1 files changed, 767 insertions, 0 deletions

diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
new file mode 100644
index 000000000..fed56d213
--- /dev/null
+++ b/fs/xfs/scrub/bmap.c
@@ -0,0 +1,767 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#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_btree.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_inode.h"
+#include "xfs_alloc.h"
+#include "xfs_bmap.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_rmap.h"
+#include "xfs_rmap_btree.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/btree.h"
+
+/* Set us up with an inode's bmap. */
+int
+xchk_setup_inode_bmap(
+	struct xfs_scrub	*sc,
+	struct xfs_inode	*ip)
+{
+	int			error;
+
+	error = xchk_get_inode(sc, ip);
+	if (error)
+		goto out;
+
+	sc->ilock_flags = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
+	xfs_ilock(sc->ip, sc->ilock_flags);
+
+	/*
+	 * We don't want any ephemeral data fork updates sitting around
+	 * while we inspect block mappings, so wait for directio to finish
+	 * and flush dirty data if we have delalloc reservations.
+	 */
+	if (S_ISREG(VFS_I(sc->ip)->i_mode) &&
+	    sc->sm->sm_type == XFS_SCRUB_TYPE_BMBTD) {
+		struct address_space	*mapping = VFS_I(sc->ip)->i_mapping;
+
+		inode_dio_wait(VFS_I(sc->ip));
+
+		/*
+		 * Try to flush all incore state to disk before we examine the
+		 * space mappings for the data fork.  Leave accumulated errors
+		 * in the mapping for the writer threads to consume.
+		 *
+		 * On ENOSPC or EIO writeback errors, we continue into the
+		 * extent mapping checks because write failures do not
+		 * necessarily imply anything about the correctness of the file
+		 * metadata.  The metadata and the file data could be on
+		 * completely separate devices; a media failure might only
+		 * affect a subset of the disk, etc.  We can handle delalloc
+		 * extents in the scrubber, so leaving them in memory is fine.
+		 */
+		error = filemap_fdatawrite(mapping);
+		if (!error)
+			error = filemap_fdatawait_keep_errors(mapping);
+		if (error && (error != -ENOSPC && error != -EIO))
+			goto out;
+	}
+
+	/* Got the inode, lock it and we're ready to go. */
+	error = xchk_trans_alloc(sc, 0);
+	if (error)
+		goto out;
+	sc->ilock_flags |= XFS_ILOCK_EXCL;
+	xfs_ilock(sc->ip, XFS_ILOCK_EXCL);
+
+out:
+	/* scrub teardown will unlock and release the inode */
+	return error;
+}
+
+/*
+ * Inode fork block mapping (BMBT) scrubber.
+ * More complex than the others because we have to scrub
+ * all the extents regardless of whether or not the fork
+ * is in btree format.
+ */
+
+struct xchk_bmap_info {
+	struct xfs_scrub	*sc;
+	xfs_fileoff_t		lastoff;
+	bool			is_rt;
+	bool			is_shared;
+	bool			was_loaded;
+	int			whichfork;
+};
+
+/* Look for a corresponding rmap for this irec. */
+static inline bool
+xchk_bmap_get_rmap(
+	struct xchk_bmap_info	*info,
+	struct xfs_bmbt_irec	*irec,
+	xfs_agblock_t		agbno,
+	uint64_t		owner,
+	struct xfs_rmap_irec	*rmap)
+{
+	xfs_fileoff_t		offset;
+	unsigned int		rflags = 0;
+	int			has_rmap;
+	int			error;
+
+	if (info->whichfork == XFS_ATTR_FORK)
+		rflags |= XFS_RMAP_ATTR_FORK;
+	if (irec->br_state == XFS_EXT_UNWRITTEN)
+		rflags |= XFS_RMAP_UNWRITTEN;
+
+	/*
+	 * CoW staging extents are owned (on disk) by the refcountbt, so
+	 * their rmaps do not have offsets.
