Re: [PATCH 1/1] mount: RDMA processing in the mount command is broken

[Chuck Lever <chuck.lever@oracle.com>]

On Sep 2, 2010, at 6:04 PM, Steve Dickson wrote:

> 
> 
> On 09/02/2010 04:35 PM, Chuck Lever wrote:
>> 
>> On Sep 2, 2010, at 4:00 PM, Steve Dickson wrote:
>> 
>>> The mounting code that process RMDA mounts is broken in a few places
>>> 
>>> First with '-o proto=rdma' was broken because nfs_get_proto()
>>> did not how to convert a netid of 'rdma' in to a AF_INET
>>> address family.
>>> 
>>> Secondly, '-o rdma' was broken because po_get() was being using
>>> to detect the existence of 'rdma' in the options. With '-o rdma'
>>> there is no value associated with that option so po_get()
>>> was always return NULL.
>> 
>> Looking at nfs(5), "rdma" as a stand-alone option isn't documented.  Only "proto=rdma" appears to be mentioned.  Thus I would argue that this is already behaving correctly.
>> 
>> Are you proposing to add support for "-o rdma" ?  If so what would that mean?
> See Documentation/filesystems/nfs/nfs-rdma.txt
> 
> I see no problem in handing this same why we handle 'udp' and 'tcp'

I used nfs(5) as the specification for the text-based option parsing support in the mount.nfs command, since that's generally what administrators and packagers look to when trying to figure out how to use mount.

I don't see any evidence in utils/mount/* that a stand-alone "rdma" option was ever supported.  The kernel documentation could be wrong, or could be based on the kernel's mount option parser, which does support a stand-alone "rdma" mount option.  So, my opinion is that, today, mount.nfs is not misbehaving by rejecting the "rdma" mount option.  This is not a bug, it's working as designed.

To add an "rdma" mount option, therefore, is really introducing a new feature to mount.nfs.  So, I think such a patch needs appropriate changes to user documentation, and this mode of invoking rdma needs testing, since clearly no-one noticed it was missing until now.

As with the rpc.nfsd changes, these mount option changes are two logically distinct but related changes that belong in separate patches.

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