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b=LzKXx9vJwSlJcTzT3/alZIDwFBAL7Df+Z6kyUIdfsVhTXycAf+5iP0nEHvJkQn4RU MKg2oB0u0ClV9drOSG50ZyHACzO6Dux+tDMpo3v3mz95X+h1qdM9d492cx7gozjS3b PvGrS0E/EzYSeOC1rNKU/Pn2g2h6374GnLDw30zHAOHzb9eTYfXjAULmxbYSOxuu+a XAwBDvuETjsAUukkXkrcuNufnGwheLM/rQn9tbQQf9wHgIGnE4CzElxJaxV4mUm1W5 wMYYEJadGq+zjC+XnbIubBOgId7dbcnY92eWIgBqExkFZGbsXM2sbHWO1EykTi4/Jq MwZgZnU5A5YMw== Message-ID: <6bc50779-1daa-4d1f-9374-ef784cd6fc0d@kernel.org> Date: Tue, 25 Aug 2026 12:12:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v19 00/40] DEPT(DEPendency Tracker) To: Matthew Wilcox , NeilBrown Cc: Byungchul Park , linux-kernel@vger.kernel.org, max.byungchul.park@gmail.com, kernel_team@skhynix.com, torvalds@linux-foundation.org, linux-ide@vger.kernel.org, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, will@kernel.org, tglx@linutronix.de, rostedt@goodmis.org, joel@joelfernandes.org, sashal@kernel.org, daniel.vetter@ffwll.ch, duyuyang@gmail.com, johannes.berg@intel.com, tj@kernel.org, tytso@mit.edu, david@fromorbit.com, amir73il@gmail.com, gregkh@linuxfoundation.org, kernel-team@lge.com, linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, minchan@kernel.org, hannes@cmpxchg.org, vdavydov.dev@gmail.com, sj@kernel.org, jglisse@redhat.com, dennis@kernel.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, vbabka@suse.cz, ngupta@vflare.org, linux-block@vger.kernel.org, josef@toxicpanda.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, jlayton@kernel.org, hch@infradead.org, djwong@kernel.org, dri-devel@lists.freedesktop.org, rodrigosiqueiramelo@gmail.com, melissa.srw@gmail.com, hamohammed.sa@gmail.com, harry.yoo@oracle.com, chris.p.wilson@intel.com, gwan-gyeong.mun@intel.com, boqun.feng@gmail.com, longman@redhat.com, yunseong.kim@ericsson.com, ysk@kzalloc.com, yeoreum.yun@arm.com, netdev@vger.kernel.org, matthew.brost@intel.com, her0gyugyu@gmail.com, corbet@lwn.net, catalin.marinas@arm.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, luto@kernel.org, sumit.semwal@linaro.org, gustavo@padovan.org, christian.koenig@amd.com, andi.shyti@kernel.org, arnd@arndb.de, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mcgrof@kernel.org, petr.pavlu@suse.com, da.gomez@kernel.org, samitolvanen@google.com, paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, josh@joshtriplett.org, urezki@gmail.com, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, chuck.lever@oracle.com, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, trondmy@kernel.org, anna@kernel.org, kees@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, mark.rutland@arm.com, ada.coupriediaz@arm.com, kristina.martsenko@arm.com, wangkefeng.wang@huawei.com, broonie@kernel.org, kevin.brodsky@arm.com, dwmw@amazon.co.uk, shakeel.butt@linux.dev, ast@kernel.org, ziy@nvidia.com, yuzhao@google.com, baolin.wang@linux.alibaba.com, usamaarif642@gmail.com, joel.granados@kernel.org, richard.weiyang@gmail.com, geert+renesas@glider.be, tim.c.chen@linux.intel.com, linux@treblig.org, alexander.shishkin@linux.intel.com, lillian@star-ark.net, chenhuacai@kernel.org, francesco@valla.it, guoweikang.kernel@gmail.com, link@vivo.com, jpoimboe@kernel.org, masahiroy@kernel.org, brauner@kernel.org, thomas.weissschuh@linutronix.de, oleg@redhat.com, mjguzik@gmail.com, andrii@kernel.org, wangfushuai@baidu.com, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-i2c@vger.kernel.org, linux-arch@vger.kernel.org, linux-modules@vger.kernel.org, rcu@vger.kernel.org, linux-nfs@vger.kernel.org, linux-rt-devel@lists.linux.dev, 2407018371@qq.com, dakr@kernel.org, miguel.ojeda.sandonis@gmail.com, bagasdotme@gmail.com, wsa+renesas@sang-engineering.com, dave.hansen@intel.com, geert@linux-m68k.org, ojeda@kernel.org, alex.gaynor@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, rust-for-linux@vger.kernel.org References: <20260706061928.66713-1-byungchul@sk.com> <359ea967-9b97-4584-88e6-bddb4044de2e@kernel.org> <20260821042143.GA40890@system.software.com> <825134a8-ceae-430c-b2fc-d1d0c7240f39@kernel.org> <178730572084.2852630.7732425311008244683@noble.neil.brown.name> <3d58eb3c-7a9d-4183-907b-46172664631c@kernel.org> <178761465493.3510150.12380729360578969391@noble.neil.brown.name> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: dh8d867fyhquwiinfbnj6k17duneqfrt X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D4B48C0004 X-HE-Tag: 1787652792-232147 X-HE-Meta: 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 haDC/z5R dAtmb7mvTWARnTv6flVIeKJ7nuw5ndT+w/EgrWj/sStKkTWJvizMVjXaG+8h/HrqTe0TJL4rMPMJCWO39RmGBeli3Xtuxp9Mm5sl3c9rzwHXTRk2F73jSHa/gGCWWFAaNNUFYfYTyzMMKX43+kNkig1yW5VJNLOBimn3zctPEsOhDFrNxCAHI21YM3ePjbNtOwm73wyMWSzqitcxfghAWoYfQU9J6aYBUvuGvCSOaCfLyLOCAl6nkb0DngImYhkHx3CvS6XjgP+CAy+RyduBKYj6zRxdXS/0jo3hkpfD6uu0XZLNK4SpzNGOoV5zVPGEFGYbiaU5nUzhHK22qa2xUtELDPcdrIXwqGF5wBXweQl9qT9mVC69VxoKAPg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >>> It's interesting, that for writeback we never unlock the folio on the I/O path, >>> but instead have the dedicated page flag to tell us when writeback is complete. >> >> PG_locked and PG_writeback are two different lock-bits with two >> different meanings. >> When a folio is PG_locked the content is invalid and shouldn't be accessed. >> When a folio is in PG_writeback its data is not safe even though >> PG_dirty has been cleared (if I remember correctly). >> >> So these are two separate, though related, lock bits that would both >> need to be tracked. lockdep would detect how they are related. > > Some history ... before we had PG_writeback, we held PG_locked > throughout the writeback process. People argued convincingly that it > was fine to map a page into a process's address space (which requires > PG_locked) while it was being written back. And so PG_locked was > split. Now we take PG_locked at the beginning of the writeback process > and downgrade to PG_writeback at some point. Right, conceptually I would have thought we could do something similar on the readahead path. PG_uptodate is likely not what we want I suspect. Not that such a change would be easy, or that we should do it; just one thing that came to mind. -- Cheers, David