag->pag_ici_lock);
  	} else {
  		/* If the VFS inode is being torn down, pause and try again. */
  		if (!igrab(inode)) {
  			trace_xfs_iget_skip(ip);
  			error = -EAGAIN;
  			goto out_error;
  		}
  
  		/* 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);
  
  	xfs_iflags_clear(ip, XFS_ISTALE | XFS_IDONTCACHE);
  	XFS_STATS_INC(mp, xs_ig_found);
  
  	return 0;
  
  out_error:
  	spin_unlock(&ip->i_flags_lock);
  	rcu_read_unlock();
  	return error;
  }
  
  
  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_iread(mp, tp, ip, flags);
  	if (error)
  		goto out_destroy;
  
  	trace_xfs_iget_miss(ip);
  
  	if ((VFS_I(ip)->i_mode == 0) && !(flags & XFS_IGET_CREATE)) {
  		error = -ENOENT;
  		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)
  		iflags |= XFS_IDONTCACHE;
  	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.
   * This flag parameter indicates how and if the inode's IO lock and inode lock
   * should be taken.
   *
   * mp -- the mount point structure for the current file system.  It points
   *       to the inode hash table.
   * tp -- a pointer to the current transaction if there is one.  This is
   *       simply passed through to the xfs_iread() call.
   * ino -- the number of the inode desired.  This is the unique identifier
   *        within the file system for the inode being requested.
   * lock_flags -- flags indicating how to lock the inode.  See the comment
   *		 for xfs_ilock() for a list of valid values.
   */
  int
  xfs_iget(
  	xfs_mount_t	*mp,
  	xfs_trans_t	*tp,
  	xfs_ino_t	ino,
  	uint		flags,
  	uint		lock_flags,
  	xfs_inode_t	**ipp)
  {
  	xfs_inode_t	*ip;
  	int		error;
  	xfs_perag_t	*pag;
  	xfs_agino_t	agino;
  
  	/*
  	 * xfs_reclaim_inode() uses the ILOCK to ensure an inode
  	 * doesn't get freed while it's being referenced during a
  	 * radix tree traversal here.  It assumes this function
  	 * aqcuires only the ILOCK (and therefore it has no need to
  	 * involve the IOLOCK in this synchronization).
  	 */
  	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();
  		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_ialloc 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 (error == -EAGAIN) {
  		delay(1);
  		goto again;
  	}
  	xfs_perag_put(pag);
  	return error;
  }
  
  /*
   * 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
  
  STATIC int
  xfs_inode_ag_walk_grab(
  	struct xfs_inode	*ip)
  {
  	struct inode		*inode = VFS_I(ip);
  
  	ASSERT(rcu_read_lock_held());
  
  	/*
  	 * check for stale RCU freed inode
  	 *
  	 * If the inode has been reallocated, it doesn't matter if it's not in
  	 * the AG we are walking - we are walking for writeback, so if it
  	 * passes all the "valid inode" checks and is dirty, then we'll write
  	 * it back anyway.  If it has been reallocated and still being
  	 * initialised, the XFS_INEW check below will catch it.
  	 */
  	spin_lock(&ip->i_flags_lock);
  	if (!ip->i_ino)
  		goto out_unlock_noent;
  
  	/* avoid new or reclaimable inodes. Leave for reclaim code to flush */
  	if (__xfs_iflags_test(ip, XFS_INEW | XFS_IRECLAIMABLE | XFS_IRECLAIM))
  		goto out_unlock_noent;
  	spin_unlock(&ip->i_flags_lock);
  
  	/* nothing to sync during shutdown */
  	if (XFS_FORCED_SHUTDOWN(ip->i_mount))
  		return -EFSCORRUPTED;
  
  	/* If we can't grab the inode, it must on it's way to reclaim. */
  	if (!igrab(inode))
  		return -ENOENT;
  
