linux-kernel - Re: INFO: possible circular locking dependency detected

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Message-ID: <45371B80.7060007@yahoo.com.au>
Date:	Thu, 19 Oct 2006 16:30:24 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andrew Morton <akpm@...l.org>
CC:	"alpha @ steudten Engineering" <alpha@...udten.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: INFO: possible circular locking dependency detected

Andrew Morton wrote:
> On Tue, 17 Oct 2006 00:32:44 +1000
> Nick Piggin <nickpiggin@...oo.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 .

Yeah you're right. It will be a hot allocation + reclaim path for high
bandwidth writes.

-- 
SUSE Labs, Novell Inc.
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