/*
   * Copyright (c) 2006-2007 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_bmap_btree.h"
  #include "xfs_inum.h"

  #include "xfs_dinode.h"
  #include "xfs_inode.h"
  #include "xfs_ag.h"

  #include "xfs_log.h"
  #include "xfs_trans.h"
  #include "xfs_sb.h"
  #include "xfs_mount.h"
  #include "xfs_bmap.h"
  #include "xfs_alloc.h"
  #include "xfs_utils.h"
  #include "xfs_mru_cache.h"
  #include "xfs_filestream.h"

  #include "xfs_trace.h"

  
  #ifdef XFS_FILESTREAMS_TRACE
  
  ktrace_t *xfs_filestreams_trace_buf;
  
  STATIC void
  xfs_filestreams_trace(
  	xfs_mount_t	*mp,	/* mount point */
  	int		type,	/* type of trace */
  	const char	*func,	/* source function */
  	int		line,	/* source line number */
  	__psunsigned_t	arg0,
  	__psunsigned_t	arg1,
  	__psunsigned_t	arg2,
  	__psunsigned_t	arg3,
  	__psunsigned_t	arg4,
  	__psunsigned_t	arg5)
  {
  	ktrace_enter(xfs_filestreams_trace_buf,
  		(void *)(__psint_t)(type | (line << 16)),
  		(void *)func,
  		(void *)(__psunsigned_t)current_pid(),
  		(void *)mp,
  		(void *)(__psunsigned_t)arg0,
  		(void *)(__psunsigned_t)arg1,
  		(void *)(__psunsigned_t)arg2,
  		(void *)(__psunsigned_t)arg3,
  		(void *)(__psunsigned_t)arg4,
  		(void *)(__psunsigned_t)arg5,
  		NULL, NULL, NULL, NULL, NULL, NULL);
  }
  
  #define TRACE0(mp,t)			TRACE6(mp,t,0,0,0,0,0,0)
  #define TRACE1(mp,t,a0)			TRACE6(mp,t,a0,0,0,0,0,0)
  #define TRACE2(mp,t,a0,a1)		TRACE6(mp,t,a0,a1,0,0,0,0)
  #define TRACE3(mp,t,a0,a1,a2)		TRACE6(mp,t,a0,a1,a2,0,0,0)
  #define TRACE4(mp,t,a0,a1,a2,a3)	TRACE6(mp,t,a0,a1,a2,a3,0,0)
  #define TRACE5(mp,t,a0,a1,a2,a3,a4)	TRACE6(mp,t,a0,a1,a2,a3,a4,0)
  #define TRACE6(mp,t,a0,a1,a2,a3,a4,a5) \

  	xfs_filestreams_trace(mp, t, __func__, __LINE__, \

  				(__psunsigned_t)a0, (__psunsigned_t)a1, \
  				(__psunsigned_t)a2, (__psunsigned_t)a3, \
  				(__psunsigned_t)a4, (__psunsigned_t)a5)
  
  #define TRACE_AG_SCAN(mp, ag, ag2) \
  		TRACE2(mp, XFS_FSTRM_KTRACE_AGSCAN, ag, ag2);
  #define TRACE_AG_PICK1(mp, max_ag, maxfree) \
  		TRACE2(mp, XFS_FSTRM_KTRACE_AGPICK1, max_ag, maxfree);
  #define TRACE_AG_PICK2(mp, ag, ag2, cnt, free, scan, flag) \
  		TRACE6(mp, XFS_FSTRM_KTRACE_AGPICK2, ag, ag2, \
  			 cnt, free, scan, flag)
  #define TRACE_UPDATE(mp, ip, ag, cnt, ag2, cnt2) \
  		TRACE5(mp, XFS_FSTRM_KTRACE_UPDATE, ip, ag, cnt, ag2, cnt2)
  #define TRACE_FREE(mp, ip, pip, ag, cnt) \
  		TRACE4(mp, XFS_FSTRM_KTRACE_FREE, ip, pip, ag, cnt)
  #define TRACE_LOOKUP(mp, ip, pip, ag, cnt) \
  		TRACE4(mp, XFS_FSTRM_KTRACE_ITEM_LOOKUP, ip, pip, ag, cnt)
  #define TRACE_ASSOCIATE(mp, ip, pip, ag, cnt) \
  		TRACE4(mp, XFS_FSTRM_KTRACE_ASSOCIATE, ip, pip, ag, cnt)
  #define TRACE_MOVEAG(mp, ip, pip, oag, ocnt, nag, ncnt) \
  		TRACE6(mp, XFS_FSTRM_KTRACE_MOVEAG, ip, pip, oag, ocnt, nag, ncnt)
  #define TRACE_ORPHAN(mp, ip, ag) \
  		TRACE2(mp, XFS_FSTRM_KTRACE_ORPHAN, ip, ag);
  
