[PATCH 16/21] xfs: repair the rmapbt

From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: darrick.wong@oracle.com
Cc: linux-xfs@vger.kernel.org, david@fromorbit.com
Subject: [PATCH 16/21] xfs: repair the rmapbt
Date: Mon, 02 Apr 2018 12:57:55 -0700	[thread overview]
Message-ID: <152269907556.16346.8583761990782285048.stgit@magnolia> (raw)
In-Reply-To: <152269897182.16346.1710955088267364781.stgit@magnolia>

From: Darrick J. Wong <darrick.wong@oracle.com>

Rebuild the reverse mapping btree from all primary metadata.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/Makefile            |    1 
 fs/xfs/scrub/repair.c      |   74 ++++
 fs/xfs/scrub/repair.h      |   20 +
 fs/xfs/scrub/rmap.c        |    6 
 fs/xfs/scrub/rmap_repair.c |  798 ++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/scrub/scrub.c       |   17 +
 fs/xfs/scrub/scrub.h       |    1 
 fs/xfs/xfs_mount.h         |    1 
 fs/xfs/xfs_super.c         |   27 +
 9 files changed, 942 insertions(+), 3 deletions(-)
 create mode 100644 fs/xfs/scrub/rmap_repair.c

diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index c8174a7..f096dfc 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -177,6 +177,7 @@ xfs-y				+= $(addprefix scrub/, \
 				   alloc_repair.o \
 				   ialloc_repair.o \
 				   repair.o \
+				   rmap_repair.o \
 				   )
 endif
 endif
diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
index 11c2257..76fc43a 100644
--- a/fs/xfs/scrub/repair.c
+++ b/fs/xfs/scrub/repair.c
@@ -879,3 +879,77 @@ xfs_repair_calc_ag_resblks(
 
 	return max(max(bnobt_sz, inobt_sz), max(rmapbt_sz, refcbt_sz));
 }
+
+/* Freeze the FS against outside activity. */
+int
+xfs_repair_fs_freeze(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_mount		*mp = sc->mp;
+	struct super_block		*sb = mp->m_super;
+	int				error;
+
+	xfs_icache_disable_reclaim(mp);
+
+	/* Freeze out any further writes or page faults. */
+	error = freeze_super(sb);
+	if (error)
+		return error;
+
+	/* Thaw it to the point that we can make transactions. */
+	down_write(&sb->s_umount);
+	sb->s_writers.frozen = SB_FREEZE_FS;
+	percpu_rwsem_acquire(sb->s_writers.rw_sem + SB_FREEZE_FS - 1,
+			0, _THIS_IP_);
+	percpu_up_write(sb->s_writers.rw_sem + SB_FREEZE_FS - 1);
+	up_write(&sb->s_umount);
+	sc->fs_frozen = true;
+
+	return 0;
+}
+
+/* Unfreeze the FS. */
+int
+xfs_repair_fs_thaw(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_mount		*mp = sc->mp;
+	struct super_block		*sb = mp->m_super;
+	int				error;
+
+	WARN_ON(sb->s_writers.frozen != SB_FREEZE_FS);
+
+	/* Re-freeze the last level of filesystem. */
+	down_write(&sb->s_umount);
+	percpu_down_write(sb->s_writers.rw_sem + SB_FREEZE_FS - 1);
+	percpu_rwsem_release(sb->s_writers.rw_sem + SB_FREEZE_FS - 1,
+			0, _THIS_IP_);
+	sb->s_writers.frozen = SB_FREEZE_COMPLETE;
+	up_write(&sb->s_umount);
+
+	/* Thaw everything. */
+	error = thaw_super(sb);
+	xfs_icache_enable_reclaim(mp);
+	return error;
+}
+
+/* Read all AG headers and attach to this transaction. */
+int
+xfs_repair_grab_all_ag_headers(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_mount		*mp = sc->mp;
+	struct xfs_buf			*agi;
+	struct xfs_buf			*agf;
+	struct xfs_buf			*agfl;
+	xfs_agnumber_t			agno;
+	int				error = 0;
+
+	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+		error = xfs_scrub_ag_read_headers(sc, agno, &agi, &agf, &agfl);
+		if (error)
+			break;
+	}
+
+	return error;
+}
diff --git a/fs/xfs/scrub/repair.h b/fs/xfs/scrub/repair.h
index 7a3af29..0232f28 100644
--- a/fs/xfs/scrub/repair.h
+++ b/fs/xfs/scrub/repair.h
@@ -85,6 +85,10 @@ int xfs_repair_find_ag_btree_roots(struct xfs_scrub_context *sc,
 int xfs_repair_reset_counters(struct xfs_mount *mp);
 xfs_extlen_t xfs_repair_calc_ag_resblks(struct xfs_scrub_context *sc);
 int xfs_repair_setup_btree_extent_collection(struct xfs_scrub_context *sc);
+int xfs_repair_fs_freeze(struct xfs_scrub_context *sc);
+int xfs_repair_fs_thaw(struct xfs_scrub_context *sc);
+int xfs_repair_grab_all_ag_headers(struct xfs_scrub_context *sc);
+int xfs_repair_rmapbt_setup(struct xfs_scrub_context *sc, struct xfs_inode *ip);
 
