Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756488AbYH1SIu (ORCPT ); Thu, 28 Aug 2008 14:08:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751725AbYH1SIm (ORCPT ); Thu, 28 Aug 2008 14:08:42 -0400 Received: from hera.kernel.org ([140.211.167.34]:56914 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751250AbYH1SIl (ORCPT ); Thu, 28 Aug 2008 14:08:41 -0400 Message-ID: <48B6E844.3050508@kernel.org> Date: Thu, 28 Aug 2008 20:02:44 +0200 From: Tejun Heo User-Agent: Thunderbird 2.0.0.12 (X11/20071114) MIME-Version: 1.0 To: Greg KH CC: fuse-devel@lists.sourceforge.net, miklos@szeredi.hu, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/7] FUSE: implement ioctl support References: <1219945263-21074-1-git-send-email-tj@kernel.org> <1219945263-21074-6-git-send-email-tj@kernel.org> <20080828175116.GB18461@kroah.com> <48B6E79E.6020702@kernel.org> In-Reply-To: <48B6E79E.6020702@kernel.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Thu, 28 Aug 2008 18:08:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 943 Lines: 23 Tejun Heo wrote: > Greg KH wrote: >> Why do we need ioctls? For CUSE? In that case, would we need to copy >> the memory from userspace, into the kernel, and then back out into >> userspace again? Can't we just have a "pass-through" type fixed ioctl >> instead? > > Can you elaborate a bit? How the fixed ioctl would know how much to > copy in and out and from where? If you're worried about the double copying due to performance reasons, what we can do is implementing userspace to userspace copying. I just took easier path of copying twice as u-u copy can't be done using the existing FUSE mechanics, but frankly, at this point, I think that would be an premature optimization. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/