/*

   * 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_bit.h"

  #include "xfs_log.h"

  #include "xfs_inum.h"

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

  #include "xfs_alloc.h"

  #include "xfs_quota.h"
  #include "xfs_mount.h"

  #include "xfs_bmap_btree.h"
  #include "xfs_ialloc_btree.h"

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

  #include "xfs_ialloc.h"
  #include "xfs_itable.h"

  #include "xfs_rtalloc.h"
  #include "xfs_error.h"

  #include "xfs_bmap.h"

  #include "xfs_attr.h"
  #include "xfs_buf_item.h"
  #include "xfs_trans_space.h"
  #include "xfs_utils.h"

  #include "xfs_qm.h"

  #include "xfs_trace.h"

  
  /*
   * The global quota manager. There is only one of these for the entire
   * system, _not_ one per file system. XQM keeps track of the overall
   * quota functionality, including maintaining the freelist and hash
   * tables of dquots.
   */

  struct mutex	xfs_Gqm_lock;

  struct xfs_qm	*xfs_Gqm;

  uint		ndquot;

  
  kmem_zone_t	*qm_dqzone;
  kmem_zone_t	*qm_dqtrxzone;

  
  STATIC void	xfs_qm_list_init(xfs_dqlist_t *, char *, int);
  STATIC void	xfs_qm_list_destroy(xfs_dqlist_t *);
  
  STATIC int	xfs_qm_init_quotainos(xfs_mount_t *);

  STATIC int	xfs_qm_init_quotainfo(xfs_mount_t *);

  STATIC int	xfs_qm_shake(struct shrinker *, struct shrink_control *);

  static struct shrinker xfs_qm_shaker = {
  	.shrink = xfs_qm_shake,
  	.seeks = DEFAULT_SEEKS,
  };

  /*
   * Initialize the XQM structure.
   * Note that there is not one quota manager per file system.
   */
  STATIC struct xfs_qm *
  xfs_Gqm_init(void)
  {

  	xfs_dqhash_t	*udqhash, *gdqhash;
  	xfs_qm_t	*xqm;

  	size_t		hsize;
  	uint		i;

  
  	/*
  	 * Initialize the dquot hash tables.
  	 */

  	udqhash = kmem_zalloc_greedy(&hsize,

  				     XFS_QM_HASHSIZE_LOW * sizeof(xfs_dqhash_t),

  				     XFS_QM_HASHSIZE_HIGH * sizeof(xfs_dqhash_t));
  	if (!udqhash)
  		goto out;
  
  	gdqhash = kmem_zalloc_large(hsize);

  	if (!gdqhash)

  		goto out_free_udqhash;

  	hsize /= sizeof(xfs_dqhash_t);

  	ndquot = hsize << 8;

  	xqm = kmem_zalloc(sizeof(xfs_qm_t), KM_SLEEP);
  	xqm->qm_dqhashmask = hsize - 1;
  	xqm->qm_usr_dqhtable = udqhash;
  	xqm->qm_grp_dqhtable = gdqhash;

  	ASSERT(xqm->qm_usr_dqhtable != NULL);
  	ASSERT(xqm->qm_grp_dqhtable != NULL);
  
  	for (i = 0; i < hsize; i++) {
  		xfs_qm_list_init(&(xqm->qm_usr_dqhtable[i]), "uxdqh", i);
  		xfs_qm_list_init(&(xqm->qm_grp_dqhtable[i]), "gxdqh", i);
  	}
  
  	/*
  	 * Freelist of all dquots of all file systems
  	 */

  	INIT_LIST_HEAD(&xqm->qm_dqfrlist);
  	xqm->qm_dqfrlist_cnt = 0;
  	mutex_init(&xqm->qm_dqfrlist_lock);

  
  	/*
  	 * dquot zone. we register our own low-memory callback.
  	 */
  	if (!qm_dqzone) {
  		xqm->qm_dqzone = kmem_zone_init(sizeof(xfs_dquot_t),
  						"xfs_dquots");
  		qm_dqzone = xqm->qm_dqzone;
  	} else
  		xqm->qm_dqzone = qm_dqzone;

  	register_shrinker(&xfs_qm_shaker);

  
  	/*
  	 * The t_dqinfo portion of transactions.
  	 */
  	if (!qm_dqtrxzone) {
  		xqm->qm_dqtrxzone = kmem_zone_init(sizeof(xfs_dquot_acct_t),
  						   "xfs_dqtrx");
  		qm_dqtrxzone = xqm->qm_dqtrxzone;
  	} else
  		xqm->qm_dqtrxzone = qm_dqtrxzone;
  
  	atomic_set(&xqm->qm_totaldquots, 0);
  	xqm->qm_dqfree_ratio = XFS_QM_DQFREE_RATIO;
  	xqm->qm_nrefs = 0;

  	return xqm;

  
   out_free_udqhash:
  	kmem_free_large(udqhash);
   out:
  	return NULL;

  }
  
  /*
   * Destroy the global quota manager when its reference count goes to zero.
   */

  STATIC void

  xfs_qm_destroy(
  	struct xfs_qm	*xqm)
  {

  	struct xfs_dquot *dqp, *n;

  	int		hsize, i;
  
  	ASSERT(xqm != NULL);
  	ASSERT(xqm->qm_nrefs == 0);

  	unregister_shrinker(&xfs_qm_shaker);

  	hsize = xqm->qm_dqhashmask + 1;
  	for (i = 0; i < hsize; i++) {
  		xfs_qm_list_destroy(&(xqm->qm_usr_dqhtable[i]));
  		xfs_qm_list_destroy(&(xqm->qm_grp_dqhtable[i]));
  	}

  	kmem_free_large(xqm->qm_usr_dqhtable);
  	kmem_free_large(xqm->qm_grp_dqhtable);

  	xqm->qm_usr_dqhtable = NULL;
  	xqm->qm_grp_dqhtable = NULL;
  	xqm->qm_dqhashmask = 0;

  
  	/* frlist cleanup */
  	mutex_lock(&xqm->qm_dqfrlist_lock);
  	list_for_each_entry_safe(dqp, n, &xqm->qm_dqfrlist, q_freelist) {
  		xfs_dqlock(dqp);

  		list_del_init(&dqp->q_freelist);
  		xfs_Gqm->qm_dqfrlist_cnt--;
  		xfs_dqunlock(dqp);
  		xfs_qm_dqdestroy(dqp);
  	}
  	mutex_unlock(&xqm->qm_dqfrlist_lock);
  	mutex_destroy(&xqm->qm_dqfrlist_lock);

  	kmem_free(xqm);

  }
  
  /*
   * Called at mount time to let XQM know that another file system is
   * starting quotas. This isn't crucial information as the individual mount
   * structures are pretty independent, but it helps the XQM keep a
   * global view of what's going on.
   */
  /* ARGSUSED */
  STATIC int
  xfs_qm_hold_quotafs_ref(
  	struct xfs_mount *mp)
  {
  	/*
  	 * Need to lock the xfs_Gqm structure for things like this. For example,
  	 * the structure could disappear between the entry to this routine and
  	 * a HOLD operation if not locked.
  	 */

  	mutex_lock(&xfs_Gqm_lock);

  	if (!xfs_Gqm) {

  		xfs_Gqm = xfs_Gqm_init();

  		if (!xfs_Gqm) {
  			mutex_unlock(&xfs_Gqm_lock);

  			return ENOMEM;

  		}

  	}

  	/*
  	 * We can keep a list of all filesystems with quotas mounted for
  	 * debugging and statistical purposes, but ...
  	 * Just take a reference and get out.
  	 */

  	xfs_Gqm->qm_nrefs++;
  	mutex_unlock(&xfs_Gqm_lock);

  
  	return 0;
  }
  
  
  /*
   * Release the reference that a filesystem took at mount time,
   * so that we know when we need to destroy the entire quota manager.
   */
  /* ARGSUSED */
  STATIC void
  xfs_qm_rele_quotafs_ref(
  	struct xfs_mount *mp)
  {

  	xfs_dquot_t	*dqp, *n;

  
  	ASSERT(xfs_Gqm);
  	ASSERT(xfs_Gqm->qm_nrefs > 0);
  
  	/*
  	 * Go thru the freelist and destroy all inactive dquots.
  	 */

  	mutex_lock(&xfs_Gqm->qm_dqfrlist_lock);

  	list_for_each_entry_safe(dqp, n, &xfs_Gqm->qm_dqfrlist, q_freelist) {

  		xfs_dqlock(dqp);

  		if (dqp->dq_flags & XFS_DQ_INACTIVE) {
  			ASSERT(dqp->q_mount == NULL);
  			ASSERT(! XFS_DQ_IS_DIRTY(dqp));

  			ASSERT(list_empty(&dqp->q_hashlist));

  			ASSERT(list_empty(&dqp->q_mplist));

  			list_del_init(&dqp->q_freelist);
  			xfs_Gqm->qm_dqfrlist_cnt--;

  			xfs_dqunlock(dqp);
  			xfs_qm_dqdestroy(dqp);
  		} else {
  			xfs_dqunlock(dqp);
  		}

  	}

  	mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock);

  
  	/*
  	 * Destroy the entire XQM. If somebody mounts with quotaon, this'll
  	 * be restarted.
  	 */

  	mutex_lock(&xfs_Gqm_lock);
  	if (--xfs_Gqm->qm_nrefs == 0) {

  		xfs_qm_destroy(xfs_Gqm);
  		xfs_Gqm = NULL;
  	}

  	mutex_unlock(&xfs_Gqm_lock);

  }
  
  /*

   * Just destroy the quotainfo structure.
   */
  void

  xfs_qm_unmount(
  	struct xfs_mount	*mp)

  {

  	if (mp->m_quotainfo) {

  		xfs_qm_dqpurge_all(mp, XFS_QMOPT_QUOTALL);

  		xfs_qm_destroy_quotainfo(mp);

  	}

  }
  
  
  /*
   * This is called from xfs_mountfs to start quotas and initialize all
   * necessary data structures like quotainfo.  This is also responsible for
   * running a quotacheck as necessary.  We are guaranteed that the superblock
   * is consistently read in at this point.

