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Date: Wed, 18 Oct 2006 23:02:43 -0700
From: Andrew Morton <akpm@osdl.org>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: "alpha @ steudten Engineering" <alpha@steudten.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: INFO: possible circular locking dependency detected
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On Tue, 17 Oct 2006 00:32:44 +1000
Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> alpha @ steudten Engineering wrote:
> > =======================================================
> > [ INFO: possible circular locking dependency detected ]
> > 2.6.18-1.2189self #1
> > -------------------------------------------------------
> > kswapd0/186 is trying to acquire lock:
> >  (&inode->i_mutex){--..}, at: [<c0326e32>] mutex_lock+0x21/0x24
> > 
> > but task is already holding lock:
> >  (iprune_mutex){--..}, at: [<c0326e32>] mutex_lock+0x21/0x24
> > 
> > which lock already depends on the new lock.
> 
> Thanks. __grab_cache_page wants to clear __GFP_FS, because it is
> holding the i_mutex so we don't want to reenter the filesystem in
> page reclaim.

We want to be able to enter page reclaim while holding i_mutex.  Think what
the effect of not doing this would be upon write() (!)

This warning is more fallout from ntfs's insistence on taking i_mutex in
its clear_inode().  See lengthy and unproductive discussion at
http://lkml.org/lkml/2006/7/26/185 .

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