linux-kernel - Re: [PATCH] NFS: Retry the CLOSE if the embedded GETATTR is rejected with ERR

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Message-ID: <20201118212935.GA12762@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>
Date:   Wed, 18 Nov 2020 21:29:35 +0000
From:   Anchal Agarwal <anchalag@...zon.com>
To:     Trond Myklebust <trondmy@...merspace.com>
CC:     "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] NFS: Retry the CLOSE if the embedded GETATTR is rejected with
 ERR_STALE

On Wed, Nov 18, 2020 at 03:17:20AM +0000, Trond Myklebust wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> 
> 
> 
> On Wed, 2020-11-18 at 00:24 +0000, Anchal Agarwal wrote:
> > If our CLOSE RPC call is rejected with an ERR_STALE error, then we
> > should remove the GETATTR call from the compound RPC and retry.
> > This could happen in a scenario where two clients tries to access
> > the same file. One client opens the file and the other client removes
> > the file while it's opened by first client. When the first client
> > attempts to close the file the server returns ESTALE and the file
> > ends
> > up being leaked on the server. This depends on how nfs server is
> > configured and is not reproducible if running against nfsd.
> 
> That would be a seriously broken server. If you return NFS4ERR_STALE to
> the client, you cannot expect any further interaction with that file
> from the client. It won't try to send CLOSE or DELEGRETURN or any other
> stateful operation.
>
In this scenario, the setup we have at EFS is more of a distributed fashion. Multiple
clients are connected to multiple servers with a common filesystem. So the above
scenario leads to leaked open file handles on the client that tries to close deleted
file. So I was of the view, in that case client could retry close without getattr
in the close sequence without anything to do on server side.

Thanks,
Anchal Agarwal
> --
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@...merspace.com
> 
>