genirq/timings: Optimize the period detection speed

[linux-2.6-microblaze.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_bmap_util.h"
#include "xfs_alloc.h"
#include "xfs_quota.h"
#include "xfs_error.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_cksum.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_bmap_btree.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_zone                *xfs_qm_dqtrxzone;
static struct kmem_zone         *xfs_qm_dqzone;

static struct lock_class_key xfs_dquot_group_class;
static struct lock_class_key xfs_dquot_project_class;

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

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

        XFS_STATS_DEC(dqp->q_mount, xs_qm_dquot);
        kmem_zone_free(xfs_qm_dqzone, 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_mount        *mp,
        struct xfs_dquot        *dq)
{
        struct xfs_quotainfo    *q = mp->m_quotainfo;
        struct xfs_disk_dquot   *d = &dq->q_core;
        struct xfs_def_quota    *defq;
        int                     prealloc = 0;

        ASSERT(d->d_id);
        defq = xfs_get_defquota(dq, q);

        if (defq->bsoftlimit && !d->d_blk_softlimit) {
                d->d_blk_softlimit = cpu_to_be64(defq->bsoftlimit);
                prealloc = 1;
        }
        if (defq->bhardlimit && !d->d_blk_hardlimit) {
                d->d_blk_hardlimit = cpu_to_be64(defq->bhardlimit);
                prealloc = 1;
        }
        if (defq->isoftlimit && !d->d_ino_softlimit)
                d->d_ino_softlimit = cpu_to_be64(defq->isoftlimit);
        if (defq->ihardlimit && !d->d_ino_hardlimit)
                d->d_ino_hardlimit = cpu_to_be64(defq->ihardlimit);
        if (defq->rtbsoftlimit && !d->d_rtb_softlimit)
                d->d_rtb_softlimit = cpu_to_be64(defq->rtbsoftlimit);
        if (defq->rtbhardlimit && !d->d_rtb_hardlimit)
                d->d_rtb_hardlimit = cpu_to_be64(defq->rtbhardlimit);

        if (prealloc)
                xfs_dquot_set_prealloc_limits(dq);
}

/*
 * Check the limits and timers of a dquot and start or reset timers
 * if necessary.
 * This gets called even when quota enforcement is OFF, which makes our
 * life a little less complicated. (We just don't reject any quota
 * reservations in that case, when enforcement is off).
 * We also return 0 as the values of the timers in Q_GETQUOTA calls, when
 * enforcement's off.
 * In contrast, warnings are a little different in that they don't
 * 'automatically' get started when limits get exceeded.  They do
 * get reset to zero, however, when we find the count to be under
 * the soft limit (they are only ever set non-zero via userspace).
 */
void
xfs_qm_adjust_dqtimers(
        xfs_mount_t             *mp,
        xfs_disk_dquot_t        *d)
{
        ASSERT(d->d_id);

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

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

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

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

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

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

        d = bp->b_addr;

        /*
         * ID of the first dquot in the block - id's are zero based.
         */
        curid = id - (id % q->qi_dqperchunk);
        memset(d, 0, BBTOB(q->qi_dqchunklen));
        for (i = 0; i < q->qi_dqperchunk; i++, d++, curid++) {
                d->dd_diskdq.d_magic = cpu_to_be16(XFS_DQUOT_MAGIC);
                d->dd_diskdq.d_version = XFS_DQUOT_VERSION;
                d->dd_diskdq.d_id = cpu_to_be32(curid);
                d->dd_diskdq.d_flags = type;
                if (xfs_sb_version_hascrc(&mp->m_sb)) {
                        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,
                            (type & XFS_DQ_USER ? XFS_BLF_UDQUOT_BUF :
                            ((type & XFS_DQ_PROJ) ? XFS_BLF_PDQUOT_BUF :
                             XFS_BLF_GDQUOT_BUF)));
        xfs_trans_log_buf(tp, bp, 0, BBTOB(q->qi_dqchunklen) - 1);
}

