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 8010CC7EE43 for ; Wed, 7 Jun 2023 07:13:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238812AbjFGHNL (ORCPT ); Wed, 7 Jun 2023 03:13:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238681AbjFGHNJ (ORCPT ); Wed, 7 Jun 2023 03:13:09 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C04C11720; Wed, 7 Jun 2023 00:13:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=4CbgdtrMRU8SgCC/lj9k+w8TeWMG8R3cL1TBFp6UuqY=; b=hvjiRjbQ931WaCH5rTfNFZ43dF 7MB76TsmX5AAZsrITTyNmsY08/KqALkDgqg2ybIdFoPx+0KRcOqaGtnGD4Y4XdVJfjIXZZcxc/n2R CRxH2cDLvRo07ZSmt+1U35fV22n1a0d5zDxD4Z7SjPd02ggrx2ENbFosvjOhkq/LNWw612Ykx7Pay b8+aC4Rmb9lAjJRV7jYB25fCMsCLGRolxDysouwQz39Hjkif3EpTqgD0oud9OF2wNJGV33aSjcb9v XUZhVXcJFLYijKWVedmkYvRDC0/VuhfDmjDiE/4Dtf+7UI4Gy8scv6ROC+Hc6wl3xvZMgPLhQwXCE Z3Qsa4QA==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1q6nLa-004gCI-2l; Wed, 07 Jun 2023 07:12:46 +0000 Date: Wed, 7 Jun 2023 00:12:46 -0700 From: Christoph Hellwig To: Nitesh Shetty Cc: Christoph Hellwig , Jens Axboe , Jonathan Corbet , Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com, Keith Busch , Christoph Hellwig , Sagi Grimberg , James Smart , Chaitanya Kulkarni , Alexander Viro , Christian Brauner , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, willy@infradead.org, hare@suse.de, djwong@kernel.org, bvanassche@acm.org, ming.lei@redhat.com, dlemoal@kernel.org, nitheshshetty@gmail.com, gost.dev@samsung.com, Kanchan Joshi , Javier =?iso-8859-1?Q?Gonz=E1lez?= , Anuj Gupta , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v12 5/9] nvme: add copy offload support Message-ID: References: <20230605121732.28468-1-nj.shetty@samsung.com> <20230605121732.28468-6-nj.shetty@samsung.com> <20230606113535.rjbhe6eqlyqk4pqq@green245> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230606113535.rjbhe6eqlyqk4pqq@green245> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Jun 06, 2023 at 05:05:35PM +0530, Nitesh Shetty wrote: > Downside will be duplicating checks which are present for read, write in > block layer, device-mapper and zoned devices. > But we can do this, shouldn't be an issue. Yes. Please never overload operations, this is just causing problems everywhere, and that why I split the operations from the flag a few years ago. > The idea behind subsys is to prevent copy across different subsystem. > For example, copy across nvme subsystem and the scsi subsystem. [1] > At present, we don't support inter-namespace(copy across NVMe namespace), > but after community feedback for previous series we left scope for it. Never leave scope for something that isn't actually added. That just creates a giant maintainance nightmare. Cross-device copies are giant nightmare in general, and in the case of NVMe completely unusable as currently done in the working group. Messing up something that is entirely reasonable (local copy) for something like that is a sure way to never get this series in.