From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E1DCB2451C0; Wed, 11 Dec 2024 04:08:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733890087; cv=none; b=L1/NqGQKSMy/78FkaHsltz3Thphs/0rH9Hg1yivfmzMzCqV6OGuDhu1WroUmFwHBRFyQNJ1heV/UXdQlGBN7wN6Gb8F5pTGJzWJ2UhY6mWmEcGOqC8TuanmdAKW0XztDnSQksr0bMkbFJF/3VqbKau2tOL1XLpRnqjk6tmEudCU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733890087; c=relaxed/simple; bh=7/3hmNoQ4LWXf/liq0trPhtYhdVp9Bh0JJE/pGvZqI0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XkXdcnpFFnQ9gkxJDKhM1i6wbD+LpTshddOyY61G6CaZ4hqk3ThkB3lzCnilR3uAb4yq6pQ8wDQ2WHPRVCRT6mXrrUnDtk7A6Q5z3oe7HEQfjRjttbQieoGHAGjW27XkeiE9C6V8O/fkjcCkXDfCFNJ052RH4dYQsKJ+1wUDBJk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m/UfDmLE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="m/UfDmLE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 373A1C4CED2; Wed, 11 Dec 2024 04:08:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733890086; bh=7/3hmNoQ4LWXf/liq0trPhtYhdVp9Bh0JJE/pGvZqI0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=m/UfDmLE/Egvp+aU2S6OtaAiPyALgOouiw8E+uIWgCmIcPR4C2wjS73sbWaCLIIRt gWn+RRFTfqC4ombZ1LaTAOmlr/qYUJepIDpqF1zfy3lkHpnd0LFqNKnpsIdlwoNV1q torokdsotdOIaYmZoXSRFVu40kfdYFGDnY4JzzhDcn517OIX8RyHltAn5FUn2dgJh0 90Ev9VNXFa6tQ/jVAAgQ42wn9SV0Bz8UhMHM51OIXl55ihfMyWYmRPVVpfr5MsQpQp XtdWAqu4dNI6qKMz3dGzSWvaISGjEYAGwulQJRy4k64T+fzqLVloAEjgQP4OdvMwNj KSOqYl/OYF4LQ== Message-ID: <6ff84297-d133-48d4-b847-807a75cab0f6@kernel.org> Date: Wed, 11 Dec 2024 13:07:38 +0900 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv10 0/9] write hints with nvme fdp, scsi streams To: Bart Van Assche , hch , Johannes Thumshirn Cc: "Martin K. Petersen" , Nitesh Shetty , Javier Gonzalez , Matthew Wilcox , Keith Busch , Keith Busch , "linux-block@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-scsi@vger.kernel.org" , "io-uring@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "joshi.k@samsung.com" References: <9d61a62f-6d95-4588-bcd8-de4433a9c1bb@acm.org> <8ef1ec5b-4b39-46db-a4ed-abf88cbba2cd@acm.org> <20241205080342.7gccjmyqydt2hb7z@ubuntu> <20241210071253.GA19956@lst.de> <2a272dbe-a90a-4531-b6a2-ee7c4c536233@wdc.com> <20241210105822.GA3123@lst.de> From: Damien Le Moal Content-Language: en-US Organization: Western Digital Research In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 12/11/24 4:21 AM, Bart Van Assche wrote: > On 12/10/24 2:58 AM, hch wrote: >> On Tue, Dec 10, 2024 at 08:05:31AM +0000, Johannes Thumshirn wrote: >>>> Generally agreeing with all you said, but do we actually have any >>>> serious use case for cross-LU copies?  They just seem incredibly >>>> complex any not all that useful. >>> >>> One use case I can think of is (again) btrfs balance (GC, convert, etc) >>> on a multi drive filesystem. BUT this use case is something that can >>> just use the fallback read-write path as it is doing now. >> >> Who uses multi-device file systems on multiple LUs of the same SCSI >> target ơr multiple namespaces on the same nvme subsystem? > > On Android systems F2FS combines a small conventional logical unit and a > large zoned logical unit into a single filesystem. This use case will > benefit from copy offloading between different logical units on the same > SCSI device. While there may be disagreement about how desirable this > setup is from a technical point of view, there is a real use case today > for offloading data copying between different logical units. But for F2FS, the conventional unit is used for metadata and the other zoned LU for data. How come copying from one to the other can be useful ? > > Bart. > -- Damien Le Moal Western Digital Research