From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q03Mhq88084264 for ; Tue, 3 Jan 2012 16:43:52 -0600 Message-ID: <4F0384A4.6000505@sgi.com> Date: Tue, 03 Jan 2012 16:43:48 -0600 From: Bill Kendall MIME-Version: 1.0 Subject: Re: xfsrestore: incorrect restore if file becomes a dir References: <20111226201856.GA3909@davidb.org> <4F036FF6.2080501@sgi.com> <20120103213147.GS23662@dastard> In-Reply-To: <20120103213147.GS23662@dastard> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: David Brown , xfs@oss.sgi.com On 01/03/2012 03:31 PM, Dave Chinner wrote: > On Tue, Jan 03, 2012 at 03:15:34PM -0600, Bill Kendall wrote: >> On 12/26/2011 02:18 PM, David Brown wrote: >>> http://oss.sgi.com/bugzilla/show_bug.cgi?id=915 >>> >>> I've had this happen again. It appears to be the case if between >>> incremental dumps, a file is deleted and a directory is created that >>> gets the same inode number. The restore leaves a file in place of the >>> directory. If the new directory has any contents, xfsrestore prints a >>> warning, and doesn't restore the subdirectory contents. >>> >>> Given the sparseness of inodes, this doesn't seem to occur all that >>> frequently, but I do have a couple of backups that exhibit the >>> behavior. If no one has any ideas, I'll start digging through >>> xfsrestore to see if I can figure out what is happening. >> >> I haven't looked at the relevant code, but it sounds like the inode >> generation number would also have to be the same in order for this >> to happen. Two inodes from separate backups are only considered to >> be the same file or directory if the inode number and the lower 12 >> bits of the inode generation number are the same. > > Why does dump only use the lower twelve bits? The on-disk generation > number is 32 bits and we use all of it (by way of random numbers) to > distinguish between different inode generations. That sounds like > something that needs to be fixed.... I don't know the history there, but it dates back to when the generation number was not randomly initialized. So an inode had to be reused 4,096 times for a collision to occur. With the current scheme (initially random, then incremented) there would be cases where a collision happens more frequently. I agree, it should be changed. Bill _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs