staging: lustre: simplify waiting in ldlm_completion_ast()

staging: lustre: simplify waiting in ldlm_completion_ast()

If a signal-callback (lwi_on_signal) is set without lwi_allow_intr, as
is the case in ldlm_completion_ast(), the behavior depends on the
timeout set.

If a timeout is set, then signals are ignored.  If the timeout is
reached, the timeout handler is called.  If the timeout handler
return 0, which ldlm_expired_completion_wait() always does, the
l_wait_event() switches to exactly the behavior if no timeout was set.

If no timeout is set, then "fatal" signals are not ignored.  If one
arrives the callback is run, but as the callback is empty in this
case, that is not relevant.

This can be simplified to:
 if a timeout is wanted
     wait_event_idle_timeout()
     if that timed out, call the timeout handler
 l_wait_event_abortable()

i.e. the code always waits indefinitely.  Sometimes it performs a
non-abortable wait first.  Sometimes it doesn't.  But it only
aborts before the condition is true if it is signaled.
This doesn't quite agree with the comments and debug messages.

Now that we call the timeout handler (ldlm_expired_completion_wait())
wait directly, we can pass the two args directly rather then
using a special-purpose struct.

Reviewed-by: Patrick Farrell <paf@cray.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>