xfs: sanitize qh_lock wrappers

[linux-2.6/linux-2.6-openrd.git] / fs / xfs / quota / xfs_qm.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_alloc.h"
#include "xfs_dmapi.h"
#include "xfs_quota.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_itable.h"
#include "xfs_rtalloc.h"
#include "xfs_error.h"
#include "xfs_bmap.h"
#include "xfs_rw.h"
#include "xfs_acl.h"
#include "xfs_attr.h"
#include "xfs_buf_item.h"
#include "xfs_trans_space.h"
#include "xfs_utils.h"
#include "xfs_qm.h"

/*
 * The global quota manager. There is only one of these for the entire
 * system, _not_ one per file system. XQM keeps track of the overall
 * quota functionality, including maintaining the freelist and hash
 * tables of dquots.
 */
mutex_t         xfs_Gqm_lock;
struct xfs_qm   *xfs_Gqm;
uint            ndquot;

kmem_zone_t     *qm_dqzone;
kmem_zone_t     *qm_dqtrxzone;

static cred_t   xfs_zerocr;

STATIC void     xfs_qm_list_init(xfs_dqlist_t *, char *, int);
STATIC void     xfs_qm_list_destroy(xfs_dqlist_t *);

STATIC void     xfs_qm_freelist_init(xfs_frlist_t *);
STATIC void     xfs_qm_freelist_destroy(xfs_frlist_t *);

STATIC int      xfs_qm_init_quotainos(xfs_mount_t *);
STATIC int      xfs_qm_init_quotainfo(xfs_mount_t *);
STATIC int      xfs_qm_shake(int, gfp_t);

static struct shrinker xfs_qm_shaker = {
        .shrink = xfs_qm_shake,
        .seeks = DEFAULT_SEEKS,
};

#ifdef DEBUG
extern mutex_t  qcheck_lock;
#endif

#ifdef QUOTADEBUG
#define XQM_LIST_PRINT(l, NXT, title) \
{ \
        xfs_dquot_t     *dqp; int i = 0; \
        cmn_err(CE_DEBUG, "%s (#%d)", title, (int) (l)->qh_nelems); \
        for (dqp = (l)->qh_next; dqp != NULL; dqp = dqp->NXT) { \
                cmn_err(CE_DEBUG, "   %d.  \"%d (%s)\"   " \
                                  "bcnt = %d, icnt = %d, refs = %d", \
                        ++i, (int) be32_to_cpu(dqp->q_core.d_id), \
                        DQFLAGTO_TYPESTR(dqp),       \
                        (int) be64_to_cpu(dqp->q_core.d_bcount), \
                        (int) be64_to_cpu(dqp->q_core.d_icount), \
                        (int) dqp->q_nrefs);  } \
}
#else
#define XQM_LIST_PRINT(l, NXT, title) do { } while (0)
#endif

/*
 * Initialize the XQM structure.
 * Note that there is not one quota manager per file system.
 */
STATIC struct xfs_qm *
xfs_Gqm_init(void)
{
        xfs_dqhash_t    *udqhash, *gdqhash;
        xfs_qm_t        *xqm;
        size_t          hsize;
        uint            i;

        /*
         * Initialize the dquot hash tables.
         */
        udqhash = kmem_zalloc_greedy(&hsize,
                                     XFS_QM_HASHSIZE_LOW * sizeof(xfs_dqhash_t),
                                     XFS_QM_HASHSIZE_HIGH * sizeof(xfs_dqhash_t),
                                     KM_SLEEP | KM_MAYFAIL | KM_LARGE);
        gdqhash = kmem_zalloc(hsize, KM_SLEEP | KM_LARGE);
        hsize /= sizeof(xfs_dqhash_t);
        ndquot = hsize << 8;

        xqm = kmem_zalloc(sizeof(xfs_qm_t), KM_SLEEP);
        xqm->qm_dqhashmask = hsize - 1;
        xqm->qm_usr_dqhtable = udqhash;
        xqm->qm_grp_dqhtable = gdqhash;
        ASSERT(xqm->qm_usr_dqhtable != NULL);
        ASSERT(xqm->qm_grp_dqhtable != NULL);

        for (i = 0; i < hsize; i++) {
                xfs_qm_list_init(&(xqm->qm_usr_dqhtable[i]), "uxdqh", i);
                xfs_qm_list_init(&(xqm->qm_grp_dqhtable[i]), "gxdqh", i);
        }

        /*
         * Freelist of all dquots of all file systems
         */
        xfs_qm_freelist_init(&(xqm->qm_dqfreelist));

        /*
         * dquot zone. we register our own low-memory callback.
         */
        if (!qm_dqzone) {
                xqm->qm_dqzone = kmem_zone_init(sizeof(xfs_dquot_t),
                                                "xfs_dquots");
                qm_dqzone = xqm->qm_dqzone;
        } else
                xqm->qm_dqzone = qm_dqzone;

        register_shrinker(&xfs_qm_shaker);

        /*
         * The t_dqinfo portion of transactions.
         */
        if (!qm_dqtrxzone) {
                xqm->qm_dqtrxzone = kmem_zone_init(sizeof(xfs_dquot_acct_t),
                                                   "xfs_dqtrx");
                qm_dqtrxzone = xqm->qm_dqtrxzone;
        } else
                xqm->qm_dqtrxzone = qm_dqtrxzone;

        atomic_set(&xqm->qm_totaldquots, 0);
        xqm->qm_dqfree_ratio = XFS_QM_DQFREE_RATIO;
        xqm->qm_nrefs = 0;
#ifdef DEBUG
        mutex_init(&qcheck_lock);
#endif
        return xqm;
}

/*
 * Destroy the global quota manager when its reference count goes to zero.
 */
STATIC void
xfs_qm_destroy(
        struct xfs_qm   *xqm)
{
        int             hsize, i;

        ASSERT(xqm != NULL);
        ASSERT(xqm->qm_nrefs == 0);
        unregister_shrinker(&xfs_qm_shaker);
        hsize = xqm->qm_dqhashmask + 1;
        for (i = 0; i < hsize; i++) {
                xfs_qm_list_destroy(&(xqm->qm_usr_dqhtable[i]));
                xfs_qm_list_destroy(&(xqm->qm_grp_dqhtable[i]));
        }
        kmem_free(xqm->qm_usr_dqhtable);
        kmem_free(xqm->qm_grp_dqhtable);
        xqm->qm_usr_dqhtable = NULL;
        xqm->qm_grp_dqhtable = NULL;
        xqm->qm_dqhashmask = 0;
        xfs_qm_freelist_destroy(&(xqm->qm_dqfreelist));
#ifdef DEBUG
        mutex_destroy(&qcheck_lock);
#endif
        kmem_free(xqm);
}

/*
 * Called at mount time to let XQM know that another file system is
 * starting quotas. This isn't crucial information as the individual mount
 * structures are pretty independent, but it helps the XQM keep a
 * global view of what's going on.
 */
/* ARGSUSED */
STATIC int
xfs_qm_hold_quotafs_ref(
        struct xfs_mount *mp)
{
        /*
         * Need to lock the xfs_Gqm structure for things like this. For example,
         * the structure could disappear between the entry to this routine and
         * a HOLD operation if not locked.
         */
        mutex_lock(&xfs_Gqm_lock);

        if (xfs_Gqm == NULL)
                xfs_Gqm = xfs_Gqm_init();
        /*
         * We can keep a list of all filesystems with quotas mounted for
         * debugging and statistical purposes, but ...
         * Just take a reference and get out.
         */
        xfs_Gqm->qm_nrefs++;
        mutex_unlock(&xfs_Gqm_lock);

        return 0;
}


/*
 * Release the reference that a filesystem took at mount time,
 * so that we know when we need to destroy the entire quota manager.
 */
/* ARGSUSED */
STATIC void
xfs_qm_rele_quotafs_ref(
        struct xfs_mount *mp)
{
        xfs_dquot_t     *dqp, *nextdqp;

        ASSERT(xfs_Gqm);
        ASSERT(xfs_Gqm->qm_nrefs > 0);

        /*
         * Go thru the freelist and destroy all inactive dquots.
         */
        xfs_qm_freelist_lock(xfs_Gqm);

        for (dqp = xfs_Gqm->qm_dqfreelist.qh_next;
             dqp != (xfs_dquot_t *)&(xfs_Gqm->qm_dqfreelist); ) {
                xfs_dqlock(dqp);
                nextdqp = dqp->dq_flnext;
                if (dqp->dq_flags & XFS_DQ_INACTIVE) {
                        ASSERT(dqp->q_mount == NULL);
                        ASSERT(! XFS_DQ_IS_DIRTY(dqp));
                        ASSERT(dqp->HL_PREVP == NULL);
                        ASSERT(dqp->MPL_PREVP == NULL);
                        XQM_FREELIST_REMOVE(dqp);
                        xfs_dqunlock(dqp);
                        xfs_qm_dqdestroy(dqp);
                } else {
                        xfs_dqunlock(dqp);
                }
                dqp = nextdqp;
        }
        xfs_qm_freelist_unlock(xfs_Gqm);

        /*
         * Destroy the entire XQM. If somebody mounts with quotaon, this'll
         * be restarted.
         */
        mutex_lock(&xfs_Gqm_lock);
        if (--xfs_Gqm->qm_nrefs == 0) {
                xfs_qm_destroy(xfs_Gqm);
                xfs_Gqm = NULL;
        }
        mutex_unlock(&xfs_Gqm_lock);
}