   *
   * If we fail here, the mount will continue with quota turned off. We don't
   * need to inidicate success or failure at all.

   */

  void

  xfs_qm_mount_quotas(

  	xfs_mount_t	*mp)

  {

  	int		error = 0;
  	uint		sbf;

  	/*
  	 * If quotas on realtime volumes is not supported, we disable
  	 * quotas immediately.
  	 */
  	if (mp->m_sb.sb_rextents) {

  		xfs_notice(mp, "Cannot turn on quotas for realtime filesystem");

  		mp->m_qflags = 0;
  		goto write_changes;
  	}

  	ASSERT(XFS_IS_QUOTA_RUNNING(mp));

  	/*
  	 * Allocate the quotainfo structure inside the mount struct, and
  	 * create quotainode(s), and change/rev superblock if necessary.
  	 */

  	error = xfs_qm_init_quotainfo(mp);
  	if (error) {

  		/*
  		 * We must turn off quotas.
  		 */
  		ASSERT(mp->m_quotainfo == NULL);
  		mp->m_qflags = 0;
  		goto write_changes;
  	}
  	/*
  	 * If any of the quotas are not consistent, do a quotacheck.
  	 */

  	if (XFS_QM_NEED_QUOTACHECK(mp)) {

  		error = xfs_qm_quotacheck(mp);
  		if (error) {
  			/* Quotacheck failed and disabled quotas. */
  			return;

  		}

  	}

  	/* 
  	 * If one type of quotas is off, then it will lose its
  	 * quotachecked status, since we won't be doing accounting for
  	 * that type anymore.
  	 */

  	if (!XFS_IS_UQUOTA_ON(mp))

  		mp->m_qflags &= ~XFS_UQUOTA_CHKD;

  	if (!(XFS_IS_GQUOTA_ON(mp) || XFS_IS_PQUOTA_ON(mp)))

  		mp->m_qflags &= ~XFS_OQUOTA_CHKD;

   write_changes:
  	/*

  	 * We actually don't have to acquire the m_sb_lock at all.

  	 * This can only be called from mount, and that's single threaded. XXX
  	 */

  	spin_lock(&mp->m_sb_lock);

  	sbf = mp->m_sb.sb_qflags;
  	mp->m_sb.sb_qflags = mp->m_qflags & XFS_MOUNT_QUOTA_ALL;

  	spin_unlock(&mp->m_sb_lock);

  
  	if (sbf != (mp->m_qflags & XFS_MOUNT_QUOTA_ALL)) {
  		if (xfs_qm_write_sb_changes(mp, XFS_SB_QFLAGS)) {
  			/*
  			 * We could only have been turning quotas off.
  			 * We aren't in very good shape actually because
  			 * the incore structures are convinced that quotas are
  			 * off, but the on disk superblock doesn't know that !
  			 */
  			ASSERT(!(XFS_IS_QUOTA_RUNNING(mp)));

  			xfs_alert(mp, "%s: Superblock update failed!",
  				__func__);

  		}
  	}
  
  	if (error) {

  		xfs_warn(mp, "Failed to initialize disk quotas.");

  		return;

  	}

  }
  
  /*
   * Called from the vfsops layer.
   */

  void

  xfs_qm_unmount_quotas(
  	xfs_mount_t	*mp)
  {

  	/*
  	 * Release the dquots that root inode, et al might be holding,
  	 * before we flush quotas and blow away the quotainfo structure.
  	 */
  	ASSERT(mp->m_rootip);
  	xfs_qm_dqdetach(mp->m_rootip);
  	if (mp->m_rbmip)
  		xfs_qm_dqdetach(mp->m_rbmip);
  	if (mp->m_rsumip)
  		xfs_qm_dqdetach(mp->m_rsumip);
  
  	/*

  	 * Release the quota inodes.

  	 */

  	if (mp->m_quotainfo) {

  		if (mp->m_quotainfo->qi_uquotaip) {
  			IRELE(mp->m_quotainfo->qi_uquotaip);
  			mp->m_quotainfo->qi_uquotaip = NULL;

  		}

  		if (mp->m_quotainfo->qi_gquotaip) {
  			IRELE(mp->m_quotainfo->qi_gquotaip);
  			mp->m_quotainfo->qi_gquotaip = NULL;

  		}
  	}

  }
  
  /*
   * Flush all dquots of the given file system to disk. The dquots are
   * _not_ purged from memory here, just their data written to disk.
   */

  STATIC int

  xfs_qm_dqflush_all(

  	struct xfs_mount	*mp,
  	int			sync_mode)

  {

  	struct xfs_quotainfo	*q = mp->m_quotainfo;
  	int			recl;
  	struct xfs_dquot	*dqp;

  	int			error;

  	if (!q)

  		return 0;

  again:

  	mutex_lock(&q->qi_dqlist_lock);
  	list_for_each_entry(dqp, &q->qi_dqlist, q_mplist) {

  		xfs_dqlock(dqp);
  		if (! XFS_DQ_IS_DIRTY(dqp)) {
  			xfs_dqunlock(dqp);
  			continue;
  		}

  		/* XXX a sentinel would be better */

  		recl = q->qi_dqreclaims;

  		if (!xfs_dqflock_nowait(dqp)) {

  			/*
  			 * If we can't grab the flush lock then check
  			 * to see if the dquot has been flushed delayed
  			 * write.  If so, grab its buffer and send it
  			 * out immediately.  We'll be able to acquire
  			 * the flush lock when the I/O completes.
  			 */
  			xfs_qm_dqflock_pushbuf_wait(dqp);
  		}
  		/*
  		 * Let go of the mplist lock. We don't want to hold it
  		 * across a disk write.
  		 */

  		mutex_unlock(&q->qi_dqlist_lock);

  		error = xfs_qm_dqflush(dqp, sync_mode);

  		xfs_dqunlock(dqp);
  		if (error)

  			return error;

  		mutex_lock(&q->qi_dqlist_lock);
  		if (recl != q->qi_dqreclaims) {
  			mutex_unlock(&q->qi_dqlist_lock);

  			/* XXX restart limit */
  			goto again;
  		}
  	}

  	mutex_unlock(&q->qi_dqlist_lock);

  	/* return ! busy */

  	return 0;

  }
  /*
   * Release the group dquot pointers the user dquots may be
   * carrying around as a hint. mplist is locked on entry and exit.
   */
  STATIC void
  xfs_qm_detach_gdquots(

  	struct xfs_mount	*mp)

  {

  	struct xfs_quotainfo	*q = mp->m_quotainfo;
  	struct xfs_dquot	*dqp, *gdqp;
  	int			nrecl;

  
   again:

  	ASSERT(mutex_is_locked(&q->qi_dqlist_lock));
  	list_for_each_entry(dqp, &q->qi_dqlist, q_mplist) {

  		xfs_dqlock(dqp);
  		if ((gdqp = dqp->q_gdquot)) {
  			xfs_dqlock(gdqp);
  			dqp->q_gdquot = NULL;
  		}
  		xfs_dqunlock(dqp);
  
  		if (gdqp) {
  			/*
  			 * Can't hold the mplist lock across a dqput.
  			 * XXXmust convert to marker based iterations here.
  			 */

  			nrecl = q->qi_dqreclaims;
  			mutex_unlock(&q->qi_dqlist_lock);

  			xfs_qm_dqput(gdqp);

  			mutex_lock(&q->qi_dqlist_lock);
  			if (nrecl != q->qi_dqreclaims)

  				goto again;
  		}

  	}
  }
  
  /*
   * Go through all the incore dquots of this file system and take them
   * off the mplist and hashlist, if the dquot type matches the dqtype
   * parameter. This is used when turning off quota accounting for
   * users and/or groups, as well as when the filesystem is unmounting.
   */
  STATIC int
  xfs_qm_dqpurge_int(

  	struct xfs_mount	*mp,
  	uint			flags)

