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=-6.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS 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 00BDDC2B9F4 for ; Mon, 14 Jun 2021 22:10:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A31316102A for ; Mon, 14 Jun 2021 22:10:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A31316102A 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 2A6166B006C; Mon, 14 Jun 2021 18:10:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 255CA6B006E; Mon, 14 Jun 2021 18:10:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D19C6B0070; Mon, 14 Jun 2021 18:10:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0207.hostedemail.com [216.40.44.207]) by kanga.kvack.org (Postfix) with ESMTP id CE5386B006C for ; Mon, 14 Jun 2021 18:10:32 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 70D66BA18 for ; Mon, 14 Jun 2021 22:10:32 +0000 (UTC) X-FDA: 78253724304.10.D0669C0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf21.hostedemail.com (Postfix) with ESMTP id 5B403E000243 for ; Mon, 14 Jun 2021 22:10:20 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id EE52C61183; Mon, 14 Jun 2021 22:10:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1623708631; bh=+b3PvT9/aY2E67kubR+lIKfGkq3+hvelnkLl1X9PaRs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=YxBz4Mwst8d0Vx4VSdrYvKvt/DH5+jhVJ9tHxBAyTqdZz3Pdq1H0E+LmLSo5RTsa4 o38rJybOPPKgCkQXTSSn7Lrr4/2GG+z7FYjioZvQO2DaXixIfY9VEPYkk020heM3yu hAokdavgzb6ZJzd2kepKd6xGg0tz8l9Rg+huDlvk= Date: Mon, 14 Jun 2021 15:10:30 -0700 From: Andrew Morton To: Yu Zhao Cc: Minchan Kim , linux-mm@kvack.org Subject: Re: [PATCH] mm/vmscan.c: fix potential deadlock in reclaim_pages() Message-Id: <20210614151030.35fd6ecfecc2e3df2d7c5dc0@linux-foundation.org> In-Reply-To: <20210614194727.2684053-1-yuzhao@google.com> References: <20210614194727.2684053-1-yuzhao@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 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=YxBz4Mws; dmarc=none; spf=pass (imf21.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam02 X-Stat-Signature: osxa8wcc9848cwpf85ahw3dxxceomsmk X-Rspamd-Queue-Id: 5B403E000243 X-HE-Tag: 1623708620-695002 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: On Mon, 14 Jun 2021 13:47:27 -0600 Yu Zhao wrote: > Use memalloc_noreclaim_save()/memalloc_noreclaim_restore() in > reclaim_pages() to prevent the page reclaim from going into the block > I/O layer recursively and deadlock. Well. Deadlocking the kernel is considered a bad thing ;) >From the lack of a cc:stable I'm assuming that this is a theoretical from-code-inspection thing and that such a deadlock has not been observed? If not, why do we think that is the case? What is saving us? (In other words, more detailed changelogging, please!)