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radix-tree: make radix_tree_descend() more useful
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Now that the shift amount is stored in the node, radix_tree_descend()
can calculate offset itself from index, which removes several lines of
code from each of the tree walkers.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Matthew Wilcox authored and Linus Torvalds committed May 21, 2016
1 parent d604c32 commit 9e85d81
Showing 1 changed file with 26 additions and 52 deletions.
78 changes: 26 additions & 52 deletions lib/radix-tree.c
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Original file line number Diff line number Diff line change
Expand Up @@ -94,9 +94,10 @@ static inline unsigned long get_slot_offset(struct radix_tree_node *parent,
return slot - parent->slots;
}

static unsigned radix_tree_descend(struct radix_tree_node *parent,
struct radix_tree_node **nodep, unsigned offset)
static unsigned int radix_tree_descend(struct radix_tree_node *parent,
struct radix_tree_node **nodep, unsigned long index)
{
unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
void **entry = rcu_dereference_raw(parent->slots[offset]);

#ifdef CONFIG_RADIX_TREE_MULTIORDER
Expand Down Expand Up @@ -536,8 +537,7 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,

/* Go a level down */
node = entry_to_node(child);
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
offset = radix_tree_descend(node, &child, offset);
offset = radix_tree_descend(node, &child, index);
slot = &node->slots[offset];
}

Expand Down Expand Up @@ -625,13 +625,12 @@ void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
unsigned int shift;
void **slot;

restart:
parent = NULL;
slot = (void **)&root->rnode;
shift = radix_tree_load_root(root, &node, &maxindex);
radix_tree_load_root(root, &node, &maxindex);
if (index > maxindex)
return NULL;

Expand All @@ -641,9 +640,7 @@ void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
if (node == RADIX_TREE_RETRY)
goto restart;
parent = entry_to_node(node);
shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
offset = radix_tree_descend(parent, &node, offset);
offset = radix_tree_descend(parent, &node, index);
slot = parent->slots + offset;
}

Expand Down Expand Up @@ -713,19 +710,15 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
unsigned int shift;

shift = radix_tree_load_root(root, &node, &maxindex);
radix_tree_load_root(root, &node, &maxindex);
BUG_ON(index > maxindex);

while (radix_tree_is_internal_node(node)) {
unsigned offset;

shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;

parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, offset);
offset = radix_tree_descend(parent, &node, index);
BUG_ON(!node);

if (!tag_get(parent, tag, offset))
Expand Down Expand Up @@ -779,21 +772,17 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
unsigned int shift;
int uninitialized_var(offset);

shift = radix_tree_load_root(root, &node, &maxindex);
radix_tree_load_root(root, &node, &maxindex);
if (index > maxindex)
return NULL;

parent = NULL;

while (radix_tree_is_internal_node(node)) {
shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;

parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, offset);
offset = radix_tree_descend(parent, &node, index);
}

if (node)
Expand Down Expand Up @@ -823,25 +812,21 @@ int radix_tree_tag_get(struct radix_tree_root *root,
{
struct radix_tree_node *node, *parent;
unsigned long maxindex;
unsigned int shift;

if (!root_tag_get(root, tag))
return 0;

shift = radix_tree_load_root(root, &node, &maxindex);
radix_tree_load_root(root, &node, &maxindex);
if (index > maxindex)
return 0;
if (node == NULL)
return 0;

while (radix_tree_is_internal_node(node)) {
int offset;

shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
unsigned offset;

parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, offset);
offset = radix_tree_descend(parent, &node, index);

if (!node)
return 0;
Expand Down Expand Up @@ -874,7 +859,7 @@ static inline void __set_iter_shift(struct radix_tree_iter *iter,
void **radix_tree_next_chunk(struct radix_tree_root *root,
struct radix_tree_iter *iter, unsigned flags)
{
unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
struct radix_tree_node *node, *child;
unsigned long index, offset, maxindex;

