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maple_tree: use height and depth consistently 

For the maple tree, the root node is defined to have a depth of 0 with a
height of 1.  Each level down from the node, these values are incremented
by 1.  Various code paths define a root with depth 1 which is inconsisent
with the definition.  Modify the code to be consistent with this
definition.

In mas_spanning_rebalance(), l_mas.depth was being used to track the
height based on the number of iterations done in the main loop.  This
information was then used in mas_put_in_tree() to set the height.  Rather
than overload the l_mas.depth field to track height, simply keep track of
height in the local variable new_height and directly pass this to
mas_wmb_replace() which will be passed into mas_put_in_tree().  This
allows up to remove writes to l_mas.depth.

Link: https://lkml.kernel.org/r/20250410191446.2474640-3-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sidhartha Kumar 2025-04-10 19:14:42 +00:00 committed by Andrew Morton
parent 28092a652f
commit f9d3a963fe
2 changed files with 63 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

84
lib/maple_tree.c
View File

@ -211,14 +211,14 @@ static void ma_free_rcu(struct maple_node *node)
call_rcu(&node->rcu, mt_free_rcu);
}
static void mas_set_height(struct ma_state *mas)
static void mt_set_height(struct maple_tree *mt, unsigned char height)
{
unsigned int new_flags = mas->tree->ma_flags;
unsigned int new_flags = mt->ma_flags;
new_flags &= ~MT_FLAGS_HEIGHT_MASK;
MAS_BUG_ON(mas, mas->depth > MAPLE_HEIGHT_MAX);
new_flags |= mas->depth << MT_FLAGS_HEIGHT_OFFSET;
mas->tree->ma_flags = new_flags;
MT_BUG_ON(mt, height > MAPLE_HEIGHT_MAX);
new_flags |= height << MT_FLAGS_HEIGHT_OFFSET;
mt->ma_flags = new_flags;
}
static unsigned int mas_mt_height(struct ma_state *mas)
@ -1371,7 +1371,7 @@ static inline struct maple_enode *mas_start(struct ma_state *mas)
root = mas_root(mas);
/* Tree with nodes */
if (likely(xa_is_node(root))) {
mas->depth = 1;
mas->depth = 0;
mas->status = ma_active;
mas->node = mte_safe_root(root);
mas->offset = 0;
@ -1712,9 +1712,10 @@ static inline void mas_adopt_children(struct ma_state *mas,
* node as dead.
* @mas: the maple state with the new node
* @old_enode: The old maple encoded node to replace.
* @new_height: if we are inserting a root node, update the height of the tree
*/
static inline void mas_put_in_tree(struct ma_state *mas,
struct maple_enode *old_enode)
struct maple_enode *old_enode, char new_height)
__must_hold(mas->tree->ma_lock)
{
unsigned char offset;
@ -1723,7 +1724,7 @@ static inline void mas_put_in_tree(struct ma_state *mas,
if (mte_is_root(mas->node)) {
mas_mn(mas)->parent = ma_parent_ptr(mas_tree_parent(mas));
rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
mas_set_height(mas);
mt_set_height(mas->tree, new_height);
} else {
offset = mte_parent_slot(mas->node);
@ -1741,12 +1742,13 @@ static inline void mas_put_in_tree(struct ma_state *mas,
* the parent encoding to locate the maple node in the tree.
* @mas: the ma_state with @mas->node pointing to the new node.
* @old_enode: The old maple encoded node.
* @new_height: The new height of the tree as a result of the operation
*/
static inline void mas_replace_node(struct ma_state *mas,
struct maple_enode *old_enode)
struct maple_enode *old_enode, unsigned char new_height)
__must_hold(mas->tree->ma_lock)
{
mas_put_in_tree(mas, old_enode);
mas_put_in_tree(mas, old_enode, new_height);
mas_free(mas, old_enode);
}
@ -2536,10 +2538,11 @@ static inline void mas_topiary_node(struct ma_state *mas,
*
* @mas: The maple state pointing at the new data
* @old_enode: The maple encoded node being replaced
* @new_height: The new height of the tree as a result of the operation
*
*/
static inline void mas_topiary_replace(struct ma_state *mas,
struct maple_enode *old_enode)
struct maple_enode *old_enode, unsigned char new_height)
{
struct ma_state tmp[3], tmp_next[3];
MA_TOPIARY(subtrees, mas->tree);
@ -2547,7 +2550,7 @@ static inline void mas_topiary_replace(struct ma_state *mas,
int i, n;
/* Place data in tree & then mark node as old */
mas_put_in_tree(mas, old_enode);
mas_put_in_tree(mas, old_enode, new_height);
/* Update the parent pointers in the tree */
tmp[0] = *mas;
@ -2631,14 +2634,15 @@ static inline void mas_topiary_replace(struct ma_state *mas,
