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Commit b1929db4 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
parent 4b8b47eb

include/linux/cgroup.h

+1 −1
Original line number Diff line number Diff line
@@ -440,7 +440,7 @@ int cgroup_taskset_size(struct cgroup_taskset *tset); 


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);

kernel/cgroup.c

+19 −10
Original line number Diff line number Diff line
@@ -4041,14 +4041,18 @@ static void init_cgroup_css(struct cgroup_subsys_state *css, 
	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);

		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 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
	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 */

	for_each_subsys(root, ss)

		dget(dentry);



	/* creation succeeded, notify subsystems */

		online_css(ss, cgrp);

	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 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss) 
	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 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss) 
	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);

kernel/cgroup_freezer.c

+3 −1
Original line number Diff line number Diff line
@@ -112,7 +112,7 @@ static struct cgroup_subsys_state *freezer_create(struct cgroup *cgroup) 
 * 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 @@ static void freezer_post_create(struct cgroup *cgroup) 
	spin_unlock(&freezer->lock);

	if (parent)

		spin_unlock_irq(&parent->lock);



	return 0;

}



/**