From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Subject: radix-tree: remove root->height
The only remaining references to root->height were in extend and shrink,
where it was updated. Now we can remove it entirely.
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 | 3
lib/radix-tree.c | 106 ++++++++++-------------------------
2 files changed, 31 insertions(+), 78 deletions(-)
diff -puN include/linux/radix-tree.h~radix-tree-remove-root-height include/linux/radix-tree.h
--- a/include/linux/radix-tree.h~radix-tree-remove-root-height
+++ a/include/linux/radix-tree.h
@@ -110,13 +110,11 @@ struct radix_tree_node {
/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
struct radix_tree_root {
- unsigned int height;
gfp_t gfp_mask;
struct radix_tree_node __rcu *rnode;
};
#define RADIX_TREE_INIT(mask) { \
- .height = 0, \
.gfp_mask = (mask), \
.rnode = NULL, \
}
@@ -126,7 +124,6 @@ struct radix_tree_root {
#define INIT_RADIX_TREE(root, mask) \
do { \
- (root)->height = 0; \
(root)->gfp_mask = (mask); \
(root)->rnode = NULL; \
} while (0)
diff -puN lib/radix-tree.c~radix-tree-remove-root-height lib/radix-tree.c
--- a/lib/radix-tree.c~radix-tree-remove-root-height
+++ a/lib/radix-tree.c
@@ -39,12 +39,6 @@
/*
- * The height_to_maxindex array needs to be one deeper than the maximum
- * path as height 0 holds only 1 entry.
- */
-static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
-
-/*
* Radix tree node cache.
*/
static struct kmem_cache *radix_tree_node_cachep;
@@ -218,8 +212,7 @@ radix_tree_find_next_bit(const unsigned
}
#ifndef __KERNEL__
-static void dump_node(struct radix_tree_node *node,
- unsigned shift, unsigned long index)
+static void dump_node(struct radix_tree_node *node, unsigned long index)
{
unsigned long i;
@@ -229,8 +222,8 @@ static void dump_node(struct radix_tree_
node->shift, node->count, node->parent);
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
- unsigned long first = index | (i << shift);
- unsigned long last = first | ((1UL << shift) - 1);
+ unsigned long first = index | (i << node->shift);
+ unsigned long last = first | ((1UL << node->shift) - 1);
void *entry = node->slots[i];
if (!entry)
continue;
@@ -243,8 +236,7 @@ static void dump_node(struct radix_tree_
pr_debug("radix entry %p offset %ld indices %ld-%ld\n",
entry, i, first, last);
} else {
- dump_node(indirect_to_ptr(entry),
- shift - RADIX_TREE_MAP_SHIFT, first);
+ dump_node(indirect_to_ptr(entry), first);
}
}
}
@@ -252,13 +244,12 @@ static void dump_node(struct radix_tree_
/* For debug */
static void radix_tree_dump(struct radix_tree_root *root)
{
- pr_debug("radix root: %p height %d rnode %p tags %x\n",
- root, root->height, root->rnode,
+ pr_debug("radix root: %p rnode %p tags %x\n",
+ root, root->rnode,
root->gfp_mask >> __GFP_BITS_SHIFT);
if (!radix_tree_is_indirect_ptr(root->rnode))
return;
- dump_node(indirect_to_ptr(root->rnode),
- (root->height - 1) * RADIX_TREE_MAP_SHIFT, 0);
+ dump_node(indirect_to_ptr(root->rnode), 0);
}
#endif
@@ -411,14 +402,8 @@ int radix_tree_maybe_preload(gfp_t gfp_m
EXPORT_SYMBOL(radix_tree_maybe_preload);
/*
- * Return the maximum key which can be store into a
- * radix tree with height HEIGHT.
+ * The maximum index which can be stored in a radix tree
*/
-static inline unsigned long radix_tree_maxindex(unsigned int height)
-{
- return height_to_maxindex[height];
-}
-
static inline unsigned long shift_maxindex(unsigned int shift)
{
return (RADIX_TREE_MAP_SIZE << shift) - 1;
@@ -450,24 +435,22 @@ static unsigned radix_tree_load_root(str
* Extend a radix tree so it can store key @index.
