Message-ID: <1fee1926-638b-4852-b98f-a0423a94b7f8@redhat.com>
Date: Mon, 30 Jun 2025 10:16:26 +0200
From: David Hildenbrand <david@...hat.com>
To: Harry Yoo <harry.yoo@...cle.com>
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Subject: Re: [PATCH RFC 07/29] mm/migrate: rename isolate_movable_page() to
 isolate_movable_ops_page()

On 30.06.25 10:04, Harry Yoo wrote:
> On Wed, Jun 18, 2025 at 07:39:50PM +0200, David Hildenbrand wrote:
>> ... and start moving back to per-page things that will absolutely not be
>> folio things in the future. Add documentation and a comment that the
>> remaining folio stuff (lock, refcount) will have to be reworked as well.
>>
>> While at it, convert the VM_BUG_ON() into a WARN_ON_ONCE() and handle
>> it gracefully (relevant with further changes), and convert a
>> WARN_ON_ONCE() into a VM_WARN_ON_ONCE_PAGE().
>>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
>> ---
> 
> Haha yeah, back to pages after folio conversion :P
> But makes sense.
> 
> Reviewed-by: Harry Yoo <harry.yoo@...cle.com>
> 
> Side question: In the future, maybe we will be unable to tell whether
> a page is compound or not, without first inspecting page->memdesc?
> (e.g., struct slab could have an order and a pointer to the head page...
> just imagining).

Right, it's not really clear what we would do in the future, but for 
anything that allocates a memdesc, that is possible.

We wouldn't even need the "head" + "tail" bit indication.

For things without an allocated memdesc (e.g., PageOffline), maybe 
compound pages will simply not apply.

Likely, the concept of compound pages as we knew it will go away.

-- 
Cheers,

David / dhildenb

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