  {

  	struct xfs_quotainfo	*q = mp->m_quotainfo;
  	struct xfs_dquot	*dqp, *n;
  	uint			dqtype;
  	int			nrecl;
  	int			nmisses;

  	if (!q)

  		return 0;

  
  	dqtype = (flags & XFS_QMOPT_UQUOTA) ? XFS_DQ_USER : 0;

  	dqtype |= (flags & XFS_QMOPT_PQUOTA) ? XFS_DQ_PROJ : 0;

  	dqtype |= (flags & XFS_QMOPT_GQUOTA) ? XFS_DQ_GROUP : 0;

  	mutex_lock(&q->qi_dqlist_lock);

  
  	/*
  	 * In the first pass through all incore dquots of this filesystem,
  	 * we release the group dquot pointers the user dquots may be
  	 * carrying around as a hint. We need to do this irrespective of
  	 * what's being turned off.
  	 */
  	xfs_qm_detach_gdquots(mp);
  
        again:
  	nmisses = 0;

  	ASSERT(mutex_is_locked(&q->qi_dqlist_lock));

  	/*
  	 * Try to get rid of all of the unwanted dquots. The idea is to
  	 * get them off mplist and hashlist, but leave them on freelist.
  	 */

  	list_for_each_entry_safe(dqp, n, &q->qi_dqlist, q_mplist) {

  		/*
  		 * It's OK to look at the type without taking dqlock here.
  		 * We're holding the mplist lock here, and that's needed for
  		 * a dqreclaim.
  		 */

  		if ((dqp->dq_flags & dqtype) == 0)

  			continue;

  		if (!mutex_trylock(&dqp->q_hash->qh_lock)) {

  			nrecl = q->qi_dqreclaims;
  			mutex_unlock(&q->qi_dqlist_lock);

  			mutex_lock(&dqp->q_hash->qh_lock);

  			mutex_lock(&q->qi_dqlist_lock);

  
  			/*
  			 * XXXTheoretically, we can get into a very long
  			 * ping pong game here.
  			 * No one can be adding dquots to the mplist at
  			 * this point, but somebody might be taking things off.
  			 */

  			if (nrecl != q->qi_dqreclaims) {

  				mutex_unlock(&dqp->q_hash->qh_lock);

  				goto again;
  			}
  		}
  
  		/*
  		 * Take the dquot off the mplist and hashlist. It may remain on
  		 * freelist in INACTIVE state.
  		 */

  		nmisses += xfs_qm_dqpurge(dqp);

  	}

  	mutex_unlock(&q->qi_dqlist_lock);

  	return nmisses;
  }
  
  int
  xfs_qm_dqpurge_all(
  	xfs_mount_t	*mp,
  	uint		flags)
  {
  	int		ndquots;
  
  	/*
  	 * Purge the dquot cache.
  	 * None of the dquots should really be busy at this point.
  	 */
  	if (mp->m_quotainfo) {
  		while ((ndquots = xfs_qm_dqpurge_int(mp, flags))) {
  			delay(ndquots * 10);
  		}
  	}
  	return 0;
  }
  
  STATIC int
  xfs_qm_dqattach_one(
  	xfs_inode_t	*ip,
  	xfs_dqid_t	id,
  	uint		type,
  	uint		doalloc,

  	xfs_dquot_t	*udqhint, /* hint */
  	xfs_dquot_t	**IO_idqpp)
  {
  	xfs_dquot_t	*dqp;
  	int		error;

  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

  	error = 0;

  	/*
  	 * See if we already have it in the inode itself. IO_idqpp is
  	 * &i_udquot or &i_gdquot. This made the code look weird, but
  	 * made the logic a lot simpler.
  	 */

  	dqp = *IO_idqpp;
  	if (dqp) {

  		trace_xfs_dqattach_found(dqp);

  		return 0;

  	}
  
  	/*
  	 * udqhint is the i_udquot field in inode, and is non-NULL only

  	 * when the type arg is group/project. Its purpose is to save a

  	 * lookup by dqid (xfs_qm_dqget) by caching a group dquot inside
  	 * the user dquot.
  	 */

  	if (udqhint) {
  		ASSERT(type == XFS_DQ_GROUP || type == XFS_DQ_PROJ);

  		xfs_dqlock(udqhint);

  		/*
  		 * No need to take dqlock to look at the id.
  		 *
  		 * The ID can't change until it gets reclaimed, and it won't
  		 * be reclaimed as long as we have a ref from inode and we
  		 * hold the ilock.
  		 */
  		dqp = udqhint->q_gdquot;
  		if (dqp && be32_to_cpu(dqp->q_core.d_id) == id) {
  			xfs_dqlock(dqp);
  			XFS_DQHOLD(dqp);
  			ASSERT(*IO_idqpp == NULL);
  			*IO_idqpp = dqp;

  			xfs_dqunlock(dqp);
  			xfs_dqunlock(udqhint);

  			return 0;

  		}

  
  		/*
  		 * We can't hold a dquot lock when we call the dqget code.
  		 * We'll deadlock in no time, because of (not conforming to)
  		 * lock ordering - the inodelock comes before any dquot lock,
  		 * and we may drop and reacquire the ilock in xfs_qm_dqget().
  		 */

  		xfs_dqunlock(udqhint);

  	}

  	/*
  	 * Find the dquot from somewhere. This bumps the
  	 * reference count of dquot and returns it locked.
  	 * This can return ENOENT if dquot didn't exist on
  	 * disk and we didn't ask it to allocate;
  	 * ESRCH if quotas got turned off suddenly.
  	 */

  	error = xfs_qm_dqget(ip->i_mount, ip, id, type, XFS_QMOPT_DOWARN, &dqp);
  	if (error)
  		return error;

  	trace_xfs_dqattach_get(dqp);

  	/*
  	 * dqget may have dropped and re-acquired the ilock, but it guarantees
  	 * that the dquot returned is the one that should go in the inode.
  	 */
  	*IO_idqpp = dqp;

  	xfs_dqunlock(dqp);
  	return 0;

  }
  
  
  /*
   * Given a udquot and gdquot, attach a ptr to the group dquot in the
   * udquot as a hint for future lookups. The idea sounds simple, but the
   * execution isn't, because the udquot might have a group dquot attached

   * already and getting rid of that gets us into lock ordering constraints.

   * The process is complicated more by the fact that the dquots may or may not
   * be locked on entry.
   */
  STATIC void
  xfs_qm_dqattach_grouphint(
  	xfs_dquot_t	*udq,

  	xfs_dquot_t	*gdq)

  {
  	xfs_dquot_t	*tmp;

  	xfs_dqlock(udq);

  
  	if ((tmp = udq->q_gdquot)) {
  		if (tmp == gdq) {

  			xfs_dqunlock(udq);

  			return;
  		}
  
  		udq->q_gdquot = NULL;
  		/*
  		 * We can't keep any dqlocks when calling dqrele,
  		 * because the freelist lock comes before dqlocks.
  		 */
  		xfs_dqunlock(udq);

  		/*
  		 * we took a hard reference once upon a time in dqget,
  		 * so give it back when the udquot no longer points at it
  		 * dqput() does the unlocking of the dquot.
  		 */
  		xfs_qm_dqrele(tmp);
  
  		xfs_dqlock(udq);
  		xfs_dqlock(gdq);
  
  	} else {
  		ASSERT(XFS_DQ_IS_LOCKED(udq));

  		xfs_dqlock(gdq);

  	}
  
  	ASSERT(XFS_DQ_IS_LOCKED(udq));
  	ASSERT(XFS_DQ_IS_LOCKED(gdq));
  	/*
  	 * Somebody could have attached a gdquot here,
  	 * when we dropped the uqlock. If so, just do nothing.
  	 */
  	if (udq->q_gdquot == NULL) {
  		XFS_DQHOLD(gdq);
  		udq->q_gdquot = gdq;
  	}

  
  	xfs_dqunlock(gdq);
  	xfs_dqunlock(udq);

  }
  
  
  /*

   * Given a locked inode, attach dquot(s) to it, taking U/G/P-QUOTAON
   * into account.

   * If XFS_QMOPT_DQALLOC, the dquot(s) will be allocated if needed.

