diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index d6355338f290..fee8c9d5dc2c 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -469,22 +469,17 @@ static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, { struct request_queue *q = disk->queue; struct blkcg_gq *blkg; - unsigned long flags; - WARN_ON_ONCE(!rcu_read_lock_held()); - - blkg = blkg_lookup(blkcg, q); - if (blkg) - return blkg; - - spin_lock_irqsave(&q->queue_lock, flags); + rcu_read_lock(); blkg = blkg_lookup(blkcg, q); if (blkg) { if (blkcg != &blkcg_root && blkg != rcu_dereference(blkcg->blkg_hint)) rcu_assign_pointer(blkcg->blkg_hint, blkg); - goto found; + rcu_read_unlock(); + return blkg; } + rcu_read_unlock(); /* * Create blkgs walking down from blkcg_root to @blkcg, so that all @@ -516,8 +511,6 @@ static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, break; } -found: - spin_unlock_irqrestore(&q->queue_lock, flags); return blkg; } @@ -2046,6 +2039,18 @@ void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta) atomic64_add(delta, &blkg->delay_nsec); } +static inline struct blkcg_gq *blkg_lookup_tryget(struct blkcg_gq *blkg) +{ +retry: + if (blkg_tryget(blkg)) + return blkg; + + blkg = blkg->parent; + if (blkg) + goto retry; + + return NULL; +} /** * blkg_tryget_closest - try and get a blkg ref on the closet blkg * @bio: target bio @@ -2058,20 +2063,30 @@ void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta) static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, struct cgroup_subsys_state *css) { - struct blkcg_gq *blkg, *ret_blkg = NULL; + struct request_queue *q = bio->bi_bdev->bd_queue; + struct blkcg *blkcg = css_to_blkcg(css); + struct blkcg_gq *blkg; rcu_read_lock(); - blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_bdev->bd_disk); - while (blkg) { - if (blkg_tryget(blkg)) { - ret_blkg = blkg; - break; - } - blkg = blkg->parent; - } + blkg = blkg_lookup(blkcg, q); + if (likely(blkg)) + blkg = blkg_lookup_tryget(blkg); rcu_read_unlock(); - return ret_blkg; + if (blkg) + return blkg; + + /* + * Fast path failed, we're probably issuing IO in this cgroup the first + * time, hold lock to create new blkg. + */ + spin_lock_irq(&q->queue_lock); + blkg = blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk); + if (blkg) + blkg = blkg_lookup_tryget(blkg); + spin_unlock_irq(&q->queue_lock); + + return blkg; } /**