 /* Metadata repairers */
 int xfs_repair_superblock(struct xfs_scrub_context *sc);
@@ -93,6 +97,7 @@ int xfs_repair_agfl(struct xfs_scrub_context *sc);
 int xfs_repair_agi(struct xfs_scrub_context *sc);
 int xfs_repair_allocbt(struct xfs_scrub_context *sc);
 int xfs_repair_iallocbt(struct xfs_scrub_context *sc);
+int xfs_repair_rmapbt(struct xfs_scrub_context *sc);
 
 #else
 
@@ -112,12 +117,27 @@ xfs_repair_calc_ag_resblks(
 	return 0;
 }
 
+static inline int xfs_repair_fs_thaw(struct xfs_scrub_context *sc)
+{
+	ASSERT(0);
+	return -EIO;
+}
+
+static inline int xfs_repair_rmapbt_setup(
+	struct xfs_scrub_context	*sc,
+	struct xfs_inode		*ip)
+{
+	/* We don't support rmap repair, but we can still do a scan. */
+	return xfs_scrub_setup_ag_btree(sc, ip, false);
+}
+
 #define xfs_repair_superblock		(NULL)
 #define xfs_repair_agf			(NULL)
 #define xfs_repair_agfl			(NULL)
 #define xfs_repair_agi			(NULL)
 #define xfs_repair_allocbt		(NULL)
 #define xfs_repair_iallocbt		(NULL)
+#define xfs_repair_rmapbt		(NULL)
 
 #endif /* CONFIG_XFS_ONLINE_REPAIR */
 
diff --git a/fs/xfs/scrub/rmap.c b/fs/xfs/scrub/rmap.c
index b7c2ef4..fd98e9d 100644
--- a/fs/xfs/scrub/rmap.c
+++ b/fs/xfs/scrub/rmap.c
@@ -38,6 +38,7 @@
 #include "scrub/common.h"
 #include "scrub/btree.h"
 #include "scrub/trace.h"
+#include "scrub/repair.h"
 
 /*
  * Set us up to scrub reverse mapping btrees.
@@ -47,7 +48,10 @@ xfs_scrub_setup_ag_rmapbt(
 	struct xfs_scrub_context	*sc,
 	struct xfs_inode		*ip)
 {
-	return xfs_scrub_setup_ag_btree(sc, ip, false);
+	if (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
+		return xfs_repair_rmapbt_setup(sc, ip);
+	else
+		return xfs_scrub_setup_ag_btree(sc, ip, false);
 }
 
