diff options
| -rw-r--r-- | block/blk-cgroup.c | 42 | ||||
| -rw-r--r-- | block/blk-cgroup.h | 18 |
2 files changed, 55 insertions, 5 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 18ae480..942f344 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -201,7 +201,16 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, } blkg = new_blkg; - /* insert */ + /* link parent and insert */ + if (blkcg_parent(blkcg)) { + blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false); + if (WARN_ON_ONCE(!blkg->parent)) { + blkg = ERR_PTR(-EINVAL); + goto err_put_css; + } + blkg_get(blkg->parent); + } + spin_lock(&blkcg->lock); ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg); if (likely(!ret)) { @@ -213,6 +222,10 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, if (!ret) return blkg; + /* @blkg failed fully initialized, use the usual release path */ + blkg_put(blkg); + return ERR_PTR(ret); + err_put_css: css_put(&blkcg->css); err_free_blkg: @@ -226,8 +239,9 @@ err_free_blkg: * @q: request_queue of interest * * Lookup blkg for the @blkcg - @q pair. If it doesn't exist, try to - * create one. This function should be called under RCU read lock and - * @q->queue_lock. + * create one. blkg creation is performed recursively from blkcg_root such + * that all non-root blkg's have access to the parent blkg. This function + * should be called under RCU read lock and @q->queue_lock. * * Returns pointer to the looked up or created blkg on success, ERR_PTR() * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not @@ -252,7 +266,23 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, if (blkg) return blkg; - return blkg_create(blkcg, q, NULL); + /* + * Create blkgs walking down from blkcg_root to @blkcg, so that all + * non-root blkgs have access to their parents. + */ + while (true) { + struct blkcg *pos = blkcg; + struct blkcg *parent = blkcg_parent(blkcg); + + while (parent && !__blkg_lookup(parent, q, false)) { + pos = parent; + parent = blkcg_parent(parent); + } + + blkg = blkg_create(pos, q, NULL); + if (pos == blkcg || IS_ERR(blkg)) + return blkg; + } } EXPORT_SYMBOL_GPL(blkg_lookup_create); @@ -321,8 +351,10 @@ static void blkg_rcu_free(struct rcu_head *rcu_head) void __blkg_release(struct blkcg_gq *blkg) { - /* release the extra blkcg reference this blkg has been holding */ + /* release the blkcg and parent blkg refs this blkg has been holding */ css_put(&blkg->blkcg->css); + if (blkg->parent) + blkg_put(blkg->parent); /* * A group is freed in rcu manner. But having an rcu lock does not diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index 2459730..b26ed58 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -94,8 +94,13 @@ struct blkcg_gq { struct list_head q_node; struct hlist_node blkcg_node; struct blkcg *blkcg; + + /* all non-root blkcg_gq's are guaranteed to have access to parent */ + struct blkcg_gq *parent; + /* request allocation list for this blkcg-q pair */ struct request_list rl; + /* reference count */ int refcnt; @@ -181,6 +186,19 @@ static inline struct blkcg *bio_blkcg(struct bio *bio) } /** + * blkcg_parent - get the parent of a blkcg + * @blkcg: blkcg of interest + * + * Return the parent blkcg of @blkcg. Can be called anytime. + */ +static inline struct blkcg *blkcg_parent(struct blkcg *blkcg) +{ + struct cgroup *pcg = blkcg->css.cgroup->parent; + + return pcg ? cgroup_to_blkcg(pcg) : NULL; +} + +/** * blkg_to_pdata - get policy private data * @blkg: blkg of interest * @pol: policy of interest |
