initial commit with v2.6.9

[linux-2.6.9-moxart.git] / fs / xfs / quota / xfs_dquot.c

/*
 * Copyright (c) 2000-2003 Silicon Graphics, Inc.  All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 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.
 *
 * Further, this software is distributed without any warranty that it is
 * free of the rightful claim of any third person regarding infringement
 * or the like.  Any license provided herein, whether implied or
 * otherwise, applies only to this software file.  Patent licenses, if
 * any, provided herein do not apply to combinations of this program with
 * other software, or any other product whatsoever.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
 * Mountain View, CA  94043, or:
 *
 * http://www.sgi.com
 *
 * For further information regarding this notice, see:
 *
 * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
 */

#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_inum.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir.h"
#include "xfs_dir2.h"
#include "xfs_alloc.h"
#include "xfs_dmapi.h"
#include "xfs_quota.h"
#include "xfs_mount.h"
#include "xfs_alloc_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_attr_sf.h"
#include "xfs_dir_sf.h"
#include "xfs_dir2_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_bit.h"
#include "xfs_rtalloc.h"
#include "xfs_error.h"
#include "xfs_itable.h"
#include "xfs_rw.h"
#include "xfs_acl.h"
#include "xfs_cap.h"
#include "xfs_mac.h"
#include "xfs_attr.h"
#include "xfs_buf_item.h"
#include "xfs_trans_space.h"
#include "xfs_trans_priv.h"

#include "xfs_qm.h"


/*
   LOCK ORDER

   inode lock               (ilock)
   dquot hash-chain lock    (hashlock)
   xqm dquot freelist lock  (freelistlock
   mount's dquot list lock  (mplistlock)
   user dquot lock - lock ordering among dquots is based on the uid or gid
   group dquot lock - similar to udquots. Between the two dquots, the udquot
                      has to be locked first.
   pin lock - the dquot lock must be held to take this lock.
   flush lock - ditto.
*/

STATIC void             xfs_qm_dqflush_done(xfs_buf_t *, xfs_dq_logitem_t *);

#ifdef DEBUG
xfs_buftarg_t *xfs_dqerror_target;
int xfs_do_dqerror;
int xfs_dqreq_num;
int xfs_dqerror_mod = 33;
#endif

/*
 * Allocate and initialize a dquot. We don't always allocate fresh memory;
 * we try to reclaim a free dquot if the number of incore dquots are above
 * a threshold.
 * The only field inside the core that gets initialized at this point
 * is the d_id field. The idea is to fill in the entire q_core
 * when we read in the on disk dquot.
 */
xfs_dquot_t *
xfs_qm_dqinit(
        xfs_mount_t  *mp,
        xfs_dqid_t   id,
        uint         type)
{
        xfs_dquot_t     *dqp;
        boolean_t       brandnewdquot;

        brandnewdquot = xfs_qm_dqalloc_incore(&dqp);
        dqp->dq_flags = type;
        INT_SET(dqp->q_core.d_id, ARCH_CONVERT, id);
        dqp->q_mount = mp;

        /*
         * No need to re-initialize these if this is a reclaimed dquot.
         */
        if (brandnewdquot) {
                dqp->dq_flnext = dqp->dq_flprev = dqp;
                mutex_init(&dqp->q_qlock,  MUTEX_DEFAULT, "xdq");
                initnsema(&dqp->q_flock, 1, "fdq");
                sv_init(&dqp->q_pinwait, SV_DEFAULT, "pdq");

#ifdef XFS_DQUOT_TRACE
                dqp->q_trace = ktrace_alloc(DQUOT_TRACE_SIZE, KM_SLEEP);
                xfs_dqtrace_entry(dqp, "DQINIT");
#endif
        } else {
                /*
                 * Only the q_core portion was zeroed in dqreclaim_one().
                 * So, we need to reset others.
                 */
                 dqp->q_nrefs = 0;
                 dqp->q_blkno = 0;
                 dqp->MPL_NEXT = dqp->HL_NEXT = NULL;
                 dqp->HL_PREVP = dqp->MPL_PREVP = NULL;
                 dqp->q_bufoffset = 0;
                 dqp->q_fileoffset = 0;
                 dqp->q_transp = NULL;
                 dqp->q_gdquot = NULL;
                 dqp->q_res_bcount = 0;
                 dqp->q_res_icount = 0;
                 dqp->q_res_rtbcount = 0;
                 dqp->q_pincount = 0;
                 dqp->q_hash = NULL;
                 ASSERT(dqp->dq_flnext == dqp->dq_flprev);

#ifdef XFS_DQUOT_TRACE
                 ASSERT(dqp->q_trace);
                 xfs_dqtrace_entry(dqp, "DQRECLAIMED_INIT");
#endif
         }

        /*
         * log item gets initialized later
         */
        return (dqp);
}

/*
 * This is called to free all the memory associated with a dquot
 */
void
xfs_qm_dqdestroy(
        xfs_dquot_t     *dqp)
{
        ASSERT(! XFS_DQ_IS_ON_FREELIST(dqp));

        mutex_destroy(&dqp->q_qlock);
        freesema(&dqp->q_flock);
        sv_destroy(&dqp->q_pinwait);

#ifdef XFS_DQUOT_TRACE
        if (dqp->q_trace)
             ktrace_free(dqp->q_trace);
        dqp->q_trace = NULL;
#endif
        kmem_zone_free(xfs_Gqm->qm_dqzone, dqp);
        atomic_dec(&xfs_Gqm->qm_totaldquots);
}

/*
 * This is what a 'fresh' dquot inside a dquot chunk looks like on disk.
 */
STATIC void
xfs_qm_dqinit_core(
        xfs_dqid_t      id,
        uint            type,
        xfs_dqblk_t     *d)
{
        /*
         * Caller has zero'd the entire dquot 'chunk' already.
         */
        INT_SET(d->dd_diskdq.d_magic, ARCH_CONVERT, XFS_DQUOT_MAGIC);
        INT_SET(d->dd_diskdq.d_version, ARCH_CONVERT, XFS_DQUOT_VERSION);
        INT_SET(d->dd_diskdq.d_id, ARCH_CONVERT, id);
        INT_SET(d->dd_diskdq.d_flags, ARCH_CONVERT, type);
}


#ifdef XFS_DQUOT_TRACE
/*
 * Dquot tracing for debugging.
 */
/* ARGSUSED */
void
__xfs_dqtrace_entry(
        xfs_dquot_t     *dqp,
        char            *func,
        void            *retaddr,
        xfs_inode_t     *ip)
{
        xfs_dquot_t     *udqp = NULL;
        xfs_ino_t       ino = 0;

        ASSERT(dqp->q_trace);
        if (ip) {
                ino = ip->i_ino;
                udqp = ip->i_udquot;
        }
        ktrace_enter(dqp->q_trace,
                     (void *)(__psint_t)DQUOT_KTRACE_ENTRY,
                     (void *)func,
                     (void *)(__psint_t)dqp->q_nrefs,
                     (void *)(__psint_t)dqp->dq_flags,
                     (void *)(__psint_t)dqp->q_res_bcount,
                     (void *)(__psint_t)INT_GET(dqp->q_core.d_bcount,
                                                ARCH_CONVERT),
                     (void *)(__psint_t)INT_GET(dqp->q_core.d_icount,
                                                ARCH_CONVERT),
                     (void *)(__psint_t)INT_GET(dqp->q_core.d_blk_hardlimit,
                                                ARCH_CONVERT),
                     (void *)(__psint_t)INT_GET(dqp->q_core.d_blk_softlimit,
                                                ARCH_CONVERT),
                     (void *)(__psint_t)INT_GET(dqp->q_core.d_ino_hardlimit,
                                                ARCH_CONVERT),
                     (void *)(__psint_t)INT_GET(dqp->q_core.d_ino_softlimit,
                                                ARCH_CONVERT),
                     (void *)(__psint_t)INT_GET(dqp->q_core.d_id, ARCH_CONVERT),
                     (void *)(__psint_t)current_pid(),
                     (void *)(__psint_t)ino,
                     (void *)(__psint_t)retaddr,
                     (void *)(__psint_t)udqp);
        return;
}
#endif


