Re: [PATCH v1 05/18] xprtrdma: Avoid using Write list for small NFS READ requests

Christoph Hellwig
2016-04-12T17:01:21Z

On Tue, Apr 12, 2016 at 10:49:24AM -0400, Chuck Lever wrote:
> >> No, pre-4.2 Linux servers have a bug that can be fixed by
> >> applying the above commit, which shouldn't be difficult to
> >> backport.
> >>
> >> Clients have always been allowed to send NFS READ this way.
> >
> > But the clients might be out in a the wild. I think we'll need at
> > least a mount option to work around them.
>
> Huh?
>
> I'm talking about non-Linux clients. RFC 5666 allows
> this behavior, it always has. The Linux server before
> 9d11b51ce7c1 is broken, full stop.

You are deliverately breaking exsisting and fairly recent clients.
I see why we want to do this, but there needs to be an options
that things keep working. The idea of upgrading your client from
4.6 to 4.7 and NFS simply not working anymore with the developer
knowing it and not providing a workaround is simply not an option.
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