dm verity: skip redundant verity_handle_err() on I/O errors

Without FEC, dm-verity won't call verity_handle_err() when I/O fails,
but with FEC enabled, it currently does even if an I/O error has
occurred.

If there is an I/O error and FEC correction fails, return the error
instead of calling verity_handle_err() again.
Suggested-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Akilesh Kailash <akailash@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-verity-target.c

@@ -475,6 +475,7 @@ static int verity_verify_io(struct dm_verity_io *io)
 	struct bvec_iter start;
 	unsigned b;
 	struct crypto_wait wait;
+	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 
 	for (b = 0; b < io->n_blocks; b++) {
 		int r;
@@ -529,10 +530,18 @@ static int verity_verify_io(struct dm_verity_io *io)
 		else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
 					   cur_block, NULL, &start) == 0)
 			continue;
-		else if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
+		else {
+			if (bio->bi_status) {
+				/*
+				 * Error correction failed; Just return error
+				 */
+				return -EIO;
+			}
+			if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
 					      cur_block))
 				return -EIO;
 		}
+	}
 
 	return 0;
 }