Revert "Don't jump to compute_result state from check_result state"

This reverts commit 4f4fd7c5.

Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Nigel Croxon <ncroxon@redhat.com>
Cc: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

drivers/md/raid5.c

@@ -4227,15 +4227,26 @@ static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
 	case check_state_check_result:
 		sh->check_state = check_state_idle;
 
-		if (s->failed > 1)
-			break;
 		/* handle a successful check operation, if parity is correct
 		 * we are done.  Otherwise update the mismatch count and repair
 		 * parity if !MD_RECOVERY_CHECK
 		 */
 		if (sh->ops.zero_sum_result == 0) {
-			/* Any parity checked was correct */
-			set_bit(STRIPE_INSYNC, &sh->state);
+			/* both parities are correct */
+			if (!s->failed)
+				set_bit(STRIPE_INSYNC, &sh->state);
+			else {
+				/* in contrast to the raid5 case we can validate
+				 * parity, but still have a failure to write
+				 * back
+				 */
+				sh->check_state = check_state_compute_result;
+				/* Returning at this point means that we may go
+				 * off and bring p and/or q uptodate again so
+				 * we make sure to check zero_sum_result again
+				 * to verify if p or q need writeback
+				 */
+			}
 		} else {
 			atomic64_add(STRIPE_SECTORS, &conf->mddev->resync_mismatches);
 			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery)) {