[PATCH 15/17] block, bfq: some cleanups for function bfq_pos_tree_add_move

[Kemeng Shi]

There are three cleanups in this patch:
1. The oom_bfqq is never inserted to tree, so return immediately for
oom_bfqq before unnecessary NULL check of bfqq->pos_root.
2. Only set bfqq->pos_root after bfq_rq_pos_tree_lookup successes rather
than set bfqq->pos_root unconditionally and reset to NULL if
bfq_rq_pos_tree_lookup fails.
3. Remove unnecessary local variable __bfqq which is only used to check
return value of bfq_rq_pos_tree_lookup.

Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
---
 block/bfq-iosched.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index ee02c7502394..6ba096e9aec6 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -783,17 +783,16 @@ void __cold
 bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
 {
 	struct rb_node **p, *parent;
-	struct bfq_queue *__bfqq;
+
+	/* oom_bfqq does not participate in queue merging */
+	if (bfqq == &bfqd->oom_bfqq)
+		return;
 
 	if (bfqq->pos_root) {
 		rb_erase(&bfqq->pos_node, bfqq->pos_root);
 		bfqq->pos_root = NULL;
 	}
 
-	/* oom_bfqq does not participate in queue merging */
-	if (bfqq == &bfqd->oom_bfqq)
-		return;
-
 	/*
 	 * bfqq cannot be merged any longer (see comments in
 	 * bfq_setup_cooperator): no point in adding bfqq into the
@@ -807,14 +806,13 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
 	if (!bfqq->next_rq)
 		return;
 
+	if (bfq_rq_pos_tree_lookup(bfqd, &bfqq_group(bfqq)->rq_pos_tree,
+			blk_rq_pos(bfqq->next_rq), &parent, &p))
+		return;
+
 	bfqq->pos_root = &bfqq_group(bfqq)->rq_pos_tree;
-	__bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root,
-			blk_rq_pos(bfqq->next_rq), &parent, &p);
-	if (!__bfqq) {
-		rb_link_node(&bfqq->pos_node, parent, p);
-		rb_insert_color(&bfqq->pos_node, bfqq->pos_root);
-	} else
-		bfqq->pos_root = NULL;
+	rb_link_node(&bfqq->pos_node, parent, p);
+	rb_insert_color(&bfqq->pos_node, bfqq->pos_root);
 }
 
 /*
-- 
2.30.0