Re: [nfsv4] [internet-drafts@ietf.org: New Version Notification for draft-hellwig-nfsv4-rdma-layout-00.txt]

Tom Talpey <tom@talpey.com> Mon, 31 July 2017 14:28 UTC

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From: Tom Talpey <tom@talpey.com>
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Date: Mon, 31 Jul 2017 10:28:26 -0400
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Subject: Re: [nfsv4] [internet-drafts@ietf.org: New Version Notification for draft-hellwig-nfsv4-rdma-layout-00.txt]
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On 7/19/2017 3:48 AM, Christoph Hellwig wrote:
> On Mon, Jul 17, 2017 at 11:49:35AM +0200, Chuck Lever wrote:
>> Also, if the connection to a DS is lost, more than a
>> reconnect is necessary. The client will need to take steps to
>> get the server to re-register the memory and send fresh
>> handles.
> 
> Yes - a connection loss with this layout is an implicit CB_RECALL
> with LAYOUTRECALL4_ALL scope.

I'm concerned with making the upper layer statement based on the
lower layer event. The connection loss is experienced by each end
at different times, and a very different state is entered depending
on whch end sees it first.

If the client sees the RDMA layout connection loss, it may promptly
reconnect and attempt to reacquire the layout. When the server sees
this, it believes that a layout is already granted. Is the server
required to grant it again? How does it know which old layout to free,
with its queue pair and memory handles, etc?

On the other hand, if the server sees a connection loss, your
"implicit" statement seems to imply it will not recall the layout
on the operation channel. Does the client need to see its layout
connection break to discover this?

Tom.