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Date: Mon, 26 Mar 2012 14:55:00 -0400 (EDT)
From: "Matt W. Benjamin" <matt@linuxbox.com>
To: Boaz Harrosh <bharrosh@panasas.com>
Cc: linux-nfs <linux-nfs@vger.kernel.org>,
        Ganesha NFS List <nfs-ganesha-devel@lists.sourceforge.net>,
        Trond Myklebust <Trond.Myklebust@netapp.com>
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Subject: Re: unlink within an open directory stream
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Hi,

Boaz:  we do not any longer send a readdir index.  We do send a cookieverf.

Fist of all, I haven't established that the issue we're actually observing is caused
by the Linux client sending old cookies to readdir(something).  However, if it is,
it's in no way better to try to make cookies "more persistent."  Nor should the Linux
client be expecting it.  The assumption is simply flawed.  The protocol introduced
cookie verifier (a LONG time ago) for a reason.

Matt
----- "Boaz Harrosh" <bharrosh@panasas.com> wrote:

> On 03/26/2012 11:25 AM, Myklebust, Trond wrote:
> 
> > On Mon, 2012-03-26 at 11:17 -0700, Boaz Harrosh wrote:
> >> On 03/24/2012 10:12 AM, Myklebust, Trond wrote:
> >>
> >>
> >> It's the new (post RHEL 6.0 Kernel) NFS need for opendir after an
> unlink.
> > 
> > What?
> > 
> 
> 
> The links below report on regression in RHEL 6.2 which have a new NFS
> implementation where  6.0 used to be fine.
> (Or it's what I understood from the reporters)
> 
> <snip>
> 
> > 
> 
> > No.
> > 
> > If the server supports permanent readdir cookies, then there is no
> need
> > for opendir after unlink.
> > 
> > If the server does not have permanent readdir cookies, then our
> client
> > has never supported it anyway (nor will it ever do so). That whole
> > 'cookieverf' READDIR bullshit has never provided a workable model
> for a
> > POSIX client...
> 
> 
> Thanks Trond for the explanation. Forgive my slowness. So you are
> saying that with knfsd it's actually filesystem dependent and maybe
> the reporters did not compare apples-to-apples and the difference is
> in the behind file system.
> 
> Matt I'm sure Trond is right with regard to Ganesha, because we
> send a readdir index and a cookieverf, which will change after
> unlink. Since the application does not call opendir again the
> client will send the old cookies, which is now a different file
> or might get out-of-bounds for Ganesha.
> 
> Let me think about it a bit. I'm sure we can send a Better
> 64bit cookie, which will be more persistent, even across unlinks.
> 
> > 
> > 
> 
> 
> Thanks
> Boaz

-- 
Matt Benjamin
The Linux Box
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