cgroup: add/update accessors which obtain subsys specific data from css

[deliverable/linux.git] / block / blk-cgroup.h

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 4e595ee8c9151aea5c0005bffbe1d936c4603083..8e5863e900bf1a2cc2f4c18dca0b2e2703f74e42 100644 (file)
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -179,22 +179,25 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 void blkg_conf_finish(struct blkg_conf_ctx *ctx);
 
 
+static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
+{
+       return css ? container_of(css, struct blkcg, css) : NULL;
+}
+
 static inline struct blkcg *cgroup_to_blkcg(struct cgroup *cgroup)
 {
-       return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
-                           struct blkcg, css);
+       return css_to_blkcg(cgroup_css(cgroup, blkio_subsys_id));
 }
 
 static inline struct blkcg *task_blkcg(struct task_struct *tsk)
 {
-       return container_of(task_subsys_state(tsk, blkio_subsys_id),
-                           struct blkcg, css);
+       return css_to_blkcg(task_css(tsk, blkio_subsys_id));
 }
 
 static inline struct blkcg *bio_blkcg(struct bio *bio)
 {
        if (bio && bio->bi_css)
-               return container_of(bio->bi_css, struct blkcg, css);
+               return css_to_blkcg(bio->bi_css);
        return task_blkcg(current);
 }
 
@@ -266,7 +269,7 @@ static inline void blkg_get(struct blkcg_gq *blkg)
        blkg->refcnt++;
 }
 
-void __blkg_release(struct blkcg_gq *blkg);
+void __blkg_release_rcu(struct rcu_head *rcu);
 
 /**
  * blkg_put - put a blkg reference
@@ -279,9 +282,43 @@ static inline void blkg_put(struct blkcg_gq *blkg)
        lockdep_assert_held(blkg->q->queue_lock);
        WARN_ON_ONCE(blkg->refcnt <= 0);
        if (!--blkg->refcnt)
-               __blkg_release(blkg);
+               call_rcu(&blkg->rcu_head, __blkg_release_rcu);
 }
 
+struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
+                              bool update_hint);
+
+/**
+ * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
+ * @d_blkg: loop cursor pointing to the current descendant
+ * @pos_cgrp: used for iteration
+ * @p_blkg: target blkg to walk descendants of
+ *
+ * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
+ * read locked.  If called under either blkcg or queue lock, the iteration
+ * is guaranteed to include all and only online blkgs.  The caller may
+ * update @pos_cgrp by calling cgroup_rightmost_descendant() to skip
+ * subtree.
+ */
+#define blkg_for_each_descendant_pre(d_blkg, pos_cgrp, p_blkg)         \
+       cgroup_for_each_descendant_pre((pos_cgrp), (p_blkg)->blkcg->css.cgroup) \
+               if (((d_blkg) = __blkg_lookup(cgroup_to_blkcg(pos_cgrp), \
+                                             (p_blkg)->q, false)))
+
+/**
+ * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
+ * @d_blkg: loop cursor pointing to the current descendant
+ * @pos_cgrp: used for iteration
+ * @p_blkg: target blkg to walk descendants of
+ *
+ * Similar to blkg_for_each_descendant_pre() but performs post-order
+ * traversal instead.  Synchronization rules are the same.
+ */
+#define blkg_for_each_descendant_post(d_blkg, pos_cgrp, p_blkg)                \
+       cgroup_for_each_descendant_post((pos_cgrp), (p_blkg)->blkcg->css.cgroup) \
+               if (((d_blkg) = __blkg_lookup(cgroup_to_blkcg(pos_cgrp), \
+                                             (p_blkg)->q, false)))
+
 /**
  * blk_get_rl - get request_list to use
  * @q: request_queue of interest