Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754697AbXICG7R (ORCPT ); Mon, 3 Sep 2007 02:59:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751616AbXICG7G (ORCPT ); Mon, 3 Sep 2007 02:59:06 -0400 Received: from sovereign.computergmbh.de ([85.214.69.204]:51270 "EHLO sovereign.computergmbh.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751363AbXICG7E (ORCPT ); Mon, 3 Sep 2007 02:59:04 -0400 Date: Mon, 3 Sep 2007 08:59:02 +0200 (CEST) From: Jan Engelhardt To: "Josef 'Jeff' Sipek" cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, hch@infradead.org, viro@ftp.linux.org.uk, bharata@linux.vnet.ibm.com, j.blunck@tu-harburg.de, Erez Zadok Subject: Re: [PATCH 12/32] Unionfs: documentation updates In-Reply-To: <1188786057364-git-send-email-jsipek@cs.sunysb.edu> Message-ID: References: <1188786055371-git-send-email-jsipek@cs.sunysb.edu> <1188786057364-git-send-email-jsipek@cs.sunysb.edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1680 Lines: 44 On Sep 2 2007 22:20, Josef 'Jeff' Sipek wrote: >+ >+While rebuilding Unionfs's objects, we also purge any page mappings and >+truncate inode pages (see fs/Unionfs/dentry.c:purge_inode_data). This is to fs/unionfs/dentry.c >+Unionfs maintains the following important invariant regarding mtime's, >+ctime's, and atime's: the upper inode object's times are the max() of all of utimes, ctimes and atimes. >+2. Lockdep (a debugging feature) isn't aware of stacking, and so it >+ incorrectly complains about locking problems. The problem boils down to >+ this: Lockdep considers all objects of a certain type to be in the same >+ class, for example, all inodes. Lockdep doesn't like to see a lock held >+ on two inodes within the same task, and warns that it could lead to a >+ deadlock. However, stackable file systems do precisely that: they lock >+ an upper object, and then a lower object, in a strict order to avoid >+ locking problems; in addition, Unionfs, as a fan-out file system, may >+ have to lock several lower inodes. We are currently looking into Lockdep >+ to see how to make it aware of stackable file systems. In the mean time, meantime >@@ -86,5 +86,12 @@ command: > > # mount -t unionfs -o remount,incgen none MOUNTPOINT > >+Note that the older way of incrementing the generation number using an >+ioctl, is no longer supported in Unionfs 2.0. Ioctls in general are not 2.1? Jan -- - 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/