/*
 * Just destroy the quotainfo structure.
 */
void
xfs_qm_unmount_quotadestroy(
        xfs_mount_t     *mp)
{
        if (mp->m_quotainfo)
                xfs_qm_destroy_quotainfo(mp);
}


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

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

        ASSERT(XFS_IS_QUOTA_RUNNING(mp));

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

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

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

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

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

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

/*
 * Flush all dquots of the given file system to disk. The dquots are
 * _not_ purged from memory here, just their data written to disk.
 */
STATIC int
xfs_qm_dqflush_all(
        xfs_mount_t     *mp,
        int             flags)
{
        int             recl;
        xfs_dquot_t     *dqp;
        int             niters;
        int             error;

        if (mp->m_quotainfo == NULL)
                return 0;
        niters = 0;
again:
        xfs_qm_mplist_lock(mp);
        FOREACH_DQUOT_IN_MP(dqp, mp) {
                xfs_dqlock(dqp);
                if (! XFS_DQ_IS_DIRTY(dqp)) {
                        xfs_dqunlock(dqp);
                        continue;
                }
                xfs_dqtrace_entry(dqp, "FLUSHALL: DQDIRTY");
                /* XXX a sentinel would be better */
                recl = XFS_QI_MPLRECLAIMS(mp);
                if (!xfs_dqflock_nowait(dqp)) {
                        /*
                         * If we can't grab the flush lock then check
                         * to see if the dquot has been flushed delayed
                         * write.  If so, grab its buffer and send it
                         * out immediately.  We'll be able to acquire
                         * the flush lock when the I/O completes.
                         */
                        xfs_qm_dqflock_pushbuf_wait(dqp);
                }
                /*
                 * Let go of the mplist lock. We don't want to hold it
                 * across a disk write.
                 */
                xfs_qm_mplist_unlock(mp);
                error = xfs_qm_dqflush(dqp, flags);
                xfs_dqunlock(dqp);
                if (error)
                        return error;

                xfs_qm_mplist_lock(mp);
                if (recl != XFS_QI_MPLRECLAIMS(mp)) {
                        xfs_qm_mplist_unlock(mp);
                        /* XXX restart limit */
                        goto again;
                }
        }

        xfs_qm_mplist_unlock(mp);
        /* return ! busy */
        return 0;
}
/*
 * Release the group dquot pointers the user dquots may be
 * carrying around as a hint. mplist is locked on entry and exit.
 */
STATIC void
xfs_qm_detach_gdquots(
        xfs_mount_t     *mp)
{
        xfs_dquot_t     *dqp, *gdqp;
        int             nrecl;

 again:
        ASSERT(XFS_QM_IS_MPLIST_LOCKED(mp));
        dqp = XFS_QI_MPLNEXT(mp);
        while (dqp) {
                xfs_dqlock(dqp);
                if ((gdqp = dqp->q_gdquot)) {
                        xfs_dqlock(gdqp);
                        dqp->q_gdquot = NULL;
                }
                xfs_dqunlock(dqp);

                if (gdqp) {
                        /*
                         * Can't hold the mplist lock across a dqput.
                         * XXXmust convert to marker based iterations here.
                         */
                        nrecl = XFS_QI_MPLRECLAIMS(mp);
                        xfs_qm_mplist_unlock(mp);
                        xfs_qm_dqput(gdqp);

                        xfs_qm_mplist_lock(mp);
                        if (nrecl != XFS_QI_MPLRECLAIMS(mp))
                                goto again;
                }
                dqp = dqp->MPL_NEXT;
        }
}

/*
 * Go through all the incore dquots of this file system and take them
 * off the mplist and hashlist, if the dquot type matches the dqtype
 * parameter. This is used when turning off quota accounting for
 * users and/or groups, as well as when the filesystem is unmounting.
 */
STATIC int
xfs_qm_dqpurge_int(
        xfs_mount_t     *mp,
        uint            flags) /* QUOTAOFF/UMOUNTING/UQUOTA/PQUOTA/GQUOTA */
{
        xfs_dquot_t     *dqp;
        uint            dqtype;
        int             nrecl;
        xfs_dquot_t     *nextdqp;
        int             nmisses;

        if (mp->m_quotainfo == NULL)
                return 0;

        dqtype = (flags & XFS_QMOPT_UQUOTA) ? XFS_DQ_USER : 0;
        dqtype |= (flags & XFS_QMOPT_PQUOTA) ? XFS_DQ_PROJ : 0;
        dqtype |= (flags & XFS_QMOPT_GQUOTA) ? XFS_DQ_GROUP : 0;

        xfs_qm_mplist_lock(mp);

        /*
         * In the first pass through all incore dquots of this filesystem,
         * we release the group dquot pointers the user dquots may be
         * carrying around as a hint. We need to do this irrespective of
         * what's being turned off.
         */
        xfs_qm_detach_gdquots(mp);

      again:
        nmisses = 0;
        ASSERT(XFS_QM_IS_MPLIST_LOCKED(mp));
        /*
         * Try to get rid of all of the unwanted dquots. The idea is to
         * get them off mplist and hashlist, but leave them on freelist.
         */
        dqp = XFS_QI_MPLNEXT(mp);
        while (dqp) {
                /*
                 * It's OK to look at the type without taking dqlock here.
                 * We're holding the mplist lock here, and that's needed for
                 * a dqreclaim.
                 */
                if ((dqp->dq_flags & dqtype) == 0) {
                        dqp = dqp->MPL_NEXT;
                        continue;
                }

                if (!mutex_trylock(&dqp->q_hash->qh_lock)) {
                        nrecl = XFS_QI_MPLRECLAIMS(mp);
                        xfs_qm_mplist_unlock(mp);
                        mutex_lock(&dqp->q_hash->qh_lock);
                        xfs_qm_mplist_lock(mp);

                        /*
                         * XXXTheoretically, we can get into a very long
                         * ping pong game here.
                         * No one can be adding dquots to the mplist at
                         * this point, but somebody might be taking things off.
                         */
                        if (nrecl != XFS_QI_MPLRECLAIMS(mp)) {
                                mutex_unlock(&dqp->q_hash->qh_lock);
                                goto again;
                        }
                }

                /*
                 * Take the dquot off the mplist and hashlist. It may remain on
                 * freelist in INACTIVE state.
                 */
                nextdqp = dqp->MPL_NEXT;
                nmisses += xfs_qm_dqpurge(dqp);
                dqp = nextdqp;
        }
        xfs_qm_mplist_unlock(mp);
        return nmisses;
}

int
xfs_qm_dqpurge_all(
        xfs_mount_t     *mp,
        uint            flags)
{
        int             ndquots;

        /*
         * Purge the dquot cache.
         * None of the dquots should really be busy at this point.
         */
        if (mp->m_quotainfo) {
                while ((ndquots = xfs_qm_dqpurge_int(mp, flags))) {
                        delay(ndquots * 10);
                }
        }
        return 0;
}

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

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

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

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

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

                        xfs_dqunlock(dqp);
                        xfs_dqunlock(udqhint);
                        return 0;
                }

                /*
                 * We can't hold a dquot lock when we call the dqget code.
                 * We'll deadlock in no time, because of (not conforming to)
                 * lock ordering - the inodelock comes before any dquot lock,
                 * and we may drop and reacquire the ilock in xfs_qm_dqget().
                 */
                xfs_dqunlock(udqhint);
        }

        /*
         * Find the dquot from somewhere. This bumps the
         * reference count of dquot and returns it locked.
         * This can return ENOENT if dquot didn't exist on
         * disk and we didn't ask it to allocate;
         * ESRCH if quotas got turned off suddenly.
         */
        error = xfs_qm_dqget(ip->i_mount, ip, id, type, XFS_QMOPT_DOWARN, &dqp);
        if (error)
                return error;

        xfs_dqtrace_entry(dqp, "DQATTACH: found by dqget");

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


/*
 * Given a udquot and gdquot, attach a ptr to the group dquot in the
 * udquot as a hint for future lookups. The idea sounds simple, but the
 * execution isn't, because the udquot might have a group dquot attached
 * already and getting rid of that gets us into lock ordering constraints.
 * The process is complicated more by the fact that the dquots may or may not
 * be locked on entry.
 */
STATIC void
xfs_qm_dqattach_grouphint(
        xfs_dquot_t     *udq,
        xfs_dquot_t     *gdq)
{
        xfs_dquot_t     *tmp;

        xfs_dqlock(udq);

        if ((tmp = udq->q_gdquot)) {
                if (tmp == gdq) {
                        xfs_dqunlock(udq);
                        return;
                }

                udq->q_gdquot = NULL;
                /*
                 * We can't keep any dqlocks when calling dqrele,
                 * because the freelist lock comes before dqlocks.
                 */
                xfs_dqunlock(udq);
                /*
                 * we took a hard reference once upon a time in dqget,
                 * so give it back when the udquot no longer points at it
                 * dqput() does the unlocking of the dquot.
                 */
                xfs_qm_dqrele(tmp);

                xfs_dqlock(udq);
                xfs_dqlock(gdq);

        } else {
                ASSERT(XFS_DQ_IS_LOCKED(udq));
                xfs_dqlock(gdq);
        }

