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mq-deadline: make it clear that __dd_dispatch_request() works on all hw queues

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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>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-01-06 09:23:11 -07:00
parent 14db491726
commit ca11f209a4
1 changed files with 8 additions and 3 deletions
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11
block/mq-deadline.c
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@ -267,9 +267,8 @@ deadline_next_request(struct deadline_data *dd, int data_dir)
* deadline_dispatch_requests selects the best request according to * deadline_dispatch_requests selects the best request according to
* read/write expire, fifo_batch, etc * 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; struct request *rq, *next_rq;
bool reads, writes; bool reads, writes;
int data_dir; int data_dir;
@ -372,13 +371,19 @@ done:
return rq; 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) static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
{ {
struct deadline_data *dd = hctx->queue->elevator->elevator_data; struct deadline_data *dd = hctx->queue->elevator->elevator_data;
struct request *rq; struct request *rq;
spin_lock(&dd->lock); spin_lock(&dd->lock);
rq = __dd_dispatch_request(hctx); rq = __dd_dispatch_request(dd);
spin_unlock(&dd->lock); spin_unlock(&dd->lock);
return rq; return rq;