sbitmap: add helpers for add/del wait queue handling

After commit 5d2ee7122c73, users of sbitmap that need wait queue
handling must use the provided helpers. But we only added
prepare_to_wait()/finish_wait() style helpers, add the equivalent
add_wait_queue/list_del wrappers as we..

This is needed to ensure kyber plays by the sbitmap waitqueue
rules.

Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 03f50fc..14d5581 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -560,13 +560,13 @@
 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m);
 
 struct sbq_wait {
-	int accounted;
+	struct sbitmap_queue *sbq;	/* if set, sbq_wait is accounted */
 	struct wait_queue_entry wait;
 };
 
 #define DEFINE_SBQ_WAIT(name)							\
 	struct sbq_wait name = {						\
-		.accounted = 0,							\
+		.sbq = NULL,							\
 		.wait = {							\
 			.private	= current,				\
 			.func		= autoremove_wake_function,		\
@@ -588,4 +588,16 @@
 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
 				struct sbq_wait *sbq_wait);
 
+/*
+ * Wrapper around add_wait_queue(), which maintains some extra internal state
+ */
+void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
+			    struct sbq_wait_state *ws,
+			    struct sbq_wait *sbq_wait);
+
+/*
+ * Must be paired with sbitmap_add_wait_queue()
+ */
+void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait);
+
 #endif /* __LINUX_SCALE_BITMAP_H */