blk_queue_bypass_start — enter queue bypass mode
| void blk_queue_bypass_start ( | struct request_queue * q ); | 
   In bypass mode, only the dispatch FIFO queue of q is used.  This
   function makes q enter bypass mode and drains all requests which were
   throttled or issued before.  On return, it's guaranteed that no request
   is being throttled or has ELVPRIV set and blk_queue_bypass true
   inside queue or RCU read lock.