From: Kevin Corry <kevcorry@us.ibm.com>

Some testing of DM multipath has turned up a problem with the DEVICE_WAIT
command.  In the tests, while performing a DEVICE_WAIT on a multipath device,
the command sometimes returns immediately, even though the event-number is
correct and no path-failure has occurred to trigger an event.  The problem was
tracked down to the call to schedule() in dev_wait(), which would return even
though it was not woken up by a DM table event.

This patch moves the responsibility for waiting from the ioctl interface into
the core driver, and uses wait_event_interruptible() instead of relying on
wait-queues and schedule().
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>