/*
 * If default limits are in force, push them into the dquot now.
 * We overwrite the dquot limits only if they are zero and this
 * is not the root dquot.
 */
void
xfs_qm_adjust_dqlimits(
        xfs_mount_t             *mp,
        xfs_disk_dquot_t        *d)
{
        xfs_quotainfo_t         *q = mp->m_quotainfo;

        ASSERT(!INT_ISZERO(d->d_id, ARCH_CONVERT));

        if (q->qi_bsoftlimit && INT_ISZERO(d->d_blk_softlimit, ARCH_CONVERT))
                INT_SET(d->d_blk_softlimit, ARCH_CONVERT, q->qi_bsoftlimit);
        if (q->qi_bhardlimit && INT_ISZERO(d->d_blk_hardlimit, ARCH_CONVERT))
                INT_SET(d->d_blk_hardlimit, ARCH_CONVERT, q->qi_bhardlimit);
        if (q->qi_isoftlimit && INT_ISZERO(d->d_ino_softlimit, ARCH_CONVERT))
                INT_SET(d->d_ino_softlimit, ARCH_CONVERT, q->qi_isoftlimit);
        if (q->qi_ihardlimit && INT_ISZERO(d->d_ino_hardlimit, ARCH_CONVERT))
                INT_SET(d->d_ino_hardlimit, ARCH_CONVERT, q->qi_ihardlimit);
        if (q->qi_rtbsoftlimit &&
            INT_ISZERO(d->d_rtb_softlimit, ARCH_CONVERT))
                INT_SET(d->d_rtb_softlimit, ARCH_CONVERT, q->qi_rtbsoftlimit);
        if (q->qi_rtbhardlimit &&
            INT_ISZERO(d->d_rtb_hardlimit, ARCH_CONVERT))
                INT_SET(d->d_rtb_hardlimit, ARCH_CONVERT, q->qi_rtbhardlimit);
}

/*
 * Check the limits and timers of a dquot and start or reset timers
 * if necessary.
 * This gets called even when quota enforcement is OFF, which makes our
 * life a little less complicated. (We just don't reject any quota
 * reservations in that case, when enforcement is off).
 * We also return 0 as the values of the timers in Q_GETQUOTA calls, when
 * enforcement's off.
 * In contrast, warnings are a little different in that they don't
 * 'automatically' get started when limits get exceeded.
 */
void
xfs_qm_adjust_dqtimers(
        xfs_mount_t             *mp,
        xfs_disk_dquot_t        *d)
{
        ASSERT(!INT_ISZERO(d->d_id, ARCH_CONVERT));

#ifdef QUOTADEBUG
        if (INT_GET(d->d_blk_hardlimit, ARCH_CONVERT))
                ASSERT(INT_GET(d->d_blk_softlimit, ARCH_CONVERT) <=
                        INT_GET(d->d_blk_hardlimit, ARCH_CONVERT));
        if (INT_GET(d->d_ino_hardlimit, ARCH_CONVERT))
                ASSERT(INT_GET(d->d_ino_softlimit, ARCH_CONVERT) <=
                        INT_GET(d->d_ino_hardlimit, ARCH_CONVERT));
        if (INT_GET(d->d_rtb_hardlimit, ARCH_CONVERT))
                ASSERT(INT_GET(d->d_rtb_softlimit, ARCH_CONVERT) <=
                        INT_GET(d->d_rtb_hardlimit, ARCH_CONVERT));
#endif
        if (INT_ISZERO(d->d_btimer, ARCH_CONVERT)) {
                if ((INT_GET(d->d_blk_softlimit, ARCH_CONVERT) &&
                    (INT_GET(d->d_bcount, ARCH_CONVERT) >=
                                INT_GET(d->d_blk_softlimit, ARCH_CONVERT))) ||
                    (INT_GET(d->d_blk_hardlimit, ARCH_CONVERT) &&
                    (INT_GET(d->d_bcount, ARCH_CONVERT) >=
                                INT_GET(d->d_blk_hardlimit, ARCH_CONVERT)))) {
                        INT_SET(d->d_btimer, ARCH_CONVERT,
                                get_seconds() + XFS_QI_BTIMELIMIT(mp));
                }
        } else {
                if ((INT_ISZERO(d->d_blk_softlimit, ARCH_CONVERT) ||
                    (INT_GET(d->d_bcount, ARCH_CONVERT) <
                                INT_GET(d->d_blk_softlimit, ARCH_CONVERT))) &&
                    (INT_ISZERO(d->d_blk_hardlimit, ARCH_CONVERT) ||
                    (INT_GET(d->d_bcount, ARCH_CONVERT) <
                                INT_GET(d->d_blk_hardlimit, ARCH_CONVERT)))) {
                        INT_ZERO(d->d_btimer, ARCH_CONVERT);
                }
        }

        if (INT_ISZERO(d->d_itimer, ARCH_CONVERT)) {
                if ((INT_GET(d->d_ino_softlimit, ARCH_CONVERT) &&
                    (INT_GET(d->d_icount, ARCH_CONVERT) >=
                                INT_GET(d->d_ino_softlimit, ARCH_CONVERT))) ||
                    (INT_GET(d->d_ino_hardlimit, ARCH_CONVERT) &&
                    (INT_GET(d->d_icount, ARCH_CONVERT) >=
                                INT_GET(d->d_ino_hardlimit, ARCH_CONVERT)))) {
                        INT_SET(d->d_itimer, ARCH_CONVERT,
                                get_seconds() + XFS_QI_ITIMELIMIT(mp));
                }
        } else {
                if ((INT_ISZERO(d->d_ino_softlimit, ARCH_CONVERT) ||
                    (INT_GET(d->d_icount, ARCH_CONVERT) <
                                INT_GET(d->d_ino_softlimit, ARCH_CONVERT)))  &&
                    (INT_ISZERO(d->d_ino_hardlimit, ARCH_CONVERT) ||
                    (INT_GET(d->d_icount, ARCH_CONVERT) <
                                INT_GET(d->d_ino_hardlimit, ARCH_CONVERT)))) {
                        INT_ZERO(d->d_itimer, ARCH_CONVERT);
                }
        }

        if (INT_ISZERO(d->d_rtbtimer, ARCH_CONVERT)) {
                if ((INT_GET(d->d_rtb_softlimit, ARCH_CONVERT) &&
                    (INT_GET(d->d_rtbcount, ARCH_CONVERT) >=
                                INT_GET(d->d_rtb_softlimit, ARCH_CONVERT))) ||
                    (INT_GET(d->d_rtb_hardlimit, ARCH_CONVERT) &&
                    (INT_GET(d->d_rtbcount, ARCH_CONVERT) >=
                                INT_GET(d->d_rtb_hardlimit, ARCH_CONVERT)))) {
                        INT_SET(d->d_rtbtimer, ARCH_CONVERT,
                                get_seconds() + XFS_QI_RTBTIMELIMIT(mp));
                }
        } else {
                if ((INT_ISZERO(d->d_rtb_softlimit, ARCH_CONVERT) ||
                    (INT_GET(d->d_rtbcount, ARCH_CONVERT) <
                                INT_GET(d->d_rtb_softlimit, ARCH_CONVERT))) &&
                    (INT_ISZERO(d->d_rtb_hardlimit, ARCH_CONVERT) ||
                    (INT_GET(d->d_rtbcount, ARCH_CONVERT) <
                                INT_GET(d->d_rtb_hardlimit, ARCH_CONVERT)))) {
                        INT_ZERO(d->d_rtbtimer, ARCH_CONVERT);
                }
        }
}

