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radix-tree: remove root->height
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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 <[email protected]>
Reviewed-by: Ross Zwisler <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Kirill Shutemov <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Neil Brown <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@torvalds
Matthew Wilcox authored and torvalds committed May 21, 2016
1 parent 0694f0c commit d089126
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Showing 2 changed files with 31 additions and 78 deletions.
3 changes: 0 additions & 3 deletions include/linux/radix-tree.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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, \
}
Expand All @@ -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)
Expand Down
106 changes: 31 additions & 75 deletions lib/radix-tree.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -38,12 +38,6 @@
#include <linux/preempt.h> /* in_interrupt() */


/*
* 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.
*/
Expand Down Expand Up @@ -218,8 +212,7 @@ radix_tree_find_next_bit(const unsigned long *addr,
}

#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;

Expand All @@ -229,8 +222,8 @@ static void dump_node(struct radix_tree_node *node,
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;
Expand All @@ -243,22 +236,20 @@ static void dump_node(struct radix_tree_node *node,
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);
}
}
}

/* 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

Expand Down Expand Up @@ -411,14 +402,8 @@ int radix_tree_maybe_preload(gfp_t gfp_mask)
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;
Expand Down Expand Up @@ -450,24 +435,22 @@ static unsigned radix_tree_load_root(struct radix_tree_root *root,
* 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)
Expand All @@ -479,14 +462,11 @@ static int radix_tree_extend(struct radix_tree_root *root,
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;
Expand All @@ -495,10 +475,11 @@ static int radix_tree_extend(struct radix_tree_root *root,
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;
}

/**
Expand Down Expand Up @@ -531,15 +512,13 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,

/* 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 */
Expand Down Expand Up @@ -1412,32 +1391,32 @@ unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
#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)) {
Expand All @@ -1454,7 +1433,6 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root)
* 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
Expand Down Expand Up @@ -1515,7 +1493,6 @@ bool __radix_tree_delete_node(struct radix_tree_root *root,
parent->count--;
} else {
root_tag_clear_all(root);
root->height = 0;
root->rnode = NULL;
}

Expand Down Expand Up @@ -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)
{
Expand All @@ -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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