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 7BA1139E6E3; Thu, 8 Jan 2026 10:17:11 +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=1767867439; cv=none; b=EjFYsVWgmLzeH6KmJN9Htjr3vwnSCRkMa3KW0OCanSNIWWRGn6PfrEsZy1OiohfWqjwRJSW5Om8xzNxQFyj+GFSZz7mibuswPxilW0doCM6NjUYmn+VGZrRMrWT3Ycef0v9J6TUh4Tcjh62msZHnxMEFyIHnBpsTkvHrHvShxRM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767867439; c=relaxed/simple; bh=ODGdH7RlSR+dio8YcadH4b5hAYSaRoEE5ObchUQmYbM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ry+Vcbfw2VmEjeU6qx0baHYoHbB0bsqLuK82kJQvZgDpIprwZUjuhl3zwcLlpZfVwPW6jWrUBwDJhLP7oEtC7yCRPreJjHQDCNFDuiceK72FEF7muE0XAncTIZGZoWLj/DexOU0GcJJIs2/OsKcQUSA4/p79DXhTSv7XVx+et2U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (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=pass (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 E3BE3227A87; Thu, 8 Jan 2026 11:17:03 +0100 (CET) Date: Thu, 8 Jan 2026 11:17:03 +0100 From: Christoph Hellwig To: Ming Lei Cc: Christoph Hellwig , Christian =?iso-8859-1?Q?K=F6nig?= , Pavel Begunkov , linux-block@vger.kernel.org, io-uring@vger.kernel.org, Vishal Verma , tushar.gohad@intel.com, Keith Busch , Jens Axboe , Sagi Grimberg , Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org Subject: Re: [RFC v2 01/11] file: add callback for pre-mapping dmabuf Message-ID: <20260108101703.GA24709@lst.de> References: <74d689540fa200fe37f1a930165357a92fe9e68c.1763725387.git.asml.silence@gmail.com> <7b2017f4-02a3-482a-a173-bb16b895c0cb@amd.com> <20251204110709.GA22971@lst.de> <0571ca61-7b17-4167-83eb-4269bd0459fe@amd.com> <20251204131025.GA26860@lst.de> <754b4cc9-20ab-4d87-85bf-eb56be058856@amd.com> <20260107160151.GA21887@lst.de> Precedence: bulk X-Mailing-List: io-uring@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, Jan 08, 2026 at 10:19:18AM +0800, Ming Lei wrote: > > The feature is in no way nvme specific. nvme is just the initial > > underlying driver. It makes total sense to support this for any high > > performance block device, and to pass it through file systems. > > But why does FS care the dma buffer attachment? Since high performance > host controller is exactly the dma buffer attachment point. I can't parse what you're trying to say here. > If the callback is added in `struct file_operations` for wiring dma buffer > and the importer(host contrller), you will see it is hard to let it cross device > mapper/raid or other stackable block devices. Why? But even when not stacking, the registration still needs to go through the file system even for a single device, never mind multiple controlled by the file system.