+	 */
+	if (info->whichfork == XFS_COW_FORK)
+		offset = 0;
+	else
+		offset = irec->br_startoff;
+
+	/*
+	 * If the caller thinks this could be a shared bmbt extent (IOWs,
+	 * any data fork extent of a reflink inode) then we have to use the
+	 * range rmap lookup to make sure we get the correct owner/offset.
+	 */
+	if (info->is_shared) {
+		error = xfs_rmap_lookup_le_range(info->sc->sa.rmap_cur, agbno,
+				owner, offset, rflags, rmap, &has_rmap);
+		if (!xchk_should_check_xref(info->sc, &error,
+				&info->sc->sa.rmap_cur))
+			return false;
+		goto out;
+	}
+
+	/*
+	 * Otherwise, use the (faster) regular lookup.
+	 */
+	error = xfs_rmap_lookup_le(info->sc->sa.rmap_cur, agbno, 0, owner,
+			offset, rflags, &has_rmap);
+	if (!xchk_should_check_xref(info->sc, &error,
+			&info->sc->sa.rmap_cur))
+		return false;
+	if (!has_rmap)
+		goto out;
+
+	error = xfs_rmap_get_rec(info->sc->sa.rmap_cur, rmap, &has_rmap);
+	if (!xchk_should_check_xref(info->sc, &error,
+			&info->sc->sa.rmap_cur))
+		return false;
+
+out:
+	if (!has_rmap)
+		xchk_fblock_xref_set_corrupt(info->sc, info->whichfork,
+			irec->br_startoff);
+	return has_rmap;
+}
+
+/* Make sure that we have rmapbt records for this extent. */
+STATIC void
+xchk_bmap_xref_rmap(
+	struct xchk_bmap_info	*info,
+	struct xfs_bmbt_irec	*irec,
+	xfs_agblock_t		agbno)
+{
+	struct xfs_rmap_irec	rmap;
+	unsigned long long	rmap_end;
+	uint64_t		owner;
+
+	if (!info->sc->sa.rmap_cur || xchk_skip_xref(info->sc->sm))
+		return;
+
+	if (info->whichfork == XFS_COW_FORK)
+		owner = XFS_RMAP_OWN_COW;
+	else
+		owner = info->sc->ip->i_ino;
+
+	/* Find the rmap record for this irec. */
+	if (!xchk_bmap_get_rmap(info, irec, agbno, owner, &rmap))
+		return;
+
+	/* Check the rmap. */
+	rmap_end = (unsigned long long)rmap.rm_startblock + rmap.rm_blockcount;
+	if (rmap.rm_startblock > agbno ||
+	    agbno + irec->br_blockcount > rmap_end)
+		xchk_fblock_xref_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	/*
+	 * Check the logical offsets if applicable.  CoW staging extents
+	 * don't track logical offsets since the mappings only exist in
+	 * memory.
+	 */
+	if (info->whichfork != XFS_COW_FORK) {
+		rmap_end = (unsigned long long)rmap.rm_offset +
+				rmap.rm_blockcount;
+		if (rmap.rm_offset > irec->br_startoff ||
+		    irec->br_startoff + irec->br_blockcount > rmap_end)
+			xchk_fblock_xref_set_corrupt(info->sc,
+					info->whichfork, irec->br_startoff);
+	}
+
+	if (rmap.rm_owner != owner)
+		xchk_fblock_xref_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	/*
+	 * Check for discrepancies between the unwritten flag in the irec and
+	 * the rmap.  Note that the (in-memory) CoW fork distinguishes between
+	 * unwritten and written extents, but we don't track that in the rmap
+	 * records because the blocks are owned (on-disk) by the refcountbt,
+	 * which doesn't track unwritten state.
