On 2024/8/2 4:24, David Hildenbrand wrote:
> On 19.07.24 05:55, Miaohe Lin wrote:
>> On 2024/7/18 13:15, David Hildenbrand wrote:
>>> On 18.07.24 05:04, Miaohe Lin wrote:
>>>> 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@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?
>>>>>
>>>>> 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?
>>>
>>> The memmap of offline memory sections shall not be touched, so .... don't touch it ;)
>>>
>>> Especially because that PagePoisoned() check is non-sensical without poisoining-during-memmap-init. You would still work with memory in offline sections.
>>>
>>> I think the code is even wrong in that regard: we allow for memory offlining to work with HWPoisoned pages, see __offline_isolated_pages(). Staring at unpoison_memory(), we might be putting these pages back to the buddy? Which is completely wrong.
>>
>> I agree with you. Thanks for detailed explanation. :)
>> Thanks David.
>
> So ... I assume there will be a new patch? :)
I was just back from my two-weeks holidays. ;) I will try to send a new version when possible.
Thanks.
.
