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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
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

38
block/bio.c
View file

@ -2028,6 +2028,41 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
return 0;
}
/**
* bio_associate_create_blkg - associate a bio with a blkg from q
* @q: request_queue where bio is going
* @bio: target bio
*
* Associate @bio with the blkg found from the bio's css and the request_queue.
* If one is not found, bio_lookup_blkg creates the blkg.
*/
int bio_associate_create_blkg(struct request_queue *q, struct bio *bio)
{
struct blkcg *blkcg;
struct blkcg_gq *blkg;
int ret = 0;
/* someone has already associated this bio with a blkg */
if (bio->bi_blkg)
return ret;
rcu_read_lock();
bio_associate_blkcg(bio, NULL);
blkcg = bio_blkcg(bio);
if (!blkcg->css.parent) {
ret = bio_associate_blkg(bio, q->root_blkg);
} else {
blkg = blkg_lookup_create(blkcg, q);
ret = bio_associate_blkg(bio, blkg);
}
rcu_read_unlock();
return ret;
}
/**
* bio_disassociate_task - undo bio_associate_current()
* @bio: target bio
@ -2057,6 +2092,9 @@ void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
{
if (src->bi_css)
WARN_ON(bio_associate_blkcg(dst, src->bi_css));
if (src->bi_blkg)
bio_associate_blkg(dst, src->bi_blkg);
}
EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);
#endif /* CONFIG_BLK_CGROUP */

24
block/blk-iolatency.c
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) {

5
block/blk-throttle.c
View file

@ -2118,9 +2118,6 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)
static void blk_throtl_assoc_bio(struct throtl_grp *tg, struct bio *bio)
{
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
/* fallback to root_blkg if we fail to get a blkg ref */
if (bio->bi_css && (bio_associate_blkg(bio, tg_to_blkg(tg)) == -ENODEV))
bio_associate_blkg(bio, bio->bi_disk->queue->root_blkg);
bio_issue_init(&bio->bi_issue, bio_sectors(bio));
#endif
}
@ -2129,7 +2126,7 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
struct bio *bio)
{
struct throtl_qnode *qn = NULL;
struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_service_queue *sq;
bool rw = bio_data_dir(bio);
bool throttled = false;

3
include/linux/bio.h
View file

@ -542,11 +542,14 @@ static inline int bio_associate_blkcg_from_page(struct bio *bio,
#ifdef CONFIG_BLK_CGROUP
int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css);
int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg);
int bio_associate_create_blkg(struct request_queue *q, struct bio *bio);
void bio_disassociate_task(struct bio *bio);
void bio_clone_blkcg_association(struct bio *dst, struct bio *src);
#else /* CONFIG_BLK_CGROUP */
static inline int bio_associate_blkcg(struct bio *bio,
struct cgroup_subsys_state *blkcg_css) { return 0; }
static inline int bio_associate_create_blkg(struct request_queue *q,
struct bio *bio) { return 0; }
static inline void bio_disassociate_task(struct bio *bio) { }
static inline void bio_clone_blkcg_association(struct bio *dst,
struct bio *src) { }

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