| Message ID | 20190408094047.29150-2-ming.lei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | blk-mq/nvme: cancel request synchronously | expand |
On Mon, Apr 08, 2019 at 05:40:46PM +0800, Ming Lei wrote: > In NVMe's error handler, follows the typical steps of tearing down > hardware for recovering controller: > > 1) stop blk_mq hw queues > 2) stop the real hw queues > 3) cancel in-flight requests via > blk_mq_tagset_busy_iter(tags, cancel_request, ...) > cancel_request(): > mark the request as abort > blk_mq_complete_request(req); > 4) destroy real hw queues > > However, there may be race between #3 and #4, because blk_mq_complete_request() > may run q->mq_ops->complete(rq) remotelly and asynchronously, and > ->complete(rq) may be run after #4. > > This patch introduces blk_mq_complete_request_sync() for fixing the > above race. > > Cc: Keith Busch <kbusch@kernel.org> > Cc: Sagi Grimberg <sagi@grimberg.me> > Cc: Bart Van Assche <bvanassche@acm.org> > Cc: James Smart <james.smart@broadcom.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: linux-nvme@lists.infradead.org > Signed-off-by: Ming Lei <ming.lei@redhat.com> > --- > block/blk-mq.c | 11 +++++++++++ > include/linux/blk-mq.h | 1 + > 2 files changed, 12 insertions(+) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index a9354835cf51..d8d89f3514ac 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -654,6 +654,17 @@ bool blk_mq_complete_request(struct request *rq) > } > EXPORT_SYMBOL(blk_mq_complete_request); > > +bool blk_mq_complete_request_sync(struct request *rq) > +{ > + if (unlikely(blk_should_fake_timeout(rq->q))) > + return false; > + > + WRITE_ONCE(rq->state, MQ_RQ_COMPLETE); > + rq->q->mq_ops->complete(rq); > + return true; > +} > +EXPORT_SYMBOL_GPL(blk_mq_complete_request_sync); Could we possibly drop the fake timeout in this path? We're using this in error handling that is past pretending completing requests didn't happen. Otherwise this all looks good to me.
On Mon, Apr 08, 2019 at 10:15:05AM -0600, Keith Busch wrote: > > +bool blk_mq_complete_request_sync(struct request *rq) > > +{ > > + if (unlikely(blk_should_fake_timeout(rq->q))) > > + return false; > > + > > + WRITE_ONCE(rq->state, MQ_RQ_COMPLETE); > > + rq->q->mq_ops->complete(rq); > > + return true; > > +} > > +EXPORT_SYMBOL_GPL(blk_mq_complete_request_sync); > > Could we possibly drop the fake timeout in this path? We're using this > in error handling that is past pretending completing requests didn't > happen. .. and at that point we can also drop the return value.
diff --git a/block/blk-mq.c b/block/blk-mq.c index a9354835cf51..d8d89f3514ac 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -654,6 +654,17 @@ bool blk_mq_complete_request(struct request *rq) } EXPORT_SYMBOL(blk_mq_complete_request); +bool blk_mq_complete_request_sync(struct request *rq) +{ + if (unlikely(blk_should_fake_timeout(rq->q))) + return false; + + WRITE_ONCE(rq->state, MQ_RQ_COMPLETE); + rq->q->mq_ops->complete(rq); + return true; +} +EXPORT_SYMBOL_GPL(blk_mq_complete_request_sync); + int blk_mq_request_started(struct request *rq) { return blk_mq_rq_state(rq) != MQ_RQ_IDLE; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index cb2aa7ecafff..1412c983e7b8 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -302,6 +302,7 @@ void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list); void blk_mq_kick_requeue_list(struct request_queue *q); void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs); bool blk_mq_complete_request(struct request *rq); +bool blk_mq_complete_request_sync(struct request *rq); bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list, struct bio *bio); bool blk_mq_queue_stopped(struct request_queue *q);
In NVMe's error handler, follows the typical steps of tearing down hardware for recovering controller: 1) stop blk_mq hw queues 2) stop the real hw queues 3) cancel in-flight requests via blk_mq_tagset_busy_iter(tags, cancel_request, ...) cancel_request(): mark the request as abort blk_mq_complete_request(req); 4) destroy real hw queues However, there may be race between #3 and #4, because blk_mq_complete_request() may run q->mq_ops->complete(rq) remotelly and asynchronously, and ->complete(rq) may be run after #4. This patch introduces blk_mq_complete_request_sync() for fixing the above race. Cc: Keith Busch <kbusch@kernel.org> Cc: Sagi Grimberg <sagi@grimberg.me> Cc: Bart Van Assche <bvanassche@acm.org> Cc: James Smart <james.smart@broadcom.com> Cc: Christoph Hellwig <hch@lst.de> Cc: linux-nvme@lists.infradead.org Signed-off-by: Ming Lei <ming.lei@redhat.com> --- block/blk-mq.c | 11 +++++++++++ include/linux/blk-mq.h | 1 + 2 files changed, 12 insertions(+)