KNBD server available

[Jeffrey C. Becker]

Hi. I ported Pavel Machek's userland nbd server to run as a kernel module,
and Pavel was kind enough to make it available at his nbd website
(http://atrey.karlin.mff.cuni.cz/~pavel/nbd/nbd.html). Please try it out!

FYI, I ran bonnie to compare knbd to nbd (2 i386's running 2.3.18 kernel
connected by fast ethernet, backing device is /dev/loop0 backed by a large
file). Note knbd is slightly faster on block reads and about 50% faster on
block writes.

Jeff Becker
MRJ Technology Solutions
Numerical Aerospace Simulation Facility
NASA Ames Research Center

----------------------------------------------------------------------
Bonnie Results
              
nbd:

              -------Sequential Output-------- ---Sequential Input--
--Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block---
--Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec
%CPU
          100  2089 25.4  2561  4.9   720  4.5  1018 13.7  1044  5.9  82.4
3.6

knbd:

              -------Sequential Output-------- ---Sequential Input--
--Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block---
--Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec
%CPU
          100  3844 45.6  3888  7.4   577  4.1   781 11.0  1054  6.1  81.1
4.1