memcg, oom: remove unnecessary check in mem_cgroup_oom_synchronize()

mem_cgroup_oom_synchronize() is only used when the memcg oom handling is
handed over to the edge of the #PF path.  Since commit 29ef680
("memcg, oom: move out_of_memory back to the charge path") this is the
case only when the kernel memcg oom killer is disabled
(current->memcg_in_oom is only set if memcg->oom_kill_disable).  Therefore
a check for oom_kill_disable in mem_cgroup_oom_synchronize() is not
required.

Link: https://lkml.kernel.org/r/20230419030739.115845-1-haifeng.xu@shopee.com
Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcontrol.c

@@ -2024,16 +2024,9 @@ bool mem_cgroup_oom_synchronize(bool handle)
 	if (locked)
 		mem_cgroup_oom_notify(memcg);
 
-	if (locked && !READ_ONCE(memcg->oom_kill_disable)) {
-		mem_cgroup_unmark_under_oom(memcg);
-		finish_wait(&memcg_oom_waitq, &owait.wait);
-		mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask,
-					 current->memcg_oom_order);
-	} else {
-		schedule();
-		mem_cgroup_unmark_under_oom(memcg);
-		finish_wait(&memcg_oom_waitq, &owait.wait);
-	}
+	schedule();
+	mem_cgroup_unmark_under_oom(memcg);
+	finish_wait(&memcg_oom_waitq, &owait.wait);
 
 	if (locked) {
 		mem_cgroup_oom_unlock(memcg);