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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 DCADDECE58C for ; Mon, 7 Oct 2019 13:28:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3A1521835 for ; Mon, 7 Oct 2019 13:28:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727940AbfJGN2W (ORCPT ); Mon, 7 Oct 2019 09:28:22 -0400 Received: from mx2.suse.de ([195.135.220.15]:39098 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727838AbfJGN2V (ORCPT ); Mon, 7 Oct 2019 09:28:21 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 71A85AC90; Mon, 7 Oct 2019 13:28:18 +0000 (UTC) Subject: Re: [bug, 5.2.16] kswapd/compaction null pointer crash [was Re: xfs_inode not reclaimed/memory leak on 5.2.16] To: Florian Weimer Cc: Dave Chinner , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Mel Gorman References: <87pnji8cpw.fsf@mid.deneb.enyo.de> <20190930085406.GP16973@dread.disaster.area> <87o8z1fvqu.fsf@mid.deneb.enyo.de> <20190930211727.GQ16973@dread.disaster.area> <96023250-6168-3806-320a-a3468f1cd8c9@suse.cz> <87lfu4i79z.fsf@mid.deneb.enyo.de> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; prefer-encrypt=mutual; keydata= mQINBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 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2ijoaMFTAU+uBtE14UP5F+LWdmRdEGS1Ah1NwooL27uAFllTDQxDhg/+LJ/TqB8ZuidOIy1B xVKRSg3I2m+DUTVqBy7Lixo73hnW69kSjtqCeamY/NSu6LNP+b0wAOKhwz9hBEwEHLp05+mj 5ZFJyfGsOiNUcMoO/17FO4EBxSDP3FDLllpuzlFD7SXkfJaMWYmXIlO0jLzdfwfcnDzBbPwO hBM8hvtsyq8lq8vJOxv6XD6xcTtj5Az8t2JjdUX6SF9hxJpwhBU0wrCoGDkWp4Bbv6jnF7zP Nzftr4l8RuJoywDIiJpdaNpSlXKpj/K6KrnyAI/joYc7 Message-ID: <2af04718-d5cb-1bb1-a789-be017f2e2df0@suse.cz> Date: Mon, 7 Oct 2019 15:28:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <87lfu4i79z.fsf@mid.deneb.enyo.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 10/1/19 9:40 PM, Florian Weimer wrote: > * Vlastimil Babka: > >> On 9/30/19 11:17 PM, Dave Chinner wrote: >>> On Mon, Sep 30, 2019 at 09:07:53PM +0200, Florian Weimer wrote: >>>> * Dave Chinner: >>>> >>>>> On Mon, Sep 30, 2019 at 09:28:27AM +0200, Florian Weimer wrote: >>>>>> Simply running “du -hc” on a large directory tree causes du to be >>>>>> killed because of kernel paging request failure in the XFS code. >>>>> >>>>> dmesg output? if the system was still running, then you might be >>>>> able to pull the trace from syslog. But we can't do much without >>>>> knowing what the actual failure was.... >>>> >>>> Huh. I actually have something in syslog: >>>> >>>> [ 4001.238411] BUG: kernel NULL pointer dereference, address: >>>> 0000000000000000 >>>> [ 4001.238415] #PF: supervisor read access in kernel mode >>>> [ 4001.238417] #PF: error_code(0x0000) - not-present page >>>> [ 4001.238418] PGD 0 P4D 0 >>>> [ 4001.238420] Oops: 0000 [#1] SMP PTI >>>> [ 4001.238423] CPU: 3 PID: 143 Comm: kswapd0 Tainted: G I 5.2.16fw+ >>>> #1 >>>> [ 4001.238424] Hardware name: System manufacturer System Product >>>> Name/P6X58D-E, BIOS 0701 05/10/2011 >>>> [ 4001.238430] RIP: 0010:__reset_isolation_pfn+0x27f/0x3c0 >>> >>> That's memory compaction code it's crashed in. >>> >>>> [ 4001.238432] Code: 44 c6 48 8b 00 a8 10 74 bc 49 8b 16 48 89 d0 >>>> 48 c1 ea 35 48 8b 14 d7 48 c1 e8 2d 48 85 d2 74 0a 0f b6 c0 48 c1 >>>> e0 04 48 01 c2 <48> 8b 02 4c 89 f2 41 b8 01 00 00 00 31 f6 b9 03 00 >>>> 00 00 4c 89 f7 >> >> Tried to decode it, but couldn't match it to source code, my version of >> compiled code is too different. Would it be possible to either send >> mm/compaction.o from the matching build, or output of 'objdump -d -l' >> for the __reset_isolation_pfn function? > > See below. I don't have debuginfo for this build, and the binary does > not reproduce for some reason. Due to the heavy inlining, it might be > quite hard to figure out what's going on. Thanks, but I'm still not able to "decompile" that in my head. > I've switched to kernel builds with debuginfo from now on. I'm > surprised that it's not the default. Let's see if you can reproduce it with that. However, I've noticed at least something weird: > 37e: 49 8b 16 mov (%r14),%rdx > 381: 48 89 d0 mov %rdx,%rax > 384: 48 c1 ea 35 shr $0x35,%rdx > 388: 48 8b 14 d7 mov (%rdi,%rdx,8),%rdx > 38c: 48 c1 e8 2d shr $0x2d,%rax > 390: 48 85 d2 test %rdx,%rdx > 393: 74 0a je 39f <__reset_isolation_pfn+0x27f> IIUC, this will jump to 39f when rdx is zero. > 395: 0f b6 c0 movzbl %al,%eax > 398: 48 c1 e0 04 shl $0x4,%rax > 39c: 48 01 c2 add %rax,%rdx > 39f: 48 8b 02 mov (%rdx),%rax And this is where we crash because rdx is zero. So the test+branch might have sent us directly here to crash. Sounds like an inverted condition somewhere? Or possibly a result of optimizations.