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

[Miaohe Lin]

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@xxxxxxxxxx> 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?

Thanks.
.