 /* Reverse-mapping scrubber. */
diff --git a/fs/xfs/scrub/rmap_repair.c b/fs/xfs/scrub/rmap_repair.c
new file mode 100644
index 0000000..fbb8bcd
--- /dev/null
+++ b/fs/xfs/scrub/rmap_repair.c
@@ -0,0 +1,798 @@
+/*
+ * Copyright (C) 2018 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * 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; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * 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_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_btree.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_alloc.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_ialloc.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_rmap.h"
+#include "xfs_rmap_btree.h"
+#include "xfs_inode.h"
+#include "xfs_icache.h"
+#include "xfs_bmap.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_refcount.h"
+#include "xfs_refcount_btree.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/btree.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+
+/* Reverse-mapping repair. */
+
+/* Set us up to repair reverse mapping btrees. */
+int
+xfs_repair_rmapbt_setup(
+	struct xfs_scrub_context	*sc,
+	struct xfs_inode		*ip)
+{
+	int				error;
+
+	/*
+	 * Freeze out anything that can lock an inode.  We reconstruct
+	 * the rmapbt by reading inode bmaps with the AGF held, which is
+	 * only safe w.r.t. ABBA deadlocks if we're the only ones locking
+	 * inodes.
+	 */
+	error = xfs_repair_fs_freeze(sc);
+	if (error)
+		return error;
+
+	/* Check the AG number and set up the scrub context. */
+	error = xfs_scrub_setup_fs(sc, ip);
+	if (error)
+		return error;
+
+	/*
+	 * Lock all the AG header buffers so that we can read all the
+	 * per-AG metadata too.
+	 */
+	error = xfs_repair_grab_all_ag_headers(sc);
+	if (error)
+		return error;
+
+	return xfs_scrub_ag_init(sc, sc->sm->sm_agno, &sc->sa);
+}
+
+struct xfs_repair_rmapbt_extent {
+	struct list_head		list;
+	struct xfs_rmap_irec		rmap;
+};
+
+struct xfs_repair_rmapbt {
+	struct list_head		rmaplist;
+	struct xfs_repair_extent_list	rmap_freelist;
+	struct xfs_repair_extent_list	bno_freelist;
+	struct xfs_scrub_context	*sc;
+	uint64_t			owner;
+	xfs_extlen_t			btblocks;
+	xfs_agblock_t			next_bno;
+	uint64_t			nr_records;
+};
+
+/* Initialize an rmap. */
+static inline int
+xfs_repair_rmapbt_new_rmap(
+	struct xfs_repair_rmapbt	*rr,
+	xfs_agblock_t			startblock,
+	xfs_extlen_t			blockcount,
+	uint64_t			owner,
+	uint64_t			offset,
+	unsigned int			flags)
+{
+	struct xfs_repair_rmapbt_extent	*rre;
+	int				error = 0;
+
+	trace_xfs_repair_rmap_extent_fn(rr->sc->mp, rr->sc->sa.agno,
+			startblock, blockcount, owner, offset, flags);
+
+	if (xfs_scrub_should_terminate(rr->sc, &error))
+		return error;
+
+	rre = kmem_alloc(sizeof(struct xfs_repair_rmapbt_extent),
+			KM_MAYFAIL | KM_NOFS);
+	if (!rre)
+		return -ENOMEM;
+	INIT_LIST_HEAD(&rre->list);
+	rre->rmap.rm_startblock = startblock;
+	rre->rmap.rm_blockcount = blockcount;
+	rre->rmap.rm_owner = owner;
+	rre->rmap.rm_offset = offset;
+	rre->rmap.rm_flags = flags;
+	list_add_tail(&rre->list, &rr->rmaplist);
+	rr->nr_records++;
+
+	return 0;
+}
+
+/* Add an AGFL block to the rmap list. */
+STATIC int
+xfs_repair_rmapbt_walk_agfl(
+	struct xfs_mount		*mp,
+	xfs_agblock_t			bno,
+	void				*priv)
+{
+	struct xfs_repair_rmapbt	*rr = priv;
+
+	return xfs_repair_rmapbt_new_rmap(rr, bno, 1, XFS_RMAP_OWN_AG, 0, 0);
+}
+
+/* Add a btree block to the rmap list. */
+STATIC int
+xfs_repair_rmapbt_visit_btblock(
+	struct xfs_btree_cur		*cur,
+	int				level,
+	void				*priv)
+{
+	struct xfs_repair_rmapbt	*rr = priv;
+	struct xfs_buf			*bp;
+	xfs_fsblock_t			fsb;
+
+	xfs_btree_get_block(cur, level, &bp);
+	if (!bp)
+		return 0;
+
+	rr->btblocks++;
+	fsb = XFS_DADDR_TO_FSB(cur->bc_mp, bp->b_bn);
+	return xfs_repair_rmapbt_new_rmap(rr, XFS_FSB_TO_AGBNO(cur->bc_mp, fsb),
+			1, rr->owner, 0, 0);
+}
+
+/* Record inode btree rmaps. */
+STATIC int
+xfs_repair_rmapbt_inodes(
+	struct xfs_btree_cur		*cur,
+	union xfs_btree_rec		*rec,
+	void				*priv)
+{
+	struct xfs_inobt_rec_incore	irec;
+	struct xfs_repair_rmapbt	*rr = priv;
+	struct xfs_mount		*mp = cur->bc_mp;
+	struct xfs_buf			*bp;
+	xfs_fsblock_t			fsb;
+	xfs_agino_t			agino;
+	xfs_agino_t			iperhole;
+	unsigned int			i;
+	int				error;
+
+	/* Record the inobt blocks */
+	for (i = 0; i < cur->bc_nlevels && cur->bc_ptrs[i] == 1; i++) {
+		xfs_btree_get_block(cur, i, &bp);
+		if (!bp)
+			continue;
+		fsb = XFS_DADDR_TO_FSB(mp, bp->b_bn);
+		error = xfs_repair_rmapbt_new_rmap(rr,
+				XFS_FSB_TO_AGBNO(mp, fsb), 1,
+				XFS_RMAP_OWN_INOBT, 0, 0);
+		if (error)
+			return error;
+	}
+
+	xfs_inobt_btrec_to_irec(mp, rec, &irec);
+
+	/* Record a non-sparse inode chunk. */
+	if (irec.ir_holemask == XFS_INOBT_HOLEMASK_FULL)
+		return xfs_repair_rmapbt_new_rmap(rr,
+				XFS_AGINO_TO_AGBNO(mp, irec.ir_startino),
+				XFS_INODES_PER_CHUNK / mp->m_sb.sb_inopblock,
+				XFS_RMAP_OWN_INODES, 0, 0);
+
+	/* Iterate each chunk. */
+	iperhole = max_t(xfs_agino_t, mp->m_sb.sb_inopblock,
+			XFS_INODES_PER_HOLEMASK_BIT);
+	for (i = 0, agino = irec.ir_startino;
+	     i < XFS_INOBT_HOLEMASK_BITS;
+	     i += iperhole / XFS_INODES_PER_HOLEMASK_BIT, agino += iperhole) {
+		/* Skip holes. */
+		if (irec.ir_holemask & (1 << i))
+			continue;
+
+		/* Record the inode chunk otherwise. */
+		error = xfs_repair_rmapbt_new_rmap(rr,
+				XFS_AGINO_TO_AGBNO(mp, agino),
+				iperhole / mp->m_sb.sb_inopblock,
+				XFS_RMAP_OWN_INODES, 0, 0);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+/* Record a CoW staging extent. */
+STATIC int
+xfs_repair_rmapbt_refcount(
+	struct xfs_btree_cur		*cur,