  
  #else
  #define TRACE_AG_SCAN(mp, ag, ag2)
  #define TRACE_AG_PICK1(mp, max_ag, maxfree)
  #define TRACE_AG_PICK2(mp, ag, ag2, cnt, free, scan, flag)
  #define TRACE_UPDATE(mp, ip, ag, cnt, ag2, cnt2)
  #define TRACE_FREE(mp, ip, pip, ag, cnt)
  #define TRACE_LOOKUP(mp, ip, pip, ag, cnt)
  #define TRACE_ASSOCIATE(mp, ip, pip, ag, cnt)
  #define TRACE_MOVEAG(mp, ip, pip, oag, ocnt, nag, ncnt)
  #define TRACE_ORPHAN(mp, ip, ag)
  #endif
  
  static kmem_zone_t *item_zone;
  
  /*
   * Structure for associating a file or a directory with an allocation group.
   * The parent directory pointer is only needed for files, but since there will
   * generally be vastly more files than directories in the cache, using the same
   * data structure simplifies the code with very little memory overhead.
   */
  typedef struct fstrm_item
  {
  	xfs_agnumber_t	ag;	/* AG currently in use for the file/directory. */
  	xfs_inode_t	*ip;	/* inode self-pointer. */
  	xfs_inode_t	*pip;	/* Parent directory inode pointer. */
  } fstrm_item_t;

  /*
   * Allocation group filestream associations are tracked with per-ag atomic
   * counters.  These counters allow _xfs_filestream_pick_ag() to tell whether a
   * particular AG already has active filestreams associated with it. The mount
   * point's m_peraglock is used to protect these counters from per-ag array
   * re-allocation during a growfs operation.  When xfs_growfs_data_private() is
   * about to reallocate the array, it calls xfs_filestream_flush() with the
   * m_peraglock held in write mode.
   *
   * Since xfs_mru_cache_flush() guarantees that all the free functions for all
   * the cache elements have finished executing before it returns, it's safe for
   * the free functions to use the atomic counters without m_peraglock protection.
   * This allows the implementation of xfs_fstrm_free_func() to be agnostic about
   * whether it was called with the m_peraglock held in read mode, write mode or
   * not held at all.  The race condition this addresses is the following:
   *
   *  - The work queue scheduler fires and pulls a filestream directory cache
   *    element off the LRU end of the cache for deletion, then gets pre-empted.
   *  - A growfs operation grabs the m_peraglock in write mode, flushes all the
   *    remaining items from the cache and reallocates the mount point's per-ag
   *    array, resetting all the counters to zero.
   *  - The work queue thread resumes and calls the free function for the element
   *    it started cleaning up earlier.  In the process it decrements the
   *    filestreams counter for an AG that now has no references.
   *
   * With a shrinkfs feature, the above scenario could panic the system.
   *
   * All other uses of the following macros should be protected by either the
   * m_peraglock held in read mode, or the cache's internal locking exposed by the
   * interval between a call to xfs_mru_cache_lookup() and a call to
   * xfs_mru_cache_done().  In addition, the m_peraglock must be held in read mode
   * when new elements are added to the cache.
   *
   * Combined, these locking rules ensure that no associations will ever exist in
   * the cache that reference per-ag array elements that have since been
   * reallocated.
   */
  static int
  xfs_filestream_peek_ag(
  	xfs_mount_t	*mp,
  	xfs_agnumber_t	agno)
  {
  	struct xfs_perag *pag;
  	int		ret;
  
