Linux 6.14-rc2

[linux.git] / fs / xfs / xfs_dquot.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2003 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_shared.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_quota.h"
#include "xfs_trans.h"
#include "xfs_buf_item.h"
#include "xfs_trans_space.h"
#include "xfs_trans_priv.h"
#include "xfs_qm.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_bmap_btree.h"
#include "xfs_error.h"
#include "xfs_health.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.
 */

struct kmem_cache               *xfs_dqtrx_cache;
static struct kmem_cache        *xfs_dquot_cache;

static struct lock_class_key xfs_dquot_group_class;
static struct lock_class_key xfs_dquot_project_class;

/* Record observations of quota corruption with the health tracking system. */
static void
xfs_dquot_mark_sick(
        struct xfs_dquot        *dqp)
{
        struct xfs_mount        *mp = dqp->q_mount;

        switch (dqp->q_type) {
        case XFS_DQTYPE_USER:
                xfs_fs_mark_sick(mp, XFS_SICK_FS_UQUOTA);
                break;
        case XFS_DQTYPE_GROUP:
                xfs_fs_mark_sick(mp, XFS_SICK_FS_GQUOTA);
                break;
        case XFS_DQTYPE_PROJ:
                xfs_fs_mark_sick(mp, XFS_SICK_FS_PQUOTA);
                break;
        default:
                ASSERT(0);
                break;
        }
}

/*
 * Detach the dquot buffer if it's still attached, because we can get called
 * through dqpurge after a log shutdown.  Caller must hold the dqflock or have
 * otherwise isolated the dquot.
 */
void
xfs_dquot_detach_buf(
        struct xfs_dquot        *dqp)
{
        struct xfs_dq_logitem   *qlip = &dqp->q_logitem;
        struct xfs_buf          *bp = NULL;

        spin_lock(&qlip->qli_lock);
        if (qlip->qli_item.li_buf) {
                bp = qlip->qli_item.li_buf;
                qlip->qli_item.li_buf = NULL;
        }
        spin_unlock(&qlip->qli_lock);
        if (bp) {
                xfs_buf_lock(bp);
                list_del_init(&qlip->qli_item.li_bio_list);
                xfs_buf_relse(bp);
        }
}

/*
 * This is called to free all the memory associated with a dquot
 */
void
xfs_qm_dqdestroy(
        struct xfs_dquot        *dqp)
{
        ASSERT(list_empty(&dqp->q_lru));
        ASSERT(dqp->q_logitem.qli_item.li_buf == NULL);

        kvfree(dqp->q_logitem.qli_item.li_lv_shadow);
        mutex_destroy(&dqp->q_qlock);

        XFS_STATS_DEC(dqp->q_mount, xs_qm_dquot);
        kmem_cache_free(xfs_dquot_cache, dqp);
}

/*
 * 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(
        struct xfs_dquot        *dq)
{
        struct xfs_mount        *mp = dq->q_mount;
        struct xfs_quotainfo    *q = mp->m_quotainfo;
        struct xfs_def_quota    *defq;
        int                     prealloc = 0;

        ASSERT(dq->q_id);
        defq = xfs_get_defquota(q, xfs_dquot_type(dq));

        if (!dq->q_blk.softlimit) {
                dq->q_blk.softlimit = defq->blk.soft;
                prealloc = 1;
        }
        if (!dq->q_blk.hardlimit) {
                dq->q_blk.hardlimit = defq->blk.hard;
                prealloc = 1;
        }
        if (!dq->q_ino.softlimit)
                dq->q_ino.softlimit = defq->ino.soft;
        if (!dq->q_ino.hardlimit)
                dq->q_ino.hardlimit = defq->ino.hard;
        if (!dq->q_rtb.softlimit)
                dq->q_rtb.softlimit = defq->rtb.soft;
        if (!dq->q_rtb.hardlimit)
                dq->q_rtb.hardlimit = defq->rtb.hard;

        if (prealloc)
                xfs_dquot_set_prealloc_limits(dq);
}

/* Set the expiration time of a quota's grace period. */
time64_t
xfs_dquot_set_timeout(
        struct xfs_mount        *mp,
        time64_t                timeout)
{
        struct xfs_quotainfo    *qi = mp->m_quotainfo;

        return clamp_t(time64_t, timeout, qi->qi_expiry_min,
                                          qi->qi_expiry_max);
}

/* Set the length of the default grace period. */
time64_t
xfs_dquot_set_grace_period(
        time64_t                grace)
{
        return clamp_t(time64_t, grace, XFS_DQ_GRACE_MIN, XFS_DQ_GRACE_MAX);
}

/*
 * Determine if this quota counter is over either limit and set the quota
 * timers as appropriate.
 */
static inline void
xfs_qm_adjust_res_timer(
        struct xfs_mount        *mp,
        struct xfs_dquot_res    *res,
        struct xfs_quota_limits *qlim)
{
        ASSERT(res->hardlimit == 0 || res->softlimit <= res->hardlimit);

        if ((res->softlimit && res->count > res->softlimit) ||
            (res->hardlimit && res->count > res->hardlimit)) {
                if (res->timer == 0)
                        res->timer = xfs_dquot_set_timeout(mp,
                                        ktime_get_real_seconds() + qlim->time);
        } else {
                res->timer = 0;
        }
}

/*
 * 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(
        struct xfs_dquot        *dq)
{
        struct xfs_mount        *mp = dq->q_mount;
        struct xfs_quotainfo    *qi = mp->m_quotainfo;
        struct xfs_def_quota    *defq;

        ASSERT(dq->q_id);
        defq = xfs_get_defquota(qi, xfs_dquot_type(dq));

        xfs_qm_adjust_res_timer(dq->q_mount, &dq->q_blk, &defq->blk);
        xfs_qm_adjust_res_timer(dq->q_mount, &dq->q_ino, &defq->ino);
        xfs_qm_adjust_res_timer(dq->q_mount, &dq->q_rtb, &defq->rtb);
}