+	 */
+	if (owner != XFS_RMAP_OWN_COW &&
+	    !!(irec->br_state == XFS_EXT_UNWRITTEN) !=
+	    !!(rmap.rm_flags & XFS_RMAP_UNWRITTEN))
+		xchk_fblock_xref_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	if (!!(info->whichfork == XFS_ATTR_FORK) !=
+	    !!(rmap.rm_flags & XFS_RMAP_ATTR_FORK))
+		xchk_fblock_xref_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+	if (rmap.rm_flags & XFS_RMAP_BMBT_BLOCK)
+		xchk_fblock_xref_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+}
+
+/* Cross-reference a single rtdev extent record. */
+STATIC void
+xchk_bmap_rt_iextent_xref(
+	struct xfs_inode	*ip,
+	struct xchk_bmap_info	*info,
+	struct xfs_bmbt_irec	*irec)
+{
+	xchk_xref_is_used_rt_space(info->sc, irec->br_startblock,
+			irec->br_blockcount);
+}
+
+/* Cross-reference a single datadev extent record. */
+STATIC void
+xchk_bmap_iextent_xref(
+	struct xfs_inode	*ip,
+	struct xchk_bmap_info	*info,
+	struct xfs_bmbt_irec	*irec)
+{
+	struct xfs_mount	*mp = info->sc->mp;
+	xfs_agnumber_t		agno;
+	xfs_agblock_t		agbno;
+	xfs_extlen_t		len;
+	int			error;
+
+	agno = XFS_FSB_TO_AGNO(mp, irec->br_startblock);
+	agbno = XFS_FSB_TO_AGBNO(mp, irec->br_startblock);
+	len = irec->br_blockcount;
+
+	error = xchk_ag_init(info->sc, agno, &info->sc->sa);
+	if (!xchk_fblock_process_error(info->sc, info->whichfork,
+			irec->br_startoff, &error))
+		return;
+
+	xchk_xref_is_used_space(info->sc, agbno, len);
+	xchk_xref_is_not_inode_chunk(info->sc, agbno, len);
+	xchk_bmap_xref_rmap(info, irec, agbno);
+	switch (info->whichfork) {
+	case XFS_DATA_FORK:
+		if (xfs_is_reflink_inode(info->sc->ip))
+			break;
+		/* fall through */
+	case XFS_ATTR_FORK:
+		xchk_xref_is_not_shared(info->sc, agbno,
+				irec->br_blockcount);
+		break;
+	case XFS_COW_FORK:
+		xchk_xref_is_cow_staging(info->sc, agbno,
+				irec->br_blockcount);
+		break;
+	}
+
+	xchk_ag_free(info->sc, &info->sc->sa);
+}
+
+/*
+ * Directories and attr forks should never have blocks that can't be addressed
+ * by a xfs_dablk_t.
+ */
+STATIC void
+xchk_bmap_dirattr_extent(
+	struct xfs_inode	*ip,
+	struct xchk_bmap_info	*info,
+	struct xfs_bmbt_irec	*irec)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	xfs_fileoff_t		off;
+
+	if (!S_ISDIR(VFS_I(ip)->i_mode) && info->whichfork != XFS_ATTR_FORK)
+		return;
+
+	if (!xfs_verify_dablk(mp, irec->br_startoff))
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	off = irec->br_startoff + irec->br_blockcount - 1;
+	if (!xfs_verify_dablk(mp, off))
+		xchk_fblock_set_corrupt(info->sc, info->whichfork, off);
+}
+
+/* Scrub a single extent record. */
+STATIC int
+xchk_bmap_iextent(
+	struct xfs_inode	*ip,
+	struct xchk_bmap_info	*info,
+	struct xfs_bmbt_irec	*irec)
+{
+	struct xfs_mount	*mp = info->sc->mp;
+	xfs_filblks_t		end;
+	int			error = 0;
+
+	/*
+	 * Check for out-of-order extents.  This record could have come
+	 * from the incore list, for which there is no ordering check.
