Re: [PATCH] mm/memory-failure: fix VM_BUG_ON_PAGE(PagePoisoned(page)) when unpoison memory

[Miaohe Lin <linmiaohe@huawei.com>]

On 2024/7/17 17:01, David Hildenbrand wrote:
> On 16.07.24 04:34, Miaohe Lin wrote:
>> On 2024/7/16 0:16, David Hildenbrand wrote:
>>> On 15.07.24 08:23, Miaohe Lin wrote:
>>>> On 2024/7/13 5:09, Andrew Morton wrote:
>>>>> On Fri, 12 Jul 2024 14:42:49 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:
>>>>>
>>>>>> When I did memory failure tests recently, below panic occurs:
>>>>>>
>>>>>> page dumped because: VM_BUG_ON_PAGE(PagePoisoned(page))
>>>>>> kernel BUG at include/linux/page-flags.h:616!
>>>>>> Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
>>>>>> CPU: 3 PID: 720 Comm: bash Not tainted 6.10.0-rc1-00195-g148743902568 #40
>>>>>> RIP: 0010:unpoison_memory+0x2f3/0x590
>>>>>> RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
>>>>>> RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
>>>>>> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
>>>>>> RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
>>>>>> R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
>>>>>> R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
>>>>>> FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
>>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>> CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
>>>>>> Call Trace:
>>>>>>    <TASK>
>>>>>>    unpoison_memory+0x2f3/0x590
>>>>>>    simple_attr_write_xsigned.constprop.0.isra.0+0xb3/0x110
>>>>>>    debugfs_attr_write+0x42/0x60
>>>>>>    full_proxy_write+0x5b/0x80
>>>>>>    vfs_write+0xd5/0x540
>>>>>>    ksys_write+0x64/0xe0
>>>>>>    do_syscall_64+0xb9/0x1d0
>>>>>>    entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>>>>> RIP: 0033:0x7f08f0314887
>>>>>> RSP: 002b:00007ffece710078 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
>>>>>> RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f08f0314887
>>>>>> RDX: 0000000000000009 RSI: 0000564787a30410 RDI: 0000000000000001
>>>>>> RBP: 0000564787a30410 R08: 000000000000fefe R09: 000000007fffffff
>>>>>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000009
>>>>>> R13: 00007f08f041b780 R14: 00007f08f0417600 R15: 00007f08f0416a00
>>>>>>    </TASK>
>>>>>> Modules linked in: hwpoison_inject
>>>>>> ---[ end trace 0000000000000000 ]---
>>>>>> RIP: 0010:unpoison_memory+0x2f3/0x590
>>>>>> RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
>>>>>> RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
>>>>>> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
>>>>>> RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
>>>>>> R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
>>>>>> R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
>>>>>> FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
>>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>> CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
>>>>>> Kernel panic - not syncing: Fatal exception
>>>>>> Kernel Offset: 0x31c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
>>>>>> ---[ end Kernel panic - not syncing: Fatal exception ]---
>>>>>>
>>>>>> The root cause is that unpoison_memory() tries to check the PG_HWPoison
>>>>>> flags of an uninitialized page. So VM_BUG_ON_PAGE(PagePoisoned(page)) is
>>>>>> triggered.
>>>>>
>>>>> I'm not seeing the call path.  Is this BUG happening via
>>>>>
>>>>> static __always_inline void __ClearPage##uname(struct page *page)    \
>>>>> {                                    \
>>>>>      VM_BUG_ON_PAGE(!Page##uname(page), page);            \
>>>>>      page->page_type |= PG_##lname;                    \
>>>>> }
>>>>>
>>>>> ?
>>>>>
>>>>> If so, where's the callsite?
>>>>
>>>> It is BUG on PF_ANY():
>>>>
>>>> PAGEFLAG(HWPoison, hwpoison, PF_ANY)
>>>>
>>>> #define PF_ANY(page, enforce)    PF_POISONED_CHECK(page)
>>>>
>>>> #define PF_POISONED_CHECK(page) ({                    \
>>>>      VM_BUG_ON_PGFLAGS(PagePoisoned(page), page);        \
>>>>      page; })
>>>>
>>>> #define    PAGE_POISON_PATTERN    -1l
>>>> static inline int PagePoisoned(const struct page *page)
>>>> {
>>>>      return READ_ONCE(page->flags) == PAGE_POISON_PATTERN;
>>>> }
>>>>
>>>> The offlined pages will have page->flags set to PAGE_POISON_PATTERN while pfn is still valid:
>>>>
>>>> offline_pages
>>>>     remove_pfn_range_from_zone
>>>>       page_init_poison
>>>>         memset(page, PAGE_POISON_PATTERN, size);
>>>
>>> Worth noting that this happens after __offline_isolated_pages() marked the covering sections as offline.
>>>
>>> Are we missing a pfn_to_online_page() check somewhere, or are we racing with offlining code that marks the section offline?
>>
>> I was thinking about to use pfn_to_online_page() instead of pfn_to_page() in unpoison_memory() so we can get rid of offlined pages.
>> But there're ZONE_DEVICE pages. They're not-onlined too. And unpoison_memory() should work for them. So we can't simply use
>> pfn_to_online_page() in that. Or am I miss something?
> 
> Right, pfn_to_online_page() does not detect ZONE_DEVICE. That has to be handled separately if pfn_to_online_page() would fail.
> 
> ... which is what we do in memory_failure():
> 
> p = pfn_to_online_page(pfn);
> if (!p) {
>     if (pfn_valid(pfn)) {
>         pgmap = get_dev_pagemap(pfn, NULL);
>         put_ref_page(pfn, flags);
>         if (pgmap) {
>             ...
>         }
>     }
>     ...
> }

Yup, this will be a good alternative. But will it be better to simply check PagePoisoned() instead?

Thanks.
.