xfs_qm.c

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

/*
 * The global quota manager. There is only one of these for the entire
 * system, _not_ one per file system. XQM keeps track of the overall
 * quota functionality, including maintaining the freelist and hash
 * tables of dquots.
 */
STATIC int  xfs_qm_init_quotainos(xfs_mount_t *);
STATIC int  xfs_qm_init_quotainfo(xfs_mount_t *);
STATIC int  xfs_qm_shake(struct shrinker *, struct shrink_control *);

/*
 * We use the batch lookup interface to iterate over the dquots as it
 * currently is the only interface into the radix tree code that allows
 * fuzzy lookups instead of exact matches.  Holding the lock over multiple
 * operations is fine as all callers are used either during mount/umount
 * or quotaoff.
 */
#define XFS_DQ_LOOKUP_BATCH 32

STATIC int
xfs_qm_dquot_walk(
    struct xfs_mount    *mp,
    int         type,
    int         (*execute)(struct xfs_dquot *dqp, void *data),
    void            *data)
{
    struct xfs_quotainfo    *qi = mp->m_quotainfo;
    struct radix_tree_root  *tree = XFS_DQUOT_TREE(qi, type);
    uint32_t        next_index;
    int         last_error = 0;
    int         skipped;
    int         nr_found;

restart:
    skipped = 0;
    next_index = 0;
    nr_found = 0;

    while (1) {
        struct xfs_dquot *batch[XFS_DQ_LOOKUP_BATCH];
        int     error = 0;
        int     i;

        mutex_lock(&qi->qi_tree_lock);
        nr_found = radix_tree_gang_lookup(tree, (void **)batch,
                    next_index, XFS_DQ_LOOKUP_BATCH);
        if (!nr_found) {
            mutex_unlock(&qi->qi_tree_lock);
            break;
        }

        for (i = 0; i < nr_found; i++) {
            struct xfs_dquot *dqp = batch[i];

            next_index = be32_to_cpu(dqp->q_core.d_id) + 1;

            error = execute(batch[i], data);
            if (error == EAGAIN) {
                skipped++;
                continue;
            }
            if (error && last_error != EFSCORRUPTED)
                last_error = error;
        }

        mutex_unlock(&qi->qi_tree_lock);

        /* bail out if the filesystem is corrupted.  */
        if (last_error == EFSCORRUPTED) {
            skipped = 0;
            break;
        }
    }

    if (skipped) {
        delay(1);
        goto restart;
    }

    return last_error;
}


/*
 * Purge a dquot from all tracking data structures and free it.
 */
STATIC int
xfs_qm_dqpurge(
    struct xfs_dquot    *dqp,
    void            *data)
{
    struct xfs_mount    *mp = dqp->q_mount;
    struct xfs_quotainfo    *qi = mp->m_quotainfo;
    struct xfs_dquot    *gdqp = NULL;

    xfs_dqlock(dqp);
    if ((dqp->dq_flags & XFS_DQ_FREEING) || dqp->q_nrefs != 0) {
        xfs_dqunlock(dqp);
        return EAGAIN;
    }

    /*
     * If this quota has a group hint attached, prepare for releasing it
     * now.
     */
    gdqp = dqp->q_gdquot;
    if (gdqp) {
        xfs_dqlock(gdqp);
        dqp->q_gdquot = NULL;
    }

    dqp->dq_flags |= XFS_DQ_FREEING;

    xfs_dqflock(dqp);

    /*
     * If we are 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)) {
        struct xfs_buf  *bp = NULL;
        int     error;

        /*
         * We don't care about getting disk errors here. We need
         * to purge this dquot anyway, so we go ahead regardless.
         */
        error = xfs_qm_dqflush(dqp, &bp);
        if (error) {
            xfs_warn(mp, "%s: dquot %p flush failed",
                __func__, dqp);
        } else {
            error = xfs_bwrite(bp);
            xfs_buf_relse(bp);
        }
        xfs_dqflock(dqp);
    }

    ASSERT(atomic_read(&dqp->q_pincount) == 0);
    ASSERT(XFS_FORCED_SHUTDOWN(mp) ||
           !(dqp->q_logitem.qli_item.li_flags & XFS_LI_IN_AIL));

    xfs_dqfunlock(dqp);
    xfs_dqunlock(dqp);

    radix_tree_delete(XFS_DQUOT_TREE(qi, dqp->q_core.d_flags),
              be32_to_cpu(dqp->q_core.d_id));
    qi->qi_dquots--;

