We shouldn't use WB_SYNC_ALL if the caller is asking for asynchronous
treatment.
Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>