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 9DA05C433E0 for ; Thu, 11 Feb 2021 10:49:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0854264E30 for ; Thu, 11 Feb 2021 10:49:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0854264E30 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 675706B00BE; Thu, 11 Feb 2021 05:49:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 625276B00BF; Thu, 11 Feb 2021 05:49:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 561E56B00C0; Thu, 11 Feb 2021 05:49:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id 3FA756B00BE for ; Thu, 11 Feb 2021 05:49:50 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 05D64180AD807 for ; Thu, 11 Feb 2021 10:49:50 +0000 (UTC) X-FDA: 77805666540.20.range93_260661e27618 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id E1138180C07A3 for ; Thu, 11 Feb 2021 10:49:49 +0000 (UTC) X-HE-Tag: range93_260661e27618 X-Filterd-Recvd-Size: 4932 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf48.hostedemail.com (Postfix) with ESMTP for ; Thu, 11 Feb 2021 10:49:49 +0000 (UTC) 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 CE92AADA2; Thu, 11 Feb 2021 10:49:47 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 461201E14B2; Thu, 11 Feb 2021 11:49:47 +0100 (CET) Date: Thu, 11 Feb 2021 11:49:47 +0100 From: Jan Kara To: syzbot Cc: jack@suse.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tytso@mit.edu, mhocko@suse.cz, linux-mm@kvack.org Subject: Re: possible deadlock in start_this_handle (2) Message-ID: <20210211104947.GL19070@quack2.suse.cz> References: <000000000000563a0205bafb7970@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <000000000000563a0205bafb7970@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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: Hello, added mm guys to CC. On Wed 10-02-21 05:35:18, syzbot wrote: > HEAD commit: 1e0d27fc Merge branch 'akpm' (patches from Andrew) > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=15cbce90d00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=bd1f72220b2e57eb > dashboard link: https://syzkaller.appspot.com/bug?extid=bfdded10ab7dcd7507ae > userspace arch: i386 > > Unfortunately, I don't have any reproducer for this issue yet. > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+bfdded10ab7dcd7507ae@syzkaller.appspotmail.com > > ====================================================== > WARNING: possible circular locking dependency detected > 5.11.0-rc6-syzkaller #0 Not tainted > ------------------------------------------------------ > kswapd0/2246 is trying to acquire lock: > ffff888041a988e0 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0xf81/0x1380 fs/jbd2/transaction.c:444 > > but task is already holding lock: > ffffffff8be892c0 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:5195 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #2 (fs_reclaim){+.+.}-{0:0}: > __fs_reclaim_acquire mm/page_alloc.c:4326 [inline] > fs_reclaim_acquire+0x117/0x150 mm/page_alloc.c:4340 > might_alloc include/linux/sched/mm.h:193 [inline] > slab_pre_alloc_hook mm/slab.h:493 [inline] > slab_alloc_node mm/slub.c:2817 [inline] > __kmalloc_node+0x5f/0x430 mm/slub.c:4015 > kmalloc_node include/linux/slab.h:575 [inline] > kvmalloc_node+0x61/0xf0 mm/util.c:587 > kvmalloc include/linux/mm.h:781 [inline] > ext4_xattr_inode_cache_find fs/ext4/xattr.c:1465 [inline] > ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1508 [inline] > ext4_xattr_set_entry+0x1ce6/0x3780 fs/ext4/xattr.c:1649 > ext4_xattr_ibody_set+0x78/0x2b0 fs/ext4/xattr.c:2224 > ext4_xattr_set_handle+0x8f4/0x13e0 fs/ext4/xattr.c:2380 > ext4_xattr_set+0x13a/0x340 fs/ext4/xattr.c:2493 > ext4_xattr_user_set+0xbc/0x100 fs/ext4/xattr_user.c:40 > __vfs_setxattr+0x10e/0x170 fs/xattr.c:177 > __vfs_setxattr_noperm+0x11a/0x4c0 fs/xattr.c:208 > __vfs_setxattr_locked+0x1bf/0x250 fs/xattr.c:266 > vfs_setxattr+0x135/0x320 fs/xattr.c:291 > setxattr+0x1ff/0x290 fs/xattr.c:553 > path_setxattr+0x170/0x190 fs/xattr.c:572 > __do_sys_setxattr fs/xattr.c:587 [inline] > __se_sys_setxattr fs/xattr.c:583 [inline] > __ia32_sys_setxattr+0xbc/0x150 fs/xattr.c:583 > do_syscall_32_irqs_on arch/x86/entry/common.c:77 [inline] > __do_fast_syscall_32+0x56/0x80 arch/x86/entry/common.c:139 > do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:164 > entry_SYSENTER_compat_after_hwframe+0x4d/0x5c This stacktrace should never happen. ext4_xattr_set() starts a transaction. That internally goes through start_this_handle() which calls: handle->saved_alloc_context = memalloc_nofs_save(); and we restore the allocation context only in stop_this_handle() when stopping the handle. And with this fs_reclaim_acquire() should remove __GFP_FS from the mask and not call __fs_reclaim_acquire(). Now I have no idea why something here didn't work out. Given we don't have a reproducer it will be probably difficult to debug this. I'd note that about year and half ago similar report happened (got autoclosed) so it may be something real somewhere but it may also be just some HW glitch or something like that. Honza -- Jan Kara SUSE Labs, CR