        ASSERT(XFS_DQ_IS_LOCKED(udq));
        ASSERT(XFS_DQ_IS_LOCKED(gdq));
        /*
         * Somebody could have attached a gdquot here,
         * when we dropped the uqlock. If so, just do nothing.
         */
        if (udq->q_gdquot == NULL) {
                XFS_DQHOLD(gdq);
                udq->q_gdquot = gdq;
        }

        xfs_dqunlock(gdq);
        xfs_dqunlock(udq);
}


/*
 * Given a locked inode, attach dquot(s) to it, taking U/G/P-QUOTAON
 * into account.
 * If XFS_QMOPT_DQALLOC, the dquot(s) will be allocated if needed.
 * If XFS_QMOPT_ILOCKED, then inode sent is already locked EXCL.
 * Inode may get unlocked and relocked in here, and the caller must deal with
 * the consequences.
 */
int
xfs_qm_dqattach(
        xfs_inode_t     *ip,
        uint            flags)
{
        xfs_mount_t     *mp = ip->i_mount;
        uint            nquotas = 0;
        int             error = 0;

        if ((! XFS_IS_QUOTA_ON(mp)) ||
            (! XFS_NOT_DQATTACHED(mp, ip)) ||
            (ip->i_ino == mp->m_sb.sb_uquotino) ||
            (ip->i_ino == mp->m_sb.sb_gquotino))
                return 0;

        ASSERT((flags & XFS_QMOPT_ILOCKED) == 0 ||
               xfs_isilocked(ip, XFS_ILOCK_EXCL));

        if (! (flags & XFS_QMOPT_ILOCKED))
                xfs_ilock(ip, XFS_ILOCK_EXCL);

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

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

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

                /*
                 * We may or may not have the i_udquot locked at this point,
                 * but this check is OK since we don't depend on the i_gdquot to
                 * be accurate 100% all the time. It is just a hint, and this
                 * will succeed in general.
                 */
                if (ip->i_udquot->q_gdquot == ip->i_gdquot)
                        goto done;
                /*
                 * Attach i_gdquot to the gdquot hint inside the i_udquot.
                 */
                xfs_qm_dqattach_grouphint(ip->i_udquot, ip->i_gdquot);
        }

      done:

#ifdef QUOTADEBUG
        if (! error) {
                if (XFS_IS_UQUOTA_ON(mp))
                        ASSERT(ip->i_udquot);
                if (XFS_IS_OQUOTA_ON(mp))
                        ASSERT(ip->i_gdquot);
        }
#endif

        if (! (flags & XFS_QMOPT_ILOCKED))
                xfs_iunlock(ip, XFS_ILOCK_EXCL);

#ifdef QUOTADEBUG
        else
                ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
#endif
        return error;
}

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

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

/*
 * This is called to sync quotas. We can be told to use non-blocking
 * semantics by either the SYNC_BDFLUSH flag or the absence of the
 * SYNC_WAIT flag.
 */
int
xfs_qm_sync(
        xfs_mount_t     *mp,
        int             flags)
{
        int             recl, restarts;
        xfs_dquot_t     *dqp;
        uint            flush_flags;
        boolean_t       nowait;
        int             error;

        if (! XFS_IS_QUOTA_ON(mp))
                return 0;

        restarts = 0;
        /*
         * We won't block unless we are asked to.
         */
        nowait = (boolean_t)(flags & SYNC_BDFLUSH || (flags & SYNC_WAIT) == 0);

  again:
        xfs_qm_mplist_lock(mp);
        /*
         * dqpurge_all() also takes the mplist lock and iterate thru all dquots
         * in quotaoff. However, if the QUOTA_ACTIVE bits are not cleared
         * when we have the mplist lock, we know that dquots will be consistent
         * as long as we have it locked.
         */
        if (! XFS_IS_QUOTA_ON(mp)) {
                xfs_qm_mplist_unlock(mp);
                return 0;
        }
        FOREACH_DQUOT_IN_MP(dqp, mp) {
                /*
                 * If this is vfs_sync calling, then skip the dquots that
                 * don't 'seem' to be dirty. ie. don't acquire dqlock.
                 * This is very similar to what xfs_sync does with inodes.
                 */
                if (flags & SYNC_BDFLUSH) {
                        if (! XFS_DQ_IS_DIRTY(dqp))
                                continue;
                }

                if (nowait) {
                        /*
                         * Try to acquire the dquot lock. We are NOT out of
                         * lock order, but we just don't want to wait for this
                         * lock, unless somebody wanted us to.
                         */
                        if (! xfs_qm_dqlock_nowait(dqp))
                                continue;
                } else {
                        xfs_dqlock(dqp);
                }

                /*
                 * Now, find out for sure if this dquot is dirty or not.
                 */
                if (! XFS_DQ_IS_DIRTY(dqp)) {
                        xfs_dqunlock(dqp);
                        continue;
                }

                /* XXX a sentinel would be better */
                recl = XFS_QI_MPLRECLAIMS(mp);
                if (!xfs_dqflock_nowait(dqp)) {
                        if (nowait) {
                                xfs_dqunlock(dqp);
                                continue;
                        }
                        /*
                         * If we can't grab the flush lock then if the caller
                         * really wanted us to give this our best shot, so
                         * see if we can give a push to the buffer before we wait
                         * on the flush lock. At this point, we know that
                         * even though the dquot is being flushed,
                         * it has (new) dirty data.
                         */
                        xfs_qm_dqflock_pushbuf_wait(dqp);
                }
                /*
                 * Let go of the mplist lock. We don't want to hold it
                 * across a disk write
                 */
                flush_flags = (nowait) ? XFS_QMOPT_DELWRI : XFS_QMOPT_SYNC;
                xfs_qm_mplist_unlock(mp);
                xfs_dqtrace_entry(dqp, "XQM_SYNC: DQFLUSH");
                error = xfs_qm_dqflush(dqp, flush_flags);
                xfs_dqunlock(dqp);
                if (error && XFS_FORCED_SHUTDOWN(mp))
                        return 0;       /* Need to prevent umount failure */
                else if (error)
                        return error;

                xfs_qm_mplist_lock(mp);
                if (recl != XFS_QI_MPLRECLAIMS(mp)) {
                        if (++restarts >= XFS_QM_SYNC_MAX_RESTARTS)
                                break;

                        xfs_qm_mplist_unlock(mp);
                        goto again;
                }
        }

        xfs_qm_mplist_unlock(mp);
        return 0;
}

/*
 * The hash chains and the mplist use the same xfs_dqhash structure as
 * their list head, but we can take the mplist qh_lock and one of the
 * hash qh_locks at the same time without any problem as they aren't
 * related.
 */
static struct lock_class_key xfs_quota_mplist_class;

/*
 * This initializes all the quota information that's kept in the
 * mount structure
 */
STATIC int
xfs_qm_init_quotainfo(
        xfs_mount_t     *mp)
{
        xfs_quotainfo_t *qinf;
        int             error;
        xfs_dquot_t     *dqp;

        ASSERT(XFS_IS_QUOTA_RUNNING(mp));

        /*
         * Tell XQM that we exist as soon as possible.
         */
        if ((error = xfs_qm_hold_quotafs_ref(mp))) {
                return error;
        }

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

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

        xfs_qm_list_init(&qinf->qi_dqlist, "mpdqlist", 0);
        lockdep_set_class(&qinf->qi_dqlist.qh_lock, &xfs_quota_mplist_class);

        qinf->qi_dqreclaims = 0;

        /* mutex used to serialize quotaoffs */
        mutex_init(&qinf->qi_quotaofflock);

        /* Precalc some constants */
        qinf->qi_dqchunklen = XFS_FSB_TO_BB(mp, XFS_DQUOT_CLUSTER_SIZE_FSB);
        ASSERT(qinf->qi_dqchunklen);
        qinf->qi_dqperchunk = BBTOB(qinf->qi_dqchunklen);
        do_div(qinf->qi_dqperchunk, sizeof(xfs_dqblk_t));

        mp->m_qflags |= (mp->m_sb.sb_qflags & XFS_ALL_QUOTA_CHKD);

        /*
         * We try to get the limits from the superuser's limits fields.
         * This is quite hacky, but it is standard quota practice.
         * We look at the USR dquot with id == 0 first, but if user quotas
         * are not enabled we goto the GRP dquot with id == 0.
         * We don't really care to keep separate default limits for user
         * and group quotas, at least not at this point.
         */
        error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t)0,
                             XFS_IS_UQUOTA_RUNNING(mp) ? XFS_DQ_USER : 
                             (XFS_IS_GQUOTA_RUNNING(mp) ? XFS_DQ_GROUP :
                                XFS_DQ_PROJ),
                             XFS_QMOPT_DQSUSER|XFS_QMOPT_DOWARN,
                             &dqp);
        if (! error) {
                xfs_disk_dquot_t        *ddqp = &dqp->q_core;

