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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41AE8C433F5 for ; Fri, 22 Apr 2022 17:37:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BFFA86B0073; Fri, 22 Apr 2022 13:37:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BAED76B0074; Fri, 22 Apr 2022 13:37:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A9D136B0075; Fri, 22 Apr 2022 13:37:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id 994776B0073 for ; Fri, 22 Apr 2022 13:37:08 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 67607120931 for ; Fri, 22 Apr 2022 17:37:08 +0000 (UTC) X-FDA: 79385220936.19.835CB35 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) by imf24.hostedemail.com (Postfix) with ESMTP id 8CDF218003F for ; Fri, 22 Apr 2022 17:37:03 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R451e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=xuyu@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VAos8w4_1650649020; Received: from 30.236.54.156(mailfrom:xuyu@linux.alibaba.com fp:SMTPD_---0VAos8w4_1650649020) by smtp.aliyun-inc.com(127.0.0.1); Sat, 23 Apr 2022 01:37:01 +0800 Message-ID: <83e32a86-6e36-15ed-ef7d-5b00b8d7db59@linux.alibaba.com> Date: Sat, 23 Apr 2022 01:37:00 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v2] mm/memory-failure.c: skip huge_zero_page in memory_failure() Content-Language: en-US To: Yang Shi Cc: David Hildenbrand , Linux MM , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Andrew Morton , Miaohe Lin , Oscar Salvador References: <497d3835612610e370c74e697ea3c721d1d55b9c.1649775850.git.xuyu@linux.alibaba.com> <47144bd6-4de0-26e3-a993-6075714e7f33@redhat.com> <548416ab-1700-4e0e-5e96-e1f1432cd58b@linux.alibaba.com> From: Yu Xu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8CDF218003F X-Stat-Signature: gcb5idi4m7yzcghkudhrfijeuh9t1i5x X-Rspam-User: Authentication-Results: imf24.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf24.hostedemail.com: domain of xuyu@linux.alibaba.com designates 115.124.30.130 as permitted sender) smtp.mailfrom=xuyu@linux.alibaba.com X-Rspamd-Server: rspam09 X-HE-Tag: 1650649023-710374 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: On 4/23/22 12:03 AM, Yang Shi wrote: > On Thu, Apr 21, 2022 at 8:27 PM Yu Xu wrote: >> >> On 4/22/22 1:53 AM, Yang Shi wrote: >>> On Thu, Apr 21, 2022 at 2:03 AM David Hildenbrand wrote: >>>> >>>> On 21.04.22 01:38, Yang Shi wrote: >>>>> On Tue, Apr 12, 2022 at 8:11 AM Xu Yu wrote: >>>>>> >>>>>> Kernel panic when injecting memory_failure for the global huge_zero_page, >>>>>> when CONFIG_DEBUG_VM is enabled, as follows. >>>>>> >>>>>> [ 5.582720] Injecting memory failure for pfn 0x109ff9 at process virtual address 0x20ff9000 >>>>>> [ 5.583786] page:00000000fb053fc3 refcount:2 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x109e00 >>>>>> [ 5.584900] head:00000000fb053fc3 order:9 compound_mapcount:0 compound_pincount:0 >>>>>> [ 5.585796] flags: 0x17fffc000010001(locked|head|node=0|zone=2|lastcpupid=0x1ffff) >>>>>> [ 5.586712] raw: 017fffc000010001 0000000000000000 dead000000000122 0000000000000000 >>>>>> [ 5.587640] raw: 0000000000000000 0000000000000000 00000002ffffffff 0000000000000000 >>>>>> [ 5.588565] page dumped because: VM_BUG_ON_PAGE(is_huge_zero_page(head)) >>>>>> [ 5.589398] ------------[ cut here ]------------ >>>>>> [ 5.589952] kernel BUG at mm/huge_memory.c:2499! >>>>>> [ 5.590516] invalid opcode: 0000 [#1] PREEMPT SMP PTI >>>>>> [ 5.591120] CPU: 6 PID: 553 Comm: split_bug Not tainted 5.18.0-rc1+ #11 >>>>>> [ 5.591904] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 3288b3c 04/01/2014 >>>>>> [ 5.592817] RIP: 0010:split_huge_page_to_list+0x66a/0x880 >>>>>> [ 5.593469] Code: 84 9b fb ff ff 48 8b 7c 24 08 31 f6 e8 9f 5d 2a 00 b8 b8 02 00 00 e9 e8 fb ff ff 48 c7 c6 e8 47 3c 82 4c b >>>>>> [ 5.595806] RSP: 0018:ffffc90000dcbdf8 EFLAGS: 00010246 >>>>>> [ 5.596434] RAX: 000000000000003c RBX: 