xfs_dquot.c

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/*
 * 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 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_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_alloc.h"
#include "xfs_quota.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_rtalloc.h"
#include "xfs_error.h"
#include "xfs_itable.h"
#include "xfs_attr.h"
#include "xfs_buf_item.h"
#include "xfs_trans_space.h"
#include "xfs_trans_priv.h"
#include "xfs_qm.h"
#include "xfs_trace.h"

/*
 * Lock order:
 *
 * ip->i_lock
 *   qi->qi_tree_lock
 *     dquot->q_qlock (xfs_dqlock() and friends)
 *       dquot->q_flush (xfs_dqflock() and friends)
 *       qi->qi_lru_lock
 *
 * If two dquots need to be locked the order is user before group/project,
 * otherwise by the lowest id first, see xfs_dqlock2.
 */

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

struct kmem_zone        *xfs_qm_dqtrxzone;
static struct kmem_zone     *xfs_qm_dqzone;

static struct lock_class_key xfs_dquot_other_class;

/*
 * This is called to free all the memory associated with a dquot
 */
void
xfs_qm_dqdestroy(
    xfs_dquot_t *dqp)
{
    ASSERT(list_empty(&dqp->q_lru));

    mutex_destroy(&dqp->q_qlock);
    kmem_zone_free(xfs_qm_dqzone, dqp);

    XFS_STATS_DEC(xs_qm_dquot);
}

/*
 * 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(d->d_id);

    if (q->qi_bsoftlimit && !d->d_blk_softlimit)
        d->d_blk_softlimit = cpu_to_be64(q->qi_bsoftlimit);
    if (q->qi_bhardlimit && !d->d_blk_hardlimit)
        d->d_blk_hardlimit = cpu_to_be64(q->qi_bhardlimit);
    if (q->qi_isoftlimit && !d->d_ino_softlimit)
        d->d_ino_softlimit = cpu_to_be64(q->qi_isoftlimit);
    if (q->qi_ihardlimit && !d->d_ino_hardlimit)
        d->d_ino_hardlimit = cpu_to_be64(q->qi_ihardlimit);
    if (q->qi_rtbsoftlimit && !d->d_rtb_softlimit)
        d->d_rtb_softlimit = cpu_to_be64(q->qi_rtbsoftlimit);
    if (q->qi_rtbhardlimit && !d->d_rtb_hardlimit)
        d->d_rtb_hardlimit = cpu_to_be64(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.  They do
 * get reset to zero, however, when we find the count to be under
 * the soft limit (they are only ever set non-zero via userspace).
 */
void
xfs_qm_adjust_dqtimers(
    xfs_mount_t     *mp,
    xfs_disk_dquot_t    *d)
{
    ASSERT(d->d_id);

#ifdef DEBUG
    if (d->d_blk_hardlimit)
        ASSERT(be64_to_cpu(d->d_blk_softlimit) <=
               be64_to_cpu(d->d_blk_hardlimit));
    if (d->d_ino_hardlimit)
        ASSERT(be64_to_cpu(d->d_ino_softlimit) <=
               be64_to_cpu(d->d_ino_hardlimit));
    if (d->d_rtb_hardlimit)
        ASSERT(be64_to_cpu(d->d_rtb_softlimit) <=
               be64_to_cpu(d->d_rtb_hardlimit));
#endif

    if (!d->d_btimer) {
        if ((d->d_blk_softlimit &&
             (be64_to_cpu(d->d_bcount) >
              be64_to_cpu(d->d_blk_softlimit))) ||
            (d->d_blk_hardlimit &&
             (be64_to_cpu(d->d_bcount) >
              be64_to_cpu(d->d_blk_hardlimit)))) {
            d->d_btimer = cpu_to_be32(get_seconds() +
                    mp->m_quotainfo->qi_btimelimit);
        } else {
            d->d_bwarns = 0;
        }
    } else {
        if ((!d->d_blk_softlimit ||
             (be64_to_cpu(d->d_bcount) <=
              be64_to_cpu(d->d_blk_softlimit))) &&
            (!d->d_blk_hardlimit ||
            (be64_to_cpu(d->d_bcount) <=
             be64_to_cpu(d->d_blk_hardlimit)))) {
            d->d_btimer = 0;
        }
    }