  	/* inode is valid */
  	return 0;
  
  out_unlock_noent:
  	spin_unlock(&ip->i_flags_lock);
  	return -ENOENT;
  }
  
  STATIC int
  xfs_inode_ag_walk(
  	struct xfs_mount	*mp,
  	struct xfs_perag	*pag,
  	int			(*execute)(struct xfs_inode *ip, int flags,
  					   void *args),
  	int			flags,
  	void			*args,
  	int			tag)
  {
  	uint32_t		first_index;
  	int			last_error = 0;
  	int			skipped;
  	int			done;
  	int			nr_found;
  
  restart:
  	done = 0;
  	skipped = 0;
  	first_index = 0;
  	nr_found = 0;
  	do {
  		struct xfs_inode *batch[XFS_LOOKUP_BATCH];
  		int		error = 0;
  		int		i;
  
  		rcu_read_lock();
  
  		if (tag == -1)
  			nr_found = radix_tree_gang_lookup(&pag->pag_ici_root,
  					(void **)batch, first_index,
  					XFS_LOOKUP_BATCH);
  		else
  			nr_found = radix_tree_gang_lookup_tag(
  					&pag->pag_ici_root,
  					(void **) batch, first_index,
  					XFS_LOOKUP_BATCH, tag);
  
  		if (!nr_found) {
  			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_inode_ag_walk_grab(ip))
  				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 = 1;
  		}
  
  		/* unlock now we've grabbed the inodes. */
  		rcu_read_unlock();
  
  		for (i = 0; i < nr_found; i++) {
  			if (!batch[i])
  				continue;
  			error = execute(batch[i], flags, args);
  			IRELE(batch[i]);
  			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();
  
  	} while (nr_found && !done);
  
  	if (skipped) {
  		delay(1);
  		goto restart;
  	}
  	return last_error;
  }
  
  /*
   * Background scanning to trim post-EOF preallocated space. This is queued
   * based on the 'speculative_prealloc_lifetime' tunable (5m by default).
   */
  void
  xfs_queue_eofblocks(
  	struct xfs_mount *mp)
  {
  	rcu_read_lock();
  	if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_EOFBLOCKS_TAG))
  		queue_delayed_work(mp->m_eofblocks_workqueue,
  				   &mp->m_eofblocks_work,
  				   msecs_to_jiffies(xfs_eofb_secs * 1000));
  	rcu_read_unlock();
  }
  
  void
  xfs_eofblocks_worker(
  	struct work_struct *work)
  {
  	struct xfs_mount *mp = container_of(to_delayed_work(work),
  				struct xfs_mount, m_eofblocks_work);
  	xfs_icache_free_eofblocks(mp, NULL);
  	xfs_queue_eofblocks(mp);
  }
  
  /*
   * Background scanning to trim preallocated CoW space. This is queued
   * based on the 'speculative_cow_prealloc_lifetime' tunable (5m by default).
   * (We'll just piggyback on the post-EOF prealloc space workqueue.)
   */
  STATIC void
  xfs_queue_cowblocks(
  	struct xfs_mount *mp)
  {
  	rcu_read_lock();
  	if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_COWBLOCKS_TAG))
  		queue_delayed_work(mp->m_eofblocks_workqueue,
  				   &mp->m_cowblocks_work,
  				   msecs_to_jiffies(xfs_cowb_secs * 1000));
  	rcu_read_unlock();
  }
  
  void
  xfs_cowblocks_worker(
  	struct work_struct *work)
  {
  	struct xfs_mount *mp = container_of(to_delayed_work(work),
  				struct xfs_mount, m_cowblocks_work);
  	xfs_icache_free_cowblocks(mp, NULL);
  	xfs_queue_cowblocks(mp);
  }
  
  int
  xfs_inode_ag_iterator(
  	struct xfs_mount	*mp,
  	int			(*execute)(struct xfs_inode *ip, int flags,
  					   void *args),
  	int			flags,
  	void			*args)
  {
  	struct xfs_perag	*pag;
  	int			error = 0;
  	int			last_error = 0;
  	xfs_agnumber_t		ag;
  
