Re: [nfsv4] Read delegations and LOCK operation

[Rick Macklem <rmacklem at uoguelph.ca>]

On Wed, 28 Oct 2009, Noveck, Dave wrote:

> > Mandatory byte range locking requests that there
> > always be a byte range lock that encompasses the
> > byte range a process or client reads or writes.
>
> Can you point me to something that says that?  I've been googling
> looking for some clear specification of what mandatory byte range locks
> actually do, but this seems hard to believe.  It means that if you set
> the mode bits indicating mandatory locking, you can't do an ordinary
> read of the file; you would need a special program that did locks around
> the reads.
I believe Mike was referring to Sec. 9.3.3 of rfc3530, which requires
clients to hold byte range locks for byte ranges being cached.
--> The I/O is allowed, but can't be cached unless the range is locked
    by the client.

As I noted before, since I client has no way of knowing if a server
is enforcing mandatory locking on a given file at any point in time,
this is all kinda theoretical.

I cover my b... by saying that any mount done against a server that
might be doing mandatory locking needs to be mounted with caching
disabled. (No one will actually do this, but...)

rick