+	union xfs_btree_rec		*rec,
+	void				*priv)
+{
+	struct xfs_repair_rmapbt	*rr = priv;
+	struct xfs_refcount_irec	refc;
+
+	xfs_refcount_btrec_to_irec(rec, &refc);
+	if (refc.rc_refcount != 1)
+		return -EFSCORRUPTED;
+
+	return xfs_repair_rmapbt_new_rmap(rr,
+			refc.rc_startblock - XFS_REFC_COW_START,
+			refc.rc_blockcount, XFS_RMAP_OWN_COW, 0, 0);
+}
+
+/* Add a bmbt block to the rmap list. */
+STATIC int
+xfs_repair_rmapbt_visit_bmbt(
+	struct xfs_btree_cur		*cur,
+	int				level,
+	void				*priv)
+{
+	struct xfs_repair_rmapbt	*rr = priv;
+	struct xfs_buf			*bp;
+	xfs_fsblock_t			fsb;
+	unsigned int			flags = XFS_RMAP_BMBT_BLOCK;
+
+	xfs_btree_get_block(cur, level, &bp);
+	if (!bp)
+		return 0;
+
+	fsb = XFS_DADDR_TO_FSB(cur->bc_mp, bp->b_bn);
+	if (XFS_FSB_TO_AGNO(cur->bc_mp, fsb) != rr->sc->sa.agno)
+		return 0;
+
+	if (cur->bc_private.b.whichfork == XFS_ATTR_FORK)
+		flags |= XFS_RMAP_ATTR_FORK;
+	return xfs_repair_rmapbt_new_rmap(rr,
+			XFS_FSB_TO_AGBNO(cur->bc_mp, fsb), 1,
+			cur->bc_private.b.ip->i_ino, 0, flags);
+}
+
+/* Determine rmap flags from fork and bmbt state. */
+static inline unsigned int
+xfs_repair_rmapbt_bmap_flags(
+	int			whichfork,
+	xfs_exntst_t		state)
+{
+	return  (whichfork == XFS_ATTR_FORK ? XFS_RMAP_ATTR_FORK : 0) |
+		(state == XFS_EXT_UNWRITTEN ? XFS_RMAP_UNWRITTEN : 0);
+}
+
+/* Find all the extents from a given AG in an inode fork. */
+STATIC int
+xfs_repair_rmapbt_scan_ifork(
+	struct xfs_repair_rmapbt	*rr,
+	struct xfs_inode		*ip,
+	int				whichfork)
+{
+	struct xfs_bmbt_irec		rec;
+	struct xfs_iext_cursor		icur;
+	struct xfs_mount		*mp = rr->sc->mp;
+	struct xfs_btree_cur		*cur = NULL;
+	struct xfs_ifork		*ifp;
+	unsigned int			rflags;
+	int				fmt;
+	int				error = 0;
+
+	/* Do we even have data mapping extents? */
+	fmt = XFS_IFORK_FORMAT(ip, whichfork);
+	ifp = XFS_IFORK_PTR(ip, whichfork);
+	switch (fmt) {
+	case XFS_DINODE_FMT_BTREE:
+		if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+			error = xfs_iread_extents(rr->sc->tp, ip, whichfork);
+			if (error)
+				return error;
+		}
+		break;
+	case XFS_DINODE_FMT_EXTENTS:
+		break;
+	default:
+		return 0;
+	}
+	if (!ifp)
+		return 0;
+
+	/* Find all the BMBT blocks in the AG. */
+	if (fmt == XFS_DINODE_FMT_BTREE) {
+		cur = xfs_bmbt_init_cursor(mp, rr->sc->tp, ip, whichfork);
+		error = xfs_btree_visit_blocks(cur,
+				xfs_repair_rmapbt_visit_bmbt, rr);
+		if (error)
+			goto out;
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+	}
+
+	/* We're done if this is an rt inode's data fork. */
+	if (whichfork == XFS_DATA_FORK && XFS_IS_REALTIME_INODE(ip))
+		return 0;
+
+	/* Find all the extents in the AG. */
+	for_each_xfs_iext(ifp, &icur, &rec) {
+		if (isnullstartblock(rec.br_startblock))
+			continue;
+		/* Stash non-hole extent. */
+		if (XFS_FSB_TO_AGNO(mp, rec.br_startblock) == rr->sc->sa.agno) {
+			rflags = xfs_repair_rmapbt_bmap_flags(whichfork,
+					rec.br_state);
+			error = xfs_repair_rmapbt_new_rmap(rr,
+					XFS_FSB_TO_AGBNO(mp, rec.br_startblock),
+					rec.br_blockcount, ip->i_ino,
+					rec.br_startoff, rflags);
+			if (error)
+				goto out;
+		}
+	}
+out:
+	if (cur)
+		xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+	return error;
+}
+
+/* Iterate all the inodes in an AG group. */
+STATIC int
+xfs_repair_rmapbt_scan_inobt(
+	struct xfs_btree_cur		*cur,
+	union xfs_btree_rec		*rec,
+	void				*priv)
+{
+	struct xfs_inobt_rec_incore	irec;
+	struct xfs_mount		*mp = cur->bc_mp;
+	struct xfs_inode		*ip = NULL;
+	xfs_ino_t			ino;
+	xfs_agino_t			agino;
+	int				chunkidx;
+	int				lock_mode = 0;
+	int				error = 0;
+
+	xfs_inobt_btrec_to_irec(mp, rec, &irec);
+
+	for (chunkidx = 0, agino = irec.ir_startino;
+	     chunkidx < XFS_INODES_PER_CHUNK;
+	     chunkidx++, agino++) {
+		bool	inuse;
+
+		/* Skip if this inode is free */
+		if (XFS_INOBT_MASK(chunkidx) & irec.ir_free)
+			continue;
+		ino = XFS_AGINO_TO_INO(mp, cur->bc_private.a.agno, agino);
+
+		/* Back off and try again if an inode is being reclaimed */
+		error = xfs_icache_inode_is_allocated(mp, cur->bc_tp, ino,
+				&inuse);
+		if (error == -EAGAIN)
+			return -EDEADLOCK;
+
+		/*
+		 * Grab inode for scanning.  We cannot use DONTCACHE here
+		 * because we already have a transaction so the iput must not
+		 * trigger inode reclaim (which might allocate a transaction
+		 * to clean up posteof blocks).
+		 */
+		error = xfs_iget(mp, cur->bc_tp, ino, 0, 0, &ip);
+		if (error)
+			return error;
+
+		if ((ip->i_d.di_format == XFS_DINODE_FMT_BTREE &&
+		     !(ip->i_df.if_flags & XFS_IFEXTENTS)) ||
+		    (ip->i_d.di_aformat == XFS_DINODE_FMT_BTREE &&
+		     !(ip->i_afp->if_flags & XFS_IFEXTENTS)))
+			lock_mode = XFS_ILOCK_EXCL;
+		else
+			lock_mode = XFS_ILOCK_SHARED;
+		if (!xfs_ilock_nowait(ip, lock_mode)) {
+			error = -EBUSY;
+			goto out_rele;
+		}
+
+		/* Check the data fork. */
+		error = xfs_repair_rmapbt_scan_ifork(priv, ip, XFS_DATA_FORK);
+		if (error)
+			goto out_unlock;
+
+		/* Check the attr fork. */
+		error = xfs_repair_rmapbt_scan_ifork(priv, ip, XFS_ATTR_FORK);
+		if (error)
+			goto out_unlock;
+
+		xfs_iunlock(ip, lock_mode);
+		iput(VFS_I(ip));
+		ip = NULL;
+	}
+
+	return error;
+out_unlock:
+	xfs_iunlock(ip, lock_mode);
+out_rele:
+	iput(VFS_I(ip));
+	return error;
+}
+
+/* Record extents that aren't in use from gaps in the rmap records. */
+STATIC int
+xfs_repair_rmapbt_record_rmap_freesp(
+	struct xfs_btree_cur		*cur,
+	struct xfs_rmap_irec		*rec,
+	void				*priv)
+{
+	struct xfs_repair_rmapbt	*rr = priv;
+	xfs_fsblock_t			fsb;
+	int				error;
+
+	/* Record the free space we find. */
