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Message-ID: <1af81f0e-6500-9719-20be-505851673b58@huawei.com>
Date: Mon, 23 Dec 2024 10:55:39 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: David Hildenbrand <david@...hat.com>, <akpm@...ux-foundation.org>, Dan
Williams <dan.j.williams@...el.com>
CC: <nao.horiguchi@...il.com>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mm/memory-failure: fix
VM_BUG_ON_PAGE(PagePoisoned(page)) when unpoison memory
On 2024/12/20 16:50, David Hildenbrand wrote:
> On 20.12.24 03:35, Miaohe Lin wrote:
>> On 2024/12/19 20:18, David Hildenbrand wrote:
>>> On 19.12.24 12:52, Miaohe Lin 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. This can be reproduced by below steps:
>>>> 1.Offline memory block:
>>>> echo offline > /sys/devices/system/memory/memory12/state
>>>> 2.Get offlined memory pfn:
>>>> page-types -b n -rlN
>>>> 3.Write pfn to unpoison-pfn
>>>> echo <pfn> > /sys/kernel/debug/hwpoison/unpoison-pfn
>>>>
>>>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>>>> ---
>>>> v2: Use pfn_to_online_page per David. Thanks.
>>>> ---
>>>> mm/memory-failure.c | 14 +++++++++++---
>>>> 1 file changed, 11 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>>>> index a7b8ccd29b6f..02be0596ce67 100644
>>>> --- a/mm/memory-failure.c
>>>> +++ b/mm/memory-failure.c
>>>> @@ -2556,10 +2556,18 @@ int unpoison_memory(unsigned long pfn)
>>>> static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
>>>> DEFAULT_RATELIMIT_BURST);
>>>> - if (!pfn_valid(pfn))
>>>> - return -ENXIO;
>>>> + p = pfn_to_online_page(pfn);
>>>> + if (!p) {
>>>> + struct dev_pagemap *pgmap;
>>>> - p = pfn_to_page(pfn);
>>>> + if (!pfn_valid(pfn))
>>>> + return -ENXIO;
>>>> + pgmap = get_dev_pagemap(pfn, NULL);
>>>> + if (!pgmap)
>>>> + return -ENXIO;
>>>> + put_dev_pagemap(pgmap);
>>>> + p = pfn_to_page(pfn);
>>>> + }
>>>
>>> Hm, I wonder if we can do anything reasonable with ZONE_DEVICE pages here?
>>
>> All I can see in unpoison_memory() is folio_test_clear_hwpoison() for ZONE_DEVICE pages.
>
> IIRC, it can only be triggered via debugfs in special kernel configs. So chances are this was never ever actually run against a ZONE_DEVICE page.
If ZONE_DEVICE pages are never expected, we can simply filter them out.
>
>>
>>>
>>> CCing Dan, maybe he knows if this interface used to do something reasonable with ZONE_DEVICE pages.
>>>
>>> Also, I'm not sure about using the page after doing the put_dev_pagemap(). Likely we would have to do that at the before exiting from this function.
>>
>> IMHO, the page can be used after doing put_dev_pagemap(). The page should still be
>> available while it has HWPoison set.
>
> 1) Why do you think it can be used afterwards? :)
>
> 2) At that point in time you don't even know yet if the page is
> HWPoisoned! That check is performed later
>
> 3) From GUP code, I recall that we must keep the pagemap referenced
> until we grabbed a page/folio reference.
I think you're right, David. I missed this case. :)
Thanks.
.
>
> Or are you worrying about memory offline? That
>> might not be the scope of this problem. But I might be miss something.
>
> I suspect unpoison_memory() doesn't do with ZONE_DEVICE pages what it should be doing. Maybe I'm wrong, it would be great to get feedback from Dan.
>
>
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