xfs: clean up the inode cluster checking in the inobt scrub

The code to check inobt records against inode clusters is a mess of
poorly named variables and unnecessary parameters.  Clean the
unnecessary inode number parameters out of _check_cluster_freemask in
favor of computing them inside the function instead of making the caller
do it.  In xchk_iallocbt_check_cluster, rename the variables to make it
more obvious just what chunk_ino and cluster_ino represent.

Add a tracepoint to make it easier to track each inode cluster as we
scrub it.

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

2 files changed, 152 insertions, 58 deletions

diff --git a/fs/xfs/scrub/ialloc.c b/fs/xfs/scrub/ialloc.c
index 0ce793d92995..708f6607db71 100644
--- a/fs/xfs/scrub/ialloc.c
+++ b/fs/xfs/scrub/ialloc.c
@@ -134,41 +134,69 @@ xchk_iallocbt_freecount(
 	return hweight64(freemask);
 }
 
-/* Check a particular inode with ir_free. */
+/*
+ * Check that an inode's allocation status matches ir_free in the inobt
+ * record.  First we try querying the in-core inode state, and if the inode
+ * isn't loaded we examine the on-disk inode directly.
+ *
+ * Since there can be 1:M and M:1 mappings between inobt records and inode
+ * clusters, we pass in the inode location information as an inobt record;
+ * the index of an inode cluster within the inobt record (as well as the
+ * cluster buffer itself); and the index of the inode within the cluster.
+ *
+ * @irec is the inobt record.
+ * @cluster_base is the inode offset of the cluster within the @irec.
+ * @cluster_bp is the cluster buffer.
+ * @cluster_index is the inode offset within the inode cluster.
+ */
 STATIC int
-xchk_iallocbt_check_cluster_freemask(
+xchk_iallocbt_check_cluster_ifree(
 	struct xchk_btree		*bs,
-	xfs_ino_t			fsino,
-	xfs_agino_t			chunkino,
-	xfs_agino_t			clusterino,
 	struct xfs_inobt_rec_incore	*irec,
-	struct xfs_buf			*bp)
+	unsigned int			cluster_base,
+	struct xfs_buf			*cluster_bp,
+	unsigned int			cluster_index)
 {
-	struct xfs_dinode		*dip;
 	struct xfs_mount		*mp = bs->cur->bc_mp;
-	bool				inode_is_free = false;
+	struct xfs_dinode		*dip;
+	xfs_ino_t			fsino;
+	xfs_agino_t			agino;
+	unsigned int			offset;
+	bool				irec_free;
+	bool				ino_inuse;
 	bool				freemask_ok;
-	bool				inuse;
-	int				error = 0;
+	int				error;
 
 	if (xchk_should_terminate(bs->sc, &error))
 		return error;
 
-	dip = xfs_buf_offset(bp, clusterino * mp->m_sb.sb_inodesize);
+	/*
+	 * Given an inobt record, an offset of a cluster within the record, and
+	 * an offset of an inode within a cluster, compute which fs inode we're
+	 * talking about and the offset of that inode within the buffer.
+	 */
+	agino = irec->ir_startino + cluster_base + cluster_index;
+	fsino = XFS_AGINO_TO_INO(mp, bs->cur->bc_private.a.agno, agino);
+	offset = cluster_index * mp->m_sb.sb_inodesize;
+	if (offset >= BBTOB(cluster_bp->b_length)) {
+		xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
+		goto out;
+	}
+	dip = xfs_buf_offset(cluster_bp, offset);
+	irec_free = (irec->ir_free & XFS_INOBT_MASK(cluster_base +
+						    cluster_index));
+
 	if (be16_to_cpu(dip->di_magic) != XFS_DINODE_MAGIC ||
-	    (dip->di_version >= 3 &&
-	     be64_to_cpu(dip->di_ino) != fsino + clusterino)) {
+	    (dip->di_version >= 3 && be64_to_cpu(dip->di_ino) != fsino)) {
 		xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
 		goto out;
 	}
 
-	if (irec->ir_free & XFS_INOBT_MASK(chunkino + clusterino))
-		inode_is_free = true;
-	error = xfs_icache_inode_is_allocated(mp, bs->cur->bc_tp,
-			fsino + clusterino, &inuse);
+	error = xfs_icache_inode_is_allocated(mp, bs->cur->bc_tp, fsino,
+			&ino_inuse);
 	if (error == -ENODATA) {
 		/* Not cached, just read the disk buffer */
-		freemask_ok = inode_is_free ^ !!(dip->di_mode);
+		freemask_ok = irec_free ^ !!(dip->di_mode);
 		if (!bs->sc->try_harder && !freemask_ok)
 			return -EDEADLOCK;
 	} else if (error < 0) {
@@ -180,7 +208,7 @@ xchk_iallocbt_check_cluster_freemask(
 		goto out;
 	} else {
 		/* Inode is all there. */
-		freemask_ok = inode_is_free ^ inuse;
+		freemask_ok = irec_free ^ ino_inuse;
 	}
 	if (!freemask_ok)
 		xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
@@ -188,43 +216,57 @@ out:
 	return 0;
 }
 