                /*
                 * The warnings and timers set the grace period given to
                 * a user or group before he or she can not perform any
                 * more writing. If it is zero, a default is used.
                 */
                qinf->qi_btimelimit = ddqp->d_btimer ?
                        be32_to_cpu(ddqp->d_btimer) : XFS_QM_BTIMELIMIT;
                qinf->qi_itimelimit = ddqp->d_itimer ?
                        be32_to_cpu(ddqp->d_itimer) : XFS_QM_ITIMELIMIT;
                qinf->qi_rtbtimelimit = ddqp->d_rtbtimer ?
                        be32_to_cpu(ddqp->d_rtbtimer) : XFS_QM_RTBTIMELIMIT;
                qinf->qi_bwarnlimit = ddqp->d_bwarns ?
                        be16_to_cpu(ddqp->d_bwarns) : XFS_QM_BWARNLIMIT;
                qinf->qi_iwarnlimit = ddqp->d_iwarns ?
                        be16_to_cpu(ddqp->d_iwarns) : XFS_QM_IWARNLIMIT;
                qinf->qi_rtbwarnlimit = ddqp->d_rtbwarns ?
                        be16_to_cpu(ddqp->d_rtbwarns) : XFS_QM_RTBWARNLIMIT;
                qinf->qi_bhardlimit = be64_to_cpu(ddqp->d_blk_hardlimit);
                qinf->qi_bsoftlimit = be64_to_cpu(ddqp->d_blk_softlimit);
                qinf->qi_ihardlimit = be64_to_cpu(ddqp->d_ino_hardlimit);
                qinf->qi_isoftlimit = be64_to_cpu(ddqp->d_ino_softlimit);
                qinf->qi_rtbhardlimit = be64_to_cpu(ddqp->d_rtb_hardlimit);
                qinf->qi_rtbsoftlimit = be64_to_cpu(ddqp->d_rtb_softlimit);
 
                /*
                 * We sent the XFS_QMOPT_DQSUSER flag to dqget because
                 * we don't want this dquot cached. We haven't done a
                 * quotacheck yet, and quotacheck doesn't like incore dquots.
                 */
                xfs_qm_dqdestroy(dqp);
        } else {
                qinf->qi_btimelimit = XFS_QM_BTIMELIMIT;
                qinf->qi_itimelimit = XFS_QM_ITIMELIMIT;
                qinf->qi_rtbtimelimit = XFS_QM_RTBTIMELIMIT;
                qinf->qi_bwarnlimit = XFS_QM_BWARNLIMIT;
                qinf->qi_iwarnlimit = XFS_QM_IWARNLIMIT;
                qinf->qi_rtbwarnlimit = XFS_QM_RTBWARNLIMIT;
        }

        return 0;
}


/*
 * Gets called when unmounting a filesystem or when all quotas get
 * turned off.
 * This purges the quota inodes, destroys locks and frees itself.
 */
void
xfs_qm_destroy_quotainfo(
        xfs_mount_t     *mp)
{
        xfs_quotainfo_t *qi;

        qi = mp->m_quotainfo;
        ASSERT(qi != NULL);
        ASSERT(xfs_Gqm != NULL);

        /*
         * Release the reference that XQM kept, so that we know
         * when the XQM structure should be freed. We cannot assume
         * that xfs_Gqm is non-null after this point.
         */
        xfs_qm_rele_quotafs_ref(mp);

        xfs_qm_list_destroy(&qi->qi_dqlist);

        if (qi->qi_uquotaip) {
                IRELE(qi->qi_uquotaip);
                qi->qi_uquotaip = NULL; /* paranoia */
        }
        if (qi->qi_gquotaip) {
                IRELE(qi->qi_gquotaip);
                qi->qi_gquotaip = NULL;
        }
        mutex_destroy(&qi->qi_quotaofflock);
        kmem_free(qi);
        mp->m_quotainfo = NULL;
}



/* ------------------- PRIVATE STATIC FUNCTIONS ----------------------- */

/* ARGSUSED */
STATIC void
xfs_qm_list_init(
        xfs_dqlist_t    *list,
        char            *str,
        int             n)
{
        mutex_init(&list->qh_lock);
        list->qh_next = NULL;
        list->qh_version = 0;
        list->qh_nelems = 0;
}

STATIC void
xfs_qm_list_destroy(
        xfs_dqlist_t    *list)
{
        mutex_destroy(&(list->qh_lock));
}


/*
 * Stripped down version of dqattach. This doesn't attach, or even look at the
 * dquots attached to the inode. The rationale is that there won't be any
 * attached at the time this is called from quotacheck.
 */
STATIC int
xfs_qm_dqget_noattach(
        xfs_inode_t     *ip,
        xfs_dquot_t     **O_udqpp,
        xfs_dquot_t     **O_gdqpp)
{
        int             error;
        xfs_mount_t     *mp;
        xfs_dquot_t     *udqp, *gdqp;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        mp = ip->i_mount;
        udqp = NULL;
        gdqp = NULL;

        if (XFS_IS_UQUOTA_ON(mp)) {
                ASSERT(ip->i_udquot == NULL);
                /*
                 * We want the dquot allocated if it doesn't exist.
                 */
                if ((error = xfs_qm_dqget(mp, ip, ip->i_d.di_uid, XFS_DQ_USER,
                                         XFS_QMOPT_DQALLOC | XFS_QMOPT_DOWARN,
                                         &udqp))) {
                        /*
                         * Shouldn't be able to turn off quotas here.
                         */
                        ASSERT(error != ESRCH);
                        ASSERT(error != ENOENT);
                        return error;
                }
                ASSERT(udqp);
        }

        if (XFS_IS_OQUOTA_ON(mp)) {
                ASSERT(ip->i_gdquot == NULL);
                if (udqp)
                        xfs_dqunlock(udqp);
                error = XFS_IS_GQUOTA_ON(mp) ?
                                xfs_qm_dqget(mp, ip,
                                             ip->i_d.di_gid, XFS_DQ_GROUP,
                                             XFS_QMOPT_DQALLOC|XFS_QMOPT_DOWARN,
                                             &gdqp) :
                                xfs_qm_dqget(mp, ip,
                                             ip->i_d.di_projid, XFS_DQ_PROJ,
                                             XFS_QMOPT_DQALLOC|XFS_QMOPT_DOWARN,
                                             &gdqp);
                if (error) {
                        if (udqp)
                                xfs_qm_dqrele(udqp);
                        ASSERT(error != ESRCH);
                        ASSERT(error != ENOENT);
                        return error;
                }
                ASSERT(gdqp);

                /* Reacquire the locks in the right order */
                if (udqp) {
                        if (! xfs_qm_dqlock_nowait(udqp)) {
                                xfs_dqunlock(gdqp);
                                xfs_dqlock(udqp);
                                xfs_dqlock(gdqp);
                        }
                }
        }

        *O_udqpp = udqp;
        *O_gdqpp = gdqp;

#ifdef QUOTADEBUG
        if (udqp) ASSERT(XFS_DQ_IS_LOCKED(udqp));
        if (gdqp) ASSERT(XFS_DQ_IS_LOCKED(gdqp));
#endif
        return 0;
}

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

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

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

        /*
         * Keep an extra reference to this quota inode. This inode is
         * locked exclusively and joined to the transaction already.
         */
        ASSERT(xfs_isilocked(*ip, XFS_ILOCK_EXCL));
        IHOLD(*ip);

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

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

                /* qflags will get updated _after_ quotacheck */
                mp->m_sb.sb_qflags = 0;
#if defined(DEBUG) && defined(XFS_LOUD_RECOVERY)
                cmn_err(CE_NOTE,
                        "Old superblock version %x, converting to %x.",
                        oldv, mp->m_sb.sb_versionnum);
#endif
        }
        if (flags & XFS_QMOPT_UQUOTA)
                mp->m_sb.sb_uquotino = (*ip)->i_ino;
        else
                mp->m_sb.sb_gquotino = (*ip)->i_ino;
        spin_unlock(&mp->m_sb_lock);
        xfs_mod_sb(tp, sbfields);

        if ((error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES))) {
                xfs_fs_cmn_err(CE_ALERT, mp, "XFS qino_alloc failed!");
                return error;
        }
        return 0;
}


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

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

STATIC int
xfs_qm_dqiter_bufs(
        xfs_mount_t     *mp,
        xfs_dqid_t      firstid,
        xfs_fsblock_t   bno,
        xfs_filblks_t   blkcnt,
        uint            flags)
{
        xfs_buf_t       *bp;
        int             error;
        int             notcommitted;
        int             incr;
        int             type;

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

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

                xfs_qm_reset_dqcounts(mp, bp, firstid, type);
                xfs_bdwrite(mp, bp);
                /*
                 * goto the next block.
                 */
                bno++;
                firstid += XFS_QM_DQPERBLK(mp);
        }
        return error;
}

/*
 * Iterate over all allocated USR/GRP/PRJ dquots in the system, calling a
 * caller supplied function for every chunk of dquots that we find.
 */
STATIC int
xfs_qm_dqiterate(
        xfs_mount_t     *mp,
        xfs_inode_t     *qip,
        uint            flags)
{
        xfs_bmbt_irec_t         *map;
        int                     i, nmaps;       /* number of map entries */
        int                     error;          /* return value */
        xfs_fileoff_t           lblkno;
        xfs_filblks_t           maxlblkcnt;
        xfs_dqid_t              firstid;
        xfs_fsblock_t           rablkno;
        xfs_filblks_t           rablkcnt;

        error = 0;
        /*
         * This looks racy, but we can't keep an inode lock across a
         * trans_reserve. But, this gets called during quotacheck, and that
         * happens only at mount time which is single threaded.
         */
        if (qip->i_d.di_nblocks == 0)
                return 0;

        map = kmem_alloc(XFS_DQITER_MAP_SIZE * sizeof(*map), KM_SLEEP);

        lblkno = 0;
        maxlblkcnt = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_MAXIOFFSET(mp));
        do {
                nmaps = XFS_DQITER_MAP_SIZE;
                /*
                 * We aren't changing the inode itself. Just changing
                 * some of its data. No new blocks are added here, and
                 * the inode is never added to the transaction.
                 */
                xfs_ilock(qip, XFS_ILOCK_SHARED);
                error = xfs_bmapi(NULL, qip, lblkno,
                                  maxlblkcnt - lblkno,
                                  XFS_BMAPI_METADATA,
                                  NULL,
                                  0, map, &nmaps, NULL, NULL);
                xfs_iunlock(qip, XFS_ILOCK_SHARED);
                if (error)
                        break;

