From mboxrd@z Thu Jan 1 00:00:00 1970 From: hooanon05@yahoo.co.jp Subject: Re: [fuse-devel] delta filesystem prototype Date: Thu, 05 Mar 2009 01:23:44 +0900 Message-ID: <26175.1236183824@jrobl> References: <9884.1236069117@jrobl> <87r61ec1o7.fsf@frosties.localdomain> <7200.1236085884@jrobl> <1236094078.6988.3.camel@norville.austin.ibm.com> <19642.1236095410@jrobl> <1236095699.6988.6.camel@norville.austin.ibm.com> <19966.1236096162@jrobl> <1236096857.6988.28.camel@norville.austin.ibm.com> <20279.1236097152@jrobl> <1236098800.6988.82.camel@norville.austin.ibm.com> <21460.1236100412@jrobl> <8763ip5wuk.fsf@frosties.localdomain> <1236175801.29098.3.camel@norville.austin.ibm.com> Cc: Goswin von Brederlow , Miklos Szeredi , linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net To: Dave Kleikamp Return-path: Received: from vsmtp02.dti.ne.jp ([202.216.231.137]:40315 "EHLO vsmtp02.dti.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752214AbZCDQYN (ORCPT ); Wed, 4 Mar 2009 11:24:13 -0500 In-Reply-To: <1236175801.29098.3.camel@norville.austin.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Dave Kleikamp: > On Wed, 2009-03-04 at 12:52 +0100, Goswin von Brederlow wrote: ::: > > By the way. If you mmap a file in fuse shared twice wouldn't the > > kernel share the physical pages. So the first access calls fuse and > > loads the data into memory, the second access would just get the same > > physical page mapped. Right? > > Right. Some of my comments were a result of not being clear on what J. > R. meant when he asked about the first mapping being to the lower file. > Both mmaps to the same file in fuse would access the same physical > pages. I didn't know how fuse implements mmap and sharing pages. Additionally there is no mmap code in deltafs.c. So I wrote "it is unclear how do you implment mmap". Now I am reading fuse (instead of deltafs.c) and begin understanding that fuse and deltafs work as you expected. But the implementation seems different a little to me. These two mappings are not sharing memory pages but keeping the latest contents by re-reading, do they? J. R. Okajima