/*
 * initialize a buffer full of dquots and log the whole thing
 */
void
xfs_qm_init_dquot_blk(
        struct xfs_trans        *tp,
        xfs_dqid_t              id,
        xfs_dqtype_t            type,
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_quotainfo    *q = mp->m_quotainfo;
        struct xfs_dqblk        *d;
        xfs_dqid_t              curid;
        unsigned int            qflag;
        unsigned int            blftype;
        int                     i;

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

        switch (type) {
        case XFS_DQTYPE_USER:
                qflag = XFS_UQUOTA_CHKD;
                blftype = XFS_BLF_UDQUOT_BUF;
                break;
        case XFS_DQTYPE_PROJ:
                qflag = XFS_PQUOTA_CHKD;
                blftype = XFS_BLF_PDQUOT_BUF;
                break;
        case XFS_DQTYPE_GROUP:
                qflag = XFS_GQUOTA_CHKD;
                blftype = XFS_BLF_GDQUOT_BUF;
                break;
        default:
                ASSERT(0);
                return;
        }

        d = bp->b_addr;

        /*
         * ID of the first dquot in the block - id's are zero based.
         */
        curid = id - (id % q->qi_dqperchunk);
        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_type = type;
                if (curid > 0 && xfs_has_bigtime(mp))
                        d->dd_diskdq.d_type |= XFS_DQTYPE_BIGTIME;
                if (xfs_has_crc(mp)) {
                        uuid_copy(&d->dd_uuid, &mp->m_sb.sb_meta_uuid);
                        xfs_update_cksum((char *)d, sizeof(struct xfs_dqblk),
                                         XFS_DQUOT_CRC_OFF);
                }
        }

        xfs_trans_dquot_buf(tp, bp, blftype);

        /*
         * quotacheck uses delayed writes to update all the dquots on disk in an
         * efficient manner instead of logging the individual dquot changes as
         * they are made. However if we log the buffer allocated here and crash
         * after quotacheck while the logged initialisation is still in the
         * active region of the log, log recovery can replay the dquot buffer
         * initialisation over the top of the checked dquots and corrupt quota
         * accounting.
         *
         * To avoid this problem, quotacheck cannot log the initialised buffer.
         * We must still dirty the buffer and write it back before the
         * allocation transaction clears the log. Therefore, mark the buffer as
         * ordered instead of logging it directly. This is safe for quotacheck
         * because it detects and repairs allocated but initialized dquot blocks
         * in the quota inodes.
         */
        if (!(mp->m_qflags & qflag))
                xfs_trans_ordered_buf(tp, bp);
        else
                xfs_trans_log_buf(tp, bp, 0, BBTOB(q->qi_dqchunklen) - 1);
}

static void
xfs_dquot_set_prealloc(
        struct xfs_dquot_pre            *pre,
        const struct xfs_dquot_res      *res)
{
        xfs_qcnt_t                      space;

        pre->q_prealloc_hi_wmark = res->hardlimit;
        pre->q_prealloc_lo_wmark = res->softlimit;

        space = div_u64(pre->q_prealloc_hi_wmark, 100);
        if (!pre->q_prealloc_lo_wmark)
                pre->q_prealloc_lo_wmark = space * 95;

        pre->q_low_space[XFS_QLOWSP_1_PCNT] = space;
        pre->q_low_space[XFS_QLOWSP_3_PCNT] = space * 3;
        pre->q_low_space[XFS_QLOWSP_5_PCNT] = space * 5;
}

/*
 * Initialize the dynamic speculative preallocation thresholds. The lo/hi
 * watermarks correspond to the soft and hard limits by default. If a soft limit
 * is not specified, we use 95% of the hard limit.
 */
void
xfs_dquot_set_prealloc_limits(struct xfs_dquot *dqp)
{
        xfs_dquot_set_prealloc(&dqp->q_blk_prealloc, &dqp->q_blk);
        xfs_dquot_set_prealloc(&dqp->q_rtb_prealloc, &dqp->q_rtb);
}

/*
 * Ensure that the given in-core dquot has a buffer on disk backing it, and
 * return the buffer locked and held. This is called when the bmapi finds a
 * hole.
 */
STATIC int
xfs_dquot_disk_alloc(
        struct xfs_dquot        *dqp,
        struct xfs_buf          **bpp)
{
        struct xfs_bmbt_irec    map;
        struct xfs_trans        *tp;
        struct xfs_mount        *mp = dqp->q_mount;
        struct xfs_buf          *bp;
        xfs_dqtype_t            qtype = xfs_dquot_type(dqp);
        struct xfs_inode        *quotip = xfs_quota_inode(mp, qtype);
        int                     nmaps = 1;
        int                     error;

        trace_xfs_dqalloc(dqp);

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_qm_dqalloc,
                        XFS_QM_DQALLOC_SPACE_RES(mp), 0, 0, &tp);
        if (error)
                return error;

        xfs_ilock(quotip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, quotip, 0);

        if (!xfs_this_quota_on(dqp->q_mount, qtype)) {
                /*
                 * Return if this type of quotas is turned off while we didn't
                 * have an inode lock
                 */
                error = -ESRCH;
                goto err_cancel;
        }

        error = xfs_iext_count_extend(tp, quotip, XFS_DATA_FORK,
                        XFS_IEXT_ADD_NOSPLIT_CNT);
        if (error)
                goto err_cancel;

        /* Create the block mapping. */
        error = xfs_bmapi_write(tp, quotip, dqp->q_fileoffset,
                        XFS_DQUOT_CLUSTER_SIZE_FSB, XFS_BMAPI_METADATA, 0, &map,
                        &nmaps);
        if (error)
                goto err_cancel;

        ASSERT(map.br_blockcount == XFS_DQUOT_CLUSTER_SIZE_FSB);
        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) */
        error = xfs_trans_get_buf(tp, mp->m_ddev_targp, dqp->q_blkno,
                        mp->m_quotainfo->qi_dqchunklen, 0, &bp);
        if (error)
                goto err_cancel;
        bp->b_ops = &xfs_dquot_buf_ops;