  	ag = 0;
  	while ((pag = xfs_perag_get(mp, ag))) {
  		ag = pag->pag_agno + 1;
  		error = xfs_inode_ag_walk(mp, pag, execute, flags, args, -1);
  		xfs_perag_put(pag);
  		if (error) {
  			last_error = error;
  			if (error == -EFSCORRUPTED)
  				break;
  		}
  	}
  	return last_error;
  }
  
  int
  xfs_inode_ag_iterator_tag(
  	struct xfs_mount	*mp,
  	int			(*execute)(struct xfs_inode *ip, int flags,
  					   void *args),
  	int			flags,
  	void			*args,
  	int			tag)
  {
  	struct xfs_perag	*pag;
  	int			error = 0;
  	int			last_error = 0;
  	xfs_agnumber_t		ag;
  
  	ag = 0;
  	while ((pag = xfs_perag_get_tag(mp, ag, tag))) {
  		ag = pag->pag_agno + 1;
  		error = xfs_inode_ag_walk(mp, pag, execute, flags, args, tag);
  		xfs_perag_put(pag);
  		if (error) {
  			last_error = error;
  			if (error == -EFSCORRUPTED)
  				break;
  		}
  	}
  	return last_error;
  }
  
  /*
   * Grab the inode for reclaim exclusively.
   * Return 0 if we grabbed it, non-zero otherwise.
   */
  STATIC int
  xfs_reclaim_inode_grab(
  	struct xfs_inode	*ip,
  	int			flags)
  {
  	ASSERT(rcu_read_lock_held());
  
  	/* quick check for stale RCU freed inode */
  	if (!ip->i_ino)
  		return 1;
  
  	/*
  	 * If we are asked for non-blocking operation, do unlocked checks to
  	 * see if the inode already is being flushed or in reclaim to avoid
  	 * lock traffic.
  	 */
  	if ((flags & SYNC_TRYLOCK) &&
  	    __xfs_iflags_test(ip, XFS_IFLOCK | XFS_IRECLAIM))
  		return 1;
  
  	/*
  	 * The radix tree lock here protects a thread in xfs_iget from racing
  	 * with us starting reclaim on the inode.  Once we have the
  	 * XFS_IRECLAIM flag set it will not touch us.
  	 *
  	 * Due to RCU lookup, we may find inodes that have been freed and only
  	 * have XFS_IRECLAIM set.  Indeed, we may see reallocated inodes that
  	 * aren't candidates for reclaim at all, so we must check the
  	 * XFS_IRECLAIMABLE is set first before proceeding to reclaim.
  	 */
  	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 1;
  	}
  	__xfs_iflags_set(ip, XFS_IRECLAIM);
  	spin_unlock(&ip->i_flags_lock);
  	return 0;
  }
  
  /*
   * Inodes in different states need to be treated differently. The following
   * table lists the inode states and the reclaim actions necessary:
   *
   *	inode state	     iflush ret		required action
   *      ---------------      ----------         ---------------
   *	bad			-		reclaim
   *	shutdown		EIO		unpin and reclaim
   *	clean, unpinned		0		reclaim
   *	stale, unpinned		0		reclaim
   *	clean, pinned(*)	0		requeue
   *	stale, pinned		EAGAIN		requeue
   *	dirty, async		-		requeue
   *	dirty, sync		0		reclaim
   *
   * (*) dgc: I don't think the clean, pinned state is possible but it gets
   * handled anyway given the order of checks implemented.
   *
   * Also, because we get the flush lock first, we know that any inode that has
   * been flushed delwri has had the flush completed by the time we check that
   * the inode is clean.
   *
   * Note that because the inode is flushed delayed write by AIL pushing, the
   * flush lock may already be held here and waiting on it can result in very
   * long latencies.  Hence for sync reclaims, where we wait on the flush lock,
   * the caller should push the AIL first before trying to reclaim inodes to
   * minimise the amount of time spent waiting.  For background relaim, we only
   * bother to reclaim clean inodes anyway.
   *
   * Hence the order of actions after gaining the locks should be:
   *	bad		=> reclaim
   *	shutdown	=> unpin and reclaim
   *	pinned, async	=> requeue
   *	pinned, sync	=> unpin
   *	stale		=> reclaim
   *	clean		=> reclaim
   *	dirty, async	=> requeue
   *	dirty, sync	=> flush, wait and reclaim
   */
  STATIC int
  xfs_reclaim_inode(
  	struct xfs_inode	*ip,
  	struct xfs_perag	*pag,
  	int			sync_mode)
  {
  	struct xfs_buf		*bp = NULL;
  	xfs_ino_t		ino = ip->i_ino; /* for radix_tree_delete */
  	int			error;
  
