From 13c7863d48c160152c42c62700a722293bddeca4 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Sat, 27 Jun 2020 09:31:54 +0200 Subject: block: move the initial blkg lookup into blkg_tryget_closest By moving the initial blkg lookup into blkg_tryget_closest we get a nicely self contained routines that does all the RCU locking. Acked-by: Tejun Heo Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-cgroup.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-) (limited to 'block/blk-cgroup.c') diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 0912820d4f81..d21ec2acd716 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1716,19 +1716,20 @@ void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta) /** * blkg_tryget_closest - try and get a blkg ref on the closet blkg - * @blkg: blkg to get + * @bio: target bio + * @css: target css * - * This needs to be called rcu protected. As the failure mode here is to walk - * up the blkg tree, this ensure that the blkg->parent pointers are always - * valid. This returns the blkg that it ended up taking a reference on or %NULL - * if no reference was taken. + * As the failure mode here is to walk up the blkg tree, this ensure that the + * blkg->parent pointers are always valid. This returns the blkg that it ended + * up taking a reference on or %NULL if no reference was taken. */ -static inline struct blkcg_gq *blkg_tryget_closest(struct blkcg_gq *blkg) +static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, + struct cgroup_subsys_state *css) { - struct blkcg_gq *ret_blkg = NULL; - - WARN_ON_ONCE(!rcu_read_lock_held()); + struct blkcg_gq *blkg, *ret_blkg = NULL; + rcu_read_lock(); + blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_disk->queue); while (blkg) { if (blkg_tryget(blkg)) { ret_blkg = blkg; @@ -1736,6 +1737,7 @@ static inline struct blkcg_gq *blkg_tryget_closest(struct blkcg_gq *blkg) } blkg = blkg->parent; } + rcu_read_unlock(); return ret_blkg; } @@ -1757,21 +1759,14 @@ static inline struct blkcg_gq *blkg_tryget_closest(struct blkcg_gq *blkg) void bio_associate_blkg_from_css(struct bio *bio, struct cgroup_subsys_state *css) { - struct request_queue *q = bio->bi_disk->queue; - if (bio->bi_blkg) blkg_put(bio->bi_blkg); if (css && css->parent) { - struct blkcg_gq *blkg; - - rcu_read_lock(); - blkg = blkg_lookup_create(css_to_blkcg(css), q); - bio->bi_blkg = blkg_tryget_closest(blkg); - rcu_read_unlock(); + bio->bi_blkg = blkg_tryget_closest(bio, css); } else { - blkg_get(q->root_blkg); - bio->bi_blkg = q->root_blkg; + blkg_get(bio->bi_disk->queue->root_blkg); + bio->bi_blkg = bio->bi_disk->queue->root_blkg; } } EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); -- cgit v1.2.3