   * Inode may get unlocked and relocked in here, and the caller must deal with
   * the consequences.
   */
  int

  xfs_qm_dqattach_locked(

  	xfs_inode_t	*ip,
  	uint		flags)
  {
  	xfs_mount_t	*mp = ip->i_mount;
  	uint		nquotas = 0;
  	int		error = 0;

  	if (!XFS_IS_QUOTA_RUNNING(mp) ||
  	    !XFS_IS_QUOTA_ON(mp) ||
  	    !XFS_NOT_DQATTACHED(mp, ip) ||
  	    ip->i_ino == mp->m_sb.sb_uquotino ||
  	    ip->i_ino == mp->m_sb.sb_gquotino)

  		return 0;

  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

  
  	if (XFS_IS_UQUOTA_ON(mp)) {
  		error = xfs_qm_dqattach_one(ip, ip->i_d.di_uid, XFS_DQ_USER,
  						flags & XFS_QMOPT_DQALLOC,

  						NULL, &ip->i_udquot);
  		if (error)
  			goto done;
  		nquotas++;
  	}

  
  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

  	if (XFS_IS_OQUOTA_ON(mp)) {
  		error = XFS_IS_GQUOTA_ON(mp) ?
  			xfs_qm_dqattach_one(ip, ip->i_d.di_gid, XFS_DQ_GROUP,
  						flags & XFS_QMOPT_DQALLOC,

  						ip->i_udquot, &ip->i_gdquot) :

  			xfs_qm_dqattach_one(ip, xfs_get_projid(ip), XFS_DQ_PROJ,

  						flags & XFS_QMOPT_DQALLOC,

  						ip->i_udquot, &ip->i_gdquot);
  		/*
  		 * Don't worry about the udquot that we may have
  		 * attached above. It'll get detached, if not already.
  		 */
  		if (error)
  			goto done;
  		nquotas++;
  	}
  
  	/*
  	 * Attach this group quota to the user quota as a hint.
  	 * This WON'T, in general, result in a thrash.
  	 */
  	if (nquotas == 2) {

  		ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

  		ASSERT(ip->i_udquot);
  		ASSERT(ip->i_gdquot);
  
  		/*
  		 * We may or may not have the i_udquot locked at this point,
  		 * but this check is OK since we don't depend on the i_gdquot to
  		 * be accurate 100% all the time. It is just a hint, and this
  		 * will succeed in general.
  		 */
  		if (ip->i_udquot->q_gdquot == ip->i_gdquot)
  			goto done;
  		/*
  		 * Attach i_gdquot to the gdquot hint inside the i_udquot.
  		 */

  		xfs_qm_dqattach_grouphint(ip->i_udquot, ip->i_gdquot);

  	}

   done:

  #ifdef DEBUG
  	if (!error) {

  		if (XFS_IS_UQUOTA_ON(mp))
  			ASSERT(ip->i_udquot);

  		if (XFS_IS_OQUOTA_ON(mp))

  			ASSERT(ip->i_gdquot);
  	}

  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

  #endif

  	return error;
  }

  int
  xfs_qm_dqattach(
  	struct xfs_inode	*ip,
  	uint			flags)
  {
  	int			error;
  
  	xfs_ilock(ip, XFS_ILOCK_EXCL);
  	error = xfs_qm_dqattach_locked(ip, flags);
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);

  	return error;

  }
  
  /*
   * Release dquots (and their references) if any.
   * The inode should be locked EXCL except when this's called by
   * xfs_ireclaim.
   */
  void
  xfs_qm_dqdetach(
  	xfs_inode_t	*ip)
  {
  	if (!(ip->i_udquot || ip->i_gdquot))
  		return;

  	trace_xfs_dquot_dqdetach(ip);

  	ASSERT(ip->i_ino != ip->i_mount->m_sb.sb_uquotino);
  	ASSERT(ip->i_ino != ip->i_mount->m_sb.sb_gquotino);

  	if (ip->i_udquot) {
  		xfs_qm_dqrele(ip->i_udquot);
  		ip->i_udquot = NULL;
  	}
  	if (ip->i_gdquot) {
  		xfs_qm_dqrele(ip->i_gdquot);
  		ip->i_gdquot = NULL;
  	}
  }

  int
  xfs_qm_sync(

  	struct xfs_mount	*mp,
  	int			flags)

  {

  	struct xfs_quotainfo	*q = mp->m_quotainfo;
  	int			recl, restarts;
  	struct xfs_dquot	*dqp;
  	int			error;

  	if (!XFS_IS_QUOTA_RUNNING(mp) || !XFS_IS_QUOTA_ON(mp))

  		return 0;

  	restarts = 0;

  
    again:

  	mutex_lock(&q->qi_dqlist_lock);

  	/*
  	 * dqpurge_all() also takes the mplist lock and iterate thru all dquots
  	 * in quotaoff. However, if the QUOTA_ACTIVE bits are not cleared
  	 * when we have the mplist lock, we know that dquots will be consistent
  	 * as long as we have it locked.
  	 */

  	if (!XFS_IS_QUOTA_ON(mp)) {

  		mutex_unlock(&q->qi_dqlist_lock);

  		return 0;

  	}

  	ASSERT(mutex_is_locked(&q->qi_dqlist_lock));
  	list_for_each_entry(dqp, &q->qi_dqlist, q_mplist) {

  		/*
  		 * If this is vfs_sync calling, then skip the dquots that
  		 * don't 'seem' to be dirty. ie. don't acquire dqlock.
  		 * This is very similar to what xfs_sync does with inodes.
  		 */

  		if (flags & SYNC_TRYLOCK) {
  			if (!XFS_DQ_IS_DIRTY(dqp))

  				continue;

  			if (!xfs_qm_dqlock_nowait(dqp))

  				continue;
  		} else {
  			xfs_dqlock(dqp);
  		}
  
  		/*
  		 * Now, find out for sure if this dquot is dirty or not.
  		 */
  		if (! XFS_DQ_IS_DIRTY(dqp)) {
  			xfs_dqunlock(dqp);
  			continue;
  		}
  
  		/* XXX a sentinel would be better */

  		recl = q->qi_dqreclaims;

  		if (!xfs_dqflock_nowait(dqp)) {

  			if (flags & SYNC_TRYLOCK) {

  				xfs_dqunlock(dqp);
  				continue;
  			}
  			/*
  			 * If we can't grab the flush lock then if the caller

  			 * really wanted us to give this our best shot, so

  			 * see if we can give a push to the buffer before we wait
  			 * on the flush lock. At this point, we know that

  			 * even though the dquot is being flushed,

  			 * it has (new) dirty data.
  			 */
  			xfs_qm_dqflock_pushbuf_wait(dqp);
  		}
  		/*
  		 * Let go of the mplist lock. We don't want to hold it
  		 * across a disk write
  		 */

  		mutex_unlock(&q->qi_dqlist_lock);

  		error = xfs_qm_dqflush(dqp, flags);

  		xfs_dqunlock(dqp);
  		if (error && XFS_FORCED_SHUTDOWN(mp))

  			return 0;	/* Need to prevent umount failure */

  		else if (error)

  			return error;

  		mutex_lock(&q->qi_dqlist_lock);
  		if (recl != q->qi_dqreclaims) {

  			if (++restarts >= XFS_QM_SYNC_MAX_RESTARTS)
  				break;

  			mutex_unlock(&q->qi_dqlist_lock);

  			goto again;
  		}
  	}

  	mutex_unlock(&q->qi_dqlist_lock);

  	return 0;

  }

  /*
   * The hash chains and the mplist use the same xfs_dqhash structure as
   * their list head, but we can take the mplist qh_lock and one of the
   * hash qh_locks at the same time without any problem as they aren't
   * related.
   */
  static struct lock_class_key xfs_quota_mplist_class;

  
  /*
   * This initializes all the quota information that's kept in the
   * mount structure
   */

  STATIC int

  xfs_qm_init_quotainfo(
  	xfs_mount_t	*mp)
  {
  	xfs_quotainfo_t *qinf;
  	int		error;
  	xfs_dquot_t	*dqp;
  
  	ASSERT(XFS_IS_QUOTA_RUNNING(mp));
  
  	/*
  	 * Tell XQM that we exist as soon as possible.
  	 */
  	if ((error = xfs_qm_hold_quotafs_ref(mp))) {

  		return error;

  	}
  
  	qinf = mp->m_quotainfo = kmem_zalloc(sizeof(xfs_quotainfo_t), KM_SLEEP);
  
  	/*
  	 * See if quotainodes are setup, and if not, allocate them,
  	 * and change the superblock accordingly.
  	 */
  	if ((error = xfs_qm_init_quotainos(mp))) {

  		kmem_free(qinf);

  		mp->m_quotainfo = NULL;

  		return error;

  	}

  	INIT_LIST_HEAD(&qinf->qi_dqlist);
  	mutex_init(&qinf->qi_dqlist_lock);
  	lockdep_set_class(&qinf->qi_dqlist_lock, &xfs_quota_mplist_class);

  	qinf->qi_dqreclaims = 0;
  
  	/* mutex used to serialize quotaoffs */

  	mutex_init(&qinf->qi_quotaofflock);

  
  	/* Precalc some constants */
  	qinf->qi_dqchunklen = XFS_FSB_TO_BB(mp, XFS_DQUOT_CLUSTER_SIZE_FSB);
  	ASSERT(qinf->qi_dqchunklen);
  	qinf->qi_dqperchunk = BBTOB(qinf->qi_dqchunklen);
  	do_div(qinf->qi_dqperchunk, sizeof(xfs_dqblk_t));
  
  	mp->m_qflags |= (mp->m_sb.sb_qflags & XFS_ALL_QUOTA_CHKD);
  
