Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1395 insertions, 0 deletions

diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
new file mode 100644
index 000000000..8fb90da89
--- /dev/null
+++ b/fs/xfs/xfs_dquot.c
@@ -0,0 +1,1395 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2000-2003 Silicon Graphics, Inc.
+ * All Rights Reserved.
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_format.h"
+#include "xfs_log_format.h"
+#include "xfs_shared.h"
+#include "xfs_trans_resv.h"
+#include "xfs_bit.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_inode.h"
+#include "xfs_bmap.h"
+#include "xfs_quota.h"
+#include "xfs_trans.h"
+#include "xfs_buf_item.h"
+#include "xfs_trans_space.h"
+#include "xfs_trans_priv.h"
+#include "xfs_qm.h"
+#include "xfs_trace.h"
+#include "xfs_log.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_error.h"
+
+/*
+ * Lock order:
+ *
+ * ip->i_lock
+ *   qi->qi_tree_lock
+ *     dquot->q_qlock (xfs_dqlock() and friends)
+ *       dquot->q_flush (xfs_dqflock() and friends)
+ *       qi->qi_lru_lock
+ *
+ * If two dquots need to be locked the order is user before group/project,
+ * otherwise by the lowest id first, see xfs_dqlock2.
+ */
+
+struct kmem_cache		*xfs_dqtrx_cache;
+static struct kmem_cache	*xfs_dquot_cache;
+
+static struct lock_class_key xfs_dquot_group_class;
+static struct lock_class_key xfs_dquot_project_class;
+
+/*
+ * This is called to free all the memory associated with a dquot
+ */
+void
+xfs_qm_dqdestroy(
+	struct xfs_dquot	*dqp)
+{
+	ASSERT(list_empty(&dqp->q_lru));
+
+	kmem_free(dqp->q_logitem.qli_item.li_lv_shadow);
+	mutex_destroy(&dqp->q_qlock);
+
+	XFS_STATS_DEC(dqp->q_mount, xs_qm_dquot);
+	kmem_cache_free(xfs_dquot_cache, dqp);
+}
+
+/*
+ * If default limits are in force, push them into the dquot now.
+ * We overwrite the dquot limits only if they are zero and this
+ * is not the root dquot.
+ */
+void
+xfs_qm_adjust_dqlimits(
+	struct xfs_dquot	*dq)
+{
+	struct xfs_mount	*mp = dq->q_mount;
+	struct xfs_quotainfo	*q = mp->m_quotainfo;
+	struct xfs_def_quota	*defq;
+	int			prealloc = 0;
+
+	ASSERT(dq->q_id);
+	defq = xfs_get_defquota(q, xfs_dquot_type(dq));
+
+	if (!dq->q_blk.softlimit) {
+		dq->q_blk.softlimit = defq->blk.soft;
+		prealloc = 1;
+	}
+	if (!dq->q_blk.hardlimit) {
+		dq->q_blk.hardlimit = defq->blk.hard;
+		prealloc = 1;
+	}
+	if (!dq->q_ino.softlimit)
+		dq->q_ino.softlimit = defq->ino.soft;
+	if (!dq->q_ino.hardlimit)
+		dq->q_ino.hardlimit = defq->ino.hard;
+	if (!dq->q_rtb.softlimit)
+		dq->q_rtb.softlimit = defq->rtb.soft;
+	if (!dq->q_rtb.hardlimit)
+		dq->q_rtb.hardlimit = defq->rtb.hard;
+
+	if (prealloc)
+		xfs_dquot_set_prealloc_limits(dq);
+}
+
+/* Set the expiration time of a quota's grace period. */
+time64_t
+xfs_dquot_set_timeout(
+	struct xfs_mount	*mp,
+	time64_t		timeout)
+{
+	struct xfs_quotainfo	*qi = mp->m_quotainfo;
+
+	return clamp_t(time64_t, timeout, qi->qi_expiry_min,
+					  qi->qi_expiry_max);
+}
+
+/* Set the length of the default grace period. */
+time64_t
+xfs_dquot_set_grace_period(
+	time64_t		grace)
+{
+	return clamp_t(time64_t, grace, XFS_DQ_GRACE_MIN, XFS_DQ_GRACE_MAX);
+}
+
+/*
+ * Determine if this quota counter is over either limit and set the quota
+ * timers as appropriate.
+ */
+static inline void
+xfs_qm_adjust_res_timer(
+	struct xfs_mount	*mp,
+	struct xfs_dquot_res	*res,
+	struct xfs_quota_limits	*qlim)
+{
+	ASSERT(res->hardlimit == 0 || res->softlimit <= res->hardlimit);
+
+	if ((res->softlimit && res->count > res->softlimit) ||
+	    (res->hardlimit && res->count > res->hardlimit)) {
+		if (res->timer == 0)
+			res->timer = xfs_dquot_set_timeout(mp,
+					ktime_get_real_seconds() + qlim->time);
+	} else {
+		res->timer = 0;
+	}
+}
+
+/*
+ * Check the limits and timers of a dquot and start or reset timers
+ * if necessary.
+ * This gets called even when quota enforcement is OFF, which makes our
+ * life a little less complicated. (We just don't reject any quota
+ * reservations in that case, when enforcement is off).
+ * We also return 0 as the values of the timers in Q_GETQUOTA calls, when
+ * enforcement's off.
+ * In contrast, warnings are a little different in that they don't
+ * 'automatically' get started when limits get exceeded.  They do
+ * get reset to zero, however, when we find the count to be under
+ * the soft limit (they are only ever set non-zero via userspace).
