fs/xfs/xfs_filestream.c - kernel/msm-5.4 - Gitiles

 /*
  * Copyright (c) 2006-2007 Silicon Graphics, Inc.
  * Copyright (c) 2014 Christoph Hellwig.
  * 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_format.h"
 #include "xfs_log_format.h"
 #include "xfs_trans_resv.h"
 #include "xfs_ag.h"
 #include "xfs_sb.h"
 #include "xfs_mount.h"
 #include "xfs_inum.h"
 #include "xfs_inode.h"
 #include "xfs_bmap.h"
 #include "xfs_bmap_util.h"
 #include "xfs_alloc.h"
 #include "xfs_mru_cache.h"
 #include "xfs_dinode.h"
 #include "xfs_filestream.h"
 #include "xfs_trace.h"

 #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_FREE(mp, ip, pip, ag, cnt)
 #define TRACE_LOOKUP(mp, ip, pip, ag, cnt)

 static kmem_zone_t *item_zone;

 struct xfs_fstrm_item {
 	struct xfs_mru_cache_elem	mru;
 	struct xfs_inode		*ip;
 	xfs_agnumber_t			ag; /* AG in use for this directory */
 };

 enum xfs_fstrm_alloc {
 	XFS_PICK_USERDATA = 1,
 	XFS_PICK_LOWSPACE = 2,
 };

 /*
  * 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);
 }

 static void
 xfs_fstrm_free_func(
 	struct xfs_mru_cache_elem *mru)
 {
 	struct xfs_fstrm_item	*item =
 		container_of(mru, struct xfs_fstrm_item, mru);

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

 	TRACE_FREE(mp, ip, NULL, item->ag,
 		   xfs_filestream_peek_ag(mp, item->ag));

 	kmem_zone_free(item_zone, item);
 }

 /*
  * 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(
 	struct xfs_inode	*ip,
 	xfs_agnumber_t		startag,
 	xfs_agnumber_t		*agp,
 	int			flags,
 	xfs_extlen_t		minlen)
 {
 	struct xfs_mount	*mp = ip->i_mount;
 	struct xfs_fstrm_item	*item;
 	struct xfs_perag	*pag;
 	xfs_extlen_t		longest, free, minfree, maxfree = 0;
 	xfs_agnumber_t		ag, max_ag = NULLAGNUMBER;
 	int			streams, max_streams;
 	int			err, trylock, nscan;

 	ASSERT(S_ISDIR(ip->i_d.di_mode));

 	/* 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);

 	if (*agp == NULLAGNUMBER)
 		return 0;

 	err = ENOMEM;
 	item = kmem_zone_zalloc(item_zone, KM_MAYFAIL);
 	if (!item)
 		goto out_put_ag;

 	item->ag = *agp;
 	item->ip = ip;

 	err = xfs_mru_cache_insert(mp->m_filestream, ip->i_ino, &item->mru);
 	if (err) {
 		if (err == EEXIST)
 			err = 0;
 		goto out_free_item;
 	}

 	return 0;

 out_free_item:
 	kmem_zone_free(item_zone, item);
 out_put_ag:
 	xfs_filestream_put_ag(mp, *agp);
 	return err;
 }

 static struct xfs_inode *
 xfs_filestream_get_parent(
 	struct xfs_inode	*ip)
 {
 	struct inode		*inode = VFS_I(ip), *dir = NULL;
 	struct dentry		*dentry, *parent;

 	dentry = d_find_alias(inode);
 	if (!dentry)
 		goto out;

 	parent = dget_parent(dentry);
 	if (!parent)
 		goto out_dput;

 	dir = igrab(parent->d_inode);
 	dput(parent);

 out_dput:
 	dput(dentry);
 out:
 	return dir ? XFS_I(dir) : NULL;
 }

 /*
  * Return the AG of the filestream the file or directory belongs to, or
  * NULLAGNUMBER otherwise.
  */
 xfs_agnumber_t
 xfs_filestream_lookup_ag(
 	struct xfs_inode	*ip)
 {
 	struct xfs_mount	*mp = ip->i_mount;
 	struct xfs_fstrm_item	*item;
 	struct xfs_inode	*pip = NULL;
 	xfs_agnumber_t		ag = NULLAGNUMBER;
 	int			ref = 0;
 	struct xfs_mru_cache_elem *mru;