  	pag = xfs_perag_get(mp, agno);
  	ret = atomic_read(&pag->pagf_fstrms);
  	xfs_perag_put(pag);
  	return ret;
  }
  
  static int
  xfs_filestream_get_ag(
  	xfs_mount_t	*mp,
  	xfs_agnumber_t	agno)
  {
  	struct xfs_perag *pag;
  	int		ret;
  
  	pag = xfs_perag_get(mp, agno);
  	ret = atomic_inc_return(&pag->pagf_fstrms);
  	xfs_perag_put(pag);
  	return ret;
  }
  
  static void
  xfs_filestream_put_ag(
  	xfs_mount_t	*mp,
  	xfs_agnumber_t	agno)
  {
  	struct xfs_perag *pag;
  
  	pag = xfs_perag_get(mp, agno);
  	atomic_dec(&pag->pagf_fstrms);
  	xfs_perag_put(pag);
  }

  
  /*
   * Scan the AGs starting at startag looking for an AG that isn't in use and has
   * at least minlen blocks free.
   */
  static int
  _xfs_filestream_pick_ag(
  	xfs_mount_t	*mp,
  	xfs_agnumber_t	startag,
  	xfs_agnumber_t	*agp,
  	int		flags,
  	xfs_extlen_t	minlen)
  {

  	int		streams, max_streams;

  	int		err, trylock, nscan;

  	xfs_extlen_t	longest, free, minfree, maxfree = 0;

  	xfs_agnumber_t	ag, max_ag = NULLAGNUMBER;
  	struct xfs_perag *pag;
  
  	/* 2% of an AG's blocks must be free for it to be chosen. */
  	minfree = mp->m_sb.sb_agblocks / 50;
  
  	ag = startag;
  	*agp = NULLAGNUMBER;
  
  	/* For the first pass, don't sleep trying to init the per-AG. */
  	trylock = XFS_ALLOC_FLAG_TRYLOCK;
  
  	for (nscan = 0; 1; nscan++) {

  		pag = xfs_perag_get(mp, ag);
  		TRACE_AG_SCAN(mp, ag, atomic_read(&pag->pagf_fstrms));

  
  		if (!pag->pagf_init) {
  			err = xfs_alloc_pagf_init(mp, NULL, ag, trylock);

  			if (err && !trylock) {
  				xfs_perag_put(pag);

  				return err;

  			}

  		}
  
  		/* Might fail sometimes during the 1st pass with trylock set. */
  		if (!pag->pagf_init)
  			goto next_ag;
  
  		/* Keep track of the AG with the most free blocks. */
  		if (pag->pagf_freeblks > maxfree) {
  			maxfree = pag->pagf_freeblks;

  			max_streams = atomic_read(&pag->pagf_fstrms);

  			max_ag = ag;
  		}
  
  		/*
  		 * The AG reference count does two things: it enforces mutual
  		 * exclusion when examining the suitability of an AG in this
  		 * loop, and it guards against two filestreams being established
  		 * in the same AG as each other.
  		 */
  		if (xfs_filestream_get_ag(mp, ag) > 1) {
  			xfs_filestream_put_ag(mp, ag);
  			goto next_ag;
  		}

  		longest = xfs_alloc_longest_free_extent(mp, pag);

  		if (((minlen && longest >= minlen) ||
  		     (!minlen && pag->pagf_freeblks >= minfree)) &&
  		    (!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) ||
  		     (flags & XFS_PICK_LOWSPACE))) {
  