    if (!d->d_itimer) {
        if ((d->d_ino_softlimit &&
             (be64_to_cpu(d->d_icount) >
              be64_to_cpu(d->d_ino_softlimit))) ||
            (d->d_ino_hardlimit &&
             (be64_to_cpu(d->d_icount) >
              be64_to_cpu(d->d_ino_hardlimit)))) {
            d->d_itimer = cpu_to_be32(get_seconds() +
                    mp->m_quotainfo->qi_itimelimit);
        } else {
            d->d_iwarns = 0;
        }
    } else {
        if ((!d->d_ino_softlimit ||
             (be64_to_cpu(d->d_icount) <=
              be64_to_cpu(d->d_ino_softlimit)))  &&
            (!d->d_ino_hardlimit ||
             (be64_to_cpu(d->d_icount) <=
              be64_to_cpu(d->d_ino_hardlimit)))) {
            d->d_itimer = 0;
        }
    }

    if (!d->d_rtbtimer) {
        if ((d->d_rtb_softlimit &&
             (be64_to_cpu(d->d_rtbcount) >
              be64_to_cpu(d->d_rtb_softlimit))) ||
            (d->d_rtb_hardlimit &&
             (be64_to_cpu(d->d_rtbcount) >
              be64_to_cpu(d->d_rtb_hardlimit)))) {
            d->d_rtbtimer = cpu_to_be32(get_seconds() +
                    mp->m_quotainfo->qi_rtbtimelimit);
        } else {
            d->d_rtbwarns = 0;
        }
    } else {
        if ((!d->d_rtb_softlimit ||
             (be64_to_cpu(d->d_rtbcount) <=
              be64_to_cpu(d->d_rtb_softlimit))) &&
            (!d->d_rtb_hardlimit ||
             (be64_to_cpu(d->d_rtbcount) <=
              be64_to_cpu(d->d_rtb_hardlimit)))) {
            d->d_rtbtimer = 0;
        }
    }
}

/*
 * 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)
{
    struct xfs_quotainfo    *q = mp->m_quotainfo;
    xfs_dqblk_t *d;
    int     curid, i;

    ASSERT(tp);
    ASSERT(xfs_buf_islocked(bp));

    d = bp->b_addr;

    /*
     * ID of the first dquot in the block - id's are zero based.
     */
    curid = id - (id % q->qi_dqperchunk);
    ASSERT(curid >= 0);
    memset(d, 0, BBTOB(q->qi_dqchunklen));
    for (i = 0; i < q->qi_dqperchunk; i++, d++, curid++) {
        d->dd_diskdq.d_magic = cpu_to_be16(XFS_DQUOT_MAGIC);
        d->dd_diskdq.d_version = XFS_DQUOT_VERSION;
        d->dd_diskdq.d_id = cpu_to_be32(curid);
        d->dd_diskdq.d_flags = type;
    }

    xfs_trans_dquot_buf(tp, bp,
                (type & XFS_DQ_USER ? XFS_BLF_UDQUOT_BUF :
                ((type & XFS_DQ_PROJ) ? XFS_BLF_PDQUOT_BUF :
                 XFS_BLF_GDQUOT_BUF)));
    xfs_trans_log_buf(tp, bp, 0, BBTOB(q->qi_dqchunklen) - 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 **tpp,
    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;
    xfs_trans_t *tp = *tpp;

    ASSERT(tp != NULL);

    trace_xfs_dqalloc(dqp);

    /*
     * 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_this_quota_on(dqp->q_mount, dqp->dq_flags)) {
        xfs_iunlock(quotip, XFS_ILOCK_EXCL);
        return (ESRCH);
    }

    xfs_trans_ijoin(tp, quotip, XFS_ILOCK_EXCL);
    nmaps = 1;
    error = xfs_bmapi_write(tp, quotip, offset_fsb,
                XFS_DQUOT_CLUSTER_SIZE_FSB, XFS_BMAPI_METADATA,
                &firstblock, XFS_QM_DQALLOC_SPACE_RES(mp),
                &map, &nmaps, &flist);
    if (error)
        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,
                   mp->m_quotainfo->qi_dqchunklen,
                   0);

    error = xfs_buf_geterror(bp);
    if (error)
        goto error1;

    /*
     * Make a chunk of dquots out of this buffer and log
     * the entire thing.
     */
    xfs_qm_init_dquot_blk(tp, mp, be32_to_cpu(dqp->q_core.d_id),
                  dqp->dq_flags & XFS_DQ_ALLTYPES, bp);