+ */
+void
+xfs_qm_adjust_dqtimers(
+	struct xfs_dquot	*dq)
+{
+	struct xfs_mount	*mp = dq->q_mount;
+	struct xfs_quotainfo	*qi = mp->m_quotainfo;
+	struct xfs_def_quota	*defq;
+
+	ASSERT(dq->q_id);
+	defq = xfs_get_defquota(qi, xfs_dquot_type(dq));
+
+	xfs_qm_adjust_res_timer(dq->q_mount, &dq->q_blk, &defq->blk);
+	xfs_qm_adjust_res_timer(dq->q_mount, &dq->q_ino, &defq->ino);
+	xfs_qm_adjust_res_timer(dq->q_mount, &dq->q_rtb, &defq->rtb);
+}
+
+/*
+ * initialize a buffer full of dquots and log the whole thing
+ */
+STATIC void
+xfs_qm_init_dquot_blk(
+	struct xfs_trans	*tp,
+	struct xfs_mount	*mp,
+	xfs_dqid_t		id,
+	xfs_dqtype_t		type,
+	struct xfs_buf		*bp)
+{
+	struct xfs_quotainfo	*q = mp->m_quotainfo;
+	struct xfs_dqblk	*d;
+	xfs_dqid_t		curid;
+	unsigned int		qflag;
+	unsigned int		blftype;
+	int			i;
+
+	ASSERT(tp);
+	ASSERT(xfs_buf_islocked(bp));
+
+	switch (type) {
+	case XFS_DQTYPE_USER:
+		qflag = XFS_UQUOTA_CHKD;
+		blftype = XFS_BLF_UDQUOT_BUF;
+		break;
+	case XFS_DQTYPE_PROJ:
+		qflag = XFS_PQUOTA_CHKD;
+		blftype = XFS_BLF_PDQUOT_BUF;
+		break;
+	case XFS_DQTYPE_GROUP:
+		qflag = XFS_GQUOTA_CHKD;
+		blftype = XFS_BLF_GDQUOT_BUF;
+		break;
+	default:
+		ASSERT(0);
+		return;
+	}
+
+	d = bp->b_addr;
+
+	/*
+	 * ID of the first dquot in the block - id's are zero based.
+	 */
+	curid = id - (id % q->qi_dqperchunk);
+	memset(d, 0, BBTOB(q->qi_dqchunklen));
+	for (i = 0; i < q->qi_dqperchunk; i++, d++, curid++) {
+		d->dd_diskdq.d_magic = cpu_to_be16(XFS_DQUOT_MAGIC);
+		d->dd_diskdq.d_version = XFS_DQUOT_VERSION;
+		d->dd_diskdq.d_id = cpu_to_be32(curid);
+		d->dd_diskdq.d_type = type;
+		if (curid > 0 && xfs_has_bigtime(mp))
+			d->dd_diskdq.d_type |= XFS_DQTYPE_BIGTIME;
+		if (xfs_has_crc(mp)) {
+			uuid_copy(&d->dd_uuid, &mp->m_sb.sb_meta_uuid);
+			xfs_update_cksum((char *)d, sizeof(struct xfs_dqblk),
+					 XFS_DQUOT_CRC_OFF);
+		}
+	}
+
+	xfs_trans_dquot_buf(tp, bp, blftype);
+
+	/*
+	 * quotacheck uses delayed writes to update all the dquots on disk in an
+	 * efficient manner instead of logging the individual dquot changes as
+	 * they are made. However if we log the buffer allocated here and crash
+	 * after quotacheck while the logged initialisation is still in the
+	 * active region of the log, log recovery can replay the dquot buffer
+	 * initialisation over the top of the checked dquots and corrupt quota
+	 * accounting.
+	 *
+	 * To avoid this problem, quotacheck cannot log the initialised buffer.
+	 * We must still dirty the buffer and write it back before the
+	 * allocation transaction clears the log. Therefore, mark the buffer as
+	 * ordered instead of logging it directly. This is safe for quotacheck
+	 * because it detects and repairs allocated but initialized dquot blocks
+	 * in the quota inodes.
+	 */
+	if (!(mp->m_qflags & qflag))
+		xfs_trans_ordered_buf(tp, bp);
+	else
+		xfs_trans_log_buf(tp, bp, 0, BBTOB(q->qi_dqchunklen) - 1);
+}
+
+/*
+ * Initialize the dynamic speculative preallocation thresholds. The lo/hi
+ * watermarks correspond to the soft and hard limits by default. If a soft limit
+ * is not specified, we use 95% of the hard limit.
+ */
+void
+xfs_dquot_set_prealloc_limits(struct xfs_dquot *dqp)
+{
+	uint64_t space;
+
+	dqp->q_prealloc_hi_wmark = dqp->q_blk.hardlimit;
+	dqp->q_prealloc_lo_wmark = dqp->q_blk.softlimit;
+	if (!dqp->q_prealloc_lo_wmark) {
+		dqp->q_prealloc_lo_wmark = dqp->q_prealloc_hi_wmark;
+		do_div(dqp->q_prealloc_lo_wmark, 100);
+		dqp->q_prealloc_lo_wmark *= 95;
+	}
+
+	space = dqp->q_prealloc_hi_wmark;
+
+	do_div(space, 100);
+	dqp->q_low_space[XFS_QLOWSP_1_PCNT] = space;
+	dqp->q_low_space[XFS_QLOWSP_3_PCNT] = space * 3;
+	dqp->q_low_space[XFS_QLOWSP_5_PCNT] = space * 5;
+}
+
+/*
+ * Ensure that the given in-core dquot has a buffer on disk backing it, and
+ * return the buffer locked and held. This is called when the bmapi finds a
+ * hole.
+ */
+STATIC int
+xfs_dquot_disk_alloc(
+	struct xfs_dquot	*dqp,
+	struct xfs_buf		**bpp)
+{
+	struct xfs_bmbt_irec	map;
+	struct xfs_trans	*tp;
+	struct xfs_mount	*mp = dqp->q_mount;
+	struct xfs_buf		*bp;
+	xfs_dqtype_t		qtype = xfs_dquot_type(dqp);
+	struct xfs_inode	*quotip = xfs_quota_inode(mp, qtype);
+	int			nmaps = 1;
+	int			error;
+
+	trace_xfs_dqalloc(dqp);
+
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_qm_dqalloc,
+			XFS_QM_DQALLOC_SPACE_RES(mp), 0, 0, &tp);
+	if (error)
+		return error;
+
+	xfs_ilock(quotip, XFS_ILOCK_EXCL);
+	xfs_trans_ijoin(tp, quotip, 0);
+
+	if (!xfs_this_quota_on(dqp->q_mount, qtype)) {
+		/*
+		 * Return if this type of quotas is turned off while we didn't
+		 * have an inode lock
+		 */
+		error = -ESRCH;
+		goto err_cancel;
+	}
+
+	error = xfs_iext_count_may_overflow(quotip, XFS_DATA_FORK,
+			XFS_IEXT_ADD_NOSPLIT_CNT);
+	if (error == -EFBIG)
+		error = xfs_iext_count_upgrade(tp, quotip,
+				XFS_IEXT_ADD_NOSPLIT_CNT);
+	if (error)
+		goto err_cancel;
+
+	/* Create the block mapping. */
+	error = xfs_bmapi_write(tp, quotip, dqp->q_fileoffset,
+			XFS_DQUOT_CLUSTER_SIZE_FSB, XFS_BMAPI_METADATA, 0, &map,
+			&nmaps);
+	if (error)
+		goto err_cancel;
+
+	ASSERT(map.br_blockcount == XFS_DQUOT_CLUSTER_SIZE_FSB);
+	ASSERT(nmaps == 1);
+	ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
+	       (map.br_startblock != HOLESTARTBLOCK));
+
+	/*
+	 * Keep track of the blkno to save a lookup later
+	 */
+	dqp->q_blkno = XFS_FSB_TO_DADDR(mp, map.br_startblock);
+
+	/* now we can just get the buffer (there's nothing to read yet) */
+	error = xfs_trans_get_buf(tp, mp->m_ddev_targp, dqp->q_blkno,
+			mp->m_quotainfo->qi_dqchunklen, 0, &bp);
+	if (error)
+		goto err_cancel;
+	bp->b_ops = &xfs_dquot_buf_ops;
+
+	/*
+	 * Make a chunk of dquots out of this buffer and log
+	 * the entire thing.
