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From: Naoya Horiguchi To: Miaohe Lin , Xu Yu Cc: akpm@linux-foundation.org, Linux-MM , Naoya Horiguchi Subject: Re: [PATCH] mm/memory-failure.c: bail out early if huge zero page Message-ID: <20220412090907.GA350357@u2004> References: <49273e6688d7571756603dac996692a15f245d58.1649603963.git.xuyu@linux.alibaba.com> <8f06b79b-aeff-3479-a3cc-c0a649dc770b@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <8f06b79b-aeff-3479-a3cc-c0a649dc770b@huawei.com> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: o7nj6od9yi7bz7ps6zod94xcx5b9j9my Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=PcFKHRph; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf12.hostedemail.com: domain of naoya.horiguchi@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=naoya.horiguchi@linux.dev X-Rspamd-Queue-Id: D7D4A4001E X-HE-Tag: 1649754556-821758 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 Mon, Apr 11, 2022 at 10:18:26AM +0800, Miaohe Lin wrote: > On 2022/4/10 23:22, 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] > > > > Thanks for the report and the patch! > > I remember I and Naoya discussed the try_to_split_thp_page in memory_failure might come > across non-lru movable compound page and huge_zero_page. We fixed the non-lru movable > compound page case but conclude huge_zero_page won't reach here due to the HWPoisonHandlable() > check. But we missed the MF_COUNT_INCREASED case where HWPoisonHandlable() is skipped. > > > In fact, huge_zero_page is unhandlable currently in either soft offline > > or memory failure injection. With CONFIG_DEBUG_VM disabled, > > huge_zero_page is bailed out when checking HWPoisonHandlable() in > > get_any_page(), or checking page mapping in split_huge_page_to_list(). > > > > This makes huge_zero_page bail out early in madvise_inject_error(), and > > panic above won't happen again. > > It seems this issue is expected to happen only in madvise_inject_error case because > MF_COUNT_INCREASED is only set here. So this fix should do the right thing. But I > don't know whether bail out early for huge_zero_page is suitable. > > Hi Naoya, what do you think? Thank you for reporting. ... > > @@ -1087,12 +1087,21 @@ static int madvise_inject_error(int behavior, > > return ret; > > pfn = page_to_pfn(page); > > > > + head = compound_head(page); > > + if (unlikely(is_huge_zero_page(head))) { > > + pr_warn("Unhandlable attempt to %s pfn %#lx at process virtual address %#lx\n", > > + behavior == MADV_SOFT_OFFLINE ? "soft offline" : > > + "inject memory failure for", > > + pfn, start); > > + return -EINVAL; > > + } This check is about the detail of error handling, so I feel it desirable to do this in memory_failure(). And memory errors on huge zero page is the real scenario, so it seems to me better to make this case injectable rather than EINVAL. How about checking is_huge_zero_page() before try_to_split_thp_page()? The result should be consistent with the results when called by other memory_failure()'s callers like MCE handler and hard_offline_page_store(). diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 9b76222ee237..771fb4fc626c 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1852,6 +1852,12 @@ int memory_failure(unsigned long pfn, int flags) } if (PageTransHuge(hpage)) { + if (is_huge_zero_page(hpage)) { + action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED); + res = -EBUSY; + goto unlock_mutex; + } + /* * The flag must be set after the refcount is bumped * otherwise it may race with THP split. Thanks, Naoya Horiguchi