  	/*
  	 * We try to get the limits from the superuser's limits fields.
  	 * This is quite hacky, but it is standard quota practice.
  	 * We look at the USR dquot with id == 0 first, but if user quotas
  	 * are not enabled we goto the GRP dquot with id == 0.
  	 * We don't really care to keep separate default limits for user
  	 * and group quotas, at least not at this point.
  	 */
  	error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t)0,

  			     XFS_IS_UQUOTA_RUNNING(mp) ? XFS_DQ_USER : 
  			     (XFS_IS_GQUOTA_RUNNING(mp) ? XFS_DQ_GROUP :
  				XFS_DQ_PROJ),

  			     XFS_QMOPT_DQSUSER|XFS_QMOPT_DOWARN,
  			     &dqp);
  	if (! error) {
  		xfs_disk_dquot_t	*ddqp = &dqp->q_core;
  
  		/*
  		 * The warnings and timers set the grace period given to
  		 * a user or group before he or she can not perform any
  		 * more writing. If it is zero, a default is used.
  		 */

  		qinf->qi_btimelimit = ddqp->d_btimer ?
  			be32_to_cpu(ddqp->d_btimer) : XFS_QM_BTIMELIMIT;
  		qinf->qi_itimelimit = ddqp->d_itimer ?
  			be32_to_cpu(ddqp->d_itimer) : XFS_QM_ITIMELIMIT;
  		qinf->qi_rtbtimelimit = ddqp->d_rtbtimer ?
  			be32_to_cpu(ddqp->d_rtbtimer) : XFS_QM_RTBTIMELIMIT;
  		qinf->qi_bwarnlimit = ddqp->d_bwarns ?
  			be16_to_cpu(ddqp->d_bwarns) : XFS_QM_BWARNLIMIT;
  		qinf->qi_iwarnlimit = ddqp->d_iwarns ?
  			be16_to_cpu(ddqp->d_iwarns) : XFS_QM_IWARNLIMIT;
  		qinf->qi_rtbwarnlimit = ddqp->d_rtbwarns ?
  			be16_to_cpu(ddqp->d_rtbwarns) : XFS_QM_RTBWARNLIMIT;
  		qinf->qi_bhardlimit = be64_to_cpu(ddqp->d_blk_hardlimit);
  		qinf->qi_bsoftlimit = be64_to_cpu(ddqp->d_blk_softlimit);
  		qinf->qi_ihardlimit = be64_to_cpu(ddqp->d_ino_hardlimit);
  		qinf->qi_isoftlimit = be64_to_cpu(ddqp->d_ino_softlimit);
  		qinf->qi_rtbhardlimit = be64_to_cpu(ddqp->d_rtb_hardlimit);
  		qinf->qi_rtbsoftlimit = be64_to_cpu(ddqp->d_rtb_softlimit);

   
  		/*
  		 * We sent the XFS_QMOPT_DQSUSER flag to dqget because
  		 * we don't want this dquot cached. We haven't done a
  		 * quotacheck yet, and quotacheck doesn't like incore dquots.
  		 */
  		xfs_qm_dqdestroy(dqp);
  	} else {
  		qinf->qi_btimelimit = XFS_QM_BTIMELIMIT;
  		qinf->qi_itimelimit = XFS_QM_ITIMELIMIT;
  		qinf->qi_rtbtimelimit = XFS_QM_RTBTIMELIMIT;
  		qinf->qi_bwarnlimit = XFS_QM_BWARNLIMIT;
  		qinf->qi_iwarnlimit = XFS_QM_IWARNLIMIT;

  		qinf->qi_rtbwarnlimit = XFS_QM_RTBWARNLIMIT;

  	}

  	return 0;

  }
  
  
  /*
   * Gets called when unmounting a filesystem or when all quotas get
   * turned off.
   * This purges the quota inodes, destroys locks and frees itself.
   */
  void
  xfs_qm_destroy_quotainfo(
  	xfs_mount_t	*mp)
  {
  	xfs_quotainfo_t *qi;
  
  	qi = mp->m_quotainfo;
  	ASSERT(qi != NULL);
  	ASSERT(xfs_Gqm != NULL);
  
  	/*
  	 * Release the reference that XQM kept, so that we know
  	 * when the XQM structure should be freed. We cannot assume
  	 * that xfs_Gqm is non-null after this point.
  	 */
  	xfs_qm_rele_quotafs_ref(mp);

  	ASSERT(list_empty(&qi->qi_dqlist));
  	mutex_destroy(&qi->qi_dqlist_lock);

  
  	if (qi->qi_uquotaip) {

  		IRELE(qi->qi_uquotaip);

  		qi->qi_uquotaip = NULL; /* paranoia */
  	}
  	if (qi->qi_gquotaip) {

  		IRELE(qi->qi_gquotaip);

  		qi->qi_gquotaip = NULL;
  	}
  	mutex_destroy(&qi->qi_quotaofflock);

  	kmem_free(qi);

  	mp->m_quotainfo = NULL;
  }
  
  
  
  /* ------------------- PRIVATE STATIC FUNCTIONS ----------------------- */
  
  /* ARGSUSED */
  STATIC void
  xfs_qm_list_init(
  	xfs_dqlist_t	*list,
  	char		*str,
  	int		n)
  {

  	mutex_init(&list->qh_lock);

  	INIT_LIST_HEAD(&list->qh_list);

  	list->qh_version = 0;
  	list->qh_nelems = 0;
  }
  
  STATIC void
  xfs_qm_list_destroy(
  	xfs_dqlist_t	*list)
  {
  	mutex_destroy(&(list->qh_lock));
  }

  /*
   * Create an inode and return with a reference already taken, but unlocked
   * This is how we create quota inodes
   */
  STATIC int
  xfs_qm_qino_alloc(
  	xfs_mount_t	*mp,
  	xfs_inode_t	**ip,
  	__int64_t	sbfields,
  	uint		flags)
  {
  	xfs_trans_t	*tp;
  	int		error;

  	int		committed;

  	tp = xfs_trans_alloc(mp, XFS_TRANS_QM_QINOCREATE);

  	if ((error = xfs_trans_reserve(tp,
  				      XFS_QM_QINOCREATE_SPACE_RES(mp),
  				      XFS_CREATE_LOG_RES(mp), 0,
  				      XFS_TRANS_PERM_LOG_RES,
  				      XFS_CREATE_LOG_COUNT))) {
  		xfs_trans_cancel(tp, 0);

  		return error;

  	}

  	error = xfs_dir_ialloc(&tp, NULL, S_IFREG, 1, 0, 0, 1, ip, &committed);
  	if (error) {

  		xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES |
  				 XFS_TRANS_ABORT);

  		return error;

  	}
  
  	/*

  	 * Make the changes in the superblock, and log those too.
  	 * sbfields arg may contain fields other than *QUOTINO;
  	 * VERSIONNUM for example.
  	 */

  	spin_lock(&mp->m_sb_lock);

  	if (flags & XFS_QMOPT_SBVERSION) {

  		ASSERT(!xfs_sb_version_hasquota(&mp->m_sb));

  		ASSERT((sbfields & (XFS_SB_VERSIONNUM | XFS_SB_UQUOTINO |
  				   XFS_SB_GQUOTINO | XFS_SB_QFLAGS)) ==
  		       (XFS_SB_VERSIONNUM | XFS_SB_UQUOTINO |
  			XFS_SB_GQUOTINO | XFS_SB_QFLAGS));

  		xfs_sb_version_addquota(&mp->m_sb);

  		mp->m_sb.sb_uquotino = NULLFSINO;
  		mp->m_sb.sb_gquotino = NULLFSINO;
  
  		/* qflags will get updated _after_ quotacheck */
  		mp->m_sb.sb_qflags = 0;

  	}
  	if (flags & XFS_QMOPT_UQUOTA)
  		mp->m_sb.sb_uquotino = (*ip)->i_ino;
  	else
  		mp->m_sb.sb_gquotino = (*ip)->i_ino;

  	spin_unlock(&mp->m_sb_lock);

  	xfs_mod_sb(tp, sbfields);

  	if ((error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES))) {

  		xfs_alert(mp, "%s failed (error %d)!", __func__, error);

  		return error;

  	}

  	return 0;

  }

  STATIC void

  xfs_qm_reset_dqcounts(
  	xfs_mount_t	*mp,
  	xfs_buf_t	*bp,
  	xfs_dqid_t	id,
  	uint		type)
  {
  	xfs_disk_dquot_t	*ddq;
  	int			j;

  	trace_xfs_reset_dqcounts(bp, _RET_IP_);

  	/*
  	 * Reset all counters and timers. They'll be
  	 * started afresh by xfs_qm_quotacheck.
  	 */
  #ifdef DEBUG
  	j = XFS_FSB_TO_B(mp, XFS_DQUOT_CLUSTER_SIZE_FSB);
  	do_div(j, sizeof(xfs_dqblk_t));

  	ASSERT(mp->m_quotainfo->qi_dqperchunk == j);

  #endif

  	ddq = bp->b_addr;

  	for (j = 0; j < mp->m_quotainfo->qi_dqperchunk; j++) {

  		/*
  		 * Do a sanity check, and if needed, repair the dqblk. Don't
  		 * output any warnings because it's perfectly possible to

  		 * find uninitialised dquot blks. See comment in xfs_qm_dqcheck.