+	 */
+	if (irec->br_startoff < info->lastoff)
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	xchk_bmap_dirattr_extent(ip, info, irec);
+
+	/* There should never be a "hole" extent in either extent list. */
+	if (irec->br_startblock == HOLESTARTBLOCK)
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	/*
+	 * Check for delalloc extents.  We never iterate the ones in the
+	 * in-core extent scan, and we should never see these in the bmbt.
+	 */
+	if (isnullstartblock(irec->br_startblock))
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	/* Make sure the extent points to a valid place. */
+	if (irec->br_blockcount > MAXEXTLEN)
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+	if (irec->br_startblock + irec->br_blockcount <= irec->br_startblock)
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+	end = irec->br_startblock + irec->br_blockcount - 1;
+	if (info->is_rt &&
+	    (!xfs_verify_rtbno(mp, irec->br_startblock) ||
+	     !xfs_verify_rtbno(mp, end)))
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+	if (!info->is_rt &&
+	    (!xfs_verify_fsbno(mp, irec->br_startblock) ||
+	     !xfs_verify_fsbno(mp, end) ||
+	     XFS_FSB_TO_AGNO(mp, irec->br_startblock) !=
+				XFS_FSB_TO_AGNO(mp, end)))
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	/* We don't allow unwritten extents on attr forks. */
+	if (irec->br_state == XFS_EXT_UNWRITTEN &&
+	    info->whichfork == XFS_ATTR_FORK)
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
+	if (info->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+		return 0;
+
+	if (info->is_rt)
+		xchk_bmap_rt_iextent_xref(ip, info, irec);
+	else
+		xchk_bmap_iextent_xref(ip, info, irec);
+
+	info->lastoff = irec->br_startoff + irec->br_blockcount;
+	return error;
+}
+
+/* Scrub a bmbt record. */
+STATIC int
+xchk_bmapbt_rec(
+	struct xchk_btree	*bs,
+	union xfs_btree_rec	*rec)
+{
+	struct xfs_bmbt_irec	irec;
+	struct xfs_bmbt_irec	iext_irec;
+	struct xfs_iext_cursor	icur;
+	struct xchk_bmap_info	*info = bs->private;
+	struct xfs_inode	*ip = bs->cur->bc_ino.ip;
+	struct xfs_buf		*bp = NULL;
+	struct xfs_btree_block	*block;
+	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, info->whichfork);
+	uint64_t		owner;
+	int			i;
+
+	/*
+	 * Check the owners of the btree blocks up to the level below
+	 * the root since the verifiers don't do that.
+	 */
+	if (xfs_sb_version_hascrc(&bs->cur->bc_mp->m_sb) &&
+	    bs->cur->bc_ptrs[0] == 1) {
+		for (i = 0; i < bs->cur->bc_nlevels - 1; i++) {
+			block = xfs_btree_get_block(bs->cur, i, &bp);
+			owner = be64_to_cpu(block->bb_u.l.bb_owner);
+			if (owner != ip->i_ino)
+				xchk_fblock_set_corrupt(bs->sc,
+						info->whichfork, 0);
+		}
+	}
+
+	/*
+	 * Check that the incore extent tree contains an extent that matches
+	 * this one exactly.  We validate those cached bmaps later, so we don't
+	 * need to check them here.  If the incore extent tree was just loaded
+	 * from disk by the scrubber, we assume that its contents match what's
+	 * on disk (we still hold the ILOCK) and skip the equivalence check.
