Merge branch 'md-next' of https://github.com/liu-song-6/linux into for-5.2/block

Pull MD fixes from Song.

* 'md-next' of https://github.com/liu-song-6/linux:
  md/raid: raid5 preserve the writeback action after the parity check
  Revert "Don't jump to compute_result state from check_result state"
  md: return -ENODEV if rdev has no mddev assigned
  block: fix use-after-free on gendisk

drivers/md/md.c

@@ -3380,10 +3380,10 @@ rdev_attr_store(struct kobject *kobj, struct attribute *attr,
 		return -EIO;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
-	rv = mddev ? mddev_lock(mddev): -EBUSY;
+	rv = mddev ? mddev_lock(mddev) : -ENODEV;
 	if (!rv) {
 		if (rdev->mddev == NULL)
-			rv = -EBUSY;
+			rv = -ENODEV;
 		else
 			rv = entry->store(rdev, page, length);
 		mddev_unlock(mddev);

drivers/md/raid5.c

@@ -4191,7 +4191,7 @@ static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
 		/* now write out any block on a failed drive,
 		 * or P or Q if they were recomputed
 		 */
-		BUG_ON(s->uptodate < disks - 1); /* We don't need Q to recover */
+		dev = NULL;
 		if (s->failed == 2) {
 			dev = &sh->dev[s->failed_num[1]];
 			s->locked++;
@@ -4216,6 +4216,14 @@ static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
 			set_bit(R5_LOCKED, &dev->flags);
 			set_bit(R5_Wantwrite, &dev->flags);
 		}
+		if (WARN_ONCE(dev && !test_bit(R5_UPTODATE, &dev->flags),
+			      "%s: disk%td not up to date\n",
+			      mdname(conf->mddev),
+			      dev - (struct r5dev *) &sh->dev)) {
+			clear_bit(R5_LOCKED, &dev->flags);
+			clear_bit(R5_Wantwrite, &dev->flags);
+			s->locked--;
+		}
 		clear_bit(STRIPE_DEGRADED, &sh->state);
 
 		set_bit(STRIPE_INSYNC, &sh->state);
@@ -4227,15 +4235,26 @@ 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)) {