Implement mem_cgroup_scan_tasks() functionality for the root
memory cgroup to use this function for looking for a OOM victim
task in the root memory cgroup by the cgroup-ware OOM killer.
The root memory cgroup is treated as a leaf cgroup, so only tasks
which are directly belonging to the root cgroup are iterated over.
This patch doesn't introduce any functional change as
mem_cgroup_scan_tasks() is never called for the root memcg.
This is preparatory work for the cgroup-aware OOM killer,
which will use this function to iterate over tasks belonging
to the root memcg.
Signed-off-by: Roman Gushchin <g...@fb.com>
Acked-by: Michal Hocko <mho...@suse.com>
Cc: Vladimir Davydov <vdavydov....@gmail.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Cc: David Rientjes <rient...@google.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Tejun Heo <t...@kernel.org>
Cc: kernel-t...@fb.com
Cc: cgro...@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
Cc: linux...@kvack.org
---
mm/memcontrol.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c7410636fadf..41d71f665550 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -917,7 +917,8 @@ static void invalidate_reclaim_iterators(struct mem_cgroup
*dead_memcg)
* value, the function breaks the iteration loop and returns the value.
* Otherwise, it will iterate over all tasks and return 0.
*
- * This function must not be called for the root memory cgroup.
+ * If memcg is the root memory cgroup, this function will iterate only
+ * over tasks belonging directly to the root memory cgroup.
*/
int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
int (*fn)(struct task_struct *, void *), void *arg)
@@ -925,8 +926,6 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
struct mem_cgroup *iter;
int ret = 0;
- BUG_ON(memcg == root_mem_cgroup);
-
for_each_mem_cgroup_tree(iter, memcg) {
struct css_task_iter it;
struct task_struct *task;
@@ -935,7 +934,7 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
while (!ret && (task = css_task_iter_next(&it)))
ret = fn(task, arg);
css_task_iter_end(&it);
- if (ret) {
+ if (ret || memcg == root_mem_cgroup) {
mem_cgroup_iter_break(memcg, iter);
break;
}
--
2.13.6
--
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