0000000000000001 RCX: 0000000000000000 >>>>>> [ 5.597322] RDX: 0000000000000000 RSI: ffffffff823e4c4f RDI: 00000000ffffffff >>>>>> [ 5.598162] RBP: ffff88843fffdb40 R08: 0000000000000000 R09: 00000000fffeffff >>>>>> [ 5.598999] R10: ffffc90000dcbc48 R11: ffffffff82d68448 R12: ffffea0004278000 >>>>>> [ 5.599849] R13: ffffffff823c6203 R14: 0000000000109ff9 R15: ffffea000427fe40 >>>>>> [ 5.600693] FS: 00007fc375a26740(0000) GS:ffff88842fd80000(0000) knlGS:0000000000000000 >>>>>> [ 5.601640] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>>>> [ 5.602304] CR2: 00007fc3757c9290 CR3: 0000000102174006 CR4: 00000000003706e0 >>>>>> [ 5.603139] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >>>>>> [ 5.603977] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >>>>>> [ 5.604806] Call Trace: >>>>>> [ 5.605101] >>>>>> [ 5.605357] ? __irq_work_queue_local+0x39/0x70 >>>>>> [ 5.605904] try_to_split_thp_page+0x3a/0x130 >>>>>> [ 5.606430] memory_failure+0x128/0x800 >>>>>> [ 5.606888] madvise_inject_error.cold+0x8b/0xa1 >>>>>> [ 5.607444] __x64_sys_madvise+0x54/0x60 >>>>>> [ 5.607915] do_syscall_64+0x35/0x80 >>>>>> [ 5.608347] entry_SYSCALL_64_after_hwframe+0x44/0xae >>>>>> [ 5.608949] RIP: 0033:0x7fc3754f8bf9 >>>>>> [ 5.609374] Code: 01 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 8 >>>>>> [ 5.611554] RSP: 002b:00007ffeda93a1d8 EFLAGS: 00000217 ORIG_RAX: 000000000000001c >>>>>> [ 5.612441] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc3754f8bf9 >>>>>> [ 5.613269] RDX: 0000000000000064 RSI: 0000000000003000 RDI: 0000000020ff9000 >>>>>> [ 5.614108] RBP: 00007ffeda93a200 R08: 0000000000000000 R09: 0000000000000000 >>>>>> [ 5.614946] R10: 00000000ffffffff R11: 0000000000000217 R12: 0000000000400490 >>>>>> [ 5.615787] R13: 00007ffeda93a2e0 R14: 0000000000000000 R15: 0000000000000000 >>>>>> [ 5.616626] >>>>>> >>>>>> This makes huge_zero_page bail out explicitly before split in >>>>>> memory_failure(), thus the panic above won't happen again. >>>>> >>>>> Skipping huge_zero_page in error injection is ok to me, but I'm >>>>> actually wondering whether raising BUG is overkilling for splitting >>>>> huge_zero_page or not. Returning -EBUSY should be totally fine. >>>> >>>> I tend to agree. Just failing with -EBUSY might be cleaner. Most >>>> probably we want to catch any bogus code here that does something we >>>> don't really expect -- splitting the huge zeropage makes 0 sense. >>> >>> Yeah, the huge zero page can't be met from normal paths other than >>> memory failure, but memory failure is a valid caller. So I tend to >>> replace the BUG to WARN + returning -EBUSY. If we don't care about the >>> reason code in memory failure, we don't have to touch memory failure. >> >> To make sure I understand this correctly, do you mean the following? > > Yes. And you should be able to drop your old patch as well. Thanks! And I have one more question, if doing so, the huge_zero_page will be set PG_has_hwpoisoned in memory_failure(), although PG_has_hwpoisoned is not checked in set_huge_zero_page(). It works, but isn't it a bit strange? To this point, as well as you mentioned that "the huge zero page can't be met from normal paths other than memory failure", I prefer to skip huge_zero_page in memory_failure(). How do you think? > >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index c468fee595ff..3bb464509518 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -2496,10 +2496,12 @@ int split_huge_page_to_list(struct page *page, struct >> list_head *list) >> int extra_pins, ret; >> pgoff_t end; >> >> - VM_BUG_ON_PAGE(is_huge_zero_page(head), head); >> VM_BUG_ON_PAGE(!PageLocked(head), head); >> VM_BUG_ON_PAGE(!PageCompound(head), head); >> >> + if (VM_WARN_ON_ONCE_PAGE(is_huge_zero_page(head), head)) >> + return -EBUSY; >> + >> if (PageWriteback(head)) >> return -EBUSY; >> >> >>> >>>> >>>> -- >>>> Thanks, >>>> >>>> David / dhildenb >>>> >>>> >> >> -- >> Thanks, >> Yu -- Thanks, Yu