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Date: Wed, 11 Jan 2006 13:07:28 -0800
From: Andrew Morton <akpm@osdl.org>
To: Arjan van de Ven <arjan@infradead.org>
Cc: ak@suse.de, linux-kernel@vger.kernel.org, sct@redhat.com, mingo@elte.hu
Subject: Re: 2.6.15-git7 oopses in ext3 during LTP runs
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Arjan van de Ven <arjan@infradead.org> wrote:
>
> On Wed, 2006-01-11 at 12:46 -0800, Andrew Morton wrote:
> > Andi Kleen <ak@suse.de> wrote:
> > >
> > > 
> > > Running LTP with the default runfile on a 4 virtual CPU x86-64 
> > > system gives
> > > 
> > > To reproduce: run ltp 20040908 (newer one will probably work
> > > too) with runltp -p -q -l `uname -r` on a ext3 file system
> > > 
> > > config is x86-64 defconfig.
> > > 
> > 
> > mutex_trylock() is returning the wrong value.  fs/super.c:write_super()
> > clearly took the lock.
> 
> 
> the conversion is buggy.
> 
> mutex_trylock has the same convention as spin_try_lock (which is the
> opposite of down_trylock). THe conversion forgot to add a !
> 
> --- linux-2.6.15/fs/ext3/super.c~	2006-01-11 21:54:13.000000000 +0100
> +++ linux-2.6.15/fs/ext3/super.c	2006-01-11 21:54:13.000000000 +0100
> @@ -2150,7 +2150,7 @@
>  
>  static void ext3_write_super (struct super_block * sb)
>  {
> -	if (mutex_trylock(&sb->s_lock) != 0)
> +	if (!mutex_trylock(&sb->s_lock) != 0)
>  		BUG();
>  	sb->s_dirt = 0;
>  }

We expect the lock to be held on entry.  Hence we expect mutex_trylock()
to return zero.