    /*
     * We move dquots to the freelist as soon as their reference count
     * hits zero, so it really should be on the freelist here.
     */
    mutex_lock(&qi->qi_lru_lock);
    ASSERT(!list_empty(&dqp->q_lru));
    list_del_init(&dqp->q_lru);
    qi->qi_lru_count--;
    XFS_STATS_DEC(xs_qm_dquot_unused);
    mutex_unlock(&qi->qi_lru_lock);

    xfs_qm_dqdestroy(dqp);

    if (gdqp)
        xfs_qm_dqput(gdqp);
    return 0;
}

/*
 * Purge the dquot cache.
 */
void
xfs_qm_dqpurge_all(
    struct xfs_mount    *mp,
    uint            flags)
{
    if (flags & XFS_QMOPT_UQUOTA)
        xfs_qm_dquot_walk(mp, XFS_DQ_USER, xfs_qm_dqpurge, NULL);
    if (flags & XFS_QMOPT_GQUOTA)
        xfs_qm_dquot_walk(mp, XFS_DQ_GROUP, xfs_qm_dqpurge, NULL);
    if (flags & XFS_QMOPT_PQUOTA)
        xfs_qm_dquot_walk(mp, XFS_DQ_PROJ, xfs_qm_dqpurge, NULL);
}

/*
 * Just destroy the quotainfo structure.
 */
void
xfs_qm_unmount(
    struct xfs_mount    *mp)
{
    if (mp->m_quotainfo) {
        xfs_qm_dqpurge_all(mp, XFS_QMOPT_QUOTALL);
        xfs_qm_destroy_quotainfo(mp);
    }
}


/*
 * This is called from xfs_mountfs to start quotas and initialize all
 * necessary data structures like quotainfo.  This is also responsible for
 * running a quotacheck as necessary.  We are guaranteed that the superblock
 * is consistently read in at this point.
 *
 * If we fail here, the mount will continue with quota turned off. We don't
 * need to inidicate success or failure at all.
 */
void
xfs_qm_mount_quotas(
    xfs_mount_t *mp)
{
    int     error = 0;
    uint        sbf;

    /*
     * If quotas on realtime volumes is not supported, we disable
     * quotas immediately.
     */
    if (mp->m_sb.sb_rextents) {
        xfs_notice(mp, "Cannot turn on quotas for realtime filesystem");
        mp->m_qflags = 0;
        goto write_changes;
    }

    ASSERT(XFS_IS_QUOTA_RUNNING(mp));

    /*
     * Allocate the quotainfo structure inside the mount struct, and
     * create quotainode(s), and change/rev superblock if necessary.
     */
    error = xfs_qm_init_quotainfo(mp);
    if (error) {
        /*
         * We must turn off quotas.
         */
        ASSERT(mp->m_quotainfo == NULL);
        mp->m_qflags = 0;
        goto write_changes;
    }
    /*
     * If any of the quotas are not consistent, do a quotacheck.
     */
    if (XFS_QM_NEED_QUOTACHECK(mp)) {
        error = xfs_qm_quotacheck(mp);
        if (error) {
            /* Quotacheck failed and disabled quotas. */
            return;
        }
    }
    /* 
     * If one type of quotas is off, then it will lose its
     * quotachecked status, since we won't be doing accounting for
     * that type anymore.
     */
    if (!XFS_IS_UQUOTA_ON(mp))
        mp->m_qflags &= ~XFS_UQUOTA_CHKD;
    if (!(XFS_IS_GQUOTA_ON(mp) || XFS_IS_PQUOTA_ON(mp)))
        mp->m_qflags &= ~XFS_OQUOTA_CHKD;

 write_changes:
    /*
     * We actually don't have to acquire the m_sb_lock at all.
     * This can only be called from mount, and that's single threaded. XXX
     */
    spin_lock(&mp->m_sb_lock);
    sbf = mp->m_sb.sb_qflags;
    mp->m_sb.sb_qflags = mp->m_qflags & XFS_MOUNT_QUOTA_ALL;
    spin_unlock(&mp->m_sb_lock);

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

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

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

    /*
     * Release the quota inodes.
     */
    if (mp->m_quotainfo) {
        if (mp->m_quotainfo->qi_uquotaip) {
            IRELE(mp->m_quotainfo->qi_uquotaip);
            mp->m_quotainfo->qi_uquotaip = NULL;
        }
        if (mp->m_quotainfo->qi_gquotaip) {
            IRELE(mp->m_quotainfo->qi_gquotaip);
            mp->m_quotainfo->qi_gquotaip = NULL;
        }
    }
}

STATIC int
xfs_qm_dqattach_one(
    xfs_inode_t *ip,
    xfs_dqid_t  id,
    uint        type,
    uint        doalloc,
    xfs_dquot_t *udqhint, /* hint */
    xfs_dquot_t **IO_idqpp)
{
    xfs_dquot_t *dqp;
    int     error;

    ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
    error = 0;

    /*
     * See if we already have it in the inode itself. IO_idqpp is
     * &i_udquot or &i_gdquot. This made the code look weird, but
     * made the logic a lot simpler.
     */
    dqp = *IO_idqpp;
    if (dqp) {
        trace_xfs_dqattach_found(dqp);
        return 0;
    }

