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Commit 12a9d2fe authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: implement cgroup_rightmost_descendant() 



Implement cgroup_rightmost_descendant() which returns the right most
descendant of the specified cgroup.  This can be used to skip the
cgroup's subtree while iterating with
cgroup_for_each_descendant_pre().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent d5b1fe68

include/linux/cgroup.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -558,6 +558,7 @@ static inline struct cgroup* task_cgroup(struct task_struct *task, 




struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,

struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,

					  struct cgroup *cgroup);

					  struct cgroup *cgroup);

struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);





/**

/**

 * cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants

 * cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants

kernel/cgroup.c

+26 −0
Original line number Original line Diff line number Diff line
@@ -3017,6 +3017,32 @@ struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos, 
}

}

EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);

EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);





/**

 * cgroup_rightmost_descendant - return the rightmost descendant of a cgroup

 * @pos: cgroup of interest

 *

 * Return the rightmost descendant of @pos.  If there's no descendant,

 * @pos is returned.  This can be used during pre-order traversal to skip

 * subtree of @pos.

 */

struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos)

{

	struct cgroup *last, *tmp;



	WARN_ON_ONCE(!rcu_read_lock_held());



	do {

		last = pos;

		/* ->prev isn't RCU safe, walk ->next till the end */

		pos = NULL;

		list_for_each_entry_rcu(tmp, &last->children, sibling)

			pos = tmp;

	} while (pos);



	return last;

}

EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);



static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)

static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)

{

{

	struct cgroup *last;

	struct cgroup *last;