linux-kernel - Re: [RFC PATCH 05/12] fs/proc/task_mmu: refactor pagemap_pmd

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Message-ID: <dac763e0-3912-439d-a9c3-6e54bf3329c6@redhat.com>
Date: Mon, 27 Oct 2025 17:31:54 +0100
From: David Hildenbrand <david@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Jason Gunthorpe <jgg@...pe.ca>
Cc: Gregory Price <gourry@...rry.net>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Janosch Frank <frankja@...ux.ibm.com>,
 Claudio Imbrenda <imbrenda@...ux.ibm.com>,
 Alexander Gordeev <agordeev@...ux.ibm.com>,
 Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>, Zi Yan <ziy@...dia.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>, Nico Pache
 <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
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 Oscar Salvador <osalvador@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
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 Matthew Brost <matthew.brost@...el.com>,
 Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
 Byungchul Park <byungchul@...com>, Ying Huang
 <ying.huang@...ux.alibaba.com>, Alistair Popple <apopple@...dia.com>,
 Pedro Falcato <pfalcato@...e.de>, Pasha Tatashin
 <pasha.tatashin@...een.com>, Rik van Riel <riel@...riel.com>,
 Harry Yoo <harry.yoo@...cle.com>, kvm@...r.kernel.org,
 linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH 05/12] fs/proc/task_mmu: refactor pagemap_pmd_range()

> 
> I don't love the union.
> 
> How would we determine what type it is, we'd have to have some
> generic_leaf_entry_t type or something to contain the swap type field and then
> cast and... is it worth it?
> 
> Intent of non-present was to refer to not-swap swapentry. It's already a
> convention that exists, e.g. is_pmd_non_present_folio_entry().

Just noting that this was a recent addition (still not upstream) that 
essentially says "there is a folio here, but it's not in an ordinary 
present page table entry.

So we could change that to something better.

-- 
Cheers

David / dhildenb