  			/* Break out, retaining the reference on the AG. */
  			free = pag->pagf_freeblks;

  			streams = atomic_read(&pag->pagf_fstrms);
  			xfs_perag_put(pag);

  			*agp = ag;
  			break;
  		}
  
  		/* Drop the reference on this AG, it's not usable. */
  		xfs_filestream_put_ag(mp, ag);
  next_ag:

  		xfs_perag_put(pag);

  		/* Move to the next AG, wrapping to AG 0 if necessary. */
  		if (++ag >= mp->m_sb.sb_agcount)
  			ag = 0;
  
  		/* If a full pass of the AGs hasn't been done yet, continue. */
  		if (ag != startag)
  			continue;
  
  		/* Allow sleeping in xfs_alloc_pagf_init() on the 2nd pass. */
  		if (trylock != 0) {
  			trylock = 0;
  			continue;
  		}
  
  		/* Finally, if lowspace wasn't set, set it for the 3rd pass. */
  		if (!(flags & XFS_PICK_LOWSPACE)) {
  			flags |= XFS_PICK_LOWSPACE;
  			continue;
  		}
  
  		/*
  		 * Take the AG with the most free space, regardless of whether
  		 * it's already in use by another filestream.
  		 */
  		if (max_ag != NULLAGNUMBER) {
  			xfs_filestream_get_ag(mp, max_ag);
  			TRACE_AG_PICK1(mp, max_ag, maxfree);

  			streams = max_streams;

  			free = maxfree;
  			*agp = max_ag;
  			break;
  		}
  
  		/* take AG 0 if none matched */
  		TRACE_AG_PICK1(mp, max_ag, maxfree);
  		*agp = 0;
  		return 0;
  	}

  	TRACE_AG_PICK2(mp, startag, *agp, streams, free, nscan, flags);

  
  	return 0;
  }
  
  /*
   * Set the allocation group number for a file or a directory, updating inode

   * references and per-AG references as appropriate.

   */
  static int
  _xfs_filestream_update_ag(
  	xfs_inode_t	*ip,
  	xfs_inode_t	*pip,
  	xfs_agnumber_t	ag)
  {
  	int		err = 0;
  	xfs_mount_t	*mp;
  	xfs_mru_cache_t	*cache;
  	fstrm_item_t	*item;
  	xfs_agnumber_t	old_ag;
  	xfs_inode_t	*old_pip;
  
  	/*
  	 * Either ip is a regular file and pip is a directory, or ip is a
  	 * directory and pip is NULL.
  	 */

  	ASSERT(ip && ((S_ISREG(ip->i_d.di_mode) && pip &&

  	               S_ISDIR(pip->i_d.di_mode)) ||
  	              (S_ISDIR(ip->i_d.di_mode) && !pip)));

  
  	mp = ip->i_mount;
  	cache = mp->m_filestream;
  
  	item = xfs_mru_cache_lookup(cache, ip->i_ino);
  	if (item) {
  		ASSERT(item->ip == ip);
  		old_ag = item->ag;
  		item->ag = ag;
  		old_pip = item->pip;
  		item->pip = pip;
  		xfs_mru_cache_done(cache);
  
  		/*
  		 * If the AG has changed, drop the old ref and take a new one,
  		 * effectively transferring the reference from old to new AG.
  		 */
  		if (ag != old_ag) {
  			xfs_filestream_put_ag(mp, old_ag);
  			xfs_filestream_get_ag(mp, ag);
  		}
  
  		/*
  		 * If ip is a file and its pip has changed, drop the old ref and
  		 * take a new one.
  		 */
  		if (pip && pip != old_pip) {
  			IRELE(old_pip);
  			IHOLD(pip);
  		}
  