  restart:
  	error = 0;
  	xfs_ilock(ip, XFS_ILOCK_EXCL);
  	if (!xfs_iflock_nowait(ip)) {
  		if (!(sync_mode & SYNC_WAIT))
  			goto out;
  		xfs_iflock(ip);
  	}
  
  	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
  		xfs_iunpin_wait(ip);
  		/* xfs_iflush_abort() drops the flush lock */
  		xfs_iflush_abort(ip, false);
  		goto reclaim;
  	}
  	if (xfs_ipincount(ip)) {
  		if (!(sync_mode & SYNC_WAIT))
  			goto out_ifunlock;
  		xfs_iunpin_wait(ip);
  	}
  	if (xfs_iflags_test(ip, XFS_ISTALE) || xfs_inode_clean(ip)) {
  		xfs_ifunlock(ip);
  		goto reclaim;
  	}
  
  	/*
  	 * Never flush out dirty data during non-blocking reclaim, as it would
  	 * just contend with AIL pushing trying to do the same job.
  	 */
  	if (!(sync_mode & SYNC_WAIT))
  		goto out_ifunlock;
  
  	/*
  	 * Now we have an inode that needs flushing.
  	 *
  	 * Note that xfs_iflush will never block on the inode buffer lock, as
  	 * xfs_ifree_cluster() can lock the inode buffer before it locks the
  	 * ip->i_lock, and we are doing the exact opposite here.  As a result,
  	 * doing a blocking xfs_imap_to_bp() to get the cluster buffer would
  	 * result in an ABBA deadlock with xfs_ifree_cluster().
  	 *
  	 * As xfs_ifree_cluser() must gather all inodes that are active in the
  	 * cache to mark them stale, if we hit this case we don't actually want
  	 * to do IO here - we want the inode marked stale so we can simply
  	 * reclaim it.  Hence if we get an EAGAIN error here,  just unlock the
  	 * inode, back off and try again.  Hopefully the next pass through will
  	 * see the stale flag set on the inode.
  	 */
  	error = xfs_iflush(ip, &bp);
  	if (error == -EAGAIN) {
  		xfs_iunlock(ip, XFS_ILOCK_EXCL);
  		/* backoff longer than in xfs_ifree_cluster */
  		delay(2);
  		goto restart;
  	}
  
  	if (!error) {
  		error = xfs_bwrite(bp);
  		xfs_buf_relse(bp);
  	}
  
  reclaim:
  	ASSERT(!xfs_isiflocked(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() can be guaranteed to detect races with us here.
  	 * By doing this, we guarantee that once xfs_iflush_cluster has locked
  	 * XFS_ILOCK that it will see either a valid, flushable inode that will
  	 * serialise correctly, or it will see a clean (and invalid) inode that
  	 * it can skip.
  	 */
  	spin_lock(&ip->i_flags_lock);
  	ip->i_flags = XFS_IRECLAIM;
  	ip->i_ino = 0;
  	spin_unlock(&ip->i_flags_lock);
  
  	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_reclaim_tag(pag);
  	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);
  	xfs_qm_dqdetach(ip);
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  
  	__xfs_inode_free(ip);
  	return error;
  
  out_ifunlock:
  	xfs_ifunlock(ip);
  out:
  	xfs_iflags_clear(ip, XFS_IRECLAIM);
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  	/*
  	 * We could return -EAGAIN here to make reclaim rescan the inode tree in
  	 * a short while. However, this just burns CPU time scanning the tree
  	 * waiting for IO to complete and the reclaim work never goes back to
  	 * the idle state. Instead, return 0 to let the next scheduled
  	 * background reclaim attempt to reclaim the inode again.
  	 */
  	return 0;
  }
  