 	ASSERT(S_ISREG(ip->i_d.di_mode));

 	pip = xfs_filestream_get_parent(ip);
 	if (!pip)
 		goto out;

 	mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
 	if (!mru)
 		goto out;

 	item = container_of(mru, struct xfs_fstrm_item, mru);

 	ag = item->ag;
 	xfs_mru_cache_done(mp->m_filestream);

 	ref = xfs_filestream_peek_ag(ip->i_mount, ag);
 out:
 	TRACE_LOOKUP(mp, ip, pip, ag, ref);
 	IRELE(pip);
 	return ag;
 }

 /*
  * Make sure a directory has a filestream associated with it.
  *
  * This is called when creating regular files in an directory that has
  * filestreams enabled, so that a stream is ready by the time we need it
  * in the allocator for the files inside the directory.
  */
 int
 xfs_filestream_associate(
 	struct xfs_inode	*pip)
 {
 	struct xfs_mount	*mp = pip->i_mount;
 	struct xfs_mru_cache_elem *mru;
 	xfs_agnumber_t		startag, ag;

 	ASSERT(S_ISDIR(pip->i_d.di_mode));

 	/*
 	 * If the directory already has a file stream associated we're done.
 	 */
 	mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
 	if (mru) {
 		xfs_mru_cache_done(mp->m_filestream);
 		return 0;
 	}

 	/*
 	 * Set the starting AG using the rotor for inode32, otherwise
 	 * use the directory inode's AG.
 	 */
 	if (mp->m_flags & XFS_MOUNT_32BITINODES) {
 		xfs_agnumber_t	 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);

 	return xfs_filestream_pick_ag(pip, startag, &ag, 0, 0);
 }

 /*
  * Pick a new allocation group for the current file and its file stream.
  *
  * This is called when the allocator can't find a suitable extent in the
  * current AG, and we have to move the stream into a new AG with more space.
  */
 int
 xfs_filestream_new_ag(
 	struct xfs_bmalloca	*ap,
 	xfs_agnumber_t		*agp)
 {
 	struct xfs_inode	*ip = ap->ip, *pip;
 	struct xfs_mount	*mp = ip->i_mount;
 	xfs_extlen_t		minlen = ap->length;
 	xfs_agnumber_t		startag = 0;
 	int			flags, err = 0;
 	struct xfs_mru_cache_elem *mru;

 	*agp = NULLAGNUMBER;

 	pip = xfs_filestream_get_parent(ip);
 	if (!pip)
 		goto exit;

 	mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
 	if (mru) {
 		struct xfs_fstrm_item *item =
 			container_of(mru, struct xfs_fstrm_item, mru);
 		startag = (item->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(pip, startag, agp, flags, minlen);

 	/*
 	 * Only free the item here so we skip over the old AG earlier.
 	 */
 	if (mru)
 		xfs_fstrm_free_func(mru);

 	IRELE(pip);
 exit:
 	if (*agp == NULLAGNUMBER)
 		*agp = 0;
 	return err;
 }

 void
 xfs_filestream_deassociate(
 	struct xfs_inode	*ip)
 {
 	xfs_mru_cache_delete(ip->i_mount->m_filestream, ip->i_ino);
 }

 int
 xfs_filestream_mount(
 	xfs_mount_t	*mp)
 {
 	/*
 	 * 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.
 	 */
 	return xfs_mru_cache_create(&mp->m_filestream, xfs_fstrm_centisecs * 10,
 				    10, xfs_fstrm_free_func);
 }

 void
 xfs_filestream_unmount(
 	xfs_mount_t	*mp)
 {
 	xfs_mru_cache_destroy(mp->m_filestream);
 }


