/*
   * 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_types.h"
  #include "xfs_bit.h"
  #include "xfs_log.h"
  #include "xfs_inum.h"
  #include "xfs_trans.h"

  #include "xfs_trans_priv.h"

  #include "xfs_sb.h"
  #include "xfs_ag.h"

  #include "xfs_mount.h"
  #include "xfs_bmap_btree.h"

  #include "xfs_inode.h"
  #include "xfs_dinode.h"
  #include "xfs_error.h"

  #include "xfs_filestream.h"
  #include "xfs_vnodeops.h"

  #include "xfs_inode_item.h"

  #include "xfs_quota.h"

  #include "xfs_trace.h"

  #include "xfs_fsops.h"

  #include <linux/kthread.h>
  #include <linux/freezer.h>

  struct workqueue_struct	*xfs_syncd_wq;	/* sync workqueue */

  /*
   * 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;
  
  	if (is_bad_inode(inode)) {
  		IRELE(ip);
  		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,
  					   struct xfs_perag *pag, int flags),

  	int			flags)

  {

  	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();

  		nr_found = radix_tree_gang_lookup(&pag->pag_ici_root,

  					(void **)batch, first_index,
  					XFS_LOOKUP_BATCH);

  		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], pag, flags);
  			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;
  }

  int

  xfs_inode_ag_iterator(
  	struct xfs_mount	*mp,
  	int			(*execute)(struct xfs_inode *ip,
  					   struct xfs_perag *pag, int flags),

  	int			flags)

  {

  	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);

  		xfs_perag_put(pag);

  		if (error) {
  			last_error = error;
  			if (error == EFSCORRUPTED)
  				break;
  		}
  	}
  	return XFS_ERROR(last_error);
  }

  STATIC int
  xfs_sync_inode_data(
  	struct xfs_inode	*ip,

  	struct xfs_perag	*pag,

  	int			flags)
  {
  	struct inode		*inode = VFS_I(ip);
  	struct address_space *mapping = inode->i_mapping;
  	int			error = 0;
  
  	if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))

  		return 0;

  
  	if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED)) {
  		if (flags & SYNC_TRYLOCK)

  			return 0;

  		xfs_ilock(ip, XFS_IOLOCK_SHARED);
  	}
  
  	error = xfs_flush_pages(ip, 0, -1, (flags & SYNC_WAIT) ?

  				0 : XBF_ASYNC, FI_NONE);

  	xfs_iunlock(ip, XFS_IOLOCK_SHARED);

  	return error;
  }

  STATIC int
  xfs_sync_inode_attr(
  	struct xfs_inode	*ip,

  	struct xfs_perag	*pag,

  	int			flags)
  {
  	int			error = 0;
  
  	xfs_ilock(ip, XFS_ILOCK_SHARED);
  	if (xfs_inode_clean(ip))
  		goto out_unlock;
  	if (!xfs_iflock_nowait(ip)) {
  		if (!(flags & SYNC_WAIT))
  			goto out_unlock;
  		xfs_iflock(ip);
  	}
  
  	if (xfs_inode_clean(ip)) {
  		xfs_ifunlock(ip);
  		goto out_unlock;
  	}

  	error = xfs_iflush(ip, flags);

  	/*
  	 * We don't want to try again on non-blocking flushes that can't run
  	 * again immediately. If an inode really must be written, then that's
  	 * what the SYNC_WAIT flag is for.
  	 */
  	if (error == EAGAIN) {
  		ASSERT(!(flags & SYNC_WAIT));
  		error = 0;
  	}

   out_unlock:
  	xfs_iunlock(ip, XFS_ILOCK_SHARED);
  	return error;
  }

  /*
   * Write out pagecache data for the whole filesystem.
   */

  STATIC int

  xfs_sync_data(
  	struct xfs_mount	*mp,
  	int			flags)

  {

  	int			error;

  	ASSERT((flags & ~(SYNC_TRYLOCK|SYNC_WAIT)) == 0);

  	error = xfs_inode_ag_iterator(mp, xfs_sync_inode_data, flags);

  	if (error)
  		return XFS_ERROR(error);

  	xfs_log_force(mp, (flags & SYNC_WAIT) ? XFS_LOG_SYNC : 0);

  	return 0;
  }

  /*
   * Write out inode metadata (attributes) for the whole filesystem.
   */

  STATIC int

  xfs_sync_attr(
  	struct xfs_mount	*mp,
  	int			flags)
  {
  	ASSERT((flags & ~SYNC_WAIT) == 0);

  	return xfs_inode_ag_iterator(mp, xfs_sync_inode_attr, flags);