  /*
   * Walk the AGs and reclaim the inodes in them. Even if the filesystem is
   * corrupted, we still want to try to reclaim all the inodes. If we don't,
   * then a shut down during filesystem unmount reclaim walk leak all the
   * unreclaimed inodes.
   */
  STATIC int
  xfs_reclaim_inodes_ag(
  	struct xfs_mount	*mp,
  	int			flags,
  	int			*nr_to_scan)
  {
  	struct xfs_perag	*pag;
  	int			error = 0;
  	int			last_error = 0;
  	xfs_agnumber_t		ag;
  	int			trylock = flags & SYNC_TRYLOCK;
  	int			skipped;
  
  restart:
  	ag = 0;
  	skipped = 0;
  	while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
  		unsigned long	first_index = 0;
  		int		done = 0;
  		int		nr_found = 0;
  
  		ag = pag->pag_agno + 1;
  
  		if (trylock) {
  			if (!mutex_trylock(&pag->pag_ici_reclaim_lock)) {
  				skipped++;
  				xfs_perag_put(pag);
  				continue;
  			}
  			first_index = pag->pag_ici_reclaim_cursor;
  		} else
  			mutex_lock(&pag->pag_ici_reclaim_lock);
  
  		do {
  			struct xfs_inode *batch[XFS_LOOKUP_BATCH];
  			int	i;
  
  			rcu_read_lock();
  			nr_found = radix_tree_gang_lookup_tag(
  					&pag->pag_ici_root,
  					(void **)batch, first_index,
  					XFS_LOOKUP_BATCH,
  					XFS_ICI_RECLAIM_TAG);
  			if (!nr_found) {
  				done = 1;
  				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_reclaim_inode_grab(ip, flags))
  					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 = 1;
  			}
  
  			/* unlock now we've grabbed the inodes. */
  			rcu_read_unlock();
  
  			for (i = 0; i < nr_found; i++) {
  				if (!batch[i])
  					continue;
  				error = xfs_reclaim_inode(batch[i], pag, flags);
  				if (error && last_error != -EFSCORRUPTED)
  					last_error = error;
  			}
  
  			*nr_to_scan -= XFS_LOOKUP_BATCH;
  
  			cond_resched();
  
  		} while (nr_found && !done && *nr_to_scan > 0);
  
  		if (trylock && !done)
  			pag->pag_ici_reclaim_cursor = first_index;
  		else
  			pag->pag_ici_reclaim_cursor = 0;
  		mutex_unlock(&pag->pag_ici_reclaim_lock);
  		xfs_perag_put(pag);
  	}
  
  	/*
  	 * if we skipped any AG, and we still have scan count remaining, do
  	 * another pass this time using blocking reclaim semantics (i.e
  	 * waiting on the reclaim locks and ignoring the reclaim cursors). This
  	 * ensure that when we get more reclaimers than AGs we block rather
  	 * than spin trying to execute reclaim.
  	 */
  	if (skipped && (flags & SYNC_WAIT) && *nr_to_scan > 0) {
  		trylock = 0;
  		goto restart;
  	}
  	return last_error;
  }
  
  int
  xfs_reclaim_inodes(
  	xfs_mount_t	*mp,
  	int		mode)
  {
  	int		nr_to_scan = INT_MAX;
  
  	return xfs_reclaim_inodes_ag(mp, mode, &nr_to_scan);
  }
  
  /*
   * Scan a certain number of inodes for reclaim.
   *
   * When called we make sure that there is a background (fast) inode reclaim in
   * progress, while we will throttle the speed of reclaim via doing synchronous
   * reclaim of inodes. That means if we come across dirty inodes, we wait for
   * them to be cleaned, which we hope will not be very long due to the
   * background walker having already kicked the IO off on those dirty inodes.
   */
  long
  xfs_reclaim_inodes_nr(
  	struct xfs_mount	*mp,
  	int			nr_to_scan)
  {
  	/* kick background reclaimer and push the AIL */
  	xfs_reclaim_work_queue(mp);
  	xfs_ail_push_all(mp->m_ail);
  
