oom: move OOM_DISABLE check from oom_kill_task to out_of_memory()

Presently if oom_kill_allocating_task is enabled and current have
OOM_DISABLED, following printk in oom_kill_process is called twice.

    pr_err("%s: Kill process %d (%s) score %lu or sacrifice child\n",
            message, task_pid_nr(p), p->comm, points);

So, OOM_DISABLE check should be more early.

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>

mm/oom_kill.c

@@ -424,7 +424,7 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
 static int oom_kill_task(struct task_struct *p)
 {
 	p = find_lock_task_mm(p);
-	if (!p || p->signal->oom_adj == OOM_DISABLE) {
+	if (!p) {
 		task_unlock(p);
 		return 1;
 	}
@@ -686,7 +686,8 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 
 	read_lock(&tasklist_lock);
 	if (sysctl_oom_kill_allocating_task &&
-	    !oom_unkillable_task(current, NULL, nodemask)) {
+	    !oom_unkillable_task(current, NULL, nodemask) &&
+	    (current->signal->oom_adj != OOM_DISABLE)) {
 		/*
 		 * oom_kill_process() needs tasklist_lock held.  If it returns
 		 * non-zero, current could not be killed so we must fallback to