  		 */

  		(void) xfs_qm_dqcheck(mp, ddq, id+j, type, XFS_QMOPT_DQREPAIR,

  				      "xfs_quotacheck");

  		ddq->d_bcount = 0;
  		ddq->d_icount = 0;
  		ddq->d_rtbcount = 0;
  		ddq->d_btimer = 0;
  		ddq->d_itimer = 0;
  		ddq->d_rtbtimer = 0;
  		ddq->d_bwarns = 0;
  		ddq->d_iwarns = 0;
  		ddq->d_rtbwarns = 0;

  		ddq = (xfs_disk_dquot_t *) ((xfs_dqblk_t *)ddq + 1);
  	}

  }
  
  STATIC int
  xfs_qm_dqiter_bufs(
  	xfs_mount_t	*mp,
  	xfs_dqid_t	firstid,
  	xfs_fsblock_t	bno,
  	xfs_filblks_t	blkcnt,
  	uint		flags)
  {
  	xfs_buf_t	*bp;
  	int		error;

  	int		type;

  
  	ASSERT(blkcnt > 0);

  	type = flags & XFS_QMOPT_UQUOTA ? XFS_DQ_USER :
  		(flags & XFS_QMOPT_PQUOTA ? XFS_DQ_PROJ : XFS_DQ_GROUP);

  	error = 0;
  
  	/*
  	 * Blkcnt arg can be a very big number, and might even be
  	 * larger than the log itself. So, we have to break it up into
  	 * manageable-sized transactions.
  	 * Note that we don't start a permanent transaction here; we might
  	 * not be able to get a log reservation for the whole thing up front,
  	 * and we don't really care to either, because we just discard
  	 * everything if we were to crash in the middle of this loop.
  	 */
  	while (blkcnt--) {
  		error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
  			      XFS_FSB_TO_DADDR(mp, bno),

  			      mp->m_quotainfo->qi_dqchunklen, 0, &bp);

  		if (error)
  			break;

  		xfs_qm_reset_dqcounts(mp, bp, firstid, type);

  		xfs_bdwrite(mp, bp);
  		/*
  		 * goto the next block.
  		 */
  		bno++;

  		firstid += mp->m_quotainfo->qi_dqperchunk;

  	}

  	return error;

  }
  
  /*

   * Iterate over all allocated USR/GRP/PRJ dquots in the system, calling a

   * caller supplied function for every chunk of dquots that we find.
   */
  STATIC int
  xfs_qm_dqiterate(
  	xfs_mount_t	*mp,
  	xfs_inode_t	*qip,
  	uint		flags)
  {
  	xfs_bmbt_irec_t		*map;
  	int			i, nmaps;	/* number of map entries */
  	int			error;		/* return value */
  	xfs_fileoff_t		lblkno;
  	xfs_filblks_t		maxlblkcnt;
  	xfs_dqid_t		firstid;
  	xfs_fsblock_t		rablkno;
  	xfs_filblks_t		rablkcnt;
  
  	error = 0;
  	/*

  	 * This looks racy, but we can't keep an inode lock across a

  	 * trans_reserve. But, this gets called during quotacheck, and that
  	 * happens only at mount time which is single threaded.
  	 */
  	if (qip->i_d.di_nblocks == 0)

  		return 0;

  
  	map = kmem_alloc(XFS_DQITER_MAP_SIZE * sizeof(*map), KM_SLEEP);
  
  	lblkno = 0;
  	maxlblkcnt = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_MAXIOFFSET(mp));
  	do {
  		nmaps = XFS_DQITER_MAP_SIZE;
  		/*
  		 * We aren't changing the inode itself. Just changing
  		 * some of its data. No new blocks are added here, and
  		 * the inode is never added to the transaction.
  		 */
  		xfs_ilock(qip, XFS_ILOCK_SHARED);
  		error = xfs_bmapi(NULL, qip, lblkno,
  				  maxlblkcnt - lblkno,
  				  XFS_BMAPI_METADATA,
  				  NULL,

  				  0, map, &nmaps, NULL);

  		xfs_iunlock(qip, XFS_ILOCK_SHARED);
  		if (error)
  			break;
  
  		ASSERT(nmaps <= XFS_DQITER_MAP_SIZE);
  		for (i = 0; i < nmaps; i++) {
  			ASSERT(map[i].br_startblock != DELAYSTARTBLOCK);
  			ASSERT(map[i].br_blockcount);
  
  
  			lblkno += map[i].br_blockcount;
  
  			if (map[i].br_startblock == HOLESTARTBLOCK)
  				continue;
  
  			firstid = (xfs_dqid_t) map[i].br_startoff *

  				mp->m_quotainfo->qi_dqperchunk;

  			/*
  			 * Do a read-ahead on the next extent.
  			 */
  			if ((i+1 < nmaps) &&
  			    (map[i+1].br_startblock != HOLESTARTBLOCK)) {
  				rablkcnt =  map[i+1].br_blockcount;
  				rablkno = map[i+1].br_startblock;
  				while (rablkcnt--) {

  					xfs_buf_readahead(mp->m_ddev_targp,

  					       XFS_FSB_TO_DADDR(mp, rablkno),

  					       mp->m_quotainfo->qi_dqchunklen);

  					rablkno++;
  				}
  			}
  			/*
  			 * Iterate thru all the blks in the extent and
  			 * reset the counters of all the dquots inside them.
  			 */
  			if ((error = xfs_qm_dqiter_bufs(mp,
  						       firstid,
  						       map[i].br_startblock,
  						       map[i].br_blockcount,
  						       flags))) {
  				break;
  			}
  		}
  
  		if (error)
  			break;
  	} while (nmaps > 0);

  	kmem_free(map);

  	return error;

  }
  
  /*
   * Called by dqusage_adjust in doing a quotacheck.

   *
   * Given the inode, and a dquot id this updates both the incore dqout as well
   * as the buffer copy. This is so that once the quotacheck is done, we can
   * just log all the buffers, as opposed to logging numerous updates to
   * individual dquots.

   */

  STATIC int

  xfs_qm_quotacheck_dqadjust(

  	struct xfs_inode	*ip,
  	xfs_dqid_t		id,
  	uint			type,

  	xfs_qcnt_t		nblks,
  	xfs_qcnt_t		rtblks)
  {

  	struct xfs_mount	*mp = ip->i_mount;
  	struct xfs_dquot	*dqp;
  	int			error;
  
  	error = xfs_qm_dqget(mp, ip, id, type,
  			     XFS_QMOPT_DQALLOC | XFS_QMOPT_DOWARN, &dqp);
  	if (error) {
  		/*
  		 * Shouldn't be able to turn off quotas here.
  		 */
  		ASSERT(error != ESRCH);
  		ASSERT(error != ENOENT);
  		return error;
  	}

  
  	trace_xfs_dqadjust(dqp);

  	/*
  	 * Adjust the inode count and the block count to reflect this inode's
  	 * resource usage.
  	 */

  	be64_add_cpu(&dqp->q_core.d_icount, 1);

  	dqp->q_res_icount++;
  	if (nblks) {

  		be64_add_cpu(&dqp->q_core.d_bcount, nblks);

  		dqp->q_res_bcount += nblks;
  	}
  	if (rtblks) {

  		be64_add_cpu(&dqp->q_core.d_rtbcount, rtblks);

  		dqp->q_res_rtbcount += rtblks;
  	}
  
  	/*
  	 * Set default limits, adjust timers (since we changed usages)

  	 *
  	 * There are no timers for the default values set in the root dquot.

