jbd2: checksum data blocks that are stored in the journal

Calculate and verify checksums of each data block being stored in the journal.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 9072f03..e9a3c4c 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -2097,10 +2097,16 @@
  */
 size_t journal_tag_bytes(journal_t *journal)
 {
+	journal_block_tag_t tag;
+	size_t x = 0;
+
+	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		x += sizeof(tag.t_checksum);
+
 	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
-		return JBD2_TAG_SIZE64;
+		return x + JBD2_TAG_SIZE64;
 	else
-		return JBD2_TAG_SIZE32;
+		return x + JBD2_TAG_SIZE32;
 }
 
 /*