+	 */
+	if (!info->was_loaded)
+		return 0;
+
+	xfs_bmbt_disk_get_all(&rec->bmbt, &irec);
+	if (!xfs_iext_lookup_extent(ip, ifp, irec.br_startoff, &icur,
+				&iext_irec) ||
+	    irec.br_startoff != iext_irec.br_startoff ||
+	    irec.br_startblock != iext_irec.br_startblock ||
+	    irec.br_blockcount != iext_irec.br_blockcount ||
+	    irec.br_state != iext_irec.br_state)
+		xchk_fblock_set_corrupt(bs->sc, info->whichfork,
+				irec.br_startoff);
+	return 0;
+}
+
+/* Scan the btree records. */
+STATIC int
+xchk_bmap_btree(
+	struct xfs_scrub	*sc,
+	int			whichfork,
+	struct xchk_bmap_info	*info)
+{
+	struct xfs_owner_info	oinfo;
+	struct xfs_ifork	*ifp = XFS_IFORK_PTR(sc->ip, whichfork);
+	struct xfs_mount	*mp = sc->mp;
+	struct xfs_inode	*ip = sc->ip;
+	struct xfs_btree_cur	*cur;
+	int			error;
+
+	/* Load the incore bmap cache if it's not loaded. */
+	info->was_loaded = ifp->if_flags & XFS_IFEXTENTS;
+	if (!info->was_loaded) {
+		error = xfs_iread_extents(sc->tp, ip, whichfork);
+		if (!xchk_fblock_process_error(sc, whichfork, 0, &error))
+			goto out;
+	}
+
+	/* Check the btree structure. */
+	cur = xfs_bmbt_init_cursor(mp, sc->tp, ip, whichfork);
+	xfs_rmap_ino_bmbt_owner(&oinfo, ip->i_ino, whichfork);
+	error = xchk_btree(sc, cur, xchk_bmapbt_rec, &oinfo, info);
+	xfs_btree_del_cursor(cur, error);
+out:
+	return error;
+}
+
+struct xchk_bmap_check_rmap_info {
+	struct xfs_scrub	*sc;
+	int			whichfork;
+	struct xfs_iext_cursor	icur;
+};
+
+/* Can we find bmaps that fit this rmap? */
+STATIC int
+xchk_bmap_check_rmap(
+	struct xfs_btree_cur		*cur,
+	struct xfs_rmap_irec		*rec,
+	void				*priv)
+{
+	struct xfs_bmbt_irec		irec;
+	struct xchk_bmap_check_rmap_info	*sbcri = priv;
+	struct xfs_ifork		*ifp;
+	struct xfs_scrub		*sc = sbcri->sc;
+	bool				have_map;
+
+	/* Is this even the right fork? */
+	if (rec->rm_owner != sc->ip->i_ino)
+		return 0;
+	if ((sbcri->whichfork == XFS_ATTR_FORK) ^
+	    !!(rec->rm_flags & XFS_RMAP_ATTR_FORK))
+		return 0;
+	if (rec->rm_flags & XFS_RMAP_BMBT_BLOCK)
+		return 0;
+
+	/* Now look up the bmbt record. */
+	ifp = XFS_IFORK_PTR(sc->ip, sbcri->whichfork);
+	if (!ifp) {
+		xchk_fblock_set_corrupt(sc, sbcri->whichfork,
+				rec->rm_offset);
+		goto out;
+	}
+	have_map = xfs_iext_lookup_extent(sc->ip, ifp, rec->rm_offset,
+			&sbcri->icur, &irec);
+	if (!have_map)
+		xchk_fblock_set_corrupt(sc, sbcri->whichfork,
+				rec->rm_offset);
+	/*
+	 * bmap extent record lengths are constrained to 2^21 blocks in length
+	 * because of space constraints in the on-disk metadata structure.
+	 * However, rmap extent record lengths are constrained only by AG
+	 * length, so we have to loop through the bmbt to make sure that the
+	 * entire rmap is covered by bmbt records.
