Patch for GPFS support

[Wayne Davison]

On Tue, Oct 21, 2008 at 10:02:42AM +1100, Ronnie Sahlberg wrote:
> This patch provides extensions to RSYNC to map to and use filesystem
> extensions present in the IBM GPFS cluster filesystem.

Thanks for the patch!  I have looked over your changes, and I have some
preliminary feedback:

 - When a protocol change requires an new option to be used, there's not
   usually a need to bump the protocol version.

 - It is rsync's job to pass options to the remote server, not the user.
   When a new option is added, you should change the server_options()
   function in options.c rather than requiring the user to use
   --rsync-path (or --remote-options).

 - That said, I'd prefer a change such as this to not need a new option.
   Ideally, rsync would notice when a filesystem supported GPFS
   attributes and include the data in the regular xattr data using a
   special xattr name, such as "user.rsync.GPFS".  That would require no
   protocol change, and would even allow the backing up of GPFS info to
   a non-GPFS disk.  Note that the xattr code might need some speed
   improvements to handle the case where every file has a chunk of
   differing data, as it currently tries to search for matching data
   between files, and its search algorithm is not very good.  You appear
   to have supplied a better search algorithm in your patch, which might
   be good to use in the xattr and ACL code.

 - I would be interested to know if the GPFS data could be read in
   smaller pieces than one big chunk, as it might be better to fit the
   data into rsync's current data structures in separate bits.  E.g. if
   there is ACL info in the data, can the ACL code be extended to handle
   the data and give the user the option of choosing what parts of the
   GPFS data they want to copy?

 - Are there application interface docs on-line?  I found some man pages
   in a tar file, but on-line docs would be nice too.

..wayne..