/*
 * 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)
{
        uint64_t space;

        dqp->q_prealloc_hi_wmark = be64_to_cpu(dqp->q_core.d_blk_hardlimit);
        dqp->q_prealloc_lo_wmark = be64_to_cpu(dqp->q_core.d_blk_softlimit);
        if (!dqp->q_prealloc_lo_wmark) {
                dqp->q_prealloc_lo_wmark = dqp->q_prealloc_hi_wmark;
                do_div(dqp->q_prealloc_lo_wmark, 100);
                dqp->q_prealloc_lo_wmark *= 95;
        }

        space = dqp->q_prealloc_hi_wmark;

        do_div(space, 100);
        dqp->q_low_space[XFS_QLOWSP_1_PCNT] = space;
        dqp->q_low_space[XFS_QLOWSP_3_PCNT] = space * 3;
        dqp->q_low_space[XFS_QLOWSP_5_PCNT] = space * 5;
}

/*
 * 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_trans        **tpp,
        struct xfs_dquot        *dqp,
        struct xfs_buf          **bpp)
{
        struct xfs_bmbt_irec    map;
        struct xfs_trans        *tp = *tpp;
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_buf          *bp;
        struct xfs_inode        *quotip = xfs_quota_inode(mp, dqp->dq_flags);
        int                     nmaps = 1;
        int                     error;

        trace_xfs_dqalloc(dqp);

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

        /* Create the block mapping. */
        xfs_trans_ijoin(tp, quotip, XFS_ILOCK_EXCL);
        error = xfs_bmapi_write(tp, quotip, dqp->q_fileoffset,
                        XFS_DQUOT_CLUSTER_SIZE_FSB, XFS_BMAPI_METADATA,
                        XFS_QM_DQALLOC_SPACE_RES(mp), &map, &nmaps);
        if (error)
                return error;
        ASSERT(map.br_blockcount == XFS_DQUOT_CLUSTER_SIZE_FSB);
        ASSERT(nmaps == 1);
        ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
               (map.br_startblock != HOLESTARTBLOCK));

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

        /* now we can just get the buffer (there's nothing to read yet) */
        bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, dqp->q_blkno,
                        mp->m_quotainfo->qi_dqchunklen, 0);
        if (!bp)
                return -ENOMEM;
        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, mp, be32_to_cpu(dqp->q_core.d_id),
                              dqp->dq_flags & XFS_DQ_ALLTYPES, 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.
         */
        xfs_trans_bhold(tp, bp);
        error = xfs_defer_finish(tpp);
        if (error) {
                xfs_trans_bhold_release(*tpp, bp);
                xfs_trans_brelse(*tpp, bp);
                return error;
        }
        *bpp = bp;
        return 0;
}

/*
 * 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;
        struct xfs_inode        *quotip = xfs_quota_inode(mp, dqp->dq_flags);
        uint                    lock_mode;
        int                     nmaps = 1;
        int                     error;

        lock_mode = xfs_ilock_data_map_shared(quotip);
        if (!xfs_this_quota_on(mp, dqp->dq_flags)) {
                /*
                 * 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 (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,
        uint                    type)
{
        struct xfs_dquot        *dqp;

        dqp = kmem_zone_zalloc(xfs_qm_dqzone, KM_SLEEP);

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

        /*
         * 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_DQ_USER:
                /* uses the default lock class */
                break;
        case XFS_DQ_GROUP:
                lockdep_set_class(&dqp->q_qlock, &xfs_dquot_group_class);
                break;
        case XFS_DQ_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;
}

/* Copy the in-core quota fields in from the on-disk buffer. */
STATIC void
xfs_dquot_from_disk(
        struct xfs_dquot        *dqp,
        struct xfs_buf          *bp)
{
        struct xfs_disk_dquot   *ddqp = bp->b_addr + dqp->q_bufoffset;

