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Mon, 16 Feb 2026 11:39:06 +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 hj/sAtoBk2nxfgAAD6G6ig (envelope-from ); Mon, 16 Feb 2026 11:39:06 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id D646FA0AA5; Mon, 16 Feb 2026 12:38:59 +0100 (CET) Date: Mon, 16 Feb 2026 12:38:59 +0100 From: Jan Kara To: Ojaswin Mujoo Cc: Pankaj Raghav , linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, lsf-pc@lists.linux-foundation.org, Andres Freund , djwong@kernel.org, john.g.garry@oracle.com, willy@infradead.org, hch@lst.de, ritesh.list@gmail.com, jack@suse.cz, Luis Chamberlain , dchinner@redhat.com, Javier Gonzalez , gost.dev@samsung.com, tytso@mit.edu, p.raghav@samsung.com, vi.shah@samsung.com Subject: Re: [Lsf-pc] [LSF/MM/BPF TOPIC] Buffered atomic writes Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 1B54C4000B X-Stat-Signature: cekhjrh1zuoqhfn375usjwbt5hy9ma5i X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1771241947-291121 X-HE-Meta: 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 FXyLXyRv ilguWrq0jd2hFLl81/sVgf/yi2KzU/s9MQKmroipK9xQwf7q6DfWGD8h2/8R+nor9wklMT7q+ggIdRoZ0ZsdOsEnVcK3b/PCiUECYJj4nOJGJcwkWwNwarp3imC1eSHC/2zkYK8boDK/McLFWI9BsRdhyFbLsDPciPBofxDZbyd/GeNm4gS2kecpfdAsO//RYhCOq9P+8zMCkmdIA2sjIivAe5fwmj3/uBMAwcgWxTX6YQUR+tyO22Niv1IaqOixT7063Bqqh/msQGLHTbPi65X/Bh3FIXWbIbdqdaiAUTdvmNViHELu07jPFgxSxDIShun05dqvuKI7j8Qkd/BA60tv70q2A3vB2aGnhMBlRhMa5Yk3TFZN8VtBl9pfM1GyjB0A0qmw2r67ICy5m8HpNLu5xSlbYplXRMcj0 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: Hi! On Fri 13-02-26 19:02:39, Ojaswin Mujoo wrote: > Another thing that came up is to consider using write through semantics > for buffered atomic writes, where we are able to transition page to > writeback state immediately after the write and avoid any other users to > modify the data till writeback completes. This might affect performance > since we won't be able to batch similar atomic IOs but maybe > applications like postgres would not mind this too much. If we go with > this approach, we will be able to avoid worrying too much about other > users changing atomic data underneath us. > > An argument against this however is that it is user's responsibility to > not do non atomic IO over an atomic range and this shall be considered a > userspace usage error. This is similar to how there are ways users can > tear a dio if they perform overlapping writes. [1]. Yes, I was wondering whether the write-through semantics would make sense as well. Intuitively it should make things simpler because you could practially reuse the atomic DIO write path. Only that you'd first copy data into the page cache and issue dio write from those folios. No need for special tracking of which folios actually belong together in atomic write, no need for cluttering standard folio writeback path, in case atomic write cannot happen (e.g. because you cannot allocate appropriately aligned blocks) you get the error back rightaway, ... Of course this all depends on whether such semantics would be actually useful for users such as PostgreSQL. Honza -- Jan Kara SUSE Labs, CR