On Thu, Aug 31, 2017 at 10:50:25PM +0000, Bart Van Assche wrote: > On Fri, 2017-09-01 at 01:27 +0800, Ming Lei wrote: > > @@ -1413,9 +1414,17 @@ static struct request *blk_old_get_request(struct > > request_queue *q, > > /* create ioc upfront */ > > create_io_context(gfp_mask, q->node); > > > > - ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM)); > > + /* > > + * When queue is frozen, we still need to allocate req for > > + * REQF_PREEMPT. > > + */ > > + if ((flags & BLK_MQ_REQ_PREEMPT) && blk_queue_is_frozen(q)) > > + blk_queue_enter_live(q); > > + else > > + ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM)); > > Hello Ming, > > Sorry but I doubt that calling blk_queue_enter_live() from inside > blk_old_get_request() is safe. Calling blk_queue_enter_live() is only safe > before a request queue has been marked dead. What prevents a kernel thread > that holds a reference on a request queue and that is running concurrently > with blk_cleanup_queue() to call blk_old_get_request() after a queue has > been marked dead?
I have sent one delta patch in list, which will only call blk_queue_enter_live() iff SCSI device is in QUIESCE. -- Ming
