Large SMBwriteX testing.

[Jeremy Allison <jra@samba.org>]

Hi Steve,

	I've finished adding the ability for smbd to support up to
16MB writeX calls in the latest git 3.2 tree.

To enable, set the parameter :

min receivefile size = XXX

where XXX is the smallest writeX you want to handle with recvfile.

The linux kernel doesn't yet support zerocopy from network to
file (ie. splice only works one way currently) so it's emulated
in userspace (with a 128k staging buffer) for now.

Also it must be an unsigned connection (for obvious reasons).

Once you've set this param smbd will start reporting
CIFS_UNIX_LARGE_WRITE_CAP on a SMB_QUERY_CIFS_UNIX_INFO:
call and you should be good to go. You'll need to use
a writeX call identical to Windows (14 wct with a 1 byte
pad field) in order to trigger the new code.

Let me know if you get the chance to test it and if
it makes a speed difference for CIFSFS.

Cheers,

	Jeremy.