From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27434208AA; Thu, 9 Nov 2023 15:46:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 957EF4EF2; Thu, 9 Nov 2023 07:46:26 -0800 (PST) Received: by verein.lst.de (Postfix, from userid 2407) id EB3BF68AA6; Thu, 9 Nov 2023 16:46:19 +0100 (CET) Date: Thu, 9 Nov 2023 16:46:19 +0100 From: Christoph Hellwig To: Matthew Wilcox Cc: Christoph Hellwig , John Garry , axboe@kernel.dk, kbusch@kernel.org, sagi@grimberg.me, jejb@linux.ibm.com, martin.petersen@oracle.com, djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, chandan.babu@oracle.com, dchinner@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com, linux-api@vger.kernel.org, Alan Adamson Subject: Re: [PATCH 21/21] nvme: Support atomic writes Message-ID: <20231109154619.GA3491@lst.de> References: <20230929102726.2985188-1-john.g.garry@oracle.com> <20230929102726.2985188-22-john.g.garry@oracle.com> <20231109153603.GA2188@lst.de> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) On Thu, Nov 09, 2023 at 03:42:40PM +0000, Matthew Wilcox wrote: > That wasn't the model we had in mind. In our thinking, it was fine to > send a write that crossed the atomic write limit, but the drive wouldn't > guarantee that it was atomic except at the atomic write boundary. > Eg with an AWUN of 16kB, you could send five 16kB writes, combine them > into a single 80kB write, and if the power failed midway through, the > drive would guarantee that it had written 0, 16kB, 32kB, 48kB, 64kB or > all 80kB. Not necessarily in order; it might have written bytes 16-32kB, > 64-80kB and not the other three. I can see some use for that, but I'm really worried that debugging problems in the I/O merging and splitting will be absolute hell.