Commit 2badf06c authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: merge __bio_associate_blkg into bio_associate_blkg_from_css 



Merge __bio_associate_blkg into the only caller, which allows to slightly
reduce the RCU crticial section and better explain the code flow.

Acked-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d92c370a

block/bio.c

+13 −32
Original line number Diff line number Diff line
@@ -1628,52 +1628,33 @@ int bioset_init_from_src(struct bio_set *bs, struct bio_set *src) 
EXPORT_SYMBOL(bioset_init_from_src);



#ifdef CONFIG_BLK_CGROUP



/**

 * __bio_associate_blkg - associate a bio with the a blkg

 * @bio: target bio

 * @blkg: the blkg to associate

 *

 * This tries to associate @bio with the specified @blkg.  Association failure

 * is handled by walking up the blkg tree.  Therefore, the blkg associated can

 * be anything between @blkg and the root_blkg.  This situation only happens

 * when a cgroup is dying and then the remaining bios will spill to the closest

 * alive blkg.

 *

 * A reference will be taken on the @blkg and will be released when @bio is

 * freed.

 */

static void __bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)

{

	if (bio->bi_blkg)

		blkg_put(bio->bi_blkg);

	bio->bi_blkg = blkg_tryget_closest(blkg);

}



/**

 * bio_associate_blkg_from_css - associate a bio with a specified css

 * @bio: target bio

 * @css: target css

 *

 * Associate @bio with the blkg found by combining the css's blkg and the

 * request_queue of the @bio.  This falls back to the queue's root_blkg if

 * the association fails with the css.

 * request_queue of the @bio.  An association failure is handled by walking up

 * the blkg tree.  Therefore, the blkg associated can be anything between @blkg

 * and q->root_blkg.  This situation only happens when a cgroup is dying and

 * then the remaining bios will spill to the closest alive blkg.

 *

 * A reference will be taken on the blkg and will be released when @bio is

 * freed.

 */

void bio_associate_blkg_from_css(struct bio *bio,

				 struct cgroup_subsys_state *css)

{

	struct request_queue *q = bio->bi_disk->queue;

	struct blkcg_gq *blkg;

	struct blkcg_gq *blkg = q->root_blkg;



	rcu_read_lock();

	if (bio->bi_blkg)

		blkg_put(bio->bi_blkg);



	if (!css || !css->parent)

		blkg = q->root_blkg;

	else

	rcu_read_lock();

	if (css && css->parent)

		blkg = blkg_lookup_create(css_to_blkcg(css), q);



	__bio_associate_blkg(bio, blkg);



	bio->bi_blkg = blkg_tryget_closest(blkg);

	rcu_read_unlock();

}

EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);