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(p200300d82f300b00cea90deed607041d.dip0.t-ipconnect.de. [2003:d8:2f30:b00:cea9:dee:d607:41d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429eb40617asm851462f8f.10.2025.11.05.13.15.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Nov 2025 13:15:54 -0800 (PST) Message-ID: <563246df-cca4-4d21-bad0-7269ab5a419c@gmail.com> Date: Wed, 5 Nov 2025 22:15:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/16] mm: introduce leaf entry type and use to simplify leaf entry logic To: Lorenzo Stoakes Cc: Gregory Price , Matthew Wilcox , Andrew Morton , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Sven Schnelle , Peter Xu , Alexander Viro , Christian Brauner , Jan Kara , Arnd Bergmann , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Muchun Song , Oscar Salvador , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Axel Rasmussen , Yuanchu Xie , Wei Xu , Kemeng Shi , Kairui Song , Nhat Pham , Baoquan He , Chris Li , SeongJae Park , Jason Gunthorpe , Leon Romanovsky , Xu Xin , Chengming Zhou , Jann Horn , Miaohe Lin , Naoya Horiguchi , Pedro Falcato , Pasha Tatashin , Rik van Riel , Harry Yoo , Hugh Dickins , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, damon@lists.linux.dev References: <2c75a316f1b91a502fad718de9b1bb151aafe717.1762171281.git.lorenzo.stoakes@oracle.com> <373a0e43-c9bf-4b5b-8d39-4f71684ef883@lucifer.local> <7f507cb7-f6aa-4f52-b0b5-8f0f27905122@gmail.com> <2d1f420e-c391-487d-a3cc-536eb62f3518@lucifer.local> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <2d1f420e-c391-487d-a3cc-536eb62f3518@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 76D4E20005 X-Stat-Signature: 8p6s1o39a1qex8qtdyw4jixha6g9z7nn X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1762377357-703375 X-HE-Meta: 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 e3ui9ysA 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 05.11.25 22:08, Lorenzo Stoakes wrote: > On Wed, Nov 05, 2025 at 09:11:45PM +0100, David Hildenbrand (Red Hat) wrote: >> On 05.11.25 21:05, Lorenzo Stoakes wrote: >>> On Wed, Nov 05, 2025 at 03:01:00PM -0500, Gregory Price wrote: >>>> On Wed, Nov 05, 2025 at 07:52:36PM +0000, Lorenzo Stoakes wrote: >>>>> On Wed, Nov 05, 2025 at 02:25:34PM -0500, Gregory Price wrote: >>>>>> On Wed, Nov 05, 2025 at 07:06:11PM +0000, Matthew Wilcox wrote: >>>>> I thought about doing this but it doesn't really work as the type is >>>>> _abstracted_ from the architecture-specific value, _and_ we use what is >>>>> currently the swp_type field to identify what this is. >>>>> >>>>> So we would lose the architecture-specific information that any 'hardware leaf' >>>>> entry would require and not be able to reliably identify it without losing bits. >>>>> >>>>> Trying to preserve the value _and_ correctly identify it as a present entry >>>>> would be difficult. >>>>> >>>>> And I _really_ didn't want to go on a deep dive through all the architectures to >>>>> see if we could encode it differently to allow for this. >>>>> >>>>> Rather I think it's better to differentiate between s/w + h/w leaf entries. >>>>> >>>> >>>> Reasonable - names are hard, but just about anything will be better than swp_entry. >>>> >>>> SWE / sw_entry seems perfectly reasonable. >>> >>> I'm not a lover of 'sw' in there it's just... eye-stabby. Is that a word? >>> >>> I am quite fond of my suggested soft_leaf_t, softleaf_xxx() >> >> We do have soft_dirty. >> >> It will get interesting with pte_swp_soft_dirty() :) > > Hmm but that's literally a swap entry, and is used against an actual PTE entry > not an abstracted s/w leaf entry so I doubt that'd require renaming on any > level. It's used on migration entries as well. Just like pte_swp_uffd_wp(). So, it's ... tricky :) But maybe I am missing your point (my brain is exhausted from uffd code)