From beea9da07d8a6228a7e4a31a83f9478d513bf03f Mon Sep 17 00:00:00 2001 From: Dennis Zhou Date: Wed, 5 Dec 2018 12:10:28 -0500 Subject: blkcg: convert blkg_lookup_create() to find closest blkg There are several scenarios where blkg_lookup_create() can fail such as the blkcg dying, request_queue is dying, or simply being OOM. Most handle this by simply falling back to the q->root_blkg and calling it a day. This patch implements the notion of closest blkg. During blkg_lookup_create(), if it fails to create, return the closest blkg found or the q->root_blkg. blkg_try_get_closest() is introduced and used during association so a bio is always attached to a blkg. Signed-off-by: Dennis Zhou Acked-by: Tejun Heo Reviewed-by: Josef Bacik Signed-off-by: Jens Axboe --- include/linux/blk-cgroup.h | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) (limited to 'include/linux') diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index b3b1a8187d23..c08e96e521ed 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -545,6 +545,20 @@ static inline struct blkcg_gq *blkg_try_get(struct blkcg_gq *blkg) return NULL; } +/** + * blkg_try_get_closest - try and get a blkg ref on the closet blkg + * @blkg: blkg to get + * + * This walks up the blkg tree to find the closest non-dying blkg and returns + * the blkg that it did association with as it may not be the passed in blkg. + */ +static inline struct blkcg_gq *blkg_try_get_closest(struct blkcg_gq *blkg) +{ + while (!atomic_inc_not_zero(&blkg->refcnt)) + blkg = blkg->parent; + + return blkg; +} void __blkg_release_rcu(struct rcu_head *rcu); @@ -797,15 +811,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q, /* associate blkcg if bio hasn't attached one */ bio_associate_blkcg(bio, NULL); blkcg = bio_blkcg(bio); - - blkg = blkg_lookup(blkcg, q); - if (unlikely(!blkg)) { - spin_lock_irq(&q->queue_lock); - blkg = __blkg_lookup_create(blkcg, q); - if (IS_ERR(blkg)) - blkg = NULL; - spin_unlock_irq(&q->queue_lock); - } + blkg = blkg_lookup_create(blkcg, q); throtl = blk_throtl_bio(q, blkg, bio); -- cgit v1.2.3-71-gd317