  	return xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr_to_scan);
  }
  
  /*
   * Return the number of reclaimable inodes in the filesystem for
   * the shrinker to determine how much to reclaim.
   */
  int
  xfs_reclaim_inodes_count(
  	struct xfs_mount	*mp)
  {
  	struct xfs_perag	*pag;
  	xfs_agnumber_t		ag = 0;
  	int			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 int
  xfs_inode_match_id(
  	struct xfs_inode	*ip,
  	struct xfs_eofblocks	*eofb)
  {
  	if ((eofb->eof_flags & XFS_EOF_FLAGS_UID) &&
  	    !uid_eq(VFS_I(ip)->i_uid, eofb->eof_uid))
  		return 0;
  
  	if ((eofb->eof_flags & XFS_EOF_FLAGS_GID) &&
  	    !gid_eq(VFS_I(ip)->i_gid, eofb->eof_gid))
  		return 0;
  
  	if ((eofb->eof_flags & XFS_EOF_FLAGS_PRID) &&
  	    xfs_get_projid(ip) != eofb->eof_prid)
  		return 0;
  
  	return 1;
  }
  
  /*
   * A union-based inode filtering algorithm. Process the inode if any of the
   * criteria match. This is for global/internal scans only.
   */
  STATIC int
  xfs_inode_match_id_union(
  	struct xfs_inode	*ip,
  	struct xfs_eofblocks	*eofb)
  {
  	if ((eofb->eof_flags & XFS_EOF_FLAGS_UID) &&
  	    uid_eq(VFS_I(ip)->i_uid, eofb->eof_uid))
  		return 1;
  
  	if ((eofb->eof_flags & XFS_EOF_FLAGS_GID) &&
  	    gid_eq(VFS_I(ip)->i_gid, eofb->eof_gid))
  		return 1;
  
  	if ((eofb->eof_flags & XFS_EOF_FLAGS_PRID) &&
  	    xfs_get_projid(ip) == eofb->eof_prid)
  		return 1;
  
  	return 0;
  }
  
  STATIC int
  xfs_inode_free_eofblocks(
  	struct xfs_inode	*ip,
  	int			flags,
  	void			*args)
  {
  	int ret = 0;
  	struct xfs_eofblocks *eofb = args;
  	int match;
  
  	if (!xfs_can_free_eofblocks(ip, false)) {
  		/* inode could be preallocated or append-only */
  		trace_xfs_inode_free_eofblocks_invalid(ip);
  		xfs_inode_clear_eofblocks_tag(ip);
  		return 0;
  	}
  
  	/*
  	 * If the mapping is dirty the operation can block and wait for some
  	 * time. Unless we are waiting, skip it.
  	 */
  	if (!(flags & SYNC_WAIT) &&
  	    mapping_tagged(VFS_I(ip)->i_mapping, PAGECACHE_TAG_DIRTY))
  		return 0;
  
  	if (eofb) {
  		if (eofb->eof_flags & XFS_EOF_FLAGS_UNION)
  			match = xfs_inode_match_id_union(ip, eofb);
  		else
  			match = xfs_inode_match_id(ip, eofb);
  		if (!match)
  			return 0;
  
  		/* skip the inode if the file size is too small */
  		if (eofb->eof_flags & XFS_EOF_FLAGS_MINFILESIZE &&
  		    XFS_ISIZE(ip) < eofb->eof_min_file_size)
  			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 (flags & SYNC_WAIT)
  			ret = -EAGAIN;
  		return ret;
  	}
  	ret = xfs_free_eofblocks(ip);
  	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
  
  	return ret;
  }
  
  static int
  __xfs_icache_free_eofblocks(
  	struct xfs_mount	*mp,
  	struct xfs_eofblocks	*eofb,
  	int			(*execute)(struct xfs_inode *ip, int flags,
  					   void *args),
  	int			tag)
  {
  	int flags = SYNC_TRYLOCK;
  
  	if (eofb && (eofb->eof_flags & XFS_EOF_FLAGS_SYNC))
  		flags = SYNC_WAIT;
  
  	return xfs_inode_ag_iterator_tag(mp, execute, flags,
  					 eofb, tag);
  }
  
  int
  xfs_icache_free_eofblocks(
  	struct xfs_mount	*mp,
  	struct xfs_eofblocks	*eofb)
  {
  	return __xfs_icache_free_eofblocks(mp, eofb, xfs_inode_free_eofblocks,
  			XFS_ICI_EOFBLOCKS_TAG);
  }
  