 /* needs to return a positive errno for the init path */
 int
 xfs_filestream_init(void)
 {
 	item_zone = kmem_zone_init(sizeof(struct xfs_fstrm_item), "fstrm_item");
 	if (!item_zone)
 		return -ENOMEM;
 	return 0;
 }

 void
 xfs_filestream_uninit(void)
 {
 	kmem_zone_destroy(item_zone);
 }
	/*
	* Copyright (c) 2006-2007 Silicon Graphics, Inc.
	* Copyright (c) 2014 Christoph Hellwig.
	* 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_format.h"
	#include "xfs_log_format.h"
	#include "xfs_trans_resv.h"
	#include "xfs_ag.h"
	#include "xfs_sb.h"
	#include "xfs_mount.h"
	#include "xfs_inum.h"
	#include "xfs_inode.h"
	#include "xfs_bmap.h"
	#include "xfs_bmap_util.h"
	#include "xfs_alloc.h"
	#include "xfs_mru_cache.h"
	#include "xfs_dinode.h"
	#include "xfs_filestream.h"
	#include "xfs_trace.h"

	#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_FREE(mp, ip, pip, ag, cnt)
	#define TRACE_LOOKUP(mp, ip, pip, ag, cnt)

	static kmem_zone_t *item_zone;

	struct xfs_fstrm_item {
	struct xfs_mru_cache_elem mru;
	struct xfs_inode *ip;
	xfs_agnumber_t ag; /* AG in use for this directory */
	};

	enum xfs_fstrm_alloc {
	XFS_PICK_USERDATA = 1,
	XFS_PICK_LOWSPACE = 2,
	};

	/*
	* 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);
	}

	static void
	xfs_fstrm_free_func(
	struct xfs_mru_cache_elem *mru)
	{
	struct xfs_fstrm_item *item =
	container_of(mru, struct xfs_fstrm_item, mru);

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

	TRACE_FREE(mp, ip, NULL, item->ag,
	xfs_filestream_peek_ag(mp, item->ag));

	kmem_zone_free(item_zone, item);
	}

	/*
	* 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(
	struct xfs_inode *ip,
	xfs_agnumber_t startag,
	xfs_agnumber_t *agp,
	int flags,
	xfs_extlen_t minlen)
	{
	struct xfs_mount *mp = ip->i_mount;
	struct xfs_fstrm_item *item;
	struct xfs_perag *pag;
	xfs_extlen_t longest, free, minfree, maxfree = 0;
	xfs_agnumber_t ag, max_ag = NULLAGNUMBER;
	int streams, max_streams;
	int err, trylock, nscan;

	ASSERT(S_ISDIR(ip->i_d.di_mode));

	/* 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);

	if (*agp == NULLAGNUMBER)
	return 0;

	err = ENOMEM;
	item = kmem_zone_zalloc(item_zone, KM_MAYFAIL);
	if (!item)
	goto out_put_ag;

	item->ag = *agp;
	item->ip = ip;

	err = xfs_mru_cache_insert(mp->m_filestream, ip->i_ino, &item->mru);
	if (err) {
	if (err == EEXIST)
	err = 0;
	goto out_free_item;
	}

	return 0;

	out_free_item:
	kmem_zone_free(item_zone, item);
	out_put_ag:
	xfs_filestream_put_ag(mp, *agp);
	return err;
	}

	static struct xfs_inode *
	xfs_filestream_get_parent(
	struct xfs_inode *ip)
	{
	struct inode inode = VFS_I(ip), dir = NULL;
	struct dentry dentry, parent;

	dentry = d_find_alias(inode);
	if (!dentry)
	goto out;

	parent = dget_parent(dentry);
	if (!parent)
	goto out_dput;

	dir = igrab(parent->d_inode);
	dput(parent);

	out_dput:
	dput(dentry);
	out:
	return dir ? XFS_I(dir) : NULL;
	}

	/*
	* Return the AG of the filestream the file or directory belongs to, or
	* NULLAGNUMBER otherwise.
	*/
	xfs_agnumber_t
	xfs_filestream_lookup_ag(
	struct xfs_inode *ip)
	{
	struct xfs_mount *mp = ip->i_mount;
	struct xfs_fstrm_item *item;
	struct xfs_inode *pip = NULL;
	xfs_agnumber_t ag = NULLAGNUMBER;
	int ref = 0;
	struct xfs_mru_cache_elem *mru;