        /*
         * Make a chunk of dquots out of this buffer and log
         * the entire thing.
         */
        xfs_qm_init_dquot_blk(tp, dqp->q_id, qtype, bp);
        xfs_buf_set_ref(bp, XFS_DQUOT_REF);

        /*
         * Hold the buffer and join it to the dfops so that we'll still own
         * the buffer when we return to the caller.  The buffer disposal on
         * error must be paid attention to very carefully, as it has been
         * broken since commit efa092f3d4c6 "[XFS] Fixes a bug in the quota
         * code when allocating a new dquot record" in 2005, and the later
         * conversion to xfs_defer_ops in commit 310a75a3c6c747 failed to keep
         * the buffer locked across the _defer_finish call.  We can now do
         * this correctly with xfs_defer_bjoin.
         *
         * Above, we allocated a disk block for the dquot information and used
         * get_buf to initialize the dquot. If the _defer_finish fails, the old
         * transaction is gone but the new buffer is not joined or held to any
         * transaction, so we must _buf_relse it.
         *
         * If everything succeeds, the caller of this function is returned a
         * buffer that is locked and held to the transaction.  The caller
         * is responsible for unlocking any buffer passed back, either
         * manually or by committing the transaction.  On error, the buffer is
         * released and not passed back.
         *
         * Keep the quota inode ILOCKed until after the transaction commit to
         * maintain the atomicity of bmap/rmap updates.
         */
        xfs_trans_bhold(tp, bp);
        error = xfs_trans_commit(tp);
        xfs_iunlock(quotip, XFS_ILOCK_EXCL);
        if (error) {
                xfs_buf_relse(bp);
                return error;
        }

        *bpp = bp;
        return 0;

err_cancel:
        xfs_trans_cancel(tp);
        xfs_iunlock(quotip, XFS_ILOCK_EXCL);
        return error;
}

/*
 * Read in the in-core dquot's on-disk metadata and return the buffer.
 * Returns ENOENT to signal a hole.
 */
STATIC int
xfs_dquot_disk_read(
        struct xfs_mount        *mp,
        struct xfs_dquot        *dqp,
        struct xfs_buf          **bpp)
{
        struct xfs_bmbt_irec    map;
        struct xfs_buf          *bp;
        xfs_dqtype_t            qtype = xfs_dquot_type(dqp);
        struct xfs_inode        *quotip = xfs_quota_inode(mp, qtype);
        uint                    lock_mode;
        int                     nmaps = 1;
        int                     error;

        lock_mode = xfs_ilock_data_map_shared(quotip);
        if (!xfs_this_quota_on(mp, qtype)) {
                /*
                 * Return if this type of quotas is turned off while we
                 * didn't have the quota inode lock.
                 */
                xfs_iunlock(quotip, lock_mode);
                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, lock_mode);
        if (error)
                return error;

        ASSERT(nmaps == 1);
        ASSERT(map.br_blockcount >= 1);
        ASSERT(map.br_startblock != DELAYSTARTBLOCK);
        if (map.br_startblock == HOLESTARTBLOCK)
                return -ENOENT;

        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, NULL, mp->m_ddev_targp, dqp->q_blkno,
                        mp->m_quotainfo->qi_dqchunklen, 0, &bp,
                        &xfs_dquot_buf_ops);
        if (xfs_metadata_is_sick(error))
                xfs_dquot_mark_sick(dqp);
        if (error) {
                ASSERT(bp == NULL);
                return error;
        }

        ASSERT(xfs_buf_islocked(bp));
        xfs_buf_set_ref(bp, XFS_DQUOT_REF);
        *bpp = bp;

        return 0;
}

/* Allocate and initialize everything we need for an incore dquot. */
STATIC struct xfs_dquot *
xfs_dquot_alloc(
        struct xfs_mount        *mp,
        xfs_dqid_t              id,
        xfs_dqtype_t            type)
{
        struct xfs_dquot        *dqp;

        dqp = kmem_cache_zalloc(xfs_dquot_cache, GFP_KERNEL | __GFP_NOFAIL);

        dqp->q_type = type;
        dqp->q_id = id;
        dqp->q_mount = mp;
        INIT_LIST_HEAD(&dqp->q_lru);
        mutex_init(&dqp->q_qlock);
        init_waitqueue_head(&dqp->q_pinwait);
        dqp->q_fileoffset = (xfs_fileoff_t)id / mp->m_quotainfo->qi_dqperchunk;
        /*
         * Offset of dquot in the (fixed sized) dquot chunk.
         */
        dqp->q_bufoffset = (id % mp->m_quotainfo->qi_dqperchunk) *
                        sizeof(struct xfs_dqblk);

        /*
         * 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.
         */
        switch (type) {
        case XFS_DQTYPE_USER:
                /* uses the default lock class */
                break;
        case XFS_DQTYPE_GROUP:
                lockdep_set_class(&dqp->q_qlock, &xfs_dquot_group_class);
                break;
        case XFS_DQTYPE_PROJ:
                lockdep_set_class(&dqp->q_qlock, &xfs_dquot_project_class);
                break;
        default:
                ASSERT(0);
                break;
        }

        xfs_qm_dquot_logitem_init(dqp);

        XFS_STATS_INC(mp, xs_qm_dquot);
        return dqp;
}

/* Check the ondisk dquot's id and type match what the incore dquot expects. */
static bool
xfs_dquot_check_type(
        struct xfs_dquot        *dqp,
        struct xfs_disk_dquot   *ddqp)
{
        uint8_t                 ddqp_type;
        uint8_t                 dqp_type;

        ddqp_type = ddqp->d_type & XFS_DQTYPE_REC_MASK;
        dqp_type = xfs_dquot_type(dqp);

        if (be32_to_cpu(ddqp->d_id) != dqp->q_id)
                return false;

