linux-kernel - Re: NFS lockdep lock misordering mmap_sem<->i_mutex

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Message-ID: <20091216005308.GB3622@basil.fritz.box>
Date:	Wed, 16 Dec 2009 01:53:08 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org
Subject: Re: NFS lockdep lock misordering mmap_sem<->i_mutex_key with
	2.6.32-git1

> If you want to work around the problem rather than going for something

I am mostly interested in making the ugly warning on my systems
go away, preferably without breaking anything in the process.
Whatever works.

> like Peter's split up of the mmap() callback, then I'd suggest changing
> to using nfs_revalidate_mapping_nolock() instead. The fact that we are
> seeing these lock misordering warnings is proof that the call to
> nfs_revalidate_mapping() is not always a no-op.

I would say the interesting question is if there is really a expectation
that mmap does this kind of synchronization? 

Why in mmap, not somewhere else?

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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