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


                        lblkno += map[i].br_blockcount;

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

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

                if (error)
                        break;
        } while (nmaps > 0);

        kmem_free(map);

        return error;
}

/*
 * Called by dqusage_adjust in doing a quotacheck.
 * Given the inode, and a dquot (either USR or GRP, doesn't matter),
 * this updates its incore copy as well as the buffer copy. This is
 * so that once the quotacheck is done, we can just log all the buffers,
 * as opposed to logging numerous updates to individual dquots.
 */
STATIC void
xfs_qm_quotacheck_dqadjust(
        xfs_dquot_t             *dqp,
        xfs_qcnt_t              nblks,
        xfs_qcnt_t              rtblks)
{
        ASSERT(XFS_DQ_IS_LOCKED(dqp));
        xfs_dqtrace_entry(dqp, "QCHECK DQADJUST");
        /*
         * Adjust the inode count and the block count to reflect this inode's
         * resource usage.
         */
        be64_add_cpu(&dqp->q_core.d_icount, 1);
        dqp->q_res_icount++;
        if (nblks) {
                be64_add_cpu(&dqp->q_core.d_bcount, nblks);
                dqp->q_res_bcount += nblks;
        }
        if (rtblks) {
                be64_add_cpu(&dqp->q_core.d_rtbcount, rtblks);
                dqp->q_res_rtbcount += rtblks;
        }

        /*
         * Set default limits, adjust timers (since we changed usages)
         */
        if (! XFS_IS_SUSER_DQUOT(dqp)) {
                xfs_qm_adjust_dqlimits(dqp->q_mount, &dqp->q_core);
                xfs_qm_adjust_dqtimers(dqp->q_mount, &dqp->q_core);
        }

        dqp->dq_flags |= XFS_DQ_DIRTY;
}

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

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

/*
 * callback routine supplied to bulkstat(). Given an inumber, find its
 * dquots and update them to account for resources taken by that inode.
 */
/* ARGSUSED */
STATIC int
xfs_qm_dqusage_adjust(
        xfs_mount_t     *mp,            /* mount point for filesystem */
        xfs_ino_t       ino,            /* inode number to get data for */
        void            __user *buffer, /* not used */
        int             ubsize,         /* not used */
        void            *private_data,  /* not used */
        xfs_daddr_t     bno,            /* starting block of inode cluster */
        int             *ubused,        /* not used */
        void            *dip,           /* on-disk inode pointer (not used) */
        int             *res)           /* result code value */
{
        xfs_inode_t     *ip;
        xfs_dquot_t     *udqp, *gdqp;
        xfs_qcnt_t      nblks, rtblks;
        int             error;

        ASSERT(XFS_IS_QUOTA_RUNNING(mp));

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

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

        /*
         * Obtain the locked dquots. In case of an error (eg. allocation
         * fails for ENOSPC), we return the negative of the error number
         * to bulkstat, so that it can get propagated to quotacheck() and
         * making us disable quotas for the file system.
         */
        if ((error = xfs_qm_dqget_noattach(ip, &udqp, &gdqp))) {
                xfs_iput(ip, XFS_ILOCK_EXCL);
                *res = BULKSTAT_RV_GIVEUP;
                return error;
        }

        rtblks = 0;
        if (! XFS_IS_REALTIME_INODE(ip)) {
                nblks = (xfs_qcnt_t)ip->i_d.di_nblocks;
        } else {
                /*
                 * Walk thru the extent list and count the realtime blocks.
                 */
                if ((error = xfs_qm_get_rtblks(ip, &rtblks))) {
                        xfs_iput(ip, XFS_ILOCK_EXCL);
                        if (udqp)
                                xfs_qm_dqput(udqp);
                        if (gdqp)
                                xfs_qm_dqput(gdqp);
                        *res = BULKSTAT_RV_GIVEUP;
                        return error;
                }
                nblks = (xfs_qcnt_t)ip->i_d.di_nblocks - rtblks;
        }
        ASSERT(ip->i_delayed_blks == 0);

        /*
         * We can't release the inode while holding its dquot locks.
         * The inode can go into inactive and might try to acquire the dquotlocks.
         * So, just unlock here and do a vn_rele at the end.
         */
        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        /*
         * Add the (disk blocks and inode) resources occupied by this
         * inode to its dquots. We do this adjustment in the incore dquot,
         * and also copy the changes to its buffer.
         * We don't care about putting these changes in a transaction
         * envelope because if we crash in the middle of a 'quotacheck'
         * we have to start from the beginning anyway.
         * Once we're done, we'll log all the dquot bufs.
         *
         * The *QUOTA_ON checks below may look pretty racy, but quotachecks
         * and quotaoffs don't race. (Quotachecks happen at mount time only).
         */
        if (XFS_IS_UQUOTA_ON(mp)) {
                ASSERT(udqp);
                xfs_qm_quotacheck_dqadjust(udqp, nblks, rtblks);
                xfs_qm_dqput(udqp);
        }
        if (XFS_IS_OQUOTA_ON(mp)) {
                ASSERT(gdqp);
                xfs_qm_quotacheck_dqadjust(gdqp, nblks, rtblks);
                xfs_qm_dqput(gdqp);
        }
        /*
         * Now release the inode. This will send it to 'inactive', and
         * possibly even free blocks.
         */
        IRELE(ip);

        /*
         * Goto next inode.
         */
        *res = BULKSTAT_RV_DIDONE;
        return 0;
}

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

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

        ASSERT(XFS_QI_UQIP(mp) || XFS_QI_GQIP(mp));
        ASSERT(XFS_IS_QUOTA_RUNNING(mp));

        /*
         * There should be no cached dquots. The (simplistic) quotacheck
         * algorithm doesn't like that.
         */
        ASSERT(XFS_QI_MPLNDQUOTS(mp) == 0);

        cmn_err(CE_NOTE, "XFS quotacheck %s: Please wait.", mp->m_fsname);

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

        if ((gip = XFS_QI_GQIP(mp))) {
                if ((error = xfs_qm_dqiterate(mp, gip, XFS_IS_GQUOTA_ON(mp) ?
                                        XFS_QMOPT_GQUOTA : XFS_QMOPT_PQUOTA)))
                        goto error_return;
                flags |= XFS_OQUOTA_CHKD;
        }

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

        } while (! done);

        /*
         * We've made all the changes that we need to make incore.
         * Flush them down to disk buffers if everything was updated
         * successfully.
         */
        if (!error)
                error = xfs_qm_dqflush_all(mp, XFS_QMOPT_DELWRI);

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

        /*
         * We didn't log anything, because if we crashed, we'll have to
         * start the quotacheck from scratch anyway. However, we must make
         * sure that our dquot changes are secure before we put the
         * quotacheck'd stamp on the superblock. So, here we do a synchronous
         * flush.
         */
        XFS_bflush(mp->m_ddev_targp);

        /*
         * If one type of quotas is off, then it will lose its
         * quotachecked status, since we won't be doing accounting for
         * that type anymore.
         */
        mp->m_qflags &= ~(XFS_OQUOTA_CHKD | XFS_UQUOTA_CHKD);
        mp->m_qflags |= flags;

        XQM_LIST_PRINT(&(XFS_QI_MPL_LIST(mp)), MPL_NEXT, "++++ Mp list +++");

 error_return:
        if (error) {
                cmn_err(CE_WARN, "XFS quotacheck %s: Unsuccessful (Error %d): "
                        "Disabling quotas.",
                        mp->m_fsname, error);
                /*
                 * We must turn off quotas.
                 */
                ASSERT(mp->m_quotainfo != NULL);
                ASSERT(xfs_Gqm != NULL);
                xfs_qm_destroy_quotainfo(mp);
                if (xfs_mount_reset_sbqflags(mp)) {
                        cmn_err(CE_WARN, "XFS quotacheck %s: "
                                "Failed to reset quota flags.", mp->m_fsname);
                }
        } else {
                cmn_err(CE_NOTE, "XFS quotacheck %s: Done.", mp->m_fsname);
        }
        return (error);
}

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

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

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

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

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

                        return XFS_ERROR(error);
                }
        }

        XFS_QI_UQIP(mp) = uip;
        XFS_QI_GQIP(mp) = gip;

        return 0;
}


/*
 * Traverse the freelist of dquots and attempt to reclaim a maximum of
 * 'howmany' dquots. This operation races with dqlookup(), and attempts to
 * favor the lookup function ...
 * XXXsup merge this with qm_reclaim_one().
 */
STATIC int
xfs_qm_shake_freelist(
        int howmany)
{
        int             nreclaimed;
        xfs_dqhash_t    *hash;
        xfs_dquot_t     *dqp, *nextdqp;
        int             restarts;
        int             nflushes;

        if (howmany <= 0)
                return 0;

        nreclaimed = 0;
        restarts = 0;
        nflushes = 0;

