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[2003:cb:c702:de00:711b:76af:b335:9b70]) by smtp.gmail.com with ESMTPSA id l8-20020a5d5608000000b00207ab405d15sm1746196wrv.42.2022.04.21.02.03.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Apr 2022 02:03:26 -0700 (PDT) Message-ID: <47144bd6-4de0-26e3-a993-6075714e7f33@redhat.com> Date: Thu, 21 Apr 2022 11:03:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.2 Subject: Re: [PATCH v2] mm/memory-failure.c: skip huge_zero_page in memory_failure() To: Yang Shi , Xu Yu Cc: Linux MM , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Andrew Morton , Miaohe Lin , Oscar Salvador References: <497d3835612610e370c74e697ea3c721d1d55b9c.1649775850.git.xuyu@linux.alibaba.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7E2BA160023 X-Rspam-User: Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hjdoTs3O; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf08.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=david@redhat.com X-Stat-Signature: soo9jxp7xtwg6ary4p67r31hwzu5d3bw X-HE-Tag: 1650531808-602971 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 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. -- Thanks, David / dhildenb