blkcg: always associate a bio with a blkg

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 <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Dennis Zhou (Facebook) 2018-09-11 14:41:29 -04:00 • committed by Jens Axboe
commit a7b39b4e96
5 changed files with 46 additions and 40 deletions

View file

@ -392,34 +392,14 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio,
spinlock_t *lock)
{
struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
struct blkcg *blkcg;
struct blkcg_gq *blkg;
struct request_queue *q = rqos->q;
struct blkcg_gq *blkg = bio->bi_blkg;
bool issue_as_root = bio_issue_as_root_blkg(bio);
if (!blk_iolatency_enabled(blkiolat))
return;
rcu_read_lock();
bio_associate_blkcg(bio, NULL);
blkcg = bio_blkcg(bio);
blkg = blkg_lookup(blkcg, q);
if (unlikely(!blkg)) {
if (!lock)
spin_lock_irq(q->queue_lock);
blkg = __blkg_lookup_create(blkcg, q);
if (IS_ERR(blkg))
blkg = NULL;
if (!lock)
spin_unlock_irq(q->queue_lock);
}
if (!blkg)
goto out;
bio_issue_init(&bio->bi_issue, bio_sectors(bio));
bio_associate_blkg(bio, blkg);
out:
rcu_read_unlock();
while (blkg && blkg->parent) {
struct iolatency_grp *iolat = blkg_to_lat(blkg);
if (!iolat) {