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From: Vishal Thanki <vishalthanki@gmail.com>
Date: Fri, 23 Dec 2011 17:09:01 +0530
Message-ID: <CAC3a_SBcMYRz-dQGLFzqBW5+_gB9P_GuVqiXtG9jGgtmr5Rj7Q@mail.gmail.com>
Subject: Re: LAYOUTGET failure handling
To: linux-nfs@vger.kernel.org
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Sender: linux-nfs-owner@vger.kernel.org

On Fri, Dec 23, 2011 at 4:51 PM, Vishal Thanki <vishalthanki@gmail.com> wrote:
> Hi,
>
> I am learning NFS (and pNFS) and not much familiar with its
> implementation in Linux kernel. I have a question on the LAYOUTGET
> operation.
>
> I have a pNFS server setup which fakes most of the pNFS operations.
> The "layout_get" implementation simply returns "-ENOENT". I am not
> sure how this should be treated on the pNFS client side. In my
> experiment, I am mounting the pNFS server and trying to read a file
> (using "cat"). On wireshark trace (attached with the mail), I could
> see that LAYOUTGET fails with NFS4ERR_BADLAYOUT error, but afterwards
> I see the READ request from client and it is handled gracefully (and I
> can see the contents of the file). Is this appropriate behavior?
>
> I am using RHEL6.1 (with pNFS patch for kernel 2.6.32 applied) on
> server, and client is RHEL6.1 stock kernel.
>
> I am sorry if this is not the appropriate forum for such kind of
> questions, and pardon my ignorance/lack of knowledge in the domain.
>
> Thanks,
> Vishal

I noticed that "send_layoutget" function is invoked from
pnfs_update_layout. All the callers of pnfs_update_layout seem to
ignore the return value (struct pnfs_layout_segment *). The callers of
this functions are following (if i am not missing any other places):

nfs_write_begin,
nfs_readpage_async,
nfs_readpages

Vishal