+	 */
+	while (have_map) {
+		if (irec.br_startoff != rec->rm_offset)
+			xchk_fblock_set_corrupt(sc, sbcri->whichfork,
+					rec->rm_offset);
+		if (irec.br_startblock != XFS_AGB_TO_FSB(sc->mp,
+				cur->bc_ag.agno, rec->rm_startblock))
+			xchk_fblock_set_corrupt(sc, sbcri->whichfork,
+					rec->rm_offset);
+		if (irec.br_blockcount > rec->rm_blockcount)
+			xchk_fblock_set_corrupt(sc, sbcri->whichfork,
+					rec->rm_offset);
+		if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+			break;
+		rec->rm_startblock += irec.br_blockcount;
+		rec->rm_offset += irec.br_blockcount;
+		rec->rm_blockcount -= irec.br_blockcount;
+		if (rec->rm_blockcount == 0)
+			break;
+		have_map = xfs_iext_next_extent(ifp, &sbcri->icur, &irec);
+		if (!have_map)
+			xchk_fblock_set_corrupt(sc, sbcri->whichfork,
+					rec->rm_offset);
+	}
+
+out:
+	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+		return -ECANCELED;
+	return 0;
+}
+
+/* Make sure each rmap has a corresponding bmbt entry. */
+STATIC int
+xchk_bmap_check_ag_rmaps(
+	struct xfs_scrub		*sc,
+	int				whichfork,
+	xfs_agnumber_t			agno)
+{
+	struct xchk_bmap_check_rmap_info	sbcri;
+	struct xfs_btree_cur		*cur;
+	struct xfs_buf			*agf;
+	int				error;
+
+	error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf);
+	if (error)
+		return error;
+
+	cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf, agno);
+	if (!cur) {
+		error = -ENOMEM;
+		goto out_agf;
+	}
+
+	sbcri.sc = sc;
+	sbcri.whichfork = whichfork;
+	error = xfs_rmap_query_all(cur, xchk_bmap_check_rmap, &sbcri);
+	if (error == -ECANCELED)
+		error = 0;
+
+	xfs_btree_del_cursor(cur, error);
+out_agf:
+	xfs_trans_brelse(sc->tp, agf);
+	return error;
+}
+
+/* Make sure each rmap has a corresponding bmbt entry. */
+STATIC int
+xchk_bmap_check_rmaps(
+	struct xfs_scrub	*sc,
+	int			whichfork)
+{
+	struct xfs_ifork	*ifp = XFS_IFORK_PTR(sc->ip, whichfork);
+	xfs_agnumber_t		agno;
+	bool			zero_size;
+	int			error;
+
+	if (!xfs_sb_version_hasrmapbt(&sc->mp->m_sb) ||
+	    whichfork == XFS_COW_FORK ||
+	    (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
+		return 0;
+
+	/* Don't support realtime rmap checks yet. */
+	if (XFS_IS_REALTIME_INODE(sc->ip) && whichfork == XFS_DATA_FORK)
+		return 0;
+
+	ASSERT(XFS_IFORK_PTR(sc->ip, whichfork) != NULL);
+
+	/*
+	 * Only do this for complex maps that are in btree format, or for
+	 * situations where we would seem to have a size but zero extents.
+	 * The inode repair code can zap broken iforks, which means we have
+	 * to flag this bmap as corrupt if there are rmaps that need to be
+	 * reattached.
+	 */
+
+	if (whichfork == XFS_DATA_FORK)
+		zero_size = i_size_read(VFS_I(sc->ip)) == 0;
+	else
+		zero_size = false;
+
+	if (ifp->if_format != XFS_DINODE_FMT_BTREE &&
+	    (zero_size || ifp->if_nextents > 0))
+		return 0;
+
+	for (agno = 0; agno < sc->mp->m_sb.sb_agcount; agno++) {
+		error = xchk_bmap_check_ag_rmaps(sc, whichfork, agno);
+		if (error)
+			return error;
+		if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+			break;
+	}
+
+	return 0;
+}
+
+/*
+ * Scrub an inode fork's block mappings.
+ *
+ * First we scan every record in every btree block, if applicable.
+ * Then we unconditionally scan the incore extent cache.
