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

[David Hildenbrand <david@redhat.com>]

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) {
			...
		}
	}
	...
}

-- 
Cheers,

David / dhildenb