  		TRACE_UPDATE(mp, ip, old_ag, xfs_filestream_peek_ag(mp, old_ag),
  				ag, xfs_filestream_peek_ag(mp, ag));
  		return 0;
  	}
  
  	item = kmem_zone_zalloc(item_zone, KM_MAYFAIL);
  	if (!item)
  		return ENOMEM;
  
  	item->ag = ag;
  	item->ip = ip;
  	item->pip = pip;
  
  	err = xfs_mru_cache_insert(cache, ip->i_ino, item);
  	if (err) {
  		kmem_zone_free(item_zone, item);
  		return err;
  	}
  
  	/* Take a reference on the AG. */
  	xfs_filestream_get_ag(mp, ag);
  
  	/*
  	 * Take a reference on the inode itself regardless of whether it's a
  	 * regular file or a directory.
  	 */
  	IHOLD(ip);
  
  	/*
  	 * In the case of a regular file, take a reference on the parent inode
  	 * as well to ensure it remains in-core.
  	 */
  	if (pip)
  		IHOLD(pip);
  
  	TRACE_UPDATE(mp, ip, ag, xfs_filestream_peek_ag(mp, ag),
  			ag, xfs_filestream_peek_ag(mp, ag));
  
  	return 0;
  }
  
  /* xfs_fstrm_free_func(): callback for freeing cached stream items. */

  STATIC void

  xfs_fstrm_free_func(

  	unsigned long	ino,
  	void		*data)

  {

  	fstrm_item_t	*item  = (fstrm_item_t *)data;

  	xfs_inode_t	*ip = item->ip;

  
  	ASSERT(ip->i_ino == ino);
  
  	xfs_iflags_clear(ip, XFS_IFILESTREAM);
  
  	/* Drop the reference taken on the AG when the item was added. */

  	xfs_filestream_put_ag(ip->i_mount, item->ag);

  	TRACE_FREE(ip->i_mount, ip, item->pip, item->ag,
  		xfs_filestream_peek_ag(ip->i_mount, item->ag));
  
  	/*
  	 * _xfs_filestream_update_ag() always takes a reference on the inode
  	 * itself, whether it's a file or a directory.  Release it here.
  	 * This can result in the inode being freed and so we must
  	 * not hold any inode locks when freeing filesstreams objects
  	 * otherwise we can deadlock here.
  	 */
  	IRELE(ip);
  
  	/*
  	 * In the case of a regular file, _xfs_filestream_update_ag() also
  	 * takes a ref on the parent inode to keep it in-core.  Release that
  	 * too.
  	 */
  	if (item->pip)
  		IRELE(item->pip);
  
  	/* Finally, free the memory allocated for the item. */
  	kmem_zone_free(item_zone, item);
  }
  
  /*
   * xfs_filestream_init() is called at xfs initialisation time to set up the
   * memory zone that will be used for filestream data structure allocation.
   */
  int
  xfs_filestream_init(void)
  {
  	item_zone = kmem_zone_init(sizeof(fstrm_item_t), "fstrm_item");

  	if (!item_zone)
  		return -ENOMEM;

  	return 0;

  }
  
  /*
   * xfs_filestream_uninit() is called at xfs termination time to destroy the
   * memory zone that was used for filestream data structure allocation.
   */
  void
  xfs_filestream_uninit(void)
  {

  	kmem_zone_destroy(item_zone);
  }
  
  /*
   * xfs_filestream_mount() is called when a file system is mounted with the
   * filestream option.  It is responsible for allocating the data structures
   * needed to track the new file system's file streams.
   */
  int
  xfs_filestream_mount(
  	xfs_mount_t	*mp)
  {
  	int		err;
  	unsigned int	lifetime, grp_count;
  
  	/*
  	 * The filestream timer tunable is currently fixed within the range of
  	 * one second to four minutes, with five seconds being the default.  The
  	 * group count is somewhat arbitrary, but it'd be nice to adhere to the
  	 * timer tunable to within about 10 percent.  This requires at least 10
  	 * groups.
  	 */
  	lifetime  = xfs_fstrm_centisecs * 10;
  	grp_count = 10;
  
  	err = xfs_mru_cache_create(&mp->m_filestream, lifetime, grp_count,

  	                     xfs_fstrm_free_func);

  
  	return err;
  }
  
  /*
   * xfs_filestream_unmount() is called when a file system that was mounted with
   * the filestream option is unmounted.  It drains the data structures created
   * to track the file system's file streams and frees all the memory that was
   * allocated.
   */
  void
  xfs_filestream_unmount(
  	xfs_mount_t	*mp)
  {
  	xfs_mru_cache_destroy(mp->m_filestream);
  }
  
