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Commit d4aad7ff authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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cfq-iosched: fold cfq_find_alloc_queue() into cfq_get_queue() 



cfq_find_alloc_queue() checks whether a queue actually needs to be
allocated, which is unnecessary as its sole caller, cfq_get_queue(),
only calls it if so.  Also, the oom queue fallback logic is scattered
between cfq_get_queue() and cfq_find_alloc_queue().  There really
isn't much going on in the latter and things can be made simpler by
folding it into cfq_get_queue().

This patch collapses cfq_find_alloc_queue() into cfq_get_queue().  The
change is fairly straight-forward with one exception - async_cfqq is
now initialized to NULL and the "!is_sync" test in the last if
conditional is replaced with "async_cfqq" test.  This is because gcc
(5.1.1) gets confused for some reason and warns that async_cfqq may be
used uninitialized otherwise.  Oh well, the code isn't necessarily
worse this way.

This patch doesn't cause any functional difference.

v2: Updated to reflect GFP_ATOMIC -> GPF_NOWAIT.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 322731ed

block/cfq-iosched.c

+15 −34
Original line number Diff line number Diff line
@@ -3640,33 +3640,6 @@ static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) 
static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }

#endif  /* CONFIG_CFQ_GROUP_IOSCHED */



static struct cfq_queue *

cfq_find_alloc_queue(struct cfq_data *cfqd, struct cfq_group *cfqg, bool is_sync,

		     struct cfq_io_cq *cic, struct bio *bio)

{

	struct cfq_queue *cfqq;



	cfqq = cic_to_cfqq(cic, is_sync);



	/*

	 * Always try a new alloc if we fell back to the OOM cfqq

	 * originally, since it should just be a temporary situation.

	 */

	if (!cfqq || cfqq == &cfqd->oom_cfqq) {

		cfqq = kmem_cache_alloc_node(cfq_pool,

					     GFP_NOWAIT | __GFP_ZERO,

					     cfqd->queue->node);

		if (cfqq) {

			cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);

			cfq_init_prio_data(cfqq, cic);

			cfq_link_cfqq_cfqg(cfqq, cfqg);

			cfq_log_cfqq(cfqd, cfqq, "alloced");

		} else

			cfqq = &cfqd->oom_cfqq;

	}

	return cfqq;

}



static struct cfq_queue **

cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)

{
@@ -3691,7 +3664,7 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic, 
{

	int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);

	int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);

	struct cfq_queue **async_cfqq;

	struct cfq_queue **async_cfqq = NULL;

	struct cfq_queue *cfqq;

	struct cfq_group *cfqg;
@@ -3714,12 +3687,20 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic, 
			goto out;

	}



	cfqq = cfq_find_alloc_queue(cfqd, cfqg, is_sync, cic, bio);

	cfqq = kmem_cache_alloc_node(cfq_pool, GFP_NOWAIT | __GFP_ZERO,

				     cfqd->queue->node);

	if (!cfqq) {

		cfqq = &cfqd->oom_cfqq;

		goto out;

	}



	cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);

	cfq_init_prio_data(cfqq, cic);

	cfq_link_cfqq_cfqg(cfqq, cfqg);

	cfq_log_cfqq(cfqd, cfqq, "alloced");



	/*

	 * pin the queue now that it's allocated, scheduler exit will prune it

	 */

	if (!is_sync && cfqq != &cfqd->oom_cfqq) {

	if (async_cfqq) {

		/* a new async queue is created, pin and remember */

		cfqq->ref++;

		*async_cfqq = cfqq;

	}
@@ -4469,7 +4450,7 @@ static int cfq_init_queue(struct request_queue *q, struct elevator_type *e) 
		cfqd->prio_trees[i] = RB_ROOT;



	/*

	 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.

	 * Our fallback cfqq if cfq_get_queue() runs into OOM issues.

	 * Grab a permanent reference to it, so that the normal code flow

	 * will not attempt to free it.  oom_cfqq is linked to root_group

	 * but shouldn't hold a reference as it'll never be unlinked.  Lose