From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Nick Piggin <npiggin@suse.de>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Trond Myklebust <trond.myklebust@fys.uio.no>,
Hugh Dickins <hugh@veritas.com>
Subject: Re: [PATCH 3/3] nfs: use ->mmap_prepare() to avoid an AB-BA deadlock
Date: Wed, 14 Nov 2007 22:31:45 +0100 [thread overview]
Message-ID: <1195075905.22457.3.camel@lappy> (raw)
In-Reply-To: <20071114212246.GA31048@wotan.suse.de>
On Wed, 2007-11-14 at 22:22 +0100, Nick Piggin wrote:
> On Wed, Nov 14, 2007 at 09:01:39PM +0100, Peter Zijlstra wrote:
> > Normal locking order is:
> >
> > i_mutex
> > mmap_sem
> >
> > However NFS's ->mmap hook, which is called under mmap_sem, can take i_mutex.
> > Avoid this potential deadlock by doing the work that requires i_mutex from
> > the new ->mmap_prepare().
> >
> > [ Is this sufficient, or does it introduce a race? ]
>
> Seems like an OK patchset in my opinion. I don't know much about NFS
> unfortunately, but I wonder what prevents the condition fixed by
> nfs_revalidate_mapping from happening again while the mmap is active...?
As the changelog might have suggested, I'm not overly sure of the nfs
requirements myself. I think it just does a best effort at getting the
pages coherent with other clients, and then hopes for the best.
I'll let Trond enlighten us further before I make an utter fool of
myself :-)
next prev parent reply other threads:[~2007-11-14 21:33 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-14 20:01 [PATCH 0/3] mmap vs NFS Peter Zijlstra
2007-11-14 20:01 ` [PATCH 1/3] mm: pull mmap_sem into do_mmap{,_pgoff} Peter Zijlstra
2007-11-14 20:01 ` [PATCH 2/3] vfs: ->mmap_prepare() Peter Zijlstra
2007-11-14 20:01 ` [PATCH 3/3] nfs: use ->mmap_prepare() to avoid an AB-BA deadlock Peter Zijlstra
2007-11-14 21:22 ` Nick Piggin
2007-11-14 21:31 ` Peter Zijlstra [this message]
2007-11-14 21:41 ` Trond Myklebust
2007-11-14 21:50 ` Peter Zijlstra
2007-11-14 22:18 ` Trond Myklebust
2007-11-14 22:24 ` Nick Piggin
2007-11-14 22:53 ` Trond Myklebust
2007-11-14 20:19 ` [PATCH 0/3] mmap vs NFS Peter Zijlstra
2007-11-14 21:27 ` Trond Myklebust
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