when should the client request a directory delegation?

[Jeff Layton <jlayton@kernel.org>]

I've started work on a patchset to add support for directory delegations
to the Linux kernel client and server. It's still too rough to post at
this point, and for now, I'm just cobbling in a ioctl to drive it.

As I started working on some of the client bits, however, I realized
that I don't really have a clear picture as to when the client should
request a delegation on a directory. It seems like there are a lot of
things we could do:

One idea: request one on an initial directory readdir. So maybe when the
offset is 0 and we don't have a dir delegation already, do:

	PUTFH:GET_DIR_DELEGATION:READDIR

Or, maybe just do it on any readdir when we haven't requested one in a
little while?

We could also do one on every lookup, when we expect that the result
will be a directory. I'm not sure if LOOKUP_DIRECTORY would be a
sufficient indicator or if we'd need the vfs to indicate that with a new
flag.

Would we also want to request one after a mkdir?

	PUTFH:CREATE:GET_DIR_DELEGATION:GETFH:GET_DIR_DELEGATION:...

Assuming we can get this all working, what should drive the client to
issues GET_DIR_DELEGATION ops?
-- 
Jeff Layton <jlayton@kernel.org>