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xfs_qm.c

/*
 * 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_dir2.h"
#include "xfs_alloc.h"
#include "xfs_dmapi.h"
#include "xfs_quota.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_itable.h"
#include "xfs_rtalloc.h"
#include "xfs_error.h"
#include "xfs_bmap.h"
#include "xfs_rw.h"
#include "xfs_attr.h"
#include "xfs_buf_item.h"
#include "xfs_trans_space.h"
#include "xfs_utils.h"
#include "xfs_qm.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 cred_t     xfs_zerocr;

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

STATIC void xfs_qm_freelist_init(xfs_frlist_t *);
STATIC void xfs_qm_freelist_destroy(xfs_frlist_t *);

STATIC int  xfs_qm_init_quotainos(xfs_mount_t *);
STATIC int  xfs_qm_init_quotainfo(xfs_mount_t *);
STATIC int  xfs_qm_shake(int, gfp_t);

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

#ifdef DEBUG
extern struct mutex     qcheck_lock;
#endif

#ifdef QUOTADEBUG
#define XQM_LIST_PRINT(l, NXT, title) \
{ \
      xfs_dquot_t *dqp; int i = 0; \
      cmn_err(CE_DEBUG, "%s (#%d)", title, (int) (l)->qh_nelems); \
      for (dqp = (l)->qh_next; dqp != NULL; dqp = dqp->NXT) { \
            cmn_err(CE_DEBUG, "   %d.  \"%d (%s)\"   " \
                          "bcnt = %d, icnt = %d, refs = %d", \
                  ++i, (int) be32_to_cpu(dqp->q_core.d_id), \
                  DQFLAGTO_TYPESTR(dqp),       \
                  (int) be64_to_cpu(dqp->q_core.d_bcount), \
                  (int) be64_to_cpu(dqp->q_core.d_icount), \
                  (int) dqp->q_nrefs);  } \
}
#else
#define XQM_LIST_PRINT(l, NXT, title) do { } while (0)
#endif

/*
 * 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),
                             KM_SLEEP | KM_MAYFAIL | KM_LARGE);
      gdqhash = kmem_zalloc(hsize, KM_SLEEP | KM_LARGE);
      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
       */
      xfs_qm_freelist_init(&(xqm->qm_dqfreelist));

      /*
       * 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;
#ifdef DEBUG
      mutex_init(&qcheck_lock);
#endif
      return xqm;
}

/*
 * Destroy the global quota manager when its reference count goes to zero.
 */
STATIC void
xfs_qm_destroy(
      struct xfs_qm     *xqm)
{
      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(xqm->qm_usr_dqhtable);
      kmem_free(xqm->qm_grp_dqhtable);
      xqm->qm_usr_dqhtable = NULL;
      xqm->qm_grp_dqhtable = NULL;
      xqm->qm_dqhashmask = 0;
      xfs_qm_freelist_destroy(&(xqm->qm_dqfreelist));
#ifdef DEBUG
      mutex_destroy(&qcheck_lock);
#endif
      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 == NULL)
            xfs_Gqm = xfs_Gqm_init();
      /*
       * 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, *nextdqp;

      ASSERT(xfs_Gqm);
      ASSERT(xfs_Gqm->qm_nrefs > 0);

      /*
       * Go thru the freelist and destroy all inactive dquots.
       */
      xfs_qm_freelist_lock(xfs_Gqm);

      for (dqp = xfs_Gqm->qm_dqfreelist.qh_next;
           dqp != (xfs_dquot_t *)&(xfs_Gqm->qm_dqfreelist); ) {
            xfs_dqlock(dqp);
            nextdqp = dqp->dq_flnext;
            if (dqp->dq_flags & XFS_DQ_INACTIVE) {
                  ASSERT(dqp->q_mount == NULL);
                  ASSERT(! XFS_DQ_IS_DIRTY(dqp));
                  ASSERT(dqp->HL_PREVP == NULL);
                  ASSERT(dqp->MPL_PREVP == NULL);
                  XQM_FREELIST_REMOVE(dqp);
                  xfs_dqunlock(dqp);
                  xfs_qm_dqdestroy(dqp);
            } else {
                  xfs_dqunlock(dqp);
            }
            dqp = nextdqp;
      }
      xfs_qm_freelist_unlock(xfs_Gqm);

      /*
       * 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_QMOPT_UMOUNTING);
            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) {
            cmn_err(CE_NOTE,
                  "Cannot turn on quotas for realtime filesystem %s",
                  mp->m_fsname);
            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_fs_cmn_err(CE_ALERT, mp,
                        "XFS mount_quotas: Superblock update failed!");
            }
      }

      if (error) {
            xfs_fs_cmn_err(CE_WARN, mp,
                  "Failed to initialize disk quotas.");
            return;
      }

#ifdef QUOTADEBUG
      if (XFS_IS_QUOTA_ON(mp))
            xfs_qm_internalqcheck(mp);
#endif
}

/*
 * 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(
      xfs_mount_t *mp,
      int         flags)
{
      int         recl;
      xfs_dquot_t *dqp;
      int         niters;
      int         error;

      if (mp->m_quotainfo == NULL)
            return 0;
      niters = 0;
again:
      xfs_qm_mplist_lock(mp);
      FOREACH_DQUOT_IN_MP(dqp, mp) {
            xfs_dqlock(dqp);
            if (! XFS_DQ_IS_DIRTY(dqp)) {
                  xfs_dqunlock(dqp);
                  continue;
            }
            xfs_dqtrace_entry(dqp, "FLUSHALL: DQDIRTY");
            /* XXX a sentinel would be better */
            recl = XFS_QI_MPLRECLAIMS(mp);
            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.
             */
            xfs_qm_mplist_unlock(mp);
            error = xfs_qm_dqflush(dqp, flags);
            xfs_dqunlock(dqp);
            if (error)
                  return error;

            xfs_qm_mplist_lock(mp);
            if (recl != XFS_QI_MPLRECLAIMS(mp)) {
                  xfs_qm_mplist_unlock(mp);
                  /* XXX restart limit */
                  goto again;
            }
      }

      xfs_qm_mplist_unlock(mp);
      /* 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(
      xfs_mount_t *mp)
{
      xfs_dquot_t *dqp, *gdqp;
      int         nrecl;

 again:
      ASSERT(XFS_QM_IS_MPLIST_LOCKED(mp));
      dqp = XFS_QI_MPLNEXT(mp);
      while (dqp) {
            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 = XFS_QI_MPLRECLAIMS(mp);
                  xfs_qm_mplist_unlock(mp);
                  xfs_qm_dqput(gdqp);

                  xfs_qm_mplist_lock(mp);
                  if (nrecl != XFS_QI_MPLRECLAIMS(mp))
                        goto again;
            }
            dqp = dqp->MPL_NEXT;
      }
}

