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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pmaKv-006tS5-Kq; Wed, 12 Apr 2023 13:16:33 +0000 Date: Wed, 12 Apr 2023 14:16:33 +0100 From: Matthew Wilcox To: Hannes Reinecke Cc: "lsf-pc@lists.linux-foundation.org" , "linux-fsdevel@vger.kernel.org" , linux-mm@kvack.org, "linux-block@vger.kernel.org" Subject: Re: [LSF/MM/BPF TOPIC] Sunsetting buffer_heads Message-ID: References: <6ca617db-5370-7f06-8b4e-c9e10f2fa567@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6ca617db-5370-7f06-8b4e-c9e10f2fa567@suse.de> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4F3D44001C X-Stat-Signature: 9gyd6drrehoowa86unt8kxmcaqs46ig4 X-Rspam-User: X-HE-Tag: 1681305400-645545 X-HE-Meta: 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 cpfK2xNw pysLmatKhUrOXeBMDvrRlkmOrjZTRIfa+b0BHQCrwzy0TaXgKiQVSANcNvAUPZXVVrC3qYnjRw043ov4FFd2wPKBp+7ZDDvnD4fgGoUYIb6YiBoURjhfyXwFn831hXg8cHiwSimbg6hjd9D/wDF14FLaNkJqfmgihKNTAHWYcgxB4hlUWkGCP6XrvBiCut+lDgv970X/FWNnqpkSmLpiTyzhGlBFoBvl6EolUF6rCZXkmzOV7loGY6GnaIM+MD48Dvam4r9ht4QT1Pn6x3GOLwUAF+yyJEdKPzSLouLLUGWAZg3s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000287, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Apr 12, 2023 at 12:18:29PM +0200, Hannes Reinecke wrote: > Ceterum censeo ... > > Having looked at implementing large blocksizes I constantly get bogged down > by buffer_heads and being as they are intricately linked into filesystems > and mm. > > And also everyone seems to have agreed to phase out buffer_heads eventually. > > So maybe it's time to start discussing exactly _how_ this could be done. > And LSF/MM seems to be the idea location for it. > > So far I've came across the following issues: > > - reading superblocks / bread(): maybe convert to ->read_folio() ? > - bh_lru and friends (maybe pointless once bread() has been converted) > - How to handle legacy filesystems still running on buffer_heads > > I'm sure this is an incomplete list, and I'm equally sure that several > people have their own ideas what should or need to be done. > > So this BOF will be about collecting these ideas and coming up with a design > how we can deprecated buffer_heads. Might be worth reviewing this thread: https://lore.kernel.org/linux-fsdevel/20230129044645.3cb2ayyxwxvxzhah@garbanzo/