| Message ID | 2c4afe1c-fb16-0d48-7c5c-2b063a16dbd1@kernel.dk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Jan 05, 2018 at 02:56:38PM -0700, Jens Axboe wrote: > Don't pass in the hardware queue to __dd_dispatch_request(), since it > leads the reader to believe that we are returning a request for that > specific hardware queue. That's not how mq-deadline works, the state > for determining which request to serve next is shared across all > hardware queues for a device. Reviewed-by: Omar Sandoval <osandov@fb.com> > Signed-off-by: Jens Axboe <axboe@kernel.dk> > > --- > > diff --git a/block/mq-deadline.c b/block/mq-deadline.c > index d56972e8ebda..c56f211c8440 100644 > --- a/block/mq-deadline.c > +++ b/block/mq-deadline.c > @@ -267,9 +267,8 @@ deadline_next_request(struct deadline_data *dd, int data_dir) > * deadline_dispatch_requests selects the best request according to > * read/write expire, fifo_batch, etc > */ > -static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx) > +static struct request *__dd_dispatch_request(struct deadline_data *dd) > { > - struct deadline_data *dd = hctx->queue->elevator->elevator_data; > struct request *rq, *next_rq; > bool reads, writes; > int data_dir; > @@ -372,13 +371,19 @@ static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx) > return rq; > } > > +/* > + * One confusing aspect here is that we get called for a specific > + * hardware queue, but we return a request that may not be for a > + * different hardware queue. This is because mq-deadline has shared > + * state for all hardware queues, in terms of sorting, FIFOs, etc. > + */ > static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) > { > struct deadline_data *dd = hctx->queue->elevator->elevator_data; > struct request *rq; > > spin_lock(&dd->lock); > - rq = __dd_dispatch_request(hctx); > + rq = __dd_dispatch_request(dd); > spin_unlock(&dd->lock); > > return rq; > > -- > Jens Axboe >
On Fri, Jan 05, 2018 at 02:56:38PM -0700, Jens Axboe wrote: > Don't pass in the hardware queue to __dd_dispatch_request(), since it > leads the reader to believe that we are returning a request for that > specific hardware queue. That's not how mq-deadline works, the state > for determining which request to serve next is shared across all > hardware queues for a device. > > Signed-off-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Ming Lei <ming.lei@redhat.com>
diff --git a/block/mq-deadline.c b/block/mq-deadline.c index d56972e8ebda..c56f211c8440 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -267,9 +267,8 @@ deadline_next_request(struct deadline_data *dd, int data_dir) * deadline_dispatch_requests selects the best request according to * read/write expire, fifo_batch, etc */ -static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx) +static struct request *__dd_dispatch_request(struct deadline_data *dd) { - struct deadline_data *dd = hctx->queue->elevator->elevator_data; struct request *rq, *next_rq; bool reads, writes; int data_dir; @@ -372,13 +371,19 @@ static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx) return rq; } +/* + * One confusing aspect here is that we get called for a specific + * hardware queue, but we return a request that may not be for a + * different hardware queue. This is because mq-deadline has shared + * state for all hardware queues, in terms of sorting, FIFOs, etc. + */ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) { struct deadline_data *dd = hctx->queue->elevator->elevator_data; struct request *rq; spin_lock(&dd->lock); - rq = __dd_dispatch_request(hctx); + rq = __dd_dispatch_request(dd); spin_unlock(&dd->lock); return rq;
Don't pass in the hardware queue to __dd_dispatch_request(), since it leads the reader to believe that we are returning a request for that specific hardware queue. That's not how mq-deadline works, the state for determining which request to serve next is shared across all hardware queues for a device. Signed-off-by: Jens Axboe <axboe@kernel.dk> ---