[RFC PATCH v2 1/7] mm, oom: refactor select_bad_process() to take memcg as an argument

[Roman Gushchin]

The select_bad_process() function will be used further
to select a process to kill in the victim cgroup.
This cgroup doesn't necessary match oc->memcg,
which is a cgroup, which limits were caused cgroup-wide OOM
(or NULL in case of global OOM).

So, refactor select_bad_process() to take a pointer to
a cgroup to iterate over as an argument.

Signed-off-by: Roman Gushchin <guro@xxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: kernel-team@xxxxxx
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
---
 mm/oom_kill.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 04c9143..f8b0fb1 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -343,10 +343,11 @@ static int oom_evaluate_task(struct task_struct *task, void *arg)
  * Simple selection loop. We choose the process with the highest number of
  * 'points'. In case scan was aborted, oc->chosen is set to -1.
  */
-static void select_bad_process(struct oom_control *oc)
+static void select_bad_process(struct oom_control *oc,
+			       struct mem_cgroup *memcg)
 {
-	if (is_memcg_oom(oc))
-		mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
+	if (memcg)
+		mem_cgroup_scan_tasks(memcg, oom_evaluate_task, oc);
 	else {
 		struct task_struct *p;
 
@@ -1032,7 +1033,7 @@ bool out_of_memory(struct oom_control *oc)
 		return true;
 	}
 
-	select_bad_process(oc);
+	select_bad_process(oc, oc->memcg);
 	/* Found nothing?!?! Either we hang forever, or we panic. */
 	if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
 		dump_header(oc, NULL);
-- 
2.7.4