This cancel_delayed_work call is called from a function that is only called
from a piece of code that immediate follows a cancel and destruction of the
workqueue, so it's clearly a mistake.

Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>