Re: The next step: nfsvers=4

[Steve Dickson <SteveD@redhat.com>]

Muntz, Daniel wrote:
>  
> 
>> -----Original Message-----
>> From: Steve Dickson [mailto:SteveD@redhat.com] 
>> Sent: Thursday, March 19, 2009 9:18 AM
>> To: linux NFS Mailing list
>> Subject: The next step: nfsvers=4
>>
>> As I see it, the next step to seamlessly move to V4 as the 
>> default is to make 'mount -o nfsvers=4' actually do a v4 mount... 
>>
>> There are two obvious place we can make this change.
>> In the kernel and/or in the mount command... 
>>
>> Looking at the kernel, since v3 and v4 truly two different 
>> file systems its seems a bit late for the nfs_get_sb() to all 
>> of sudden have to change file system type. Meaning when 
>> nfs_get_sb() sees the "nfsvers=4" somehow it would have to 
>> back out and call nfs4_get_sb(), which obviously is a bit hacky.... 
>>
>> Now I guess we could have one nfs_get_sb() for both v3 and v4.
>> Where the nfs_get_sb() could peek into the options data to 
>> see which version is needed. This would also mean the mount 
>> command would always have to set a version so when the "nfsvers=" 
>> options is not set, the kernel would know which version to use.
>> Again, this feels a bit hacky as well but doable... 
>>
>> At least to me, what seems like the best option is to have 
>> the mount.nfs binary early on intercept "nfsvers=4" option 
>> and then change the fs_type to "nfs4", which would allow 
>> everything to "trickle down" as it does today... Again to me, 
>> that seem like the least intrusive way to do it...
>>
>> Comments? Is there other ways?
> 
> Whichever way it's done, if v4 becomes the default, don't forget to also
> make the default behavior be that the system will fall back and try a v3
> mount if v4 isn't available.  Otherwise you'll break a huge percentage
> of your user base.  Of course then you also have to deal with the
> semantics of how to specifify "only v4" vs. "try v4 first and fall
> back".
No worries... falling back to v3/v2 will be the will definitely
happen before the switch is made... 

This was this is reason I'm pushing for a mount configuration file.
So the semantics of which version is or is not tried can be defined locally...

steved.