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Fri, 5 Apr 2024 10:55:47 +0000 Received: from DM6PR10MB4313.namprd10.prod.outlook.com ([fe80::ae68:7d51:133f:324]) by DM6PR10MB4313.namprd10.prod.outlook.com ([fe80::ae68:7d51:133f:324%4]) with mapi id 15.20.7409.042; Fri, 5 Apr 2024 10:55:47 +0000 Message-ID: <2e82a05d-f0b4-4967-a6d0-11f9282e3058@oracle.com> Date: Fri, 5 Apr 2024 11:55:41 +0100 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 00/10] block atomic writes To: Kent Overstreet , Dave Chinner Cc: Matthew Wilcox , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, jejb@linux.ibm.com, martin.petersen@oracle.com, djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, dchinner@redhat.com, jack@suse.cz, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com, linux-scsi@vger.kernel.org, ojaswin@linux.ibm.com, linux-aio@kvack.org, linux-btrfs@vger.kernel.org, io-uring@vger.kernel.org, nilay@linux.ibm.com, ritesh.list@gmail.com References: <20240326133813.3224593-1-john.g.garry@oracle.com> <62uvkga54im76lnz47nc2znoeayidp2tcwpffseqtl42xdwxlc@hep6ckbgpwqz> Content-Language: en-US From: John Garry Organization: Oracle Corporation In-Reply-To: <62uvkga54im76lnz47nc2znoeayidp2tcwpffseqtl42xdwxlc@hep6ckbgpwqz> Content-Type: text/plain; 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I've talked to a few database people >>> and all they want is to increase the untorn write boundary from "one >>> disc block" to one database block, typically 8kB or 16kB. >>> >>> So they would be quite happy with a much simpler interface where they >>> set the inode block size at inode creation time, and then all writes to >>> that inode were guaranteed to be untorn. This would also be simpler to >>> implement for buffered writes. >> You're conflating filesystem functionality that applications will use >> with hardware and block-layer enablement that filesystems and >> filesystem utilities need to configure the filesystem in ways that >> allow users to make use of atomic write capability of the hardware. >> >> The block layer functionality needs to export everything that the >> hardware can do and filesystems will make use of. The actual >> application usage and setup of atomic writes at the filesystem/page >> cache layer is a separate problem. i.e. The block layer interfaces >> need only support direct IO and expose limits for issuing atomic >> direct IO, and nothing more. All the more complex stuff to make it >> "easy to use" is filesystem level functionality and completely >> outside the scope of this patchset.... > A CoW filesystem can implement atomic writes without any block device > support. It seems to me that might have been the easier place to start - > start by getting the APIs right, then do all the plumbing for efficient > untorn writes on non CoW filesystems... 03/10 and 04/10 in this series define the user API, i.e. RWF_ATOMIC and statx updates. Any filesystem-specific changes - like in https://lore.kernel.org/linux-xfs/20240304130428.13026-1-john.g.garry@oracle.com/ - are just for enabling this API for that filesystem.