From a7b39b4e961c4e2b3ed837803a7441a65c90ce33 Mon Sep 17 00:00:00 2001 From: "Dennis Zhou (Facebook)" Date: Tue, 11 Sep 2018 14:41:29 -0400 Subject: 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 Acked-by: Tejun Heo Signed-off-by: Jens Axboe --- block/bio.c | 38 ++++++++++++++++++++++++++++++++++++++ block/blk-iolatency.c | 24 ++---------------------- block/blk-throttle.c | 5 +---- 3 files changed, 41 insertions(+), 26 deletions(-) (limited to 'block') diff --git a/block/bio.c b/block/bio.c index bfd41e8b53a8..748d7132f172 100644 --- a/block/bio.c +++ b/block/bio.c @@ -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 */ diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index ffde3ab9f84c..7337fbc7f850 100644 --- a/block/blk-iolatency.c +++ b/block/blk-iolatency.c @@ -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) { diff --git a/block/blk-throttle.c b/block/blk-throttle.c index db1a3a2ae006..e62ae502891b 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -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; -- cgit