Introduce a per-memory-cgroup oom_score_adj setting.
A read-write single value file which exits on non-root
cgroups. The default is "0".

It will have a similar meaning to a per-process value,
available via /proc/<pid>/oom_score_adj.
Should be in a range [-1000, 1000].

Signed-off-by: Roman Gushchin <g...@fb.com>
Cc: Michal Hocko <mho...@kernel.org>
Cc: Vladimir Davydov <vdavydov....@gmail.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Tejun Heo <t...@kernel.org>
Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
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
---
 include/linux/memcontrol.h |  3 +++
 mm/memcontrol.c            | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index c59926c..b84a050 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -203,6 +203,9 @@ struct mem_cgroup {
        /* kill all tasks in the subtree in case of OOM */
        bool oom_kill_all_tasks;
 
+       /* OOM kill score adjustment */
+       short oom_score_adj;
+
        /* handle for "memory.events" */
        struct cgroup_file events_file;
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4face20..e474eba 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5333,6 +5333,36 @@ static ssize_t memory_oom_kill_all_tasks_write(struct 
kernfs_open_file *of,
        return nbytes;
 }
 
+static int memory_oom_score_adj_show(struct seq_file *m, void *v)
+{
+       struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
+       short oom_score_adj = memcg->oom_score_adj;
+
+       seq_printf(m, "%d\n", oom_score_adj);
+
+       return 0;
+}
+
+static ssize_t memory_oom_score_adj_write(struct kernfs_open_file *of,
+                               char *buf, size_t nbytes, loff_t off)
+{
+       struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+       int oom_score_adj;
+       int err;
+
+       err = kstrtoint(strstrip(buf), 0, &oom_score_adj);
+       if (err)
+               return err;
+
+       if (oom_score_adj < OOM_SCORE_ADJ_MIN ||
+                       oom_score_adj > OOM_SCORE_ADJ_MAX)
+               return -EINVAL;
+
+       memcg->oom_score_adj = (short)oom_score_adj;
+
+       return nbytes;
+}
+
 static int memory_events_show(struct seq_file *m, void *v)
 {
        struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
@@ -5459,6 +5489,12 @@ static struct cftype memory_files[] = {
                .write = memory_oom_kill_all_tasks_write,
        },
        {
+               .name = "oom_score_adj",
+               .flags = CFTYPE_NOT_ON_ROOT,
+               .seq_show = memory_oom_score_adj_show,
+               .write = memory_oom_score_adj_write,
+       },
+       {
                .name = "events",
                .flags = CFTYPE_NOT_ON_ROOT,
                .file_offset = offsetof(struct mem_cgroup, events_file),
-- 
2.7.4

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