From patchwork Fri Apr 30 05:57:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12232429 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29466C433B4 for ; Fri, 30 Apr 2021 05:57:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C3B6F61463 for ; Fri, 30 Apr 2021 05:57:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C3B6F61463 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DC0CB8D0003; Fri, 30 Apr 2021 01:57:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D49F36B00DC; Fri, 30 Apr 2021 01:57:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7E7E76B00DC; Fri, 30 Apr 2021 01:57:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0057.hostedemail.com [216.40.44.57]) by kanga.kvack.org (Postfix) with ESMTP id 53B706B00DA for ; Fri, 30 Apr 2021 01:57:06 -0400 (EDT) Received: from smtpin38.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 0F0308249980 for ; Fri, 30 Apr 2021 05:57:06 +0000 (UTC) X-FDA: 78087975252.38.D6B48EE Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf12.hostedemail.com (Postfix) with ESMTP id F20C1135 for ; Fri, 30 Apr 2021 05:56:53 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 8318661463; Fri, 30 Apr 2021 05:57:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1619762224; bh=ok8OtXsNP0K6GTEJDOS7VAVlnbOgfYJupbLxGeOgdBM=; h=Date:From:To:Subject:In-Reply-To:From; b=TM964wdbC1NtjdAET5KVrgT9MkbblruC4SYxzfTUnuXrZoIJIELl0kqSMFDuYjPk7 P4Dvb3bjca77ED54jUkl+qdv4MiP0SG9oGh9Yk8QWLDv6uK1y5rJkdrn8Ky/a/xlSP rXtJu9pLeP4Zo33kVgL9FKvzFU/lSmrGMTKbYhuU= Date: Thu, 29 Apr 2021 22:57:04 -0700 From: Andrew Morton To: akpm@linux-foundation.org, chris@chrisdown.name, guro@fb.com, hannes@cmpxchg.org, hughd@google.com, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, shakeelb@google.com, torvalds@linux-foundation.org Subject: [patch 076/178] mm: page_counter: mitigate consequences of a page_counter underflow Message-ID: <20210430055704.VJCczN8O-%akpm@linux-foundation.org> In-Reply-To: <20210429225251.02b6386d21b69255b4f6c163@linux-foundation.org> User-Agent: s-nail v14.8.16 Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=TM964wdb; dmarc=none; spf=pass (imf12.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Stat-Signature: gymfhgbsrc4axyhrf8nq6shmfspx48bq X-Rspamd-Queue-Id: F20C1135 X-Rspamd-Server: rspam05 Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf12; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619762213-255411 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Johannes Weiner Subject: mm: page_counter: mitigate consequences of a page_counter underflow When the unsigned page_counter underflows, even just by a few pages, a cgroup will not be able to run anything afterwards and trigger the OOM killer in a loop. Underflows shouldn't happen, but when they do in practice, we may just be off by a small amount that doesn't interfere with the normal operation - consequences don't need to be that dire. Reset the page_counter to 0 upon underflow. We'll issue a warning that the accounting will be off and then try to keep limping along. [ We used to do this with the original res_counter, where it was a more straight-forward correction inside the spinlock section. I didn't carry it forward into the lockless page counters for simplicity, but it turns out this is quite useful in practice. ] Link: https://lkml.kernel.org/r/20210408143155.2679744-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Acked-by: Chris Down Reviewed-by: Shakeel Butt Cc: Hugh Dickins Cc: Roman Gushchin Signed-off-by: Andrew Morton --- mm/page_counter.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/mm/page_counter.c~mm-page_counter-mitigate-consequences-of-a-page_counter-underflow +++ a/mm/page_counter.c @@ -52,9 +52,13 @@ void page_counter_cancel(struct page_cou long new; new = atomic_long_sub_return(nr_pages, &counter->usage); - propagate_protected_usage(counter, new); /* More uncharges than charges? */ - WARN_ON_ONCE(new < 0); + if (WARN_ONCE(new < 0, "page_counter underflow: %ld nr_pages=%lu\n", + new, nr_pages)) { + new = 0; + atomic_long_set(&counter->usage, new); + } + propagate_protected_usage(counter, new); } /**