From: Peng Zhang zhangpeng.00@bytedance.com
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_vOg5... 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 zhangpeng.00@bytedance.com Reviewed-by: Liam R. Howlett Liam.Howlett@oracle.com Tested-by: Geert Uytterhoeven geert@linux-m68k.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- lib/maple_tree.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -3711,7 +3711,8 @@ static inline int mas_root_expand(struct 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);