        /*
         * V5 filesystems always expect an exact type match.  V4 filesystems
         * expect an exact match for user dquots and for non-root group and
         * project dquots.
         */
        if (xfs_has_crc(dqp->q_mount) ||
            dqp_type == XFS_DQTYPE_USER || dqp->q_id != 0)
                return ddqp_type == dqp_type;

        /*
         * V4 filesystems support either group or project quotas, but not both
         * at the same time.  The non-user quota file can be switched between
         * group and project quota uses depending on the mount options, which
         * means that we can encounter the other type when we try to load quota
         * defaults.  Quotacheck will soon reset the entire quota file
         * (including the root dquot) anyway, but don't log scary corruption
         * reports to dmesg.
         */
        return ddqp_type == XFS_DQTYPE_GROUP || ddqp_type == XFS_DQTYPE_PROJ;
}

/* Copy the in-core quota fields in from the on-disk buffer. */
STATIC int
xfs_dquot_from_disk(
        struct xfs_dquot        *dqp,
        struct xfs_buf          *bp)
{
        struct xfs_dqblk        *dqb = xfs_buf_offset(bp, dqp->q_bufoffset);
        struct xfs_disk_dquot   *ddqp = &dqb->dd_diskdq;

        /*
         * Ensure that we got the type and ID we were looking for.
         * Everything else was checked by the dquot buffer verifier.
         */
        if (!xfs_dquot_check_type(dqp, ddqp)) {
                xfs_alert_tag(bp->b_mount, XFS_PTAG_VERIFIER_ERROR,
                          "Metadata corruption detected at %pS, quota %u",
                          __this_address, dqp->q_id);
                xfs_alert(bp->b_mount, "Unmount and run xfs_repair");
                xfs_dquot_mark_sick(dqp);
                return -EFSCORRUPTED;
        }

        /* copy everything from disk dquot to the incore dquot */
        dqp->q_type = ddqp->d_type;
        dqp->q_blk.hardlimit = be64_to_cpu(ddqp->d_blk_hardlimit);
        dqp->q_blk.softlimit = be64_to_cpu(ddqp->d_blk_softlimit);
        dqp->q_ino.hardlimit = be64_to_cpu(ddqp->d_ino_hardlimit);
        dqp->q_ino.softlimit = be64_to_cpu(ddqp->d_ino_softlimit);
        dqp->q_rtb.hardlimit = be64_to_cpu(ddqp->d_rtb_hardlimit);
        dqp->q_rtb.softlimit = be64_to_cpu(ddqp->d_rtb_softlimit);

        dqp->q_blk.count = be64_to_cpu(ddqp->d_bcount);
        dqp->q_ino.count = be64_to_cpu(ddqp->d_icount);
        dqp->q_rtb.count = be64_to_cpu(ddqp->d_rtbcount);

        dqp->q_blk.timer = xfs_dquot_from_disk_ts(ddqp, ddqp->d_btimer);
        dqp->q_ino.timer = xfs_dquot_from_disk_ts(ddqp, ddqp->d_itimer);
        dqp->q_rtb.timer = xfs_dquot_from_disk_ts(ddqp, ddqp->d_rtbtimer);

        /*
         * Reservation counters are defined as reservation plus current usage
         * to avoid having to add every time.
         */
        dqp->q_blk.reserved = dqp->q_blk.count;
        dqp->q_ino.reserved = dqp->q_ino.count;
        dqp->q_rtb.reserved = dqp->q_rtb.count;

        /* initialize the dquot speculative prealloc thresholds */
        xfs_dquot_set_prealloc_limits(dqp);
        return 0;
}

/* Copy the in-core quota fields into the on-disk buffer. */
void
xfs_dquot_to_disk(
        struct xfs_disk_dquot   *ddqp,
        struct xfs_dquot        *dqp)
{
        ddqp->d_magic = cpu_to_be16(XFS_DQUOT_MAGIC);
        ddqp->d_version = XFS_DQUOT_VERSION;
        ddqp->d_type = dqp->q_type;
        ddqp->d_id = cpu_to_be32(dqp->q_id);
        ddqp->d_pad0 = 0;
        ddqp->d_pad = 0;

        ddqp->d_blk_hardlimit = cpu_to_be64(dqp->q_blk.hardlimit);
        ddqp->d_blk_softlimit = cpu_to_be64(dqp->q_blk.softlimit);
        ddqp->d_ino_hardlimit = cpu_to_be64(dqp->q_ino.hardlimit);
        ddqp->d_ino_softlimit = cpu_to_be64(dqp->q_ino.softlimit);
        ddqp->d_rtb_hardlimit = cpu_to_be64(dqp->q_rtb.hardlimit);
        ddqp->d_rtb_softlimit = cpu_to_be64(dqp->q_rtb.softlimit);

        ddqp->d_bcount = cpu_to_be64(dqp->q_blk.count);
        ddqp->d_icount = cpu_to_be64(dqp->q_ino.count);
        ddqp->d_rtbcount = cpu_to_be64(dqp->q_rtb.count);

        ddqp->d_bwarns = 0;
        ddqp->d_iwarns = 0;
        ddqp->d_rtbwarns = 0;

        ddqp->d_btimer = xfs_dquot_to_disk_ts(dqp, dqp->q_blk.timer);
        ddqp->d_itimer = xfs_dquot_to_disk_ts(dqp, dqp->q_ino.timer);
        ddqp->d_rtbtimer = xfs_dquot_to_disk_ts(dqp, dqp->q_rtb.timer);
}

/*
 * Read in the ondisk dquot using dqtobp() then copy it to an incore version,
 * and release the buffer immediately.  If @can_alloc is true, fill any
 * holes in the on-disk metadata.
 */
static int
xfs_qm_dqread(
        struct xfs_mount        *mp,
        xfs_dqid_t              id,
        xfs_dqtype_t            type,
        bool                    can_alloc,
        struct xfs_dquot        **dqpp)
{
        struct xfs_dquot        *dqp;
        struct xfs_buf          *bp;
        int                     error;

        dqp = xfs_dquot_alloc(mp, id, type);
        trace_xfs_dqread(dqp);

