Re: [PATCH] blk-mq: Make sure that the affected zone is unlocked if a request times out
From: Ming Lei <hidden>
Date: 2018-02-28 01:35:38
On Tue, Feb 27, 2018 at 04:28:30PM -0800, Bart Van Assche wrote:
If a request times out the .completed_request() method is not called
If BLK_EH_HANDLED is returned from .timeout(), __blk_mq_complete_request() should have called .completed_request(). Otherwise, somewhere may be wrong about timeout handling. Could you investigate why .completed_request isn't called under this situation?
and the .finish_request() method is only called if RQF_ELVPRIV has
.finish_request() is counter-pair of .prepare_request(), and both aren't implemented by mq-deadline, so RQF_ELVPRIV needn't to be set, and the current rule is that this flag is managed by block core.
quoted hunk ↗ jump to hunk
been set. Hence this patch that sets RQF_ELVPRIV and that adds a .finish_request() method. Without this patch, if a request times out the zone that request applies to remains locked forever and no further writes are accepted for that zone. Fixes: 5700f69178e9 ("mq-deadline: Introduce zone locking support") Signed-off-by: Damien Le Moal <redacted> Signed-off-by: Bart Van Assche <redacted> Cc: Hannes Reinecke <hare@suse.com> Cc: Ming Lei <redacted> --- block/mq-deadline.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)diff --git a/block/mq-deadline.c b/block/mq-deadline.c index c56f211c8440..55d5b7a02d62 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c@@ -367,7 +367,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd) * If the request needs its target zone locked, do it. */ blk_req_zone_write_lock(rq); - rq->rq_flags |= RQF_STARTED; + /* Set RQF_ELVPRIV to ensure that .finish_request() gets called */ + rq->rq_flags |= RQF_STARTED | RQF_ELVPRIV; return rq; }@@ -539,7 +540,9 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx, * For zoned block devices, write unlock the target zone of * completed write requests. Do this while holding the zone lock * spinlock so that the zone is never unlocked while deadline_fifo_request() - * while deadline_next_request() are executing. + * while deadline_next_request() are executing. This function is called twice + * for requests that complete in a normal way and once for requests that time + * out. */ static void dd_completed_request(struct request *rq) {@@ -757,6 +760,7 @@ static struct elevator_type mq_deadline = { .insert_requests = dd_insert_requests, .dispatch_request = dd_dispatch_request, .completed_request = dd_completed_request, + .finish_request = dd_completed_request, .next_request = elv_rb_latter_request, .former_request = elv_rb_former_request, .bio_merge = dd_bio_merge,-- 2.16.2
-- Ming