/*
 * Increment or reset warnings of a given dquot.
 */
int
xfs_qm_dqwarn(
        xfs_disk_dquot_t        *d,
        uint                    flags)
{
        int     warned;

        /*
         * root's limits are not real limits.
         */
        if (INT_ISZERO(d->d_id, ARCH_CONVERT))
                return (0);

        warned = 0;
        if (INT_GET(d->d_blk_softlimit, ARCH_CONVERT) &&
            (INT_GET(d->d_bcount, ARCH_CONVERT) >=
             INT_GET(d->d_blk_softlimit, ARCH_CONVERT))) {
                if (flags & XFS_QMOPT_DOWARN) {
                        INT_MOD(d->d_bwarns, ARCH_CONVERT, +1);
                        warned++;
                }
        } else {
                if (INT_ISZERO(d->d_blk_softlimit, ARCH_CONVERT) ||
                    (INT_GET(d->d_bcount, ARCH_CONVERT) <
                     INT_GET(d->d_blk_softlimit, ARCH_CONVERT))) {
                        INT_ZERO(d->d_bwarns, ARCH_CONVERT);
                }
        }

        if (INT_GET(d->d_ino_softlimit, ARCH_CONVERT) > 0 &&
            (INT_GET(d->d_icount, ARCH_CONVERT) >=
             INT_GET(d->d_ino_softlimit, ARCH_CONVERT))) {
                if (flags & XFS_QMOPT_DOWARN) {
                        INT_MOD(d->d_iwarns, ARCH_CONVERT, +1);
                        warned++;
                }
        } else {
                if ((INT_ISZERO(d->d_ino_softlimit, ARCH_CONVERT)) ||
                    (INT_GET(d->d_icount, ARCH_CONVERT) <
                     INT_GET(d->d_ino_softlimit, ARCH_CONVERT))) {
                        INT_ZERO(d->d_iwarns, ARCH_CONVERT);
                }
        }
#ifdef QUOTADEBUG
        if (INT_GET(d->d_iwarns, ARCH_CONVERT))
                cmn_err(CE_DEBUG,
                        "--------@@Inode warnings running : %Lu >= %Lu",
                        INT_GET(d->d_icount, ARCH_CONVERT),
                        INT_GET(d->d_ino_softlimit, ARCH_CONVERT));
        if (INT_GET(d->d_bwarns, ARCH_CONVERT))
                cmn_err(CE_DEBUG,
                        "--------@@Blks warnings running : %Lu >= %Lu",
                        INT_GET(d->d_bcount, ARCH_CONVERT),
                        INT_GET(d->d_blk_softlimit, ARCH_CONVERT));
#endif
        return (warned);
}


/*
 * initialize a buffer full of dquots and log the whole thing
 */
STATIC void
xfs_qm_init_dquot_blk(
        xfs_trans_t     *tp,
        xfs_mount_t     *mp,
        xfs_dqid_t      id,
        uint            type,
        xfs_buf_t       *bp)
{
        xfs_dqblk_t     *d;
        int             curid, i;

        ASSERT(tp);
        ASSERT(XFS_BUF_ISBUSY(bp));
        ASSERT(XFS_BUF_VALUSEMA(bp) <= 0);

        d = (xfs_dqblk_t *)XFS_BUF_PTR(bp);

        /*
         * ID of the first dquot in the block - id's are zero based.
         */
        curid = id - (id % XFS_QM_DQPERBLK(mp));
        ASSERT(curid >= 0);
        memset(d, 0, BBTOB(XFS_QI_DQCHUNKLEN(mp)));
        for (i = 0; i < XFS_QM_DQPERBLK(mp); i++, d++, curid++)
                xfs_qm_dqinit_core(curid, type, d);
        xfs_trans_dquot_buf(tp, bp,
                            type & XFS_DQ_USER ?
                            XFS_BLI_UDQUOT_BUF :
                            XFS_BLI_GDQUOT_BUF);
        xfs_trans_log_buf(tp, bp, 0, BBTOB(XFS_QI_DQCHUNKLEN(mp)) - 1);
}



/*
 * Allocate a block and fill it with dquots.
 * This is called when the bmapi finds a hole.
 */
STATIC int
xfs_qm_dqalloc(
        xfs_trans_t     *tp,
        xfs_mount_t     *mp,
        xfs_dquot_t     *dqp,
        xfs_inode_t     *quotip,
        xfs_fileoff_t   offset_fsb,
        xfs_buf_t       **O_bpp)
{
        xfs_fsblock_t   firstblock;
        xfs_bmap_free_t flist;
        xfs_bmbt_irec_t map;
        int             nmaps, error, committed;
        xfs_buf_t       *bp;

        ASSERT(tp != NULL);
        xfs_dqtrace_entry(dqp, "DQALLOC");

        /*
         * Initialize the bmap freelist prior to calling bmapi code.
         */
        XFS_BMAP_INIT(&flist, &firstblock);
        xfs_ilock(quotip, XFS_ILOCK_EXCL);
        /*
         * Return if this type of quotas is turned off while we didn't
         * have an inode lock
         */
        if (XFS_IS_THIS_QUOTA_OFF(dqp)) {
                xfs_iunlock(quotip, XFS_ILOCK_EXCL);
                return (ESRCH);
        }

        /*
         * xfs_trans_commit normally decrements the vnode ref count
         * when it unlocks the inode. Since we want to keep the quota
         * inode around, we bump the vnode ref count now.
         */
        VN_HOLD(XFS_ITOV(quotip));

        xfs_trans_ijoin(tp, quotip, XFS_ILOCK_EXCL);
        nmaps = 1;
        if ((error = xfs_bmapi(tp, quotip,
                              offset_fsb, XFS_DQUOT_CLUSTER_SIZE_FSB,
                              XFS_BMAPI_METADATA | XFS_BMAPI_WRITE,
                              &firstblock,
                              XFS_QM_DQALLOC_SPACE_RES(mp),
                              &map, &nmaps, &flist))) {
                goto error0;
        }
        ASSERT(map.br_blockcount == XFS_DQUOT_CLUSTER_SIZE_FSB);
        ASSERT(nmaps == 1);
        ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
               (map.br_startblock != HOLESTARTBLOCK));

        /*
         * Keep track of the blkno to save a lookup later
         */
        dqp->q_blkno = XFS_FSB_TO_DADDR(mp, map.br_startblock);

        /* now we can just get the buffer (there's nothing to read yet) */
        bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
                               dqp->q_blkno,
                               XFS_QI_DQCHUNKLEN(mp),
                               0);
        if (!bp || (error = XFS_BUF_GETERROR(bp)))
                goto error1;
        /*
         * Make a chunk of dquots out of this buffer and log
         * the entire thing.
         */
        xfs_qm_init_dquot_blk(tp, mp, INT_GET(dqp->q_core.d_id, ARCH_CONVERT),
                              dqp->dq_flags & (XFS_DQ_USER|XFS_DQ_GROUP),
                              bp);

        if ((error = xfs_bmap_finish(&tp, &flist, firstblock, &committed))) {
                goto error1;
        }