        /* Try to read the buffer, allocating if necessary. */
        error = xfs_dquot_disk_read(mp, dqp, &bp);
        if (error == -ENOENT && can_alloc)
                error = xfs_dquot_disk_alloc(dqp, &bp);
        if (error)
                goto err;

        /*
         * At this point we should have a clean locked buffer.  Copy the data
         * to the incore dquot and release the buffer since the incore dquot
         * has its own locking protocol so we needn't tie up the buffer any
         * further.
         */
        ASSERT(xfs_buf_islocked(bp));
        error = xfs_dquot_from_disk(dqp, bp);
        xfs_buf_relse(bp);
        if (error)
                goto err;

        *dqpp = dqp;
        return error;

err:
        trace_xfs_dqread_fail(dqp);
        xfs_qm_dqdestroy(dqp);
        *dqpp = NULL;
        return error;
}

/*
 * Advance to the next id in the current chunk, or if at the
 * end of the chunk, skip ahead to first id in next allocated chunk
 * using the SEEK_DATA interface.
 */
static int
xfs_dq_get_next_id(
        struct xfs_mount        *mp,
        xfs_dqtype_t            type,
        xfs_dqid_t              *id)
{
        struct xfs_inode        *quotip = xfs_quota_inode(mp, type);
        xfs_dqid_t              next_id = *id + 1; /* simple advance */
        uint                    lock_flags;
        struct xfs_bmbt_irec    got;
        struct xfs_iext_cursor  cur;
        xfs_fsblock_t           start;
        int                     error = 0;

        /* If we'd wrap past the max ID, stop */
        if (next_id < *id)
                return -ENOENT;

        /* If new ID is within the current chunk, advancing it sufficed */
        if (next_id % mp->m_quotainfo->qi_dqperchunk) {
                *id = next_id;
                return 0;
        }

        /* Nope, next_id is now past the current chunk, so find the next one */
        start = (xfs_fsblock_t)next_id / mp->m_quotainfo->qi_dqperchunk;

        lock_flags = xfs_ilock_data_map_shared(quotip);
        error = xfs_iread_extents(NULL, quotip, XFS_DATA_FORK);
        if (error)
                return error;

        if (xfs_iext_lookup_extent(quotip, &quotip->i_df, start, &cur, &got)) {
                /* contiguous chunk, bump startoff for the id calculation */
                if (got.br_startoff < start)
                        got.br_startoff = start;
                *id = got.br_startoff * mp->m_quotainfo->qi_dqperchunk;
        } else {
                error = -ENOENT;
        }

        xfs_iunlock(quotip, lock_flags);

        return error;
}

/*
 * Look up the dquot in the in-core cache.  If found, the dquot is returned
 * locked and ready to go.
 */
static struct xfs_dquot *
xfs_qm_dqget_cache_lookup(
        struct xfs_mount        *mp,
        struct xfs_quotainfo    *qi,
        struct radix_tree_root  *tree,
        xfs_dqid_t              id)
{
        struct xfs_dquot        *dqp;

restart:
        mutex_lock(&qi->qi_tree_lock);
        dqp = radix_tree_lookup(tree, id);
        if (!dqp) {
                mutex_unlock(&qi->qi_tree_lock);
                XFS_STATS_INC(mp, xs_qm_dqcachemisses);
                return NULL;
        }

        xfs_dqlock(dqp);
        if (dqp->q_flags & XFS_DQFLAG_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(mp, xs_qm_dqcachehits);
        return dqp;
}

/*
 * Try to insert a new dquot into the in-core cache.  If an error occurs the
 * caller should throw away the dquot and start over.  Otherwise, the dquot
 * is returned locked (and held by the cache) as if there had been a cache
 * hit.
 *
 * The insert needs to be done under memalloc_nofs context because the radix
 * tree can do memory allocation during insert. The qi->qi_tree_lock is taken in
 * memory reclaim when freeing unused dquots, so we cannot have the radix tree
 * node allocation recursing into filesystem reclaim whilst we hold the
 * qi_tree_lock.
 */
static int
xfs_qm_dqget_cache_insert(
        struct xfs_mount        *mp,
        struct xfs_quotainfo    *qi,
        struct radix_tree_root  *tree,
        xfs_dqid_t              id,
        struct xfs_dquot        *dqp)
{
        unsigned int            nofs_flags;
        int                     error;

        nofs_flags = memalloc_nofs_save();
        mutex_lock(&qi->qi_tree_lock);
        error = radix_tree_insert(tree, id, dqp);
        if (unlikely(error)) {
                /* Duplicate found!  Caller must try again. */
                trace_xfs_dqget_dup(dqp);
                goto out_unlock;
        }

        /* Return a locked dquot to the caller, with a reference taken. */
        xfs_dqlock(dqp);
        dqp->q_nrefs = 1;
        qi->qi_dquots++;

out_unlock:
        mutex_unlock(&qi->qi_tree_lock);
        memalloc_nofs_restore(nofs_flags);
        return error;
}

/* Check our input parameters. */
static int
xfs_qm_dqget_checks(
        struct xfs_mount        *mp,
        xfs_dqtype_t            type)
{
        switch (type) {
        case XFS_DQTYPE_USER:
                if (!XFS_IS_UQUOTA_ON(mp))
                        return -ESRCH;
                return 0;
        case XFS_DQTYPE_GROUP:
                if (!XFS_IS_GQUOTA_ON(mp))
                        return -ESRCH;
                return 0;
        case XFS_DQTYPE_PROJ:
                if (!XFS_IS_PQUOTA_ON(mp))
                        return -ESRCH;
                return 0;
        default:
                WARN_ON_ONCE(0);
                return -EINVAL;
        }
}

