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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 C04A5C433E0 for ; Thu, 11 Feb 2021 12:15:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F13E64E95 for ; Thu, 11 Feb 2021 12:15:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230101AbhBKMOw (ORCPT ); Thu, 11 Feb 2021 07:14:52 -0500 Received: from mx2.suse.de ([195.135.220.15]:34764 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230436AbhBKMMo (ORCPT ); Thu, 11 Feb 2021 07:12:44 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 80C01ACD4; Thu, 11 Feb 2021 12:12:02 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 1B4BA1E14B2; Thu, 11 Feb 2021 13:12:02 +0100 (CET) Date: Thu, 11 Feb 2021 13:12:02 +0100 From: Jan Kara To: Hillf Danton Cc: Jan Kara , syzbot , "linux-ext4@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "syzkaller-bugs@googlegroups.com" , Tahsin Erdogan Subject: Re: possible deadlock in fs_reclaim_acquire (2) Message-ID: <20210211121202.GP19070@quack2.suse.cz> References: <00000000000086723c05bb056425@google.com> <20210211040729.12804-1-hdanton@sina.com> <20210211102225.GK19070@quack2.suse.cz> <20210211120424.86857A3B85@relay2.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210211120424.86857A3B85@relay2.suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu 11-02-21 20:04:14, Hillf Danton wrote: > On Thu 11-02-21 12:07:29, Jan Kara wrote: > >> Fix 71b565ceff37 ("ext4: drop ext4_kvmalloc()") by restoring the > >> GFP_NOFS introduced in dec214d00e0d ("ext4: xattr inode deduplication"). > >> > >> Note this may be the fix also to possible deadlock > >> Reported-by: syzbot+bfdded10ab7dcd7507ae@syzkaller.appspotmail.com > >> https://lore.kernel.org/linux-ext4/000000000000563a0205bafb7970@google.com/ > > > >Please no. Ext4 is using scoping API to limit allocations to GFP_NOFS > >inside transactions. In this case something didn't work which seems like a > >lockdep bug at the first sight but I'll talk to mm guys about it. > >Definitely to problem doesn't seem to be in ext4. > > Feel free to elaborate why we can find ext4 in the report? > Why is ext4 special in this case? Please read my reply to the syzbot report [1]. It has all the details. [1] https://lore.kernel.org/lkml/20210211104947.GL19070@quack2.suse.cz Honza -- Jan Kara SUSE Labs, CR