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

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

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

/* Allocate and initialize the dquot buffer for this in-core dquot. */
static int
xfs_qm_dqread_alloc(
        struct xfs_mount        *mp,
        struct xfs_dquot        *dqp,
        struct xfs_buf          **bpp)
{
        struct xfs_trans        *tp;
        int                     error;

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

        error = xfs_dquot_disk_alloc(&tp, dqp, bpp);
        if (error)
                goto err_cancel;

        error = xfs_trans_commit(tp);
        if (error) {
                /*
                 * Buffer was held to the transaction, so we have to unlock it
                 * manually here because we're not passing it back.
                 */
                xfs_buf_relse(*bpp);
                *bpp = NULL;
                goto err;
        }
        return 0;

err_cancel:
        xfs_trans_cancel(tp);
err:
        return error;
}

/*
 * 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,
        uint                    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_qm_dqread_alloc(mp, 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));
        xfs_dquot_from_disk(dqp, bp);

        xfs_buf_relse(bp);
        *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,
        uint                    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);
        if (!(quotip->i_df.if_flags & XFS_IFEXTENTS)) {
                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->dq_flags & XFS_DQ_FREEING) {
                xfs_dqunlock(dqp);
                mutex_unlock(&qi->qi_tree_lock);
                trace_xfs_dqget_freeing(dqp);
                delay(1);
                goto restart;
        }

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

        trace_xfs_dqget_hit(dqp);
        XFS_STATS_INC(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.
 */
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)
{
        int                     error;

        mutex_lock(&qi->qi_tree_lock);
        error = radix_tree_insert(tree, id, dqp);
        if (unlikely(error)) {
                /* Duplicate found!  Caller must try again. */
                WARN_ON(error != -EEXIST);
                mutex_unlock(&qi->qi_tree_lock);
                trace_xfs_dqget_dup(dqp);
                return error;
        }

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

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

        return 0;
}

/* Check our input parameters. */
static int
xfs_qm_dqget_checks(
        struct xfs_mount        *mp,
        uint                    type)
{
        if (WARN_ON_ONCE(!XFS_IS_QUOTA_RUNNING(mp)))
                return -ESRCH;

        switch (type) {
        case XFS_DQ_USER:
                if (!XFS_IS_UQUOTA_ON(mp))
                        return -ESRCH;
                return 0;
        case XFS_DQ_GROUP:
                if (!XFS_IS_GQUOTA_ON(mp))
                        return -ESRCH;
                return 0;
        case XFS_DQ_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), return a a locked
 * dquot, doing an allocation (if requested) as needed.
 */
int
xfs_qm_dqget(
        struct xfs_mount        *mp,
        xfs_dqid_t              id,
        uint                    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,
        uint                    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,
        uint                    type)
{
        switch (type) {
        case XFS_DQ_USER:
                return ip->i_d.di_uid;
        case XFS_DQ_GROUP:
                return ip->i_d.di_gid;
        case XFS_DQ_PROJ:
                return xfs_get_projid(ip);
        }
        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,
        uint                    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;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(xfs_inode_dquot(ip, type) == NULL);

        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:
        ASSERT(xfs_isilocked(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,
        uint                    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(&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(
        xfs_dquot_t     *dqp)
{
        if (!dqp)
                return;

        trace_xfs_dqrele(dqp);

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

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

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

                /* xfs_trans_ail_delete() drops the AIL lock. */
                spin_lock(&ailp->ail_lock);
                if (lip->li_lsn == qip->qli_flush_lsn) {
                        xfs_trans_ail_delete(ailp, lip, SHUTDOWN_CORRUPT_INCORE);
                } else {
                        /*
                         * Clear the failed state since we are about to drop the
                         * flush lock
                         */
                        xfs_clear_li_failed(lip);
                        spin_unlock(&ailp->ail_lock);
                }
        }

