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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 06BFAC25B76 for ; Sat, 1 Jun 2024 05:59:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=qGD8e8W0ADYiRiaARL57q94CaUzxErin9PPmd+A6Ntw=; b=YuX7RPysJFFmoWGmdR+PNd95LE FuSwt6N3cmluBi5hAZTG/ZQfw17S/Lgzm6Jup4HkYfN0kFZpvzB925TXTXBUR0AlIGA3XqffcQ//L oGfGcEKPyvC18ssbZLNoDrF5llwZWPW96xfhaY5fTclftk9y5/EyDot8GXj+FS5pvQClS6SZobeLk vRffM6yMNHoFeE3bj1CfuFWmbuuae1pGl6GyMfNNSi03xM6Uzm3qHRlJ5ZO6AvblmWfFs8yHT0iPe oLY34S6l5aJiRpyGa7o9X6SJyB2kB9TiPJIKvpgst9ByOIJK/3TxU9QAKbAL8suFfEFhLPqBInFT/ W2OnoFFg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sDHmG-0000000C2Xu-0676; Sat, 01 Jun 2024 05:59:40 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sDHmB-0000000C2Wk-461g for linux-nvme@lists.infradead.org; Sat, 01 Jun 2024 05:59:37 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 06C1168D17; Sat, 1 Jun 2024 07:59:32 +0200 (CEST) Date: Sat, 1 Jun 2024 07:59:31 +0200 From: Christoph Hellwig To: Bart Van Assche Cc: Nitesh Shetty , Damien Le Moal , Jens Axboe , Jonathan Corbet , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Keith Busch , Christoph Hellwig , Sagi Grimberg , Chaitanya Kulkarni , Alexander Viro , Christian Brauner , Jan Kara , martin.petersen@oracle.com, david@fromorbit.com, hare@suse.de, damien.lemoal@opensource.wdc.com, anuj20.g@samsung.com, joshi.k@samsung.com, nitheshshetty@gmail.com, gost.dev@samsung.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, dm-devel@lists.linux.dev, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v20 02/12] Add infrastructure for copy offload in block and request layer. Message-ID: <20240601055931.GB5772@lst.de> References: <20240520102033.9361-1-nj.shetty@samsung.com> <20240520102033.9361-3-nj.shetty@samsung.com> <9f1ec1c1-e1b8-48ac-b7ff-8efb806a1bc8@kernel.org> <665850bd.050a0220.a5e6b.5b72SMTPIN_ADDED_BROKEN@mx.google.com> 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) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240531_225936_217795_78686DD6 X-CRM114-Status: GOOD ( 14.32 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Thu, May 30, 2024 at 10:11:15AM -0700, Bart Van Assche wrote: > This new approach has the following two disadvantages: > * Without plug, REQ_OP_COPY_SRC and REQ_OP_COPY_DST are not combined. These two > operation types are the only operation types for which not using a plug causes > an I/O failure. So? We can clearly document that and even fail submission with a helpful message trivially to enforce that. > * A loop is required to combine the REQ_OP_COPY_SRC and REQ_OP_COPY_DST operations. I don't see why that is a problem. Especiallly once we allow multiple sources which is really useful for GC workloads we'll need to do that anyway. > Please switch to the approach Hannes suggested, namely bio chaining. Chaining > REQ_OP_COPY_SRC and REQ_OP_COPY_DST bios before these are submitted eliminates the > two disadvantages mentioned above. No.