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 13128CF6AB9 for ; Thu, 8 Jan 2026 10:17:26 +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=mf5Fl5TyeSzTLU/3MWJhqzju+t39rckia/cTJh/0f8I=; b=x+JSPhQ3buS98xKciD2mBFmc90 CwHu49Wsy5iToP4kNS6cH1Q3RsIhe28xdN/r6I9RoWV3Ulny9NUb9QpWbt1SN9K1JWK/xlxf5+w+V ViCs/nkXP2yQh0rE5aZNlB18IjIXP80EhiEfNjLTqs//ni09RWTW+dbcvl3FA/nwBChVlVTYes2my oRakuGE7IQAXE3MgVfO4FR8zbnJs/lBQujK43S+3j8KABgZSTR6iVCGs9+LbRewe9R4epytgR4dZi IckZWEjMU6DoJOuBTi9EpWMopYafcKNJyHH9Q96HKoDCeEZmRNbsoDuiTmzvkhOUyLdUfaRkj6GZi brCA/IDQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vdn4y-0000000Gaez-32ut; Thu, 08 Jan 2026 10:17:20 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vdn4s-0000000GadS-05bQ for linux-nvme@lists.infradead.org; Thu, 08 Jan 2026 10:17:15 +0000 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> 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-20260108_021714_197028_61F2B639 X-CRM114-Status: GOOD ( 18.88 ) 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, 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.