/*
 * Given the file system, id, and type (UDQUOT/GDQUOT/PDQUOT), return a
 * locked dquot, doing an allocation (if requested) as needed.
 */
int
xfs_qm_dqget(
        struct xfs_mount        *mp,
        xfs_dqid_t              id,
        xfs_dqtype_t            type,
        bool                    can_alloc,
        struct xfs_dquot        **O_dqpp)
{
        struct xfs_quotainfo    *qi = mp->m_quotainfo;
        struct radix_tree_root  *tree = xfs_dquot_tree(qi, type);
        struct xfs_dquot        *dqp;
        int                     error;

        error = xfs_qm_dqget_checks(mp, type);
        if (error)
                return error;

restart:
        dqp = xfs_qm_dqget_cache_lookup(mp, qi, tree, id);
        if (dqp) {
                *O_dqpp = dqp;
                return 0;
        }

        error = xfs_qm_dqread(mp, id, type, can_alloc, &dqp);
        if (error)
                return error;

        error = xfs_qm_dqget_cache_insert(mp, qi, tree, id, dqp);
        if (error) {
                /*
                 * Duplicate found. Just throw away the new dquot and start
                 * over.
                 */
                xfs_qm_dqdestroy(dqp);
                XFS_STATS_INC(mp, xs_qm_dquot_dups);
                goto restart;
        }

        trace_xfs_dqget_miss(dqp);
        *O_dqpp = dqp;
        return 0;
}

/*
 * Given a dquot id and type, read and initialize a dquot from the on-disk
 * metadata.  This function is only for use during quota initialization so
 * it ignores the dquot cache assuming that the dquot shrinker isn't set up.
 * The caller is responsible for _qm_dqdestroy'ing the returned dquot.
 */
int
xfs_qm_dqget_uncached(
        struct xfs_mount        *mp,
        xfs_dqid_t              id,
        xfs_dqtype_t            type,
        struct xfs_dquot        **dqpp)
{
        int                     error;

        error = xfs_qm_dqget_checks(mp, type);
        if (error)
                return error;

        return xfs_qm_dqread(mp, id, type, 0, dqpp);
}

/* Return the quota id for a given inode and type. */
xfs_dqid_t
xfs_qm_id_for_quotatype(
        struct xfs_inode        *ip,
        xfs_dqtype_t            type)
{
        switch (type) {
        case XFS_DQTYPE_USER:
                return i_uid_read(VFS_I(ip));
        case XFS_DQTYPE_GROUP:
                return i_gid_read(VFS_I(ip));
        case XFS_DQTYPE_PROJ:
                return ip->i_projid;
        }
        ASSERT(0);
        return 0;
}

/*
 * Return the dquot for a given inode and type.  If @can_alloc is true, then
 * allocate blocks if needed.  The inode's ILOCK must be held and it must not
 * have already had an inode attached.
 */
int
xfs_qm_dqget_inode(
        struct xfs_inode        *ip,
        xfs_dqtype_t            type,
        bool                    can_alloc,
        struct xfs_dquot        **O_dqpp)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_quotainfo    *qi = mp->m_quotainfo;
        struct radix_tree_root  *tree = xfs_dquot_tree(qi, type);
        struct xfs_dquot        *dqp;
        xfs_dqid_t              id;
        int                     error;

        error = xfs_qm_dqget_checks(mp, type);
        if (error)
                return error;

        xfs_assert_ilocked(ip, XFS_ILOCK_EXCL);
        ASSERT(xfs_inode_dquot(ip, type) == NULL);
        ASSERT(!xfs_is_metadir_inode(ip));

        id = xfs_qm_id_for_quotatype(ip, type);

restart:
        dqp = xfs_qm_dqget_cache_lookup(mp, qi, tree, id);
        if (dqp) {
                *O_dqpp = dqp;
                return 0;
        }

        /*
         * 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.
         */
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        error = xfs_qm_dqread(mp, id, type, can_alloc, &dqp);
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        if (error)
                return error;

        /*
         * 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 -ESRCH;
        }

        error = xfs_qm_dqget_cache_insert(mp, qi, tree, id, dqp);
        if (error) {
                /*
                 * Duplicate found. Just throw away the new dquot and start
                 * over.
                 */
                xfs_qm_dqdestroy(dqp);
                XFS_STATS_INC(mp, xs_qm_dquot_dups);
                goto restart;
        }

dqret:
        xfs_assert_ilocked(ip, XFS_ILOCK_EXCL);
        trace_xfs_dqget_miss(dqp);
        *O_dqpp = dqp;
        return 0;
}

/*
 * Starting at @id and progressing upwards, look for an initialized incore
 * dquot, lock it, and return it.
 */
int
xfs_qm_dqget_next(
        struct xfs_mount        *mp,
        xfs_dqid_t              id,
        xfs_dqtype_t            type,
        struct xfs_dquot        **dqpp)
{
        struct xfs_dquot        *dqp;
        int                     error = 0;

        *dqpp = NULL;
        for (; !error; error = xfs_dq_get_next_id(mp, type, &id)) {
                error = xfs_qm_dqget(mp, id, type, false, &dqp);
                if (error == -ENOENT)
                        continue;
                else if (error != 0)
                        break;

                if (!XFS_IS_DQUOT_UNINITIALIZED(dqp)) {
                        *dqpp = dqp;
                        return 0;
                }

                xfs_qm_dqput(dqp);
        }

        return error;
}

/*
 * 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) {
                struct xfs_quotainfo    *qi = dqp->q_mount->m_quotainfo;
                trace_xfs_dqput_free(dqp);

                if (list_lru_add_obj(&qi->qi_lru, &dqp->q_lru))
                        XFS_STATS_INC(dqp->q_mount, xs_qm_dquot_unused);
        }
        xfs_dqunlock(dqp);
}

