xfs: avoid ilock games in the quota scrubber

Refactor the quota scrubber to take the quotaofflock and grab the quota
inode in the setup function so that we can treat quota in the same
"scrub in the context of this inode" (i.e. sc->ip) manner as we treat
any other inode.  We do have to drop the quota inode's ILOCK_EXCL to use
dqiterate, but since dquots have their own individual locks the ILOCK
wasn't helping us anyway.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/scrub/quota.c

@@ -66,12 +66,24 @@ xfs_scrub_setup_quota(
 	struct xfs_inode		*ip)
 {
 	uint				dqtype;
+	int				error;
+
+	if (!XFS_IS_QUOTA_RUNNING(sc->mp) || !XFS_IS_QUOTA_ON(sc->mp))
+		return -ENOENT;
 
 	dqtype = xfs_scrub_quota_to_dqtype(sc);
 	if (dqtype == 0)
 		return -EINVAL;
+	sc->has_quotaofflock = true;
+	mutex_lock(&sc->mp->m_quotainfo->qi_quotaofflock);
 	if (!xfs_this_quota_on(sc->mp, dqtype))
 		return -ENOENT;
+	error = xfs_scrub_setup_fs(sc, ip);
+	if (error)
+		return error;
+	sc->ip = xfs_quota_inode(sc->mp, dqtype);
+	xfs_ilock(sc->ip, XFS_ILOCK_EXCL);
+	sc->ilock_flags = XFS_ILOCK_EXCL;
 	return 0;
 }
 
@@ -202,7 +214,6 @@ xfs_scrub_quota(
 	struct xfs_bmbt_irec		irec = { 0 };
 	struct xfs_scrub_quota_info	sqi;
 	struct xfs_mount		*mp = sc->mp;
-	struct xfs_inode		*ip;
 	struct xfs_quotainfo		*qi = mp->m_quotainfo;
 	xfs_fileoff_t			max_dqid_off;
 	xfs_fileoff_t			off = 0;
@@ -210,25 +221,12 @@ xfs_scrub_quota(
 	int				nimaps;
 	int				error = 0;
 
-	if (!XFS_IS_QUOTA_RUNNING(mp) || !XFS_IS_QUOTA_ON(mp))
-		return -ENOENT;
-
-	mutex_lock(&qi->qi_quotaofflock);
 	dqtype = xfs_scrub_quota_to_dqtype(sc);
-	if (!xfs_this_quota_on(sc->mp, dqtype)) {
-		error = -ENOENT;
-		goto out_unlock_quota;
-	}
-
-	/* Attach to the quota inode and set sc->ip so that reporting works. */
-	ip = xfs_quota_inode(sc->mp, dqtype);
-	sc->ip = ip;
 
 	/* Look for problem extents. */
-	xfs_ilock(ip, XFS_ILOCK_EXCL);
-	if (ip->i_d.di_flags & XFS_DIFLAG_REALTIME) {
+	if (sc->ip->i_d.di_flags & XFS_DIFLAG_REALTIME) {
 		xfs_scrub_ino_set_corrupt(sc, sc->ip->i_ino);
-		goto out_unlock_inode;
+		goto out;
 	}
 	max_dqid_off = ((xfs_dqid_t)-1) / qi->qi_dqperchunk;
 	while (1) {
@@ -237,11 +235,11 @@ xfs_scrub_quota(
 
 		off = irec.br_startoff + irec.br_blockcount;
 		nimaps = 1;
-		error = xfs_bmapi_read(ip, off, -1, &irec, &nimaps,
+		error = xfs_bmapi_read(sc->ip, off, -1, &irec, &nimaps,
 				XFS_BMAPI_ENTIRE);
 		if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, off,
 				&error))
-			goto out_unlock_inode;
+			goto out;
 		if (!nimaps)
 			break;
 		if (irec.br_startblock == HOLESTARTBLOCK)
@@ -267,26 +265,25 @@ xfs_scrub_quota(
 		    irec.br_startoff + irec.br_blockcount > max_dqid_off + 1)
 			xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, off);
 	}
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
 		goto out;
 
-	/* Check all the quota items. */
+	/*
+	 * Check all the quota items.  Now that we've checked the quota inode
+	 * data fork we have to drop ILOCK_EXCL to use the regular dquot
+	 * functions.
+	 */
+	xfs_iunlock(sc->ip, sc->ilock_flags);
+	sc->ilock_flags = 0;
 	sqi.sc = sc;
 	sqi.last_id = 0;
 	error = xfs_qm_dqiterate(mp, dqtype, xfs_scrub_quota_item, &sqi);
+	sc->ilock_flags = XFS_ILOCK_EXCL;
+	xfs_ilock(sc->ip, sc->ilock_flags);
 	if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK,
 			sqi.last_id * qi->qi_dqperchunk, &error))
 		goto out;
 
 out:
-	/* We set sc->ip earlier, so make sure we clear it now. */
-	sc->ip = NULL;
-out_unlock_quota:
-	mutex_unlock(&qi->qi_quotaofflock);
 	return error;
-
-out_unlock_inode:
-	xfs_iunlock(ip, XFS_ILOCK_EXCL);
-	goto out;
 }

fs/xfs/scrub/scrub.c

@@ -42,6 +42,8 @@
 #include "xfs_refcount_btree.h"
 #include "xfs_rmap.h"
 #include "xfs_rmap_btree.h"
+#include "xfs_quota.h"
+#include "xfs_qm.h"
 #include "scrub/xfs_scrub.h"
 #include "scrub/scrub.h"
 #include "scrub/common.h"
@@ -166,6 +168,8 @@ xfs_scrub_teardown(
 			iput(VFS_I(sc->ip));
 		sc->ip = NULL;
 	}
+	if (sc->has_quotaofflock)
+		mutex_unlock(&sc->mp->m_quotainfo->qi_quotaofflock);
 	if (sc->buf) {
 		kmem_free(sc->buf);
 		sc->buf = NULL;

fs/xfs/scrub/scrub.h

@@ -73,6 +73,7 @@ struct xfs_scrub_context {
 	void				*buf;
 	uint				ilock_flags;
 	bool				try_harder;
+	bool				has_quotaofflock;
 
 	/* State tracking for single-AG operations. */
 	struct xfs_scrub_ag		sa;