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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vJDCh-000000068nw-2KVV; Wed, 12 Nov 2025 15:56:15 +0000 Date: Wed, 12 Nov 2025 15:56:15 +0000 From: Matthew Wilcox To: Ojaswin Mujoo Cc: Christian Brauner , djwong@kernel.org, ritesh.list@gmail.com, john.g.garry@oracle.com, tytso@mit.edu, dchinner@redhat.com, hch@lst.de, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, jack@suse.cz, nilay@linux.ibm.com, martin.petersen@oracle.com, rostedt@goodmis.org, axboe@kernel.dk, linux-block@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [RFC PATCH 2/8] mm: Add PG_atomic Message-ID: References: <5f0a7c62a3c787f2011ada10abe3826a94f99e17.1762945505.git.ojaswin@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5f0a7c62a3c787f2011ada10abe3826a94f99e17.1762945505.git.ojaswin@linux.ibm.com> X-Stat-Signature: ahsj1mnx46k43y5s413uf3roawoyczim X-Rspam-User: X-Rspamd-Queue-Id: 8D27B40005 X-Rspamd-Server: rspam10 X-HE-Tag: 1762962990-811539 X-HE-Meta: U2FsdGVkX1/fQWF4u9Krz04tW0LLb1b5P95jV+AWnHdBv/svZhkub8U2cO5kI2ylx48MFwbYjTKYd69y3IGvsniliZ5MayV16x7W1MgmTAzK61XKb2x1HLScXSv/i4HYEsnwBWdeETnf/H/8DUr9DA/xiZqZR2qviShHo74sqfCBtY2QoF7+GWwc0dCLqdYXuAd65rerWZfGzUGS4E2hL67VvKmd8kXrMFNZO+/cT1Es/RgNiFs7bfEeWf7G1grkB1ZyzZdGm5gW6qPMphxV3TMfdZLbXupJ0sFYiFavXg5dSL7jwEylFSm+vzrGSFTgwHfr2aWaHqw4BAdJsa53otHq50XjUtsuHvZZ8PU1wwGGUCkiwwAIzuP+fnfkdniKdVBUYrnBezzOyfTKf9gutyQuFjT6zMWfsGUnCTZlq2EHoSehFm6Ub36LPccwLivsYXTjfNCd2ntuTq9uJxdXTScZYcqLeG/pKJXvxyFCBwMNJtM4XwRv8H7TqCOinyAPDwwUR6SCx9B1w0ER5Lab/gy1elDHaSRUSJvj0vbJfTcH2lmaO6jnEiXu48Xd+uEAibjLtTLyrqeMfDdAy/DjGmegMJEUNGAGtLUgdTwyslKcc0QLa2XoXN4DPJqwkufgtpFko30cgFh1K7FbIibjWISUT+n+d2tcQ3nh4gCowrFLKuWA3RLshMccL1p1iVNljFPGzQuA6Nfvqrn4WKkY7kMA9+Wo3Xc6LTiJyHeFZU57hKB2x2+xIGQCc7tAJHtiGSebMoxSKAvOiY2+xSHDw5hB76XlN1zYQQl8kUUiAM+PzBABoo8UMysDkZ2l3qh60L1yjnq0LDcNADeGsQj0YZZRgq/y67hQluWhuzt7gOcGzn59IqCgNI0VgDbFb5RnFBNeUNERkkNqgaYGopk/Oq67tcFwymM9N3ZjugTXKeFe0MDxqCWmB+nQ7PkQY+OwlqEQz5pxCvA1MeratNb nF7j4wuT IGFbS4RFFBNGy8YXDZFfX20Hi1AT8oG5baof0t4iK+RQFU1EM9MTRtScb1aqccQKzFKRsQsDKTn9dbXAIjcknMb0p6kxklAgprylhV6BEyvrIl7Tn4kS2U/xZ2OQ7xBOqm+AJF8fqB1YElsIfH2TvIGvh2yCH0n3Z0ojOFP3ZXlBabyZITvMWAsZ7ZAkjZ6gtmP/Vn3usA+NhS9FaH1D8bZDs/ZUdn9TXf15taZ4kV3Cy8yw8Ez8ErhFgy/wC5f6/h9v4ksh6jge2z/VW9RAYXlQNWuhN+C6K7LGGgXPs5om0gcfK+KRr5GYhEb0HxRiVFRS9i79OFnfJA/Y4w5oy4B6H8DghtJ9TwObGwIeE1niic3Ljw3xOafCBkH6D6o7U74q3MGzTMLqMMhM= 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 Wed, Nov 12, 2025 at 04:36:05PM +0530, Ojaswin Mujoo wrote: > From: John Garry > > Add page flag PG_atomic, meaning that a folio needs to be written back > atomically. This will be used by for handling RWF_ATOMIC buffered IO > in upcoming patches. Page flags are a precious resource. I'm not thrilled about allocating one to this rather niche usecase. Wouldn't this be more aptly a flag on the address_space rather than the folio? ie if we're doing this kind of write to a file, aren't most/all of the writes to the file going to be atomic?