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authorChristoph Hellwig <hch@lst.de>2020-06-27 09:31:53 +0200
committerJens Axboe <axboe@kernel.dk>2020-06-29 17:09:08 +0200
commita5b97526bf2860fe8306959f19ee428d1f5cc732 (patch)
tree8f3c46c26cb255774957970073be840bdc23af9f /block/blk-cgroup.c
parentblock: merge blkg_lookup_create and __blkg_lookup_create (diff)
downloadlinux-a5b97526bf2860fe8306959f19ee428d1f5cc732.tar.xz
linux-a5b97526bf2860fe8306959f19ee428d1f5cc732.zip
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 <tj@kernel.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-cgroup.c')
-rw-r--r--block/blk-cgroup.c15
1 files changed, 10 insertions, 5 deletions
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);