/*
 * 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(
      xfs_mount_t *mp,
      uint        flags) /* QUOTAOFF/UMOUNTING/UQUOTA/PQUOTA/GQUOTA */
{
      xfs_dquot_t *dqp;
      uint        dqtype;
      int         nrecl;
      xfs_dquot_t *nextdqp;
      int         nmisses;

      if (mp->m_quotainfo == NULL)
            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;

      xfs_qm_mplist_lock(mp);

      /*
       * 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(XFS_QM_IS_MPLIST_LOCKED(mp));
      /*
       * 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.
       */
      dqp = XFS_QI_MPLNEXT(mp);
      while (dqp) {
            /*
             * 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) {
                  dqp = dqp->MPL_NEXT;
                  continue;
            }

            if (!mutex_trylock(&dqp->q_hash->qh_lock)) {
                  nrecl = XFS_QI_MPLRECLAIMS(mp);
                  xfs_qm_mplist_unlock(mp);
                  mutex_lock(&dqp->q_hash->qh_lock);
                  xfs_qm_mplist_lock(mp);

                  /*
                   * 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 != XFS_QI_MPLRECLAIMS(mp)) {
                        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.
             */
            nextdqp = dqp->MPL_NEXT;
            nmisses += xfs_qm_dqpurge(dqp);
            dqp = nextdqp;
      }
      xfs_qm_mplist_unlock(mp);
      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) {
            xfs_dqtrace_entry(dqp, "DQATTACH: found in ip");
            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;

      xfs_dqtrace_entry(dqp, "DQATTACH: found by dqget");

      /*
       * 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, ip->i_d.di_projid, 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 QUOTADEBUG
      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;

      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_dqtrace_entry_ino(ip->i_udquot, "DQDETTACH", ip);
            xfs_qm_dqrele(ip->i_udquot);
            ip->i_udquot = NULL;
      }
      if (ip->i_gdquot) {
            xfs_dqtrace_entry_ino(ip->i_gdquot, "DQDETTACH", ip);
            xfs_qm_dqrele(ip->i_gdquot);
            ip->i_gdquot = NULL;
      }
}

int
xfs_qm_sync(
      xfs_mount_t *mp,
      int         flags)
{
      int         recl, restarts;
      xfs_dquot_t *dqp;
      uint        flush_flags;
      int         error;

      if (!XFS_IS_QUOTA_RUNNING(mp) || !XFS_IS_QUOTA_ON(mp))
            return 0;

      flush_flags = (flags & SYNC_WAIT) ? XFS_QMOPT_SYNC : XFS_QMOPT_DELWRI;
      restarts = 0;

  again:
      xfs_qm_mplist_lock(mp);
      /*
       * 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)) {
            xfs_qm_mplist_unlock(mp);
            return 0;
      }
      FOREACH_DQUOT_IN_MP(dqp, mp) {
            /*
             * 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 = XFS_QI_MPLRECLAIMS(mp);
            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
             */
            xfs_qm_mplist_unlock(mp);
            xfs_dqtrace_entry(dqp, "XQM_SYNC: DQFLUSH");
            error = xfs_qm_dqflush(dqp, flush_flags);
            xfs_dqunlock(dqp);
            if (error && XFS_FORCED_SHUTDOWN(mp))
                  return 0;   /* Need to prevent umount failure */
            else if (error)
                  return error;

            xfs_qm_mplist_lock(mp);
            if (recl != XFS_QI_MPLRECLAIMS(mp)) {
                  if (++restarts >= XFS_QM_SYNC_MAX_RESTARTS)
                        break;

                  xfs_qm_mplist_unlock(mp);
                  goto again;
            }
      }

      xfs_qm_mplist_unlock(mp);
      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;
      }

      xfs_qm_list_init(&qinf->qi_dqlist, "mpdqlist", 0);
      lockdep_set_class(&qinf->qi_dqlist.qh_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);

      xfs_qm_list_destroy(&qi->qi_dqlist);

      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);
      list->qh_next = NULL;
      list->qh_version = 0;
      list->qh_nelems = 0;
}

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


/*
 * Stripped down version of dqattach. This doesn't attach, or even look at the
 * dquots attached to the inode. The rationale is that there won't be any
 * attached at the time this is called from quotacheck.
 */
STATIC int
xfs_qm_dqget_noattach(
      xfs_inode_t *ip,
      xfs_dquot_t **O_udqpp,
      xfs_dquot_t **O_gdqpp)
{
      int         error;
      xfs_mount_t *mp;
      xfs_dquot_t *udqp, *gdqp;

      ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
      mp = ip->i_mount;
      udqp = NULL;
      gdqp = NULL;

      if (XFS_IS_UQUOTA_ON(mp)) {
            ASSERT(ip->i_udquot == NULL);
            /*
             * We want the dquot allocated if it doesn't exist.
             */
            if ((error = xfs_qm_dqget(mp, ip, ip->i_d.di_uid, XFS_DQ_USER,
                               XFS_QMOPT_DQALLOC | XFS_QMOPT_DOWARN,
                               &udqp))) {
                  /*
                   * Shouldn't be able to turn off quotas here.
                   */
                  ASSERT(error != ESRCH);
                  ASSERT(error != ENOENT);
                  return error;
            }
            ASSERT(udqp);
      }

      if (XFS_IS_OQUOTA_ON(mp)) {
            ASSERT(ip->i_gdquot == NULL);
            if (udqp)
                  xfs_dqunlock(udqp);
            error = XFS_IS_GQUOTA_ON(mp) ?
                        xfs_qm_dqget(mp, ip,
                                   ip->i_d.di_gid, XFS_DQ_GROUP,
                                   XFS_QMOPT_DQALLOC|XFS_QMOPT_DOWARN,
                                   &gdqp) :
                        xfs_qm_dqget(mp, ip,
                                   ip->i_d.di_projid, XFS_DQ_PROJ,
                                   XFS_QMOPT_DQALLOC|XFS_QMOPT_DOWARN,
                                   &gdqp);
            if (error) {
                  if (udqp)
                        xfs_qm_dqrele(udqp);
                  ASSERT(error != ESRCH);
                  ASSERT(error != ENOENT);
                  return error;
            }
            ASSERT(gdqp);

            /* Reacquire the locks in the right order */
            if (udqp) {
                  if (! xfs_qm_dqlock_nowait(udqp)) {
                        xfs_dqunlock(gdqp);
                        xfs_dqlock(udqp);
                        xfs_dqlock(gdqp);
                  }
            }
      }

      *O_udqpp = udqp;
      *O_gdqpp = gdqp;

#ifdef QUOTADEBUG
      if (udqp) ASSERT(XFS_DQ_IS_LOCKED(udqp));
      if (gdqp) ASSERT(XFS_DQ_IS_LOCKED(gdqp));
#endif
      return 0;
}

/*
 * 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;
      }

      if ((error = xfs_dir_ialloc(&tp, NULL, S_IFREG, 1, 0,
                           &xfs_zerocr, 0, 1, ip, &committed))) {
            xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES |
                         XFS_TRANS_ABORT);
            return error;
      }

      /*
       * Keep an extra reference to this quota inode. This inode is
       * locked exclusively and joined to the transaction already.
       */
      ASSERT(xfs_isilocked(*ip, XFS_ILOCK_EXCL));
      IHOLD(*ip);

      /*
       * 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) {
#if defined(DEBUG) && defined(XFS_LOUD_RECOVERY)
            unsigned oldv = mp->m_sb.sb_versionnum;
#endif
            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 defined(DEBUG) && defined(XFS_LOUD_RECOVERY)
            cmn_err(CE_NOTE,
                  "Old superblock version %x, converting to %x.",
                  oldv, mp->m_sb.sb_versionnum);
#endif
      }
      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_fs_cmn_err(CE_ALERT, mp, "XFS qino_alloc failed!");
            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;

      xfs_buftrace("RESET DQUOTS", bp);
      /*
       * 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(XFS_QM_DQPERBLK(mp) == j);
#endif
      ddq = (xfs_disk_dquot_t *)XFS_BUF_PTR(bp);
      for (j = 0; j < XFS_QM_DQPERBLK(mp); 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(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         notcommitted;
      int         incr;
      int         type;

      ASSERT(blkcnt > 0);
      notcommitted = 0;
      incr = (blkcnt > XFS_QM_MAX_DQCLUSTER_LOGSZ) ?
            XFS_QM_MAX_DQCLUSTER_LOGSZ : blkcnt;
      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),
                        (int)XFS_QI_DQCHUNKLEN(mp), 0, &bp);
            if (error)
                  break;

            xfs_qm_reset_dqcounts(mp, bp, firstid, type);
            xfs_bdwrite(mp, bp);
            /*
             * goto the next block.
             */
            bno++;
            firstid += XFS_QM_DQPERBLK(mp);
      }
      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, 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 *
                        XFS_QM_DQPERBLK(mp);
                  /*
                   * 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_baread(mp->m_ddev_targp,
                                     XFS_FSB_TO_DADDR(mp, rablkno),
                                     (int)XFS_QI_DQCHUNKLEN(mp));
                              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 (either USR or GRP, doesn't matter),
 * this updates its incore copy 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 void
xfs_qm_quotacheck_dqadjust(
      xfs_dquot_t       *dqp,
      xfs_qcnt_t        nblks,
      xfs_qcnt_t        rtblks)
{
      ASSERT(XFS_DQ_IS_LOCKED(dqp));
      xfs_dqtrace_entry(dqp, "QCHECK DQADJUST");
      /*
       * 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)
       */
      if (! XFS_IS_SUSER_DQUOT(dqp)) {
            xfs_qm_adjust_dqlimits(dqp->q_mount, &dqp->q_core);
            xfs_qm_adjust_dqtimers(dqp->q_mount, &dqp->q_core);
      }

      dqp->dq_flags |= XFS_DQ_DIRTY;
}

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 */
      void        *private_data,    /* not used */
      xfs_daddr_t bno,        /* starting block of inode cluster */
      int         *ubused,    /* not used */
      void        *dip,       /* on-disk inode pointer (not used) */
      int         *res)       /* result code value */
{
      xfs_inode_t *ip;
      xfs_dquot_t *udqp, *gdqp;
      xfs_qcnt_t  nblks, rtblks;
      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.
       */
      if ((error = xfs_iget(mp, NULL, ino, 0, XFS_ILOCK_EXCL, &ip, bno))) {
            *res = BULKSTAT_RV_NOTHING;
            return error;
      }

