Commit d93a11f1 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

blkcg, cfq-iosched: use GFP_NOWAIT instead of GFP_ATOMIC for non-critical allocations 



blkcg performs several allocations to track IOs per cgroup and enforce
resource control.  Most of these allocations are performed lazily on
demand in the IO path and thus can't involve reclaim path.  Currently,
these allocations use GFP_ATOMIC; however, blkcg can gracefully deal
with occassional failures of these allocations by punting IOs to the
root cgroup and there's no reason to reach into the emergency reserve.

This patch replaces GFP_ATOMIC with GFP_NOWAIT for the following
allocations.

* bdi_writeback_congested and blkcg_gq allocations in blkg_create().

* radix tree node allocations for blkcg->blkg_tree.

* cfq_queue allocation on ioprio changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Suggested-and-Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Suggested-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 563180a4

block/blk-cgroup.c

+4 −4
Original line number Diff line number Diff line
@@ -188,7 +188,7 @@ EXPORT_SYMBOL_GPL(blkg_lookup); 


/*

 * If @new_blkg is %NULL, this function tries to allocate a new one as

 * necessary using %GFP_ATOMIC.  @new_blkg is always consumed on return.

 * necessary using %GFP_NOWAIT.  @new_blkg is always consumed on return.

 */

static struct blkcg_gq *blkg_create(struct blkcg *blkcg,

				    struct request_queue *q,
@@ -208,7 +208,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, 
	}



	wb_congested = wb_congested_get_create(&q->backing_dev_info,

					       blkcg->css.id, GFP_ATOMIC);

					       blkcg->css.id, GFP_NOWAIT);

	if (!wb_congested) {

		ret = -ENOMEM;

		goto err_put_css;
@@ -216,7 +216,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, 


	/* allocate */

	if (!new_blkg) {

		new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);

		new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT);

		if (unlikely(!new_blkg)) {

			ret = -ENOMEM;

			goto err_put_congested;
@@ -882,7 +882,7 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css) 


done:

	spin_lock_init(&blkcg->lock);

	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);

	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);

	INIT_HLIST_HEAD(&blkcg->blkg_list);

#ifdef CONFIG_CGROUP_WRITEBACK

	INIT_LIST_HEAD(&blkcg->cgwb_list);

block/cfq-iosched.c

+1 −1
Original line number Diff line number Diff line
@@ -3575,7 +3575,7 @@ 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_ATOMIC);

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

		cic_set_cfqq(cic, cfqq, false);

	}

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