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[71.191.145.202]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-91f23d452b0sm12300596d6.11.2026.11.12.21.08.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Nov 2026 21:08:27 -0800 (PST) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [PATCH 05/12] fs/proc/task_mmu: write-protect device-private THPs in PAGEMAP_SCAN From: "Gregory Price (Meta)" To: "Lorenzo Stoakes (ARM)" Cc: Tal Zussman , Andrew Morton , Mike Rapoport , Peter Xu , James Houghton , Andrea Arcangeli , Suren Baghdasaryan , Balbir Singh , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , =?utf-8?q?Micha=C5=82_Miros=C5=82aw?= , Andrei Vagin , Stephen Rothwell , Arnd Bergmann , Muhammad Usama Anjum , David Hildenbrand , Zi Yan , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Chris Down , Muchun Song , Oscar Salvador , =?utf-8?q?Miko=C5=82aj_Lenczewski?= , Michal Hocko , Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org In-Reply-To: References: <20261111-uffd-state-fixes-v1-0-00713d368976@columbia.edu> <20261111-uffd-state-fixes-v1-5-00713d368976@columbia.edu> Date: Fri, 13 Nov 2026 00:08:26 -0500 Message-Id: <179454650651.482102.17667443707760097412.b4-reply@b4> X-Mailer: b4 0.17-dev On 2026-11-12 19:34 +0000, Lorenzo Stoakes (ARM) wrote: > On Wed, Nov 11, 2026 at 12:55:13PM -0500, Tal Zussman wrote: > > but does nothing for a device-private THP. The PMD never gets the uffd > > bit. > > Sigh yeah. Device-private feels like another 'just have to happen to know to > update X million open-coded parts of the code'. > > We really need to find a way to abstract this stuff. > I've poked at it a bit, but zone device creates this issue in many places. The core issue is really that softleaf can mean 20 things, and the number of things has been piled on heavily. I don't know how we solve this, it's just a rats nest of complexity at this point. -- ~Gregory