#ifdef QUOTADEBUG
        cmn_err(CE_DEBUG, "Shake free 0x%x", howmany);
#endif
        /* lock order is : hashchainlock, freelistlock, mplistlock */
 tryagain:
        xfs_qm_freelist_lock(xfs_Gqm);

        for (dqp = xfs_Gqm->qm_dqfreelist.qh_next;
             ((dqp != (xfs_dquot_t *) &xfs_Gqm->qm_dqfreelist) &&
              nreclaimed < howmany); ) {
                xfs_dqlock(dqp);

                /*
                 * We are racing with dqlookup here. Naturally we don't
                 * want to reclaim a dquot that lookup wants.
                 */
                if (dqp->dq_flags & XFS_DQ_WANT) {
                        xfs_dqunlock(dqp);
                        xfs_qm_freelist_unlock(xfs_Gqm);
                        if (++restarts >= XFS_QM_RECLAIM_MAX_RESTARTS)
                                return nreclaimed;
                        XQM_STATS_INC(xqmstats.xs_qm_dqwants);
                        goto tryagain;
                }

                /*
                 * If the dquot is inactive, we are assured that it is
                 * not on the mplist or the hashlist, and that makes our
                 * life easier.
                 */
                if (dqp->dq_flags & XFS_DQ_INACTIVE) {
                        ASSERT(dqp->q_mount == NULL);
                        ASSERT(! XFS_DQ_IS_DIRTY(dqp));
                        ASSERT(dqp->HL_PREVP == NULL);
                        ASSERT(dqp->MPL_PREVP == NULL);
                        XQM_STATS_INC(xqmstats.xs_qm_dqinact_reclaims);
                        nextdqp = dqp->dq_flnext;
                        goto off_freelist;
                }

                ASSERT(dqp->MPL_PREVP);
                /*
                 * Try to grab the flush lock. If this dquot is in the process of
                 * getting flushed to disk, we don't want to reclaim it.
                 */
                if (!xfs_dqflock_nowait(dqp)) {
                        xfs_dqunlock(dqp);
                        dqp = dqp->dq_flnext;
                        continue;
                }

                /*
                 * We have the flush lock so we know that this is not in the
                 * process of being flushed. So, if this is dirty, flush it
                 * DELWRI so that we don't get a freelist infested with
                 * dirty dquots.
                 */
                if (XFS_DQ_IS_DIRTY(dqp)) {
                        int     error;
                        xfs_dqtrace_entry(dqp, "DQSHAKE: DQDIRTY");
                        /*
                         * We flush it delayed write, so don't bother
                         * releasing the mplock.
                         */
                        error = xfs_qm_dqflush(dqp, XFS_QMOPT_DELWRI);
                        if (error) {
                                xfs_fs_cmn_err(CE_WARN, dqp->q_mount,
                        "xfs_qm_dqflush_all: dquot %p flush failed", dqp);
                        }
                        xfs_dqunlock(dqp); /* dqflush unlocks dqflock */
                        dqp = dqp->dq_flnext;
                        continue;
                }
                /*
                 * We're trying to get the hashlock out of order. This races
                 * with dqlookup; so, we giveup and goto the next dquot if
                 * we couldn't get the hashlock. This way, we won't starve
                 * a dqlookup process that holds the hashlock that is
                 * waiting for the freelist lock.
                 */
                if (!mutex_trylock(&dqp->q_hash->qh_lock)) {
                        xfs_dqfunlock(dqp);
                        xfs_dqunlock(dqp);
                        dqp = dqp->dq_flnext;
                        continue;
                }
                /*
                 * This races with dquot allocation code as well as dqflush_all
                 * and reclaim code. So, if we failed to grab the mplist lock,
                 * giveup everything and start over.
                 */
                hash = dqp->q_hash;
                ASSERT(hash);
                if (! xfs_qm_mplist_nowait(dqp->q_mount)) {
                        /* XXX put a sentinel so that we can come back here */
                        xfs_dqfunlock(dqp);
                        xfs_dqunlock(dqp);
                        mutex_unlock(&hash->qh_lock);
                        xfs_qm_freelist_unlock(xfs_Gqm);
                        if (++restarts >= XFS_QM_RECLAIM_MAX_RESTARTS)
                                return nreclaimed;
                        goto tryagain;
                }
                xfs_dqtrace_entry(dqp, "DQSHAKE: UNLINKING");
#ifdef QUOTADEBUG
                cmn_err(CE_DEBUG, "Shake 0x%p, ID 0x%x\n",
                        dqp, be32_to_cpu(dqp->q_core.d_id));
#endif
                ASSERT(dqp->q_nrefs == 0);
                nextdqp = dqp->dq_flnext;
                XQM_MPLIST_REMOVE(&(XFS_QI_MPL_LIST(dqp->q_mount)), dqp);
                XQM_HASHLIST_REMOVE(hash, dqp);
                xfs_dqfunlock(dqp);
                xfs_qm_mplist_unlock(dqp->q_mount);
                mutex_unlock(&hash->qh_lock);

 off_freelist:
                XQM_FREELIST_REMOVE(dqp);
                xfs_dqunlock(dqp);
                nreclaimed++;
                XQM_STATS_INC(xqmstats.xs_qm_dqshake_reclaims);
                xfs_qm_dqdestroy(dqp);
                dqp = nextdqp;
        }
        xfs_qm_freelist_unlock(xfs_Gqm);
        return nreclaimed;
}


/*
 * The kmem_shake interface is invoked when memory is running low.
 */
/* ARGSUSED */
STATIC int
xfs_qm_shake(int nr_to_scan, gfp_t gfp_mask)
{
        int     ndqused, nfree, n;

        if (!kmem_shake_allow(gfp_mask))
                return 0;
        if (!xfs_Gqm)
                return 0;

        nfree = xfs_Gqm->qm_dqfreelist.qh_nelems; /* free dquots */
        /* incore dquots in all f/s's */
        ndqused = atomic_read(&xfs_Gqm->qm_totaldquots) - nfree;

        ASSERT(ndqused >= 0);

        if (nfree <= ndqused && nfree < ndquot)
                return 0;

        ndqused *= xfs_Gqm->qm_dqfree_ratio;    /* target # of free dquots */
        n = nfree - ndqused - ndquot;           /* # over target */

        return xfs_qm_shake_freelist(MAX(nfree, n));
}


/*
 * Just pop the least recently used dquot off the freelist and
 * recycle it. The returned dquot is locked.
 */
STATIC xfs_dquot_t *
xfs_qm_dqreclaim_one(void)
{
        xfs_dquot_t     *dqpout;
        xfs_dquot_t     *dqp;
        int             restarts;
        int             nflushes;

        restarts = 0;
        dqpout = NULL;
        nflushes = 0;

        /* lockorder: hashchainlock, freelistlock, mplistlock, dqlock, dqflock */
 startagain:
        xfs_qm_freelist_lock(xfs_Gqm);

        FOREACH_DQUOT_IN_FREELIST(dqp, &(xfs_Gqm->qm_dqfreelist)) {
                xfs_dqlock(dqp);

                /*
                 * We are racing with dqlookup here. Naturally we don't
                 * want to reclaim a dquot that lookup wants. We release the
                 * freelist lock and start over, so that lookup will grab
                 * both the dquot and the freelistlock.
                 */
                if (dqp->dq_flags & XFS_DQ_WANT) {
                        ASSERT(! (dqp->dq_flags & XFS_DQ_INACTIVE));
                        xfs_dqtrace_entry(dqp, "DQRECLAIM: DQWANT");
                        xfs_dqunlock(dqp);
                        xfs_qm_freelist_unlock(xfs_Gqm);
                        if (++restarts >= XFS_QM_RECLAIM_MAX_RESTARTS)
                                return NULL;
                        XQM_STATS_INC(xqmstats.xs_qm_dqwants);
                        goto startagain;
                }

                /*
                 * If the dquot is inactive, we are assured that it is
                 * not on the mplist or the hashlist, and that makes our
                 * life easier.
                 */
                if (dqp->dq_flags & XFS_DQ_INACTIVE) {
                        ASSERT(dqp->q_mount == NULL);
                        ASSERT(! XFS_DQ_IS_DIRTY(dqp));
                        ASSERT(dqp->HL_PREVP == NULL);
                        ASSERT(dqp->MPL_PREVP == NULL);
                        XQM_FREELIST_REMOVE(dqp);
                        xfs_dqunlock(dqp);
                        dqpout = dqp;
                        XQM_STATS_INC(xqmstats.xs_qm_dqinact_reclaims);
                        break;
                }

                ASSERT(dqp->q_hash);
                ASSERT(dqp->MPL_PREVP);

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

                /*
                 * We have the flush lock so we know that this is not in the
                 * process of being flushed. So, if this is dirty, flush it
                 * DELWRI so that we don't get a freelist infested with
                 * dirty dquots.
                 */
                if (XFS_DQ_IS_DIRTY(dqp)) {
                        int     error;
                        xfs_dqtrace_entry(dqp, "DQRECLAIM: DQDIRTY");
                        /*
                         * We flush it delayed write, so don't bother
                         * releasing the freelist lock.
                         */
                        error = xfs_qm_dqflush(dqp, XFS_QMOPT_DELWRI);
                        if (error) {
                                xfs_fs_cmn_err(CE_WARN, dqp->q_mount,
                        "xfs_qm_dqreclaim: dquot %p flush failed", dqp);
                        }
                        xfs_dqunlock(dqp); /* dqflush unlocks dqflock */
                        continue;
                }

                if (! xfs_qm_mplist_nowait(dqp->q_mount)) {
                        xfs_dqfunlock(dqp);
                        xfs_dqunlock(dqp);
                        continue;
                }

                if (!mutex_trylock(&dqp->q_hash->qh_lock))
                        goto mplistunlock;