+	if (rec->rm_startblock > rr->next_bno) {
+		fsb = XFS_AGB_TO_FSB(cur->bc_mp, cur->bc_private.a.agno,
+				rr->next_bno);
+		error = xfs_repair_collect_btree_extent(rr->sc,
+				&rr->rmap_freelist, fsb,
+				rec->rm_startblock - rr->next_bno);
+		if (error)
+			return error;
+	}
+	rr->next_bno = max_t(xfs_agblock_t, rr->next_bno,
+			rec->rm_startblock + rec->rm_blockcount);
+	return 0;
+}
+
+/* Record extents that aren't in use from the bnobt records. */
+STATIC int
+xfs_repair_rmapbt_record_bno_freesp(
+	struct xfs_btree_cur		*cur,
+	struct xfs_alloc_rec_incore	*rec,
+	void				*priv)
+{
+	struct xfs_repair_rmapbt	*rr = priv;
+	xfs_fsblock_t			fsb;
+
+	/* Record the free space we find. */
+	fsb = XFS_AGB_TO_FSB(cur->bc_mp, cur->bc_private.a.agno,
+			rec->ar_startblock);
+	return xfs_repair_collect_btree_extent(rr->sc, &rr->bno_freelist,
+			fsb, rec->ar_blockcount);
+}
+
+/* Compare two rmapbt extents. */
+static int
+xfs_repair_rmapbt_extent_cmp(
+	void				*priv,
+	struct list_head		*a,
+	struct list_head		*b)
+{
+	struct xfs_repair_rmapbt_extent	*ap;
+	struct xfs_repair_rmapbt_extent	*bp;
+
+	ap = container_of(a, struct xfs_repair_rmapbt_extent, list);
+	bp = container_of(b, struct xfs_repair_rmapbt_extent, list);
+	return xfs_rmap_compare(&ap->rmap, &bp->rmap);
+}
+
+#define RMAP(type, startblock, blockcount) xfs_repair_rmapbt_new_rmap( \
+		&rr, (startblock), (blockcount), \
+		XFS_RMAP_OWN_##type, 0, 0)
+/* Repair the rmap btree for some AG. */
+int
+xfs_repair_rmapbt(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_repair_rmapbt	rr;
+	struct xfs_owner_info		oinfo;
+	struct xfs_repair_rmapbt_extent	*rre;
+	struct xfs_repair_rmapbt_extent	*n;
+	struct xfs_mount		*mp = sc->mp;
+	struct xfs_btree_cur		*cur = NULL;
+	struct xfs_buf			*bp = NULL;
+	struct xfs_agf			*agf;
+	struct xfs_agi			*agi;
+	struct xfs_perag		*pag;
+	xfs_fsblock_t			btfsb;
+	xfs_agnumber_t			ag;
+	xfs_agblock_t			agend;
+	xfs_extlen_t			freesp_btblocks;
+	int				error;
+
+	INIT_LIST_HEAD(&rr.rmaplist);
+	xfs_repair_init_extent_list(&rr.rmap_freelist);
+	xfs_repair_init_extent_list(&rr.bno_freelist);
+	rr.sc = sc;
+	rr.nr_records = 0;
+
+	/* Collect rmaps for all AG headers. */
+	error = RMAP(FS, XFS_SB_BLOCK(mp), 1);
+	if (error)
+		goto out;
+	rre = list_last_entry(&rr.rmaplist, struct xfs_repair_rmapbt_extent,
+			list);
+
+	if (rre->rmap.rm_startblock != XFS_AGF_BLOCK(mp)) {
+		error = RMAP(FS, XFS_AGF_BLOCK(mp), 1);
+		if (error)
+			goto out;
+		rre = list_last_entry(&rr.rmaplist,
+				struct xfs_repair_rmapbt_extent, list);
+	}
+
+	if (rre->rmap.rm_startblock != XFS_AGI_BLOCK(mp)) {
+		error = RMAP(FS, XFS_AGI_BLOCK(mp), 1);
+		if (error)
+			goto out;
+		rre = list_last_entry(&rr.rmaplist,
+				struct xfs_repair_rmapbt_extent, list);
+	}
+
+	if (rre->rmap.rm_startblock != XFS_AGFL_BLOCK(mp)) {
+		error = RMAP(FS, XFS_AGFL_BLOCK(mp), 1);
+		if (error)
+			goto out;
+	}
+
+	error = xfs_agfl_walk(sc->mp, XFS_BUF_TO_AGF(sc->sa.agf_bp),
+			sc->sa.agfl_bp, xfs_repair_rmapbt_walk_agfl, &rr);
+	if (error)
+		goto out;
+
+	/* Collect rmap for the log if it's in this AG. */
+	if (mp->m_sb.sb_logstart &&
+	    XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart) == sc->sa.agno) {
+		error = RMAP(LOG, XFS_FSB_TO_AGBNO(mp, mp->m_sb.sb_logstart),
+				mp->m_sb.sb_logblocks);
+		if (error)
+			goto out;
+	}
+
+	/* Collect rmaps for the free space btrees. */
+	rr.owner = XFS_RMAP_OWN_AG;
+	rr.btblocks = 0;
+	cur = xfs_allocbt_init_cursor(mp, sc->tp, sc->sa.agf_bp, sc->sa.agno,
+			XFS_BTNUM_BNO);
+	error = xfs_btree_visit_blocks(cur, xfs_repair_rmapbt_visit_btblock,
+			&rr);
+	if (error)
+		goto out;
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+	cur = NULL;
+
+	/* Collect rmaps for the cntbt. */
+	cur = xfs_allocbt_init_cursor(mp, sc->tp, sc->sa.agf_bp, sc->sa.agno,
+			XFS_BTNUM_CNT);
+	error = xfs_btree_visit_blocks(cur, xfs_repair_rmapbt_visit_btblock,
+			&rr);
+	if (error)
+		goto out;
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+	cur = NULL;
+	freesp_btblocks = rr.btblocks;
+
+	/* Collect rmaps for the inode btree. */
+	cur = xfs_inobt_init_cursor(mp, sc->tp, sc->sa.agi_bp, sc->sa.agno,
+			XFS_BTNUM_INO);
+	error = xfs_btree_query_all(cur, xfs_repair_rmapbt_inodes, &rr);
+	if (error)
+		goto out;
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+
+	/* If there are no inodes, we have to include the inobt root. */
+	agi = XFS_BUF_TO_AGI(sc->sa.agi_bp);
+	if (agi->agi_count == cpu_to_be32(0)) {
+		error = xfs_repair_rmapbt_new_rmap(&rr,
+				be32_to_cpu(agi->agi_root), 1,
+				XFS_RMAP_OWN_INOBT, 0, 0);
+		if (error)
+			goto out;
+	}
+
+	/* Collect rmaps for the free inode btree. */
+	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
+		rr.owner = XFS_RMAP_OWN_INOBT;
+		cur = xfs_inobt_init_cursor(mp, sc->tp, sc->sa.agi_bp,
+				sc->sa.agno, XFS_BTNUM_FINO);
+		error = xfs_btree_visit_blocks(cur,
+				xfs_repair_rmapbt_visit_btblock, &rr);
+		if (error)
+			goto out;
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+	}
+
+	/* Collect rmaps for the refcount btree. */
+	if (xfs_sb_version_hasreflink(&mp->m_sb)) {
+		union xfs_btree_irec		low;
+		union xfs_btree_irec		high;
+
+		rr.owner = XFS_RMAP_OWN_REFC;
+		cur = xfs_refcountbt_init_cursor(mp, sc->tp, sc->sa.agf_bp,
+				sc->sa.agno, NULL);
+		error = xfs_btree_visit_blocks(cur,
+				xfs_repair_rmapbt_visit_btblock, &rr);
+		if (error)
+			goto out;
+
+		/* Collect rmaps for CoW staging extents. */
+		memset(&low, 0, sizeof(low));
+		low.rc.rc_startblock = XFS_REFC_COW_START;
+		memset(&high, 0xFF, sizeof(high));
+		error = xfs_btree_query_range(cur, &low, &high,