    /*
     * xfs_bmap_finish() may commit the current transaction and
     * start a second transaction if the freelist is not empty.
     *
     * Since we still want to modify this buffer, we need to
     * ensure that the buffer is not released on commit of
     * the first transaction and ensure the buffer is added to the
     * second transaction.
     *
     * If there is only one transaction then don't stop the buffer
     * from being released when it commits later on.
     */

    xfs_trans_bhold(tp, bp);

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

    if (committed) {
        tp = *tpp;
        xfs_trans_bjoin(tp, bp);
    } else {
        xfs_trans_bhold_release(tp, bp);
    }

    *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     **tpp,
    xfs_dquot_t     *dqp,
    xfs_disk_dquot_t    **O_ddpp,
    xfs_buf_t       **O_bpp,
    uint            flags)
{
    xfs_bmbt_irec_t map;
    int     nmaps = 1, error;
    xfs_buf_t   *bp;
    xfs_inode_t *quotip = XFS_DQ_TO_QIP(dqp);
    xfs_mount_t *mp = dqp->q_mount;
    xfs_disk_dquot_t *ddq;
    xfs_dqid_t  id = be32_to_cpu(dqp->q_core.d_id);
    xfs_trans_t *tp = (tpp ? *tpp : NULL);

    dqp->q_fileoffset = (xfs_fileoff_t)id / mp->m_quotainfo->qi_dqperchunk;

    xfs_ilock(quotip, XFS_ILOCK_SHARED);
    if (!xfs_this_quota_on(dqp->q_mount, dqp->dq_flags)) {
        /*
         * Return if this type of quotas is turned off while we
         * didn't have the quota inode lock.
         */
        xfs_iunlock(quotip, XFS_ILOCK_SHARED);
        return ESRCH;
    }

    /*
     * Find the block map; no allocations yet
     */
    error = xfs_bmapi_read(quotip, dqp->q_fileoffset,
                   XFS_DQUOT_CLUSTER_SIZE_FSB, &map, &nmaps, 0);

    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 % mp->m_quotainfo->qi_dqperchunk) *
        sizeof(xfs_dqblk_t);

    ASSERT(map.br_startblock != DELAYSTARTBLOCK);
    if (map.br_startblock == HOLESTARTBLOCK) {
        /*
         * We don't allocate unless we're asked to
         */
        if (!(flags & XFS_QMOPT_DQALLOC))
            return ENOENT;

        ASSERT(tp);
        error = xfs_qm_dqalloc(tpp, mp, dqp, quotip,
                    dqp->q_fileoffset, &bp);
        if (error)
            return error;
        tp = *tpp;
    } else {
        trace_xfs_dqtobp_read(dqp);

        /*
         * 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);

        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                       dqp->q_blkno,
                       mp->m_quotainfo->qi_dqchunklen,
                       0, &bp);
        if (error || !bp)
            return XFS_ERROR(error);
    }

    ASSERT(xfs_buf_islocked(bp));

    /*
     * calculate the location of the dquot inside the buffer.
     */
    ddq = bp->b_addr + dqp->q_bufoffset;

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

    *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.
 *
 * If XFS_QMOPT_DQALLOC is set, allocate a dquot on disk if it needed.
 */
int
xfs_qm_dqread(
    struct xfs_mount    *mp,
    xfs_dqid_t      id,
    uint            type,
    uint            flags,
    struct xfs_dquot    **O_dqpp)
{
    struct xfs_dquot    *dqp;
    struct xfs_disk_dquot   *ddqp;
    struct xfs_buf      *bp;
    struct xfs_trans    *tp = NULL;
    int         error;
    int         cancelflags = 0;


    dqp = kmem_zone_zalloc(xfs_qm_dqzone, KM_SLEEP);

    dqp->dq_flags = type;
    dqp->q_core.d_id = cpu_to_be32(id);
    dqp->q_mount = mp;
    INIT_LIST_HEAD(&dqp->q_lru);
    mutex_init(&dqp->q_qlock);
    init_waitqueue_head(&dqp->q_pinwait);

    /*
     * Because we want to use a counting completion, complete
     * the flush completion once to allow a single access to
     * the flush completion without blocking.
     */
    init_completion(&dqp->q_flush);
    complete(&dqp->q_flush);

