ocfs2: Add directory block trailers.
Future ocfs2 features metaecc and indexed directories need to store a
little bit of data in each dirblock. For compatibility, we place this
in a trailer at the end of the dirblock. The trailer plays itself as an
empty dirent, so that if the features are turned off, it can be reused
without requiring a tunefs scan.
This code adds the trailer and validates it when the block is read in.
[ Mark is the original author, but I reinserted this code before his
dir index work. -- Joel ]
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index 290fa26..af0013b 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/fs/ocfs2/ocfs2_fs.h
@@ -65,6 +65,7 @@
#define OCFS2_EXTENT_BLOCK_SIGNATURE "EXBLK01"
#define OCFS2_GROUP_DESC_SIGNATURE "GROUP01"
#define OCFS2_XATTR_BLOCK_SIGNATURE "XATTR01"
+#define OCFS2_DIR_TRAILER_SIGNATURE "DIRTRL1"
/* Compatibility flags */
#define OCFS2_HAS_COMPAT_FEATURE(sb,mask) \
@@ -752,6 +753,34 @@
} __attribute__ ((packed));
/*
+ * Per-block record for the unindexed directory btree. This is carefully
+ * crafted so that the rec_len and name_len records of an ocfs2_dir_entry are
+ * mirrored. That way, the directory manipulation code needs a minimal amount
+ * of update.
+ *
+ * NOTE: Keep this structure aligned to a multiple of 4 bytes.
+ */
+struct ocfs2_dir_block_trailer {
+/*00*/ __le64 db_compat_inode; /* Always zero. Was inode */
+
+ __le16 db_compat_rec_len; /* Backwards compatible with
+ * ocfs2_dir_entry. */
+ __u8 db_compat_name_len; /* Always zero. Was name_len */
+ __u8 db_reserved0;
+ __le16 db_reserved1;
+ __le16 db_free_rec_len; /* Size of largest empty hole
+ * in this block. (unused) */
+/*10*/ __u8 db_signature[8]; /* Signature for verification */
+ __le64 db_reserved2;
+ __le64 db_free_next; /* Next block in list (unused) */
+/*20*/ __le64 db_blkno; /* Offset on disk, in blocks */
+ __le64 db_parent_dinode; /* dinode which owns me, in
+ blocks */
+/*30*/ __le64 db_check; /* Error checking */
+/*40*/
+};
+
+/*
* On disk allocator group structure for OCFS2
*/
struct ocfs2_group_desc