Expand All @@ -895,7 +880,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
return NULL;

restart:
shift = radix_tree_load_root(root, &child, &maxindex);
radix_tree_load_root(root, &child, &maxindex);
if (index > maxindex)
return NULL;
if (!child)
Expand All @@ -912,9 +897,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,

do {
node = entry_to_node(child);
shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
offset = radix_tree_descend(node, &child, offset);
offset = radix_tree_descend(node, &child, index);

if ((flags & RADIX_TREE_ITER_TAGGED) ?
!tag_get(node, tag, offset) : !child) {
Expand All @@ -936,7 +919,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
break;
}
index &= ~node_maxindex(node);
index += offset << shift;
index += offset << node->shift;
/* Overflow after ~0UL */
if (!index)
return NULL;
Expand All @@ -952,7 +935,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
/* Update the iterator state */
iter->index = (index &~ node_maxindex(node)) | (offset << node->shift);
iter->next_index = (index | node_maxindex(node)) + 1;
__set_iter_shift(iter, shift);
__set_iter_shift(iter, node->shift);

/* Construct iter->tags bit-mask from node->tags[tag] array */
if (flags & RADIX_TREE_ITER_TAGGED) {
Expand Down Expand Up @@ -1010,10 +993,10 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
{
struct radix_tree_node *parent, *node, *child;
unsigned long maxindex;
unsigned int shift = radix_tree_load_root(root, &child, &maxindex);
unsigned long tagged = 0;
unsigned long index = *first_indexp;

radix_tree_load_root(root, &child, &maxindex);
last_index = min(last_index, maxindex);
if (index > last_index)
return 0;
Expand All @@ -1030,19 +1013,16 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
}

node = entry_to_node(child);
shift -= RADIX_TREE_MAP_SHIFT;

for (;;) {
unsigned offset = (index >> shift) & RADIX_TREE_MAP_MASK;
offset = radix_tree_descend(node, &child, offset);
unsigned offset = radix_tree_descend(node, &child, index);
if (!child)
goto next;
if (!tag_get(node, iftag, offset))
goto next;
/* Sibling slots never have tags set on them */
if (radix_tree_is_internal_node(child)) {
node = entry_to_node(child);
shift -= RADIX_TREE_MAP_SHIFT;
continue;
}

Expand All @@ -1063,21 +1043,20 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
tag_set(parent, settag, offset);
}
next:
/* Go to next item at level determined by 'shift' */
index = ((index >> shift) + 1) << shift;
/* Go to next entry in node */
index = ((index >> node->shift) + 1) << node->shift;
/* Overflow can happen when last_index is ~0UL... */
if (index > last_index || !index)
break;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
while (offset == 0) {
/*
* We've fully scanned this node. Go up. Because
* last_index is guaranteed to be in the tree, what
* we do below cannot wander astray.
*/
node = node->parent;
shift += RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
}
if (is_sibling_entry(node, node->slots[offset]))
goto next;
Expand Down Expand Up @@ -1275,13 +1254,10 @@ struct locate_info {
static unsigned long __locate(struct radix_tree_node *slot, void *item,
unsigned long index, struct locate_info *info)
{
unsigned int shift;
unsigned long i;

shift = slot->shift + RADIX_TREE_MAP_SHIFT;

do {
shift -= RADIX_TREE_MAP_SHIFT;
unsigned int shift = slot->shift;

for (i = (index >> shift) & RADIX_TREE_MAP_MASK;
i < RADIX_TREE_MAP_SIZE;
Expand All @@ -1304,9 +1280,7 @@ static unsigned long __locate(struct radix_tree_node *slot, void *item,
slot = node;
break;
}
if (i == RADIX_TREE_MAP_SIZE)
break;
} while (shift);
} while (i < RADIX_TREE_MAP_SIZE);

out:
if ((index == 0) && (i == RADIX_TREE_MAP_SIZE))
Expand Down

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