From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 009.lax.mailroute.net (009.lax.mailroute.net [199.89.1.12]) (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 976BE23ED63; Tue, 10 Dec 2024 19:21:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.1.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733858497; cv=none; b=s97EW7qXxH2GUyl80A7nsFlwY2jgIjxFzZ8ccovBjS0TsCeOw3o9WpVElEpvf6QXYuBIsRNtsiL98uh9f2LC7xKQGjmiJVxPvUWnEezIvLVjZODuEo3SuSpLJVhqtM+DpOJyRVRrfL9RiCOAB++w1SIkk1C1Yd5uipi4PX6nV4A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733858497; c=relaxed/simple; bh=3IuxfdZlkeKKdy0z0s/LC0FJPtMGyWmWmj3MdGBivHQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=syE+4FP6t588ImF4/YcY5SQZS94HhcemK+n1OIDLJFiPXv4SmtAbEQJzMBvN30mInR4iI3mzsuJ5Utb28h363K8Az8TrfnLcdjiuEOQyKsvF5FukOpEzh5LrwRVJ8YtiHZgVPo7lf3QwKTN0NyP6b6RVE1hACKUvG4iUjnFYpMw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org; spf=pass smtp.mailfrom=acm.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b=H8w++Jtt; arc=none smtp.client-ip=199.89.1.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=acm.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b="H8w++Jtt" Received: from localhost (localhost [127.0.0.1]) by 009.lax.mailroute.net (Postfix) with ESMTP id 4Y77rT0hT9zlfl5W; Tue, 10 Dec 2024 19:21:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=acm.org; h= content-transfer-encoding:content-type:content-type:in-reply-to :from:from:content-language:references:subject:subject :user-agent:mime-version:date:date:message-id:received:received; s=mr01; t=1733858483; x=1736450484; bh=kGRxI4MvkczRgURGuKE/NkzS kR8ERW6zUvwscihee5Y=; b=H8w++JttLWyRmupBTpStBzQYxt04HXVU8MKEQp/A QDh5jwvvB7s/UP9el/mzXENVIjN+SNQL050OLkUB5F4NIzwf7R6EUjlXHqRPlKov 1u51rm2LezO45wdEDr6Uid0qCWKiscKLy5sfj5krUU0B9bTVdq9P6jO0WzAjshJ8 0vnnMakugglrPj/CaTcLAVyWNSFkva6ccpFCmNr+hFUfHByiRhjCwfWjBss37wjc +Qb2yUvJDvJvNGJsIGh/Avom64luqQdXa/qRFoRiehYjX0xMZaZfTmgJFP16eCI+ 93n+QYDTSoYErgf2t0pn9JC36n/iVCi5CnmzCkklf/KarA== X-Virus-Scanned: by MailRoute Received: from 009.lax.mailroute.net ([127.0.0.1]) by localhost (009.lax [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id v14CjmZSqQuW; Tue, 10 Dec 2024 19:21:23 +0000 (UTC) Received: from [100.66.154.22] (unknown [104.135.204.82]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bvanassche@acm.org) by 009.lax.mailroute.net (Postfix) with ESMTPSA id 4Y77rJ3qwkzlgd6J; Tue, 10 Dec 2024 19:21:20 +0000 (UTC) Message-ID: Date: Tue, 10 Dec 2024 11:21:19 -0800 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: 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> Content-Language: en-US From: Bart Van Assche In-Reply-To: <20241210105822.GA3123@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable 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. >=20 > Who uses multi-device file systems on multiple LUs of the same SCSI > target =C6=A1r 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. Bart.