+				xfs_repair_rmapbt_refcount, &rr);
+		if (error)
+			goto out;
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+	}
+
+	/* Iterate all AGs for inodes. */
+	for (ag = 0; ag < mp->m_sb.sb_agcount; ag++) {
+		error = xfs_ialloc_read_agi(mp, sc->tp, ag, &bp);
+		if (error)
+			goto out;
+		cur = xfs_inobt_init_cursor(mp, sc->tp, bp, ag, XFS_BTNUM_INO);
+		error = xfs_btree_query_all(cur, xfs_repair_rmapbt_scan_inobt,
+				&rr);
+		if (error)
+			goto out;
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+		xfs_trans_brelse(sc->tp, bp);
+		bp = NULL;
+	}
+
+	/* Do we actually have enough space to do this? */
+	pag = xfs_perag_get(mp, sc->sa.agno);
+	if (!xfs_repair_ag_has_space(pag,
+			xfs_rmapbt_calc_size(mp, rr.nr_records),
+			XFS_AG_RESV_AGFL)) {
+		xfs_perag_put(pag);
+		error = -ENOSPC;
+		goto out;
+	}
+
+	/* XXX: Do we need to invalidate buffers here? */
+
+	/* Initialize a new rmapbt root. */
+	xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_UNKNOWN);
+	agf = XFS_BUF_TO_AGF(sc->sa.agf_bp);
+	error = xfs_repair_alloc_ag_block(sc, &oinfo, &btfsb, XFS_AG_RESV_AGFL);
+	if (error) {
+		xfs_perag_put(pag);
+		goto out;
+	}
+	error = xfs_repair_init_btblock(sc, btfsb, &bp, XFS_BTNUM_RMAP,
+			&xfs_rmapbt_buf_ops);
+	if (error) {
+		xfs_perag_put(pag);
+		goto out;
+	}
+	agf->agf_roots[XFS_BTNUM_RMAPi] = cpu_to_be32(XFS_FSB_TO_AGBNO(mp,
+			btfsb));
+	agf->agf_levels[XFS_BTNUM_RMAPi] = cpu_to_be32(1);
+	agf->agf_rmap_blocks = cpu_to_be32(1);
+
+	/* Reset the perag info. */
+	pag->pagf_btreeblks = freesp_btblocks - 2;
+	pag->pagf_levels[XFS_BTNUM_RMAPi] =
+			be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAPi]);
+
+	/* Now reset the AGF counters. */
+	agf->agf_btreeblks = cpu_to_be32(pag->pagf_btreeblks);
+	xfs_perag_put(pag);
+	xfs_alloc_log_agf(sc->tp, sc->sa.agf_bp, XFS_AGF_ROOTS |
+			XFS_AGF_LEVELS | XFS_AGF_RMAP_BLOCKS |
+			XFS_AGF_BTREEBLKS);
+	bp = NULL;
+	error = xfs_repair_roll_ag_trans(sc);
+	if (error)
+		goto out;
+
+	/* Insert all the metadata rmaps. */
+	list_sort(NULL, &rr.rmaplist, xfs_repair_rmapbt_extent_cmp);
+	list_for_each_entry_safe(rre, n, &rr.rmaplist, list) {
+		/* Add the rmap. */
+		cur = xfs_rmapbt_init_cursor(mp, sc->tp, sc->sa.agf_bp,
+				sc->sa.agno);
+		error = xfs_rmap_map_raw(cur, &rre->rmap);
+		if (error)
+			goto out;
+		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+		cur = NULL;
+
+		error = xfs_repair_roll_ag_trans(sc);
+		if (error)
+			goto out;
+
+		list_del(&rre->list);
+		kmem_free(rre);
+
+		/*
+		 * Ensure the freelist is full, but don't let it shrink.
+		 * The rmapbt isn't fully set up yet, which means that
+		 * the current AGFL blocks might not be reflected in the
+		 * rmapbt, which is a problem if we want to unmap blocks
+		 * from the AGFL.
+		 */
+		error = xfs_repair_fix_freelist(sc, false);
+		if (error)
+			goto out;
+	}
+
+	/* Compute free space from the new rmapbt. */
+	rr.next_bno = 0;
+	cur = xfs_rmapbt_init_cursor(mp, sc->tp, sc->sa.agf_bp, sc->sa.agno);
+	error = xfs_rmap_query_all(cur, xfs_repair_rmapbt_record_rmap_freesp,
+			&rr);
+	if (error)
+		goto out;
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+	cur = NULL;
+
+	/* Insert a record for space between the last rmap and EOAG. */
+	agf = XFS_BUF_TO_AGF(sc->sa.agf_bp);
+	agend = be32_to_cpu(agf->agf_length);
+	if (rr.next_bno < agend) {
+		btfsb = XFS_AGB_TO_FSB(mp, sc->sa.agno, rr.next_bno);
+		error = xfs_repair_collect_btree_extent(sc, &rr.rmap_freelist,
+				btfsb, agend - rr.next_bno);
+		if (error)
+			goto out;
+	}
+
+	/* Compute free space from the existing bnobt. */
+	cur = xfs_allocbt_init_cursor(mp, sc->tp, sc->sa.agf_bp, sc->sa.agno,
+			XFS_BTNUM_BNO);
+	error = xfs_alloc_query_all(cur, xfs_repair_rmapbt_record_bno_freesp,
+			&rr);
+	if (error)
+		goto out;
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+	cur = NULL;
+
+	/*
+	 * Free the "free" blocks that the new rmapbt knows about but
+	 * the old bnobt doesn't.  These are the old rmapbt blocks.
+	 */
+	error = xfs_repair_subtract_extents(sc, &rr.rmap_freelist,
+			&rr.bno_freelist);
+	if (error)
+		goto out;
+	xfs_repair_cancel_btree_extents(sc, &rr.bno_freelist);
+	return xfs_repair_reap_btree_extents(sc, &rr.rmap_freelist, &oinfo,
+			XFS_AG_RESV_AGFL);
+out:
+	if (cur)
+		xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+	if (bp)
+		xfs_trans_brelse(sc->tp, bp);
+	xfs_repair_cancel_btree_extents(sc, &rr.bno_freelist);
+	xfs_repair_cancel_btree_extents(sc, &rr.rmap_freelist);
+	list_for_each_entry_safe(rre, n, &rr.rmaplist, list) {
+		list_del(&rre->list);
+		kmem_free(rre);
+	}
+	return error;
+}
+#undef RMAP
diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index 0add910..5ee2ec6 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -176,6 +176,8 @@ xfs_scrub_teardown(
 	struct xfs_inode		*ip_in,
 	int				error)
 {
+	int				err2;
+
 	xfs_scrub_ag_free(sc, &sc->sa);
 	if (sc->tp) {
 		if (error == 0 && (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
@@ -184,6 +186,12 @@ xfs_scrub_teardown(
 			xfs_trans_cancel(sc->tp);
 		sc->tp = NULL;
 	}
+	if (sc->fs_frozen) {
+		err2 = xfs_repair_fs_thaw(sc);
+		if (!error && err2)
+			error = err2;
+		sc->fs_frozen = false;
+	}
 	if (sc->ip) {
 		if (sc->ilock_flags)
 			xfs_iunlock(sc->ip, sc->ilock_flags);
@@ -263,6 +271,7 @@ static const struct xfs_scrub_meta_ops meta_scrub_ops[] = {
 		.type	= ST_PERAG,
 		.setup	= xfs_scrub_setup_ag_rmapbt,
 		.scrub	= xfs_scrub_rmapbt,
+		.repair	= xfs_repair_rmapbt,
 		.has	= xfs_sb_version_hasrmapbt,
 	},
 	[XFS_SCRUB_TYPE_REFCNTBT] = {	/* refcountbt */
@@ -539,6 +548,8 @@ xfs_scrub_metadata(
 
