[Libguestfs] [PATCH libnbd] states: In recv_into_rbuf and send_from_wbuf loop until EAGAIN.

I thought this should produce a fairly dramatic performance gain. In fact I couldn't measure any performance difference at all. I think what's happening is we're actually paying an extra syscall (to discover the socket would block) and then doing the poll anyway. So I don't know if it's worth having this patch. It could be argued that it makes the code shorter (therefore simpler), so I'm posting it, but I'm ambivalent. Rich.