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mq-deadline: Fix request accounting

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The block layer may call the I/O scheduler .finish_request() callback
without having called the .insert_requests() callback. Make sure that the
mq-deadline I/O statistics are correct if the block layer inserts an I/O
request that bypasses the I/O scheduler. This patch prevents that lower
priority I/O is delayed longer than necessary for mixed I/O priority
workloads.

Cc: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Reported-by: Niklas Cassel <Niklas.Cassel@wdc.com>
Fixes: 08a9ad8bf6 ("block/mq-deadline: Add cgroup support")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210824170520.1659173-1-bvanassche@acm.org
Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
Tested-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2021-08-24 10:05:20 -07:00 committed by Jens Axboe
parent a9ed27a764
commit b6d2b054e8
1 changed files with 11 additions and 5 deletions
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16
block/mq-deadline.c
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@ -711,6 +711,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
prio = ioprio_class_to_prio[ioprio_class];
dd_count(dd, inserted, prio);
rq->elv.priv[0] = (void *)(uintptr_t)1;
if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
blk_mq_free_requests(&free);
@ -759,12 +760,10 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
spin_unlock(&dd->lock);
}
/*
* Nothing to do here. This is defined only to ensure that .finish_request
* method is called upon request completion.
*/
/* Callback from inside blk_mq_rq_ctx_init(). */
static void dd_prepare_request(struct request *rq)
{
rq->elv.priv[0] = NULL;
}
/*
@ -791,7 +790,14 @@ static void dd_finish_request(struct request *rq)
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
struct dd_per_prio *per_prio = &dd->per_prio[prio];
dd_count(dd, completed, prio);
/*
* The block layer core may call dd_finish_request() without having
* called dd_insert_requests(). Hence only update statistics for
* requests for which dd_insert_requests() has been called. See also
* blk_mq_request_bypass_insert().
*/
if (rq->elv.priv[0])
dd_count(dd, completed, prio);
if (blk_queue_is_zoned(q)) {
unsigned long flags;