  	 */

  	if (dqp->q_core.d_id) {

  		xfs_qm_adjust_dqlimits(mp, &dqp->q_core);
  		xfs_qm_adjust_dqtimers(mp, &dqp->q_core);

  	}
  
  	dqp->dq_flags |= XFS_DQ_DIRTY;

  	xfs_qm_dqput(dqp);
  	return 0;

  }
  
  STATIC int
  xfs_qm_get_rtblks(
  	xfs_inode_t	*ip,
  	xfs_qcnt_t	*O_rtblks)
  {
  	xfs_filblks_t	rtblks;			/* total rt blks */

  	xfs_extnum_t	idx;			/* extent record index */

  	xfs_ifork_t	*ifp;			/* inode fork pointer */
  	xfs_extnum_t	nextents;		/* number of extent entries */

  	int		error;
  
  	ASSERT(XFS_IS_REALTIME_INODE(ip));
  	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
  	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
  		if ((error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK)))

  			return error;

  	}
  	rtblks = 0;

  	nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);

  	for (idx = 0; idx < nextents; idx++)
  		rtblks += xfs_bmbt_get_blockcount(xfs_iext_get_ext(ifp, idx));

  	*O_rtblks = (xfs_qcnt_t)rtblks;

  	return 0;

  }
  
  /*
   * callback routine supplied to bulkstat(). Given an inumber, find its
   * dquots and update them to account for resources taken by that inode.
   */
  /* ARGSUSED */
  STATIC int
  xfs_qm_dqusage_adjust(
  	xfs_mount_t	*mp,		/* mount point for filesystem */
  	xfs_ino_t	ino,		/* inode number to get data for */
  	void		__user *buffer,	/* not used */
  	int		ubsize,		/* not used */

  	int		*ubused,	/* not used */

  	int		*res)		/* result code value */
  {
  	xfs_inode_t	*ip;

  	xfs_qcnt_t	nblks, rtblks = 0;

  	int		error;
  
  	ASSERT(XFS_IS_QUOTA_RUNNING(mp));
  
  	/*
  	 * rootino must have its resources accounted for, not so with the quota
  	 * inodes.
  	 */
  	if (ino == mp->m_sb.sb_uquotino || ino == mp->m_sb.sb_gquotino) {
  		*res = BULKSTAT_RV_NOTHING;
  		return XFS_ERROR(EINVAL);
  	}
  
  	/*
  	 * We don't _need_ to take the ilock EXCL. However, the xfs_qm_dqget
  	 * interface expects the inode to be exclusively locked because that's
  	 * the case in all other instances. It's OK that we do this because
  	 * quotacheck is done only at mount time.
  	 */

  	error = xfs_iget(mp, NULL, ino, 0, XFS_ILOCK_EXCL, &ip);
  	if (error) {

  		*res = BULKSTAT_RV_NOTHING;

  		return error;

  	}

  	ASSERT(ip->i_delayed_blks == 0);

  	if (XFS_IS_REALTIME_INODE(ip)) {

  		/*
  		 * Walk thru the extent list and count the realtime blocks.
  		 */

  		error = xfs_qm_get_rtblks(ip, &rtblks);
  		if (error)
  			goto error0;

  	}

  	nblks = (xfs_qcnt_t)ip->i_d.di_nblocks - rtblks;

  
  	/*
  	 * Add the (disk blocks and inode) resources occupied by this
  	 * inode to its dquots. We do this adjustment in the incore dquot,
  	 * and also copy the changes to its buffer.
  	 * We don't care about putting these changes in a transaction
  	 * envelope because if we crash in the middle of a 'quotacheck'
  	 * we have to start from the beginning anyway.
  	 * Once we're done, we'll log all the dquot bufs.
  	 *

  	 * The *QUOTA_ON checks below may look pretty racy, but quotachecks

  	 * and quotaoffs don't race. (Quotachecks happen at mount time only).
  	 */
  	if (XFS_IS_UQUOTA_ON(mp)) {

  		error = xfs_qm_quotacheck_dqadjust(ip, ip->i_d.di_uid,
  						   XFS_DQ_USER, nblks, rtblks);
  		if (error)
  			goto error0;

  	}

  
  	if (XFS_IS_GQUOTA_ON(mp)) {
  		error = xfs_qm_quotacheck_dqadjust(ip, ip->i_d.di_gid,
  						   XFS_DQ_GROUP, nblks, rtblks);
  		if (error)
  			goto error0;

  	}

  	if (XFS_IS_PQUOTA_ON(mp)) {

  		error = xfs_qm_quotacheck_dqadjust(ip, xfs_get_projid(ip),

  						   XFS_DQ_PROJ, nblks, rtblks);
  		if (error)
  			goto error0;
  	}
  
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  	IRELE(ip);

  	*res = BULKSTAT_RV_DIDONE;

  	return 0;

  
  error0:
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  	IRELE(ip);
  	*res = BULKSTAT_RV_GIVEUP;
  	return error;

  }
  
  /*
   * Walk thru all the filesystem inodes and construct a consistent view
   * of the disk quota world. If the quotacheck fails, disable quotas.
   */
  int
  xfs_qm_quotacheck(
  	xfs_mount_t	*mp)
  {
  	int		done, count, error;
  	xfs_ino_t	lastino;
  	size_t		structsz;
  	xfs_inode_t	*uip, *gip;
  	uint		flags;
  
  	count = INT_MAX;
  	structsz = 1;
  	lastino = 0;
  	flags = 0;

  	ASSERT(mp->m_quotainfo->qi_uquotaip || mp->m_quotainfo->qi_gquotaip);

  	ASSERT(XFS_IS_QUOTA_RUNNING(mp));
  
  	/*
  	 * There should be no cached dquots. The (simplistic) quotacheck
  	 * algorithm doesn't like that.
  	 */

  	ASSERT(list_empty(&mp->m_quotainfo->qi_dqlist));

  	xfs_notice(mp, "Quotacheck needed: Please wait.");

  
  	/*

  	 * First we go thru all the dquots on disk, USR and GRP/PRJ, and reset

  	 * their counters to zero. We need a clean slate.
  	 * We don't log our changes till later.
  	 */

  	uip = mp->m_quotainfo->qi_uquotaip;
  	if (uip) {
  		error = xfs_qm_dqiterate(mp, uip, XFS_QMOPT_UQUOTA);
  		if (error)

  			goto error_return;
  		flags |= XFS_UQUOTA_CHKD;
  	}

  	gip = mp->m_quotainfo->qi_gquotaip;
  	if (gip) {
  		error = xfs_qm_dqiterate(mp, gip, XFS_IS_GQUOTA_ON(mp) ?
  					XFS_QMOPT_GQUOTA : XFS_QMOPT_PQUOTA);
  		if (error)

  			goto error_return;

  		flags |= XFS_OQUOTA_CHKD;

  	}
  
  	do {
  		/*
  		 * Iterate thru all the inodes in the file system,
  		 * adjusting the corresponding dquot counters in core.
  		 */

  		error = xfs_bulkstat(mp, &lastino, &count,
  				     xfs_qm_dqusage_adjust,
  				     structsz, NULL, &done);
  		if (error)

  			break;

  	} while (!done);

  
  	/*

  	 * We've made all the changes that we need to make incore.
  	 * Flush them down to disk buffers if everything was updated
  	 * successfully.
  	 */
  	if (!error)

  		error = xfs_qm_dqflush_all(mp, 0);

  
  	/*

  	 * We can get this error if we couldn't do a dquot allocation inside
  	 * xfs_qm_dqusage_adjust (via bulkstat). We don't care about the
  	 * dirty dquots that might be cached, we just want to get rid of them
  	 * and turn quotaoff. The dquots won't be attached to any of the inodes
  	 * at this point (because we intentionally didn't in dqget_noattach).
  	 */
  	if (error) {

  		xfs_qm_dqpurge_all(mp, XFS_QMOPT_QUOTALL);

  		goto error_return;
  	}

  
  	/*
  	 * We didn't log anything, because if we crashed, we'll have to
  	 * start the quotacheck from scratch anyway. However, we must make
  	 * sure that our dquot changes are secure before we put the
  	 * quotacheck'd stamp on the superblock. So, here we do a synchronous
  	 * flush.
  	 */
  	XFS_bflush(mp->m_ddev_targp);
  
  	/*
  	 * If one type of quotas is off, then it will lose its
  	 * quotachecked status, since we won't be doing accounting for
  	 * that type anymore.
  	 */

  	mp->m_qflags &= ~(XFS_OQUOTA_CHKD | XFS_UQUOTA_CHKD);

  	mp->m_qflags |= flags;

   error_return:
  	if (error) {

  		xfs_warn(mp,
  	"Quotacheck: Unsuccessful (Error %d): Disabling quotas.",
  			error);

  		/*
  		 * We must turn off quotas.
  		 */
  		ASSERT(mp->m_quotainfo != NULL);
  		ASSERT(xfs_Gqm != NULL);
  		xfs_qm_destroy_quotainfo(mp);

  		if (xfs_mount_reset_sbqflags(mp)) {

  			xfs_warn(mp,
  				"Quotacheck: Failed to reset quota flags.");

  		}

  	} else
  		xfs_notice(mp, "Quotacheck: Done.");

  	return (error);
  }
  
  /*
   * This is called after the superblock has been read in and we're ready to
   * iget the quota inodes.
   */
  STATIC int
  xfs_qm_init_quotainos(
  	xfs_mount_t	*mp)
  {
  	xfs_inode_t	*uip, *gip;
  	int		error;
  	__int64_t	sbflags;
  	uint		flags;
  
  	ASSERT(mp->m_quotainfo);
  	uip = gip = NULL;
  	sbflags = 0;
  	flags = 0;
  
