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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6A52C433F5 for ; Wed, 6 Oct 2021 08:39:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8CBB561139 for ; Wed, 6 Oct 2021 08:39:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237670AbhJFIlo (ORCPT ); Wed, 6 Oct 2021 04:41:44 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:38407 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231415AbhJFIlm (ORCPT ); Wed, 6 Oct 2021 04:41:42 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=rongwei.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0Uqjldqo_1633509587; Received: from 192.168.31.179(mailfrom:rongwei.wang@linux.alibaba.com fp:SMTPD_---0Uqjldqo_1633509587) by smtp.aliyun-inc.com(127.0.0.1); Wed, 06 Oct 2021 16:39:48 +0800 Message-ID: Date: Wed, 6 Oct 2021 16:39:47 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:93.0) Gecko/20100101 Thunderbird/93.0 Subject: Re: [PATCH v3 v3 2/2] mm, thp: bail out early in collapse_file for writeback page Content-Language: en-US To: Matthew Wilcox Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, song@kernel.org, william.kucharski@oracle.com, hughd@google.com References: <20210906121200.57905-1-rongwei.wang@linux.alibaba.com> <20211006021837.59721-1-rongwei.wang@linux.alibaba.com> <20211006021837.59721-3-rongwei.wang@linux.alibaba.com> From: Rongwei Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/6/21 10:41 AM, Matthew Wilcox wrote: > On Wed, Oct 06, 2021 at 10:18:37AM +0800, Rongwei Wang wrote: >> Currently collapse_file does not explicitly check PG_writeback, instead, >> page_has_private and try_to_release_page are used to filter writeback >> pages. This does not work for xfs with blocksize equal to or larger >> than pagesize, because in such case xfs has no page->private. >> >> This makes collapse_file bail out early for writeback page. Otherwise, >> xfs end_page_writeback will panic as follows. > > Could you cut the timestamps out? They don't add any value. OK, no problem! > >> [ 6411.448211] page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:ffff0003f88c86a8 index:0x0 pfn:0x84ef32 >> [ 6411.448304] aops:xfs_address_space_operations [xfs] ino:30000b7 dentry name:"libtest.so" >> [ 6411.448312] flags: 0x57fffe0000008027(locked|referenced|uptodate|active|writeback) >> [ 6411.448317] raw: 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ffff0003f88c86a8 >> [ 6411.448321] raw: 0000000000000000 0000000000000000 00000000ffffffff ffff0000c3e9a000 >> [ 6411.448324] page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u <= 127u)) >> [ 6411.448327] page->mem_cgroup:ffff0000c3e9a000 >> [ 6411.448340] ------------[ cut here ]------------ >> [ 6411.448343] kernel BUG at include/linux/mm.h:1212! >> [ 6411.449288] Internal error: Oops - BUG: 0 [#1] SMP >> [ 6411.449786] Modules linked in: >> [ 6411.449790] BUG: Bad page state in process khugepaged pfn:84ef32 >> [ 6411.450143] xfs(E) >> [ 6411.450459] page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:0 index:0x0 pfn:0x84ef32 >> [ 6411.451361] libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) ... >> [ 6411.451387] CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Tainted: ... >> [ 6411.451389] pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--) >> [ 6411.451393] pc : end_page_writeback+0x1c0/0x214 >> [ 6411.451394] lr : end_page_writeback+0x1c0/0x214 >> [ 6411.451395] sp : ffff800011ce3cc0 >> [ 6411.451396] x29: ffff800011ce3cc0 x28: 0000000000000000 >> [ 6411.451398] x27: ffff000c04608040 x26: 0000000000000000 >> [ 6411.451399] x25: ffff000c04608040 x24: 0000000000001000 >> [ 6411.451401] x23: ffff0003f88c8530 x22: 0000000000001000 >> [ 6411.451403] x21: ffff0003f88c8530 x20: 0000000000000000 >> [ 6411.451404] x19: fffffe00201bcc80 x18: 0000000000000030 >> [ 6411.451406] x17: 0000000000000000 x16: 0000000000000000 >> [ 6411.451407] x15: ffff000c018f9760 x14: ffffffffffffffff >> [ 6411.451409] x13: ffff8000119d72b0 x12: ffff8000119d6ee3 >> [ 6411.451410] x11: ffff8000117b69b8 x10: 00000000ffff8000 >> [ 6411.451412] x9 : ffff800010617534 x8 : 0000000000000000 >> [ 6411.451413] x7 : ffff8000114f69b8 x6 : 000000000000000f >> [ 6411.451415] x5 : 0000000000000000 x4 : 0000000000000000 >> [ 6411.451416] x3 : 0000000000000400 x2 : 0000000000000000 >> [ 6411.451418] x1 : 0000000000000000 x0 : 0000000000000000 >> [ 6411.451420] Call trace: >> [ 6411.451421] end_page_writeback+0x1c0/0x214 >> [ 6411.451424] iomap_finish_page_writeback+0x13c/0x204 >> [ 6411.451425] iomap_finish_ioend+0xe8/0x19c >> [ 6411.451426] iomap_writepage_end_bio+0x38/0x50 >> [ 6411.451427] bio_endio+0x168/0x1ec >> [ 6411.451430] blk_update_request+0x278/0x3f0 >> [ 6411.451432] blk_mq_end_request+0x34/0x15c >> [ 6411.451435] virtblk_request_done+0x38/0x74 [virtio_blk] >> [ 6411.451437] blk_done_softirq+0xc4/0x110 >> [ 6411.451439] __do_softirq+0x128/0x38c >> [ 6411.451441] __irq_exit_rcu+0x118/0x150 >> [ 6411.451442] irq_exit+0x1c/0x30 >> [ 6411.451445] __handle_domain_irq+0x8c/0xf0 >> [ 6411.451446] gic_handle_irq+0x84/0x108 >> [ 6411.451447] el1_irq+0xcc/0x180 >> [ 6411.451448] arch_cpu_idle+0x18/0x40 >> [ 6411.451450] default_idle_call+0x4c/0x1a0 >> [ 6411.451453] cpuidle_idle_call+0x168/0x1e0 >> [ 6411.451454] do_idle+0xb4/0x104 >> [ 6411.451455] cpu_startup_entry+0x30/0x9c >> [ 6411.451458] secondary_start_kernel+0x104/0x180 >> [ 6411.451460] Code: d4210000 b0006161 910c8021 94013f4d (d4210000) >> [ 6411.451462] ---[ end trace 4a88c6a074082f8c ]--- >> [ 6411.451464] Kernel panic - not syncing: Oops - BUG: Fatal exception in interrupt >> >> Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs") >> Suggested-by: Yang Shi >> Signed-off-by: Xu Yu >> Signed-off-by: Rongwei Wang > > Reviewed-by: Matthew Wilcox (Oracle) > > Although I think the Fixes: line is wrong. This bug goes all the > way back to 99cb0dbd47a1. In fact, I understand it this way: the 99cb0dbd47a1 only introduce file-backed THP for VMA with MAP_DENYWRITE, denying write directly not to truncate pagecache when it is opened. And eb6ecbed0aa2 will to truncate pagecache when DSO is opened by a writer, then will trigger ... It seems 'Fixes: eb6ecbed0aa2' is more reasonable. >