+	 */
+	xfs_qm_init_dquot_blk(tp, mp, dqp->q_id, qtype, bp);
+	xfs_buf_set_ref(bp, XFS_DQUOT_REF);
+
+	/*
+	 * Hold the buffer and join it to the dfops so that we'll still own
+	 * the buffer when we return to the caller.  The buffer disposal on
+	 * error must be paid attention to very carefully, as it has been
+	 * broken since commit efa092f3d4c6 "[XFS] Fixes a bug in the quota
+	 * code when allocating a new dquot record" in 2005, and the later
+	 * conversion to xfs_defer_ops in commit 310a75a3c6c747 failed to keep
+	 * the buffer locked across the _defer_finish call.  We can now do
+	 * this correctly with xfs_defer_bjoin.
+	 *
+	 * Above, we allocated a disk block for the dquot information and used
+	 * get_buf to initialize the dquot. If the _defer_finish fails, the old
+	 * transaction is gone but the new buffer is not joined or held to any
+	 * transaction, so we must _buf_relse it.
+	 *
+	 * If everything succeeds, the caller of this function is returned a
+	 * buffer that is locked and held to the transaction.  The caller
+	 * is responsible for unlocking any buffer passed back, either
+	 * manually or by committing the transaction.  On error, the buffer is
+	 * released and not passed back.
+	 *
+	 * Keep the quota inode ILOCKed until after the transaction commit to
+	 * maintain the atomicity of bmap/rmap updates.
+	 */
+	xfs_trans_bhold(tp, bp);
+	error = xfs_trans_commit(tp);
+	xfs_iunlock(quotip, XFS_ILOCK_EXCL);
+	if (error) {
+		xfs_buf_relse(bp);
+		return error;
+	}
+
+	*bpp = bp;
+	return 0;
+
+err_cancel:
+	xfs_trans_cancel(tp);
+	xfs_iunlock(quotip, XFS_ILOCK_EXCL);
+	return error;
+}
+
+/*
+ * Read in the in-core dquot's on-disk metadata and return the buffer.
+ * Returns ENOENT to signal a hole.
+ */
+STATIC int
+xfs_dquot_disk_read(
+	struct xfs_mount	*mp,
+	struct xfs_dquot	*dqp,
+	struct xfs_buf		**bpp)
+{
+	struct xfs_bmbt_irec	map;
+	struct xfs_buf		*bp;
+	xfs_dqtype_t		qtype = xfs_dquot_type(dqp);
+	struct xfs_inode	*quotip = xfs_quota_inode(mp, qtype);
+	uint			lock_mode;
+	int			nmaps = 1;
+	int			error;
+
+	lock_mode = xfs_ilock_data_map_shared(quotip);
+	if (!xfs_this_quota_on(mp, qtype)) {
+		/*
+		 * Return if this type of quotas is turned off while we
+		 * didn't have the quota inode lock.
+		 */
+		xfs_iunlock(quotip, lock_mode);
+		return -ESRCH;
+	}
+
+	/*
+	 * Find the block map; no allocations yet
+	 */
+	error = xfs_bmapi_read(quotip, dqp->q_fileoffset,
+			XFS_DQUOT_CLUSTER_SIZE_FSB, &map, &nmaps, 0);
+	xfs_iunlock(quotip, lock_mode);
+	if (error)
+		return error;
+
+	ASSERT(nmaps == 1);
+	ASSERT(map.br_blockcount >= 1);
+	ASSERT(map.br_startblock != DELAYSTARTBLOCK);
+	if (map.br_startblock == HOLESTARTBLOCK)
+		return -ENOENT;
+
+	trace_xfs_dqtobp_read(dqp);
+
+	/*
+	 * store the blkno etc so that we don't have to do the
+	 * mapping all the time
+	 */
+	dqp->q_blkno = XFS_FSB_TO_DADDR(mp, map.br_startblock);
+
+	error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp, dqp->q_blkno,
+			mp->m_quotainfo->qi_dqchunklen, 0, &bp,
+			&xfs_dquot_buf_ops);
+	if (error) {
+		ASSERT(bp == NULL);
+		return error;
+	}
+
+	ASSERT(xfs_buf_islocked(bp));
+	xfs_buf_set_ref(bp, XFS_DQUOT_REF);
+	*bpp = bp;
+
+	return 0;
+}
+
+/* Allocate and initialize everything we need for an incore dquot. */
+STATIC struct xfs_dquot *
+xfs_dquot_alloc(
+	struct xfs_mount	*mp,
+	xfs_dqid_t		id,
+	xfs_dqtype_t		type)
+{
+	struct xfs_dquot	*dqp;
+
+	dqp = kmem_cache_zalloc(xfs_dquot_cache, GFP_KERNEL | __GFP_NOFAIL);
+
+	dqp->q_type = type;
+	dqp->q_id = id;
+	dqp->q_mount = mp;
+	INIT_LIST_HEAD(&dqp->q_lru);
+	mutex_init(&dqp->q_qlock);
+	init_waitqueue_head(&dqp->q_pinwait);
+	dqp->q_fileoffset = (xfs_fileoff_t)id / mp->m_quotainfo->qi_dqperchunk;
+	/*
+	 * Offset of dquot in the (fixed sized) dquot chunk.
+	 */
+	dqp->q_bufoffset = (id % mp->m_quotainfo->qi_dqperchunk) *
+			sizeof(struct xfs_dqblk);
+
+	/*
+	 * Because we want to use a counting completion, complete
+	 * the flush completion once to allow a single access to
+	 * the flush completion without blocking.
+	 */
+	init_completion(&dqp->q_flush);
+	complete(&dqp->q_flush);
+
+	/*
+	 * Make sure group quotas have a different lock class than user
+	 * quotas.
