---

yaml --- r: 251157 b: refs/heads/master c: 4843c69 h: refs/heads/master i: 251155: e7d8ed9 v: v3
git-mirror · May 20, 2011 · 730f361 · 730f361
1 parent 8d3e553
commit 730f361
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Showing 2 changed files with 22 additions and 2 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5617cbef7723952cbdff28c7a10ff8a254945f4f
+refs/heads/master: 4843c69d496a8d2e4caab6182fe016b9a79136e0
diff --git a/trunk/block/blk-throttle.c b/trunk/block/blk-throttle.c
@@ -78,6 +78,8 @@ struct throtl_grp {
 
 	/* Some throttle limits got updated for the group */
 	int limits_changed;
+
+	struct rcu_head rcu_head;
 };
 
 struct throtl_data
@@ -151,12 +153,30 @@ static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
 	return tg;
 }
 
+static void throtl_free_tg(struct rcu_head *head)
+{
+	struct throtl_grp *tg;
+
+	tg = container_of(head, struct throtl_grp, rcu_head);
+	kfree(tg);
+}
+
 static void throtl_put_tg(struct throtl_grp *tg)
 {
 	BUG_ON(atomic_read(&tg->ref) <= 0);
 	if (!atomic_dec_and_test(&tg->ref))
 		return;
-	kfree(tg);
+
+	/*
+	 * A group is freed in rcu manner. But having an rcu lock does not
+	 * mean that one can access all the fields of blkg and assume these
+	 * are valid. For example, don't try to follow throtl_data and
+	 * request queue links.
+	 *
+	 * Having a reference to blkg under an rcu allows acess to only
+	 * values local to groups like group stats and group rate limits
+	 */
+	call_rcu(&tg->rcu_head, throtl_free_tg);
 }
 
 static void throtl_init_group(struct throtl_grp *tg)