        *O_bpp = bp;
        return 0;

      error1:
        xfs_bmap_cancel(&flist);
      error0:
        xfs_iunlock(quotip, XFS_ILOCK_EXCL);

        return (error);
}

/*
 * Maps a dquot to the buffer containing its on-disk version.
 * This returns a ptr to the buffer containing the on-disk dquot
 * in the bpp param, and a ptr to the on-disk dquot within that buffer
 */
STATIC int
xfs_qm_dqtobp(
        xfs_trans_t             *tp,
        xfs_dquot_t             *dqp,
        xfs_disk_dquot_t        **O_ddpp,
        xfs_buf_t               **O_bpp,
        uint                    flags)
{
        xfs_bmbt_irec_t map;
        int             nmaps, error;
        xfs_buf_t       *bp;
        xfs_inode_t     *quotip;
        xfs_mount_t     *mp;
        xfs_disk_dquot_t *ddq;
        xfs_dqid_t      id;
        boolean_t       newdquot;

        mp = dqp->q_mount;
        id = INT_GET(dqp->q_core.d_id, ARCH_CONVERT);
        nmaps = 1;
        newdquot = B_FALSE;

        /*
         * If we don't know where the dquot lives, find out.
         */
        if (dqp->q_blkno == (xfs_daddr_t) 0) {
                /* We use the id as an index */
                dqp->q_fileoffset = (xfs_fileoff_t) ((uint)id /
                                                     XFS_QM_DQPERBLK(mp));
                nmaps = 1;
                quotip = XFS_DQ_TO_QIP(dqp);
                xfs_ilock(quotip, XFS_ILOCK_SHARED);
                /*
                 * Return if this type of quotas is turned off while we didn't
                 * have an inode lock
                 */
                if (XFS_IS_THIS_QUOTA_OFF(dqp)) {
                        xfs_iunlock(quotip, XFS_ILOCK_SHARED);
                        return (ESRCH);
                }
                /*
                 * Find the block map; no allocations yet
                 */
                error = xfs_bmapi(NULL, quotip, dqp->q_fileoffset,
                                  XFS_DQUOT_CLUSTER_SIZE_FSB,
                                  XFS_BMAPI_METADATA,
                                  NULL, 0, &map, &nmaps, NULL);

                xfs_iunlock(quotip, XFS_ILOCK_SHARED);
                if (error)
                        return (error);
                ASSERT(nmaps == 1);
                ASSERT(map.br_blockcount == 1);

                /*
                 * offset of dquot in the (fixed sized) dquot chunk.
                 */
                dqp->q_bufoffset = (id % XFS_QM_DQPERBLK(mp)) *
                        sizeof(xfs_dqblk_t);
                if (map.br_startblock == HOLESTARTBLOCK) {
                        /*
                         * We don't allocate unless we're asked to
                         */
                        if (!(flags & XFS_QMOPT_DQALLOC))
                                return (ENOENT);

                        ASSERT(tp);
                        if ((error = xfs_qm_dqalloc(tp, mp, dqp, quotip,
                                                dqp->q_fileoffset, &bp)))
                                return (error);
                        newdquot = B_TRUE;
                } else {
                        /*
                         * store the blkno etc so that we don't have to do the
                         * mapping all the time
                         */
                        dqp->q_blkno = XFS_FSB_TO_DADDR(mp, map.br_startblock);
                }
        }
        ASSERT(dqp->q_blkno != DELAYSTARTBLOCK);
        ASSERT(dqp->q_blkno != HOLESTARTBLOCK);

        /*
         * Read in the buffer, unless we've just done the allocation
         * (in which case we already have the buf).
         */
        if (! newdquot) {
                xfs_dqtrace_entry(dqp, "DQTOBP READBUF");
                if ((error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                                               dqp->q_blkno,
                                               XFS_QI_DQCHUNKLEN(mp),
                                               0, &bp))) {
                        return (error);
                }
                if (error || !bp)
                        return XFS_ERROR(error);
        }
        ASSERT(XFS_BUF_ISBUSY(bp));
        ASSERT(XFS_BUF_VALUSEMA(bp) <= 0);

        /*
         * calculate the location of the dquot inside the buffer.
         */
        ddq = (xfs_disk_dquot_t *)((char *)XFS_BUF_PTR(bp) + dqp->q_bufoffset);

        /*
         * A simple sanity check in case we got a corrupted dquot...
         */
        if (xfs_qm_dqcheck(ddq, id,
                           dqp->dq_flags & (XFS_DQ_USER|XFS_DQ_GROUP),
                           flags & (XFS_QMOPT_DQREPAIR|XFS_QMOPT_DOWARN),
                           "dqtobp")) {
                if (!(flags & XFS_QMOPT_DQREPAIR)) {
                        xfs_trans_brelse(tp, bp);
                        return XFS_ERROR(EIO);
                }
                XFS_BUF_BUSY(bp); /* We dirtied this */
        }

        *O_bpp = bp;
        *O_ddpp = ddq;

        return (0);
}


/*
 * Read in the ondisk dquot using dqtobp() then copy it to an incore version,
 * and release the buffer immediately.
 *
 */
/* ARGSUSED */
STATIC int
xfs_qm_dqread(
        xfs_trans_t     *tp,
        xfs_dqid_t      id,
        xfs_dquot_t     *dqp,   /* dquot to get filled in */
        uint            flags)
{
        xfs_disk_dquot_t *ddqp;
        xfs_buf_t        *bp;
        int              error;

        /*
         * get a pointer to the on-disk dquot and the buffer containing it
         * dqp already knows its own type (GROUP/USER).
         */
        xfs_dqtrace_entry(dqp, "DQREAD");
        if ((error = xfs_qm_dqtobp(tp, dqp, &ddqp, &bp, flags))) {
                return (error);
        }

        /* copy everything from disk dquot to the incore dquot */
        memcpy(&dqp->q_core, ddqp, sizeof(xfs_disk_dquot_t));
        ASSERT(INT_GET(dqp->q_core.d_id, ARCH_CONVERT) == id);
        xfs_qm_dquot_logitem_init(dqp);

        /*
         * Reservation counters are defined as reservation plus current usage
         * to avoid having to add everytime.
         */
        dqp->q_res_bcount = INT_GET(ddqp->d_bcount, ARCH_CONVERT);
        dqp->q_res_icount = INT_GET(ddqp->d_icount, ARCH_CONVERT);
        dqp->q_res_rtbcount = INT_GET(ddqp->d_rtbcount, ARCH_CONVERT);

        /* Mark the buf so that this will stay incore a little longer */
        XFS_BUF_SET_VTYPE_REF(bp, B_FS_DQUOT, XFS_DQUOT_REF);

        /*
         * We got the buffer with a xfs_trans_read_buf() (in dqtobp())
         * So we need to release with xfs_trans_brelse().
         * The strategy here is identical to that of inodes; we lock
         * the dquot in xfs_qm_dqget() before making it accessible to
         * others. This is because dquots, like inodes, need a good level of
         * concurrency, and we don't want to take locks on the entire buffers
         * for dquot accesses.
         * Note also that the dquot buffer may even be dirty at this point, if
         * this particular dquot was repaired. We still aren't afraid to
         * brelse it because we have the changes incore.
         */
        ASSERT(XFS_BUF_ISBUSY(bp));
        ASSERT(XFS_BUF_VALUSEMA(bp) <= 0);
        xfs_trans_brelse(tp, bp);

        return (error);
}


/*
 * allocate an incore dquot from the kernel heap,
 * and fill its core with quota information kept on disk.
 * If XFS_QMOPT_DQALLOC is set, it'll allocate a dquot on disk
 * if it wasn't already allocated.
 */
STATIC int
xfs_qm_idtodq(
        xfs_mount_t     *mp,
        xfs_dqid_t      id,      /* gid or uid, depending on type */
        uint            type,    /* UDQUOT or GDQUOT */
        uint            flags,   /* DQALLOC, DQREPAIR */
        xfs_dquot_t     **O_dqpp)/* OUT : incore dquot, not locked */
{
        xfs_dquot_t     *dqp;
        int             error;
        xfs_trans_t     *tp;
        int             cancelflags=0;

        dqp = xfs_qm_dqinit(mp, id, type);
        tp = NULL;
        if (flags & XFS_QMOPT_DQALLOC) {
                tp = xfs_trans_alloc(mp, XFS_TRANS_QM_DQALLOC);
                if ((error = xfs_trans_reserve(tp,
                                       XFS_QM_DQALLOC_SPACE_RES(mp),
                                       XFS_WRITE_LOG_RES(mp) +
                                              BBTOB(XFS_QI_DQCHUNKLEN(mp)) - 1 +
                                              128,
                                       0,
                                       XFS_TRANS_PERM_LOG_RES,
                                       XFS_WRITE_LOG_COUNT))) {
                        cancelflags = 0;
                        goto error0;
                }
                cancelflags = XFS_TRANS_RELEASE_LOG_RES;
        }