* mas_wmb_replace() - Write memory barrier and replace
* @mas: The maple state
* @old_enode: The old maple encoded node that is being replaced.
* @new_height: The new height of the tree as a result of the operation
*
* Updates gap as necessary.
*/
static inline void mas_wmb_replace(struct ma_state *mas,
struct maple_enode *old_enode)
struct maple_enode *old_enode, unsigned char new_height)
{
/* Insert the new data in the tree */
mas_topiary_replace(mas, old_enode);
mas_topiary_replace(mas, old_enode, new_height);
if (mte_is_leaf(mas->node))
return;
@ -2824,6 +2828,7 @@ static void mas_spanning_rebalance(struct ma_state *mas,
{
unsigned char split, mid_split;
unsigned char slot = 0;
unsigned char new_height = 0; /* used if node is a new root */
struct maple_enode *left = NULL, *middle = NULL, *right = NULL;
struct maple_enode *old_enode;
@ -2845,8 +2850,6 @@ static void mas_spanning_rebalance(struct ma_state *mas,
unlikely(mast->bn->b_end <= mt_min_slots[mast->bn->type]))
mast_spanning_rebalance(mast);
l_mas.depth = 0;
/*
* Each level of the tree is examined and balanced, pushing data to the left or
* right, or rebalancing against left or right nodes is employed to avoid
@ -2866,6 +2869,7 @@ static void mas_spanning_rebalance(struct ma_state *mas,
mast_set_split_parents(mast, left, middle, right, split,
mid_split);
mast_cp_to_nodes(mast, left, middle, right, split, mid_split);
new_height++;
/*
* Copy data from next level in the tree to mast->bn from next
@ -2873,7 +2877,6 @@ static void mas_spanning_rebalance(struct ma_state *mas,
*/
memset(mast->bn, 0, sizeof(struct maple_big_node));
mast->bn->type = mte_node_type(left);
l_mas.depth++;
/* Root already stored in l->node. */
if (mas_is_root_limits(mast->l))
@ -2909,8 +2912,9 @@ static void mas_spanning_rebalance(struct ma_state *mas,
l_mas.node = mt_mk_node(ma_mnode_ptr(mas_pop_node(mas)),
mte_node_type(mast->orig_l->node));
l_mas.depth++;
mab_mas_cp(mast->bn, 0, mt_slots[mast->bn->type] - 1, &l_mas, true);
new_height++;
mas_set_parent(mas, left, l_mas.node, slot);
if (middle)
mas_set_parent(mas, middle, l_mas.node, ++slot);
@ -2933,7 +2937,7 @@ static void mas_spanning_rebalance(struct ma_state *mas,
mas->min = l_mas.min;
mas->max = l_mas.max;
mas->offset = l_mas.offset;
mas_wmb_replace(mas, old_enode);
mas_wmb_replace(mas, old_enode, new_height);
mtree_range_walk(mas);
return;
}
@ -3009,6 +3013,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
void __rcu **l_slots, **slots;
unsigned long *l_pivs, *pivs, gap;
bool in_rcu = mt_in_rcu(mas->tree);
unsigned char new_height = mas_mt_height(mas);
MA_STATE(l_mas, mas->tree, mas->index, mas->last);
@ -3103,7 +3108,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
mas_ascend(mas);
if (in_rcu) {
mas_replace_node(mas, old_eparent);
mas_replace_node(mas, old_eparent, new_height);
mas_adopt_children(mas, mas->node);
}
@ -3114,10 +3119,9 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
* mas_split_final_node() - Split the final node in a subtree operation.
* @mast: the maple subtree state
* @mas: The maple state
* @height: The height of the tree in case it's a new root.
*/
static inline void mas_split_final_node(struct maple_subtree_state *mast,
struct ma_state *mas, int height)
struct ma_state *mas)
{
struct maple_enode *ancestor;
@ -3126,7 +3130,6 @@ static inline void mas_split_final_node(struct maple_subtree_state *mast,
mast->bn->type = maple_arange_64;
else
mast->bn->type = maple_range_64;
mas->depth = height;
}
/*
* Only a single node is used here, could be root.
@ -3214,7 +3217,6 @@ static inline void mast_split_data(struct maple_subtree_state *mast,
* mas_push_data() - Instead of splitting a node, it is beneficial to push the
* data to the right or left node if there is room.
* @mas: The maple state
* @height: The current height of the maple state
* @mast: The maple subtree state
* @left: Push left or not.
*
@ -3222,8 +3224,8 @@ static inline void mast_split_data(struct maple_subtree_state *mast,
*
* Return: True if pushed, false otherwise.
*/
static inline bool mas_push_data(struct ma_state *mas, int height,
struct maple_subtree_state *mast, bool left)
static inline bool mas_push_data(struct ma_state *mas,
struct maple_subtree_state *mast, bool left)
{
unsigned char slot_total = mast->bn->b_end;
unsigned char end, space, split;
@ -3280,7 +3282,7 @@ static inline bool mas_push_data(struct ma_state *mas, int height,
