md: don't clear MD_CHANGE_CLEAN in md_update_sb() for external arrays

If this bit is cleared in md_update_sb() the kernel will allow writes to the
array if userspace triggers md_allow_write(), e.g. through stripe_cache_size,
when mdmon is not active.  When mdmon is active the array transitions to
active-idle bypassing write-pending, setting up a race for mdmon to set the
array clean before a write arrives.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index c148b630215484f9689bf9257d6acf286685c37a..a1f6b59b8b37d0a2ba71232288c1ddd21248641b 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2167,9 +2167,10 @@ repeat:
                                rdev->recovery_offset = mddev->curr_resync_completed;
 
        }       
-       if (mddev->external || !mddev->persistent) {
+       if (!mddev->persistent) {
+               if (!mddev->external)
+                       clear_bit(MD_CHANGE_CLEAN, &mddev->flags);
                clear_bit(MD_CHANGE_DEVS, &mddev->flags);
-               clear_bit(MD_CHANGE_CLEAN, &mddev->flags);
                wake_up(&mddev->sb_wait);
                return;
        }