Commit 2da8de0b authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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cfq-iosched: remove @gfp_mask from cfq_find_alloc_queue() 



Even when allocations fail, cfq_find_alloc_queue() always returns a
valid cfq_queue by falling back to the oom cfq_queue.  As such, there
isn't much point in taking @gfp_mask and trying "harder" if __GFP_WAIT
is set.  GFP_NOWAIT allocations don't fail often and even when they do
the degraded behavior is acceptable and temporary.

After all, the only reason get_request(), which ultimately determines
the gfp_mask, cares about __GFP_WAIT is to guarantee request
allocation, assuming IO forward progress, for callers which are
willing to wait.  There's no reason for cfq_find_alloc_queue() to
behave differently on __GFP_WAIT when it already has a fallback
mechanism.

Remove @gfp_mask from cfq_find_alloc_queue() and propagate the changes
to its callers.  This simplifies the function quite a bit and will
help making async queues per-cfq_group.

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 d93a11f1

block/cfq-iosched.c

+10 −35
Original line number Diff line number Diff line
@@ -883,8 +883,7 @@ static inline int cfqg_busy_async_queues(struct cfq_data *cfqd, 


static void cfq_dispatch_insert(struct request_queue *, struct request *);

static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,

				       struct cfq_io_cq *cic, struct bio *bio,

				       gfp_t gfp_mask);

				       struct cfq_io_cq *cic, struct bio *bio);



static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)

{
@@ -3575,7 +3574,7 @@ static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio) 
	cfqq = cic_to_cfqq(cic, false);

	if (cfqq) {

		cfq_put_queue(cfqq);

		cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio, GFP_NOWAIT);

		cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio);

		cic_set_cfqq(cic, cfqq, false);

	}
@@ -3643,13 +3642,12 @@ static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { 


static struct cfq_queue *

cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,

		     struct bio *bio, gfp_t gfp_mask)

		     struct bio *bio)

{

	struct blkcg *blkcg;

	struct cfq_queue *cfqq, *new_cfqq = NULL;

	struct cfq_queue *cfqq;

	struct cfq_group *cfqg;



retry:

	rcu_read_lock();



	blkcg = bio_blkcg(bio);
@@ -3666,27 +3664,9 @@ retry: 
	 * originally, since it should just be a temporary situation.

	 */

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

		cfqq = NULL;

		if (new_cfqq) {

			cfqq = new_cfqq;

			new_cfqq = NULL;

		} else if (gfp_mask & __GFP_WAIT) {

			rcu_read_unlock();

			spin_unlock_irq(cfqd->queue->queue_lock);

			new_cfqq = kmem_cache_alloc_node(cfq_pool,

					gfp_mask | __GFP_ZERO,

					cfqd->queue->node);

			spin_lock_irq(cfqd->queue->queue_lock);

			if (new_cfqq)

				goto retry;

			else

				return &cfqd->oom_cfqq;

		} else {

		cfqq = kmem_cache_alloc_node(cfq_pool,

					gfp_mask | __GFP_ZERO,

					     GFP_NOWAIT | __GFP_ZERO,

					     cfqd->queue->node);

		}



		if (cfqq) {

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

			cfq_init_prio_data(cfqq, cic);
@@ -3696,9 +3676,6 @@ retry: 
			cfqq = &cfqd->oom_cfqq;

	}

out:

	if (new_cfqq)

		kmem_cache_free(cfq_pool, new_cfqq);



	rcu_read_unlock();

	return cfqq;

}
@@ -3723,7 +3700,7 @@ cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 


static struct cfq_queue *

cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,

	      struct bio *bio, gfp_t gfp_mask)

	      struct bio *bio)

{

	int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);

	int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
@@ -3742,7 +3719,7 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic, 
			goto out;

	}



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

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



	/*

	 * pin the queue now that it's allocated, scheduler exit will prune it
@@ -4286,8 +4263,6 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio, 
	const bool is_sync = rq_is_sync(rq);

	struct cfq_queue *cfqq;



	might_sleep_if(gfp_mask & __GFP_WAIT);



	spin_lock_irq(q->queue_lock);



	check_ioprio_changed(cic, bio);
@@ -4297,7 +4272,7 @@ new_queue: 
	if (!cfqq || cfqq == &cfqd->oom_cfqq) {

		if (cfqq)

			cfq_put_queue(cfqq);

		cfqq = cfq_get_queue(cfqd, is_sync, cic, bio, gfp_mask);

		cfqq = cfq_get_queue(cfqd, is_sync, cic, bio);

		cic_set_cfqq(cic, cfqq, is_sync);

	} else {

		/*

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