linux-kernel - Re: [PATCH v1 2/4] mm: smaller folio_pte

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Message-ID: <1d98e96b-4bc9-45c1-9861-e0f3c5930ec2@redhat.com>
Date: Wed, 2 Jul 2025 10:48:20 +0200
From: David Hildenbrand <david@...hat.com>
To: Oscar Salvador <osalvador@...e.de>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
 Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Zi Yan <ziy@...dia.com>,
 Matthew Brost <matthew.brost@...el.com>,
 Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
 Byungchul Park <byungchul@...com>, Gregory Price <gourry@...rry.net>,
 Ying Huang <ying.huang@...ux.alibaba.com>,
 Alistair Popple <apopple@...dia.com>, Pedro Falcato <pfalcato@...e.de>,
 Rik van Riel <riel@...riel.com>, Harry Yoo <harry.yoo@...cle.com>
Subject: Re: [PATCH v1 2/4] mm: smaller folio_pte_batch() improvements

On 02.07.25 10:42, Oscar Salvador wrote:
> On Fri, Jun 27, 2025 at 01:55:08PM +0200, David Hildenbrand wrote:
>> Let's clean up a bit:
>>
>> (1) No need for start_ptep vs. ptep anymore, we can simply use ptep
>>
>> (2) Let's switch to "unsigned int" for everything
>>
>> (3) We can simplify the code by leaving the pte unchanged after the
>>      pte_same() check.
>>
>> (4) Clarify that we should never exceed a single VMA; it indicates a
>>      problem in the caller.
>>
>> No functional change intended.
>>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
> 
> Hi David :-),
> 
> I have to confess that I fell in the same trap as Lorenzo wrt.
> __pte_batch_clear_ignored changing the pte value.
> So I'm not sure if it would be nice to place a little comment in
> __pte_batch_clear_ignored claryfing that pte's value remains unchanged ?

I mean, that's how all our pte modification functions work, really? :)

Thanks!

-- 
Cheers,

David / dhildenb