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 <[email protected]> Acked-by: Michal Hocko <[email protected]> Cc: Vladimir Davydov <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Tetsuo Handa <[email protected]> Cc: David Rientjes <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Tejun Heo <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] --- mm/memcontrol.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d5f3a62887cf..b4de17a78dc1 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
