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Commit f3d46500 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: convert cgroup_has_live_children() into css_has_online_children() 



Now that cgroup liveliness and css onliness are the same state,
convert cgroup_has_live_children() into css_has_online_children() so
that it can be used for actual csses too.  The function now uses
css_for_each_child() for iteration and is published.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 184faf32

include/linux/cgroup.h

+2 −0
Original line number Diff line number Diff line
@@ -873,6 +873,8 @@ css_next_descendant_post(struct cgroup_subsys_state *pos, 
	for ((pos) = css_next_descendant_post(NULL, (css)); (pos);	\

	     (pos) = css_next_descendant_post((pos), (css)))



bool css_has_online_children(struct cgroup_subsys_state *css);



/* A css_task_iter should be treated as an opaque object */

struct css_task_iter {

	struct cgroup_subsys		*ss;

kernel/cgroup.c

+20 −12
Original line number Diff line number Diff line
@@ -175,7 +175,6 @@ static int need_forkexit_callback __read_mostly; 
static struct cftype cgroup_base_files[];



static void cgroup_put(struct cgroup *cgrp);

static bool cgroup_has_live_children(struct cgroup *cgrp);

static int rebind_subsystems(struct cgroup_root *dst_root,

			     unsigned int ss_mask);

static int cgroup_destroy_locked(struct cgroup *cgrp);
@@ -1769,7 +1768,7 @@ static void cgroup_kill_sb(struct super_block *sb) 
	 * This prevents new mounts by disabling percpu_ref_tryget_live().

	 * cgroup_mount() may wait for @root's release.

	 */

	if (cgroup_has_live_children(&root->cgrp))

	if (css_has_online_children(&root->cgrp.self))

		cgroup_put(&root->cgrp);

	else

		percpu_ref_kill(&root->cgrp.self.refcnt);
@@ -3291,19 +3290,28 @@ css_next_descendant_post(struct cgroup_subsys_state *pos, 
	return pos->parent;

}



static bool cgroup_has_live_children(struct cgroup *cgrp)

/**

 * css_has_online_children - does a css have online children

 * @css: the target css

 *

 * Returns %true if @css has any online children; otherwise, %false.  This

 * function can be called from any context but the caller is responsible

 * for synchronizing against on/offlining as necessary.

 */

bool css_has_online_children(struct cgroup_subsys_state *css)

{

	struct cgroup *child;

	struct cgroup_subsys_state *child;

	bool ret = false;



	rcu_read_lock();

	list_for_each_entry_rcu(child, &cgrp->self.children, self.sibling) {

		if (!cgroup_is_dead(child)) {

			rcu_read_unlock();

			return true;

	css_for_each_child(child, css) {

		if (css->flags & CSS_ONLINE) {

			ret = true;

			break;

		}

	}

	rcu_read_unlock();

	return false;

	return ret;

}



/**
@@ -4535,7 +4543,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) 
	 * ->self.children as dead children linger on it while being

	 * drained; otherwise, "rmdir parent/child parent" may fail.

	 */

	if (cgroup_has_live_children(cgrp))

	if (css_has_online_children(&cgrp->self))

		return -EBUSY;



	/*
@@ -5014,8 +5022,8 @@ void cgroup_exit(struct task_struct *tsk) 


static void check_for_release(struct cgroup *cgrp)

{

	if (cgroup_is_releasable(cgrp) &&

	    list_empty(&cgrp->cset_links) && !cgroup_has_live_children(cgrp)) {

	if (cgroup_is_releasable(cgrp) && list_empty(&cgrp->cset_links) &&

	    !css_has_online_children(&cgrp->self)) {

		/*

		 * Control Group is currently removeable. If it's not

		 * already queued for a userspace notification, queue