*/
static int radix_tree_extend(struct radix_tree_root *root,
- unsigned long index)
+ unsigned long index, unsigned int shift)
{
struct radix_tree_node *slot;
- unsigned int height;
+ unsigned int maxshift;
int tag;
- /* Figure out what the height should be. */
- height = root->height + 1;
- while (index > radix_tree_maxindex(height))
- height++;
+ /* Figure out what the shift should be. */
+ maxshift = shift;
+ while (index > shift_maxindex(maxshift))
+ maxshift += RADIX_TREE_MAP_SHIFT;
- if (root->rnode == NULL) {
- root->height = height;
+ slot = root->rnode;
+ if (!slot)
goto out;
- }
do {
- unsigned int newheight;
struct radix_tree_node *node = radix_tree_node_alloc(root);
if (!node)
@@ -479,14 +462,11 @@ static int radix_tree_extend(struct radi
tag_set(node, tag, 0);
}
- /* Increase the height. */
- newheight = root->height;
- BUG_ON(newheight > BITS_PER_LONG);
- node->shift = newheight * RADIX_TREE_MAP_SHIFT;
+ BUG_ON(shift > BITS_PER_LONG);
+ node->shift = shift;
node->offset = 0;
node->count = 1;
node->parent = NULL;
- slot = root->rnode;
if (radix_tree_is_indirect_ptr(slot)) {
slot = indirect_to_ptr(slot);
slot->parent = node;
@@ -495,10 +475,11 @@ 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;
- } while (height > root->height);
+ shift += RADIX_TREE_MAP_SHIFT;
+ slot = node;
+ } while (shift <= maxshift);
out:
- return height * RADIX_TREE_MAP_SHIFT;
+ return maxshift + RADIX_TREE_MAP_SHIFT;
}
/**
@@ -531,15 +512,13 @@ int __radix_tree_create(struct radix_tre
/* Make sure the tree is high enough. */
if (max > maxindex) {
- int error = radix_tree_extend(root, max);
+ int error = radix_tree_extend(root, max, shift);
if (error < 0)
return error;
shift = error;
slot = root->rnode;
- if (order == shift) {
+ if (order == shift)
shift += RADIX_TREE_MAP_SHIFT;
- root->height++;
- }
}
offset = 0; /* uninitialised var warning */
@@ -1412,32 +1391,32 @@ unsigned long radix_tree_locate_item(str
#endif /* CONFIG_SHMEM && CONFIG_SWAP */
/**
- * radix_tree_shrink - shrink height of a radix tree to minimal
+ * radix_tree_shrink - shrink radix tree to minimum height
* @root radix tree root
*/
static inline bool radix_tree_shrink(struct radix_tree_root *root)
{
bool shrunk = false;
- /* try to shrink tree height */
- while (root->height > 0) {
+ for (;;) {
struct radix_tree_node *to_free = root->rnode;
struct radix_tree_node *slot;
- BUG_ON(!radix_tree_is_indirect_ptr(to_free));
+ if (!radix_tree_is_indirect_ptr(to_free))
+ break;
to_free = indirect_to_ptr(to_free);
/*
* The candidate node has more than one child, or its child
- * is not at the leftmost slot, or it is a multiorder entry,
- * we cannot shrink.
+ * is not at the leftmost slot, or the child is a multiorder
+ * entry, we cannot shrink.
*/
if (to_free->count != 1)
break;
slot = to_free->slots[0];
if (!slot)
break;
- if (!radix_tree_is_indirect_ptr(slot) && (root->height > 1))
+ if (!radix_tree_is_indirect_ptr(slot) && to_free->shift)
break;
if (radix_tree_is_indirect_ptr(slot)) {
@@ -1454,7 +1433,6 @@ static inline bool radix_tree_shrink(str
* one (root->rnode) as far as dependent read barriers go.
*/
root->rnode = slot;
- root->height--;
/*
* We have a dilemma here. The node's slot[0] must not be
@@ -1515,7 +1493,6 @@ bool __radix_tree_delete_node(struct rad
parent->count--;
} else {
root_tag_clear_all(root);
- root->height = 0;
root->rnode = NULL;
}
@@ -1631,26 +1608,6 @@ radix_tree_node_ctor(void *arg)
INIT_LIST_HEAD(&node->private_list);
}
-static __init unsigned long __maxindex(unsigned int height)
-{
- unsigned int width = height * RADIX_TREE_MAP_SHIFT;
- int shift = RADIX_TREE_INDEX_BITS - width;
-
- if (shift < 0)
- return ~0UL;
- if (shift >= BITS_PER_LONG)
- return 0UL;
- return ~0UL >> shift;
-}
-
-static __init void radix_tree_init_maxindex(void)
-{
- unsigned int i;
-
- for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
- height_to_maxindex[i] = __maxindex(i);
-}
-
static int radix_tree_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
@@ -1677,6 +1634,5 @@ void __init radix_tree_init(void)
sizeof(struct radix_tree_node), 0,
SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
radix_tree_node_ctor);
- radix_tree_init_maxindex();
hotcpu_notifier(radix_tree_callback, 0);
}
_
--
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