+	 */
+	switch (type) {
+	case XFS_DQTYPE_USER:
+		/* uses the default lock class */
+		break;
+	case XFS_DQTYPE_GROUP:
+		lockdep_set_class(&dqp->q_qlock, &xfs_dquot_group_class);
+		break;
+	case XFS_DQTYPE_PROJ:
+		lockdep_set_class(&dqp->q_qlock, &xfs_dquot_project_class);
+		break;
+	default:
+		ASSERT(0);
+		break;
+	}
+
+	xfs_qm_dquot_logitem_init(dqp);
+
+	XFS_STATS_INC(mp, xs_qm_dquot);
+	return dqp;
+}
+
+/* Check the ondisk dquot's id and type match what the incore dquot expects. */
+static bool
+xfs_dquot_check_type(
+	struct xfs_dquot	*dqp,
+	struct xfs_disk_dquot	*ddqp)
+{
+	uint8_t			ddqp_type;
+	uint8_t			dqp_type;
+
+	ddqp_type = ddqp->d_type & XFS_DQTYPE_REC_MASK;
+	dqp_type = xfs_dquot_type(dqp);
+
+	if (be32_to_cpu(ddqp->d_id) != dqp->q_id)
+		return false;
+
+	/*
+	 * V5 filesystems always expect an exact type match.  V4 filesystems
+	 * expect an exact match for user dquots and for non-root group and
+	 * project dquots.
+	 */
+	if (xfs_has_crc(dqp->q_mount) ||
+	    dqp_type == XFS_DQTYPE_USER || dqp->q_id != 0)
+		return ddqp_type == dqp_type;
+
+	/*
+	 * V4 filesystems support either group or project quotas, but not both
+	 * at the same time.  The non-user quota file can be switched between
+	 * group and project quota uses depending on the mount options, which
+	 * means that we can encounter the other type when we try to load quota
+	 * defaults.  Quotacheck will soon reset the entire quota file
+	 * (including the root dquot) anyway, but don't log scary corruption
+	 * reports to dmesg.
+	 */
+	return ddqp_type == XFS_DQTYPE_GROUP || ddqp_type == XFS_DQTYPE_PROJ;
+}
+
+/* Copy the in-core quota fields in from the on-disk buffer. */
+STATIC int
+xfs_dquot_from_disk(
+	struct xfs_dquot	*dqp,
+	struct xfs_buf		*bp)
+{
+	struct xfs_disk_dquot	*ddqp = bp->b_addr + dqp->q_bufoffset;
+
+	/*
+	 * Ensure that we got the type and ID we were looking for.
+	 * Everything else was checked by the dquot buffer verifier.
+	 */
+	if (!xfs_dquot_check_type(dqp, ddqp)) {
+		xfs_alert_tag(bp->b_mount, XFS_PTAG_VERIFIER_ERROR,
+			  "Metadata corruption detected at %pS, quota %u",
+			  __this_address, dqp->q_id);
+		xfs_alert(bp->b_mount, "Unmount and run xfs_repair");
+		return -EFSCORRUPTED;
+	}
+
+	/* copy everything from disk dquot to the incore dquot */
+	dqp->q_type = ddqp->d_type;
+	dqp->q_blk.hardlimit = be64_to_cpu(ddqp->d_blk_hardlimit);
+	dqp->q_blk.softlimit = be64_to_cpu(ddqp->d_blk_softlimit);
+	dqp->q_ino.hardlimit = be64_to_cpu(ddqp->d_ino_hardlimit);
+	dqp->q_ino.softlimit = be64_to_cpu(ddqp->d_ino_softlimit);
+	dqp->q_rtb.hardlimit = be64_to_cpu(ddqp->d_rtb_hardlimit);
+	dqp->q_rtb.softlimit = be64_to_cpu(ddqp->d_rtb_softlimit);
+
+	dqp->q_blk.count = be64_to_cpu(ddqp->d_bcount);
+	dqp->q_ino.count = be64_to_cpu(ddqp->d_icount);
+	dqp->q_rtb.count = be64_to_cpu(ddqp->d_rtbcount);
+
+	dqp->q_blk.timer = xfs_dquot_from_disk_ts(ddqp, ddqp->d_btimer);
+	dqp->q_ino.timer = xfs_dquot_from_disk_ts(ddqp, ddqp->d_itimer);
+	dqp->q_rtb.timer = xfs_dquot_from_disk_ts(ddqp, ddqp->d_rtbtimer);
+
+	/*
+	 * Reservation counters are defined as reservation plus current usage
+	 * to avoid having to add every time.
+	 */
+	dqp->q_blk.reserved = dqp->q_blk.count;
+	dqp->q_ino.reserved = dqp->q_ino.count;
+	dqp->q_rtb.reserved = dqp->q_rtb.count;
+
+	/* initialize the dquot speculative prealloc thresholds */
+	xfs_dquot_set_prealloc_limits(dqp);
+	return 0;
+}
+
+/* Copy the in-core quota fields into the on-disk buffer. */
+void
+xfs_dquot_to_disk(
+	struct xfs_disk_dquot	*ddqp,
+	struct xfs_dquot	*dqp)
+{
+	ddqp->d_magic = cpu_to_be16(XFS_DQUOT_MAGIC);
+	ddqp->d_version = XFS_DQUOT_VERSION;
+	ddqp->d_type = dqp->q_type;
+	ddqp->d_id = cpu_to_be32(dqp->q_id);
+	ddqp->d_pad0 = 0;
+	ddqp->d_pad = 0;
+
+	ddqp->d_blk_hardlimit = cpu_to_be64(dqp->q_blk.hardlimit);
+	ddqp->d_blk_softlimit = cpu_to_be64(dqp->q_blk.softlimit);
+	ddqp->d_ino_hardlimit = cpu_to_be64(dqp->q_ino.hardlimit);
+	ddqp->d_ino_softlimit = cpu_to_be64(dqp->q_ino.softlimit);
+	ddqp->d_rtb_hardlimit = cpu_to_be64(dqp->q_rtb.hardlimit);
+	ddqp->d_rtb_softlimit = cpu_to_be64(dqp->q_rtb.softlimit);
+
+	ddqp->d_bcount = cpu_to_be64(dqp->q_blk.count);
+	ddqp->d_icount = cpu_to_be64(dqp->q_ino.count);
+	ddqp->d_rtbcount = cpu_to_be64(dqp->q_rtb.count);
+
+	ddqp->d_bwarns = 0;
+	ddqp->d_iwarns = 0;
+	ddqp->d_rtbwarns = 0;
+
+	ddqp->d_btimer = xfs_dquot_to_disk_ts(dqp, dqp->q_blk.timer);
+	ddqp->d_itimer = xfs_dquot_to_disk_ts(dqp, dqp->q_ino.timer);
+	ddqp->d_rtbtimer = xfs_dquot_to_disk_ts(dqp, dqp->q_rtb.timer);
+}
+
+/*
+ * Read in the ondisk dquot using dqtobp() then copy it to an incore version,
+ * and release the buffer immediately.  If @can_alloc is true, fill any
+ * holes in the on-disk metadata.
