[PATCH 12/14] cgroup: convert cgroup_has_live_children() into css_has_online_children()

Tejun Heo
2014-05-09T21:32:57Z

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: Tejun Heo <tj@kernel.org>
---
include/linux/cgroup.h | 2 ++
kernel/cgroup.c | 32 ++++++++++++++++++++------------
2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 2cf2063..c8eb66e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -868,6 +868,8 @@ 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;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a0cfe36..0b16631 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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);
@@ -1768,7 +1767,7 @@ 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);
@@ -3290,19 +3289,28 @@ 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;
}

/**
@@ -4534,7 +4542,7 @@ 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;

/*
@@ -5006,8 +5014,8 @@ 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
--
1.9.0