+ */
+STATIC int
+xchk_bmap(
+	struct xfs_scrub	*sc,
+	int			whichfork)
+{
+	struct xfs_bmbt_irec	irec;
+	struct xchk_bmap_info	info = { NULL };
+	struct xfs_mount	*mp = sc->mp;
+	struct xfs_inode	*ip = sc->ip;
+	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, whichfork);
+	xfs_fileoff_t		endoff;
+	struct xfs_iext_cursor	icur;
+	int			error = 0;
+
+	/* Non-existent forks can be ignored. */
+	if (!ifp)
+		goto out;
+
+	info.is_rt = whichfork == XFS_DATA_FORK && XFS_IS_REALTIME_INODE(ip);
+	info.whichfork = whichfork;
+	info.is_shared = whichfork == XFS_DATA_FORK && xfs_is_reflink_inode(ip);
+	info.sc = sc;
+
+	switch (whichfork) {
+	case XFS_COW_FORK:
+		/* No CoW forks on non-reflink inodes/filesystems. */
+		if (!xfs_is_reflink_inode(ip)) {
+			xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+			goto out;
+		}
+		break;
+	case XFS_ATTR_FORK:
+		if (!xfs_sb_version_hasattr(&mp->m_sb) &&
+		    !xfs_sb_version_hasattr2(&mp->m_sb))
+			xchk_ino_set_corrupt(sc, sc->ip->i_ino);
+		break;
+	default:
+		ASSERT(whichfork == XFS_DATA_FORK);
+		break;
+	}
+
+	/* Check the fork values */
+	switch (ifp->if_format) {
+	case XFS_DINODE_FMT_UUID:
+	case XFS_DINODE_FMT_DEV:
+	case XFS_DINODE_FMT_LOCAL:
+		/* No mappings to check. */
+		goto out;
+	case XFS_DINODE_FMT_EXTENTS:
+		if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+			xchk_fblock_set_corrupt(sc, whichfork, 0);
+			goto out;
+		}
+		break;
+	case XFS_DINODE_FMT_BTREE:
+		if (whichfork == XFS_COW_FORK) {
+			xchk_fblock_set_corrupt(sc, whichfork, 0);
+			goto out;
+		}
+
+		error = xchk_bmap_btree(sc, whichfork, &info);
+		if (error)
+			goto out;
+		break;
+	default:
+		xchk_fblock_set_corrupt(sc, whichfork, 0);
+		goto out;
+	}
+
+	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+		goto out;
+
+	/* Find the offset of the last extent in the mapping. */
+	error = xfs_bmap_last_offset(ip, &endoff, whichfork);
+	if (!xchk_fblock_process_error(sc, whichfork, 0, &error))
+		goto out;
+
+	/* Scrub extent records. */
+	info.lastoff = 0;
+	ifp = XFS_IFORK_PTR(ip, whichfork);
+	for_each_xfs_iext(ifp, &icur, &irec) {
+		if (xchk_should_terminate(sc, &error) ||
+		    (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
+			goto out;
+		if (isnullstartblock(irec.br_startblock))
+			continue;
+		if (irec.br_startoff >= endoff) {
+			xchk_fblock_set_corrupt(sc, whichfork,
+					irec.br_startoff);
+			goto out;
+		}
+		error = xchk_bmap_iextent(ip, &info, &irec);
+		if (error)
+			goto out;
+	}
+
+	error = xchk_bmap_check_rmaps(sc, whichfork);
+	if (!xchk_fblock_xref_process_error(sc, whichfork, 0, &error))
+		goto out;
+out:
+	return error;
+}
+
+/* Scrub an inode's data fork. */
+int
+xchk_bmap_data(
+	struct xfs_scrub	*sc)
+{
+	return xchk_bmap(sc, XFS_DATA_FORK);
+}
+
+/* Scrub an inode's attr fork. */
+int
+xchk_bmap_attr(
+	struct xfs_scrub	*sc)
+{
+	return xchk_bmap(sc, XFS_ATTR_FORK);
+}
+
+/* Scrub an inode's CoW fork. */
+int
+xchk_bmap_cow(
+	struct xfs_scrub	*sc)
+{
+	if (!xfs_is_reflink_inode(sc->ip))
+		return -ENOENT;
+
+	return xchk_bmap(sc, XFS_COW_FORK);
+}