[PATCH v5 1/2] blk-throtl: move WARN_ON_ONCE() from throtl_rb_first() to it's caller

[Yu Kuai]

Prepare to reintroduce tg_drain_bios(), which will iterate until
throtl_rb_first() return NULL.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 block/blk-throttle.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 7c462c006b26..fa3454041def 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -503,7 +503,6 @@ throtl_rb_first(struct throtl_service_queue *parent_sq)
 	struct rb_node *n;
 
 	n = rb_first_cached(&parent_sq->pending_tree);
-	WARN_ON_ONCE(!n);
 	if (!n)
 		return NULL;
 	return rb_entry_tg(n);
@@ -522,7 +521,7 @@ static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
 	struct throtl_grp *tg;
 
 	tg = throtl_rb_first(parent_sq);
-	if (!tg)
+	if (WARN_ON_ONCE(!tg))
 		return;
 
 	parent_sq->first_pending_disptime = tg->disptime;
@@ -1091,7 +1090,7 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
 			break;
 
 		tg = throtl_rb_first(parent_sq);
-		if (!tg)
+		if (WARN_ON_ONCE(!tg))
 			break;
 
 		if (time_before(jiffies, tg->disptime))
-- 
2.31.1