Re: mm: Regression with v7.0-rc1 on RISC-V

[Zi Yan]

On 24 Feb 2026, at 12:07, David Hildenbrand wrote:

>> David Hildenbrand (Arm) <david@xxxxxxxxxx> hat am 24.02.2026 12:00 CET geschrieben:
>>
>>
>>
>>
>>
>> On 2/24/26 09:37, Ron Economos wrote:
>>
>>> I'm getting a BUG dump during shutdown with Linux v7.0-rc1 on RISC-V.
>>>
>>>
>>>
>>> [  OK  ] Reached target shutdown.target - System Shutdown.
>>>
>>> [  OK  ] Reached target final.target - Late Shutdown Services.
>>>
>>> [  OK  ] Finished systemd-reboot.service - System Reboot.
>>>
>>> [  OK  ] Reached target reboot.target - System Reboot.
>>>
>>> [  173.985249] BUG: Bad page state in process shutdown  pfn:f8850
>>>
>>> [  173.985311] page: refcount:1 mapcount:0 mapping:0000000000000000
>>>
>>> index:0x0 pfn:0xf8850
>>>
>>> [  173.985336] flags: 0xffff80000000000(node=0|zone=0|
>>>
>>> lastcpupid=0x1ffff) CMA
>>>
>>> [  173.985365] raw: 0ffff80000000000 ffffffc501e21448 ffffffc600f2ae88
>>>
>>> 0000000000000000
>>>
>>> [  173.985386] raw: 0000000000000000 0000000000000000 00000001ffffffff
>>>
>>> 0000000000000000
>>>
>>> [  173.985403] page dumped because: nonzero _refcount
>>
>> So, we're freeing something from CMA in cma_release().
>>
>>
>>
>> In cma_release() we iterate all pages to decrement their refcount
>>
>>
>>
>> VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)));
>>
>>
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>> I would expect that this would fire already if there is still a page
>>
>> referenced.
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>>
>>
>> Are you running with CONFIG_DEBUG_VM=y ?
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>>
>>
>>
>>
>> --
>>
>> Cheers,
>>
>>
>>
>> David
>
> Thinking again without my computer at hand … isn‘t the call completely optimized out without CONFIG_DEBUG_VM?
>
>
>
> At least that’s what I remember.

Right. Without CONFIG_DEBUG_VM=y, VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)))
and is_check_pages_enabled(), which leads to free_page_is_bad()’s
“page dumped because: nonzero _refcount”, are disabled.

It seems to me that someone else bump the page refcount between
VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn))) and free_page_is_bad().


Best Regards,
Yan, Zi