/*
 * Release a dquot. Flush it if dirty, then dqput() it.
 * dquot must not be locked.
 */
void
xfs_qm_dqrele(
        struct xfs_dquot        *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_log_item     *lip)
{
        struct xfs_dq_logitem   *qlip =
                        container_of(lip, struct xfs_dq_logitem, qli_item);
        struct xfs_dquot        *dqp = qlip->qli_dquot;
        struct xfs_ail          *ailp = lip->li_ailp;
        struct xfs_buf          *bp = NULL;
        xfs_lsn_t               tail_lsn;

        /*
         * 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 (test_bit(XFS_LI_IN_AIL, &lip->li_flags) &&
            (lip->li_lsn == qlip->qli_flush_lsn ||
             test_bit(XFS_LI_FAILED, &lip->li_flags))) {

                spin_lock(&ailp->ail_lock);
                xfs_clear_li_failed(lip);
                if (lip->li_lsn == qlip->qli_flush_lsn) {
                        /* xfs_ail_update_finish() drops the AIL lock */
                        tail_lsn = xfs_ail_delete_one(ailp, lip);
                        xfs_ail_update_finish(ailp, tail_lsn);
                } else {
                        spin_unlock(&ailp->ail_lock);
                }
        }

        /*
         * If this dquot hasn't been dirtied since initiating the last dqflush,
         * release the buffer reference.  We already unlinked this dquot item
         * from the buffer.
         */
        spin_lock(&qlip->qli_lock);
        if (!qlip->qli_dirty) {
                bp = lip->li_buf;
                lip->li_buf = NULL;
        }
        spin_unlock(&qlip->qli_lock);
        if (bp)
                xfs_buf_rele(bp);

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

void
xfs_buf_dquot_iodone(
        struct xfs_buf          *bp)
{
        struct xfs_log_item     *lip, *n;

        list_for_each_entry_safe(lip, n, &bp->b_li_list, li_bio_list) {
                list_del_init(&lip->li_bio_list);
                xfs_qm_dqflush_done(lip);
        }
}

/* Check incore dquot for errors before we flush. */
static xfs_failaddr_t
xfs_qm_dqflush_check(
        struct xfs_dquot        *dqp)
{
        xfs_dqtype_t            type = xfs_dquot_type(dqp);

        if (type != XFS_DQTYPE_USER &&
            type != XFS_DQTYPE_GROUP &&
            type != XFS_DQTYPE_PROJ)
                return __this_address;

        if (dqp->q_id == 0)
                return NULL;

        if (dqp->q_blk.softlimit && dqp->q_blk.count > dqp->q_blk.softlimit &&
            !dqp->q_blk.timer)
                return __this_address;

        if (dqp->q_ino.softlimit && dqp->q_ino.count > dqp->q_ino.softlimit &&
            !dqp->q_ino.timer)
                return __this_address;

        if (dqp->q_rtb.softlimit && dqp->q_rtb.count > dqp->q_rtb.softlimit &&
            !dqp->q_rtb.timer)
                return __this_address;

        /* bigtime flag should never be set on root dquots */
        if (dqp->q_type & XFS_DQTYPE_BIGTIME) {
                if (!xfs_has_bigtime(dqp->q_mount))
                        return __this_address;
                if (dqp->q_id == 0)
                        return __this_address;
        }

        return NULL;
}

/*
 * Get the buffer containing the on-disk dquot.
 *
 * Requires dquot flush lock, will clear the dirty flag, delete the quota log
 * item from the AIL, and shut down the system if something goes wrong.
 */
static int
xfs_dquot_read_buf(
        struct xfs_trans        *tp,
        struct xfs_dquot        *dqp,
        struct xfs_buf          **bpp)
{
        struct xfs_mount        *mp = dqp->q_mount;
        struct xfs_buf          *bp = NULL;
        int                     error;

        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, dqp->q_blkno,
                                   mp->m_quotainfo->qi_dqchunklen, 0,
                                   &bp, &xfs_dquot_buf_ops);
        if (xfs_metadata_is_sick(error))
                xfs_dquot_mark_sick(dqp);
        if (error)
                goto out_abort;

        *bpp = bp;
        return 0;

out_abort:
        dqp->q_flags &= ~XFS_DQFLAG_DIRTY;
        xfs_trans_ail_delete(&dqp->q_logitem.qli_item, 0);
        xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
        return error;
}

/*
 * Attach a dquot buffer to this dquot to avoid allocating a buffer during a
 * dqflush, since dqflush can be called from reclaim context.  Caller must hold
 * the dqlock.
 */
int
xfs_dquot_attach_buf(
        struct xfs_trans        *tp,
        struct xfs_dquot        *dqp)
{
        struct xfs_dq_logitem   *qlip = &dqp->q_logitem;
        struct xfs_log_item     *lip = &qlip->qli_item;
        int                     error;

        spin_lock(&qlip->qli_lock);
        if (!lip->li_buf) {
                struct xfs_buf  *bp = NULL;

                spin_unlock(&qlip->qli_lock);
                error = xfs_dquot_read_buf(tp, dqp, &bp);
                if (error)
                        return error;

                /*
                 * Hold the dquot buffer so that we retain our ref to it after
                 * detaching it from the transaction, then give that ref to the
                 * dquot log item so that the AIL does not have to read the
                 * dquot buffer to push this item.
                 */
                xfs_buf_hold(bp);
                xfs_trans_brelse(tp, bp);

                spin_lock(&qlip->qli_lock);
                lip->li_buf = bp;
        }
        qlip->qli_dirty = true;
        spin_unlock(&qlip->qli_lock);

        return 0;
}

/*
 * Get a new reference the dquot buffer attached to this dquot for a dqflush
 * operation.
 *
 * Returns 0 and a NULL bp if none was attached to the dquot; 0 and a locked
 * bp; or -EAGAIN if the buffer could not be locked.
 */
int
xfs_dquot_use_attached_buf(
        struct xfs_dquot        *dqp,
        struct xfs_buf          **bpp)
{
        struct xfs_buf          *bp = dqp->q_logitem.qli_item.li_buf;