    /*
     * udqhint is the i_udquot field in inode, and is non-NULL only
     * when the type arg is group/project. Its purpose is to save a
     * lookup by dqid (xfs_qm_dqget) by caching a group dquot inside
     * the user dquot.
     */
    if (udqhint) {
        ASSERT(type == XFS_DQ_GROUP || type == XFS_DQ_PROJ);
        xfs_dqlock(udqhint);

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

            *IO_idqpp = xfs_qm_dqhold(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,
                 doalloc | XFS_QMOPT_DOWARN, &dqp);
    if (error)
        return error;

    trace_xfs_dqattach_get(dqp);

    /*
     * dqget may have dropped and re-acquired the ilock, but it guarantees
     * that the dquot returned is the one that should go in the inode.
     */
    *IO_idqpp = dqp;
    xfs_dqunlock(dqp);
    return 0;
}


/*
 * Given a udquot and gdquot, attach a ptr to the group dquot in the
 * udquot as a hint for future lookups.
 */
STATIC void
xfs_qm_dqattach_grouphint(
    xfs_dquot_t *udq,
    xfs_dquot_t *gdq)
{
    xfs_dquot_t *tmp;

    xfs_dqlock(udq);

    tmp = udq->q_gdquot;
    if (tmp) {
        if (tmp == gdq)
            goto done;

        udq->q_gdquot = NULL;
        xfs_qm_dqrele(tmp);
    }

    udq->q_gdquot = xfs_qm_dqhold(gdq);
done:
    xfs_dqunlock(udq);
}

static bool
xfs_qm_need_dqattach(
    struct xfs_inode    *ip)
{
    struct xfs_mount    *mp = ip->i_mount;

    if (!XFS_IS_QUOTA_RUNNING(mp))
        return false;
    if (!XFS_IS_QUOTA_ON(mp))
        return false;
    if (!XFS_NOT_DQATTACHED(mp, ip))
        return false;
    if (ip->i_ino == mp->m_sb.sb_uquotino ||
        ip->i_ino == mp->m_sb.sb_gquotino)
        return false;
    return true;
}

/*
 * 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_qm_need_dqattach(ip))
        return 0;

    ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

    if (XFS_IS_UQUOTA_ON(mp)) {
        error = xfs_qm_dqattach_one(ip, ip->i_d.di_uid, XFS_DQ_USER,
                        flags & XFS_QMOPT_DQALLOC,
                        NULL, &ip->i_udquot);
        if (error)
            goto done;
        nquotas++;
    }

    ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
    if (XFS_IS_OQUOTA_ON(mp)) {
        error = XFS_IS_GQUOTA_ON(mp) ?
            xfs_qm_dqattach_one(ip, ip->i_d.di_gid, XFS_DQ_GROUP,
                        flags & XFS_QMOPT_DQALLOC,
                        ip->i_udquot, &ip->i_gdquot) :
            xfs_qm_dqattach_one(ip, xfs_get_projid(ip), XFS_DQ_PROJ,
                        flags & XFS_QMOPT_DQALLOC,
                        ip->i_udquot, &ip->i_gdquot);
        /*
         * Don't worry about the udquot that we may have
         * attached above. It'll get detached, if not already.
         */
        if (error)
            goto done;
        nquotas++;
    }

    /*
     * Attach this group quota to the user quota as a hint.
     * This WON'T, in general, result in a thrash.
     */
    if (nquotas == 2) {
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(ip->i_udquot);
        ASSERT(ip->i_gdquot);

        /*
         * We do not have 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)
            xfs_qm_dqattach_grouphint(ip->i_udquot, ip->i_gdquot);
    }

 done:
#ifdef DEBUG
    if (!error) {
        if (XFS_IS_UQUOTA_ON(mp))
            ASSERT(ip->i_udquot);
        if (XFS_IS_OQUOTA_ON(mp))
            ASSERT(ip->i_gdquot);
    }
    ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
#endif
    return error;
}

int
xfs_qm_dqattach(
    struct xfs_inode    *ip,
    uint            flags)
{
    int         error;

    if (!xfs_qm_need_dqattach(ip))
        return 0;

    xfs_ilock(ip, XFS_ILOCK_EXCL);
    error = xfs_qm_dqattach_locked(ip, flags);
    xfs_iunlock(ip, XFS_ILOCK_EXCL);

    return error;
}

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

    trace_xfs_dquot_dqdetach(ip);

    ASSERT(ip->i_ino != ip->i_mount->m_sb.sb_uquotino);
    ASSERT(ip->i_ino != ip->i_mount->m_sb.sb_gquotino);
    if (ip->i_udquot) {
        xfs_qm_dqrele(ip->i_udquot);
        ip->i_udquot = NULL;
    }
    if (ip->i_gdquot) {
        xfs_qm_dqrele(ip->i_gdquot);
        ip->i_gdquot = NULL;
    }
}

