Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755574Ab0BJMPj (ORCPT ); Wed, 10 Feb 2010 07:15:39 -0500 Received: from fxip-0047f.externet.hu ([88.209.222.127]:41155 "EHLO pomaz-ex.szeredi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755273Ab0BJMPi (ORCPT ); Wed, 10 Feb 2010 07:15:38 -0500 To: Tejun Heo CC: miklos@szeredi.hu, mszeredi@suse.cz, linux-kernel@vger.kernel.org, fuse-devel@lists.sourceforge.net, polynomial-c@gentoo.org, akpm@linux-foundation.org In-reply-to: <4B729F07.8020704@kernel.org> (message from Tejun Heo on Wed, 10 Feb 2010 20:56:55 +0900) Subject: Re: [fuse-devel] [PATCH] FUSE/CUSE: implement direct mmap support References: <4B70FBE4.7050700@kernel.org> <4B7296DF.207@kernel.org> <4B729F07.8020704@kernel.org> Message-Id: From: Miklos Szeredi Date: Wed, 10 Feb 2010 13:15:28 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1303 Lines: 33 On Wed, 10 Feb 2010, Tejun Heo wrote: > > Okay, lets be a little clearer. There are client side maps and server > > side maps. Client side maps are naturally aligned (same offset -> > > same page). > > Same offset -> same page doesn't hold. Right, I really meant same page -> same offset. If the same offset is mapped to multiple pages: no problem. If the same page is mapped to multiple offsets, then obviously it's not going to work properly. > Can you please elaborate how you think the thing can work without > referencing the proposed implementation? Let's find out where the > misundertanding is. Thinking about it I'm not really sure... Maybe the problem is that the propsed solution allows too much freedom. Normally there's a 1:1 relationship between pages and offsets. But we want to break that for CUSE, because two different mappings of a char dev might point to completely different pages, right? When does that happen? Can it happen that two mappings of the same file descriptor will have different backing pages? Thanks, Miklos -- 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/