oom: /proc/<pid>/oom_score treat kernel thread honestly

If a kernel thread is using use_mm(), badness() returns a positive value.
This is not a big issue because caller take care of it correctly.  But
there is one exception, /proc/<pid>/oom_score calls badness() directly and
doesn't care that the task is a regular process.

Another example, /proc/1/oom_score return !0 value.  But it's unkillable.
This incorrectness makes administration a little confusing.

This patch fixes it.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index acb7ef80ea4f..fc23f62bb0b8 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -428,7 +428,8 @@ static const struct file_operations proc_lstats_operations = {
 #endif
 
 /* The badness from the OOM killer */
-unsigned long badness(struct task_struct *p, unsigned long uptime);
+unsigned long badness(struct task_struct *p, struct mem_cgroup *mem,
+                      nodemask_t *nodemask, unsigned long uptime);
 static int proc_oom_score(struct task_struct *task, char *buffer)
 {
         unsigned long points = 0;
@@ -437,7 +438,7 @@ static int proc_oom_score(struct task_struct *task, char *buffer)
         do_posix_clock_monotonic_gettime(&uptime);
         read_lock(&tasklist_lock);
         if (pid_alive(task))
-                points = badness(task, uptime.tv_sec);
+                points = badness(task, NULL, NULL, uptime.tv_sec);
         read_unlock(&tasklist_lock);
         return sprintf(buffer, "%lu\n", points);
 }