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/commit.c b/fs/jbd2/commit.c
index 840f70f..69d7803 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -627,7 +627,7 @@
 
 		tag = (journal_block_tag_t *) tagp;
 		write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
-		tag->t_flags = cpu_to_be32(tag_flag);
+		tag->t_flags = cpu_to_be16(tag_flag);
 		tagp += tag_bytes;
 		space_left -= tag_bytes;
 
@@ -651,7 +651,7 @@
                            submitting the IOs.  "tag" still points to
                            the last tag we set up. */
 
-			tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
+			tag->t_flags |= cpu_to_be16(JBD2_FLAG_LAST_TAG);
 
 start_journal_io:
 			for (i = 0; i < bufs; i++) {
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);