md: make sure a re-add after a restart honours bitmap when resyncing

Commit 1757128438d41670ded8bc3bc735325cc07dc8f9 was slightly bad.  If an array
has a write-intent bitmap, and you remove a drive, then readd it, only the
changed parts should be resynced.  However after the above commit, this only
works if the array has not been shut down and restarted.

This is because it sets 'fullsync' at little more often than it should.  This
patch is more careful.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 650991bddd8e..ea2a58d28871 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1972,7 +1972,8 @@ static int run(mddev_t *mddev)
                     !test_bit(In_sync, &disk->rdev->flags)) {
                         disk->head_position = 0;
                         mddev->degraded++;
-                        conf->fullsync = 1;
+                        if (disk->rdev)
+                                conf->fullsync = 1;
                 }
         }
         if (mddev->degraded == conf->raid_disks) {