md/raid5: ensure correct assessment of drives during degraded reshape.

While reshaping a degraded array (as when reshaping a RAID0 by first
converting it to a degraded RAID4) we currently get confused about
which devices are in_sync.  In most cases we get it right, but in the
region that is being reshaped we need to treat non-failed devices as
in-sync when we have the data but haven't actually written it out yet.

Reported-by: Adam Kwolek <adam.kwolek@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/raid5.c

@@ -3065,11 +3065,17 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
 			}
 		} else if (test_bit(In_sync, &rdev->flags))
 			set_bit(R5_Insync, &dev->flags);
-		else {
+		else if (sh->sector + STRIPE_SECTORS <= rdev->recovery_offset)
 			/* in sync if before recovery_offset */
-			if (sh->sector + STRIPE_SECTORS <= rdev->recovery_offset)
-				set_bit(R5_Insync, &dev->flags);
-		}
+			set_bit(R5_Insync, &dev->flags);
+		else if (test_bit(R5_UPTODATE, &dev->flags) &&
+			 test_bit(R5_Expanded, &dev->flags))
+			/* If we've reshaped into here, we assume it is Insync.
+			 * We will shortly update recovery_offset to make
+			 * it official.
+			 */
+			set_bit(R5_Insync, &dev->flags);
+
 		if (rdev && test_bit(R5_WriteError, &dev->flags)) {
 			clear_bit(R5_Insync, &dev->flags);
 			if (!test_bit(Faulty, &rdev->flags)) {