maple_tree: avoid unnecessary ascending

The maple tree node limits are implied by the parent.  When walking up the
tree, the limit may not be known until a slot that does not have implied
limits are encountered.  However, if the node is the left-most or
right-most node, the walking up to find that limit can be skipped.

This commit also fixes the debug/testing code that was not setting the
limit on walking down the tree as that optimization is not compatible with
this change.

Link: https://lkml.kernel.org/r/20230518145544.1722059-4-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: David Binderman <dcb314@hotmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vernon Yang <vernon2gm@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 0471215e576182fcd8b022670cc03dd96e6e2162..ccd834d624ed77988f34808551b538a645bf3223 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1103,7 +1103,6 @@ static int mas_ascend(struct ma_state *mas)
        enum maple_type a_type;
        unsigned long min, max;
        unsigned long *pivots;
-       unsigned char offset;
        bool set_max = false, set_min = false;
 
        a_node = mas_mn(mas);
@@ -1115,8 +1114,9 @@ static int mas_ascend(struct ma_state *mas)
        p_node = mte_parent(mas->node);
        if (unlikely(a_node == p_node))
                return 1;
+
        a_type = mas_parent_type(mas, mas->node);
-       offset = mte_parent_slot(mas->node);
+       mas->offset = mte_parent_slot(mas->node);
        a_enode = mt_mk_node(p_node, a_type);
 
        /* Check to make sure all parent information is still accurate */
@@ -1124,7 +1124,6 @@ static int mas_ascend(struct ma_state *mas)
                return 1;
 
        mas->node = a_enode;
-       mas->offset = offset;
 
        if (mte_is_root(a_enode)) {
                mas->max = ULONG_MAX;
@@ -1132,6 +1131,12 @@ static int mas_ascend(struct ma_state *mas)
                return 0;
        }
 
+       if (!mas->min)
+               set_min = true;
+
+       if (mas->max == ULONG_MAX)
+               set_max = true;
+
        min = 0;
        max = ULONG_MAX;
        do {

diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index 9286d3baa12d6a9eeadb3050673711ed60d80bc0..75df543e019c95f8fc8f694f5e000f0b1a13cff0 100644 (file)
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -35259,6 +35259,7 @@ static void mas_dfs_preorder(struct ma_state *mas)
 
        struct maple_enode *prev;
        unsigned char end, slot = 0;
+       unsigned long *pivots;
 
        if (mas->node == MAS_START) {
                mas_start(mas);
@@ -35291,6 +35292,9 @@ walk_up:
                mas_ascend(mas);
                goto walk_up;
        }
+       pivots = ma_pivots(mte_to_node(prev), mte_node_type(prev));
+       mas->max = mas_safe_pivot(mas, pivots, slot, mte_node_type(prev));
+       mas->min = mas_safe_min(mas, pivots, slot);
 
        return;
 done: