bcache: kill closure locking usage

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/drivers/md/bcache/journal.h b/drivers/md/bcache/journal.h
index a6472fd..9180c44 100644
--- a/drivers/md/bcache/journal.h
+++ b/drivers/md/bcache/journal.h
@@ -104,6 +104,7 @@
 	/* used when waiting because the journal was full */
 	struct closure_waitlist	wait;
 	struct closure		io;
+	int			io_in_flight;
 	struct delayed_work	work;
 
 	/* Number of blocks free in the bucket(s) we're currently writing to */