                ASSERT(dqp->q_nrefs == 0);
                xfs_dqtrace_entry(dqp, "DQRECLAIM: UNLINKING");
                XQM_MPLIST_REMOVE(&(XFS_QI_MPL_LIST(dqp->q_mount)), dqp);
                XQM_HASHLIST_REMOVE(dqp->q_hash, dqp);
                XQM_FREELIST_REMOVE(dqp);
                dqpout = dqp;
                mutex_unlock(&dqp->q_hash->qh_lock);
 mplistunlock:
                xfs_qm_mplist_unlock(dqp->q_mount);
                xfs_dqfunlock(dqp);
                xfs_dqunlock(dqp);
                if (dqpout)
                        break;
        }

        xfs_qm_freelist_unlock(xfs_Gqm);
        return dqpout;
}


/*------------------------------------------------------------------*/

/*
 * Return a new incore dquot. Depending on the number of
 * dquots in the system, we either allocate a new one on the kernel heap,
 * or reclaim a free one.
 * Return value is B_TRUE if we allocated a new dquot, B_FALSE if we managed
 * to reclaim an existing one from the freelist.
 */
boolean_t
xfs_qm_dqalloc_incore(
        xfs_dquot_t **O_dqpp)
{
        xfs_dquot_t     *dqp;

        /*
         * Check against high water mark to see if we want to pop
         * a nincompoop dquot off the freelist.
         */
        if (atomic_read(&xfs_Gqm->qm_totaldquots) >= ndquot) {
                /*
                 * Try to recycle a dquot from the freelist.
                 */
                if ((dqp = xfs_qm_dqreclaim_one())) {
                        XQM_STATS_INC(xqmstats.xs_qm_dqreclaims);
                        /*
                         * Just zero the core here. The rest will get
                         * reinitialized by caller. XXX we shouldn't even
                         * do this zero ...
                         */
                        memset(&dqp->q_core, 0, sizeof(dqp->q_core));
                        *O_dqpp = dqp;
                        return B_FALSE;
                }
                XQM_STATS_INC(xqmstats.xs_qm_dqreclaim_misses);
        }

        /*
         * Allocate a brand new dquot on the kernel heap and return it
         * to the caller to initialize.
         */
        ASSERT(xfs_Gqm->qm_dqzone != NULL);
        *O_dqpp = kmem_zone_zalloc(xfs_Gqm->qm_dqzone, KM_SLEEP);
        atomic_inc(&xfs_Gqm->qm_totaldquots);

        return B_TRUE;
}


/*
 * Start a transaction and write the incore superblock changes to
 * disk. flags parameter indicates which fields have changed.
 */
int
xfs_qm_write_sb_changes(
        xfs_mount_t     *mp,
        __int64_t       flags)
{
        xfs_trans_t     *tp;
        int             error;

#ifdef QUOTADEBUG
        cmn_err(CE_NOTE, "Writing superblock quota changes :%s", mp->m_fsname);
#endif
        tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SBCHANGE);
        if ((error = xfs_trans_reserve(tp, 0,
                                      mp->m_sb.sb_sectsize + 128, 0,
                                      0,
                                      XFS_DEFAULT_LOG_COUNT))) {
                xfs_trans_cancel(tp, 0);
                return error;
        }

        xfs_mod_sb(tp, flags);
        error = xfs_trans_commit(tp, 0);

        return error;
}


/* --------------- utility functions for vnodeops ---------------- */


/*
 * Given an inode, a uid and gid (from cred_t) make sure that we have
 * allocated relevant dquot(s) on disk, and that we won't exceed inode
 * quotas by creating this file.
 * This also attaches dquot(s) to the given inode after locking it,
 * and returns the dquots corresponding to the uid and/or gid.
 *
 * in   : inode (unlocked)
 * out  : udquot, gdquot with references taken and unlocked
 */
int
xfs_qm_vop_dqalloc(
        xfs_mount_t     *mp,
        xfs_inode_t     *ip,
        uid_t           uid,
        gid_t           gid,
        prid_t          prid,
        uint            flags,
        xfs_dquot_t     **O_udqpp,
        xfs_dquot_t     **O_gdqpp)
{
        int             error;
        xfs_dquot_t     *uq, *gq;
        uint            lockflags;

        if (!XFS_IS_QUOTA_ON(mp))
                return 0;

        lockflags = XFS_ILOCK_EXCL;
        xfs_ilock(ip, lockflags);

        if ((flags & XFS_QMOPT_INHERIT) && XFS_INHERIT_GID(ip))
                gid = ip->i_d.di_gid;

        /*
         * Attach the dquot(s) to this inode, doing a dquot allocation
         * if necessary. The dquot(s) will not be locked.
         */
        if (XFS_NOT_DQATTACHED(mp, ip)) {
                if ((error = xfs_qm_dqattach(ip, XFS_QMOPT_DQALLOC |
                                            XFS_QMOPT_ILOCKED))) {
                        xfs_iunlock(ip, lockflags);
                        return error;
                }
        }

        uq = gq = NULL;
        if ((flags & XFS_QMOPT_UQUOTA) && XFS_IS_UQUOTA_ON(mp)) {
                if (ip->i_d.di_uid != uid) {
                        /*
                         * What we need is the dquot that has this uid, and
                         * if we send the inode to dqget, the uid of the inode
                         * takes priority over what's sent in the uid argument.
                         * We must unlock inode here before calling dqget if
                         * we're not sending the inode, because otherwise
                         * we'll deadlock by doing trans_reserve while
                         * holding ilock.
                         */
                        xfs_iunlock(ip, lockflags);
                        if ((error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t) uid,
                                                 XFS_DQ_USER,
                                                 XFS_QMOPT_DQALLOC |
                                                 XFS_QMOPT_DOWARN,
                                                 &uq))) {
                                ASSERT(error != ENOENT);
                                return error;
                        }
                        /*
                         * Get the ilock in the right order.
                         */
                        xfs_dqunlock(uq);
                        lockflags = XFS_ILOCK_SHARED;
                        xfs_ilock(ip, lockflags);
                } else {
                        /*
                         * Take an extra reference, because we'll return
                         * this to caller
                         */
                        ASSERT(ip->i_udquot);
                        uq = ip->i_udquot;
                        xfs_dqlock(uq);
                        XFS_DQHOLD(uq);
                        xfs_dqunlock(uq);
                }
        }
        if ((flags & XFS_QMOPT_GQUOTA) && XFS_IS_GQUOTA_ON(mp)) {
                if (ip->i_d.di_gid != gid) {
                        xfs_iunlock(ip, lockflags);
                        if ((error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t)gid,
                                                 XFS_DQ_GROUP,
                                                 XFS_QMOPT_DQALLOC |
                                                 XFS_QMOPT_DOWARN,
                                                 &gq))) {
                                if (uq)
                                        xfs_qm_dqrele(uq);
                                ASSERT(error != ENOENT);
                                return error;
                        }
                        xfs_dqunlock(gq);
                        lockflags = XFS_ILOCK_SHARED;
                        xfs_ilock(ip, lockflags);
                } else {
                        ASSERT(ip->i_gdquot);
                        gq = ip->i_gdquot;
                        xfs_dqlock(gq);
                        XFS_DQHOLD(gq);
                        xfs_dqunlock(gq);
                }
        } else if ((flags & XFS_QMOPT_PQUOTA) && XFS_IS_PQUOTA_ON(mp)) {
                if (ip->i_d.di_projid != prid) {
                        xfs_iunlock(ip, lockflags);
                        if ((error = xfs_qm_dqget(mp, NULL, (xfs_dqid_t)prid,
                                                 XFS_DQ_PROJ,
                                                 XFS_QMOPT_DQALLOC |
                                                 XFS_QMOPT_DOWARN,
                                                 &gq))) {
                                if (uq)
                                        xfs_qm_dqrele(uq);
                                ASSERT(error != ENOENT);
                                return (error);
                        }
                        xfs_dqunlock(gq);
                        lockflags = XFS_ILOCK_SHARED;
                        xfs_ilock(ip, lockflags);
                } else {
                        ASSERT(ip->i_gdquot);
                        gq = ip->i_gdquot;
                        xfs_dqlock(gq);
                        XFS_DQHOLD(gq);
                        xfs_dqunlock(gq);
                }
        }
        if (uq)
                xfs_dqtrace_entry_ino(uq, "DQALLOC", ip);

        xfs_iunlock(ip, lockflags);
        if (O_udqpp)
                *O_udqpp = uq;
        else if (uq)
                xfs_qm_dqrele(uq);
        if (O_gdqpp)
                *O_gdqpp = gq;
        else if (gq)
                xfs_qm_dqrele(gq);
        return 0;
}

