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Subject[PATCH 04/14] block: merge __bio_associate_blkg into bio_associate_blkg_from_css
Date
Merge __bio_associate_blkg into the only caller, which allows to slightly
reduce the RCU crticial section and better explain the code flow.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/bio.c | 45 +++++++++++++--------------------------------
1 file changed, 13 insertions(+), 32 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index e1d01acce8070c..bc8de2432e3645 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -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);
--
2.26.2
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