SMB/CIFS compounding support

Performance of the kernel SMB3 code in my testing was quite good, although in some cases Volker's userspace (Samba tool) smbclient improvements can beat it. In most of my large i/o tests it was faster (Linux to Linux, on localhost) than NFSv3 or NFSv4.2.

But ... SMB3 kernel client without compounding (and handle caching and directory leases) can be much slower for large directories and metadata searches. This is very exciting work that Ronnie at Redhat is doing to introduce compounding into the kernel client (cifs.ko) for SMB3.

In addition, Long Li's work (various "smbdirect" - ie network file system i/o over RDMA) is impressive. Windows, NetApp etc. servers support RDMA and it is nice to be able to take advantage of this with very easy to use SMB3 mounts using the work Long Li has done. He has a pending patchset as well for improving SMB3 direct i/o in the kernel. Hard to imagine a userspace FUSE client able to keep up with that.