/*
 * 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));

    qinf = mp->m_quotainfo = kmem_zalloc(sizeof(xfs_quotainfo_t), KM_SLEEP);

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

    INIT_RADIX_TREE(&qinf->qi_uquota_tree, GFP_NOFS);
    INIT_RADIX_TREE(&qinf->qi_gquota_tree, GFP_NOFS);
    mutex_init(&qinf->qi_tree_lock);

    INIT_LIST_HEAD(&qinf->qi_lru_list);
    qinf->qi_lru_count = 0;
    mutex_init(&qinf->qi_lru_lock);

    /* 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.
     *
     * Since we may not have done a quotacheck by this point, just read
     * the dquot without attaching it to any hashtables or lists.
     */
    error = xfs_qm_dqread(mp, 0,
            XFS_IS_UQUOTA_RUNNING(mp) ? XFS_DQ_USER :
             (XFS_IS_GQUOTA_RUNNING(mp) ? XFS_DQ_GROUP :
              XFS_DQ_PROJ),
            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);
 
        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;
    }

    qinf->qi_shrinker.shrink = xfs_qm_shake;
    qinf->qi_shrinker.seeks = DEFAULT_SEEKS;
    register_shrinker(&qinf->qi_shrinker);
    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);

    unregister_shrinker(&qi->qi_shrinker);

    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;
}

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

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

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

    /*
     * Make the changes in the superblock, and log those too.
     * sbfields arg may contain fields other than *QUOTINO;
     * VERSIONNUM for example.
     */
    spin_lock(&mp->m_sb_lock);
    if (flags & XFS_QMOPT_SBVERSION) {
        ASSERT(!xfs_sb_version_hasquota(&mp->m_sb));
        ASSERT((sbfields & (XFS_SB_VERSIONNUM | XFS_SB_UQUOTINO |
                   XFS_SB_GQUOTINO | XFS_SB_QFLAGS)) ==
               (XFS_SB_VERSIONNUM | XFS_SB_UQUOTINO |
            XFS_SB_GQUOTINO | XFS_SB_QFLAGS));

        xfs_sb_version_addquota(&mp->m_sb);
        mp->m_sb.sb_uquotino = NULLFSINO;
        mp->m_sb.sb_gquotino = NULLFSINO;

        /* qflags will get updated _after_ quotacheck */
        mp->m_sb.sb_qflags = 0;
    }
    if (flags & XFS_QMOPT_UQUOTA)
        mp->m_sb.sb_uquotino = (*ip)->i_ino;
    else
        mp->m_sb.sb_gquotino = (*ip)->i_ino;
    spin_unlock(&mp->m_sb_lock);
    xfs_mod_sb(tp, sbfields);

    if ((error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES))) {
        xfs_alert(mp, "%s failed (error %d)!", __func__, error);
        return error;
    }
    return 0;
}


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

    trace_xfs_reset_dqcounts(bp, _RET_IP_);

    /*
     * Reset all counters and timers. They'll be
     * started afresh by xfs_qm_quotacheck.
     */
#ifdef DEBUG
    j = XFS_FSB_TO_B(mp, XFS_DQUOT_CLUSTER_SIZE_FSB);
    do_div(j, sizeof(xfs_dqblk_t));
    ASSERT(mp->m_quotainfo->qi_dqperchunk == j);
#endif
    ddq = bp->b_addr;
    for (j = 0; j < mp->m_quotainfo->qi_dqperchunk; j++) {
        /*
         * Do a sanity check, and if needed, repair the dqblk. Don't
         * output any warnings because it's perfectly possible to
         * find uninitialised dquot blks. See comment in xfs_qm_dqcheck.
         */
        (void) xfs_qm_dqcheck(mp, ddq, id+j, type, XFS_QMOPT_DQREPAIR,
                      "xfs_quotacheck");
        ddq->d_bcount = 0;
        ddq->d_icount = 0;
        ddq->d_rtbcount = 0;
        ddq->d_btimer = 0;
        ddq->d_itimer = 0;
        ddq->d_rtbtimer = 0;
        ddq->d_bwarns = 0;
        ddq->d_iwarns = 0;
        ddq->d_rtbwarns = 0;
        ddq = (xfs_disk_dquot_t *) ((xfs_dqblk_t *)ddq + 1);
    }
}

STATIC int
xfs_qm_dqiter_bufs(
    struct xfs_mount    *mp,
    xfs_dqid_t      firstid,
    xfs_fsblock_t       bno,
    xfs_filblks_t       blkcnt,
    uint            flags,
    struct list_head    *buffer_list)
{
    struct xfs_buf      *bp;
    int         error;
    int         type;

    ASSERT(blkcnt > 0);
    type = flags & XFS_QMOPT_UQUOTA ? XFS_DQ_USER :
        (flags & XFS_QMOPT_PQUOTA ? XFS_DQ_PROJ : XFS_DQ_GROUP);
    error = 0;

