oom: do not kill tasks with oom_score_adj OOM_SCORE_ADJ_MIN

Commit c9f01245 ("oom: remove oom_disable_count") has removed the
oom_disable_count counter which has been used for early break out from
oom_badness so we could never select a task with oom_score_adj set to
OOM_SCORE_ADJ_MIN (oom disabled).

Now that the counter is gone we are always going through heuristics
calculation and we always return a non zero positive value.  This means
that we can end up killing a task with OOM disabled because it is
indistinguishable from regular tasks with 1% resp.  CAP_SYS_ADMIN tasks
with 3% usage of memory or tasks with oom_score_adj set but OOM enabled.

Let's break out early if the task should have OOM disabled.

Signed-off-by: Michal Hocko <[email protected]>
Acked-by: David Rientjes <[email protected]>
Acked-by: KOSAKI Motohiro <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Ying Han <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 471dedb463ab30f9e57d793c5367cac966098c06..76f2c5ae908e85a858c006d932edcdf9128e0cc2 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -185,6 +185,11 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
        if (!p)
                return 0;
 
+       if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
+               task_unlock(p);
+               return 0;
+       }
+
        /*
         * The memory controller may have a limit of 0 bytes, so avoid a divide
         * by zero, if necessary.