blk-cgroup: Fix an RCU warning in blkiocg_create()

[safe/jmp/linux-2.6] / block / blk-cgroup.c

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3ad497f..2cc682b 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -14,6 +14,8 @@
 #include <linux/seq_file.h>
 #include <linux/kdev_t.h>
 #include <linux/module.h>
+#include <linux/err.h>
+#include <linux/slab.h>
 #include "blk-cgroup.h"
 
 static DEFINE_SPINLOCK(blkio_list_lock);
@@ -22,19 +24,30 @@ static LIST_HEAD(blkio_list);
 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
-bool blkiocg_css_tryget(struct blkio_cgroup *blkcg)
-{
-       if (!css_tryget(&blkcg->css))
-               return false;
-       return true;
-}
-EXPORT_SYMBOL_GPL(blkiocg_css_tryget);
+static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
+                                                 struct cgroup *);
+static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
+                             struct task_struct *, bool);
+static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
+                          struct cgroup *, struct task_struct *, bool);
+static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
+static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 
-void blkiocg_css_put(struct blkio_cgroup *blkcg)
-{
-       css_put(&blkcg->css);
-}
-EXPORT_SYMBOL_GPL(blkiocg_css_put);
+struct cgroup_subsys blkio_subsys = {
+       .name = "blkio",
+       .create = blkiocg_create,
+       .can_attach = blkiocg_can_attach,
+       .attach = blkiocg_attach,
+       .destroy = blkiocg_destroy,
+       .populate = blkiocg_populate,
+#ifdef CONFIG_BLK_CGROUP
+       /* note: blkio_subsys_id is otherwise defined in blk-cgroup.h */
+       .subsys_id = blkio_subsys_id,
+#endif
+       .use_id = 1,
+       .module = THIS_MODULE,
+};
+EXPORT_SYMBOL_GPL(blkio_subsys);
 
 struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 {
@@ -146,16 +159,16 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
                return -EINVAL;
 
        blkcg = cgroup_to_blkio_cgroup(cgroup);
+       spin_lock(&blkio_list_lock);
        spin_lock_irq(&blkcg->lock);
        blkcg->weight = (unsigned int)val;
        hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
-               spin_lock(&blkio_list_lock);
                list_for_each_entry(blkiop, &blkio_list, list)
                        blkiop->ops.blkio_update_group_weight_fn(blkg,
                                        blkcg->weight);
-               spin_unlock(&blkio_list_lock);
        }
        spin_unlock_irq(&blkcg->lock);
+       spin_unlock(&blkio_list_lock);
        return 0;
 }
 
@@ -266,22 +279,23 @@ remove_entry:
 done:
        free_css_id(&blkio_subsys, &blkcg->css);
        rcu_read_unlock();
-       kfree(blkcg);
+       if (blkcg != &blkio_root_cgroup)
+               kfree(blkcg);
 }
 
 static struct cgroup_subsys_state *
 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 {
-       struct blkio_cgroup *blkcg, *parent_blkcg;
+       struct blkio_cgroup *blkcg;
+       struct cgroup *parent = cgroup->parent;
 
-       if (!cgroup->parent) {
+       if (!parent) {
                blkcg = &blkio_root_cgroup;
                goto done;
        }
 
        /* Currently we do not support hierarchy deeper than two level (0,1) */
-       parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
-       if (css_depth(&parent_blkcg->css) > 0)
+       if (parent != cgroup->top_cgroup)
                return ERR_PTR(-EINVAL);
 
        blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
@@ -332,17 +346,6 @@ static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
        task_unlock(tsk);
 }
 
-struct cgroup_subsys blkio_subsys = {
-       .name = "blkio",
-       .create = blkiocg_create,
-       .can_attach = blkiocg_can_attach,
-       .attach = blkiocg_attach,
-       .destroy = blkiocg_destroy,
-       .populate = blkiocg_populate,
-       .subsys_id = blkio_subsys_id,
-       .use_id = 1,
-};
-
 void blkio_policy_register(struct blkio_policy_type *blkiop)
 {
        spin_lock(&blkio_list_lock);
@@ -358,3 +361,17 @@ void blkio_policy_unregister(struct blkio_policy_type *blkiop)
        spin_unlock(&blkio_list_lock);
 }
 EXPORT_SYMBOL_GPL(blkio_policy_unregister);
+
+static int __init init_cgroup_blkio(void)
+{
+       return cgroup_load_subsys(&blkio_subsys);
+}
+
+static void __exit exit_cgroup_blkio(void)
+{
+       cgroup_unload_subsys(&blkio_subsys);
+}
+
+module_init(init_cgroup_blkio);
+module_exit(exit_cgroup_blkio);
+MODULE_LICENSE("GPL");