+ */
+static int
+xfs_qm_dqread(
+	struct xfs_mount	*mp,
+	xfs_dqid_t		id,
+	xfs_dqtype_t		type,
+	bool			can_alloc,
+	struct xfs_dquot	**dqpp)
+{
+	struct xfs_dquot	*dqp;
+	struct xfs_buf		*bp;
+	int			error;
+
+	dqp = xfs_dquot_alloc(mp, id, type);
+	trace_xfs_dqread(dqp);
+
+	/* Try to read the buffer, allocating if necessary. */
+	error = xfs_dquot_disk_read(mp, dqp, &bp);
+	if (error == -ENOENT && can_alloc)
+		error = xfs_dquot_disk_alloc(dqp, &bp);
+	if (error)
+		goto err;
+
+	/*
+	 * At this point we should have a clean locked buffer.  Copy the data
+	 * to the incore dquot and release the buffer since the incore dquot
+	 * has its own locking protocol so we needn't tie up the buffer any
+	 * further.
+	 */
+	ASSERT(xfs_buf_islocked(bp));
+	error = xfs_dquot_from_disk(dqp, bp);
+	xfs_buf_relse(bp);
+	if (error)
+		goto err;
+
+	*dqpp = dqp;
+	return error;
+
+err:
+	trace_xfs_dqread_fail(dqp);
+	xfs_qm_dqdestroy(dqp);
+	*dqpp = NULL;
+	return error;
+}
+
+/*
+ * Advance to the next id in the current chunk, or if at the
+ * end of the chunk, skip ahead to first id in next allocated chunk
+ * using the SEEK_DATA interface.
+ */
+static int
+xfs_dq_get_next_id(
+	struct xfs_mount	*mp,
+	xfs_dqtype_t		type,
+	xfs_dqid_t		*id)
+{
+	struct xfs_inode	*quotip = xfs_quota_inode(mp, type);
+	xfs_dqid_t		next_id = *id + 1; /* simple advance */
+	uint			lock_flags;
+	struct xfs_bmbt_irec	got;
+	struct xfs_iext_cursor	cur;
+	xfs_fsblock_t		start;
+	int			error = 0;
+
+	/* If we'd wrap past the max ID, stop */
+	if (next_id < *id)
+		return -ENOENT;
+
+	/* If new ID is within the current chunk, advancing it sufficed */
+	if (next_id % mp->m_quotainfo->qi_dqperchunk) {
+		*id = next_id;
+		return 0;
+	}
+
+	/* Nope, next_id is now past the current chunk, so find the next one */
+	start = (xfs_fsblock_t)next_id / mp->m_quotainfo->qi_dqperchunk;
+
+	lock_flags = xfs_ilock_data_map_shared(quotip);
+	error = xfs_iread_extents(NULL, quotip, XFS_DATA_FORK);
+	if (error)
+		return error;
+
+	if (xfs_iext_lookup_extent(quotip, &quotip->i_df, start, &cur, &got)) {
+		/* contiguous chunk, bump startoff for the id calculation */
+		if (got.br_startoff < start)
+			got.br_startoff = start;
+		*id = got.br_startoff * mp->m_quotainfo->qi_dqperchunk;
+	} else {
+		error = -ENOENT;
+	}
+
+	xfs_iunlock(quotip, lock_flags);
+
+	return error;
+}
+
+/*
+ * Look up the dquot in the in-core cache.  If found, the dquot is returned
+ * locked and ready to go.
+ */
+static struct xfs_dquot *
+xfs_qm_dqget_cache_lookup(
+	struct xfs_mount	*mp,
+	struct xfs_quotainfo	*qi,
+	struct radix_tree_root	*tree,
+	xfs_dqid_t		id)
+{
+	struct xfs_dquot	*dqp;
+
+restart:
+	mutex_lock(&qi->qi_tree_lock);
+	dqp = radix_tree_lookup(tree, id);
+	if (!dqp) {
+		mutex_unlock(&qi->qi_tree_lock);
+		XFS_STATS_INC(mp, xs_qm_dqcachemisses);
+		return NULL;
+	}
+
+	xfs_dqlock(dqp);
+	if (dqp->q_flags & XFS_DQFLAG_FREEING) {
+		xfs_dqunlock(dqp);
+		mutex_unlock(&qi->qi_tree_lock);
+		trace_xfs_dqget_freeing(dqp);
+		delay(1);
+		goto restart;
+	}
+
+	dqp->q_nrefs++;
+	mutex_unlock(&qi->qi_tree_lock);
+
+	trace_xfs_dqget_hit(dqp);
+	XFS_STATS_INC(mp, xs_qm_dqcachehits);
+	return dqp;
+}
+
+/*
+ * Try to insert a new dquot into the in-core cache.  If an error occurs the
+ * caller should throw away the dquot and start over.  Otherwise, the dquot
+ * is returned locked (and held by the cache) as if there had been a cache
+ * hit.
+ */
+static int
+xfs_qm_dqget_cache_insert(
+	struct xfs_mount	*mp,
+	struct xfs_quotainfo	*qi,
+	struct radix_tree_root	*tree,
+	xfs_dqid_t		id,
+	struct xfs_dquot	*dqp)
+{
+	int			error;
+
+	mutex_lock(&qi->qi_tree_lock);
+	error = radix_tree_insert(tree, id, dqp);
+	if (unlikely(error)) {
+		/* Duplicate found!  Caller must try again. */
+		WARN_ON(error != -EEXIST);
+		mutex_unlock(&qi->qi_tree_lock);
+		trace_xfs_dqget_dup(dqp);
+		return error;
+	}
+
+	/* Return a locked dquot to the caller, with a reference taken. */
+	xfs_dqlock(dqp);
+	dqp->q_nrefs = 1;
+
+	qi->qi_dquots++;
+	mutex_unlock(&qi->qi_tree_lock);
+
+	return 0;
+}
+
+/* Check our input parameters. */
+static int
+xfs_qm_dqget_checks(
+	struct xfs_mount	*mp,
+	xfs_dqtype_t		type)
+{
+	switch (type) {
+	case XFS_DQTYPE_USER:
+		if (!XFS_IS_UQUOTA_ON(mp))
+			return -ESRCH;
+		return 0;
+	case XFS_DQTYPE_GROUP:
+		if (!XFS_IS_GQUOTA_ON(mp))
+			return -ESRCH;
+		return 0;
+	case XFS_DQTYPE_PROJ:
+		if (!XFS_IS_PQUOTA_ON(mp))
+			return -ESRCH;
+		return 0;
+	default:
+		WARN_ON_ONCE(0);
+		return -EINVAL;
+	}
+}
+
+/*
+ * Given the file system, id, and type (UDQUOT/GDQUOT/PDQUOT), return a
+ * locked dquot, doing an allocation (if requested) as needed.