  /*

   * Return the AG of the filestream the file or directory belongs to, or
   * NULLAGNUMBER otherwise.
   */
  xfs_agnumber_t
  xfs_filestream_lookup_ag(
  	xfs_inode_t	*ip)
  {
  	xfs_mru_cache_t	*cache;
  	fstrm_item_t	*item;
  	xfs_agnumber_t	ag;
  	int		ref;

  	if (!S_ISREG(ip->i_d.di_mode) && !S_ISDIR(ip->i_d.di_mode)) {

  		ASSERT(0);
  		return NULLAGNUMBER;
  	}
  
  	cache = ip->i_mount->m_filestream;
  	item = xfs_mru_cache_lookup(cache, ip->i_ino);
  	if (!item) {
  		TRACE_LOOKUP(ip->i_mount, ip, NULL, NULLAGNUMBER, 0);
  		return NULLAGNUMBER;
  	}
  
  	ASSERT(ip == item->ip);
  	ag = item->ag;
  	ref = xfs_filestream_peek_ag(ip->i_mount, ag);
  	xfs_mru_cache_done(cache);
  
  	TRACE_LOOKUP(ip->i_mount, ip, item->pip, ag, ref);
  	return ag;
  }
  
  /*
   * xfs_filestream_associate() should only be called to associate a regular file
   * with its parent directory.  Calling it with a child directory isn't
   * appropriate because filestreams don't apply to entire directory hierarchies.
   * Creating a file in a child directory of an existing filestream directory
   * starts a new filestream with its own allocation group association.
   *
   * Returns < 0 on error, 0 if successful association occurred, > 0 if
   * we failed to get an association because of locking issues.
   */
  int
  xfs_filestream_associate(
  	xfs_inode_t	*pip,
  	xfs_inode_t	*ip)
  {
  	xfs_mount_t	*mp;
  	xfs_mru_cache_t	*cache;
  	fstrm_item_t	*item;
  	xfs_agnumber_t	ag, rotorstep, startag;
  	int		err = 0;

  	ASSERT(S_ISDIR(pip->i_d.di_mode));
  	ASSERT(S_ISREG(ip->i_d.di_mode));
  	if (!S_ISDIR(pip->i_d.di_mode) || !S_ISREG(ip->i_d.di_mode))

  		return -EINVAL;
  
  	mp = pip->i_mount;
  	cache = mp->m_filestream;

  
  	/*
  	 * We have a problem, Houston.
  	 *
  	 * Taking the iolock here violates inode locking order - we already
  	 * hold the ilock. Hence if we block getting this lock we may never
  	 * wake. Unfortunately, that means if we can't get the lock, we're
  	 * screwed in terms of getting a stream association - we can't spin
  	 * waiting for the lock because someone else is waiting on the lock we
  	 * hold and we cannot drop that as we are in a transaction here.
  	 *

  	 * Lucky for us, this inversion is not a problem because it's a
  	 * directory inode that we are trying to lock here.

