From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Subject: radix-tree: replace node->height with node->shift
node->shift represents the shift necessary for looking in the slots array
at this level. It is equal to the old (node->height - 1) *
RADIX_TREE_MAP_SHIFT.
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Cc: Kirill Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/radix-tree.h | 2 +-
lib/radix-tree.c | 30 ++++++++++++++++--------------
2 files changed, 17 insertions(+), 15 deletions(-)
diff -puN include/linux/radix-tree.h~radix-tree-replace-node-height-with-node-shift include/linux/radix-tree.h
--- a/include/linux/radix-tree.h~radix-tree-replace-node-height-with-node-shift
+++ a/include/linux/radix-tree.h
@@ -89,7 +89,7 @@ static inline int radix_tree_is_indirect
#define RADIX_TREE_COUNT_MASK ((1UL << RADIX_TREE_COUNT_SHIFT) - 1)
struct radix_tree_node {
- unsigned char height; /* From the bottom */
+ unsigned char shift; /* Bits remaining in each slot */
unsigned char offset; /* Slot offset in parent */
unsigned int count;
union {
diff -puN lib/radix-tree.c~radix-tree-replace-node-height-with-node-shift lib/radix-tree.c
--- a/lib/radix-tree.c~radix-tree-replace-node-height-with-node-shift
+++ a/lib/radix-tree.c
@@ -223,10 +223,10 @@ static void dump_node(struct radix_tree_
{
unsigned long i;
- pr_debug("radix node: %p offset %d tags %lx %lx %lx height %d count %d parent %p\n",
+ pr_debug("radix node: %p offset %d tags %lx %lx %lx shift %d count %d parent %p\n",
node, node->offset,
node->tags[0][0], node->tags[1][0], node->tags[2][0],
- node->height, node->count, node->parent);
+ node->shift, node->count, node->parent);
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
unsigned long first = index | (i << shift);
@@ -419,9 +419,14 @@ static inline unsigned long radix_tree_m
return height_to_maxindex[height];
}
+static inline unsigned long shift_maxindex(unsigned int shift)
+{
+ return (RADIX_TREE_MAP_SIZE << shift) - 1;
+}
+
static inline unsigned long node_maxindex(struct radix_tree_node *node)
{
- return radix_tree_maxindex(node->height);
+ return shift_maxindex(node->shift);
}
static unsigned radix_tree_load_root(struct radix_tree_root *root,
@@ -434,7 +439,7 @@ static unsigned radix_tree_load_root(str
if (likely(radix_tree_is_indirect_ptr(node))) {
node = indirect_to_ptr(node);
*maxindex = node_maxindex(node);
- return node->height * RADIX_TREE_MAP_SHIFT;
+ return node->shift + RADIX_TREE_MAP_SHIFT;
}
*maxindex = 0;
@@ -475,9 +480,9 @@ static int radix_tree_extend(struct radi
}
/* Increase the height. */
- newheight = root->height + 1;
+ newheight = root->height;
BUG_ON(newheight > BITS_PER_LONG);
- node->height = newheight;
+ node->shift = newheight * RADIX_TREE_MAP_SHIFT;
node->offset = 0;
node->count = 1;
node->parent = NULL;
@@ -490,7 +495,7 @@ static int radix_tree_extend(struct radi
node->slots[0] = slot;
node = ptr_to_indirect(node);
rcu_assign_pointer(root->rnode, node);
- root->height = newheight;
+ root->height = ++newheight;
} while (height > root->height);
out:
return height * RADIX_TREE_MAP_SHIFT;
@@ -519,7 +524,7 @@ int __radix_tree_create(struct radix_tre
{
struct radix_tree_node *node = NULL, *slot;
unsigned long maxindex;
- unsigned int height, shift, offset;
+ unsigned int shift, offset;
unsigned long max = index | ((1UL << order) - 1);
shift = radix_tree_load_root(root, &slot, &maxindex);
@@ -537,16 +542,15 @@ int __radix_tree_create(struct radix_tre
}
}
- height = root->height;
-
offset = 0; /* uninitialised var warning */
while (shift > order) {
+ shift -= RADIX_TREE_MAP_SHIFT;
if (slot == NULL) {
/* Have to add a child node. */
slot = radix_tree_node_alloc(root);
if (!slot)
return -ENOMEM;
- slot->height = height;
+ slot->shift = shift;
slot->offset = offset;
slot->parent = node;
if (node) {
@@ -560,8 +564,6 @@ int __radix_tree_create(struct radix_tre
break;
/* Go a level down */
- height--;
- shift -= RADIX_TREE_MAP_SHIFT;
node = indirect_to_ptr(slot);
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
offset = radix_tree_descend(node, &slot, offset);
@@ -1322,7 +1324,7 @@ static unsigned long __locate(struct rad
unsigned int shift;
unsigned long i;
- shift = slot->height * RADIX_TREE_MAP_SHIFT;
+ shift = slot->shift + RADIX_TREE_MAP_SHIFT;
do {
shift -= RADIX_TREE_MAP_SHIFT;
_
--
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