linux-kernel - Re: [PATCH 0/3] mm: treewide: make get_free

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Message-ID: <3e798b9e-4915-404f-9197-ed3c32587141@kernel.org>
Date: Mon, 20 Oct 2025 08:58:50 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Matthew Wilcox <willy@...radead.org>, Mike Rapoport <rppt@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Brendan Jackman <jackmanb@...gle.com>, David Hildenbrand <david@...hat.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Johannes Weiner <hannes@...xchg.org>, Julia Lawall <Julia.Lawall@...ia.fr>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Michal Hocko
 <mhocko@...e.com>, Suren Baghdasaryan <surenb@...gle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Zi Yan <ziy@...dia.com>,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 0/3] mm: treewide: make get_free_pages() and return void *

On 19. 10. 25, 2:30, Matthew Wilcox wrote:
> On Sat, Oct 18, 2025 at 12:29:59PM +0300, Mike Rapoport wrote:
>> Vast majority of allocations that use get_free_pages() and its derivatives
>> cast the returned unsigned long to a pointer and then cast it back to
>> unsigned long when freeing the memory.
>>
>> These castings are useless and only obfuscate the code.
>>
>> Make get_free_pages() and friends return 'void *' and free_pages() accept
>> 'void *' as its address parameter.
> 
> No.  Linus has rejected this change before.  I can't find it now, it was
> a long time ago.  Most of them shouldn't be using get_free_pages() at
> all, they should be using kmalloc().

I'd be interested in the refusal thread (what was the rejection exactly 
about). In a need of whole pages, why would I want to alloc more for 
metadata (using k*alloc)? Or what am I missing?

thanks,
-- 
js
suse labs