    /*
     * Make sure group quotas have a different lock class than user
     * quotas.
     */
    if (!(type & XFS_DQ_USER))
        lockdep_set_class(&dqp->q_qlock, &xfs_dquot_other_class);

    XFS_STATS_INC(xs_qm_dquot);

    trace_xfs_dqread(dqp);

    if (flags & XFS_QMOPT_DQALLOC) {
        tp = xfs_trans_alloc(mp, XFS_TRANS_QM_DQALLOC);
        error = xfs_trans_reserve(tp, XFS_QM_DQALLOC_SPACE_RES(mp),
                XFS_WRITE_LOG_RES(mp) +
                /*
                 * Round the chunklen up to the next multiple
                 * of 128 (buf log item chunk size)).
                 */
                BBTOB(mp->m_quotainfo->qi_dqchunklen) - 1 + 128,
                0,
                XFS_TRANS_PERM_LOG_RES,
                XFS_WRITE_LOG_COUNT);
        if (error)
            goto error1;
        cancelflags = XFS_TRANS_RELEASE_LOG_RES;
    }

    /*
     * get a pointer to the on-disk dquot and the buffer containing it
     * dqp already knows its own type (GROUP/USER).
     */
    error = xfs_qm_dqtobp(&tp, dqp, &ddqp, &bp, flags);
    if (error) {
        /*
         * This can happen if quotas got turned off (ESRCH),
         * or if the dquot didn't exist on disk and we ask to
         * allocate (ENOENT).
         */
        trace_xfs_dqread_fail(dqp);
        cancelflags |= XFS_TRANS_ABORT;
        goto error1;
    }

    /* copy everything from disk dquot to the incore dquot */
    memcpy(&dqp->q_core, ddqp, sizeof(xfs_disk_dquot_t));
    xfs_qm_dquot_logitem_init(dqp);

    /*
     * Reservation counters are defined as reservation plus current usage
     * to avoid having to add every time.
     */
    dqp->q_res_bcount = be64_to_cpu(ddqp->d_bcount);
    dqp->q_res_icount = be64_to_cpu(ddqp->d_icount);
    dqp->q_res_rtbcount = be64_to_cpu(ddqp->d_rtbcount);

    /* Mark the buf so that this will stay incore a little longer */
    xfs_buf_set_ref(bp, 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_islocked(bp));
    xfs_trans_brelse(tp, bp);

    if (tp) {
        error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
        if (error)
            goto error0;
    }

    *O_dqpp = dqp;
    return error;

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

/*
 * 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,   /* uid/projid/gid depending on type */
    uint        type,     /* XFS_DQ_USER/XFS_DQ_PROJ/XFS_DQ_GROUP */
    uint        flags,    /* DQALLOC, DQSUSER, DQREPAIR, DOWARN */
    xfs_dquot_t **O_dqpp) /* OUT : locked incore dquot */
{
    struct xfs_quotainfo    *qi = mp->m_quotainfo;
    struct radix_tree_root *tree = XFS_DQUOT_TREE(qi, type);
    struct xfs_dquot    *dqp;
    int         error;

    ASSERT(XFS_IS_QUOTA_RUNNING(mp));
    if ((! XFS_IS_UQUOTA_ON(mp) && type == XFS_DQ_USER) ||
        (! XFS_IS_PQUOTA_ON(mp) && type == XFS_DQ_PROJ) ||
        (! XFS_IS_GQUOTA_ON(mp) && type == XFS_DQ_GROUP)) {
        return (ESRCH);
    }

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

    ASSERT(type == XFS_DQ_USER ||
           type == XFS_DQ_PROJ ||
           type == XFS_DQ_GROUP);
    if (ip) {
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(xfs_inode_dquot(ip, type) == NULL);
    }
#endif

restart:
    mutex_lock(&qi->qi_tree_lock);
    dqp = radix_tree_lookup(tree, id);
    if (dqp) {
        xfs_dqlock(dqp);
        if (dqp->dq_flags & XFS_DQ_FREEING) {
            xfs_dqunlock(dqp);
            mutex_unlock(&qi->qi_tree_lock);
            trace_xfs_dqget_freeing(dqp);
            delay(1);
            goto restart;
        }

        dqp->q_nrefs++;
        mutex_unlock(&qi->qi_tree_lock);