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

        xfs_qm_reset_dqcounts(mp, bp, firstid, type);
        xfs_buf_delwri_queue(bp, buffer_list);
        xfs_buf_relse(bp);
        /*
         * goto the next block.
         */
        bno++;
        firstid += mp->m_quotainfo->qi_dqperchunk;
    }

    return error;
}

/*
 * Iterate over all allocated USR/GRP/PRJ dquots in the system, calling a
 * caller supplied function for every chunk of dquots that we find.
 */
STATIC int
xfs_qm_dqiterate(
    struct xfs_mount    *mp,
    struct xfs_inode    *qip,
    uint            flags,
    struct list_head    *buffer_list)
{
    struct xfs_bmbt_irec    *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, mp->m_super->s_maxbytes);
    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_read(qip, lblkno, maxlblkcnt - lblkno,
                       map, &nmaps, 0);
        xfs_iunlock(qip, XFS_ILOCK_SHARED);
        if (error)
            break;

        ASSERT(nmaps <= XFS_DQITER_MAP_SIZE);
        for (i = 0; i < nmaps; i++) {
            ASSERT(map[i].br_startblock != DELAYSTARTBLOCK);
            ASSERT(map[i].br_blockcount);


            lblkno += map[i].br_blockcount;

            if (map[i].br_startblock == HOLESTARTBLOCK)
                continue;

            firstid = (xfs_dqid_t) map[i].br_startoff *
                mp->m_quotainfo->qi_dqperchunk;
            /*
             * Do a read-ahead on the next extent.
             */
            if ((i+1 < nmaps) &&
                (map[i+1].br_startblock != HOLESTARTBLOCK)) {
                rablkcnt =  map[i+1].br_blockcount;
                rablkno = map[i+1].br_startblock;
                while (rablkcnt--) {
                    xfs_buf_readahead(mp->m_ddev_targp,
                           XFS_FSB_TO_DADDR(mp, rablkno),
                           mp->m_quotainfo->qi_dqchunklen);
                    rablkno++;
                }
            }
            /*
             * Iterate thru all the blks in the extent and
             * reset the counters of all the dquots inside them.
             */
            error = xfs_qm_dqiter_bufs(mp, firstid,
                           map[i].br_startblock,
                           map[i].br_blockcount,
                           flags, buffer_list);
            if (error)
                goto out;
        }
    } while (nmaps > 0);

out:
    kmem_free(map);
    return error;
}

/*
 * Called by dqusage_adjust in doing a quotacheck.
 *
 * Given the inode, and a dquot id this updates both the incore dqout as well
 * as the buffer copy. This is so that once the quotacheck is done, we can
 * just log all the buffers, as opposed to logging numerous updates to
 * individual dquots.
 */
STATIC int
xfs_qm_quotacheck_dqadjust(
    struct xfs_inode    *ip,
    xfs_dqid_t      id,
    uint            type,
    xfs_qcnt_t      nblks,
    xfs_qcnt_t      rtblks)
{
    struct xfs_mount    *mp = ip->i_mount;
    struct xfs_dquot    *dqp;
    int         error;

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

    trace_xfs_dqadjust(dqp);

    /*
     * Adjust the inode count and the block count to reflect this inode's
     * resource usage.
     */
    be64_add_cpu(&dqp->q_core.d_icount, 1);
    dqp->q_res_icount++;
    if (nblks) {
        be64_add_cpu(&dqp->q_core.d_bcount, nblks);
        dqp->q_res_bcount += nblks;
    }
    if (rtblks) {
        be64_add_cpu(&dqp->q_core.d_rtbcount, rtblks);
        dqp->q_res_rtbcount += rtblks;
    }

    /*
     * Set default limits, adjust timers (since we changed usages)
     *
     * There are no timers for the default values set in the root dquot.
     */
    if (dqp->q_core.d_id) {
        xfs_qm_adjust_dqlimits(mp, &dqp->q_core);
        xfs_qm_adjust_dqtimers(mp, &dqp->q_core);
    }

    dqp->dq_flags |= XFS_DQ_DIRTY;
    xfs_qm_dqput(dqp);
    return 0;
}

STATIC int
xfs_qm_get_rtblks(
    xfs_inode_t *ip,
    xfs_qcnt_t  *O_rtblks)
{
    xfs_filblks_t   rtblks;         /* total rt blks */
    xfs_extnum_t    idx;            /* extent record index */
    xfs_ifork_t *ifp;           /* inode fork pointer */
    xfs_extnum_t    nextents;       /* number of extent entries */
    int     error;

    ASSERT(XFS_IS_REALTIME_INODE(ip));
    ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
    if (!(ifp->if_flags & XFS_IFEXTENTS)) {
        if ((error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK)))
            return error;
    }
    rtblks = 0;
    nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
    for (idx = 0; idx < nextents; idx++)
        rtblks += xfs_bmbt_get_blockcount(xfs_iext_get_ext(ifp, idx));
    *O_rtblks = (xfs_qcnt_t)rtblks;
    return 0;
}