  }

  STATIC int

  xfs_sync_fsdata(

  	struct xfs_mount	*mp)

  {
  	struct xfs_buf		*bp;

  	int			error;

  
  	/*

  	 * If the buffer is pinned then push on the log so we won't get stuck
  	 * waiting in the write for someone, maybe ourselves, to flush the log.
  	 *
  	 * Even though we just pushed the log above, we did not have the
  	 * superblock buffer locked at that point so it can become pinned in
  	 * between there and here.

  	 */

  	bp = xfs_getsb(mp, 0);

  	if (xfs_buf_ispinned(bp))

  		xfs_log_force(mp, 0);

  	error = xfs_bwrite(bp);
  	xfs_buf_relse(bp);
  	return error;

  }

  int
  xfs_log_dirty_inode(
  	struct xfs_inode	*ip,
  	struct xfs_perag	*pag,
  	int			flags)
  {
  	struct xfs_mount	*mp = ip->i_mount;
  	struct xfs_trans	*tp;
  	int			error;
  
  	if (!ip->i_update_core)
  		return 0;
  
  	tp = xfs_trans_alloc(mp, XFS_TRANS_FSYNC_TS);
  	error = xfs_trans_reserve(tp, 0, XFS_FSYNC_TS_LOG_RES(mp), 0, 0, 0);
  	if (error) {
  		xfs_trans_cancel(tp, 0);
  		return error;
  	}
  
  	xfs_ilock(ip, XFS_ILOCK_EXCL);
  	xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
  	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
  	return xfs_trans_commit(tp, 0);
  }

  /*

   * When remounting a filesystem read-only or freezing the filesystem, we have
   * two phases to execute. This first phase is syncing the data before we
   * quiesce the filesystem, and the second is flushing all the inodes out after
   * we've waited for all the transactions created by the first phase to
   * complete. The second phase ensures that the inodes are written to their
   * location on disk rather than just existing in transactions in the log. This
   * means after a quiesce there is no log replay required to write the inodes to
   * disk (this is the main difference between a sync and a quiesce).
   */
  /*
   * First stage of freeze - no writers will make progress now we are here,

   * so we flush delwri and delalloc buffers here, then wait for all I/O to
   * complete.  Data is frozen at that point. Metadata is not frozen,

   * transactions can still occur here so don't bother flushing the buftarg
   * because it'll just get dirty again.

   */
  int
  xfs_quiesce_data(
  	struct xfs_mount	*mp)
  {

  	int			error, error2 = 0;

  	/*
  	 * Log all pending size and timestamp updates.  The vfs writeback
  	 * code is supposed to do this, but due to its overagressive
  	 * livelock detection it will skip inodes where appending writes
  	 * were written out in the first non-blocking sync phase if their
  	 * completion took long enough that it happened after taking the
  	 * timestamp for the cut-off in the blocking phase.
  	 */
  	xfs_inode_ag_iterator(mp, xfs_log_dirty_inode, 0);

  	/* force out the log */

  	xfs_log_force(mp, XFS_LOG_SYNC);

  	/* write superblock and hoover up shutdown errors */

  	error = xfs_sync_fsdata(mp);
  
  	/* make sure all delwri buffers are written out */
  	xfs_flush_buftarg(mp->m_ddev_targp, 1);
  
  	/* mark the log as covered if needed */
  	if (xfs_log_need_covered(mp))

  		error2 = xfs_fs_log_dummy(mp);

  	/* flush data-only devices */

  	if (mp->m_rtdev_targp)

  		xfs_flush_buftarg(mp->m_rtdev_targp, 1);

  	return error ? error : error2;

  }

  STATIC void
  xfs_quiesce_fs(
  	struct xfs_mount	*mp)
  {
  	int	count = 0, pincount;

  	xfs_reclaim_inodes(mp, 0);

  	xfs_flush_buftarg(mp->m_ddev_targp, 0);

  
  	/*
  	 * This loop must run at least twice.  The first instance of the loop
  	 * will flush most meta data but that will generate more meta data
  	 * (typically directory updates).  Which then must be flushed and

  	 * logged before we can write the unmount record. We also so sync
  	 * reclaim of inodes to catch any that the above delwri flush skipped.