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

/*
 * Write a modified dquot to disk.
 * The dquot must be locked and the flush lock too taken by caller.
 * The flush lock will not be unlocked until the dquot reaches the disk,
 * but the dquot is free to be unlocked and modified by the caller
 * in the interim. Dquot is still locked on return. This behavior is
 * identical to that of inodes.
 */
int
xfs_qm_dqflush(
        struct xfs_dquot        *dqp,
        struct xfs_buf          **bpp)
{
        struct xfs_mount        *mp = dqp->q_mount;
        struct xfs_buf          *bp;
        struct xfs_dqblk        *dqb;
        struct xfs_disk_dquot   *ddqp;
        xfs_failaddr_t          fa;
        int                     error;

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

        trace_xfs_dqflush(dqp);

        *bpp = NULL;

        xfs_qm_dqunpin_wait(dqp);

        /*
         * This may have been unpinned because the filesystem is shutting
         * down forcibly. If that's the case we must not write this dquot
         * to disk, because the log record didn't make it to disk.
         *
         * We also have to remove the log item from the AIL in this case,
         * as we wait for an emptry AIL as part of the unmount process.
         */
        if (XFS_FORCED_SHUTDOWN(mp)) {
                struct xfs_log_item     *lip = &dqp->q_logitem.qli_item;
                dqp->dq_flags &= ~XFS_DQ_DIRTY;

                xfs_trans_ail_remove(lip, SHUTDOWN_CORRUPT_INCORE);

                error = -EIO;
                goto out_unlock;
        }

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

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

        /*
         * A simple sanity check in case we got a corrupted dquot.
         */
        fa = xfs_dqblk_verify(mp, dqb, be32_to_cpu(ddqp->d_id), 0);
        if (fa) {
                xfs_alert(mp, "corrupt dquot ID 0x%x in memory at %pS",
                                be32_to_cpu(ddqp->d_id), fa);
                xfs_buf_relse(bp);
                xfs_dqfunlock(dqp);
                xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
                return -EIO;
        }

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

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

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

        /*
         * 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_sb_version_hascrc(&mp->m_sb)) {
                dqb->dd_lsn = cpu_to_be64(dqp->q_logitem.qli_item.li_lsn);
                xfs_update_cksum((char *)dqb, sizeof(struct xfs_dqblk),
                                 XFS_DQUOT_CRC_OFF);
        }

        /*
         * Attach an iodone routine so that we can remove this dquot from the
         * AIL and release the flush lock once the dquot is synced to disk.
         */
        xfs_buf_attach_iodone(bp, xfs_qm_dqflush_done,
                                  &dqp->q_logitem.qli_item);

        /*
         * If the buffer is pinned then push on the log so we won't
         * get stuck waiting in the write for too long.
         */
        if (xfs_buf_ispinned(bp)) {
                trace_xfs_dqflush_force(dqp);
                xfs_log_force(mp, 0);
        }

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

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

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

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

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

        return 0;

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

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

/*
 * Iterate every dquot of a particular type.  The caller must ensure that the
 * particular quota type is active.  iter_fn can return negative error codes,
 * or XFS_BTREE_QUERY_RANGE_ABORT to indicate that it wants to stop iterating.
 */
int
xfs_qm_dqiterate(
        struct xfs_mount        *mp,
        uint                    dqtype,
        xfs_qm_dqiterate_fn     iter_fn,
        void                    *priv)
{
        struct xfs_dquot        *dq;
        xfs_dqid_t              id = 0;
        int                     error;

        do {
                error = xfs_qm_dqget_next(mp, id, dqtype, &dq);
                if (error == -ENOENT)
                        return 0;
                if (error)
                        return error;

                error = iter_fn(dq, dqtype, priv);
                id = be32_to_cpu(dq->q_core.d_id);
                xfs_qm_dqput(dq);
                id++;
        } while (error == 0 && id != 0);

        return error;
}