linux-kernel - Re: [patch] nfs: fix locking in nfs/inode.c in nfs_free_open

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Message-ID: <20070726200047.1225c084@localhost>
Date:	Thu, 26 Jul 2007 20:00:47 +0200
From:	Christian Krafft <krafft@...ibm.com>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [patch] nfs: fix locking in nfs/inode.c in
 nfs_free_open_context

On Thu, 26 Jul 2007 12:08:17 -0400
Trond Myklebust <trond.myklebust@....uio.no> wrote:

> On Thu, 2007-07-26 at 17:13 +0200, Arnd Bergmann wrote:
> > Unfortunately, you didn't answer my question. The observed problem is
> > that the final kref_put gets called at a time where there are still
> > references to the context in nfsi->open_files, and other threads
> > therefore do get at them.
> 
> Actually, I thought I did: I said we need to grab the lock atomically
> with the last put. See below.
> 
> > The patch holds the i_lock around the kref_put to prevent others
> > from searching the list. Ugly, I know, but it seems that's the
> > price you pay for using a kref in such unconventional ways, i.e.
> > not counting every reference.
> 
> Really ugly. Here's an alternative that is a lot more palatable.

Indeed, and it also compiles ;-)
I started a test run using this patch, we'll see in a few hours ...

-- 
Mit freundlichen Gruessen,
kind regards,

Christian Krafft
IBM Systems & Technology Group,
Linux Kernel Development
IT Specialist


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