cgroup: allow ->post_create() to fail
There could be cases where controllers want to do initialization
operations which may fail from ->post_create(). This patch makes
->post_create() return -errno to indicate failure and online_css()
relay such failures.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index f4a9c98..03d8a92 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -440,7 +440,7 @@
struct cgroup_subsys {
struct cgroup_subsys_state *(*create)(struct cgroup *cgrp);
- void (*post_create)(struct cgroup *cgrp);
+ int (*post_create)(struct cgroup *cgrp);
void (*pre_destroy)(struct cgroup *cgrp);
void (*destroy)(struct cgroup *cgrp);
int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 027b66e..c389f42 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4041,14 +4041,18 @@
INIT_WORK(&css->dput_work, css_dput_fn);
}
-/* invoke ->post_create() on a new CSS and mark it online */
-static void online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
+/* invoke ->post_create() on a new CSS and mark it online if successful */
+static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
{
+ int ret = 0;
+
lockdep_assert_held(&cgroup_mutex);
if (ss->post_create)
- ss->post_create(cgrp);
- cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
+ ret = ss->post_create(cgrp);
+ if (!ret)
+ cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
+ return ret;
}
/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
@@ -4174,12 +4178,15 @@
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
root->number_of_cgroups++;
- for_each_subsys(root, ss) {
- /* each css holds a ref to the cgroup's dentry */
+ /* each css holds a ref to the cgroup's dentry */
+ for_each_subsys(root, ss)
dget(dentry);
- /* creation succeeded, notify subsystems */
- online_css(ss, cgrp);
+ /* creation succeeded, notify subsystems */
+ for_each_subsys(root, ss) {
+ err = online_css(ss, cgrp);
+ if (err)
+ goto err_destroy;
}
err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
@@ -4393,7 +4400,7 @@
BUG_ON(!list_empty(&init_task.tasks));
ss->active = 1;
- online_css(ss, dummytop);
+ BUG_ON(online_css(ss, dummytop));
mutex_unlock(&cgroup_mutex);
@@ -4500,7 +4507,9 @@
write_unlock(&css_set_lock);
ss->active = 1;
- online_css(ss, dummytop);
+ ret = online_css(ss, dummytop);
+ if (ret)
+ goto err_unload;
/* success! */
mutex_unlock(&cgroup_mutex);
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 670a4af..ee8bb67 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -112,7 +112,7 @@
* parent's freezing state while holding both parent's and our
* freezer->lock.
*/
-static void freezer_post_create(struct cgroup *cgroup)
+static int freezer_post_create(struct cgroup *cgroup)
{
struct freezer *freezer = cgroup_freezer(cgroup);
struct freezer *parent = parent_freezer(freezer);
@@ -136,6 +136,8 @@
spin_unlock(&freezer->lock);
if (parent)
spin_unlock_irq(&parent->lock);
+
+ return 0;
}
/**