  /*
   * Run eofblocks scans on the quotas applicable to the inode. For inodes with
   * multiple quotas, we don't know exactly which quota caused an allocation
   * failure. We make a best effort by including each quota under low free space
   * conditions (less than 1% free space) in the scan.
   */
  static int
  __xfs_inode_free_quota_eofblocks(
  	struct xfs_inode	*ip,
  	int			(*execute)(struct xfs_mount *mp,
  					   struct xfs_eofblocks	*eofb))
  {
  	int scan = 0;
  	struct xfs_eofblocks eofb = {0};
  	struct xfs_dquot *dq;
  
  	/*
  	 * Run a sync scan to increase effectiveness and use the union filter to
  	 * cover all applicable quotas in a single scan.
  	 */
  	eofb.eof_flags = XFS_EOF_FLAGS_UNION|XFS_EOF_FLAGS_SYNC;
  
  	if (XFS_IS_UQUOTA_ENFORCED(ip->i_mount)) {
  		dq = xfs_inode_dquot(ip, XFS_DQ_USER);
  		if (dq && xfs_dquot_lowsp(dq)) {
  			eofb.eof_uid = VFS_I(ip)->i_uid;
  			eofb.eof_flags |= XFS_EOF_FLAGS_UID;
  			scan = 1;
  		}
  	}
  
  	if (XFS_IS_GQUOTA_ENFORCED(ip->i_mount)) {
  		dq = xfs_inode_dquot(ip, XFS_DQ_GROUP);
  		if (dq && xfs_dquot_lowsp(dq)) {
  			eofb.eof_gid = VFS_I(ip)->i_gid;
  			eofb.eof_flags |= XFS_EOF_FLAGS_GID;
  			scan = 1;
  		}
  	}
  
  	if (scan)
  		execute(ip->i_mount, &eofb);
  
  	return scan;
  }
  
  int
  xfs_inode_free_quota_eofblocks(
  	struct xfs_inode *ip)
  {
  	return __xfs_inode_free_quota_eofblocks(ip, xfs_icache_free_eofblocks);
  }
  
  static void
  __xfs_inode_set_eofblocks_tag(
  	xfs_inode_t	*ip,
  	void		(*execute)(struct xfs_mount *mp),
  	void		(*set_tp)(struct xfs_mount *mp, xfs_agnumber_t agno,
  				  int error, unsigned long caller_ip),
  	int		tag)
  {
  	struct xfs_mount *mp = ip->i_mount;
  	struct xfs_perag *pag;
  	int tagged;
  
  	/*
  	 * 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 & XFS_IEOFBLOCKS)
  		return;
  	spin_lock(&ip->i_flags_lock);
  	ip->i_flags |= XFS_IEOFBLOCKS;
  	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);
  
  	tagged = radix_tree_tagged(&pag->pag_ici_root, tag);
  	radix_tree_tag_set(&pag->pag_ici_root,
  			   XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino), tag);
  	if (!tagged) {
  		/* propagate the eofblocks tag up into the perag radix tree */
  		spin_lock(&ip->i_mount->m_perag_lock);
  		radix_tree_tag_set(&ip->i_mount->m_perag_tree,
  				   XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
  				   tag);
  		spin_unlock(&ip->i_mount->m_perag_lock);
  
