md/bitmap: protect clearing of ->bitmap by mddev->lock

This makes it safe to inspect the struct while holding only
the spinlock.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 1695ee5f3ffc..3424b1915fc4 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1619,7 +1619,9 @@ void bitmap_destroy(struct mddev *mddev)
                 return;
 
         mutex_lock(&mddev->bitmap_info.mutex);
+        spin_lock(&mddev->lock);
         mddev->bitmap = NULL; /* disconnect from the md device */
+        spin_unlock(&mddev->lock);
         mutex_unlock(&mddev->bitmap_info.mutex);
         if (mddev->thread)
                 mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;