netdev - Re: It's back! (Re: [REGRESSION] NFS is creating a hidden port (left over from xs

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Message-ID: <20160630160726.304a3d14@gandalf.local.home>
Date:	Thu, 30 Jun 2016 16:07:26 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Trond Myklebust <trondmy@...marydata.com>
Cc:	Jeff Layton <jlayton@...chiereds.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Schumaker Anna <anna.schumaker@...app.com>,
	"Linux NFS Mailing List" <linux-nfs@...r.kernel.org>,
	"Linux Network Devel Mailing List" <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	Fields Bruce <bfields@...ldses.org>
Subject: Re: It's back! (Re: [REGRESSION] NFS is creating a hidden port
 (left over from xs_bind() ))

On Thu, 30 Jun 2016 18:30:42 +0000
Trond Myklebust <trondmy@...marydata.com> wrote:

> Wait. So the NFS mount is still active, it’s just that the socket
> disconnected due to no traffic? That should be OK. Granted that the
> port can’t be reused by another process, but you really don’t want
> that: what if there are no other ports available and you start
> writing to a file on the NFS partition?

What would cause the port to be connected to a socket again? I copied a
large file to the nfs mount, and the hidden port is still there?

Remember, this wasn't always the case, the hidden port is a recent
issue.

I ran wireshark on this and it appears to create two ports for NFS. One
of them is canceled by the client (sends a FIN/ACK) and this port is
what lays around never to be used again, and uses the other port for
all connections after that.

When I unmount the NFS directory, the port is finally freed (but has no
socket attached to it). What is the purpose of keeping this port around?

I can reproduce this by having the client unmount and remount the
directory.

-- Steve