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>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 31670f8d6b65..858fdbb7eb07 100644
--- a/drivers/md/raid5.c
+++ b/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)) {