From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Mon, 04 Dec 2006 03:35:06 -0800 (PST) Received: from mail.lst.de (verein.lst.de [213.95.11.210]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id kB4BYvaG002796 for ; Mon, 4 Dec 2006 03:34:59 -0800 Date: Mon, 4 Dec 2006 12:34:06 +0100 From: Christoph Hellwig Subject: Re: [PATCH] remove v_number Message-ID: <20061204113406.GC11074@lst.de> References: <20061129154729.GC6400@lst.de> <20061130003050.GG33919298@melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061130003050.GG33919298@melbourne.sgi.com> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: David Chinner Cc: Christoph Hellwig , xfs@oss.sgi.com On Thu, Nov 30, 2006 at 11:30:50AM +1100, David Chinner wrote: > On Wed, Nov 29, 2006 at 04:47:29PM +0100, Christoph Hellwig wrote: > > v_number is unused except for the naming some locks (which is a > > functionality totally unused by Linux), so remove it and assorted > > crap. Besides saving two words in struct vnode this also gets rid > > of a spinlock per inode allocation. > > Hmm - given that I've just used the v_number in post-mortem analysis > of a nasty bug to correlate the sequence of events during a series > of mkdir operations (i.e. transactions in the incore log buffers, > the resulting xfs_inodes and some screwed up dentries) that lead to > a BUG_ON being tripped in d_instantiate. > > So, while it appears to be unused, it is _very_ useful for > determining the SOE that has occurred in certain types of problems. > > FWIW, while analysing this crash dump a couple of days ago I was > wishing that dentries had an equivalent sequence number because > there is no way to tell what dentry was supposed to be related to > what inode after it got screwed up... Putting in sequence counting is trivial using kprobes. Will you put in this patch after I write you a kprobes modules to do the sequence numbering?