        /*
         * Read it from disk; xfs_dqread() takes care of
         * all the necessary initialization of dquot's fields (locks, etc)
         */
        if ((error = xfs_qm_dqread(tp, id, dqp, flags))) {
                /*
                 * This can happen if quotas got turned off (ESRCH),
                 * or if the dquot didn't exist on disk and we ask to
                 * allocate (ENOENT).
                 */
                xfs_dqtrace_entry(dqp, "DQREAD FAIL");
                cancelflags |= XFS_TRANS_ABORT;
                goto error0;
        }
        if (tp) {
                if ((error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES,
                                             NULL)))
                        goto error1;
        }

        *O_dqpp = dqp;
        return (0);

 error0:
        ASSERT(error);
        if (tp)
                xfs_trans_cancel(tp, cancelflags);
 error1:
        xfs_qm_dqdestroy(dqp);
        *O_dqpp = NULL;
        return (error);
}

/*
 * Lookup a dquot in the incore dquot hashtable. We keep two separate
 * hashtables for user and group dquots; and, these are global tables
 * inside the XQM, not per-filesystem tables.
 * The hash chain must be locked by caller, and it is left locked
 * on return. Returning dquot is locked.
 */
STATIC int
xfs_qm_dqlookup(
        xfs_mount_t             *mp,
        xfs_dqid_t              id,
        xfs_dqhash_t            *qh,
        xfs_dquot_t             **O_dqpp)
{
        xfs_dquot_t             *dqp;
        uint                    flist_locked;
        xfs_dquot_t             *d;

        ASSERT(XFS_DQ_IS_HASH_LOCKED(qh));

        flist_locked = B_FALSE;

        /*
         * Traverse the hashchain looking for a match
         */
        for (dqp = qh->qh_next; dqp != NULL; dqp = dqp->HL_NEXT) {
                /*
                 * We already have the hashlock. We don't need the
                 * dqlock to look at the id field of the dquot, since the
                 * id can't be modified without the hashlock anyway.
                 */
                if (INT_GET(dqp->q_core.d_id, ARCH_CONVERT) == id && dqp->q_mount == mp) {
                        xfs_dqtrace_entry(dqp, "DQFOUND BY LOOKUP");
                        /*
                         * All in core dquots must be on the dqlist of mp
                         */
                        ASSERT(dqp->MPL_PREVP != NULL);

                        xfs_dqlock(dqp);
                        if (dqp->q_nrefs == 0) {
                                ASSERT (XFS_DQ_IS_ON_FREELIST(dqp));
                                if (! xfs_qm_freelist_lock_nowait(xfs_Gqm)) {
                                        xfs_dqtrace_entry(dqp, "DQLOOKUP: WANT");

                                        /*
                                         * We may have raced with dqreclaim_one()
                                         * (and lost). So, flag that we don't
                                         * want the dquot to be reclaimed.
                                         */
                                        dqp->dq_flags |= XFS_DQ_WANT;
                                        xfs_dqunlock(dqp);
                                        xfs_qm_freelist_lock(xfs_Gqm);
                                        xfs_dqlock(dqp);
                                        dqp->dq_flags &= ~(XFS_DQ_WANT);
                                }
                                flist_locked = B_TRUE;
                        }

                        /*
                         * id couldn't have changed; we had the hashlock all
                         * along
                         */
                        ASSERT(INT_GET(dqp->q_core.d_id, ARCH_CONVERT) == id);

                        if (flist_locked) {
                                if (dqp->q_nrefs != 0) {
                                        xfs_qm_freelist_unlock(xfs_Gqm);
                                        flist_locked = B_FALSE;
                                } else {
                                        /*
                                         * take it off the freelist
                                         */
                                        xfs_dqtrace_entry(dqp,
                                                        "DQLOOKUP: TAKEOFF FL");
                                        XQM_FREELIST_REMOVE(dqp);
                                        /* xfs_qm_freelist_print(&(xfs_Gqm->
                                                        qm_dqfreelist),
                                                        "after removal"); */
                                }
                        }

                        /*
                         * grab a reference
                         */
                        XFS_DQHOLD(dqp);

                        if (flist_locked)
                                xfs_qm_freelist_unlock(xfs_Gqm);
                        /*
                         * move the dquot to the front of the hashchain
                         */
                        ASSERT(XFS_DQ_IS_HASH_LOCKED(qh));
                        if (dqp->HL_PREVP != &qh->qh_next) {
                                xfs_dqtrace_entry(dqp,
                                                  "DQLOOKUP: HASH MOVETOFRONT");
                                if ((d = dqp->HL_NEXT))
                                        d->HL_PREVP = dqp->HL_PREVP;
                                *(dqp->HL_PREVP) = d;
                                d = qh->qh_next;
                                d->HL_PREVP = &dqp->HL_NEXT;
                                dqp->HL_NEXT = d;
                                dqp->HL_PREVP = &qh->qh_next;
                                qh->qh_next = dqp;
                        }
                        xfs_dqtrace_entry(dqp, "LOOKUP END");
                        *O_dqpp = dqp;
                        ASSERT(XFS_DQ_IS_HASH_LOCKED(qh));
                        return (0);
                }
        }

        *O_dqpp = NULL;
        ASSERT(XFS_DQ_IS_HASH_LOCKED(qh));
        return (1);
}

/*
 * Given the file system, inode OR id, and type (UDQUOT/GDQUOT), return a
 * a locked dquot, doing an allocation (if requested) as needed.
 * When both an inode and an id are given, the inode's id takes precedence.
 * That is, if the id changes while we don't hold the ilock inside this
 * function, the new dquot is returned, not necessarily the one requested
 * in the id argument.
 */
int
xfs_qm_dqget(
        xfs_mount_t     *mp,
        xfs_inode_t     *ip,      /* locked inode (optional) */
        xfs_dqid_t      id,       /* gid or uid, depending on type */
        uint            type,     /* UDQUOT or GDQUOT */
        uint            flags,    /* DQALLOC, DQSUSER, DQREPAIR, DOWARN */
        xfs_dquot_t     **O_dqpp) /* OUT : locked incore dquot */
{
        xfs_dquot_t     *dqp;
        xfs_dqhash_t    *h;
        uint            version;
        int             error;

        ASSERT(XFS_IS_QUOTA_RUNNING(mp));
        if ((! XFS_IS_UQUOTA_ON(mp) && type == XFS_DQ_USER) ||
            (! XFS_IS_GQUOTA_ON(mp) && type == XFS_DQ_GROUP)) {
                return (ESRCH);
        }
        h = XFS_DQ_HASH(mp, id, type);

#ifdef DEBUG
        if (xfs_do_dqerror) {
                if ((xfs_dqerror_target == mp->m_ddev_targp) &&
                    (xfs_dqreq_num++ % xfs_dqerror_mod) == 0) {
                        cmn_err(CE_DEBUG, "Returning error in dqget");
                        return (EIO);
                }
        }
#endif

 again:

