xfs: add CRC checking to dir2 free blocks

This addition follows the same pattern as the dir2 block CRCs, but
with a few differences. The main difference is that the free block
header is different between the v2 and v3 formats, so an "in-core"
free block header has been added and _todisk/_from_disk functions
used to abstract the differences in structure format from the code.
This is similar to the on-disk superblock versus the in-core
superblock setup. The in-core strucutre is populated when the buffer
is read from disk, all the in memory checks and modifications are
done on the in-core version of the structure which is written back
to the buffer before the buffer is logged.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_dir2_format.h

@@ -66,6 +66,7 @@
 
 #define	XFS_DIR3_BLOCK_MAGIC	0x58444233	/* XDB3: single block dirs */
 #define	XFS_DIR3_DATA_MAGIC	0x58444433	/* XDD3: multiblock dirs */
+#define	XFS_DIR3_FREE_MAGIC	0x58444633	/* XDF3: free index blocks */
 
 /*
  * Byte offset in data block and shortform entry.
@@ -663,19 +664,65 @@ typedef struct xfs_dir2_free {
 						/* unused entries are -1 */
 } xfs_dir2_free_t;
 
-static inline int xfs_dir2_free_max_bests(struct xfs_mount *mp)
+struct xfs_dir3_free_hdr {
+	struct xfs_dir3_blk_hdr	hdr;
+	__be32			firstdb;	/* db of first entry */
+	__be32			nvalid;		/* count of valid entries */
+	__be32			nused;		/* count of used entries */
+};
+
+struct xfs_dir3_free {
+	struct xfs_dir3_free_hdr hdr;
+	__be16			bests[];	/* best free counts */
+						/* unused entries are -1 */
+};
+
+#define XFS_DIR3_FREE_CRC_OFF  offsetof(struct xfs_dir3_free, hdr.hdr.crc)
+
+/*
+ * In core version of the free block header, abstracted away from on-disk format
+ * differences. Use this in the code, and convert to/from the disk version using
+ * xfs_dir3_free_hdr_from_disk/xfs_dir3_free_hdr_to_disk.
+ */
+struct xfs_dir3_icfree_hdr {
+	__uint32_t	magic;
+	__uint32_t	firstdb;
+	__uint32_t	nvalid;
+	__uint32_t	nused;
+
+};
+
+void xfs_dir3_free_hdr_from_disk(struct xfs_dir3_icfree_hdr *to,
+				 struct xfs_dir2_free *from);
+
+static inline int
+xfs_dir3_free_hdr_size(struct xfs_mount *mp)
 {
-	return (mp->m_dirblksize - sizeof(struct xfs_dir2_free_hdr)) /
+	if (xfs_sb_version_hascrc(&mp->m_sb))
+		return sizeof(struct xfs_dir3_free_hdr);
+	return sizeof(struct xfs_dir2_free_hdr);
+}
+
+static inline int
+xfs_dir3_free_max_bests(struct xfs_mount *mp)
+{
+	return (mp->m_dirblksize - xfs_dir3_free_hdr_size(mp)) /
 		sizeof(xfs_dir2_data_off_t);
 }
 
+static inline __be16 *
+xfs_dir3_free_bests_p(struct xfs_mount *mp, struct xfs_dir2_free *free)
+{
+	return (__be16 *)((char *)free + xfs_dir3_free_hdr_size(mp));
+}
+
 /*
  * Convert data space db to the corresponding free db.
  */
 static inline xfs_dir2_db_t
 xfs_dir2_db_to_fdb(struct xfs_mount *mp, xfs_dir2_db_t db)
 {
-	return XFS_DIR2_FREE_FIRSTDB(mp) + db / xfs_dir2_free_max_bests(mp);
+	return XFS_DIR2_FREE_FIRSTDB(mp) + db / xfs_dir3_free_max_bests(mp);
 }
 
 /*
@@ -684,7 +731,7 @@ xfs_dir2_db_to_fdb(struct xfs_mount *mp, xfs_dir2_db_t db)
 static inline int
 xfs_dir2_db_to_fdindex(struct xfs_mount *mp, xfs_dir2_db_t db)
 {
-	return db % xfs_dir2_free_max_bests(mp);
+	return db % xfs_dir3_free_max_bests(mp);
 }
 
 /*

fs/xfs/xfs_dir2_leaf.c

@@ -1881,6 +1881,7 @@ xfs_dir2_node_to_leaf(
 	xfs_mount_t		*mp;		/* filesystem mount point */
 	int			rval;		/* successful free trim? */
 	xfs_trans_t		*tp;		/* transaction pointer */
+	struct xfs_dir3_icfree_hdr freehdr;
 
 	/*
 	 * There's more than a leaf level in the btree, so there must
@@ -1938,15 +1939,15 @@ xfs_dir2_node_to_leaf(
 	if (error)
 		return error;
 	free = fbp->b_addr;
-	ASSERT(free->hdr.magic == cpu_to_be32(XFS_DIR2_FREE_MAGIC));
-	ASSERT(!free->hdr.firstdb);
+	xfs_dir3_free_hdr_from_disk(&freehdr, free);
+
+	ASSERT(!freehdr.firstdb);
 
 	/*
 	 * Now see if the leafn and free data will fit in a leaf1.
 	 * If not, release the buffer and give up.
 	 */
-	if (xfs_dir2_leaf_size(&leaf->hdr, be32_to_cpu(free->hdr.nvalid)) >
-			mp->m_dirblksize) {
+	if (xfs_dir2_leaf_size(&leaf->hdr, freehdr.nvalid) > mp->m_dirblksize) {
 		xfs_trans_brelse(tp, fbp);
 		return 0;
 	}
@@ -1967,12 +1968,12 @@ xfs_dir2_node_to_leaf(
 	 * Set up the leaf tail from the freespace block.
 	 */
 	ltp = xfs_dir2_leaf_tail_p(mp, leaf);
-	ltp->bestcount = free->hdr.nvalid;
+	ltp->bestcount = cpu_to_be32(freehdr.nvalid);
 	/*
 	 * Set up the leaf bests table.
 	 */
-	memcpy(xfs_dir2_leaf_bests_p(ltp), free->bests,
-		be32_to_cpu(ltp->bestcount) * sizeof(xfs_dir2_data_off_t));
+	memcpy(xfs_dir2_leaf_bests_p(ltp), xfs_dir3_free_bests_p(mp, free),
+		freehdr.nvalid * sizeof(xfs_dir2_data_off_t));
 	xfs_dir2_leaf_log_bests(tp, lbp, 0, be32_to_cpu(ltp->bestcount) - 1);
 	xfs_dir2_leaf_log_tail(tp, lbp);
 	xfs_dir2_leaf_check(dp, lbp);