maple_tree: adjust node allocation on mas_rebalance()

mas_rebalance() is called to rebalance an insufficient node into a
single node or two sufficient nodes.  The preallocation estimate is
always too many in this case as the height of the tree will never grow
and there is no possibility to have a three way split in this case, so
revise the node allocation count.

Link: https://lkml.kernel.org/r/20230724183157.3939892-9-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 0d7e30c7d9993432ae452ba0ef37b6a3314af419..494f884ef17fc4682f024cab17aface5625b16c9 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3136,7 +3136,7 @@ static inline int mas_rebalance(struct ma_state *mas,
         * tries to combine the data in the same way.  If one node contains the
         * entire range of the tree, then that node is used as a new root node.
         */
-       mas_node_count(mas, 1 + empty_count * 3);
+       mas_node_count(mas, empty_count * 2 - 1);
        if (mas_is_err(mas))
                return 0;