      /*
       * Obtain the locked dquots. In case of an error (eg. allocation
       * fails for ENOSPC), we return the negative of the error number
       * to bulkstat, so that it can get propagated to quotacheck() and
       * making us disable quotas for the file system.
       */
      if ((error = xfs_qm_dqget_noattach(ip, &udqp, &gdqp))) {
            xfs_iput(ip, XFS_ILOCK_EXCL);
            *res = BULKSTAT_RV_GIVEUP;
            return error;
      }

      rtblks = 0;
      if (! XFS_IS_REALTIME_INODE(ip)) {
            nblks = (xfs_qcnt_t)ip->i_d.di_nblocks;
      } else {
            /*
             * Walk thru the extent list and count the realtime blocks.
             */
            if ((error = xfs_qm_get_rtblks(ip, &rtblks))) {
                  xfs_iput(ip, XFS_ILOCK_EXCL);
                  if (udqp)
                        xfs_qm_dqput(udqp);
                  if (gdqp)
                        xfs_qm_dqput(gdqp);
                  *res = BULKSTAT_RV_GIVEUP;
                  return error;
            }
            nblks = (xfs_qcnt_t)ip->i_d.di_nblocks - rtblks;
      }
      ASSERT(ip->i_delayed_blks == 0);

      /*
       * We can't release the inode while holding its dquot locks.
       * The inode can go into inactive and might try to acquire the dquotlocks.
       * So, just unlock here and do a vn_rele at the end.
       */
      xfs_iunlock(ip, XFS_ILOCK_EXCL);

      /*
       * 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)) {
            ASSERT(udqp);
            xfs_qm_quotacheck_dqadjust(udqp, nblks, rtblks);
            xfs_qm_dqput(udqp);
      }
      if (XFS_IS_OQUOTA_ON(mp)) {
            ASSERT(gdqp);
            xfs_qm_quotacheck_dqadjust(gdqp, nblks, rtblks);
            xfs_qm_dqput(gdqp);
      }
      /*
       * Now release the inode. This will send it to 'inactive', and
       * possibly even free blocks.
       */
      IRELE(ip);

      /*
       * Goto next inode.
       */
      *res = BULKSTAT_RV_DIDONE;
      return 0;
}

/*
 * 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(XFS_QI_UQIP(mp) || XFS_QI_GQIP(mp));
      ASSERT(XFS_IS_QUOTA_RUNNING(mp));

      /*
       * There should be no cached dquots. The (simplistic) quotacheck
       * algorithm doesn't like that.
       */
      ASSERT(XFS_QI_MPLNDQUOTS(mp) == 0);

      cmn_err(CE_NOTE, "XFS quotacheck %s: Please wait.", mp->m_fsname);

      /*
       * 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.
       */
      if ((uip = XFS_QI_UQIP(mp))) {
            if ((error = xfs_qm_dqiterate(mp, uip, XFS_QMOPT_UQUOTA)))
                  goto error_return;
            flags |= XFS_UQUOTA_CHKD;
      }

      if ((gip = XFS_QI_GQIP(mp))) {
            if ((error = xfs_qm_dqiterate(mp, gip, XFS_IS_GQUOTA_ON(mp) ?
                              XFS_QMOPT_GQUOTA : XFS_QMOPT_PQUOTA)))
                  goto error_return;
            flags |= XFS_OQUOTA_CHKD;
      }

      do {
            /*
             * Iterate thru all the inodes in the file system,
             * adjusting the corresponding dquot counters in core.
             */
            if ((error = xfs_bulkstat(mp, &lastino, &count,
                             xfs_qm_dqusage_adjust, NULL,
                             structsz, NULL, BULKSTAT_FG_IGET, &done)))
                  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, XFS_QMOPT_DELWRI);

      /*
       * 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 | XFS_QMOPT_QUOTAOFF);
            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;

      XQM_LIST_PRINT(&(XFS_QI_MPL_LIST(mp)), MPL_NEXT, "++++ Mp list +++");

 error_return:
      if (error) {
            cmn_err(CE_WARN, "XFS quotacheck %s: Unsuccessful (Error %d): "
                  "Disabling quotas.",
                  mp->m_fsname, 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)) {
                  cmn_err(CE_WARN, "XFS quotacheck %s: "
                        "Failed to reset quota flags.", mp->m_fsname);
            }
      } else {
            cmn_err(CE_NOTE, "XFS quotacheck %s: Done.", mp->m_fsname);
      }
      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, 0)))
                        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, 0))) {
                        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);
            }
      }

      XFS_QI_UQIP(mp) = uip;
      XFS_QI_GQIP(mp) = gip;

      return 0;
}


/*
 * 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 ...
 * XXXsup merge this with qm_reclaim_one().
 */
STATIC int
xfs_qm_shake_freelist(
      int howmany)
{
      int         nreclaimed;
      xfs_dqhash_t      *hash;
      xfs_dquot_t *dqp, *nextdqp;
      int         restarts;
      int         nflushes;

      if (howmany <= 0)
            return 0;

      nreclaimed = 0;
      restarts = 0;
      nflushes = 0;

#ifdef QUOTADEBUG
      cmn_err(CE_DEBUG, "Shake free 0x%x", howmany);
#endif
      /* lock order is : hashchainlock, freelistlock, mplistlock */
 tryagain:
      xfs_qm_freelist_lock(xfs_Gqm);

      for (dqp = xfs_Gqm->qm_dqfreelist.qh_next;
           ((dqp != (xfs_dquot_t *) &xfs_Gqm->qm_dqfreelist) &&
            nreclaimed < howmany); ) {
            xfs_dqlock(dqp);

            /*
             * We are racing with dqlookup here. Naturally we don't
             * want to reclaim a dquot that lookup wants.
             */
            if (dqp->dq_flags & XFS_DQ_WANT) {
                  xfs_dqunlock(dqp);
                  xfs_qm_freelist_unlock(xfs_Gqm);
                  if (++restarts >= XFS_QM_RECLAIM_MAX_RESTARTS)
                        return nreclaimed;
                  XQM_STATS_INC(xqmstats.xs_qm_dqwants);
                  goto tryagain;
            }

            /*
             * 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(dqp->q_mount == NULL);
                  ASSERT(! XFS_DQ_IS_DIRTY(dqp));
                  ASSERT(dqp->HL_PREVP == NULL);
                  ASSERT(dqp->MPL_PREVP == NULL);
                  XQM_STATS_INC(xqmstats.xs_qm_dqinact_reclaims);
                  nextdqp = dqp->dq_flnext;
                  goto off_freelist;
            }

