Commit d19e19de authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: simplify cgroup_load_subsys() failure path 



Now that cgroup_unload_subsys() can tell whether the root css is
online or not, we can safely call cgroup_unload_subsys() after idr
init failure in cgroup_load_subsys().

Replace the manual unrolling and invoke cgroup_unload_subsys() on
failure.  This drops cgroup_mutex inbetween but should be safe as the
subsystem will fail try_module_get() and thus can't be mounted
inbetween.  As this means that cgroup_unload_subsys() can be called
before css_sets are rehashed, remove BUG_ON() on %NULL
css_set->subsys[] from cgroup_unload_subsys().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent a31f2d3f

kernel/cgroup.c

+10 −11
Original line number Diff line number Diff line
@@ -4400,8 +4400,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss) 
 */

int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)

{

	int i;

	struct cgroup_subsys_state *css;

	int i, ret;



	/* check name and function validity */

	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
@@ -4452,15 +4452,9 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss) 
	init_cgroup_css(css, ss, dummytop);

	/* init_idr must be after init_cgroup_css because it sets css->id. */

	if (ss->use_id) {

		int ret = cgroup_init_idr(ss, css);

		if (ret) {

			ss->destroy(dummytop);

			dummytop->subsys[ss->subsys_id] = NULL;

			subsys[ss->subsys_id] = NULL;

			list_del_init(&ss->sibling);

			mutex_unlock(&cgroup_mutex);

			return ret;

		}

		ret = cgroup_init_idr(ss, css);

		if (ret)

			goto err_unload;

	}



	/*
@@ -4498,6 +4492,12 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss) 
	/* success! */

	mutex_unlock(&cgroup_mutex);

	return 0;



err_unload:

	mutex_unlock(&cgroup_mutex);

	/* @ss can't be mounted here as try_module_get() would fail */

	cgroup_unload_subsys(ss);

	return ret;

}

EXPORT_SYMBOL_GPL(cgroup_load_subsys);
@@ -4548,7 +4548,6 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss) 
		struct css_set *cg = link->cg;



		hlist_del(&cg->hlist);

		BUG_ON(!cg->subsys[ss->subsys_id]);

		cg->subsys[ss->subsys_id] = NULL;

		hhead = css_set_hash(cg->subsys);

		hlist_add_head(&cg->hlist, hhead);

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