#ifdef DEBUG
        ASSERT(type == XFS_DQ_USER || type == XFS_DQ_GROUP);
        if (ip) {
                ASSERT(XFS_ISLOCKED_INODE_EXCL(ip));
                if (type == XFS_DQ_USER)
                        ASSERT(ip->i_udquot == NULL);
                else
                        ASSERT(ip->i_gdquot == NULL);
        }
#endif
        XFS_DQ_HASH_LOCK(h);

        /*
         * Look in the cache (hashtable).
         * The chain is kept locked during lookup.
         */
        if (xfs_qm_dqlookup(mp, id, h, O_dqpp) == 0) {
                XQM_STATS_INC(xqmstats.xs_qm_dqcachehits);
                /*
                 * The dquot was found, moved to the front of the chain,
                 * taken off the freelist if it was on it, and locked
                 * at this point. Just unlock the hashchain and return.
                 */
                ASSERT(*O_dqpp);
                ASSERT(XFS_DQ_IS_LOCKED(*O_dqpp));
                XFS_DQ_HASH_UNLOCK(h);
                xfs_dqtrace_entry(*O_dqpp, "DQGET DONE (FROM CACHE)");
                return (0);     /* success */
        }
        XQM_STATS_INC(xqmstats.xs_qm_dqcachemisses);

        /*
         * Dquot cache miss. We don't want to keep the inode lock across
         * a (potential) disk read. Also we don't want to deal with the lock
         * ordering between quotainode and this inode. OTOH, dropping the inode
         * lock here means dealing with a chown that can happen before
         * we re-acquire the lock.
         */
        if (ip)
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
        /*
         * Save the hashchain version stamp, and unlock the chain, so that
         * we don't keep the lock across a disk read
         */
        version = h->qh_version;
        XFS_DQ_HASH_UNLOCK(h);

        /*
         * Allocate the dquot on the kernel heap, and read the ondisk
         * portion off the disk. Also, do all the necessary initialization
         * 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.
         */
        if ((error = xfs_qm_idtodq(mp, id, type,
                                  flags & (XFS_QMOPT_DQALLOC|XFS_QMOPT_DQREPAIR|
                                           XFS_QMOPT_DOWARN),
                                  &dqp))) {
                if (ip)
                        xfs_ilock(ip, XFS_ILOCK_EXCL);
                return (error);
        }

        /*
         * See if this is mount code calling to look at the overall quota limits
         * which are stored in the id == 0 user or group's dquot.
         * Since we may not have done a quotacheck by this point, just return
         * the dquot without attaching it to any hashtables, lists, etc, or even
         * taking a reference.
         * The caller must dqdestroy this once done.
         */
        if (flags & XFS_QMOPT_DQSUSER) {
                ASSERT(id == 0);
                ASSERT(! ip);
                goto dqret;
        }

        /*
         * Dquot lock comes after hashlock in the lock ordering
         */
        if (ip) {
                xfs_ilock(ip, XFS_ILOCK_EXCL);
                if (! XFS_IS_DQTYPE_ON(mp, type)) {
                        /* inode stays locked on return */
                        xfs_qm_dqdestroy(dqp);
                        return XFS_ERROR(ESRCH);
                }
                /*
                 * A dquot could be attached to this inode by now, since
                 * we had dropped the ilock.
                 */
                if (type == XFS_DQ_USER) {
                        if (ip->i_udquot) {
                                xfs_qm_dqdestroy(dqp);
                                dqp = ip->i_udquot;
                                xfs_dqlock(dqp);
                                goto dqret;
                        }
                } else {
                        if (ip->i_gdquot) {
                                xfs_qm_dqdestroy(dqp);
                                dqp = ip->i_gdquot;
                                xfs_dqlock(dqp);
                                goto dqret;
                        }
                }
        }

        /*
         * Hashlock comes after ilock in lock order
         */
        XFS_DQ_HASH_LOCK(h);
        if (version != h->qh_version) {
                xfs_dquot_t *tmpdqp;
                /*
                 * Now, see if somebody else put the dquot in the
                 * hashtable before us. This can happen because we didn't
                 * keep the hashchain lock. We don't have to worry about
                 * lock order between the two dquots here since dqp isn't
                 * on any findable lists yet.
                 */
                if (xfs_qm_dqlookup(mp, id, h, &tmpdqp) == 0) {
                        /*
                         * Duplicate found. Just throw away the new dquot
                         * and start over.
                         */
                        xfs_qm_dqput(tmpdqp);
                        XFS_DQ_HASH_UNLOCK(h);
                        xfs_qm_dqdestroy(dqp);
                        XQM_STATS_INC(xqmstats.xs_qm_dquot_dups);
                        goto again;
                }
        }

        /*
         * Put the dquot at the beginning of the hash-chain and mp's list
         * LOCK ORDER: hashlock, freelistlock, mplistlock, udqlock, gdqlock ..
         */
        ASSERT(XFS_DQ_IS_HASH_LOCKED(h));
        dqp->q_hash = h;
        XQM_HASHLIST_INSERT(h, dqp);

        /*
         * Attach this dquot to this filesystem's list of all dquots,
         * kept inside the mount structure in m_quotainfo field
         */
        xfs_qm_mplist_lock(mp);

        /*
         * We return a locked dquot to the caller, with a reference taken
         */
        xfs_dqlock(dqp);
        dqp->q_nrefs = 1;

        XQM_MPLIST_INSERT(&(XFS_QI_MPL_LIST(mp)), dqp);

        xfs_qm_mplist_unlock(mp);
        XFS_DQ_HASH_UNLOCK(h);
 dqret:
        ASSERT((ip == NULL) || XFS_ISLOCKED_INODE_EXCL(ip));
        xfs_dqtrace_entry(dqp, "DQGET DONE");
        *O_dqpp = dqp;
        return (0);
}


/*
 * Release a reference to the dquot (decrement ref-count)
 * and unlock it. If there is a group quota attached to this
 * dquot, carefully release that too without tripping over
 * deadlocks'n'stuff.
 */
void
xfs_qm_dqput(
        xfs_dquot_t     *dqp)
{
        xfs_dquot_t     *gdqp;

        ASSERT(dqp->q_nrefs > 0);
        ASSERT(XFS_DQ_IS_LOCKED(dqp));
        xfs_dqtrace_entry(dqp, "DQPUT");

        if (dqp->q_nrefs != 1) {
                dqp->q_nrefs--;
                xfs_dqunlock(dqp);
                return;
        }

        /*
         * drop the dqlock and acquire the freelist and dqlock
         * in the right order; but try to get it out-of-order first
         */
        if (! xfs_qm_freelist_lock_nowait(xfs_Gqm)) {
                xfs_dqtrace_entry(dqp, "DQPUT: FLLOCK-WAIT");
                xfs_dqunlock(dqp);
                xfs_qm_freelist_lock(xfs_Gqm);
                xfs_dqlock(dqp);
        }

        while (1) {
                gdqp = NULL;

                /* We can't depend on nrefs being == 1 here */
                if (--dqp->q_nrefs == 0) {
                        xfs_dqtrace_entry(dqp, "DQPUT: ON FREELIST");
                        /*
                         * insert at end of the freelist.
                         */
                        XQM_FREELIST_INSERT(&(xfs_Gqm->qm_dqfreelist), dqp);

                        /*
                         * If we just added a udquot to the freelist, then
                         * we want to release the gdquot reference that
                         * it (probably) has. Otherwise it'll keep the
                         * gdquot from getting reclaimed.
                         */
                        if ((gdqp = dqp->q_gdquot)) {
                                /*
                                 * Avoid a recursive dqput call
                                 */
                                xfs_dqlock(gdqp);
                                dqp->q_gdquot = NULL;
                        }

                        /* xfs_qm_freelist_print(&(xfs_Gqm->qm_dqfreelist),
                           "@@@@@++ Free list (after append) @@@@@+");
                           */
                }
                xfs_dqunlock(dqp);