 	xfs_scrub_experimental_warning(mp);
 
+	atomic_inc(&mp->m_scrubbers);
+
 retry_op:
 	/* Set up for the operation. */
 	memset(&sc, 0, sizeof(sc));
@@ -561,7 +572,7 @@ xfs_scrub_metadata(
 		 */
 		error = xfs_scrub_teardown(&sc, ip, 0);
 		if (error)
-			goto out;
+			goto out_dec;
 		try_harder = true;
 		goto retry_op;
 	} else if (error)
@@ -597,7 +608,7 @@ xfs_scrub_metadata(
 			error = xfs_scrub_teardown(&sc, ip, 0);
 			if (error) {
 				xfs_repair_failure(mp);
-				goto out;
+				goto out_dec;
 			}
 			goto retry_op;
 		}
@@ -616,6 +627,8 @@ xfs_scrub_metadata(
 
 out_teardown:
 	error = xfs_scrub_teardown(&sc, ip, error);
+out_dec:
+	atomic_dec(&mp->m_scrubbers);
 out:
 	trace_xfs_scrub_done(ip, sm, error);
 	if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
diff --git a/fs/xfs/scrub/scrub.h b/fs/xfs/scrub/scrub.h
index 340d6227..4f3d6d0 100644
--- a/fs/xfs/scrub/scrub.h
+++ b/fs/xfs/scrub/scrub.h
@@ -77,6 +77,7 @@ struct xfs_scrub_context {
 	uint				ilock_flags;
 	bool				try_harder;
 	bool				reset_counters;
+	bool				fs_frozen;
 