  	 *
  	 * So, if we can't get the iolock without sleeping then just give up
  	 */

  	if (!xfs_ilock_nowait(pip, XFS_IOLOCK_EXCL))

  		return 1;

  
  	/* If the parent directory is already in the cache, use its AG. */
  	item = xfs_mru_cache_lookup(cache, pip->i_ino);
  	if (item) {
  		ASSERT(item->ip == pip);
  		ag = item->ag;
  		xfs_mru_cache_done(cache);
  
  		TRACE_LOOKUP(mp, pip, pip, ag, xfs_filestream_peek_ag(mp, ag));
  		err = _xfs_filestream_update_ag(ip, pip, ag);
  
  		goto exit;
  	}
  
  	/*
  	 * Set the starting AG using the rotor for inode32, otherwise
  	 * use the directory inode's AG.
  	 */
  	if (mp->m_flags & XFS_MOUNT_32BITINODES) {
  		rotorstep = xfs_rotorstep;
  		startag = (mp->m_agfrotor / rotorstep) % mp->m_sb.sb_agcount;
  		mp->m_agfrotor = (mp->m_agfrotor + 1) %
  		                 (mp->m_sb.sb_agcount * rotorstep);
  	} else
  		startag = XFS_INO_TO_AGNO(mp, pip->i_ino);
  
  	/* Pick a new AG for the parent inode starting at startag. */
  	err = _xfs_filestream_pick_ag(mp, startag, &ag, 0, 0);
  	if (err || ag == NULLAGNUMBER)
  		goto exit_did_pick;
  
  	/* Associate the parent inode with the AG. */
  	err = _xfs_filestream_update_ag(pip, NULL, ag);
  	if (err)
  		goto exit_did_pick;
  
  	/* Associate the file inode with the AG. */
  	err = _xfs_filestream_update_ag(ip, pip, ag);
  	if (err)
  		goto exit_did_pick;
  
  	TRACE_ASSOCIATE(mp, ip, pip, ag, xfs_filestream_peek_ag(mp, ag));
  
  exit_did_pick:
  	/*
  	 * If _xfs_filestream_pick_ag() returned a valid AG, remove the
  	 * reference it took on it, since the file and directory will have taken
  	 * their own now if they were successfully cached.
  	 */
  	if (ag != NULLAGNUMBER)
  		xfs_filestream_put_ag(mp, ag);
  
  exit:
  	xfs_iunlock(pip, XFS_IOLOCK_EXCL);

  	return -err;
  }
  
  /*
   * Pick a new allocation group for the current file and its file stream.  This
   * function is called by xfs_bmap_filestreams() with the mount point's per-ag
   * lock held.
   */
  int
  xfs_filestream_new_ag(
  	xfs_bmalloca_t	*ap,
  	xfs_agnumber_t	*agp)
  {
  	int		flags, err;
  	xfs_inode_t	*ip, *pip = NULL;
  	xfs_mount_t	*mp;
  	xfs_mru_cache_t	*cache;
  	xfs_extlen_t	minlen;
  	fstrm_item_t	*dir, *file;
  	xfs_agnumber_t	ag = NULLAGNUMBER;
  
  	ip = ap->ip;
  	mp = ip->i_mount;
  	cache = mp->m_filestream;

  	minlen = ap->length;

  	*agp = NULLAGNUMBER;
  
  	/*
  	 * Look for the file in the cache, removing it if it's found.  Doing
  	 * this allows it to be held across the dir lookup that follows.
  	 */
  	file = xfs_mru_cache_remove(cache, ip->i_ino);
  	if (file) {
  		ASSERT(ip == file->ip);
  
  		/* Save the file's parent inode and old AG number for later. */
  		pip = file->pip;
  		ag = file->ag;
  
  		/* Look for the file's directory in the cache. */
  		dir = xfs_mru_cache_lookup(cache, pip->i_ino);
  		if (dir) {
  			ASSERT(pip == dir->ip);
  
  			/*
  			 * If the directory has already moved on to a new AG,
  			 * use that AG as the new AG for the file. Don't
  			 * forget to twiddle the AG refcounts to match the
  			 * movement.
  			 */
  			if (dir->ag != file->ag) {
  				xfs_filestream_put_ag(mp, file->ag);
  				xfs_filestream_get_ag(mp, dir->ag);
  				*agp = file->ag = dir->ag;
  			}
  
  			xfs_mru_cache_done(cache);
  		}
  
  		/*
  		 * Put the file back in the cache.  If this fails, the free
  		 * function needs to be called to tidy up in the same way as if
  		 * the item had simply expired from the cache.
  		 */
  		err = xfs_mru_cache_insert(cache, ip->i_ino, file);
  		if (err) {
  			xfs_fstrm_free_func(ip->i_ino, file);
  			return err;
  		}
  