/*
 * callback routine supplied to bulkstat(). Given an inumber, find its
 * dquots and update them to account for resources taken by that inode.
 */
/* ARGSUSED */
STATIC int
xfs_qm_dqusage_adjust(
    xfs_mount_t *mp,        /* mount point for filesystem */
    xfs_ino_t   ino,        /* inode number to get data for */
    void        __user *buffer, /* not used */
    int     ubsize,     /* not used */
    int     *ubused,    /* not used */
    int     *res)       /* result code value */
{
    xfs_inode_t *ip;
    xfs_qcnt_t  nblks, rtblks = 0;
    int     error;

    ASSERT(XFS_IS_QUOTA_RUNNING(mp));

    /*
     * rootino must have its resources accounted for, not so with the quota
     * inodes.
     */
    if (ino == mp->m_sb.sb_uquotino || ino == mp->m_sb.sb_gquotino) {
        *res = BULKSTAT_RV_NOTHING;
        return XFS_ERROR(EINVAL);
    }

    /*
     * We don't _need_ to take the ilock EXCL. However, the xfs_qm_dqget
     * interface expects the inode to be exclusively locked because that's
     * the case in all other instances. It's OK that we do this because
     * quotacheck is done only at mount time.
     */
    error = xfs_iget(mp, NULL, ino, 0, XFS_ILOCK_EXCL, &ip);
    if (error) {
        *res = BULKSTAT_RV_NOTHING;
        return error;
    }

    ASSERT(ip->i_delayed_blks == 0);

    if (XFS_IS_REALTIME_INODE(ip)) {
        /*
         * Walk thru the extent list and count the realtime blocks.
         */
        error = xfs_qm_get_rtblks(ip, &rtblks);
        if (error)
            goto error0;
    }

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

    /*
     * Add the (disk blocks and inode) resources occupied by this
     * inode to its dquots. We do this adjustment in the incore dquot,
     * and also copy the changes to its buffer.
     * We don't care about putting these changes in a transaction
     * envelope because if we crash in the middle of a 'quotacheck'
     * we have to start from the beginning anyway.
     * Once we're done, we'll log all the dquot bufs.
     *
     * The *QUOTA_ON checks below may look pretty racy, but quotachecks
     * and quotaoffs don't race. (Quotachecks happen at mount time only).
     */
    if (XFS_IS_UQUOTA_ON(mp)) {
        error = xfs_qm_quotacheck_dqadjust(ip, ip->i_d.di_uid,
                           XFS_DQ_USER, nblks, rtblks);
        if (error)
            goto error0;
    }

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

    if (XFS_IS_PQUOTA_ON(mp)) {
        error = xfs_qm_quotacheck_dqadjust(ip, xfs_get_projid(ip),
                           XFS_DQ_PROJ, nblks, rtblks);
        if (error)
            goto error0;
    }

    xfs_iunlock(ip, XFS_ILOCK_EXCL);
    IRELE(ip);
    *res = BULKSTAT_RV_DIDONE;
    return 0;

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

STATIC int
xfs_qm_flush_one(
    struct xfs_dquot    *dqp,
    void            *data)
{
    struct list_head    *buffer_list = data;
    struct xfs_buf      *bp = NULL;
    int         error = 0;

    xfs_dqlock(dqp);
    if (dqp->dq_flags & XFS_DQ_FREEING)
        goto out_unlock;
    if (!XFS_DQ_IS_DIRTY(dqp))
        goto out_unlock;

    xfs_dqflock(dqp);
    error = xfs_qm_dqflush(dqp, &bp);
    if (error)
        goto out_unlock;

    xfs_buf_delwri_queue(bp, buffer_list);
    xfs_buf_relse(bp);
out_unlock:
    xfs_dqunlock(dqp);
    return error;
}

/*
 * Walk thru all the filesystem inodes and construct a consistent view
 * of the disk quota world. If the quotacheck fails, disable quotas.
 */
int
xfs_qm_quotacheck(
    xfs_mount_t *mp)
{
    int     done, count, error, error2;
    xfs_ino_t   lastino;
    size_t      structsz;
    xfs_inode_t *uip, *gip;
    uint        flags;
    LIST_HEAD   (buffer_list);

    count = INT_MAX;
    structsz = 1;
    lastino = 0;
    flags = 0;

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

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

    /*
     * First we go thru all the dquots on disk, USR and GRP/PRJ, and reset
     * their counters to zero. We need a clean slate.
     * We don't log our changes till later.
     */
    uip = mp->m_quotainfo->qi_uquotaip;
    if (uip) {
        error = xfs_qm_dqiterate(mp, uip, XFS_QMOPT_UQUOTA,
                     &buffer_list);
        if (error)
            goto error_return;
        flags |= XFS_UQUOTA_CHKD;
    }

    gip = mp->m_quotainfo->qi_gquotaip;
    if (gip) {
        error = xfs_qm_dqiterate(mp, gip, XFS_IS_GQUOTA_ON(mp) ?
                     XFS_QMOPT_GQUOTA : XFS_QMOPT_PQUOTA,
                     &buffer_list);
        if (error)
            goto error_return;
        flags |= XFS_OQUOTA_CHKD;
    }

