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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 9F0F2C433E0 for ; Fri, 12 Feb 2021 12:31:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6566864DEE for ; Fri, 12 Feb 2021 12:31:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231289AbhBLMbY (ORCPT ); Fri, 12 Feb 2021 07:31:24 -0500 Received: from mx2.suse.de ([195.135.220.15]:49644 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229650AbhBLMbT (ORCPT ); Fri, 12 Feb 2021 07:31:19 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1613133032; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5qj3DCkH6KSXjLCqZi9x6XmR8kpK5XSIPuFj/6qx+Dk=; b=GJdLO7vNuHU5kY/jx531qhdurR1ot+bvUV9wWhO8u2XWIGldELlfyLJidkMmSdnPn3rWEg Moy4uqup9gTrdN6ugKLmIc1sLfAdJJavfJxHaFkN9mXOkRRLSo/w7zH5E4LOqpxOq0yXKc iha7zSMFZfbcfuMcpheYvZOAM7Sqf1M= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 8B501AC69; Fri, 12 Feb 2021 12:30:32 +0000 (UTC) Date: Fri, 12 Feb 2021 13:30:31 +0100 From: Michal Hocko To: Matthew Wilcox Cc: Tetsuo Handa , Jan Kara , Dmitry Vyukov , syzbot , Jan Kara , linux-ext4@vger.kernel.org, LKML , syzkaller-bugs , Theodore Ts'o , Linux-MM Subject: Re: possible deadlock in start_this_handle (2) Message-ID: References: <20210211121020.GO19070@quack2.suse.cz> <20210211125717.GH308988@casper.infradead.org> <20210211132533.GI308988@casper.infradead.org> <20210211142630.GK308988@casper.infradead.org> <9cff0fbf-b6e7-1166-e4ba-d4573aef0c82@i-love.sakura.ne.jp> <20210212122207.GM308988@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210212122207.GM308988@casper.infradead.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 12-02-21 12:22:07, Matthew Wilcox wrote: > On Fri, Feb 12, 2021 at 08:18:11PM +0900, Tetsuo Handa wrote: > > 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. > > No, nobody is manipulating another task's GFP flags. Agreed. And nobody should be manipulating PF flags on remote tasks either. -- Michal Hocko SUSE Labs