jbd2: clean up checksum verification in do_one_pass()

Remove the unnecessary chksum_err and checksum_seen variables as well as
some redundant code to make the function easier to understand.

[ With changes suggested by jack@ and tytso@ ]

Signed-off-by: Shijie Luo <luoshijie1@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200819122955.33526-1-luoshijie1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/jbd2/recovery.c

@@ -690,57 +690,35 @@ static int do_one_pass(journal_t *journal,
 			 * number. */
 			if (pass == PASS_SCAN &&
 			    jbd2_has_feature_checksum(journal)) {
-				int chksum_err, chksum_seen;
 				struct commit_header *cbh =
 					(struct commit_header *)bh->b_data;
 				unsigned found_chksum =
 					be32_to_cpu(cbh->h_chksum[0]);
 
-				chksum_err = chksum_seen = 0;
-
 				if (info->end_transaction) {
 					journal->j_failed_commit =
 						info->end_transaction;
 					brelse(bh);
 					break;
 				}
 
-				if (crc32_sum == found_chksum &&
-				    cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
-				    cbh->h_chksum_size ==
-						JBD2_CRC32_CHKSUM_SIZE)
-				       chksum_seen = 1;
-				else if (!(cbh->h_chksum_type == 0 &&
-					     cbh->h_chksum_size == 0 &&
-					     found_chksum == 0 &&
-					     !chksum_seen))
-				/*
-				 * If fs is mounted using an old kernel and then
-				 * kernel with journal_chksum is used then we
-				 * get a situation where the journal flag has
-				 * checksum flag set but checksums are not
-				 * present i.e chksum = 0, in the individual
-				 * commit blocks.
-				 * Hence to avoid checksum failures, in this
-				 * situation, this extra check is added.
-				 */
-						chksum_err = 1;
-
-				if (chksum_err) {
-					info->end_transaction = next_commit_ID;
-
-					if (!jbd2_has_feature_async_commit(journal)) {
-						journal->j_failed_commit =
-							next_commit_ID;
-						brelse(bh);
-						break;
-					}
-				}
+				/* Neither checksum match nor unused? */
+				if (!((crc32_sum == found_chksum &&
+				       cbh->h_chksum_type ==
+						JBD2_CRC32_CHKSUM &&
+				       cbh->h_chksum_size ==
+						JBD2_CRC32_CHKSUM_SIZE) ||
+				      (cbh->h_chksum_type == 0 &&
+				       cbh->h_chksum_size == 0 &&
+				       found_chksum == 0)))
+					goto chksum_error;
+
 				crc32_sum = ~0;
 			}
 			if (pass == PASS_SCAN &&
 			    !jbd2_commit_block_csum_verify(journal,
 							   bh->b_data)) {
+			chksum_error:
 				info->end_transaction = next_commit_ID;
 
 				if (!jbd2_has_feature_async_commit(journal)) {