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

    } while (!done);

    /*
     * We've made all the changes that we need to make incore.  Flush them
     * down to disk buffers if everything was updated successfully.
     */
    if (XFS_IS_UQUOTA_ON(mp)) {
        error = xfs_qm_dquot_walk(mp, XFS_DQ_USER, xfs_qm_flush_one,
                      &buffer_list);
    }
    if (XFS_IS_GQUOTA_ON(mp)) {
        error2 = xfs_qm_dquot_walk(mp, XFS_DQ_GROUP, xfs_qm_flush_one,
                       &buffer_list);
        if (!error)
            error = error2;
    }
    if (XFS_IS_PQUOTA_ON(mp)) {
        error2 = xfs_qm_dquot_walk(mp, XFS_DQ_PROJ, xfs_qm_flush_one,
                       &buffer_list);
        if (!error)
            error = error2;
    }

    error2 = xfs_buf_delwri_submit(&buffer_list);
    if (!error)
        error = error2;

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

    /*
     * 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_ALL_QUOTA_CHKD;
    mp->m_qflags |= flags;

 error_return:
    while (!list_empty(&buffer_list)) {
        struct xfs_buf *bp =
            list_first_entry(&buffer_list, struct xfs_buf, b_list);
        list_del_init(&bp->b_list);
        xfs_buf_relse(bp);
    }

    if (error) {
        xfs_warn(mp,
    "Quotacheck: Unsuccessful (Error %d): Disabling quotas.",
            error);
        /*
         * We must turn off quotas.
         */
        ASSERT(mp->m_quotainfo != NULL);
        xfs_qm_destroy_quotainfo(mp);
        if (xfs_mount_reset_sbqflags(mp)) {
            xfs_warn(mp,
                "Quotacheck: Failed to reset quota flags.");
        }
    } else
        xfs_notice(mp, "Quotacheck: Done.");
    return (error);
}

/*
 * This is called after the superblock has been read in and we're ready to
 * iget the quota inodes.
 */
STATIC int
xfs_qm_init_quotainos(
    xfs_mount_t *mp)
{
    xfs_inode_t *uip, *gip;
    int     error;
    __int64_t   sbflags;
    uint        flags;

    ASSERT(mp->m_quotainfo);
    uip = gip = NULL;
    sbflags = 0;
    flags = 0;

    /*
     * Get the uquota and gquota inodes
     */
    if (xfs_sb_version_hasquota(&mp->m_sb)) {
        if (XFS_IS_UQUOTA_ON(mp) &&
            mp->m_sb.sb_uquotino != NULLFSINO) {
            ASSERT(mp->m_sb.sb_uquotino > 0);
            if ((error = xfs_iget(mp, NULL, mp->m_sb.sb_uquotino,
                         0, 0, &uip)))
                return XFS_ERROR(error);
        }
        if (XFS_IS_OQUOTA_ON(mp) &&
            mp->m_sb.sb_gquotino != NULLFSINO) {
            ASSERT(mp->m_sb.sb_gquotino > 0);
            if ((error = xfs_iget(mp, NULL, mp->m_sb.sb_gquotino,
                         0, 0, &gip))) {
                if (uip)
                    IRELE(uip);
                return XFS_ERROR(error);
            }
        }
    } else {
        flags |= XFS_QMOPT_SBVERSION;
        sbflags |= (XFS_SB_VERSIONNUM | XFS_SB_UQUOTINO |
                XFS_SB_GQUOTINO | XFS_SB_QFLAGS);
    }

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

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

            return XFS_ERROR(error);
        }
    }

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

    return 0;
}

STATIC void
xfs_qm_dqfree_one(
    struct xfs_dquot    *dqp)
{
    struct xfs_mount    *mp = dqp->q_mount;
    struct xfs_quotainfo    *qi = mp->m_quotainfo;

    mutex_lock(&qi->qi_tree_lock);
    radix_tree_delete(XFS_DQUOT_TREE(qi, dqp->q_core.d_flags),
              be32_to_cpu(dqp->q_core.d_id));

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

    xfs_qm_dqdestroy(dqp);
}

STATIC void
xfs_qm_dqreclaim_one(
    struct xfs_dquot    *dqp,
    struct list_head    *buffer_list,
    struct list_head    *dispose_list)
{
    struct xfs_mount    *mp = dqp->q_mount;
    struct xfs_quotainfo    *qi = mp->m_quotainfo;
    int         error;

    if (!xfs_dqlock_nowait(dqp))
        goto out_busy;