            ASSERT(dqp->MPL_PREVP);
            /*
             * 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)) {
                  xfs_dqunlock(dqp);
                  dqp = dqp->dq_flnext;
                  continue;
            }

            /*
             * 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;
                  xfs_dqtrace_entry(dqp, "DQSHAKE: DQDIRTY");
                  /*
                   * We flush it delayed write, so don't bother
                   * releasing the mplock.
                   */
                  error = xfs_qm_dqflush(dqp, XFS_QMOPT_DELWRI);
                  if (error) {
                        xfs_fs_cmn_err(CE_WARN, dqp->q_mount,
                  "xfs_qm_dqflush_all: dquot %p flush failed", dqp);
                  }
                  xfs_dqunlock(dqp); /* dqflush unlocks dqflock */
                  dqp = dqp->dq_flnext;
                  continue;
            }
            /*
             * 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)) {
                  xfs_dqfunlock(dqp);
                  xfs_dqunlock(dqp);
                  dqp = dqp->dq_flnext;
                  continue;
            }
            /*
             * 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.
             */
            hash = dqp->q_hash;
            ASSERT(hash);
            if (! xfs_qm_mplist_nowait(dqp->q_mount)) {
                  /* XXX put a sentinel so that we can come back here */
                  xfs_dqfunlock(dqp);
                  xfs_dqunlock(dqp);
                  mutex_unlock(&hash->qh_lock);
                  xfs_qm_freelist_unlock(xfs_Gqm);
                  if (++restarts >= XFS_QM_RECLAIM_MAX_RESTARTS)
                        return nreclaimed;
                  goto tryagain;
            }
            xfs_dqtrace_entry(dqp, "DQSHAKE: UNLINKING");
#ifdef QUOTADEBUG
            cmn_err(CE_DEBUG, "Shake 0x%p, ID 0x%x\n",
                  dqp, be32_to_cpu(dqp->q_core.d_id));
#endif
            ASSERT(dqp->q_nrefs == 0);
            nextdqp = dqp->dq_flnext;
            XQM_MPLIST_REMOVE(&(XFS_QI_MPL_LIST(dqp->q_mount)), dqp);
            XQM_HASHLIST_REMOVE(hash, dqp);
            xfs_dqfunlock(dqp);
            xfs_qm_mplist_unlock(dqp->q_mount);
            mutex_unlock(&hash->qh_lock);

 off_freelist:
            XQM_FREELIST_REMOVE(dqp);
            xfs_dqunlock(dqp);
            nreclaimed++;
            XQM_STATS_INC(xqmstats.xs_qm_dqshake_reclaims);
            xfs_qm_dqdestroy(dqp);
            dqp = nextdqp;
      }
      xfs_qm_freelist_unlock(xfs_Gqm);
      return nreclaimed;
}


/*
 * The kmem_shake interface is invoked when memory is running low.
 */
/* ARGSUSED */
STATIC int
xfs_qm_shake(int nr_to_scan, gfp_t gfp_mask)
{
      int   ndqused, nfree, n;

      if (!kmem_shake_allow(gfp_mask))
            return 0;
      if (!xfs_Gqm)
            return 0;

      nfree = xfs_Gqm->qm_dqfreelist.qh_nelems; /* 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;

      ndqused *= xfs_Gqm->qm_dqfree_ratio;      /* target # of free dquots */
      n = nfree - ndqused - ndquot;       /* # over target */

      return xfs_qm_shake_freelist(MAX(nfree, n));
}


/*
 * 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         nflushes;

      restarts = 0;
      dqpout = NULL;
      nflushes = 0;

      /* lockorder: hashchainlock, freelistlock, mplistlock, dqlock, dqflock */
 startagain:
      xfs_qm_freelist_lock(xfs_Gqm);

      FOREACH_DQUOT_IN_FREELIST(dqp, &(xfs_Gqm->qm_dqfreelist)) {
            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));
                  xfs_dqtrace_entry(dqp, "DQRECLAIM: DQWANT");
                  xfs_dqunlock(dqp);
                  xfs_qm_freelist_unlock(xfs_Gqm);
                  if (++restarts >= XFS_QM_RECLAIM_MAX_RESTARTS)
                        return NULL;
                  XQM_STATS_INC(xqmstats.xs_qm_dqwants);
                  goto startagain;
            }

            /*
             * 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(dqp->q_mount == NULL);
                  ASSERT(! XFS_DQ_IS_DIRTY(dqp));
                  ASSERT(dqp->HL_PREVP == NULL);
                  ASSERT(dqp->MPL_PREVP == NULL);
                  XQM_FREELIST_REMOVE(dqp);
                  xfs_dqunlock(dqp);
                  dqpout = dqp;
                  XQM_STATS_INC(xqmstats.xs_qm_dqinact_reclaims);
                  break;
            }

            ASSERT(dqp->q_hash);
            ASSERT(dqp->MPL_PREVP);

            /*
             * 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)) {
                  xfs_dqunlock(dqp);
                  continue;
            }

            /*
             * 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;
                  xfs_dqtrace_entry(dqp, "DQRECLAIM: DQDIRTY");
                  /*
                   * We flush it delayed write, so don't bother
                   * releasing the freelist lock.
                   */
                  error = xfs_qm_dqflush(dqp, XFS_QMOPT_DELWRI);
                  if (error) {
                        xfs_fs_cmn_err(CE_WARN, dqp->q_mount,
                  "xfs_qm_dqreclaim: dquot %p flush failed", dqp);
                  }
                  xfs_dqunlock(dqp); /* dqflush unlocks dqflock */
                  continue;
            }

            if (! xfs_qm_mplist_nowait(dqp->q_mount)) {
                  xfs_dqfunlock(dqp);
                  xfs_dqunlock(dqp);
                  continue;
            }

            if (!mutex_trylock(&dqp->q_hash->qh_lock))
                  goto mplistunlock;

