jbd2: complain about descriptor block checksum errors

We should complain in dmesg when journal recovery fails on account of
the descriptor block being corrupt, so that the diagnostic data can
be recovered.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index bcbef08..b5128c6 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -524,6 +524,9 @@
 			if (descr_csum_size > 0 &&
 			    !jbd2_descr_block_csum_verify(journal,
 							  bh->b_data)) {
+				printk(KERN_ERR "JBD2: Invalid checksum "
+				       "recovering block %lu in log\n",
+				       next_log_block);
 				err = -EIO;
 				brelse(bh);
 				goto failed;