        trace_xfs_dqget_hit(dqp);
        XFS_STATS_INC(xs_qm_dqcachehits);
        *O_dqpp = dqp;
        return 0;
    }
    mutex_unlock(&qi->qi_tree_lock);
    XFS_STATS_INC(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);

    error = xfs_qm_dqread(mp, id, type, flags, &dqp);

    if (ip)
        xfs_ilock(ip, XFS_ILOCK_EXCL);

    if (error)
        return error;

    if (ip) {
        /*
         * A dquot could be attached to this inode by now, since
         * we had dropped the ilock.
         */
        if (xfs_this_quota_on(mp, type)) {
            struct xfs_dquot    *dqp1;

            dqp1 = xfs_inode_dquot(ip, type);
            if (dqp1) {
                xfs_qm_dqdestroy(dqp);
                dqp = dqp1;
                xfs_dqlock(dqp);
                goto dqret;
            }
        } else {
            /* inode stays locked on return */
            xfs_qm_dqdestroy(dqp);
            return XFS_ERROR(ESRCH);
        }
    }

    mutex_lock(&qi->qi_tree_lock);
    error = -radix_tree_insert(tree, id, dqp);
    if (unlikely(error)) {
        WARN_ON(error != EEXIST);

        /*
         * Duplicate found. Just throw away the new dquot and start
         * over.
         */
        mutex_unlock(&qi->qi_tree_lock);
        trace_xfs_dqget_dup(dqp);
        xfs_qm_dqdestroy(dqp);
        XFS_STATS_INC(xs_qm_dquot_dups);
        goto restart;
    }

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

    qi->qi_dquots++;
    mutex_unlock(&qi->qi_tree_lock);

 dqret:
    ASSERT((ip == NULL) || xfs_isilocked(ip, XFS_ILOCK_EXCL));
    trace_xfs_dqget_miss(dqp);
    *O_dqpp = dqp;
    return (0);
}


STATIC void
xfs_qm_dqput_final(
    struct xfs_dquot    *dqp)
{
    struct xfs_quotainfo    *qi = dqp->q_mount->m_quotainfo;
    struct xfs_dquot    *gdqp;

    trace_xfs_dqput_free(dqp);

    mutex_lock(&qi->qi_lru_lock);
    if (list_empty(&dqp->q_lru)) {
        list_add_tail(&dqp->q_lru, &qi->qi_lru_list);
        qi->qi_lru_count++;
        XFS_STATS_INC(xs_qm_dquot_unused);
    }
    mutex_unlock(&qi->qi_lru_lock);

    /*
     * 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.
     */
    gdqp = dqp->q_gdquot;
    if (gdqp) {
        xfs_dqlock(gdqp);
        dqp->q_gdquot = NULL;
    }
    xfs_dqunlock(dqp);

    /*
     * If we had a group quota hint, release it now.
     */
    if (gdqp)
        xfs_qm_dqput(gdqp);
}

/*
 * 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(
    struct xfs_dquot    *dqp)
{
    ASSERT(dqp->q_nrefs > 0);
    ASSERT(XFS_DQ_IS_LOCKED(dqp));

    trace_xfs_dqput(dqp);

    if (--dqp->q_nrefs > 0)
        xfs_dqunlock(dqp);
    else
        xfs_qm_dqput_final(dqp);
}

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

    trace_xfs_dqrele(dqp);

    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);
}

/*
 * 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..
 */
STATIC void
xfs_qm_dqflush_done(
    struct xfs_buf      *bp,
    struct xfs_log_item *lip)
{
    xfs_dq_logitem_t    *qip = (struct xfs_dq_logitem *)lip;
    xfs_dquot_t     *dqp = qip->qli_dquot;
    struct xfs_ail      *ailp = lip->li_ailp;

    /*
     * 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 ((lip->li_flags & XFS_LI_IN_AIL) &&
        lip->li_lsn == qip->qli_flush_lsn) {

        /* xfs_trans_ail_delete() drops the AIL lock. */
        spin_lock(&ailp->xa_lock);
        if (lip->li_lsn == qip->qli_flush_lsn)
            xfs_trans_ail_delete(ailp, lip, SHUTDOWN_CORRUPT_INCORE);
        else
            spin_unlock(&ailp->xa_lock);
    }

