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Date:      Mon, 27 Jul 1998 07:10:52 +0900 (JST)
From:      Michael Hancock <michaelh@cet.co.jp>
To:        Chris Radek <cradek@in221.inetnebr.com>
Cc:        freebsd-current@FreeBSD.ORG
Subject:   Re: ext2fs and sync panic, still
Message-ID:  <Pine.SV4.3.95.980727070724.4390B-100000@parkplace.cet.co.jp>
In-Reply-To: <m0z0Xzu-000PTPC@hoser.inetnebr.com>

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Have you looked at the ffs version of the source?  There aren't too many
people working on ext2fs so I would try getting familiar with ffs since it
is kept up to date, obviously.  Ext2fs is derived from ffs.

Regards,


Mike Hancock

On Sun, 26 Jul 1998, Chris Radek wrote:

> 
> I have run into the problem where mounting an ext2fs r/w panics as 
> soon as sync is called.  r/o has no problems.  This is from current 
> as of a couple days ago.
> 
> This panic is due to a null pointer dereference in ext2_sync
> (ext2_vfsops.c:858) caused by a vnode with a NULL v_data.  There is a 
> comment in ext2_vget warning of a blocking MALLOC() that might cause 
> this, but I don't understand the comment.  Can someone explain this 
> to me?  My first thought was that this was an SMP locking problem, 
> but a uniprocessor kernel gives the same behavior.
> 
> I could of course skip syncing the vnode if its v_data is NULL but it 
> seems to me like having this bogus vnode in the list signifies a 
> bigger problem.  There is some locking code in ext2_vget but I don't 
> understand it.  Is it possible that a sync can be called between 
> getnewvnode() and filling in the structure?  (Please excuse any 
> questions that might be stupid...  I'm new to this!)
> 
> Does anyone have insight into this problem?  Charlie Fluffy 
> (fluffy@int.tele.dk) reported the same thing on June 28th and it 
> doesn't look like anybody has made any progress.
> 
> Unfortunately I can't get a memory dump from this machine because I am
> running it diskless.  (correct me if this is wrong!)  I want to
> convert it (gently) from Linux and to do this I need to run it diskless
> and mount my ext2 filesystems.
> 
> Thanks,
> 
> Chris


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