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blkcg: always associate a bio with a blkg

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Previously, blkg's were only assigned as needed by blk-iolatency and
blk-throttle. bio->css was also always being associated while blkg was
being looked up and then thrown away in blkcg_bio_issue_check.

This patch begins the cleanup of bio->css and bio->bi_blkg by always
associating a blkg in blkcg_bio_issue_check. This tries to create the
blkg, but if it is not possible, falls back to using the root_blkg of
the request_queue. Therefore, a bio will always be associated with a
blkg. The duplicate association logic is removed from blk-throttle and
blk-iolatency.

Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dennis Zhou (Facebook) 2018-09-11 14:41:29 -04:00 • committed by Jens Axboe
parent 07b05bcc32
commit a7b39b4e96
5 changed files with 46 additions and 40 deletions
Download patch file Download diff file Expand all files Collapse all files

16
include/linux/blk-cgroup.h
View file

@ -900,29 +900,17 @@ static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg
static inline bool blkcg_bio_issue_check(struct request_queue *q,
struct bio *bio)
{
struct blkcg *blkcg;
struct blkcg_gq *blkg;
bool throtl = false;
rcu_read_lock();
/* 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);
}
bio_associate_create_blkg(q, bio);
blkg = bio->bi_blkg;
throtl = blk_throtl_bio(q, blkg, bio);
if (!throtl) {
blkg = blkg ?: q->root_blkg;
/*
* If the bio is flagged with BIO_QUEUE_ENTERED it means this
* is a split bio and we would have already accounted for the