  		/*
  		 * If the file's AG was moved to the directory's new AG, there's
  		 * nothing more to be done.
  		 */
  		if (*agp != NULLAGNUMBER) {
  			TRACE_MOVEAG(mp, ip, pip,
  					ag, xfs_filestream_peek_ag(mp, ag),
  					*agp, xfs_filestream_peek_ag(mp, *agp));
  			return 0;
  		}
  	}
  
  	/*
  	 * If the file's parent directory is known, take its iolock in exclusive
  	 * mode to prevent two sibling files from racing each other to migrate
  	 * themselves and their parent to different AGs.

  	 *
  	 * Note that we lock the parent directory iolock inside the child
  	 * iolock here.  That's fine as we never hold both parent and child
  	 * iolock in any other place.  This is different from the ilock,
  	 * which requires locking of the child after the parent for namespace
  	 * operations.

  	 */
  	if (pip)

  		xfs_ilock(pip, XFS_IOLOCK_EXCL | XFS_IOLOCK_PARENT);

  
  	/*
  	 * A new AG needs to be found for the file.  If the file's parent
  	 * directory is also known, it will be moved to the new AG as well to
  	 * ensure that files created inside it in future use the new AG.
  	 */
  	ag = (ag == NULLAGNUMBER) ? 0 : (ag + 1) % mp->m_sb.sb_agcount;
  	flags = (ap->userdata ? XFS_PICK_USERDATA : 0) |

  	        (ap->flist->xbf_low ? XFS_PICK_LOWSPACE : 0);

  
  	err = _xfs_filestream_pick_ag(mp, ag, agp, flags, minlen);
  	if (err || *agp == NULLAGNUMBER)
  		goto exit;
  
  	/*
  	 * If the file wasn't found in the file cache, then its parent directory
  	 * inode isn't known.  For this to have happened, the file must either
  	 * be pre-existing, or it was created long enough ago that its cache
  	 * entry has expired.  This isn't the sort of usage that the filestreams
  	 * allocator is trying to optimise, so there's no point trying to track
  	 * its new AG somehow in the filestream data structures.
  	 */
  	if (!pip) {
  		TRACE_ORPHAN(mp, ip, *agp);
  		goto exit;
  	}
  
  	/* Associate the parent inode with the AG. */
  	err = _xfs_filestream_update_ag(pip, NULL, *agp);
  	if (err)
  		goto exit;
  
  	/* Associate the file inode with the AG. */
  	err = _xfs_filestream_update_ag(ip, pip, *agp);
  	if (err)
  		goto exit;
  
  	TRACE_MOVEAG(mp, ip, pip, NULLAGNUMBER, 0,
  			*agp, xfs_filestream_peek_ag(mp, *agp));
  
  exit:
  	/*
  	 * If _xfs_filestream_pick_ag() returned a valid AG, remove the
  	 * reference it took on it, since the file and directory will have taken
  	 * their own now if they were successfully cached.
  	 */
  	if (*agp != NULLAGNUMBER)
  		xfs_filestream_put_ag(mp, *agp);
  	else
  		*agp = 0;
  
  	if (pip)
  		xfs_iunlock(pip, XFS_IOLOCK_EXCL);
  
  	return err;
  }
  
  /*
   * Remove an association between an inode and a filestream object.
   * Typically this is done on last close of an unlinked file.
   */
  void
  xfs_filestream_deassociate(
  	xfs_inode_t	*ip)
  {
  	xfs_mru_cache_t	*cache = ip->i_mount->m_filestream;
  
  	xfs_mru_cache_delete(cache, ip->i_ino);
  }