drbd: Fixed race condition in drbd_queue_bitmap_io

May only test for ap_bio_cnt == 0 under req_lock. It can increase
only under req_lock.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 843b909..975dc5a 100644 (file)
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -3849,11 +3849,13 @@ void drbd_queue_bitmap_io(struct drbd_conf *mdev,
        mdev->bm_io_work.done = done;
        mdev->bm_io_work.why = why;
 
+       spin_lock_irq(&mdev->req_lock);
        set_bit(BITMAP_IO, &mdev->flags);
        if (atomic_read(&mdev->ap_bio_cnt) == 0) {
                if (!test_and_set_bit(BITMAP_IO_QUEUED, &mdev->flags))
                        drbd_queue_work(&mdev->data.work, &mdev->bm_io_work.w);
        }
+       spin_unlock_irq(&mdev->req_lock);
 }
 
 /**