ocfs2/dlm: fix race between dispatched_work and dlm_lockres_grab_inflight_worker

ocfs2/dlm: fix race between dispatched_work and dlm_lockres_grab_inflight_worker

Commit ac4fef4d23ed ("ocfs2/dlm: do not purge lockres that is queued for
assert master") may have the following possible race case:

  dlm_dispatch_assert_master       dlm_wq
  ========================================================================
  queue_work(dlm->quedlm_worker,
      &dlm->dispatched_work);
                                 dispatch work,
                                 dlm_lockres_drop_inflight_worker
                                 *BUG_ON(res->inflight_assert_workers == 0)*
  dlm_lockres_grab_inflight_worker
  inflight_assert_workers++

So ensure inflight_assert_workers to be increased first.

Signed-off-by: Joseph Qi <[email protected]>
Signed-off-by: Xue jiufei <[email protected]>
Cc: Joel Becker <[email protected]>
Reviewed-by: Mark Fasheh <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>