    /*
     * Release the dq's flush lock since we're done with it.
     */
    xfs_dqfunlock(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(
    struct xfs_dquot    *dqp,
    struct xfs_buf      **bpp)
{
    struct xfs_mount    *mp = dqp->q_mount;
    struct xfs_buf      *bp;
    struct xfs_disk_dquot   *ddqp;
    int         error;

    ASSERT(XFS_DQ_IS_LOCKED(dqp));
    ASSERT(!completion_done(&dqp->q_flush));

    trace_xfs_dqflush(dqp);

    *bpp = NULL;

    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.
     *
     * We also have to remove the log item from the AIL in this case,
     * as we wait for an emptry AIL as part of the unmount process.
     */
    if (XFS_FORCED_SHUTDOWN(mp)) {
        struct xfs_log_item *lip = &dqp->q_logitem.qli_item;
        dqp->dq_flags &= ~XFS_DQ_DIRTY;

        spin_lock(&mp->m_ail->xa_lock);
        if (lip->li_flags & XFS_LI_IN_AIL)
            xfs_trans_ail_delete(mp->m_ail, lip,
                         SHUTDOWN_CORRUPT_INCORE);
        else
            spin_unlock(&mp->m_ail->xa_lock);
        error = XFS_ERROR(EIO);
        goto out_unlock;
    }

    /*
     * Get the buffer containing the on-disk dquot
     */
    error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp, dqp->q_blkno,
                   mp->m_quotainfo->qi_dqchunklen, 0, &bp);
    if (error)
        goto out_unlock;

    /*
     * Calculate the location of the dquot inside the buffer.
     */
    ddqp = bp->b_addr + dqp->q_bufoffset;

    /*
     * A simple sanity check in case we got a corrupted dquot..
     */
    error = xfs_qm_dqcheck(mp, &dqp->q_core, be32_to_cpu(ddqp->d_id), 0,
               XFS_QMOPT_DOWARN, "dqflush (incore copy)");
    if (error) {
        xfs_buf_relse(bp);
        xfs_dqfunlock(dqp);
        xfs_force_shutdown(mp, SHUTDOWN_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;

    xfs_trans_ail_copy_lsn(mp->m_ail, &dqp->q_logitem.qli_flush_lsn,
                    &dqp->q_logitem.qli_item.li_lsn);

    /*
     * 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, 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)) {
        trace_xfs_dqflush_force(dqp);
        xfs_log_force(mp, 0);
    }

    trace_xfs_dqflush_done(dqp);
    *bpp = bp;
    return 0;

out_unlock:
    xfs_dqfunlock(dqp);
    return XFS_ERROR(EIO);
}

/*
 * Lock two xfs_dquot structures.
 *
 * To avoid deadlocks we always lock the quota structure with
 * the lowerd id first.
 */
void
xfs_dqlock2(
    xfs_dquot_t *d1,
    xfs_dquot_t *d2)
{
    if (d1 && d2) {
        ASSERT(d1 != d2);
        if (be32_to_cpu(d1->q_core.d_id) >
            be32_to_cpu(d2->q_core.d_id)) {
            mutex_lock(&d2->q_qlock);
            mutex_lock_nested(&d1->q_qlock, XFS_QLOCK_NESTED);
        } else {
            mutex_lock(&d1->q_qlock);
            mutex_lock_nested(&d2->q_qlock, XFS_QLOCK_NESTED);
        }
    } else if (d1) {
        mutex_lock(&d1->q_qlock);
    } else if (d2) {
        mutex_lock(&d2->q_qlock);
    }
}

int __init
xfs_qm_init(void)
{
    xfs_qm_dqzone =
        kmem_zone_init(sizeof(struct xfs_dquot), "xfs_dquot");
    if (!xfs_qm_dqzone)
        goto out;

    xfs_qm_dqtrxzone =
        kmem_zone_init(sizeof(struct xfs_dquot_acct), "xfs_dqtrx");
    if (!xfs_qm_dqtrxzone)
        goto out_free_dqzone;

    return 0;

out_free_dqzone:
    kmem_zone_destroy(xfs_qm_dqzone);
out:
    return -ENOMEM;
}

void
xfs_qm_exit(void)
{
    kmem_zone_destroy(xfs_qm_dqtrxzone);
    kmem_zone_destroy(xfs_qm_dqzone);
}