  	 */
  	do {

  		xfs_reclaim_inodes(mp, SYNC_WAIT);

  		xfs_sync_attr(mp, SYNC_WAIT);

  		pincount = xfs_flush_buftarg(mp->m_ddev_targp, 1);
  		if (!pincount) {
  			delay(50);
  			count++;
  		}
  	} while (count < 2);
  }
  
  /*
   * Second stage of a quiesce. The data is already synced, now we have to take
   * care of the metadata. New transactions are already blocked, so we need to

   * wait for any remaining transactions to drain out before proceeding.

   */
  void
  xfs_quiesce_attr(
  	struct xfs_mount	*mp)
  {
  	int	error = 0;
  
  	/* wait for all modifications to complete */
  	while (atomic_read(&mp->m_active_trans) > 0)
  		delay(100);
  
  	/* flush inodes and push all remaining buffers out to disk */
  	xfs_quiesce_fs(mp);

  	/*
  	 * Just warn here till VFS can correctly support
  	 * read-only remount without racing.
  	 */
  	WARN_ON(atomic_read(&mp->m_active_trans) != 0);

  
  	/* Push the superblock and write an unmount record */

  	error = xfs_log_sbcount(mp);

  	if (error)

  		xfs_warn(mp, "xfs_attr_quiesce: failed to log sb changes. "

  				"Frozen image may not be consistent.");
  	xfs_log_unmount_write(mp);
  	xfs_unmountfs_writesb(mp);
  }

  static void
  xfs_syncd_queue_sync(
  	struct xfs_mount        *mp)

  {

  	queue_delayed_work(xfs_syncd_wq, &mp->m_sync_work,
  				msecs_to_jiffies(xfs_syncd_centisecs * 10));

  }

  /*

   * Every sync period we need to unpin all items, reclaim inodes and sync
   * disk quotas.  We might need to cover the log to indicate that the

   * filesystem is idle and not frozen.

   */

  STATIC void
  xfs_sync_worker(

  	struct work_struct *work)

  {

  	struct xfs_mount *mp = container_of(to_delayed_work(work),
  					struct xfs_mount, m_sync_work);

  	int		error;

  	if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {

  		/* dgc: errors ignored here */

  		if (mp->m_super->s_frozen == SB_UNFROZEN &&
  		    xfs_log_need_covered(mp))

  			error = xfs_fs_log_dummy(mp);
  		else
  			xfs_log_force(mp, 0);

  
  		/* start pushing all the metadata that is currently dirty */
  		xfs_ail_push_all(mp->m_ail);

  	}

  
  	/* queue us up again */
  	xfs_syncd_queue_sync(mp);

  }

  /*

   * 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 syncd work 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_syncd_queue_reclaim(
  	struct xfs_mount        *mp)

  {

  	/*
  	 * We can have inodes enter reclaim after we've shut down the syncd
  	 * workqueue during unmount, so don't allow reclaim work to be queued
  	 * during unmount.
  	 */
  	if (!(mp->m_super->s_flags & MS_ACTIVE))
  		return;

  	rcu_read_lock();
  	if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
  		queue_delayed_work(xfs_syncd_wq, &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.
   */
  STATIC 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_syncd_queue_reclaim(mp);
  }
  
  /*

   * Flush delayed allocate data, attempting to free up reserved space
   * from existing allocations.  At this point a new allocation attempt
   * has failed with ENOSPC and we are in the process of scratching our
   * heads, looking about for more room.
   *
   * Queue a new data flush if there isn't one already in progress and
   * wait for completion of the flush. This means that we only ever have one
   * inode flush in progress no matter how many ENOSPC events are occurring and
   * so will prevent the system from bogging down due to every concurrent
   * ENOSPC event scanning all the active inodes in the system for writeback.
   */
  void
  xfs_flush_inodes(
  	struct xfs_inode	*ip)
  {
  	struct xfs_mount	*mp = ip->i_mount;
  
  	queue_work(xfs_syncd_wq, &mp->m_flush_work);
  	flush_work_sync(&mp->m_flush_work);
  }
  
  STATIC void
  xfs_flush_worker(
  	struct work_struct *work)
  {
  	struct xfs_mount *mp = container_of(work,
  					struct xfs_mount, m_flush_work);
  
  	xfs_sync_data(mp, SYNC_TRYLOCK);
  	xfs_sync_data(mp, SYNC_TRYLOCK | SYNC_WAIT);

