jbd2: change disk layout for metadata checksumming

Define flags and allocate space in on-disk journal structures to support
checksumming of journal metadata.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index c1a0335..980f3d6 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -193,10 +193,10 @@
 
 		nr++;
 		tagp += tag_bytes;
-		if (!(tag->t_flags & cpu_to_be32(JBD2_FLAG_SAME_UUID)))
+		if (!(tag->t_flags & cpu_to_be16(JBD2_FLAG_SAME_UUID)))
 			tagp += 16;
 
-		if (tag->t_flags & cpu_to_be32(JBD2_FLAG_LAST_TAG))
+		if (tag->t_flags & cpu_to_be16(JBD2_FLAG_LAST_TAG))
 			break;
 	}
 
@@ -485,7 +485,7 @@
 				unsigned long io_block;
 
 				tag = (journal_block_tag_t *) tagp;
-				flags = be32_to_cpu(tag->t_flags);
+				flags = be16_to_cpu(tag->t_flags);
 
 				io_block = next_log_block++;
 				wrap(journal, next_log_block);