            ASSERT(dqp->q_nrefs == 0);
            xfs_dqtrace_entry(dqp, "DQRECLAIM: UNLINKING");
            XQM_MPLIST_REMOVE(&(XFS_QI_MPL_LIST(dqp->q_mount)), dqp);
            XQM_HASHLIST_REMOVE(dqp->q_hash, dqp);
            XQM_FREELIST_REMOVE(dqp);
            dqpout = dqp;
            mutex_unlock(&dqp->q_hash->qh_lock);
 mplistunlock:
            xfs_qm_mplist_unlock(dqp->q_mount);
            xfs_dqfunlock(dqp);
            xfs_dqunlock(dqp);
            if (dqpout)
                  break;
      }

      xfs_qm_freelist_unlock(xfs_Gqm);
      return dqpout;
}


/*------------------------------------------------------------------*/

/*
 * Return a new incore dquot. Depending on the number of
 * dquots in the system, we either allocate a new one on the kernel heap,
 * or reclaim a free one.
 * Return value is B_TRUE if we allocated a new dquot, B_FALSE if we managed
 * to reclaim an existing one from the freelist.
 */
boolean_t
xfs_qm_dqalloc_incore(
      xfs_dquot_t **O_dqpp)
{
      xfs_dquot_t *dqp;

      /*
       * Check against high water mark to see if we want to pop
       * a nincompoop dquot off the freelist.
       */
      if (atomic_read(&xfs_Gqm->qm_totaldquots) >= ndquot) {
            /*
             * Try to recycle a dquot from the freelist.
             */
            if ((dqp = xfs_qm_dqreclaim_one())) {
                  XQM_STATS_INC(xqmstats.xs_qm_dqreclaims);
                  /*
                   * Just zero the core here. The rest will get
                   * reinitialized by caller. XXX we shouldn't even
                   * do this zero ...
                   */
                  memset(&dqp->q_core, 0, sizeof(dqp->q_core));
                  *O_dqpp = dqp;
                  return B_FALSE;
            }
            XQM_STATS_INC(xqmstats.xs_qm_dqreclaim_misses);
      }

      /*
       * Allocate a brand new dquot on the kernel heap and return it
       * to the caller to initialize.
       */
      ASSERT(xfs_Gqm->qm_dqzone != NULL);
      *O_dqpp = kmem_zone_zalloc(xfs_Gqm->qm_dqzone, KM_SLEEP);
      atomic_inc(&xfs_Gqm->qm_totaldquots);

      return B_TRUE;
}


/*
 * Start a transaction and write the incore superblock changes to
 * disk. flags parameter indicates which fields have changed.
 */
int
xfs_qm_write_sb_changes(
      xfs_mount_t *mp,
      __int64_t   flags)
{
      xfs_trans_t *tp;
      int         error;

#ifdef QUOTADEBUG
      cmn_err(CE_NOTE, "Writing superblock quota changes :%s", mp->m_fsname);
#endif
      tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SBCHANGE);
      if ((error = xfs_trans_reserve(tp, 0,
                              mp->m_sb.sb_sectsize + 128, 0,
                              0,
                              XFS_DEFAULT_LOG_COUNT))) {
            xfs_trans_cancel(tp, 0);
            return error;
      }

      xfs_mod_sb(tp, flags);
      error = xfs_trans_commit(tp, 0);

      return error;
}


/* --------------- utility functions for vnodeops ---------------- */


/*
 * Given an inode, a uid and gid (from cred_t) make sure that we have
 * allocated relevant dquot(s) on disk, and that we won't exceed inode
 * quotas by creating this file.
 * This also attaches dquot(s) to the given inode after locking it,
 * and returns the dquots corresponding to the uid and/or gid.
 *
 * in : inode (unlocked)
 * out      : udquot, gdquot with references taken and unlocked
 */
int
xfs_qm_vop_dqalloc(
      struct xfs_inode  *ip,
      uid_t             uid,
      gid_t             gid,
      prid_t                  prid,
      uint              flags,
      struct xfs_dquot  **O_udqpp,
      struct xfs_dquot  **O_gdqpp)
{
      struct xfs_mount  *mp = ip->i_mount;
      struct xfs_dquot  *uq, *gq;
      int               error;
      uint              lockflags;

      if (!XFS_IS_QUOTA_RUNNING(mp) || !XFS_IS_QUOTA_ON(mp))
            return 0;

      lockflags = XFS_ILOCK_EXCL;
      xfs_ilock(ip, lockflags);

      if ((flags & XFS_QMOPT_INHERIT) && XFS_INHERIT_GID(ip))
            gid = ip->i_d.di_gid;

      /*
       * Attach the dquot(s) to this inode, doing a dquot allocation
       * if necessary. The dquot(s) will not be locked.
       */
      if (XFS_NOT_DQATTACHED(mp, ip)) {
            error = xfs_qm_dqattach_locked(ip, XFS_QMOPT_DQALLOC);
            if (error) {
                  xfs_iunlock(ip, lockflags);
                  return error;
            }
      }

