Re: [PATCH 2/2] Enable v4 mounts when either "nfsvers=4" or "vers=4" option are set (vers-02)

[Steve Dickson <SteveD@redhat.com>]

On 08/25/2009 04:49 PM, Trond Myklebust wrote:
> On Tue, 2009-08-25 at 16:15 -0400, Steve Dickson wrote:
>>
>> On 08/25/2009 03:32 PM, Chuck Lever wrote:
>>> On Aug 25, 2009, at 3:18 PM, Steve Dickson wrote:
>>>> On 08/25/2009 02:59 PM, Chuck Lever wrote:
>>>>> On Aug 25, 2009, at 1:55 PM, Steve Dickson wrote:
>>>>>> commit 1471d23d692efc7388794a8a3c3b9e548d1c5be8
>>>>>> Author: Steve Dickson <steved@redhat.com>
>>>>>> Date:   Tue Aug 25 12:15:18 2009 -0400
>>>>>>
>>>>>>   Make sure umount use correct fs type.
>>>>>>
>>>>>>   umounts use the fs type in /etc/mtab to determine
>>>>>>   which file system is being unmounted. The mtab
>>>>>>   entry is create during the mount. To ensure the
>>>>>>   correct entry is create when the fs type changes
>>>>>>   due to the mount options, the address of the fs_type
>>>>>>   variable has to be passed so it can be updated.
>>>>>
>>>>> In general, my policy is to record the user requested mount options in
>>>>> /etc/mtab, and let umount.nfs handle renegotiating as needed.  For
>>>>> version/transport this means that the server's configuration can change
>>>>> between the mount and the umount, and the umount will still work.
>>>>>
>>>>> Perhaps this is not a consideration for NFSv4, but leaving the mount
>>>>> options as specified by the user would save the need to update the fs
>>>>> type, and would be a consistent policy for v2, v3, and v4.  I think it
>>>>> would be cleaner to teach umount.nfs to do the right thing with "-t nfs
>>>>> -o v4" rather than rewriting the options in /etc/mtab.
>>>> Since nfs4 is truly a separate/different file system from nfs in the
>>>> kernel, I think we should continue making that distinction in system
>>>> files like mtab and /proc/mounts....
>>>
>>> We are teaching mount.nfs not to care about nfs/nfs4 (at least
>>> externally).  Why should umount.nfs?
>> That's not quite accurate... IMHO.. I see it as we are teach mount.nfs to
>> accept new command line arguments that will cause a nfs4 file system
>> to be mounted... and that is done by caring which fs type mount is
>> dealing with... 
> 
> So, why couldn't we just do this in the kernel? It should be easily
> doable to set nfs -overs=4 to mount an NFSv4 filesystem. We only have to
> do this for text mounts...
Basically time to market.... A kernel patch will not make into a mainstream
kernel until 2.6.32 which is in the distant future... verses having this
patch committed in the very near future (like today! ;-) ). 

Plus its historical reasons... Things like this have always been done in 
in user level code since its much easier to change user level code that it
is kernel.

With that said, I will be more than willing to come up with kernel patch
which in the end would make these patch obsolete... but again that
would be in the distant future... 

steved.