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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>
Signed-off-by: azrim <mirzaspc@gmail.com>
This commit is contained in:
Jens Axboe 2018-01-06 09:23:11 -07:00 committed by azrim
parent d6ea93a924
commit 7987646dec
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GPG Key ID: 497F8FB059B45D1C
1 changed files with 8 additions and 2 deletions
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10
block/mq-deadline.c
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@ -195,7 +195,7 @@ static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
* 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;
@ -288,13 +288,19 @@ 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;