    /*
     * This dquot has acquired a reference in the meantime remove it from
     * the freelist and try again.
     */
    if (dqp->q_nrefs) {
        xfs_dqunlock(dqp);

        trace_xfs_dqreclaim_want(dqp);
        XFS_STATS_INC(xs_qm_dqwants);

        list_del_init(&dqp->q_lru);
        qi->qi_lru_count--;
        XFS_STATS_DEC(xs_qm_dquot_unused);
        return;
    }

    /*
     * Try to grab the flush lock. If this dquot is in the process of
     * getting flushed to disk, we don't want to reclaim it.
     */
    if (!xfs_dqflock_nowait(dqp))
        goto out_busy;

    if (XFS_DQ_IS_DIRTY(dqp)) {
        struct xfs_buf  *bp = NULL;

        trace_xfs_dqreclaim_dirty(dqp);

        error = xfs_qm_dqflush(dqp, &bp);
        if (error) {
            xfs_warn(mp, "%s: dquot %p flush failed",
                 __func__, dqp);
            goto out_busy;
        }

        xfs_buf_delwri_queue(bp, buffer_list);
        xfs_buf_relse(bp);
        /*
         * Give the dquot another try on the freelist, as the
         * flushing will take some time.
         */
        goto out_busy;
    }
    xfs_dqfunlock(dqp);

    /*
     * Prevent lookups now that we are past the point of no return.
     */
    dqp->dq_flags |= XFS_DQ_FREEING;
    xfs_dqunlock(dqp);

    ASSERT(dqp->q_nrefs == 0);
    list_move_tail(&dqp->q_lru, dispose_list);
    qi->qi_lru_count--;
    XFS_STATS_DEC(xs_qm_dquot_unused);

    trace_xfs_dqreclaim_done(dqp);
    XFS_STATS_INC(xs_qm_dqreclaims);
    return;

out_busy:
    xfs_dqunlock(dqp);

    /*
     * Move the dquot to the tail of the list so that we don't spin on it.
     */
    list_move_tail(&dqp->q_lru, &qi->qi_lru_list);

    trace_xfs_dqreclaim_busy(dqp);
    XFS_STATS_INC(xs_qm_dqreclaim_misses);
}

STATIC int
xfs_qm_shake(
    struct shrinker     *shrink,
    struct shrink_control   *sc)
{
    struct xfs_quotainfo    *qi =
        container_of(shrink, struct xfs_quotainfo, qi_shrinker);
    int         nr_to_scan = sc->nr_to_scan;
    LIST_HEAD       (buffer_list);
    LIST_HEAD       (dispose_list);
    struct xfs_dquot    *dqp;
    int         error;

    if ((sc->gfp_mask & (__GFP_FS|__GFP_WAIT)) != (__GFP_FS|__GFP_WAIT))
        return 0;
    if (!nr_to_scan)
        goto out;

    mutex_lock(&qi->qi_lru_lock);
    while (!list_empty(&qi->qi_lru_list)) {
        if (nr_to_scan-- <= 0)
            break;
        dqp = list_first_entry(&qi->qi_lru_list, struct xfs_dquot,
                       q_lru);
        xfs_qm_dqreclaim_one(dqp, &buffer_list, &dispose_list);
    }
    mutex_unlock(&qi->qi_lru_lock);

    error = xfs_buf_delwri_submit(&buffer_list);
    if (error)
        xfs_warn(NULL, "%s: dquot reclaim failed", __func__);

    while (!list_empty(&dispose_list)) {
        dqp = list_first_entry(&dispose_list, struct xfs_dquot, q_lru);
        list_del_init(&dqp->q_lru);
        xfs_qm_dqfree_one(dqp);
    }

out:
    return (qi->qi_lru_count / 100) * sysctl_vfs_cache_pressure;
}

/*
 * 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;

    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, gid and prid 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 = xfs_qm_dqhold(ip->i_udquot);
        }
    }
    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 = xfs_qm_dqhold(ip->i_gdquot);
        }
    } else if ((flags & XFS_QMOPT_PQUOTA) && XFS_IS_PQUOTA_ON(mp)) {
        if (xfs_get_projid(ip) != 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 = xfs_qm_dqhold(ip->i_gdquot);
        }
    }
    if (uq)
        trace_xfs_dquot_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.
     */
    *IO_olddq = xfs_qm_dqhold(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) &&
             xfs_get_projid(ip) != 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) {
        ASSERT(ip->i_udquot == NULL);
        ASSERT(XFS_IS_UQUOTA_ON(mp));
        ASSERT(ip->i_d.di_uid == be32_to_cpu(udqp->q_core.d_id));

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

        ip->i_gdquot = xfs_qm_dqhold(gdqp);
        xfs_trans_mod_dquot(tp, gdqp, XFS_TRANS_DQ_ICOUNT, 1);
    }
}