  }
  
  int
  xfs_syncd_init(
  	struct xfs_mount	*mp)
  {

  	INIT_WORK(&mp->m_flush_work, xfs_flush_worker);

  	INIT_DELAYED_WORK(&mp->m_sync_work, xfs_sync_worker);

  	INIT_DELAYED_WORK(&mp->m_reclaim_work, xfs_reclaim_worker);

  	xfs_syncd_queue_sync(mp);

  	xfs_syncd_queue_reclaim(mp);

  	return 0;
  }
  
  void
  xfs_syncd_stop(
  	struct xfs_mount	*mp)
  {

  	cancel_delayed_work_sync(&mp->m_sync_work);

  	cancel_delayed_work_sync(&mp->m_reclaim_work);

  	cancel_work_sync(&mp->m_flush_work);

  }

  void
  __xfs_inode_set_reclaim_tag(
  	struct xfs_perag	*pag,
  	struct xfs_inode	*ip)
  {
  	radix_tree_tag_set(&pag->pag_ici_root,
  			   XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino),
  			   XFS_ICI_RECLAIM_TAG);

  
  	if (!pag->pag_ici_reclaimable) {
  		/* propagate the reclaim 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),
  				XFS_ICI_RECLAIM_TAG);
  		spin_unlock(&ip->i_mount->m_perag_lock);

  
  		/* schedule periodic background inode reclaim */
  		xfs_syncd_queue_reclaim(ip->i_mount);

  		trace_xfs_perag_set_reclaim(ip->i_mount, pag->pag_agno,
  							-1, _RET_IP_);
  	}

  	pag->pag_ici_reclaimable++;

  }

  /*
   * 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(
  	xfs_inode_t	*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);

  	__xfs_inode_set_reclaim_tag(pag, ip);

  	__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(

  	xfs_perag_t	*pag,
  	xfs_inode_t	*ip)
  {

  	pag->pag_ici_reclaimable--;

  	if (!pag->pag_ici_reclaimable) {
  		/* clear the reclaim 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),
  				XFS_ICI_RECLAIM_TAG);
  		spin_unlock(&ip->i_mount->m_perag_lock);
  		trace_xfs_perag_clear_reclaim(ip->i_mount, pag->pag_agno,
  							-1, _RET_IP_);
  	}

  }

  void
  __xfs_inode_clear_reclaim_tag(
  	xfs_mount_t	*mp,
  	xfs_perag_t	*pag,
  	xfs_inode_t	*ip)
  {
  	radix_tree_tag_clear(&pag->pag_ici_root,
  			XFS_INO_TO_AGINO(mp, ip->i_ino), XFS_ICI_RECLAIM_TAG);
  	__xfs_inode_clear_reclaim(pag, ip);
  }

  /*

   * 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;

  
  	/*

  	 * do some unlocked checks first to avoid unnecessary lock traffic.

  	 * The first is a flush lock check, the second is a already in reclaim
  	 * check. Only do these checks if we are not going to block on locks.
  	 */
  	if ((flags & SYNC_TRYLOCK) &&
  	    (!ip->i_flush.done || __xfs_iflags_test(ip, 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, and the return
   * value of xfs_iflush is not sufficient to get this right. The following table
   * lists the inode states and the reclaim actions necessary for non-blocking
   * reclaim:
   *
   *
   *	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, delwri ok	0		requeue
   *	dirty, delwri blocked	EAGAIN		requeue
   *	dirty, sync flush	0		reclaim

   *
   * (*) dgc: I don't think the clean, pinned state is possible but it gets
   * handled anyway given the order of checks implemented.
   *

   * As can be seen from the table, the return value of xfs_iflush() is not
   * sufficient to correctly decide the reclaim action here. The checks in
   * xfs_iflush() might look like duplicates, but they are not.
   *
   * 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. The clean inode check needs to be done before flushing
   * the inode delwri otherwise we would loop forever requeuing clean inodes as
   * we cannot tell apart a successful delwri flush and a clean inode from the
   * return value of xfs_iflush().
   *
   * Note that because the inode is flushed delayed write by background
   * writeback, 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 out delayed write inodes first before
   * trying to reclaim them to minimise the amount of time spent waiting. For
   * background relaim, we just requeue the inode for the next pass.
   *