                /*
                 * If we had a group quota inside the user quota as a hint,
                 * release it now.
                 */
                if (! gdqp)
                        break;
                dqp = gdqp;
        }
        xfs_qm_freelist_unlock(xfs_Gqm);
}

/*
 * Release a dquot. Flush it if dirty, then dqput() it.
 * dquot must not be locked.
 */
void
xfs_qm_dqrele(
        xfs_dquot_t     *dqp)
{
        ASSERT(dqp);
        xfs_dqtrace_entry(dqp, "DQRELE");

        xfs_dqlock(dqp);
        /*
         * We don't care to flush it if the dquot is dirty here.
         * That will create stutters that we want to avoid.
         * Instead we do a delayed write when we try to reclaim
         * a dirty dquot. Also xfs_sync will take part of the burden...
         */
        xfs_qm_dqput(dqp);
}


/*
 * Write a modified dquot to disk.
 * The dquot must be locked and the flush lock too taken by caller.
 * The flush lock will not be unlocked until the dquot reaches the disk,
 * but the dquot is free to be unlocked and modified by the caller
 * in the interim. Dquot is still locked on return. This behavior is
 * identical to that of inodes.
 */
int
xfs_qm_dqflush(
        xfs_dquot_t             *dqp,
        uint                    flags)
{
        xfs_mount_t             *mp;
        xfs_buf_t               *bp;
        xfs_disk_dquot_t        *ddqp;
        int                     error;
        SPLDECL(s);

        ASSERT(XFS_DQ_IS_LOCKED(dqp));
        ASSERT(XFS_DQ_IS_FLUSH_LOCKED(dqp));
        xfs_dqtrace_entry(dqp, "DQFLUSH");

        /*
         * If not dirty, nada.
         */
        if (!XFS_DQ_IS_DIRTY(dqp)) {
                xfs_dqfunlock(dqp);
                return (0);
        }

        /*
         * Cant flush a pinned dquot. Wait for it.
         */
        xfs_qm_dqunpin_wait(dqp);

        /*
         * This may have been unpinned because the filesystem is shutting
         * down forcibly. If that's the case we must not write this dquot
         * to disk, because the log record didn't make it to disk!
         */
        if (XFS_FORCED_SHUTDOWN(dqp->q_mount)) {
                dqp->dq_flags &= ~(XFS_DQ_DIRTY);
                xfs_dqfunlock(dqp);
                return XFS_ERROR(EIO);
        }

        /*
         * Get the buffer containing the on-disk dquot
         * We don't need a transaction envelope because we know that the
         * the ondisk-dquot has already been allocated for.
         */
        if ((error = xfs_qm_dqtobp(NULL, dqp, &ddqp, &bp, XFS_QMOPT_DOWARN))) {
                xfs_dqtrace_entry(dqp, "DQTOBP FAIL");
                ASSERT(error != ENOENT);
                /*
                 * Quotas could have gotten turned off (ESRCH)
                 */
                xfs_dqfunlock(dqp);
                return (error);
        }

        if (xfs_qm_dqcheck(&dqp->q_core, INT_GET(ddqp->d_id, ARCH_CONVERT), 0, XFS_QMOPT_DOWARN,
                           "dqflush (incore copy)")) {
                xfs_force_shutdown(dqp->q_mount, XFS_CORRUPT_INCORE);
                return XFS_ERROR(EIO);
        }

        /* This is the only portion of data that needs to persist */
        memcpy(ddqp, &(dqp->q_core), sizeof(xfs_disk_dquot_t));

        /*
         * Clear the dirty field and remember the flush lsn for later use.
         */
        dqp->dq_flags &= ~(XFS_DQ_DIRTY);
        mp = dqp->q_mount;

        /* lsn is 64 bits */
        AIL_LOCK(mp, s);
        dqp->q_logitem.qli_flush_lsn = dqp->q_logitem.qli_item.li_lsn;
        AIL_UNLOCK(mp, s);

        /*
         * Attach an iodone routine so that we can remove this dquot from the
         * AIL and release the flush lock once the dquot is synced to disk.
         */
        xfs_buf_attach_iodone(bp, (void(*)(xfs_buf_t *, xfs_log_item_t *))
                              xfs_qm_dqflush_done, &(dqp->q_logitem.qli_item));
        /*
         * If the buffer is pinned then push on the log so we won't
         * get stuck waiting in the write for too long.
         */
        if (XFS_BUF_ISPINNED(bp)) {
                xfs_dqtrace_entry(dqp, "DQFLUSH LOG FORCE");
                xfs_log_force(mp, (xfs_lsn_t)0, XFS_LOG_FORCE);
        }

        if (flags & XFS_QMOPT_DELWRI) {
                xfs_bdwrite(mp, bp);
        } else if (flags & XFS_QMOPT_ASYNC) {
                xfs_bawrite(mp, bp);
        } else {
                error = xfs_bwrite(mp, bp);
        }
        xfs_dqtrace_entry(dqp, "DQFLUSH END");
        /*
         * dqp is still locked, but caller is free to unlock it now.
         */
        return (error);

}

/*
 * This is the dquot flushing I/O completion routine.  It is called
 * from interrupt level when the buffer containing the dquot is
 * flushed to disk.  It is responsible for removing the dquot logitem
 * from the AIL if it has not been re-logged, and unlocking the dquot's
 * flush lock. This behavior is very similar to that of inodes..
 */
/*ARGSUSED*/
STATIC void
xfs_qm_dqflush_done(
        xfs_buf_t               *bp,
        xfs_dq_logitem_t        *qip)
{
        xfs_dquot_t             *dqp;
        SPLDECL(s);

        dqp = qip->qli_dquot;

        /*
         * We only want to pull the item from the AIL if its
         * location in the log has not changed since we started the flush.
         * Thus, we only bother if the dquot's lsn has
         * not changed. First we check the lsn outside the lock
         * since it's cheaper, and then we recheck while
         * holding the lock before removing the dquot from the AIL.
         */
        if ((qip->qli_item.li_flags & XFS_LI_IN_AIL) &&
            qip->qli_item.li_lsn == qip->qli_flush_lsn) {

                AIL_LOCK(dqp->q_mount, s);
                /*
                 * xfs_trans_delete_ail() drops the AIL lock.
                 */
                if (qip->qli_item.li_lsn == qip->qli_flush_lsn)
                        xfs_trans_delete_ail(dqp->q_mount,
                                             (xfs_log_item_t*)qip, s);
                else
                        AIL_UNLOCK(dqp->q_mount, s);
        }

        /*
         * Release the dq's flush lock since we're done with it.
         */
        xfs_dqfunlock(dqp);
}


int
xfs_qm_dqflock_nowait(
        xfs_dquot_t *dqp)
{
        int locked;

        locked = cpsema(&((dqp)->q_flock));

        /* XXX ifdef these out */
        if (locked)
                (dqp)->dq_flags |= XFS_DQ_FLOCKED;
        return (locked);
}


int
xfs_qm_dqlock_nowait(
        xfs_dquot_t *dqp)
{
        return (mutex_trylock(&((dqp)->q_qlock)));
}

void
xfs_dqlock(
        xfs_dquot_t *dqp)
{
        mutex_lock(&(dqp->q_qlock), PINOD);
}

void
xfs_dqunlock(
        xfs_dquot_t *dqp)
{
        mutex_unlock(&(dqp->q_qlock));
        if (dqp->q_logitem.qli_dquot == dqp) {
                /* Once was dqp->q_mount, but might just have been cleared */
                xfs_trans_unlocked_item(dqp->q_logitem.qli_item.li_mountp,
                                        (xfs_log_item_t*)&(dqp->q_logitem));
        }
}


void
xfs_dqunlock_nonotify(
        xfs_dquot_t *dqp)
{
        mutex_unlock(&(dqp->q_qlock));
}

void
xfs_dqlock2(
        xfs_dquot_t     *d1,
        xfs_dquot_t     *d2)
{
        if (d1 && d2) {
                ASSERT(d1 != d2);
                if (INT_GET(d1->q_core.d_id, ARCH_CONVERT) > INT_GET(d2->q_core.d_id, ARCH_CONVERT)) {
                        xfs_dqlock(d2);
                        xfs_dqlock(d1);
                } else {
                        xfs_dqlock(d1);
                        xfs_dqlock(d2);
                }
        } else {
                if (d1) {
                        xfs_dqlock(d1);
                } else if (d2) {
                        xfs_dqlock(d2);
                }
        }
}