/*
 * Actually transfer ownership, and do dquot modifications.
 * These were already reserved.
 */
xfs_dquot_t *
xfs_qm_vop_chown(
        xfs_trans_t     *tp,
        xfs_inode_t     *ip,
        xfs_dquot_t     **IO_olddq,
        xfs_dquot_t     *newdq)
{
        xfs_dquot_t     *prevdq;
        uint            bfield = XFS_IS_REALTIME_INODE(ip) ?
                                 XFS_TRANS_DQ_RTBCOUNT : XFS_TRANS_DQ_BCOUNT;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(XFS_IS_QUOTA_RUNNING(ip->i_mount));

        /* old dquot */
        prevdq = *IO_olddq;
        ASSERT(prevdq);
        ASSERT(prevdq != newdq);

        xfs_trans_mod_dquot(tp, prevdq, bfield, -(ip->i_d.di_nblocks));
        xfs_trans_mod_dquot(tp, prevdq, XFS_TRANS_DQ_ICOUNT, -1);

        /* the sparkling new dquot */
        xfs_trans_mod_dquot(tp, newdq, bfield, ip->i_d.di_nblocks);
        xfs_trans_mod_dquot(tp, newdq, XFS_TRANS_DQ_ICOUNT, 1);

        /*
         * Take an extra reference, because the inode
         * is going to keep this dquot pointer even
         * after the trans_commit.
         */
        xfs_dqlock(newdq);
        XFS_DQHOLD(newdq);
        xfs_dqunlock(newdq);
        *IO_olddq = newdq;

        return prevdq;
}

/*
 * Quota reservations for setattr(AT_UID|AT_GID|AT_PROJID).
 */
int
xfs_qm_vop_chown_reserve(
        xfs_trans_t     *tp,
        xfs_inode_t     *ip,
        xfs_dquot_t     *udqp,
        xfs_dquot_t     *gdqp,
        uint            flags)
{
        int             error;
        xfs_mount_t     *mp;
        uint            delblks, blkflags, prjflags = 0;
        xfs_dquot_t     *unresudq, *unresgdq, *delblksudq, *delblksgdq;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
        mp = ip->i_mount;
        ASSERT(XFS_IS_QUOTA_RUNNING(mp));

        delblks = ip->i_delayed_blks;
        delblksudq = delblksgdq = unresudq = unresgdq = NULL;
        blkflags = XFS_IS_REALTIME_INODE(ip) ?
                        XFS_QMOPT_RES_RTBLKS : XFS_QMOPT_RES_REGBLKS;

        if (XFS_IS_UQUOTA_ON(mp) && udqp &&
            ip->i_d.di_uid != (uid_t)be32_to_cpu(udqp->q_core.d_id)) {
                delblksudq = udqp;
                /*
                 * If there are delayed allocation blocks, then we have to
                 * unreserve those from the old dquot, and add them to the
                 * new dquot.
                 */
                if (delblks) {
                        ASSERT(ip->i_udquot);
                        unresudq = ip->i_udquot;
                }
        }
        if (XFS_IS_OQUOTA_ON(ip->i_mount) && gdqp) {
                if (XFS_IS_PQUOTA_ON(ip->i_mount) &&
                     ip->i_d.di_projid != be32_to_cpu(gdqp->q_core.d_id))
                        prjflags = XFS_QMOPT_ENOSPC;

                if (prjflags ||
                    (XFS_IS_GQUOTA_ON(ip->i_mount) &&
                     ip->i_d.di_gid != be32_to_cpu(gdqp->q_core.d_id))) {
                        delblksgdq = gdqp;
                        if (delblks) {
                                ASSERT(ip->i_gdquot);
                                unresgdq = ip->i_gdquot;
                        }
                }
        }

        if ((error = xfs_trans_reserve_quota_bydquots(tp, ip->i_mount,
                                delblksudq, delblksgdq, ip->i_d.di_nblocks, 1,
                                flags | blkflags | prjflags)))
                return (error);

        /*
         * Do the delayed blks reservations/unreservations now. Since, these
         * are done without the help of a transaction, if a reservation fails
         * its previous reservations won't be automatically undone by trans
         * code. So, we have to do it manually here.
         */
        if (delblks) {
                /*
                 * Do the reservations first. Unreservation can't fail.
                 */
                ASSERT(delblksudq || delblksgdq);
                ASSERT(unresudq || unresgdq);
                if ((error = xfs_trans_reserve_quota_bydquots(NULL, ip->i_mount,
                                delblksudq, delblksgdq, (xfs_qcnt_t)delblks, 0,
                                flags | blkflags | prjflags)))
                        return (error);
                xfs_trans_reserve_quota_bydquots(NULL, ip->i_mount,
                                unresudq, unresgdq, -((xfs_qcnt_t)delblks), 0,
                                blkflags);
        }

        return (0);
}

int
xfs_qm_vop_rename_dqattach(
        xfs_inode_t     **i_tab)
{
        xfs_inode_t     *ip;
        int             i;
        int             error;

        ip = i_tab[0];

        if (! XFS_IS_QUOTA_ON(ip->i_mount))
                return 0;

        if (XFS_NOT_DQATTACHED(ip->i_mount, ip)) {
                error = xfs_qm_dqattach(ip, 0);
                if (error)
                        return error;
        }
        for (i = 1; (i < 4 && i_tab[i]); i++) {
                /*
                 * Watch out for duplicate entries in the table.
                 */
                if ((ip = i_tab[i]) != i_tab[i-1]) {
                        if (XFS_NOT_DQATTACHED(ip->i_mount, ip)) {
                                error = xfs_qm_dqattach(ip, 0);
                                if (error)
                                        return error;
                        }
                }
        }
        return 0;
}

void
xfs_qm_vop_dqattach_and_dqmod_newinode(
        xfs_trans_t     *tp,
        xfs_inode_t     *ip,
        xfs_dquot_t     *udqp,
        xfs_dquot_t     *gdqp)
{
        if (!XFS_IS_QUOTA_ON(tp->t_mountp))
                return;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(XFS_IS_QUOTA_RUNNING(tp->t_mountp));

        if (udqp) {
                xfs_dqlock(udqp);
                XFS_DQHOLD(udqp);
                xfs_dqunlock(udqp);
                ASSERT(ip->i_udquot == NULL);
                ip->i_udquot = udqp;
                ASSERT(XFS_IS_UQUOTA_ON(tp->t_mountp));
                ASSERT(ip->i_d.di_uid == be32_to_cpu(udqp->q_core.d_id));
                xfs_trans_mod_dquot(tp, udqp, XFS_TRANS_DQ_ICOUNT, 1);
        }
        if (gdqp) {
                xfs_dqlock(gdqp);
                XFS_DQHOLD(gdqp);
                xfs_dqunlock(gdqp);
                ASSERT(ip->i_gdquot == NULL);
                ip->i_gdquot = gdqp;
                ASSERT(XFS_IS_OQUOTA_ON(tp->t_mountp));
                ASSERT((XFS_IS_GQUOTA_ON(tp->t_mountp) ?
                        ip->i_d.di_gid : ip->i_d.di_projid) ==
                                be32_to_cpu(gdqp->q_core.d_id));
                xfs_trans_mod_dquot(tp, gdqp, XFS_TRANS_DQ_ICOUNT, 1);
        }
}

/* ------------- list stuff -----------------*/
STATIC void
xfs_qm_freelist_init(xfs_frlist_t *ql)
{
        ql->qh_next = ql->qh_prev = (xfs_dquot_t *) ql;
        mutex_init(&ql->qh_lock);
        ql->qh_version = 0;
        ql->qh_nelems = 0;
}

STATIC void
xfs_qm_freelist_destroy(xfs_frlist_t *ql)
{
        xfs_dquot_t     *dqp, *nextdqp;

        mutex_lock(&ql->qh_lock);
        for (dqp = ql->qh_next;
             dqp != (xfs_dquot_t *)ql; ) {
                xfs_dqlock(dqp);
                nextdqp = dqp->dq_flnext;
#ifdef QUOTADEBUG
                cmn_err(CE_DEBUG, "FREELIST destroy 0x%p", dqp);
#endif
                XQM_FREELIST_REMOVE(dqp);
                xfs_dqunlock(dqp);
                xfs_qm_dqdestroy(dqp);
                dqp = nextdqp;
        }
        mutex_unlock(&ql->qh_lock);
        mutex_destroy(&ql->qh_lock);

        ASSERT(ql->qh_nelems == 0);
}

STATIC void
xfs_qm_freelist_insert(xfs_frlist_t *ql, xfs_dquot_t *dq)
{
        dq->dq_flnext = ql->qh_next;
        dq->dq_flprev = (xfs_dquot_t *)ql;
        ql->qh_next = dq;
        dq->dq_flnext->dq_flprev = dq;
        xfs_Gqm->qm_dqfreelist.qh_nelems++;
        xfs_Gqm->qm_dqfreelist.qh_version++;
}

void
xfs_qm_freelist_unlink(xfs_dquot_t *dq)
{
        xfs_dquot_t *next = dq->dq_flnext;
        xfs_dquot_t *prev = dq->dq_flprev;

        next->dq_flprev = prev;
        prev->dq_flnext = next;
        dq->dq_flnext = dq->dq_flprev = dq;
        xfs_Gqm->qm_dqfreelist.qh_nelems--;
        xfs_Gqm->qm_dqfreelist.qh_version++;
}

void
xfs_qm_freelist_append(xfs_frlist_t *ql, xfs_dquot_t *dq)
{
        xfs_qm_freelist_insert((xfs_frlist_t *)ql->qh_prev, dq);
}