Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30FD0C433EF for ; Tue, 16 Nov 2021 01:56:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1009761A8D for ; Tue, 16 Nov 2021 01:56:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1382087AbhKPB6P (ORCPT ); Mon, 15 Nov 2021 20:58:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:55786 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240969AbhKOSO0 (ORCPT ); Mon, 15 Nov 2021 13:14:26 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 95EF161AA5; Mon, 15 Nov 2021 17:49:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636998546; bh=3/GhNhNpV7TuJJIs1sSxWld4fpGprXLa0BpXnUsoB4A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=liRlgQ0xZYyN7umZkxGl2FMc0vR17R8MGV9DJToaj+0sAzqwQ+zAo7S1I43KZQtah HiUyYQPHgoYkaqtuSrWJjrfP8Zz/lupWFUUTBT9Z/YTu2DsKgkKWyFRxG3OIizxCin DAwtqPUtayd0I7J80rlBFyP/GiV6D6KuIcIU3oIQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vasily Averin , Michal Hocko , Johannes Weiner , Vladimir Davydov , Roman Gushchin , Uladzislau Rezki , Vlastimil Babka , Shakeel Butt , Mel Gorman , Tetsuo Handa , Andrew Morton , Linus Torvalds Subject: [PATCH 5.10 549/575] memcg: prohibit unconditional exceeding the limit of dying tasks Date: Mon, 15 Nov 2021 18:04:34 +0100 Message-Id: <20211115165402.667702086@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165343.579890274@linuxfoundation.org> References: <20211115165343.579890274@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vasily Averin commit a4ebf1b6ca1e011289677239a2a361fde4a88076 upstream. Memory cgroup charging allows killed or exiting tasks to exceed the hard limit. It is assumed that the amount of the memory charged by those tasks is bound and most of the memory will get released while the task is exiting. This is resembling a heuristic for the global OOM situation when tasks get access to memory reserves. There is no global memory shortage at the memcg level so the memcg heuristic is more relieved. The above assumption is overly optimistic though. E.g. vmalloc can scale to really large requests and the heuristic would allow that. We used to have an early break in the vmalloc allocator for killed tasks but this has been reverted by commit b8c8a338f75e ("Revert "vmalloc: back off when the current task is killed""). There are likely other similar code paths which do not check for fatal signals in an allocation&charge loop. Also there are some kernel objects charged to a memcg which are not bound to a process life time. It has been observed that it is not really hard to trigger these bypasses and cause global OOM situation. One potential way to address these runaways would be to limit the amount of excess (similar to the global OOM with limited oom reserves). This is certainly possible but it is not really clear how much of an excess is desirable and still protects from global OOMs as that would have to consider the overall memcg configuration. This patch is addressing the problem by removing the heuristic altogether. Bypass is only allowed for requests which either cannot fail or where the failure is not desirable while excess should be still limited (e.g. atomic requests). Implementation wise a killed or dying task fails to charge if it has passed the OOM killer stage. That should give all forms of reclaim chance to restore the limit before the failure (ENOMEM) and tell the caller to back off. In addition, this patch renames should_force_charge() helper to task_is_dying() because now its use is not associated witch forced charging. This patch depends on pagefault_out_of_memory() to not trigger out_of_memory(), because then a memcg failure can unwind to VM_FAULT_OOM and cause a global OOM killer. Link: https://lkml.kernel.org/r/8f5cebbb-06da-4902-91f0-6566fc4b4203@virtuozzo.com Signed-off-by: Vasily Averin Suggested-by: Michal Hocko Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Roman Gushchin Cc: Uladzislau Rezki Cc: Vlastimil Babka Cc: Shakeel Butt Cc: Mel Gorman Cc: Tetsuo Handa Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memcontrol.c | 27 ++++++++------------------- 1 file changed, 8 insertions(+), 19 deletions(-) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -230,7 +230,7 @@ enum res_type { iter != NULL; \ iter = mem_cgroup_iter(NULL, iter, NULL)) -static inline bool should_force_charge(void) +static inline bool task_is_dying(void) { return tsk_is_oom_victim(current) || fatal_signal_pending(current) || (current->flags & PF_EXITING); @@ -1729,7 +1729,7 @@ static bool mem_cgroup_out_of_memory(str * A few threads which were not waiting at mutex_lock_killable() can * fail to bail out. Therefore, check again after holding oom_lock. */ - ret = should_force_charge() || out_of_memory(&oc); + ret = task_is_dying() || out_of_memory(&oc); unlock: mutex_unlock(&oom_lock); @@ -2683,6 +2683,7 @@ static int try_charge(struct mem_cgroup struct page_counter *counter; enum oom_status oom_status; unsigned long nr_reclaimed; + bool passed_oom = false; bool may_swap = true; bool drained = false; unsigned long pflags; @@ -2720,15 +2721,6 @@ retry: goto force; /* - * Unlike in global OOM situations, memcg is not in a physical - * memory shortage. Allow dying and OOM-killed tasks to - * bypass the last charges so that they can exit quickly and - * free their memory. - */ - if (unlikely(should_force_charge())) - goto force; - - /* * Prevent unbounded recursion when reclaim operations need to * allocate memory. This might exceed the limits temporarily, * but we prefer facilitating memory reclaim and getting back @@ -2788,8 +2780,9 @@ retry: if (gfp_mask & __GFP_NOFAIL) goto force; - if (fatal_signal_pending(current)) - goto force; + /* Avoid endless loop for tasks bypassed by the oom killer */ + if (passed_oom && task_is_dying()) + goto nomem; /* * keep retrying as long as the memcg oom killer is able to make @@ -2798,14 +2791,10 @@ retry: */ oom_status = mem_cgroup_oom(mem_over_limit, gfp_mask, get_order(nr_pages * PAGE_SIZE)); - switch (oom_status) { - case OOM_SUCCESS: + if (oom_status == OOM_SUCCESS) { + passed_oom = true; nr_retries = MAX_RECLAIM_RETRIES; goto retry; - case OOM_FAILED: - goto force; - default: - goto nomem; } nomem: if (!(gfp_mask & __GFP_NOFAIL))