linux-kernel - [RFC] memcg, oom: clean up mem_cgroup_oom

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Message-Id: <20230315070302.268316-1-haifeng.xu@shopee.com>
Date:   Wed, 15 Mar 2023 07:03:02 +0000
From:   Haifeng Xu <haifeng.xu@...pee.com>
To:     mhocko@...nel.org
Cc:     hannes@...xchg.org, shakeelb@...gle.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Haifeng Xu <haifeng.xu@...pee.com>
Subject: [RFC] memcg, oom: clean up mem_cgroup_oom_synchronize

Since commit 29ef680ae7c2 ("memcg, oom: move out_of_memory back to
the charge path"), only oom_kill_disable is set, oom killer will
be delayed to page fault path. In the charge patch, even if the
oom_lock in memcg can't be acquired, the oom handing can also be
invoked. In order to keep the behavior consistent with it, remove
the lock check, just leave oom_kill_disable check behind in the
page fault path.

Furthermore, the lock contender won't be scheduled out, this doesn't
fit the sixth description in commit fb2a6fc56be66 ("mm: memcg:
rework and document OOM waiting and wakeup"). So remove the explicit
wakeup for the lock holder.

Fixes: fb2a6fc56be6 ("mm: memcg: rework and document OOM waiting and wakeup")
Signed-off-by: Haifeng Xu <haifeng.xu@...pee.com>
---
 mm/memcontrol.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5abffe6f8389..360fa7cf7879 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1999,7 +1999,7 @@ bool mem_cgroup_oom_synchronize(bool handle)
 	if (locked)
 		mem_cgroup_oom_notify(memcg);
 
-	if (locked && !memcg->oom_kill_disable) {
+	if (!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,
@@ -2010,15 +2010,8 @@ bool mem_cgroup_oom_synchronize(bool handle)
 		finish_wait(&memcg_oom_waitq, &owait.wait);
 	}
 
-	if (locked) {
+	if (locked)
 		mem_cgroup_oom_unlock(memcg);
-		/*
-		 * There is no guarantee that an OOM-lock contender
-		 * sees the wakeups triggered by the OOM kill
-		 * uncharges.  Wake any sleepers explicitly.
-		 */
-		memcg_oom_recover(memcg);
-	}
 cleanup:
 	current->memcg_in_oom = NULL;
 	css_put(&memcg->css);
-- 
2.25.1