linux-kernel - Re: [PATCH v1] mm/gup: remove (VM_)BUG

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Message-ID: <8d995aa8-31f4-4bbe-b79a-c9e1c2ade1fb@redhat.com>
Date: Thu, 5 Jun 2025 14:29:01 +0200
From: David Hildenbrand <david@...hat.com>
To: Vlastimil Babka <vbabka@...e.cz>, John Hubbard <jhubbard@...dia.com>,
 linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Mike Rapoport
 <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Jason Gunthorpe <jgg@...pe.ca>,
 Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH v1] mm/gup: remove (VM_)BUG_ONs

On 05.06.25 10:48, Vlastimil Babka wrote:
> On 6/5/25 08:08, David Hildenbrand wrote:
>> On 05.06.25 07:37, Vlastimil Babka wrote:
>>> On 6/5/25 03:07, John Hubbard wrote:
>>>> On 6/4/25 7:05 AM, David Hildenbrand wrote:
>>>>> Especially once we hit one of the assertions in
>>>>> sanity_check_pinned_pages(), observing follow-up assertions failing
>>>>> in other code can give good clues about what went wrong, so use
>>>>> VM_WARN_ON_ONCE instead.
>>>>>
>>>>> While at it, let's just convert all VM_BUG_ON to VM_WARN_ON_ONCE as
>>>>> well. Add one comment for the pfn_valid() check.
>>>>
>>>> It would be a nice touch to add Linus' notes here, with the BUG() history
>>>> and all. It answers a FAQ about BUG vs. WARN* that is really nice
>>>> to have in the commit log.
>>>
>>> Perhaps then rather put it somewhere appropriate in Documentation/process/
>>> than a random commit log?
>>
>> I mean, I documented most of that already in coding-style.rst. :)
> 
> Thanks for the reminder, looks good to me :)
> 
>> The full BUG history is not in there, but not sure if that is really required if ...
>> we're not supposed to use it.
> 
> We could put links to the history excursion email (and appropriate older
> emails you link in the commit log below) to the References appendix of the
> coding-style file, but it's not that critical.

Not sure if it's really of value. I mean, whoever questions the rules 
(for whatever reason ;) ) should probably look at the git log ...

-- 
Cheers,

David / dhildenb