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Wed, 12 Nov 2025 15:36:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id tIDBF3epFGnsdQAAD6G6ig (envelope-from ); Wed, 12 Nov 2025 15:36:23 +0000 Message-ID: Date: Wed, 12 Nov 2025 16:36:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 02/16] mm: introduce leaf entry type and use to simplify leaf entry logic Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: Christian Borntraeger , Janosch Frank , Claudio Imbrenda , David Hildenbrand , 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 , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Axel Rasmussen , Yuanchu Xie , Wei Xu , Kemeng Shi , Kairui Song , Nhat Pham , Baoquan He , Chris Li , SeongJae Park , Matthew Wilcox , 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: From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 9C300140011 X-Stat-Signature: wr1xdncuf5se74f4b89mc41o5uyattsh X-Rspam-User: X-HE-Tag: 1762961785-646177 X-HE-Meta: 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 L8My4vkP zdIsSHIhqfSmRXTgVdMkG1xE84VDbI81YIaorSqlDOz5J2CVaTAqdSyApSCoECi4bM2IuPHn+pIuq6tfuaJZPdlFFJXu6/jDEqbBWN5BDnjI8trASQVVSdU5ILrovq1aWUtXUUquZ+mz4j8xzVy+54IwllsN3AAIZOl4ZZuSASlcjAer3+GnyjDiqnkBGQScr88HJa+2FwHeUS4kTY7CjXuNHgV08dSUZxR72KmGIeXy0MePvWpR2b67400VrTLBbLhxQ9hboJx3lHu++r1Zf+SpK9dgPr77Xon8p/TlWMLVGzXqBtVVTVNc0eu0TxPsK9Ma/akge3oVekXKRclgReknafAiF2acTxC/TrTpGpELn/DT/Pbw+NKdtFT0jsBX78enZ 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 11/10/25 23:21, Lorenzo Stoakes wrote: > The kernel maintains leaf page table entries which contain either: > > - Nothing ('none' entries) > - Present entries (that is stuff the hardware can navigate without fault) > - Everything else that will cause a fault which the kernel handles > > In the 'everything else' group we include swap entries, but we also include > a number of other things such as migration entries, device private entries > and marker entries. > > Unfortunately this 'everything else' group expresses everything through > a swp_entry_t type, and these entries are referred to swap entries even > though they may well not contain a... swap entry. > > This is compounded by the rather mind-boggling concept of a non-swap swap > entry (checked via non_swap_entry()) and the means by which we twist and > turn to satisfy this. > > This patch lays the foundation for reducing this confusion. > > We refer to 'everything else' as a 'software-define leaf entry' or > 'softleaf'. for short And in fact we scoop up the 'none' entries into this > concept also so we are left with: > > - Present entries. > - Softleaf entries (which may be empty). > > This allows for radical simplification across the board - one can simply > convert any leaf page table entry to a leaf entry via softleaf_from_pte(). > > If the entry is present, we return an empty leaf entry, so it is assumed > the caller is aware that they must differentiate between the two categories > of page table entries, checking for the former via pte_present(). > > As a result, we can eliminate a number of places where we would otherwise > need to use predicates to see if we can proceed with leaf page table entry > conversion and instead just go ahead and do it unconditionally. > > We do so where we can, adjusting surrounding logic as necessary to > integrate the new softleaf_t logic as far as seems reasonable at this > stage. > > We typedef swp_entry_t to softleaf_t for the time being until the > conversion can be complete, meaning everything remains compatible > regardless of which type is used. We will eventually remove swp_entry_t > when the conversion is complete. > > We introduce a new header file to keep things clear - leafops.h - this > imports swapops.h so can direct replace swapops imports without issue, and > we do so in all the files that require it. > > Additionally, add new leafops.h file to core mm maintainers entry. > > Signed-off-by: Lorenzo Stoakes Seems like a reasonable first step of the conversion. Reviewed-by: Vlastimil Babka