[PATCH] md: make sure the events count in an md array never returns to zero

Now that we sometimes step the array events count backwards (when
transitioning dirty->clean where nothing else interesting has happened - so
that we don't need to write to spares all the time), it is possible for the
event count to return to zero, which is potentially confusing and triggers and
MD_BUG.

We could possibly remove the MD_BUG, but is just as easy, and probably safer,
to make sure we never return to zero.

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

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index d1cb45f6d6a9..ec3d8e8a0bd3 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1633,7 +1633,8 @@ repeat:
          * and 'events' is odd, we can roll back to the previous clean state */
         if (nospares
             && (mddev->in_sync && mddev->recovery_cp == MaxSector)
-            && (mddev->events & 1))
+            && (mddev->events & 1)
+            && mddev->events != 1)
                 mddev->events--;
         else {
                 /* otherwise we have to go forward and ... */