+ */
+int
+xfs_qm_dqget(
+	struct xfs_mount	*mp,
+	xfs_dqid_t		id,
+	xfs_dqtype_t		type,
+	bool			can_alloc,
+	struct xfs_dquot	**O_dqpp)
+{
+	struct xfs_quotainfo	*qi = mp->m_quotainfo;
+	struct radix_tree_root	*tree = xfs_dquot_tree(qi, type);
+	struct xfs_dquot	*dqp;
+	int			error;
+
+	error = xfs_qm_dqget_checks(mp, type);
+	if (error)
+		return error;
+
+restart:
+	dqp = xfs_qm_dqget_cache_lookup(mp, qi, tree, id);
+	if (dqp) {
+		*O_dqpp = dqp;
+		return 0;
+	}
+
+	error = xfs_qm_dqread(mp, id, type, can_alloc, &dqp);
+	if (error)
+		return error;
+
+	error = xfs_qm_dqget_cache_insert(mp, qi, tree, id, dqp);
+	if (error) {
+		/*
+		 * Duplicate found. Just throw away the new dquot and start
+		 * over.
+		 */
+		xfs_qm_dqdestroy(dqp);
+		XFS_STATS_INC(mp, xs_qm_dquot_dups);
+		goto restart;
+	}
+
+	trace_xfs_dqget_miss(dqp);
+	*O_dqpp = dqp;
+	return 0;
+}
+
+/*
+ * Given a dquot id and type, read and initialize a dquot from the on-disk
+ * metadata.  This function is only for use during quota initialization so
+ * it ignores the dquot cache assuming that the dquot shrinker isn't set up.
+ * The caller is responsible for _qm_dqdestroy'ing the returned dquot.
+ */
+int
+xfs_qm_dqget_uncached(
+	struct xfs_mount	*mp,
+	xfs_dqid_t		id,
+	xfs_dqtype_t		type,
+	struct xfs_dquot	**dqpp)
+{
+	int			error;
+
+	error = xfs_qm_dqget_checks(mp, type);
+	if (error)
+		return error;
+
+	return xfs_qm_dqread(mp, id, type, 0, dqpp);
+}
+
+/* Return the quota id for a given inode and type. */
+xfs_dqid_t
+xfs_qm_id_for_quotatype(
+	struct xfs_inode	*ip,
+	xfs_dqtype_t		type)
+{
+	switch (type) {
+	case XFS_DQTYPE_USER:
+		return i_uid_read(VFS_I(ip));
+	case XFS_DQTYPE_GROUP:
+		return i_gid_read(VFS_I(ip));
+	case XFS_DQTYPE_PROJ:
+		return ip->i_projid;
+	}
+	ASSERT(0);
+	return 0;
+}
+
+/*
+ * Return the dquot for a given inode and type.  If @can_alloc is true, then
+ * allocate blocks if needed.  The inode's ILOCK must be held and it must not
+ * have already had an inode attached.
+ */
+int
+xfs_qm_dqget_inode(
+	struct xfs_inode	*ip,
+	xfs_dqtype_t		type,
+	bool			can_alloc,
+	struct xfs_dquot	**O_dqpp)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_quotainfo	*qi = mp->m_quotainfo;
+	struct radix_tree_root	*tree = xfs_dquot_tree(qi, type);
+	struct xfs_dquot	*dqp;
+	xfs_dqid_t		id;
+	int			error;
+
+	error = xfs_qm_dqget_checks(mp, type);
+	if (error)
+		return error;
+
+	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
+	ASSERT(xfs_inode_dquot(ip, type) == NULL);
+
+	id = xfs_qm_id_for_quotatype(ip, type);
+
+restart:
+	dqp = xfs_qm_dqget_cache_lookup(mp, qi, tree, id);
+	if (dqp) {
+		*O_dqpp = dqp;
+		return 0;
+	}
+
+	/*
+	 * Dquot cache miss. We don't want to keep the inode lock across
+	 * a (potential) disk read. Also we don't want to deal with the lock
+	 * ordering between quotainode and this inode. OTOH, dropping the inode
+	 * lock here means dealing with a chown that can happen before
+	 * we re-acquire the lock.
+	 */
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	error = xfs_qm_dqread(mp, id, type, can_alloc, &dqp);
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	if (error)
+		return error;
+
+	/*
+	 * A dquot could be attached to this inode by now, since we had
+	 * dropped the ilock.
+	 */
+	if (xfs_this_quota_on(mp, type)) {
+		struct xfs_dquot	*dqp1;
+
+		dqp1 = xfs_inode_dquot(ip, type);
+		if (dqp1) {
+			xfs_qm_dqdestroy(dqp);
+			dqp = dqp1;
+			xfs_dqlock(dqp);
+			goto dqret;
+		}
+	} else {
+		/* inode stays locked on return */
+		xfs_qm_dqdestroy(dqp);
+		return -ESRCH;
+	}
+
+	error = xfs_qm_dqget_cache_insert(mp, qi, tree, id, dqp);
+	if (error) {
+		/*
+		 * Duplicate found. Just throw away the new dquot and start
+		 * over.
+		 */
+		xfs_qm_dqdestroy(dqp);
+		XFS_STATS_INC(mp, xs_qm_dquot_dups);
+		goto restart;
+	}
+
+dqret:
+	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
+	trace_xfs_dqget_miss(dqp);
+	*O_dqpp = dqp;
+	return 0;
+}
+
+/*
+ * Starting at @id and progressing upwards, look for an initialized incore
+ * dquot, lock it, and return it.
