Common i/o layer changes:
 - If a device driver tries to start I/O while the common I/O layer wants
   to start path verification, don't reject the I/O with -EBUSY (which
   might prompt the driver to retry the next tick) but seemingly accept
   the I/O and deliver a fake irb with deferred cc 1 after path
   verification has finished (prompting the driver to retry the I/O).
   This prevents the device driver from doing useless retries while cio
   is still busy with path verification.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>