From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 CD25E111A1; Sat, 1 Jun 2024 05:59:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717221579; cv=none; b=rwl74DGLnA1gSo//MaOryVQ6AbpFiJgtS3NMLDjYPcZfYt+j7HNEaEfUn1nFchWYVpdA1TNDMQs5TOWfaY03y3NU+7W9iNnfkyyDJBK/G5hi/RtB52rseub7DI+PmhcWbyHpFRah1Wgvgd9IR43taEke8n46/Xy80wDDensiK4Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717221579; c=relaxed/simple; bh=icMOdDMIgwIXGGzLIxIeSihpdWV/icJnEheY/OC4ask=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IrdRsNfYo6vFW0UXEoaM4k1LKYF4IlzJFUCDTrQ1DIspcOq4/Hm9aFeRiXvDliBwS1DQOCAA1hROe9qJ8EesqoOnZK+Z2rOkpxUQuseUCKrl3BmVqBWB97ztJV9Is6tjJlaM4qgCbzsq54XBoVMUpU3QmoukJhNibjZHnOjwop8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de 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> Precedence: bulk X-Mailing-List: linux-kernel@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, 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.