        /*
         * A NULL buffer can happen if the dquot dirty flag was set but the
         * filesystem shut down before transaction commit happened.  In that
         * case we're not going to flush anyway.
         */
        if (!bp) {
                ASSERT(xfs_is_shutdown(dqp->q_mount));

                *bpp = NULL;
                return 0;
        }

        if (!xfs_buf_trylock(bp))
                return -EAGAIN;

        xfs_buf_hold(bp);
        *bpp = bp;
        return 0;
}

/*
 * 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          *bp)
{
        struct xfs_mount        *mp = dqp->q_mount;
        struct xfs_dq_logitem   *qlip = &dqp->q_logitem;
        struct xfs_log_item     *lip = &qlip->qli_item;
        struct xfs_dqblk        *dqblk;
        xfs_failaddr_t          fa;
        int                     error;

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

        trace_xfs_dqflush(dqp);

        xfs_qm_dqunpin_wait(dqp);

        fa = xfs_qm_dqflush_check(dqp);
        if (fa) {
                xfs_alert(mp, "corrupt dquot ID 0x%x in memory at %pS",
                                dqp->q_id, fa);
                xfs_dquot_mark_sick(dqp);
                error = -EFSCORRUPTED;
                goto out_abort;
        }

        /* Flush the incore dquot to the ondisk buffer. */
        dqblk = xfs_buf_offset(bp, dqp->q_bufoffset);
        xfs_dquot_to_disk(&dqblk->dd_diskdq, dqp);

        /*
         * Clear the dirty field and remember the flush lsn for later use.
         */
        dqp->q_flags &= ~XFS_DQFLAG_DIRTY;

        /*
         * We hold the dquot lock, so nobody can dirty it while we're
         * scheduling the write out.  Clear the dirty-since-flush flag.
         */
        spin_lock(&qlip->qli_lock);
        qlip->qli_dirty = false;
        spin_unlock(&qlip->qli_lock);

        xfs_trans_ail_copy_lsn(mp->m_ail, &qlip->qli_flush_lsn, &lip->li_lsn);

        /*
         * copy the lsn into the on-disk dquot now while we have the in memory
         * dquot here. This can't be done later in the write verifier as we
         * can't get access to the log item at that point in time.
         *
         * We also calculate the CRC here so that the on-disk dquot in the
         * buffer always has a valid CRC. This ensures there is no possibility
         * of a dquot without an up-to-date CRC getting to disk.
         */
        if (xfs_has_crc(mp)) {
                dqblk->dd_lsn = cpu_to_be64(lip->li_lsn);
                xfs_update_cksum((char *)dqblk, sizeof(struct xfs_dqblk),
                                 XFS_DQUOT_CRC_OFF);
        }

        /*
         * Attach the dquot to the buffer so that we can remove this dquot from
         * the AIL and release the flush lock once the dquot is synced to disk.
         */
        bp->b_iodone = xfs_buf_dquot_iodone;
        list_add_tail(&lip->li_bio_list, &bp->b_li_list);

        /*
         * 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);
        return 0;

out_abort:
        dqp->q_flags &= ~XFS_DQFLAG_DIRTY;
        xfs_trans_ail_delete(lip, 0);
        xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
        xfs_dqfunlock(dqp);
        return error;
}

/*
 * Lock two xfs_dquot structures.
 *
 * To avoid deadlocks we always lock the quota structure with
 * the lowerd id first.
 */
void
xfs_dqlock2(
        struct xfs_dquot        *d1,
        struct xfs_dquot        *d2)
{
        if (d1 && d2) {
                ASSERT(d1 != d2);
                if (d1->q_id > d2->q_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);
        }
}

static int
xfs_dqtrx_cmp(
        const void              *a,
        const void              *b)
{
        const struct xfs_dqtrx  *qa = a;
        const struct xfs_dqtrx  *qb = b;

        if (qa->qt_dquot->q_id > qb->qt_dquot->q_id)
                return 1;
        if (qa->qt_dquot->q_id < qb->qt_dquot->q_id)
                return -1;
        return 0;
}

void
xfs_dqlockn(
        struct xfs_dqtrx        *q)
{
        unsigned int            i;

        BUILD_BUG_ON(XFS_QM_TRANS_MAXDQS > MAX_LOCKDEP_SUBCLASSES);

        /* Sort in order of dquot id, do not allow duplicates */
        for (i = 0; i < XFS_QM_TRANS_MAXDQS && q[i].qt_dquot != NULL; i++) {
                unsigned int    j;

                for (j = 0; j < i; j++)
                        ASSERT(q[i].qt_dquot != q[j].qt_dquot);
        }
        if (i == 0)
                return;

        sort(q, i, sizeof(struct xfs_dqtrx), xfs_dqtrx_cmp, NULL);

        mutex_lock(&q[0].qt_dquot->q_qlock);
        for (i = 1; i < XFS_QM_TRANS_MAXDQS && q[i].qt_dquot != NULL; i++)
                mutex_lock_nested(&q[i].qt_dquot->q_qlock,
                                XFS_QLOCK_NESTED + i - 1);
}

int __init
xfs_qm_init(void)
{
        xfs_dquot_cache = kmem_cache_create("xfs_dquot",
                                          sizeof(struct xfs_dquot),
                                          0, 0, NULL);
        if (!xfs_dquot_cache)
                goto out;

        xfs_dqtrx_cache = kmem_cache_create("xfs_dqtrx",
                                             sizeof(struct xfs_dquot_acct),
                                             0, 0, NULL);
        if (!xfs_dqtrx_cache)
                goto out_free_dquot_cache;

        return 0;

out_free_dquot_cache:
        kmem_cache_destroy(xfs_dquot_cache);
out:
        return -ENOMEM;
}

void
xfs_qm_exit(void)
{
        kmem_cache_destroy(xfs_dqtrx_cache);
        kmem_cache_destroy(xfs_dquot_cache);
}