+ */
+int
+xfs_qm_dqget_next(
+	struct xfs_mount	*mp,
+	xfs_dqid_t		id,
+	xfs_dqtype_t		type,
+	struct xfs_dquot	**dqpp)
+{
+	struct xfs_dquot	*dqp;
+	int			error = 0;
+
+	*dqpp = NULL;
+	for (; !error; error = xfs_dq_get_next_id(mp, type, &id)) {
+		error = xfs_qm_dqget(mp, id, type, false, &dqp);
+		if (error == -ENOENT)
+			continue;
+		else if (error != 0)
+			break;
+
+		if (!XFS_IS_DQUOT_UNINITIALIZED(dqp)) {
+			*dqpp = dqp;
+			return 0;
+		}
+
+		xfs_qm_dqput(dqp);
+	}
+
+	return error;
+}
+
+/*
+ * Release a reference to the dquot (decrement ref-count) and unlock it.
+ *
+ * If there is a group quota attached to this dquot, carefully release that
+ * too without tripping over deadlocks'n'stuff.
+ */
+void
+xfs_qm_dqput(
+	struct xfs_dquot	*dqp)
+{
+	ASSERT(dqp->q_nrefs > 0);
+	ASSERT(XFS_DQ_IS_LOCKED(dqp));
+
+	trace_xfs_dqput(dqp);
+
+	if (--dqp->q_nrefs == 0) {
+		struct xfs_quotainfo	*qi = dqp->q_mount->m_quotainfo;
+		trace_xfs_dqput_free(dqp);
+
+		if (list_lru_add(&qi->qi_lru, &dqp->q_lru))
+			XFS_STATS_INC(dqp->q_mount, xs_qm_dquot_unused);
+	}
+	xfs_dqunlock(dqp);
+}
+
+/*
+ * Release a dquot. Flush it if dirty, then dqput() it.
+ * dquot must not be locked.
+ */
+void
+xfs_qm_dqrele(
+	struct xfs_dquot	*dqp)
+{
+	if (!dqp)
+		return;
+
+	trace_xfs_dqrele(dqp);
+
+	xfs_dqlock(dqp);
+	/*
+	 * We don't care to flush it if the dquot is dirty here.
+	 * That will create stutters that we want to avoid.
+	 * Instead we do a delayed write when we try to reclaim
+	 * a dirty dquot. Also xfs_sync will take part of the burden...
+	 */
+	xfs_qm_dqput(dqp);
+}
+
+/*
+ * This is the dquot flushing I/O completion routine.  It is called
+ * from interrupt level when the buffer containing the dquot is
+ * flushed to disk.  It is responsible for removing the dquot logitem
+ * from the AIL if it has not been re-logged, and unlocking the dquot's
+ * flush lock. This behavior is very similar to that of inodes..
+ */
+static void
+xfs_qm_dqflush_done(
+	struct xfs_log_item	*lip)
+{
+	struct xfs_dq_logitem	*qip = (struct xfs_dq_logitem *)lip;
+	struct xfs_dquot	*dqp = qip->qli_dquot;
+	struct xfs_ail		*ailp = lip->li_ailp;
+	xfs_lsn_t		tail_lsn;
+
+	/*
+	 * We only want to pull the item from the AIL if its
+	 * location in the log has not changed since we started the flush.
+	 * Thus, we only bother if the dquot's lsn has
+	 * not changed. First we check the lsn outside the lock
+	 * since it's cheaper, and then we recheck while
+	 * holding the lock before removing the dquot from the AIL.
+	 */
+	if (test_bit(XFS_LI_IN_AIL, &lip->li_flags) &&
+	    ((lip->li_lsn == qip->qli_flush_lsn) ||
+	     test_bit(XFS_LI_FAILED, &lip->li_flags))) {
+
+		spin_lock(&ailp->ail_lock);
+		xfs_clear_li_failed(lip);
+		if (lip->li_lsn == qip->qli_flush_lsn) {
+			/* xfs_ail_update_finish() drops the AIL lock */
+			tail_lsn = xfs_ail_delete_one(ailp, lip);
+			xfs_ail_update_finish(ailp, tail_lsn);
+		} else {
+			spin_unlock(&ailp->ail_lock);
+		}
+	}
+
+	/*
+	 * Release the dq's flush lock since we're done with it.
+	 */
+	xfs_dqfunlock(dqp);
+}
+
+void
+xfs_buf_dquot_iodone(
+	struct xfs_buf		*bp)
+{
+	struct xfs_log_item	*lip, *n;
+
+	list_for_each_entry_safe(lip, n, &bp->b_li_list, li_bio_list) {
+		list_del_init(&lip->li_bio_list);
+		xfs_qm_dqflush_done(lip);
+	}
+}
+
+void
+xfs_buf_dquot_io_fail(
+	struct xfs_buf		*bp)
+{
+	struct xfs_log_item	*lip;
+
+	spin_lock(&bp->b_mount->m_ail->ail_lock);
+	list_for_each_entry(lip, &bp->b_li_list, li_bio_list)
+		xfs_set_li_failed(lip, bp);
+	spin_unlock(&bp->b_mount->m_ail->ail_lock);
+}
+
+/* Check incore dquot for errors before we flush. */
+static xfs_failaddr_t
+xfs_qm_dqflush_check(
+	struct xfs_dquot	*dqp)
+{
+	xfs_dqtype_t		type = xfs_dquot_type(dqp);
+
+	if (type != XFS_DQTYPE_USER &&
+	    type != XFS_DQTYPE_GROUP &&
+	    type != XFS_DQTYPE_PROJ)
+		return __this_address;
+
+	if (dqp->q_id == 0)
+		return NULL;
+
+	if (dqp->q_blk.softlimit && dqp->q_blk.count > dqp->q_blk.softlimit &&
+	    !dqp->q_blk.timer)
+		return __this_address;
+
+	if (dqp->q_ino.softlimit && dqp->q_ino.count > dqp->q_ino.softlimit &&
+	    !dqp->q_ino.timer)
+		return __this_address;
+
+	if (dqp->q_rtb.softlimit && dqp->q_rtb.count > dqp->q_rtb.softlimit &&
+	    !dqp->q_rtb.timer)
+		return __this_address;
+
+	/* bigtime flag should never be set on root dquots */
+	if (dqp->q_type & XFS_DQTYPE_BIGTIME) {
+		if (!xfs_has_bigtime(dqp->q_mount))
+			return __this_address;
+		if (dqp->q_id == 0)
+			return __this_address;
+	}
+
+	return NULL;
+}
+
+/*
+ * Write a modified dquot to disk.
+ * The dquot must be locked and the flush lock too taken by caller.
+ * The flush lock will not be unlocked until the dquot reaches the disk,
+ * but the dquot is free to be unlocked and modified by the caller
+ * in the interim. Dquot is still locked on return. This behavior is
+ * identical to that of inodes.
