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=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 95AEAC433DB for ; Fri, 12 Feb 2021 11:19:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1A73264E65 for ; Fri, 12 Feb 2021 11:19:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1A73264E65 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9FFCF8D004A; Fri, 12 Feb 2021 06:19:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9B0958D0015; Fri, 12 Feb 2021 06:19:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8C6668D004A; Fri, 12 Feb 2021 06:19:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0142.hostedemail.com [216.40.44.142]) by kanga.kvack.org (Postfix) with ESMTP id 74E888D0015 for ; Fri, 12 Feb 2021 06:19:19 -0500 (EST) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 3A3DF8249980 for ; Fri, 12 Feb 2021 11:19:19 +0000 (UTC) X-FDA: 77809369638.05.86BD726 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by imf22.hostedemail.com (Postfix) with ESMTP id BB335C0001EE for ; Fri, 12 Feb 2021 11:19:17 +0000 (UTC) Received: from fsav103.sakura.ne.jp (fsav103.sakura.ne.jp [27.133.134.230]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 11CBIE5c098656; Fri, 12 Feb 2021 20:18:14 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav103.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav103.sakura.ne.jp); Fri, 12 Feb 2021 20:18:14 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav103.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 11CBIEE2098653 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Fri, 12 Feb 2021 20:18:14 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: possible deadlock in start_this_handle (2) To: Michal Hocko , Matthew Wilcox Cc: Jan Kara , Dmitry Vyukov , syzbot , Jan Kara , linux-ext4@vger.kernel.org, LKML , syzkaller-bugs , "Theodore Ts'o" , Linux-MM References: <20210211104947.GL19070@quack2.suse.cz> <20210211121020.GO19070@quack2.suse.cz> <20210211125717.GH308988@casper.infradead.org> <20210211132533.GI308988@casper.infradead.org> <20210211142630.GK308988@casper.infradead.org> From: Tetsuo Handa Message-ID: <9cff0fbf-b6e7-1166-e4ba-d4573aef0c82@i-love.sakura.ne.jp> Date: Fri, 12 Feb 2021 20:18:11 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Stat-Signature: f4a8k6oith9qib9h3pbjjqm5zccbnruj X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: BB335C0001EE Received-SPF: none (i-love.sakura.ne.jp>: No applicable sender policy available) receiver=imf22; identity=mailfrom; envelope-from=""; helo=www262.sakura.ne.jp; client-ip=202.181.97.72 X-HE-DKIM-Result: none/none X-HE-Tag: 1613128757-543488 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 2021/02/12 1:41, Michal Hocko wrote: > But I suspect we have drifted away from the original issue. I thought > that a simple check would help us narrow down this particular case and > somebody messing up from the IRQ context didn't sound like a completely > off. > From my experience at https://lkml.kernel.org/r/201409192053.IHJ35462.JLOMOSOFFVtQFH@I-love.SAKURA.ne.jp , I think we can replace direct PF_* manipulation with macros which do not receive "struct task_struct *" argument. Since TASK_PFA_TEST()/TASK_PFA_SET()/TASK_PFA_CLEAR() are for manipulating PFA_* flags on a remote thread, we can define similar ones for manipulating PF_* flags on current thread. Then, auditing dangerous users becomes easier.