      uq = gq = NULL;
      if ((flags & XFS_QMOPT_UQUOTA) && XFS_IS_UQUOTA_ON(mp)) {
            if (ip->i_d.di_uid != uid) {
                  /*
                   * What we need is the dquot that has this uid, and
                   * if we send the inode to dqget, the uid of the inode
                   * takes priority over what's sent in the uid argument.
                   * We must unlock inode here before calling dqget if
                   * we're not sending the inode, because otherwise
                   * we'll deadlock by doing trans_reserve while
                   * holding ilock.
                   */
                  xfs_iunlock(ip, lockflags);
                  if ((error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t) uid,
                                     XFS_DQ_USER,
                                     XFS_QMOPT_DQALLOC |
                                     XFS_QMOPT_DOWARN,
                                     &uq))) {
                        ASSERT(error != ENOENT);
                        return error;
                  }
                  /*
                   * Get the ilock in the right order.
                   */
                  xfs_dqunlock(uq);
                  lockflags = XFS_ILOCK_SHARED;
                  xfs_ilock(ip, lockflags);
            } else {
                  /*
                   * Take an extra reference, because we'll return
                   * this to caller
                   */
                  ASSERT(ip->i_udquot);
                  uq = ip->i_udquot;
                  xfs_dqlock(uq);
                  XFS_DQHOLD(uq);
                  xfs_dqunlock(uq);
            }
      }
      if ((flags & XFS_QMOPT_GQUOTA) && XFS_IS_GQUOTA_ON(mp)) {
            if (ip->i_d.di_gid != gid) {
                  xfs_iunlock(ip, lockflags);
                  if ((error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t)gid,
                                     XFS_DQ_GROUP,
                                     XFS_QMOPT_DQALLOC |
                                     XFS_QMOPT_DOWARN,
                                     &gq))) {
                        if (uq)
                              xfs_qm_dqrele(uq);
                        ASSERT(error != ENOENT);
                        return error;
                  }
                  xfs_dqunlock(gq);
                  lockflags = XFS_ILOCK_SHARED;
                  xfs_ilock(ip, lockflags);
            } else {
                  ASSERT(ip->i_gdquot);
                  gq = ip->i_gdquot;
                  xfs_dqlock(gq);
                  XFS_DQHOLD(gq);
                  xfs_dqunlock(gq);
            }
      } else if ((flags & XFS_QMOPT_PQUOTA) && XFS_IS_PQUOTA_ON(mp)) {
            if (ip->i_d.di_projid != prid) {
                  xfs_iunlock(ip, lockflags);
                  if ((error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t)prid,
                                     XFS_DQ_PROJ,
                                     XFS_QMOPT_DQALLOC |
                                     XFS_QMOPT_DOWARN,
                                     &gq))) {
                        if (uq)
                              xfs_qm_dqrele(uq);
                        ASSERT(error != ENOENT);
                        return (error);
                  }
                  xfs_dqunlock(gq);
                  lockflags = XFS_ILOCK_SHARED;
                  xfs_ilock(ip, lockflags);
            } else {
                  ASSERT(ip->i_gdquot);
                  gq = ip->i_gdquot;
                  xfs_dqlock(gq);
                  XFS_DQHOLD(gq);
                  xfs_dqunlock(gq);
            }
      }
      if (uq)
            xfs_dqtrace_entry_ino(uq, "DQALLOC", ip);

      xfs_iunlock(ip, lockflags);
      if (O_udqpp)
            *O_udqpp = uq;
      else if (uq)
            xfs_qm_dqrele(uq);
      if (O_gdqpp)
            *O_gdqpp = gq;
      else if (gq)
            xfs_qm_dqrele(gq);
      return 0;
}

/*
 * Actually transfer ownership, and do dquot modifications.
 * These were already reserved.
 */
xfs_dquot_t *
xfs_qm_vop_chown(
      xfs_trans_t *tp,
      xfs_inode_t *ip,
      xfs_dquot_t **IO_olddq,
      xfs_dquot_t *newdq)
{
      xfs_dquot_t *prevdq;
      uint        bfield = XFS_IS_REALTIME_INODE(ip) ?
                         XFS_TRANS_DQ_RTBCOUNT : XFS_TRANS_DQ_BCOUNT;


      ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
      ASSERT(XFS_IS_QUOTA_RUNNING(ip->i_mount));

      /* old dquot */
      prevdq = *IO_olddq;
      ASSERT(prevdq);
      ASSERT(prevdq != newdq);

      xfs_trans_mod_dquot(tp, prevdq, bfield, -(ip->i_d.di_nblocks));
      xfs_trans_mod_dquot(tp, prevdq, XFS_TRANS_DQ_ICOUNT, -1);

      /* the sparkling new dquot */
      xfs_trans_mod_dquot(tp, newdq, bfield, ip->i_d.di_nblocks);
      xfs_trans_mod_dquot(tp, newdq, XFS_TRANS_DQ_ICOUNT, 1);

      /*
       * Take an extra reference, because the inode
       * is going to keep this dquot pointer even
       * after the trans_commit.
       */
      xfs_dqlock(newdq);
      XFS_DQHOLD(newdq);
      xfs_dqunlock(newdq);
      *IO_olddq = newdq;

      return prevdq;
}

/*
 * Quota reservations for setattr(AT_UID|AT_GID|AT_PROJID).
 */
int
xfs_qm_vop_chown_reserve(
      xfs_trans_t *tp,
      xfs_inode_t *ip,
      xfs_dquot_t *udqp,
      xfs_dquot_t *gdqp,
      uint        flags)
{
      xfs_mount_t *mp = ip->i_mount;
      uint        delblks, blkflags, prjflags = 0;
      xfs_dquot_t *unresudq, *unresgdq, *delblksudq, *delblksgdq;
      int         error;


      ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
      ASSERT(XFS_IS_QUOTA_RUNNING(mp));

      delblks = ip->i_delayed_blks;
      delblksudq = delblksgdq = unresudq = unresgdq = NULL;
      blkflags = XFS_IS_REALTIME_INODE(ip) ?
                  XFS_QMOPT_RES_RTBLKS : XFS_QMOPT_RES_REGBLKS;

      if (XFS_IS_UQUOTA_ON(mp) && udqp &&
          ip->i_d.di_uid != (uid_t)be32_to_cpu(udqp->q_core.d_id)) {
            delblksudq = udqp;
            /*
             * If there are delayed allocation blocks, then we have to
             * unreserve those from the old dquot, and add them to the
             * new dquot.
             */
            if (delblks) {
                  ASSERT(ip->i_udquot);
                  unresudq = ip->i_udquot;
            }
      }
      if (XFS_IS_OQUOTA_ON(ip->i_mount) && gdqp) {
            if (XFS_IS_PQUOTA_ON(ip->i_mount) &&
                 ip->i_d.di_projid != be32_to_cpu(gdqp->q_core.d_id))
                  prjflags = XFS_QMOPT_ENOSPC;

            if (prjflags ||
                (XFS_IS_GQUOTA_ON(ip->i_mount) &&
                 ip->i_d.di_gid != be32_to_cpu(gdqp->q_core.d_id))) {
                  delblksgdq = gdqp;
                  if (delblks) {
                        ASSERT(ip->i_gdquot);
                        unresgdq = ip->i_gdquot;
                  }
            }
      }

      if ((error = xfs_trans_reserve_quota_bydquots(tp, ip->i_mount,
                        delblksudq, delblksgdq, ip->i_d.di_nblocks, 1,
                        flags | blkflags | prjflags)))
            return (error);

