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 <ax...@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