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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: Tejun Heo <tj@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2020-06-27 09:31:49 +02:00 committed by Jens Axboe
parent d92c370a16
commit 2badf06cf9
1 changed files with 13 additions and 32 deletions
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45
block/bio.c
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@ -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;
if (bio->bi_blkg)
blkg_put(bio->bi_blkg);
rcu_read_lock();
if (!css || !css->parent)
blkg = q->root_blkg;
else
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);