From mboxrd@z Thu Jan 1 00:00:00 1970 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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 EBF58CA9EAE for ; Wed, 30 Oct 2019 00:47:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF4012083E for ; Wed, 30 Oct 2019 00:47:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572396456; bh=rC4DTyV2zuA+J7bw7dlMjJDABthKcuPGgzmZ5hyLjuk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=bh6KMVdNfPhdji3vsqHeQOk7xdkgrROKd7KlD+3k4C+LDD2hzFnlItf6y3PcfJ9TC UsB0clEvNrCWckvo1EdnvSVGW0+SxpEfWYmkHqarXHEVMNX+NQxqn0/jxDPJ/aBI5E 6gSFQJIlC2aGSSTRVdjcJuFzEOqoAZaySsizQ6jA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726331AbfJ3ArZ (ORCPT ); Tue, 29 Oct 2019 20:47:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:50748 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726076AbfJ3ArY (ORCPT ); Tue, 29 Oct 2019 20:47:24 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BA2EB2083E; Wed, 30 Oct 2019 00:47:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572396444; bh=rC4DTyV2zuA+J7bw7dlMjJDABthKcuPGgzmZ5hyLjuk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=DqNmB7cmPEMslfCggeao0xz1kdv2tQhIkyD7Hc8ovAHyXPu3xJlmo9hCCB4yuZF2C Yqf39GHojD759SooL74JvoLuYT7M8J0q4zOVJ8XoFBP4Q/DrCA+/i6JM6+iJH4KCx8 s/OLz4DGT94C0Dhpc+xlz1YOg3OoodQ3lsuWTBl0= Date: Tue, 29 Oct 2019 17:47:23 -0700 From: Andrew Morton To: Shakeel Butt Cc: Greg Thelen , Roman Gushchin , Johannes Weiner , Michal Hocko , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+13f93c99c06988391efe@syzkaller.appspotmail.com Subject: Re: [PATCH] mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node() Message-Id: <20191029174723.ceb916ec850e7c88ed00e091@linux-foundation.org> In-Reply-To: <20191029234753.224143-1-shakeelb@google.com> References: <20191029234753.224143-1-shakeelb@google.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Oct 2019 16:47:53 -0700 Shakeel Butt wrote: > Since commit 1ba6fc9af35b ("mm: vmscan: do not share cgroup iteration > between reclaimers"), the memcg reclaim does not bail out earlier based > on sc->nr_reclaimed and will traverse all the nodes. All the reclaimable > pages of the memcg on all the nodes will be scanned relative to the > reclaim priority. So, there is no need to maintain state regarding which > node to start the memcg reclaim from. Also KCSAN complains data races in > the code maintaining the state. > > This patch effectively reverts the commit 889976dbcb12 ("memcg: reclaim > memory from nodes in round-robin order") and the commit 453a9bf347f1 > ("memcg: fix numa scan information update to be triggered by memory > event"). > > Signed-off-by: Shakeel Butt > Reported-by: The sysbot report (http://lkml.kernel.org/r/00000000000055aba7058af4d378@google.com) was for a null pointer deref. So won't we be needing a Fixes: and cc:stable?