From ca11f209a4c88743fb4b652fd812470e6fecc598 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Sat, 6 Jan 2018 09:23:11 -0700 Subject: [PATCH] mq-deadline: make it clear that __dd_dispatch_request() works on all hw queues 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 Reviewed-by: Ming Lei Signed-off-by: Jens Axboe --- block/mq-deadline.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) 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 @@ done: 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; -- 2.30.2