  	/*
  	 * Get the uquota and gquota inodes
  	 */

  	if (xfs_sb_version_hasquota(&mp->m_sb)) {

  		if (XFS_IS_UQUOTA_ON(mp) &&
  		    mp->m_sb.sb_uquotino != NULLFSINO) {
  			ASSERT(mp->m_sb.sb_uquotino > 0);
  			if ((error = xfs_iget(mp, NULL, mp->m_sb.sb_uquotino,

  					     0, 0, &uip)))

  				return XFS_ERROR(error);
  		}

  		if (XFS_IS_OQUOTA_ON(mp) &&

  		    mp->m_sb.sb_gquotino != NULLFSINO) {
  			ASSERT(mp->m_sb.sb_gquotino > 0);
  			if ((error = xfs_iget(mp, NULL, mp->m_sb.sb_gquotino,

  					     0, 0, &gip))) {

  				if (uip)

  					IRELE(uip);

  				return XFS_ERROR(error);
  			}
  		}
  	} else {
  		flags |= XFS_QMOPT_SBVERSION;
  		sbflags |= (XFS_SB_VERSIONNUM | XFS_SB_UQUOTINO |
  			    XFS_SB_GQUOTINO | XFS_SB_QFLAGS);
  	}
  
  	/*
  	 * Create the two inodes, if they don't exist already. The changes
  	 * made above will get added to a transaction and logged in one of
  	 * the qino_alloc calls below.  If the device is readonly,
  	 * temporarily switch to read-write to do this.
  	 */
  	if (XFS_IS_UQUOTA_ON(mp) && uip == NULL) {
  		if ((error = xfs_qm_qino_alloc(mp, &uip,
  					      sbflags | XFS_SB_UQUOTINO,
  					      flags | XFS_QMOPT_UQUOTA)))
  			return XFS_ERROR(error);
  
  		flags &= ~XFS_QMOPT_SBVERSION;
  	}

  	if (XFS_IS_OQUOTA_ON(mp) && gip == NULL) {
  		flags |= (XFS_IS_GQUOTA_ON(mp) ?
  				XFS_QMOPT_GQUOTA : XFS_QMOPT_PQUOTA);
  		error = xfs_qm_qino_alloc(mp, &gip,
  					  sbflags | XFS_SB_GQUOTINO, flags);
  		if (error) {

  			if (uip)

  				IRELE(uip);

  
  			return XFS_ERROR(error);
  		}
  	}

  	mp->m_quotainfo->qi_uquotaip = uip;
  	mp->m_quotainfo->qi_gquotaip = gip;

  	return 0;

  }

  /*

   * Just pop the least recently used dquot off the freelist and
   * recycle it. The returned dquot is locked.

   */

  STATIC xfs_dquot_t *
  xfs_qm_dqreclaim_one(void)

  {

  	xfs_dquot_t	*dqpout;
  	xfs_dquot_t	*dqp;

  	int		restarts;

  	int		startagain;

  	restarts = 0;

  	dqpout = NULL;

  	/* lockorder: hashchainlock, freelistlock, mplistlock, dqlock, dqflock */

  again:
  	startagain = 0;

  	mutex_lock(&xfs_Gqm->qm_dqfrlist_lock);

  	list_for_each_entry(dqp, &xfs_Gqm->qm_dqfrlist, q_freelist) {

  		struct xfs_mount *mp = dqp->q_mount;

  		xfs_dqlock(dqp);
  
  		/*
  		 * We are racing with dqlookup here. Naturally we don't

  		 * want to reclaim a dquot that lookup wants. We release the
  		 * freelist lock and start over, so that lookup will grab
  		 * both the dquot and the freelistlock.

  		 */
  		if (dqp->dq_flags & XFS_DQ_WANT) {

  			ASSERT(! (dqp->dq_flags & XFS_DQ_INACTIVE));
  
  			trace_xfs_dqreclaim_want(dqp);

  			XQM_STATS_INC(xqmstats.xs_qm_dqwants);

  			restarts++;
  			startagain = 1;
  			goto dqunlock;

  		}
  
  		/*
  		 * If the dquot is inactive, we are assured that it is
  		 * not on the mplist or the hashlist, and that makes our
  		 * life easier.
  		 */
  		if (dqp->dq_flags & XFS_DQ_INACTIVE) {

  			ASSERT(mp == NULL);

  			ASSERT(! XFS_DQ_IS_DIRTY(dqp));

  			ASSERT(list_empty(&dqp->q_hashlist));

  			ASSERT(list_empty(&dqp->q_mplist));

  			list_del_init(&dqp->q_freelist);
  			xfs_Gqm->qm_dqfrlist_cnt--;

  			dqpout = dqp;

  			XQM_STATS_INC(xqmstats.xs_qm_dqinact_reclaims);

  			goto dqunlock;

  		}

  		ASSERT(dqp->q_hash);

  		ASSERT(!list_empty(&dqp->q_mplist));

  		/*

  		 * Try to grab the flush lock. If this dquot is in the process
  		 * of getting flushed to disk, we don't want to reclaim it.

  		 */

  		if (!xfs_dqflock_nowait(dqp))
  			goto dqunlock;

  
  		/*
  		 * We have the flush lock so we know that this is not in the
  		 * process of being flushed. So, if this is dirty, flush it
  		 * DELWRI so that we don't get a freelist infested with
  		 * dirty dquots.
  		 */
  		if (XFS_DQ_IS_DIRTY(dqp)) {

  			int	error;

  			trace_xfs_dqreclaim_dirty(dqp);

  			/*
  			 * We flush it delayed write, so don't bother

  			 * releasing the freelist lock.

  			 */

  			error = xfs_qm_dqflush(dqp, 0);

  			if (error) {

  				xfs_warn(mp, "%s: dquot %p flush failed",
  					__func__, dqp);

  			}

  			goto dqunlock;

  		}

  		/*
  		 * We're trying to get the hashlock out of order. This races
  		 * with dqlookup; so, we giveup and goto the next dquot if
  		 * we couldn't get the hashlock. This way, we won't starve
  		 * a dqlookup process that holds the hashlock that is
  		 * waiting for the freelist lock.
  		 */

  		if (!mutex_trylock(&dqp->q_hash->qh_lock)) {

  			restarts++;
  			goto dqfunlock;

  		}

  		/*
  		 * This races with dquot allocation code as well as dqflush_all
  		 * and reclaim code. So, if we failed to grab the mplist lock,
  		 * giveup everything and start over.
  		 */

  		if (!mutex_trylock(&mp->m_quotainfo->qi_dqlist_lock)) {

  			restarts++;

  			startagain = 1;
  			goto qhunlock;

  		}

  		ASSERT(dqp->q_nrefs == 0);

  		list_del_init(&dqp->q_mplist);
  		mp->m_quotainfo->qi_dquots--;
  		mp->m_quotainfo->qi_dqreclaims++;

  		list_del_init(&dqp->q_hashlist);
  		dqp->q_hash->qh_version++;

  		list_del_init(&dqp->q_freelist);
  		xfs_Gqm->qm_dqfrlist_cnt--;

  		dqpout = dqp;
  		mutex_unlock(&mp->m_quotainfo->qi_dqlist_lock);

  qhunlock:

  		mutex_unlock(&dqp->q_hash->qh_lock);
  dqfunlock:
  		xfs_dqfunlock(dqp);

  dqunlock:

  		xfs_dqunlock(dqp);

  		if (dqpout)
  			break;
  		if (restarts >= XFS_QM_RECLAIM_MAX_RESTARTS)

  			break;
  		if (startagain) {
  			mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock);
  			goto again;
  		}

  	}

  	mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock);

  	return dqpout;

  }

  /*
   * Traverse the freelist of dquots and attempt to reclaim a maximum of
   * 'howmany' dquots. This operation races with dqlookup(), and attempts to
   * favor the lookup function ...
   */
  STATIC int
  xfs_qm_shake_freelist(
  	int	howmany)
  {
  	int		nreclaimed = 0;
  	xfs_dquot_t	*dqp;
  
  	if (howmany <= 0)
  		return 0;
  
  	while (nreclaimed < howmany) {
  		dqp = xfs_qm_dqreclaim_one();
  		if (!dqp)
  			return nreclaimed;
  		xfs_qm_dqdestroy(dqp);
  		nreclaimed++;
  	}
  	return nreclaimed;
  }

  
  /*
   * The kmem_shake interface is invoked when memory is running low.
   */
  /* ARGSUSED */
  STATIC int

  xfs_qm_shake(
  	struct shrinker	*shrink,

  	struct shrink_control *sc)

  {
  	int	ndqused, nfree, n;

  	gfp_t gfp_mask = sc->gfp_mask;

  
  	if (!kmem_shake_allow(gfp_mask))

  		return 0;

  	if (!xfs_Gqm)

  		return 0;

  	nfree = xfs_Gqm->qm_dqfrlist_cnt; /* free dquots */

  	/* incore dquots in all f/s's */
  	ndqused = atomic_read(&xfs_Gqm->qm_totaldquots) - nfree;
  
  	ASSERT(ndqused >= 0);
  
  	if (nfree <= ndqused && nfree < ndquot)

  		return 0;