 	/* State tracking for single-AG operations. */
 	struct xfs_scrub_ag		sa;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index d359a88..95142e9 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -206,6 +206,7 @@ typedef struct xfs_mount {
 	unsigned int		*m_errortag;
 	struct xfs_kobj		m_errortag_kobj;
 #endif
+	atomic_t		m_scrubbers;	/* # of active scrub processes */
 } xfs_mount_t;
 
 /*
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 33f0dd9..3b21ae4 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1436,6 +1436,30 @@ xfs_fs_unfreeze(
 	return 0;
 }
 
+/* Don't let userspace freeze while we're scrubbing the filesystem. */
+STATIC int
+xfs_fs_freeze_super(
+	struct super_block	*sb)
+{
+	struct xfs_mount	*mp = XFS_M(sb);
+
+	if (atomic_read(&mp->m_scrubbers) > 0)
+		return -EBUSY;
+	return freeze_super(sb);
+}
+
+/* Don't let userspace thaw while we're scrubbing the filesystem. */
+STATIC int
+xfs_fs_thaw_super(
+	struct super_block	*sb)
+{
+	struct xfs_mount	*mp = XFS_M(sb);
+
+	if (atomic_read(&mp->m_scrubbers) > 0)
+		return -EBUSY;
+	return thaw_super(sb);
+}
+
 STATIC int
 xfs_fs_show_options(
 	struct seq_file		*m,
@@ -1574,6 +1598,7 @@ xfs_fs_fill_super(
 	spin_lock_init(&mp->m_sb_lock);
 	mutex_init(&mp->m_growlock);
 	atomic_set(&mp->m_active_trans, 0);
+	atomic_set(&mp->m_scrubbers, 0);
 	INIT_DELAYED_WORK(&mp->m_reclaim_work, xfs_reclaim_worker);
 	INIT_DELAYED_WORK(&mp->m_eofblocks_work, xfs_eofblocks_worker);
 	INIT_DELAYED_WORK(&mp->m_cowblocks_work, xfs_cowblocks_worker);
@@ -1790,6 +1815,8 @@ static const struct super_operations xfs_super_operations = {
 	.show_options		= xfs_fs_show_options,
 	.nr_cached_objects	= xfs_fs_nr_cached_objects,
 	.free_cached_objects	= xfs_fs_free_cached_objects,
+	.freeze_super		= xfs_fs_freeze_super,
+	.thaw_super		= xfs_fs_thaw_super,
 };
 
 static struct file_system_type xfs_fs_type = {

