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

From: Chuck Lever <chuck.lever@oracle.com>
To: Steve Dickson <SteveD@redhat.com>
Cc: Linux NFS Mailing list <linux-nfs@vger.kernel.org>,
	Linux NFSv4 mailing list <nfsv4@linux-nfs.org>
Subject: Re: [PATCH 2/2] Enable v4 mounts when either "nfsvers=4" or "vers=4" option are set (vers-02)
Date: Tue, 25 Aug 2009 15:32:36 -0400	[thread overview]
Message-ID: <7AB7BC01-F9E5-4611-BB4B-2B6E27069631@oracle.com> (raw)
In-Reply-To: <4A943914.9020104@RedHat.com>

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?

> Also note there is no '-o ' flag to umount so 'umount -t nfs -o v4' is
> not valid... but 'umount -t nfs' is and works on both nfs4 and nfs
> file systems.

Sorry I wasn't clear.  I meant that umount.nfs should be able to read  
a line in /etc/mtab that has "nfs" and "v4" and do the right thing...  
then you wouldn't have to change the fs_type in /etc/mtab at all.

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com