From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E004C4167D for ; Thu, 9 Nov 2023 16:03:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234513AbjKIQDz (ORCPT ); Thu, 9 Nov 2023 11:03:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234728AbjKIPsq (ORCPT ); Thu, 9 Nov 2023 10:48:46 -0500 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> 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) Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org 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.