diff options
Diffstat (limited to 'block/blk-cgroup.c')
| -rw-r--r-- | block/blk-cgroup.c | 103 |
1 files changed, 101 insertions, 2 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 0ecc897b225c..bb0607bfd771 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -328,7 +328,7 @@ err_free_blkg: * Returns the blkg or the closest blkg if blkg_create() fails as it walks * down from root. */ -struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, +static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, struct request_queue *q) { struct blkcg_gq *blkg; @@ -377,7 +377,7 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, * This looks up or creates the blkg representing the unique pair * of the blkcg and the request_queue. */ -struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, +static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, struct request_queue *q) { struct blkcg_gq *blkg = blkg_lookup(blkcg, q); @@ -1727,6 +1727,105 @@ void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta) atomic64_add(delta, &blkg->delay_nsec); } +/** + * blkg_tryget_closest - try and get a blkg ref on the closet blkg + * @blkg: blkg to get + * + * This needs to be called rcu protected. As the failure mode here is to walk + * up the blkg tree, this ensure that the blkg->parent pointers are always + * valid. This returns the blkg that it ended up taking a reference on or %NULL + * if no reference was taken. + */ +static inline struct blkcg_gq *blkg_tryget_closest(struct blkcg_gq *blkg) +{ + struct blkcg_gq *ret_blkg = NULL; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + while (blkg) { + if (blkg_tryget(blkg)) { + ret_blkg = blkg; + break; + } + blkg = blkg->parent; + } + + return ret_blkg; +} + +/** + * bio_associate_blkg_from_css - associate a bio with a specified css + * @bio: target bio + * @css: target css + * + * Associate @bio with the blkg found by combining the css's blkg and the + * request_queue of the @bio. An association failure is handled by walking up + * the blkg tree. Therefore, the blkg associated can be anything between @blkg + * and q->root_blkg. This situation only happens when a cgroup is dying and + * then the remaining bios will spill to the closest alive blkg. + * + * A reference will be taken on the blkg and will be released when @bio is + * freed. + */ +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) + blkg = blkg_lookup_create(css_to_blkcg(css), q); + bio->bi_blkg = blkg_tryget_closest(blkg); + rcu_read_unlock(); +} +EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); + +/** + * bio_associate_blkg - associate a bio with a blkg + * @bio: target bio + * + * Associate @bio with the blkg found from the bio's css and request_queue. + * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is + * already associated, the css is reused and association redone as the + * request_queue may have changed. + */ +void bio_associate_blkg(struct bio *bio) +{ + struct cgroup_subsys_state *css; + + rcu_read_lock(); + + if (bio->bi_blkg) + css = &bio_blkcg(bio)->css; + else + css = blkcg_css(); + + bio_associate_blkg_from_css(bio, css); + + rcu_read_unlock(); +} +EXPORT_SYMBOL_GPL(bio_associate_blkg); + +/** + * bio_clone_blkg_association - clone blkg association from src to dst bio + * @dst: destination bio + * @src: source bio + */ +void bio_clone_blkg_association(struct bio *dst, struct bio *src) +{ + if (src->bi_blkg) { + if (dst->bi_blkg) + blkg_put(dst->bi_blkg); + blkg_get(src->bi_blkg); + dst->bi_blkg = src->bi_blkg; + } +} +EXPORT_SYMBOL_GPL(bio_clone_blkg_association); + static int __init blkcg_init(void) { blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio", |