/*
 * Take a dquot out of the mount's dqlist as well as the hashlist.
 * This is called via unmount as well as quotaoff, and the purge
 * will always succeed unless there are soft (temp) references
 * outstanding.
 *
 * This returns 0 if it was purged, 1 if it wasn't. It's not an error code
 * that we're returning! XXXsup - not cool.
 */
/* ARGSUSED */
int
xfs_qm_dqpurge(
        xfs_dquot_t     *dqp,
        uint            flags)
{
        xfs_dqhash_t    *thishash;
        xfs_mount_t     *mp;

        mp = dqp->q_mount;

        ASSERT(XFS_QM_IS_MPLIST_LOCKED(mp));
        ASSERT(XFS_DQ_IS_HASH_LOCKED(dqp->q_hash));

        xfs_dqlock(dqp);
        /*
         * We really can't afford to purge a dquot that is
         * referenced, because these are hard refs.
         * It shouldn't happen in general because we went thru _all_ inodes in
         * dqrele_all_inodes before calling this and didn't let the mountlock go.
         * However it is possible that we have dquots with temporary
         * references that are not attached to an inode. e.g. see xfs_setattr().
         */
        if (dqp->q_nrefs != 0) {
                xfs_dqunlock(dqp);
                XFS_DQ_HASH_UNLOCK(dqp->q_hash);
                return (1);
        }

        ASSERT(XFS_DQ_IS_ON_FREELIST(dqp));

        /*
         * If we're turning off quotas, we have to make sure that, for
         * example, we don't delete quota disk blocks while dquots are
         * in the process of getting written to those disk blocks.
         * This dquot might well be on AIL, and we can't leave it there
         * if we're turning off quotas. Basically, we need this flush
         * lock, and are willing to block on it.
         */
        if (! xfs_qm_dqflock_nowait(dqp)) {
                /*
                 * Block on the flush lock after nudging dquot buffer,
                 * if it is incore.
                 */
                xfs_qm_dqflock_pushbuf_wait(dqp);
        }

        /*
         * XXXIf we're turning this type of quotas off, we don't care
         * about the dirty metadata sitting in this dquot. OTOH, if
         * we're unmounting, we do care, so we flush it and wait.
         */
        if (XFS_DQ_IS_DIRTY(dqp)) {
                xfs_dqtrace_entry(dqp, "DQPURGE ->DQFLUSH: DQDIRTY");
                /* dqflush unlocks dqflock */
                /*
                 * Given that dqpurge is a very rare occurrence, it is OK
                 * that we're holding the hashlist and mplist locks
                 * across the disk write. But, ... XXXsup
                 *
                 * We don't care about getting disk errors here. We need
                 * to purge this dquot anyway, so we go ahead regardless.
                 */
                (void) xfs_qm_dqflush(dqp, XFS_QMOPT_SYNC);
                xfs_dqflock(dqp);
        }
        ASSERT(dqp->q_pincount == 0);
        ASSERT(XFS_FORCED_SHUTDOWN(mp) ||
               !(dqp->q_logitem.qli_item.li_flags & XFS_LI_IN_AIL));

        thishash = dqp->q_hash;
        XQM_HASHLIST_REMOVE(thishash, dqp);
        XQM_MPLIST_REMOVE(&(XFS_QI_MPL_LIST(mp)), dqp);
        /*
         * XXX Move this to the front of the freelist, if we can get the
         * freelist lock.
         */
        ASSERT(XFS_DQ_IS_ON_FREELIST(dqp));

        dqp->q_mount = NULL;
        dqp->q_hash = NULL;
        dqp->dq_flags = XFS_DQ_INACTIVE;
        memset(&dqp->q_core, 0, sizeof(dqp->q_core));
        xfs_dqfunlock(dqp);
        xfs_dqunlock(dqp);
        XFS_DQ_HASH_UNLOCK(thishash);
        return (0);
}


#ifdef QUOTADEBUG
void
xfs_qm_dqprint(xfs_dquot_t *dqp)
{
        cmn_err(CE_DEBUG, "-----------KERNEL DQUOT----------------");
        cmn_err(CE_DEBUG, "---- dquotID =  %d",
                (int)INT_GET(dqp->q_core.d_id, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- type    =  %s",
                XFS_QM_ISUDQ(dqp) ? "USR" : "GRP");
        cmn_err(CE_DEBUG, "---- fs      =  0x%p", dqp->q_mount);
        cmn_err(CE_DEBUG, "---- blkno   =  0x%x", (int) dqp->q_blkno);
        cmn_err(CE_DEBUG, "---- boffset =  0x%x", (int) dqp->q_bufoffset);
        cmn_err(CE_DEBUG, "---- blkhlimit =  %Lu (0x%x)",
                INT_GET(dqp->q_core.d_blk_hardlimit, ARCH_CONVERT),
                (int) INT_GET(dqp->q_core.d_blk_hardlimit, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- blkslimit =  %Lu (0x%x)",
                INT_GET(dqp->q_core.d_blk_softlimit, ARCH_CONVERT),
                (int)INT_GET(dqp->q_core.d_blk_softlimit, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- inohlimit =  %Lu (0x%x)",
                INT_GET(dqp->q_core.d_ino_hardlimit, ARCH_CONVERT),
                (int)INT_GET(dqp->q_core.d_ino_hardlimit, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- inoslimit =  %Lu (0x%x)",
                INT_GET(dqp->q_core.d_ino_softlimit, ARCH_CONVERT),
                (int)INT_GET(dqp->q_core.d_ino_softlimit, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- bcount  =  %Lu (0x%x)",
                INT_GET(dqp->q_core.d_bcount, ARCH_CONVERT),
                (int)INT_GET(dqp->q_core.d_bcount, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- icount  =  %Lu (0x%x)",
                INT_GET(dqp->q_core.d_icount, ARCH_CONVERT),
                (int)INT_GET(dqp->q_core.d_icount, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- btimer  =  %d",
                (int)INT_GET(dqp->q_core.d_btimer, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---- itimer  =  %d",
                (int)INT_GET(dqp->q_core.d_itimer, ARCH_CONVERT));
        cmn_err(CE_DEBUG, "---------------------------");
}
#endif

/*
 * Give the buffer a little push if it is incore and
 * wait on the flush lock.
 */
void
xfs_qm_dqflock_pushbuf_wait(
        xfs_dquot_t     *dqp)
{
        xfs_buf_t       *bp;

        /*
         * 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.
         */
        bp = xfs_incore(dqp->q_mount->m_ddev_targp, dqp->q_blkno,
                    XFS_QI_DQCHUNKLEN(dqp->q_mount),
                    XFS_INCORE_TRYLOCK);
        if (bp != NULL) {
                if (XFS_BUF_ISDELAYWRITE(bp)) {
                        if (XFS_BUF_ISPINNED(bp)) {
                                xfs_log_force(dqp->q_mount,
                                              (xfs_lsn_t)0,
                                              XFS_LOG_FORCE);
                        }
                        xfs_bawrite(dqp->q_mount, bp);
                } else {
                        xfs_buf_relse(bp);
                }
        }
        xfs_dqflock(dqp);
}