drbd: Fixed a race condition between detach and start of resync

drbd_state_lock() is only there to serialize cluster wide state
changes. Testing the local disk state needs to happen while
holding the global_state_lock.

Otherwise you might see something like this (Oct 6 on kugel)
14:20:24 drbd0: conn( WFSyncUUID -> Connected ) disk( Inconsistent -> Failed )
14:20:24 drbd0: helper command: /sbin/drbdadm before-resync-target minor-0 exit code 0 (0x0)
14:20:24 drbd0: conn( Connected -> SyncTarget ) disk( Failed -> Inconsistent )

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

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 62bde5ae17f7..5fc60f622bed 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -1537,14 +1537,14 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
         }
 
         drbd_state_lock(mdev);
-
+        write_lock_irq(&global_state_lock);
         if (!get_ldev_if_state(mdev, D_NEGOTIATING)) {
+                write_unlock_irq(&global_state_lock);
                 drbd_state_unlock(mdev);
                 return;
         }
 
-        write_lock_irq(&global_state_lock);
-        ns = mdev->state;
+        ns.i = mdev->state.i;
 
         ns.aftr_isp = !_drbd_may_sync_now(mdev);