+ */
+int
+xfs_qm_dqflush(
+	struct xfs_dquot	*dqp,
+	struct xfs_buf		**bpp)
+{
+	struct xfs_mount	*mp = dqp->q_mount;
+	struct xfs_log_item	*lip = &dqp->q_logitem.qli_item;
+	struct xfs_buf		*bp;
+	struct xfs_dqblk	*dqblk;
+	xfs_failaddr_t		fa;
+	int			error;
+
+	ASSERT(XFS_DQ_IS_LOCKED(dqp));
+	ASSERT(!completion_done(&dqp->q_flush));
+
+	trace_xfs_dqflush(dqp);
+
+	*bpp = NULL;
+
+	xfs_qm_dqunpin_wait(dqp);
+
+	/*
+	 * Get the buffer containing the on-disk dquot
+	 */
+	error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp, dqp->q_blkno,
+				   mp->m_quotainfo->qi_dqchunklen, XBF_TRYLOCK,
+				   &bp, &xfs_dquot_buf_ops);
+	if (error == -EAGAIN)
+		goto out_unlock;
+	if (error)
+		goto out_abort;
+
+	fa = xfs_qm_dqflush_check(dqp);
+	if (fa) {
+		xfs_alert(mp, "corrupt dquot ID 0x%x in memory at %pS",
+				dqp->q_id, fa);
+		xfs_buf_relse(bp);
+		error = -EFSCORRUPTED;
+		goto out_abort;
+	}
+
+	/* Flush the incore dquot to the ondisk buffer. */
+	dqblk = bp->b_addr + dqp->q_bufoffset;
+	xfs_dquot_to_disk(&dqblk->dd_diskdq, dqp);
+
+	/*
+	 * Clear the dirty field and remember the flush lsn for later use.
+	 */
+	dqp->q_flags &= ~XFS_DQFLAG_DIRTY;
+
+	xfs_trans_ail_copy_lsn(mp->m_ail, &dqp->q_logitem.qli_flush_lsn,
+					&dqp->q_logitem.qli_item.li_lsn);
+
+	/*
+	 * copy the lsn into the on-disk dquot now while we have the in memory
+	 * dquot here. This can't be done later in the write verifier as we
+	 * can't get access to the log item at that point in time.
+	 *
+	 * We also calculate the CRC here so that the on-disk dquot in the
+	 * buffer always has a valid CRC. This ensures there is no possibility
+	 * of a dquot without an up-to-date CRC getting to disk.
+	 */
+	if (xfs_has_crc(mp)) {
+		dqblk->dd_lsn = cpu_to_be64(dqp->q_logitem.qli_item.li_lsn);
+		xfs_update_cksum((char *)dqblk, sizeof(struct xfs_dqblk),
+				 XFS_DQUOT_CRC_OFF);
+	}
+
+	/*
+	 * Attach the dquot to the buffer so that we can remove this dquot from
+	 * the AIL and release the flush lock once the dquot is synced to disk.
+	 */
+	bp->b_flags |= _XBF_DQUOTS;
+	list_add_tail(&dqp->q_logitem.qli_item.li_bio_list, &bp->b_li_list);
+
+	/*
+	 * If the buffer is pinned then push on the log so we won't
+	 * get stuck waiting in the write for too long.
+	 */
+	if (xfs_buf_ispinned(bp)) {
+		trace_xfs_dqflush_force(dqp);
+		xfs_log_force(mp, 0);
+	}
+
+	trace_xfs_dqflush_done(dqp);
+	*bpp = bp;
+	return 0;
+
+out_abort:
+	dqp->q_flags &= ~XFS_DQFLAG_DIRTY;
+	xfs_trans_ail_delete(lip, 0);
+	xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+out_unlock:
+	xfs_dqfunlock(dqp);
+	return error;
+}
+
+/*
+ * Lock two xfs_dquot structures.
+ *
+ * To avoid deadlocks we always lock the quota structure with
+ * the lowerd id first.
+ */
+void
+xfs_dqlock2(
+	struct xfs_dquot	*d1,
+	struct xfs_dquot	*d2)
+{
+	if (d1 && d2) {
+		ASSERT(d1 != d2);
+		if (d1->q_id > d2->q_id) {
+			mutex_lock(&d2->q_qlock);
+			mutex_lock_nested(&d1->q_qlock, XFS_QLOCK_NESTED);
+		} else {
+			mutex_lock(&d1->q_qlock);
+			mutex_lock_nested(&d2->q_qlock, XFS_QLOCK_NESTED);
+		}
+	} else if (d1) {
+		mutex_lock(&d1->q_qlock);
+	} else if (d2) {
+		mutex_lock(&d2->q_qlock);
+	}
+}
+
+int __init
+xfs_qm_init(void)
+{
+	xfs_dquot_cache = kmem_cache_create("xfs_dquot",
+					  sizeof(struct xfs_dquot),
+					  0, 0, NULL);
+	if (!xfs_dquot_cache)
+		goto out;
+
+	xfs_dqtrx_cache = kmem_cache_create("xfs_dqtrx",
+					     sizeof(struct xfs_dquot_acct),
+					     0, 0, NULL);
+	if (!xfs_dqtrx_cache)
+		goto out_free_dquot_cache;
+
+	return 0;
+
+out_free_dquot_cache:
+	kmem_cache_destroy(xfs_dquot_cache);
+out:
+	return -ENOMEM;
+}
+
+void
+xfs_qm_exit(void)
+{
+	kmem_cache_destroy(xfs_dqtrx_cache);
+	kmem_cache_destroy(xfs_dquot_cache);
+}
+
+/*
+ * Iterate every dquot of a particular type.  The caller must ensure that the
+ * particular quota type is active.  iter_fn can return negative error codes,
+ * or -ECANCELED to indicate that it wants to stop iterating.
+ */
+int
+xfs_qm_dqiterate(
+	struct xfs_mount	*mp,
+	xfs_dqtype_t		type,
+	xfs_qm_dqiterate_fn	iter_fn,
+	void			*priv)
+{
+	struct xfs_dquot	*dq;
+	xfs_dqid_t		id = 0;
+	int			error;
+
+	do {
+		error = xfs_qm_dqget_next(mp, id, type, &dq);
+		if (error == -ENOENT)
+			return 0;
+		if (error)
+			return error;
+
+		error = iter_fn(dq, type, priv);
+		id = dq->q_id;
+		xfs_qm_dqput(dq);
+	} while (error == 0 && id != 0);
+
+	return error;
+}