Re: [PATCH] Disable NFS version 2

[Steve Dickson <SteveD@redhat.com>]

On 05/07/13 10:59, Chuck Lever wrote:
> Hi Steve-
> 
> On Jul 5, 2013, at 7:31 AM, Steve Dickson <SteveD@redhat.com> wrote:
> 
>> Hey,
>>
>> On 03/07/13 09:19, Chuck Lever wrote:
>>> Hi-
>>>
>>> I'm not opposed to this change, but we should have some public discussion about it first.
>>>
>>> If we make this proposed upstream change, NFSv2 will be built far less often and will be 
>>> a magnet for code rot.  It might make more sense to simply leave the "compile this out" 
>>> choice up to distributions...?
>> Code rot is a possibility for any code where default is 'n' so that means we should
>> never use it? If that is the case, we should have swap over NFS and Label NFS 
>> on be default on by default so those bits don't rote... My point being, I don't
>> think code rot should be a reason for us to maintain code people should not
>> be using in the first place...
> 
> In the case at hand, code rot isn't much of a risk if the point is to remove a feature.  
> But that point wasn't stated anywhere.
> 
>>> I'd like to reduce the risk of the kernel carrying  around code that no-one uses or 
>>> compiles.  If we truly want this off by default  everywhere, shouldn't we just 
>>> remove it?  (Is that the eventual goal?)
>> I would think so. Turn it off and see who screams.. Then get the clue-bat out for
>> for those people that do scream... ;-)  They can always turn it back on... 
> 
> If deprecation is the long-term goal, we ought to have a stated plan that we all 
> agree on.  We're talking about removing a feature of Linux NFS that has been a 
> mainstay for, literally, decades.  Make some noise, let people chime in, and publish 
> a plan so folks know what to expect.
That was the purpose of this patch... to start the conversation... 

> 
> We should also document publicly why we think NFSv2 support should go away.  Is it a 
< significant maintenance burden?  Is it a security problem?  Who are the stakeholders?
Its mostly maintenances and limited testing resource. I would rather use cycles
to fix/test v4... 
 
> 
>>> Should the server also disable NFSv2 support by default?  If not, then why is the 
>>> client special in this regard?
>> We have to start somewhere... It was just easier to start with the client. If 
>> Bruce is interested in dropping v2 support on the server, I will be more than
>> willing to looking into that... Actually it might just be a nfs-utils only thing...
> 
> It feels like we should have a plan for both the server and client.
I'm thinking we could do it separately...
 
> 
> You could remove NFSv2 support in nfs-utils on both sides, I would think.  Didn't you 
> already remove NFSv2 from the mount.nfs command's version negotiation?
Yes, the mount command no longer negotiates down to v2. The -o v2 mount
option still works. 

> 
> Deprecating a kernel feature also has a pathway through the staging tree, IIUC.  
> Would that be appropriate for NFSv2?  It may even be a requirement these days, but 
> I'm not sure.
Really? Anybody know what that pathway is?

> 
>>> Finally, if we go with something like this change, does this patch also need to 
>>> update the default configurations shipped with the kernel?
>> What "default configurations shipped with the kernel"? Isn't fs/nfs/Kconfig the
>> only place I need to turn it off?
> 
> arch/*/configs/*_defconfig
> 
> These were not updated when the NFS client was modularized, so they currently do not 
> list an explicit CONFIG_NFS_V2 setting.  IIUC that means changing Kconfig ought to be 
> enough.
Cool...

steved.
> 
>> Thanks for the cycles!
>>
>> steved.
>>
>>>
>>>
>>> On Jul 3, 2013, at 9:04 AM, Steve Dickson <steved@redhat.com> wrote:
>>>
>>>> This patch disables the NFS version 2 module from being compile by default.
>>>>
>>>> Signed-off-by: Steve Dickson <steved@redhat.com>
>>>> ---
>>>> fs/nfs/Kconfig | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
>>>> index 13ca196..6831a01 100644
>>>> --- a/fs/nfs/Kconfig
>>>> +++ b/fs/nfs/Kconfig
>>>> @@ -32,12 +32,12 @@ config NFS_FS
>>>> config NFS_V2
>>>> 	tristate "NFS client support for NFS version 2"
>>>> 	depends on NFS_FS
>>>> -	default y
>>>> +	default n
>>>> 	help
>>>> 	  This option enables support for version 2 of the NFS protocol
>>>> 	  (RFC 1094) in the kernel's NFS client.
>>>>
>>>> -	  If unsure, say Y.
>>>> +	  If unsure, say n.
>>>>
>>>> config NFS_V3
>>>> 	tristate "NFS client support for NFS version 3"
>>>> -- 
>>>> 1.8.1.4
>>>>
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>>>
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