      /*
       * Do the delayed blks reservations/unreservations now. Since, these
       * are done without the help of a transaction, if a reservation fails
       * its previous reservations won't be automatically undone by trans
       * code. So, we have to do it manually here.
       */
      if (delblks) {
            /*
             * Do the reservations first. Unreservation can't fail.
             */
            ASSERT(delblksudq || delblksgdq);
            ASSERT(unresudq || unresgdq);
            if ((error = xfs_trans_reserve_quota_bydquots(NULL, ip->i_mount,
                        delblksudq, delblksgdq, (xfs_qcnt_t)delblks, 0,
                        flags | blkflags | prjflags)))
                  return (error);
            xfs_trans_reserve_quota_bydquots(NULL, ip->i_mount,
                        unresudq, unresgdq, -((xfs_qcnt_t)delblks), 0,
                        blkflags);
      }

      return (0);
}

int
xfs_qm_vop_rename_dqattach(
      struct xfs_inode  **i_tab)
{
      struct xfs_mount  *mp = i_tab[0]->i_mount;
      int               i;

      if (!XFS_IS_QUOTA_RUNNING(mp) || !XFS_IS_QUOTA_ON(mp))
            return 0;

      for (i = 0; (i < 4 && i_tab[i]); i++) {
            struct xfs_inode  *ip = i_tab[i];
            int               error;

            /*
             * Watch out for duplicate entries in the table.
             */
            if (i == 0 || ip != i_tab[i-1]) {
                  if (XFS_NOT_DQATTACHED(mp, ip)) {
                        error = xfs_qm_dqattach(ip, 0);
                        if (error)
                              return error;
                  }
            }
      }
      return 0;
}

void
xfs_qm_vop_create_dqattach(
      struct xfs_trans  *tp,
      struct xfs_inode  *ip,
      struct xfs_dquot  *udqp,
      struct xfs_dquot  *gdqp)
{
      struct xfs_mount  *mp = tp->t_mountp;

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

      ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
      ASSERT(XFS_IS_QUOTA_RUNNING(mp));

      if (udqp) {
            xfs_dqlock(udqp);
            XFS_DQHOLD(udqp);
            xfs_dqunlock(udqp);
            ASSERT(ip->i_udquot == NULL);
            ip->i_udquot = udqp;
            ASSERT(XFS_IS_UQUOTA_ON(mp));
            ASSERT(ip->i_d.di_uid == be32_to_cpu(udqp->q_core.d_id));
            xfs_trans_mod_dquot(tp, udqp, XFS_TRANS_DQ_ICOUNT, 1);
      }
      if (gdqp) {
            xfs_dqlock(gdqp);
            XFS_DQHOLD(gdqp);
            xfs_dqunlock(gdqp);
            ASSERT(ip->i_gdquot == NULL);
            ip->i_gdquot = gdqp;
            ASSERT(XFS_IS_OQUOTA_ON(mp));
            ASSERT((XFS_IS_GQUOTA_ON(mp) ?
                  ip->i_d.di_gid : ip->i_d.di_projid) ==
                        be32_to_cpu(gdqp->q_core.d_id));
            xfs_trans_mod_dquot(tp, gdqp, XFS_TRANS_DQ_ICOUNT, 1);
      }
}

/* ------------- list stuff -----------------*/
STATIC void
xfs_qm_freelist_init(xfs_frlist_t *ql)
{
      ql->qh_next = ql->qh_prev = (xfs_dquot_t *) ql;
      mutex_init(&ql->qh_lock);
      ql->qh_version = 0;
      ql->qh_nelems = 0;
}

STATIC void
xfs_qm_freelist_destroy(xfs_frlist_t *ql)
{
      xfs_dquot_t *dqp, *nextdqp;

      mutex_lock(&ql->qh_lock);
      for (dqp = ql->qh_next;
           dqp != (xfs_dquot_t *)ql; ) {
            xfs_dqlock(dqp);
            nextdqp = dqp->dq_flnext;
#ifdef QUOTADEBUG
            cmn_err(CE_DEBUG, "FREELIST destroy 0x%p", dqp);
#endif
            XQM_FREELIST_REMOVE(dqp);
            xfs_dqunlock(dqp);
            xfs_qm_dqdestroy(dqp);
            dqp = nextdqp;
      }
      mutex_unlock(&ql->qh_lock);
      mutex_destroy(&ql->qh_lock);

      ASSERT(ql->qh_nelems == 0);
}

STATIC void
xfs_qm_freelist_insert(xfs_frlist_t *ql, xfs_dquot_t *dq)
{
      dq->dq_flnext = ql->qh_next;
      dq->dq_flprev = (xfs_dquot_t *)ql;
      ql->qh_next = dq;
      dq->dq_flnext->dq_flprev = dq;
      xfs_Gqm->qm_dqfreelist.qh_nelems++;
      xfs_Gqm->qm_dqfreelist.qh_version++;
}

void
xfs_qm_freelist_unlink(xfs_dquot_t *dq)
{
      xfs_dquot_t *next = dq->dq_flnext;
      xfs_dquot_t *prev = dq->dq_flprev;

      next->dq_flprev = prev;
      prev->dq_flnext = next;
      dq->dq_flnext = dq->dq_flprev = dq;
      xfs_Gqm->qm_dqfreelist.qh_nelems--;
      xfs_Gqm->qm_dqfreelist.qh_version++;
}

void
xfs_qm_freelist_append(xfs_frlist_t *ql, xfs_dquot_t *dq)
{
      xfs_qm_freelist_insert((xfs_frlist_t *)ql->qh_prev, dq);
}

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