linux-kernel - RE: [ 16/46] NFSv4.1: Remove a bogus BUG_ON() in nfs4_layoutreturn

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Date:	Mon, 17 Sep 2012 13:05:19 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ben Hutchings <ben@...adent.org.uk>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	Boaz Harrosh <bharrosh@...asas.com>,
	Tigran Mkrtchyan <tigran.mkrtchyan@...y.de>
Subject: RE: [ 16/46] NFSv4.1: Remove a bogus BUG_ON() in
 nfs4_layoutreturn_done

> -----Original Message-----
> From: Greg Kroah-Hartman [mailto:gregkh@...uxfoundation.org]
> Sent: Sunday, September 16, 2012 12:37 PM
> To: Ben Hutchings
> Cc: Myklebust, Trond; linux-kernel@...r.kernel.org;
> stable@...r.kernel.org; Boaz Harrosh; Tigran Mkrtchyan
> Subject: Re: [ 16/46] NFSv4.1: Remove a bogus BUG_ON() in
> nfs4_layoutreturn_done
> 
> On Sun, Sep 16, 2012 at 05:33:03PM +0100, Ben Hutchings wrote:
> > On Wed, 2012-09-12 at 16:39 -0700, Greg Kroah-Hartman wrote:
> > > From: Greg KH <gregkh@...uxfoundation.org>
> > >
> > > 3.0-stable review patch.  If anyone has any objections, please let me
> know.
> > >
> > > ------------------
> > >
> > > From: Trond Myklebust <Trond.Myklebust@...app.com>
> > >
> > > commit 47fbf7976e0b7d9dcdd799e2a1baba19064d9631 upstream.
> > >
> > > Ever since commit 0a57cdac3f (NFSv4.1 send layoutreturn to fence
> > > disconnected data server) we've been sending layoutreturn calls
> > > while there is potentially still outstanding I/O to the data
> > > servers. The reason we do this is to avoid races between replayed
> > > writes to the MDS and the original writes to the DS.
> > >
> > > When this happens, the BUG_ON() in nfs4_layoutreturn_done can be
> > > triggered because it assumes that we would never call layoutreturn
> > > without knowing that all I/O to the DS is finished. The fix is to
> > > remove the BUG_ON() now that the assumptions behind the test are
> > > obsolete.
> > >
> > > Reported-by: Boaz Harrosh <bharrosh@...asas.com>
> > > Reported-by: Tigran Mkrtchyan <tigran.mkrtchyan@...y.de>
> > > Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > [...]
> >
> > The upstream commit has:
> >
> >     Cc: stable@...r.kernel.org [>=3.5]
> >
> > and so I ignored it for 3.2.  Is it actually needed for the earlier
> > stable series?
> 
> Crud, I missed that somehow :(
> 
> Trond, should I revert this in 3.0 and 3.4 stable kernels?

Hi Greg,

Applying it to those kernels should be unnecessary but harmless, so if you've already applied them then I'd say just keep them.

Cheers
  Trond
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