RFC: changing the default NFSv4 minor version?

[Rick Macklem]

Daniel Ebdrup Jensen wrote:
>On Thu, May 13, 2021 at 11:02:35PM +0000, Rick Macklem wrote:
>>Hi,
>>
>>I believe that NFSv4.1 and NFSv4.2 are now mature in freebsd-current/main.
>>I also believe that NFSv4.1/4.2 is a better protocol than NFSv4.0.
>>(In particular, the sessions mechanism for "exactly once RPC semantics"
>> is a significant improvement over the duplicate request cache for NFSv4.0,
>> plus other improvements.)
>>
>>Right now, the FreeBSD NFSv4 client will use NFSv4.0 unless the
>>"minorversion" mount option is used to set the minor version to 1 or 2.
>>
>>The Linux client uses the highest minor version supported by both
>>client and server by default.
>>I'd like to propose that the default behaviour of the FreeBSD client
>>be changed to do the same, so that NFSv4.1/4.2 will be used when possible.
>>--> The "minorversion" mount option could still be used to override the
>>      above default.
>>
>>I have hesitated doing this change because it could be considered a POLA
>>violation, but I think the change from 4.0->4.1/4.2 will normally be a
>>neutral to positive experience. (To be honest, I suspect most won't notice
>>the change.)
>>
>>How do others feel about this change?
>>
>>rick
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>
>Hi Rick,
>
>      If I understand your plans correctly, you're not going to be making
>      it so that minorversion=N complains?
If by "complains" you mean "mount fails if the minor version is not supported
by the server" then, yes, I am not planning on changing that.

>     In that case, I don't quite understand how it can be a POLA
>      violation, since presumably it'll fall back to NFSv4.0 if that's
>      the only thing that's supported by ntpd on some other system.
The POLA violation is that, now, a mount without "minorversion" always
uses NFSv4.0 and fails to mount if the server does not support NFSv4.0.

>      At any rate, I'm all for it since I'm already using NFSv4.2. :)
Thanks for the input, rick

Yours,
Daniel Ebdrup Jensen