From 85718972b0046eec54552dd00981628208414f4c Mon Sep 17 00:00:00 2001 From: Peng Zhang Date: Tue, 11 Jul 2023 11:54:37 +0800 Subject: [PATCH] maple_tree: set the node limit when creating a new root node commit 3c769fd88b9742954763a968e84de09f7ad78cfe upstream. Set the node limit of the root node so that the last pivot of all nodes is the node limit (if the node is not full). This patch also fixes a bug in mas_rev_awalk(). Effectively, always setting a maximum makes mas_logical_pivot() behave as mas_safe_pivot(). Without this fix, it is possible that very small tasks would fail to find the correct gap. Although this has not been observed with real tasks, it has been reported to happen in m68k nommu running the maple tree tests. Link: https://lkml.kernel.org/r/20230711035444.526-1-zhangpeng.00@bytedance.com Link: https://lore.kernel.org/linux-mm/CAMuHMdV4T53fOw7VPoBgPR7fP6RYqf=CBhD_y_vOg53zZX_DnA@mail.gmail.com/ Link: https://lkml.kernel.org/r/20230711035444.526-2-zhangpeng.00@bytedance.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Tested-by: Geert Uytterhoeven Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- lib/maple_tree.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/maple_tree.c b/lib/maple_tree.c index 2f1f661157c9..47d0c95b9a01 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -3711,7 +3711,8 @@ static inline int mas_root_expand(struct ma_state *mas, void *entry) mas->offset = slot; pivots[slot] = mas->last; if (mas->last != ULONG_MAX) - slot++; + pivots[++slot] = ULONG_MAX; + mas->depth = 1; mas_set_height(mas); ma_set_meta(node, maple_leaf_64, 0, slot);