-/* Check an inode cluster. */
+/*
+ * Check that the holemask and freemask of a hypothetical inode cluster match
+ * what's actually on disk.  If sparse inodes are enabled, the cluster does
+ * not actually have to map to inodes if the corresponding holemask bit is set.
+ *
+ * @cluster_base is the first inode in the cluster within the @irec.
+ */
 STATIC int
 xchk_iallocbt_check_cluster(
 	struct xchk_btree		*bs,
 	struct xfs_inobt_rec_incore	*irec,
-	xfs_agino_t			agino)
+	unsigned int			cluster_base)
 {
 	struct xfs_imap			imap;
 	struct xfs_mount		*mp = bs->cur->bc_mp;
 	struct xfs_dinode		*dip;
-	struct xfs_buf			*bp;
-	xfs_ino_t			fsino;
+	struct xfs_buf			*cluster_bp;
 	unsigned int			nr_inodes;
-	xfs_agino_t			chunkino;
-	xfs_agino_t			clusterino;
+	xfs_agnumber_t			agno = bs->cur->bc_private.a.agno;
 	xfs_agblock_t			agbno;
-	uint16_t			holemask;
+	unsigned int			cluster_index;
+	uint16_t			cluster_mask = 0;
 	uint16_t			ir_holemask;
 	int				error = 0;
 
-	/* Make sure the freemask matches the inode records. */
 	nr_inodes = min_t(unsigned int, XFS_INODES_PER_CHUNK,
 			mp->m_inodes_per_cluster);
 
-	fsino = XFS_AGINO_TO_INO(mp, bs->cur->bc_private.a.agno, agino);
-	chunkino = agino - irec->ir_startino;
-	agbno = XFS_AGINO_TO_AGBNO(mp, agino);
+	/* Map this inode cluster */
+	agbno = XFS_AGINO_TO_AGBNO(mp, irec->ir_startino + cluster_base);
 
-	/* Compute the holemask mask for this cluster. */
-	for (clusterino = 0, holemask = 0; clusterino < nr_inodes;
-	     clusterino += XFS_INODES_PER_HOLEMASK_BIT)
-		holemask |= XFS_INOBT_MASK((chunkino + clusterino) /
+	/* Compute a bitmask for this cluster that can be used for holemask. */
+	for (cluster_index = 0;
+	     cluster_index < nr_inodes;
+	     cluster_index += XFS_INODES_PER_HOLEMASK_BIT)
+		cluster_mask |= XFS_INOBT_MASK((cluster_base + cluster_index) /
 				XFS_INODES_PER_HOLEMASK_BIT);
 
+	ir_holemask = (irec->ir_holemask & cluster_mask);
+	imap.im_blkno = XFS_AGB_TO_DADDR(mp, agno, agbno);
+	imap.im_len = XFS_FSB_TO_BB(mp, mp->m_blocks_per_cluster);
+	imap.im_boffset = 0;
+
+	trace_xchk_iallocbt_check_cluster(mp, agno, irec->ir_startino,
+			imap.im_blkno, imap.im_len, cluster_base, nr_inodes,
+			cluster_mask, ir_holemask,
+			XFS_INO_TO_OFFSET(mp, irec->ir_startino +
+					  cluster_base));
+
 	/* The whole cluster must be a hole or not a hole. */
-	ir_holemask = (irec->ir_holemask & holemask);
-	if (ir_holemask != holemask && ir_holemask != 0) {
+	if (ir_holemask != cluster_mask && ir_holemask != 0) {
 		xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
 		return 0;
 	}
@@ -241,40 +283,47 @@ xchk_iallocbt_check_cluster(
 			&XFS_RMAP_OINFO_INODES);
 
 	/* Grab the inode cluster buffer. */
-	imap.im_blkno = XFS_AGB_TO_DADDR(mp, bs->cur->bc_private.a.agno, agbno);
-	imap.im_len = XFS_FSB_TO_BB(mp, mp->m_blocks_per_cluster);
-	imap.im_boffset = 0;
-
-	error = xfs_imap_to_bp(mp, bs->cur->bc_tp, &imap, &dip, &bp, 0, 0);
+	error = xfs_imap_to_bp(mp, bs->cur->bc_tp, &imap, &dip, &cluster_bp,
+			0, 0);
 	if (!xchk_btree_xref_process_error(bs->sc, bs->cur, 0, &error))
-		return 0;
+		return error;
 
