Blk-throttle: update to use rbtree with leftmost node cached

As rbtree has native support of caching leftmost node,
i.e. rb_root_cached, no need to do the caching by ourselves.

Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 01d0620a4e4a5e829c9de5c2dec0ac5e0b2b3ab3..db1a3a2ae00617fbe1e4804bbfd327e37ce55737 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -84,8 +84,7 @@ struct throtl_service_queue {
         * RB tree of active children throtl_grp's, which are sorted by
         * their ->disptime.
         */
-       struct rb_root          pending_tree;   /* RB tree of active tgs */
-       struct rb_node          *first_pending; /* first node in the tree */
+       struct rb_root_cached   pending_tree;   /* RB tree of active tgs */
        unsigned int            nr_pending;     /* # queued in the tree */
        unsigned long           first_pending_disptime; /* disptime of the first tg */
        struct timer_list       pending_timer;  /* fires on first_pending_disptime */
@@ -475,7 +474,7 @@ static void throtl_service_queue_init(struct throtl_service_queue *sq)
 {
        INIT_LIST_HEAD(&sq->queued[0]);
        INIT_LIST_HEAD(&sq->queued[1]);
-       sq->pending_tree = RB_ROOT;
+       sq->pending_tree = RB_ROOT_CACHED;
        timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
 }
 
@@ -616,31 +615,23 @@ static void throtl_pd_free(struct blkg_policy_data *pd)
 static struct throtl_grp *
 throtl_rb_first(struct throtl_service_queue *parent_sq)
 {
+       struct rb_node *n;
        /* Service tree is empty */
        if (!parent_sq->nr_pending)
                return NULL;
 
-       if (!parent_sq->first_pending)
-               parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
-
-       if (parent_sq->first_pending)
-               return rb_entry_tg(parent_sq->first_pending);
-
-       return NULL;
-}
-
-static void rb_erase_init(struct rb_node *n, struct rb_root *root)
-{
-       rb_erase(n, root);
-       RB_CLEAR_NODE(n);
+       n = rb_first_cached(&parent_sq->pending_tree);
+       WARN_ON_ONCE(!n);
+       if (!n)
+               return NULL;
+       return rb_entry_tg(n);
 }
 
 static void throtl_rb_erase(struct rb_node *n,
                            struct throtl_service_queue *parent_sq)
 {
-       if (parent_sq->first_pending == n)
-               parent_sq->first_pending = NULL;
-       rb_erase_init(n, &parent_sq->pending_tree);
+       rb_erase_cached(n, &parent_sq->pending_tree);
+       RB_CLEAR_NODE(n);
        --parent_sq->nr_pending;
 }
 
@@ -658,11 +649,11 @@ static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
 static void tg_service_queue_add(struct throtl_grp *tg)
 {
        struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
-       struct rb_node **node = &parent_sq->pending_tree.rb_node;
+       struct rb_node **node = &parent_sq->pending_tree.rb_root.rb_node;
        struct rb_node *parent = NULL;
        struct throtl_grp *__tg;
        unsigned long key = tg->disptime;
-       int left = 1;
+       bool leftmost = true;
 
        while (*node != NULL) {
                parent = *node;
@@ -672,15 +663,13 @@ static void tg_service_queue_add(struct throtl_grp *tg)
                        node = &parent->rb_left;
                else {
                        node = &parent->rb_right;
-                       left = 0;
+                       leftmost = false;
                }
        }
 
-       if (left)
-               parent_sq->first_pending = &tg->rb_node;
-
        rb_link_node(&tg->rb_node, parent, node);
-       rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
+       rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree,
+                              leftmost);
 }
 
 static void __throtl_enqueue_tg(struct throtl_grp *tg)