Hello,

I've just tripped over two new interfaces where I (for reasons I don't 
know or remember) ordered a parameter pair "w-r" (write, read) instead 
of "r-w" (read, write).  When trying to implement of these interfaces I 
consistently got the parameter order backwards (read, write)(1).

The attached patch re-orders the xfer_partial interface so its 
read/write buffers are ordered read/write (i.e., sanely).  I'm doing it 
now before too many things start to depend on the interface.

argh,
Andrew

(1) I also got parameters to pread/pwrite wrong so its a pretty bad day 
all round.