-	/* Which inodes are free? */
-	for (clusterino = 0; clusterino < nr_inodes; clusterino++) {
-		error = xchk_iallocbt_check_cluster_freemask(bs, fsino,
-				chunkino, clusterino, irec, bp);
+	/* Check free status of each inode within this cluster. */
+	for (cluster_index = 0; cluster_index < nr_inodes; cluster_index++) {
+		error = xchk_iallocbt_check_cluster_ifree(bs, irec,
+				cluster_base, cluster_bp, cluster_index);
 		if (error)
 			break;
 	}
 
-	xfs_trans_brelse(bs->cur->bc_tp, bp);
+	xfs_trans_brelse(bs->cur->bc_tp, cluster_bp);
 	return error;
 }
 
-/* Make sure the free mask is consistent with what the inodes think. */
+/*
+ * For all the inode clusters that could map to this inobt record, make sure
+ * that the holemask makes sense and that the allocation status of each inode
+ * matches the freemask.
+ */
 STATIC int
-xchk_iallocbt_check_freemask(
+xchk_iallocbt_check_clusters(
 	struct xchk_btree		*bs,
 	struct xfs_inobt_rec_incore	*irec)
 {
-	struct xfs_mount		*mp = bs->cur->bc_mp;
-	xfs_agino_t			agino;
+	unsigned int			cluster_base;
 	int				error = 0;
 
-	for (agino = irec->ir_startino;
-	     agino < irec->ir_startino + XFS_INODES_PER_CHUNK;
-	     agino += mp->m_inodes_per_cluster) {
-		error = xchk_iallocbt_check_cluster(bs, irec, agino);
+	/*
+	 * For the common case where this inobt record maps to multiple inode
+	 * clusters this will call _check_cluster for each cluster.
+	 *
+	 * For the case that multiple inobt records map to a single cluster,
+	 * this will call _check_cluster once.
+	 */
+	for (cluster_base = 0;
+	     cluster_base < XFS_INODES_PER_CHUNK;
+	     cluster_base += bs->sc->mp->m_inodes_per_cluster) {
+		error = xchk_iallocbt_check_cluster(bs, irec, cluster_base);
 		if (error)
 			break;
 	}
@@ -415,7 +464,7 @@ xchk_iallocbt_rec(
 
 		if (!xchk_iallocbt_chunk(bs, &irec, agino, len))
 			goto out;
-		goto check_freemask;
+		goto check_clusters;
 	}
 
 	/* Check each chunk of a sparse inode cluster. */
@@ -441,8 +490,8 @@ xchk_iallocbt_rec(
 	    holecount + irec.ir_count != XFS_INODES_PER_CHUNK)
 		xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
 
-check_freemask:
-	error = xchk_iallocbt_check_freemask(bs, &irec);
+check_clusters:
+	error = xchk_iallocbt_check_clusters(bs, &irec);
 	if (error)
 		goto out;
 
diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 8344b14031ef..3c83e8b3b39c 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -545,6 +545,51 @@ TRACE_EVENT(xchk_xref_error,
 		  __entry->ret_ip)
 );
 
+TRACE_EVENT(xchk_iallocbt_check_cluster,
+	TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno,
+		 xfs_agino_t startino, xfs_daddr_t map_daddr,
+		 unsigned short map_len, unsigned int chunk_ino,
+		 unsigned int nr_inodes, uint16_t cluster_mask,
+		 uint16_t holemask, unsigned int cluster_ino),
+	TP_ARGS(mp, agno, startino, map_daddr, map_len, chunk_ino, nr_inodes,
+		cluster_mask, holemask, cluster_ino),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(xfs_agnumber_t, agno)
+		__field(xfs_agino_t, startino)
+		__field(xfs_daddr_t, map_daddr)
+		__field(unsigned short, map_len)
+		__field(unsigned int, chunk_ino)
+		__field(unsigned int, nr_inodes)
+		__field(unsigned int, cluster_ino)
+		__field(uint16_t, cluster_mask)
+		__field(uint16_t, holemask)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->agno = agno;
+		__entry->startino = startino;
+		__entry->map_daddr = map_daddr;
+		__entry->map_len = map_len;
+		__entry->chunk_ino = chunk_ino;
+		__entry->nr_inodes = nr_inodes;
+		__entry->cluster_mask = cluster_mask;
+		__entry->holemask = holemask;
+		__entry->cluster_ino = cluster_ino;
+	),
+	TP_printk("dev %d:%d agno %d startino %u daddr 0x%llx len %d chunkino %u nr_inodes %u cluster_mask 0x%x holemask 0x%x cluster_ino %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->agno,
+		  __entry->startino,
+		  __entry->map_daddr,
+		  __entry->map_len,
+		  __entry->chunk_ino,
+		  __entry->nr_inodes,
+		  __entry->cluster_mask,
+		  __entry->holemask,
+		  __entry->cluster_ino)
+)
+
 /* repair tracepoints */
 #if IS_ENABLED(CONFIG_XFS_ONLINE_REPAIR)