   * Hence the order of actions after gaining the locks should be:
   *	bad		=> reclaim
   *	shutdown	=> unpin and reclaim

   *	pinned, delwri	=> requeue
   *	pinned, sync	=> unpin

   *	stale		=> reclaim
   *	clean		=> reclaim

   *	dirty, delwri	=> flush and requeue
   *	dirty, sync	=> flush, wait and reclaim

   */

  STATIC int

  xfs_reclaim_inode(

  	struct xfs_inode	*ip,
  	struct xfs_perag	*pag,

  	int			sync_mode)

  {

  	int	error;

  restart:
  	error = 0;

  	xfs_ilock(ip, XFS_ILOCK_EXCL);

  	if (!xfs_iflock_nowait(ip)) {
  		if (!(sync_mode & SYNC_WAIT))
  			goto out;

  
  		/*
  		 * If we only have a single dirty inode in a cluster there is
  		 * a fair chance that the AIL push may have pushed it into
  		 * the buffer, but xfsbufd won't touch it until 30 seconds
  		 * from now, and thus we will lock up here.
  		 *
  		 * Promote the inode buffer to the front of the delwri list
  		 * and wake up xfsbufd now.
  		 */
  		xfs_promote_inode(ip);

  		xfs_iflock(ip);
  	}

  	if (is_bad_inode(VFS_I(ip)))
  		goto reclaim;
  	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
  		xfs_iunpin_wait(ip);
  		goto reclaim;
  	}

  	if (xfs_ipincount(ip)) {
  		if (!(sync_mode & SYNC_WAIT)) {
  			xfs_ifunlock(ip);
  			goto out;
  		}

  		xfs_iunpin_wait(ip);

  	}

  	if (xfs_iflags_test(ip, XFS_ISTALE))
  		goto reclaim;
  	if (xfs_inode_clean(ip))
  		goto reclaim;

  	/*
  	 * Now we have an inode that needs flushing.
  	 *
  	 * We do a nonblocking flush here even if we are doing a SYNC_WAIT
  	 * reclaim as we can deadlock with inode cluster removal.
  	 * 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_itobp() to get the cluster buffer will 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 on a SYNC_WAIT flush,
  	 * 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, SYNC_TRYLOCK | sync_mode);

  	if (sync_mode & SYNC_WAIT) {

  		if (error == EAGAIN) {
  			xfs_iunlock(ip, XFS_ILOCK_EXCL);
  			/* backoff longer than in xfs_ifree_cluster */
  			delay(2);
  			goto restart;
  		}

  		xfs_iflock(ip);
  		goto reclaim;

  	}

  	/*
  	 * When we have to flush an inode but don't have SYNC_WAIT set, we
  	 * flush the inode out using a delwri buffer and wait for the next
  	 * call into reclaim to find it in a clean state instead of waiting for
  	 * it now. We also don't return errors here - if the error is transient
  	 * then the next reclaim pass will flush the inode, and if the error

  	 * is permanent then the next sync reclaim will reclaim the inode and

  	 * pass on the error.
  	 */

  	if (error && error != EAGAIN && !XFS_FORCED_SHUTDOWN(ip->i_mount)) {

  		xfs_warn(ip->i_mount,

  			"inode 0x%llx background reclaim flush failed with %d",
  			(long long)ip->i_ino, error);
  	}
  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 xfssyncd 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;

  reclaim:
  	xfs_ifunlock(ip);

  	xfs_iunlock(ip, XFS_ILOCK_EXCL);

  
  	XFS_STATS_INC(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, ip->i_ino)))
  		ASSERT(0);

  	__xfs_inode_clear_reclaim(pag, ip);

  	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.  We get
  	 * both the ilock and the iolock because the code may need to drop the
  	 * ilock one but will still hold the iolock.
  	 */
  	xfs_ilock(ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
  	xfs_qm_dqdetach(ip);
  	xfs_iunlock(ip, XFS_ILOCK_EXCL | XFS_IOLOCK_EXCL);
  
  	xfs_inode_free(ip);

  	return error;

  }

  /*
   * 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.
   */
  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 XFS_ERROR(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.

   */

  void
  xfs_reclaim_inodes_nr(
  	struct xfs_mount	*mp,
  	int			nr_to_scan)

  {

  	/* kick background reclaimer and push the AIL */
  	xfs_syncd_queue_reclaim(mp);
  	xfs_ail_push_all(mp->m_ail);

  	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;
  }