	ASSERT(S_ISREG(ip->i_d.di_mode));

	pip = xfs_filestream_get_parent(ip);
	if (!pip)
	goto out;

	mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
	if (!mru)
	goto out;

	item = container_of(mru, struct xfs_fstrm_item, mru);

	ag = item->ag;
	xfs_mru_cache_done(mp->m_filestream);

	ref = xfs_filestream_peek_ag(ip->i_mount, ag);
	out:
	TRACE_LOOKUP(mp, ip, pip, ag, ref);
	IRELE(pip);
	return ag;
	}

	/*
	* Make sure a directory has a filestream associated with it.
	*
	* This is called when creating regular files in an directory that has
	* filestreams enabled, so that a stream is ready by the time we need it
	* in the allocator for the files inside the directory.
	*/
	int
	xfs_filestream_associate(
	struct xfs_inode *pip)
	{
	struct xfs_mount *mp = pip->i_mount;
	struct xfs_mru_cache_elem *mru;
	xfs_agnumber_t startag, ag;

	ASSERT(S_ISDIR(pip->i_d.di_mode));

	/*
	* If the directory already has a file stream associated we're done.
	*/
	mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
	if (mru) {
	xfs_mru_cache_done(mp->m_filestream);
	return 0;
	}

	/*
	* Set the starting AG using the rotor for inode32, otherwise
	* use the directory inode's AG.
	*/
	if (mp->m_flags & XFS_MOUNT_32BITINODES) {
	xfs_agnumber_t 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);

	return xfs_filestream_pick_ag(pip, startag, &ag, 0, 0);
	}

	/*
	* Pick a new allocation group for the current file and its file stream.
	*
	* This is called when the allocator can't find a suitable extent in the
	* current AG, and we have to move the stream into a new AG with more space.
	*/
	int
	xfs_filestream_new_ag(
	struct xfs_bmalloca *ap,
	xfs_agnumber_t *agp)
	{
	struct xfs_inode ip = ap->ip, pip;
	struct xfs_mount *mp = ip->i_mount;
	xfs_extlen_t minlen = ap->length;
	xfs_agnumber_t startag = 0;
	int flags, err = 0;
	struct xfs_mru_cache_elem *mru;

	*agp = NULLAGNUMBER;

	pip = xfs_filestream_get_parent(ip);
	if (!pip)
	goto exit;

	mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
	if (mru) {
	struct xfs_fstrm_item *item =
	container_of(mru, struct xfs_fstrm_item, mru);
	startag = (item->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(pip, startag, agp, flags, minlen);

	/*
	* Only free the item here so we skip over the old AG earlier.
	*/
	if (mru)
	xfs_fstrm_free_func(mru);

	IRELE(pip);
	exit:
	if (*agp == NULLAGNUMBER)
	*agp = 0;
	return err;
	}

	void
	xfs_filestream_deassociate(
	struct xfs_inode *ip)
	{
	xfs_mru_cache_delete(ip->i_mount->m_filestream, ip->i_ino);
	}

	int
	xfs_filestream_mount(
	xfs_mount_t *mp)
	{
	/*
	* 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.
	*/
	return xfs_mru_cache_create(&mp->m_filestream, xfs_fstrm_centisecs * 10,
	10, xfs_fstrm_free_func);
	}

	void
	xfs_filestream_unmount(
	xfs_mount_t *mp)
	{
	xfs_mru_cache_destroy(mp->m_filestream);
	}


	/* needs to return a positive errno for the init path */
	int
	xfs_filestream_init(void)
	{
	item_zone = kmem_zone_init(sizeof(struct xfs_fstrm_item), "fstrm_item");
	if (!item_zone)
	return -ENOMEM;
	return 0;
	}

	void
	xfs_filestream_uninit(void)
	{
	kmem_zone_destroy(item_zone);
	}