  		/* kick off background trimming */
  		execute(ip->i_mount);
  
  		set_tp(ip->i_mount, pag->pag_agno, -1, _RET_IP_);
  	}
  
  	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_inode_set_eofblocks_tag(ip, xfs_queue_eofblocks,
  			trace_xfs_perag_set_eofblocks,
  			XFS_ICI_EOFBLOCKS_TAG);
  }
  
  static void
  __xfs_inode_clear_eofblocks_tag(
  	xfs_inode_t	*ip,
  	void		(*clear_tp)(struct xfs_mount *mp, xfs_agnumber_t agno,
  				    int error, unsigned long caller_ip),
  	int		tag)
  {
  	struct xfs_mount *mp = ip->i_mount;
  	struct xfs_perag *pag;
  
  	spin_lock(&ip->i_flags_lock);
  	ip->i_flags &= ~XFS_IEOFBLOCKS;
  	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);
  
  	radix_tree_tag_clear(&pag->pag_ici_root,
  			     XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino), tag);
  	if (!radix_tree_tagged(&pag->pag_ici_root, tag)) {
  		/* clear the eofblocks tag from the perag radix tree */
  		spin_lock(&ip->i_mount->m_perag_lock);
  		radix_tree_tag_clear(&ip->i_mount->m_perag_tree,
  				     XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
  				     tag);
  		spin_unlock(&ip->i_mount->m_perag_lock);
  		clear_tp(ip->i_mount, pag->pag_agno, -1, _RET_IP_);
  	}
  
  	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_inode_clear_eofblocks_tag(ip,
  			trace_xfs_perag_clear_eofblocks, XFS_ICI_EOFBLOCKS_TAG);
  }
  
  /*
   * 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,
  	int			flags,
  	void			*args)
  {
  	int ret;
  	struct xfs_eofblocks *eofb = args;
  	int match;
  	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
  
  	/*
  	 * 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_is_reflink_inode(ip) || !ifp->if_bytes) {
  		trace_xfs_inode_free_cowblocks_invalid(ip);
  		xfs_inode_clear_cowblocks_tag(ip);
  		return 0;
  	}
  
  	/*
  	 * 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 0;
  
  	if (eofb) {
  		if (eofb->eof_flags & XFS_EOF_FLAGS_UNION)
  			match = xfs_inode_match_id_union(ip, eofb);
  		else
  			match = xfs_inode_match_id(ip, eofb);
  		if (!match)
  			return 0;
  
  		/* skip the inode if the file size is too small */
  		if (eofb->eof_flags & XFS_EOF_FLAGS_MINFILESIZE &&
  		    XFS_ISIZE(ip) < eofb->eof_min_file_size)
  			return 0;
  	}
  
  	/* Free the CoW blocks */
  	xfs_ilock(ip, XFS_IOLOCK_EXCL);
  	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
  
  	ret = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, false);
  
  	xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
  	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
  
  	return ret;
  }
  
  int
  xfs_icache_free_cowblocks(
  	struct xfs_mount	*mp,
  	struct xfs_eofblocks	*eofb)
  {
  	return __xfs_icache_free_eofblocks(mp, eofb, xfs_inode_free_cowblocks,
  			XFS_ICI_COWBLOCKS_TAG);
  }
  
  int
  xfs_inode_free_quota_cowblocks(
  	struct xfs_inode *ip)
  {
  	return __xfs_inode_free_quota_eofblocks(ip, xfs_icache_free_cowblocks);
  }
  
  void
  xfs_inode_set_cowblocks_tag(
  	xfs_inode_t	*ip)
  {
  	trace_xfs_inode_set_cowblocks_tag(ip);
  	return __xfs_inode_set_eofblocks_tag(ip, xfs_queue_cowblocks,
  			trace_xfs_perag_set_cowblocks,
  			XFS_ICI_COWBLOCKS_TAG);
  }
  
  void
  xfs_inode_clear_cowblocks_tag(
  	xfs_inode_t	*ip)
  {
  	trace_xfs_inode_clear_cowblocks_tag(ip);
  	return __xfs_inode_clear_eofblocks_tag(ip,
  			trace_xfs_perag_clear_cowblocks, XFS_ICI_COWBLOCKS_TAG);
  }
  