cgroup: use RCU free in create_css() failure path (a2bed820) · Commits · 戴 / test

Currently, when create_css() fails in the middle, the half-initialized css is freed by invoking cgroup_subsys->css_free() directly. This patch updates the function so that it invokes RCU free path instead. As the RCU free path puts the parent css and owning cgroup, their references are now acquired right after a new css is successfully allocated. This doesn't make any visible difference now but is to enable implementing css->id and RCU protected lookup by such IDs. Signed-off-by:

Tejun Heo <tj@kernel.org> Acked-by:

Li Zefan <lizefan@huawei.com>

kernel/cgroup.c

+5 −6

Original line number	Diff line number	Diff line
		@@ -4185,12 +4185,14 @@ static int create_css(struct cgroup cgrp, struct cgroup_subsys ss)
		if (IS_ERR(css))
		return PTR_ERR(css);

		init_css(css, ss, cgrp);
		cgroup_get(cgrp);
		css_get(css->parent);

		err = percpu_ref_init(&css->refcnt, css_release);
		if (err)
		goto err_free_css;

		init_css(css, ss, cgrp);

		err = cgroup_populate_dir(cgrp, 1 << ss->id);
		if (err)
		goto err_free_percpu_ref;
		@@ -4199,9 +4201,6 @@ static int create_css(struct cgroup cgrp, struct cgroup_subsys ss)
		if (err)
		goto err_clear_dir;

		cgroup_get(cgrp);
		css_get(css->parent);

		if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
		parent->parent) {
		pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
		@@ -4218,7 +4217,7 @@ err_clear_dir:
		err_free_percpu_ref:
		percpu_ref_cancel_init(&css->refcnt);
		err_free_css:
		ss->css_free(css);
		call_rcu(&css->rcu_head, css_free_rcu_fn);
		return err;
		}

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