mast_split_data(mast, mas, split);
mast_fill_bnode(mast, mas, 2);
mas_split_final_node(mast, mas, height + 1);
mas_split_final_node(mast, mas);
return true;
}
@ -3293,6 +3295,7 @@ static void mas_split(struct ma_state *mas, struct maple_big_node *b_node)
{
struct maple_subtree_state mast;
int height = 0;
unsigned int orig_height = mas_mt_height(mas);
unsigned char mid_split, split = 0;
struct maple_enode *old;
@ -3319,7 +3322,6 @@ static void mas_split(struct ma_state *mas, struct maple_big_node *b_node)
MA_STATE(prev_r_mas, mas->tree, mas->index, mas->last);
trace_ma_op(__func__, mas);
mas->depth = mas_mt_height(mas);
mast.l = &l_mas;
mast.r = &r_mas;
@ -3327,9 +3329,9 @@ static void mas_split(struct ma_state *mas, struct maple_big_node *b_node)
mast.orig_r = &prev_r_mas;
mast.bn = b_node;
while (height++ <= mas->depth) {
while (height++ <= orig_height) {
if (mt_slots[b_node->type] > b_node->b_end) {
mas_split_final_node(&mast, mas, height);
mas_split_final_node(&mast, mas);
break;
}
@ -3344,11 +3346,15 @@ static void mas_split(struct ma_state *mas, struct maple_big_node *b_node)
* is a significant savings.
*/
/* Try to push left. */
if (mas_push_data(mas, height, &mast, true))
if (mas_push_data(mas, &mast, true)) {
height++;
break;
}
/* Try to push right. */
if (mas_push_data(mas, height, &mast, false))
if (mas_push_data(mas, &mast, false)) {
height++;
break;
}
split = mab_calc_split(mas, b_node, &mid_split);
mast_split_data(&mast, mas, split);
@ -3365,7 +3371,7 @@ static void mas_split(struct ma_state *mas, struct maple_big_node *b_node)
/* Set the original node as dead */
old = mas->node;
mas->node = l_mas.node;
mas_wmb_replace(mas, old);
mas_wmb_replace(mas, old, height);
mtree_range_walk(mas);
return;
}
@ -3424,8 +3430,7 @@ static inline void mas_root_expand(struct ma_state *mas, void *entry)
if (mas->last != ULONG_MAX)
pivots[++slot] = ULONG_MAX;
mas->depth = 1;
mas_set_height(mas);
mt_set_height(mas->tree, 1);
ma_set_meta(node, maple_leaf_64, 0, slot);
/* swap the new root into the tree */
rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
@ -3669,8 +3674,7 @@ static inline void mas_new_root(struct ma_state *mas, void *entry)
WARN_ON_ONCE(mas->index || mas->last != ULONG_MAX);
if (!entry) {
mas->depth = 0;
mas_set_height(mas);
mt_set_height(mas->tree, 0);
rcu_assign_pointer(mas->tree->ma_root, entry);
mas->status = ma_start;
goto done;
@ -3684,8 +3688,7 @@ static inline void mas_new_root(struct ma_state *mas, void *entry)
mas->status = ma_active;
rcu_assign_pointer(slots[0], entry);
pivots[0] = mas->last;
mas->depth = 1;
mas_set_height(mas);
mt_set_height(mas->tree, 1);
rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
done:
@ -3804,6 +3807,7 @@ static inline void mas_wr_node_store(struct ma_wr_state *wr_mas,
struct maple_node reuse, *newnode;
unsigned char copy_size, node_pivots = mt_pivots[wr_mas->type];
bool in_rcu = mt_in_rcu(mas->tree);
unsigned char height = mas_mt_height(mas);
if (mas->last == wr_mas->end_piv)
offset_end++; /* don't copy this offset */
@ -3860,7 +3864,7 @@ static inline void mas_wr_node_store(struct ma_wr_state *wr_mas,
struct maple_enode *old_enode = mas->node;
mas->node = mt_mk_node(newnode, wr_mas->type);
mas_replace_node(mas, old_enode);
mas_replace_node(mas, old_enode, height);
} else {
memcpy(wr_mas->node, newnode, sizeof(struct maple_node));
}

19
tools/testing/radix-tree/maple.c
View File

@ -36248,6 +36248,21 @@ static noinline void __init check_mtree_dup(struct maple_tree *mt)
extern void test_kmem_cache_bulk(void);
static inline void check_spanning_store_height(struct maple_tree *mt)
{
int index = 0;
MA_STATE(mas, mt, 0, 0);
mas_lock(&mas);
while (mt_height(mt) != 3) {
mas_store_gfp(&mas, xa_mk_value(index), GFP_KERNEL);
mas_set(&mas, ++index);
}
mas_set_range(&mas, 90, 140);
mas_store_gfp(&mas, xa_mk_value(index), GFP_KERNEL);
MT_BUG_ON(mt, mas_mt_height(&mas) != 2);
mas_unlock(&mas);
}
/* callback function used for check_nomem_writer_race() */
static void writer2(void *maple_tree)
{
@ -36414,6 +36429,10 @@ void farmer_tests(void)
check_spanning_write(&tree);
mtree_destroy(&tree);
mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);
check_spanning_store_height(&tree);
mtree_destroy(&tree);
mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);
check_null_expand(&tree);
mtree_destroy(&tree);