From a5b97526bf2860fe8306959f19ee428d1f5cc732 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Sat, 27 Jun 2020 09:31:53 +0200 Subject: block: bypass blkg_tryget_closest for the root_blkg The root_blkg is only torn down at the very end of removing a queue. So in the I/O submission path is always has a life reference and we can just grab another one using blkg_get instead of doing a tryget and parent walk that won't lead anywhere. Acked-by: Tejun Heo Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-cgroup.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) (limited to 'block/blk-cgroup.c') diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 6aedb73ffbf4..0912820d4f81 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1758,16 +1758,21 @@ 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 = q->root_blkg; if (bio->bi_blkg) blkg_put(bio->bi_blkg); - rcu_read_lock(); - if (css && css->parent) + 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(blkg); + rcu_read_unlock(); + } else { + blkg_get(q->root_blkg); + bio->bi_blkg = q->root_blkg; + } } EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); -- cgit v1.2.3