Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754018Ab0BKNvU (ORCPT ); Thu, 11 Feb 2010 08:51:20 -0500 Received: from hera.kernel.org ([140.211.167.34]:39418 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752801Ab0BKNvT (ORCPT ); Thu, 11 Feb 2010 08:51:19 -0500 Message-ID: <4B740CFB.7060409@kernel.org> Date: Thu, 11 Feb 2010 22:58:19 +0900 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091130 SUSE/3.0.0-1.1.1 Thunderbird/3.0 MIME-Version: 1.0 To: Miklos Szeredi CC: mszeredi@suse.cz, linux-kernel@vger.kernel.org, fuse-devel@lists.sourceforge.net, polynomial-c@gentoo.org, akpm@linux-foundation.org Subject: Re: [fuse-devel] [PATCH] FUSE/CUSE: implement direct mmap support References: <4B70FBE4.7050700@kernel.org> <4B7296DF.207@kernel.org> <4B729F07.8020704@kernel.org> <4B72A802.6040009@kernel.org> <4B7344A4.1030607@kernel.org> <4B73EE68.4070004@kernel.org> <4B73FE96.2080707@kernel.org> <4B74065D.2000707@kernel.org> In-Reply-To: X-Enigmail-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Thu, 11 Feb 2010 13:51:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1649 Lines: 52 Hello, On 02/11/2010 10:40 PM, Miklos Szeredi wrote: > On Thu, 11 Feb 2010, Tejun Heo wrote: >>> So there are different offsets: >>> >>> a) vma->vm_pgoff (which may mean anything, but usually means b) >> >> Yeap, vma->vm_pgoff can be any value and doesn't really matter. The >> only visible difference would be the /proc listing, right? Setting >> this to the requested offset is trivial. > > You mean leaving it at the requested offset? Yes, that's the most > trivial thing to do. Very few drivers change vm_pgoff: > > git grep "vm_pgoff *=[^=]" Yeap, sure. I just didn't think it was visible outside. >>> b) the offset at which the pages of the mapping are located >>> c) the offset at which the server side mmap is located >> >> There are three offsets. >> >> a) the offset a client requested >> >> b) the offset into dmmap AS, a client mmap region is mapped to. This >> could be different from a) by multiple of SHMLBA / PAGE_SIZE. > > No, it could be different from a) by an arbitrary value. Then, sharing those pages would cause aliasing issues. >> c) the offset into dmmap AS, a server mmap region is mapped to, where >> collection of these mmaps define the dmmap AS. >> >> The offsets used in b) and c) are the same offsets. > > Why are they the same? I meant they point into the same space. If they're the same value, they point to the same page. Thanks. -- 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/