/*
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
- * Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
+ * Copyright (C) 2005 SGI, Christoph Lameter
+ * Copyright (C) 2006 Nick Piggin
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
#include <linux/slab.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
-#include <linux/gfp.h>
#include <linux/string.h>
#include <linux/bitops.h>
+#include <linux/rcupdate.h>
#ifdef __KERNEL__
((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
struct radix_tree_node {
+ unsigned int height; /* Height from the bottom */
unsigned int count;
- void *slots[RADIX_TREE_MAP_SIZE];
+ struct rcu_head rcu_head;
+ void __rcu *slots[RADIX_TREE_MAP_SIZE];
unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
};
};
#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
-#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
+#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
+ RADIX_TREE_MAP_SHIFT))
-static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;
+/*
+ * 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 kmem_cache_t *radix_tree_node_cachep;
+static struct kmem_cache *radix_tree_node_cachep;
/*
* Per-cpu pool of preloaded nodes
int nr;
struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
};
-DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
+static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
+
+static inline void *ptr_to_indirect(void *ptr)
+{
+ return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
+}
+
+static inline void *indirect_to_ptr(void *ptr)
+{
+ return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
+}
static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
{
return root->gfp_mask & __GFP_BITS_MASK;
}
+static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
+ int offset)
+{
+ __set_bit(offset, node->tags[tag]);
+}
+
+static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
+ int offset)
+{
+ __clear_bit(offset, node->tags[tag]);
+}
+
+static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
+ int offset)
+{
+ return test_bit(offset, node->tags[tag]);
+}
+
+static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
+{
+ root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
+}
+
+static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
+{
+ root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
+}
+
+static inline void root_tag_clear_all(struct radix_tree_root *root)
+{
+ root->gfp_mask &= __GFP_BITS_MASK;
+}
+
+static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
+{
+ return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
+}
+
+/*
+ * Returns 1 if any slot in the node has this tag set.
+ * Otherwise returns 0.
+ */
+static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
+{
+ int idx;
+ for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
+ if (node->tags[tag][idx])
+ return 1;
+ }
+ return 0;
+}
/*
* This assumes that the caller has performed appropriate preallocation, and
* that the caller has pinned this thread of control to the current CPU.
static struct radix_tree_node *
radix_tree_node_alloc(struct radix_tree_root *root)
{
- struct radix_tree_node *ret;
+ struct radix_tree_node *ret = NULL;
gfp_t gfp_mask = root_gfp_mask(root);
- ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
- if (ret == NULL && !(gfp_mask & __GFP_WAIT)) {
+ if (!(gfp_mask & __GFP_WAIT)) {
struct radix_tree_preload *rtp;
+ /*
+ * Provided the caller has preloaded here, we will always
+ * succeed in getting a node here (and never reach
+ * kmem_cache_alloc)
+ */
rtp = &__get_cpu_var(radix_tree_preloads);
if (rtp->nr) {
ret = rtp->nodes[rtp->nr - 1];
rtp->nr--;
}
}
+ if (ret == NULL)
+ ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
+
+ BUG_ON(radix_tree_is_indirect_ptr(ret));
return ret;
}
+static void radix_tree_node_rcu_free(struct rcu_head *head)
+{
+ struct radix_tree_node *node =
+ container_of(head, struct radix_tree_node, rcu_head);
+ int i;
+
+ /*
+ * must only free zeroed nodes into the slab. radix_tree_shrink
+ * can leave us with a non-NULL entry in the first slot, so clear
+ * that here to make sure.
+ */
+ for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
+ tag_clear(node, i, 0);
+
+ node->slots[0] = NULL;
+ node->count = 0;
+
+ kmem_cache_free(radix_tree_node_cachep, node);
+}
+
static inline void
radix_tree_node_free(struct radix_tree_node *node)
{
- kmem_cache_free(radix_tree_node_cachep, node);
+ call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
}
/*
* ensure that the addition of a single element in the tree cannot fail. On
* success, return zero, with preemption disabled. On error, return -ENOMEM
* with preemption not disabled.
+ *
+ * To make use of this facility, the radix tree must be initialised without
+ * __GFP_WAIT being passed to INIT_RADIX_TREE().
*/
int radix_tree_preload(gfp_t gfp_mask)
{
out:
return ret;
}
-
-static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
- int offset)
-{
- __set_bit(offset, node->tags[tag]);
-}
-
-static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
- int offset)
-{
- __clear_bit(offset, node->tags[tag]);
-}
-
-static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
- int offset)
-{
- return test_bit(offset, node->tags[tag]);
-}
-
-static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
-{
- root->gfp_mask |= (1 << (tag + __GFP_BITS_SHIFT));
-}
-
-
-static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
-{
- root->gfp_mask &= ~(1 << (tag + __GFP_BITS_SHIFT));
-}
-
-static inline void root_tag_clear_all(struct radix_tree_root *root)
-{
- root->gfp_mask &= __GFP_BITS_MASK;
-}
-
-static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
-{
- return root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
-}
-
-/*
- * Returns 1 if any slot in the node has this tag set.
- * Otherwise returns 0.
- */
-static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
-{
- int idx;
- for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
- if (node->tags[tag][idx])
- return 1;
- }
- return 0;
-}
+EXPORT_SYMBOL(radix_tree_preload);
/*
* Return the maximum key which can be store into a
}
do {
+ unsigned int newheight;
if (!(node = radix_tree_node_alloc(root)))
return -ENOMEM;
/* Increase the height. */
- node->slots[0] = root->rnode;
+ node->slots[0] = indirect_to_ptr(root->rnode);
/* Propagate the aggregated tag info into the new root */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
tag_set(node, tag, 0);
}
+ newheight = root->height+1;
+ node->height = newheight;
node->count = 1;
- root->rnode = node;
- root->height++;
+ node = ptr_to_indirect(node);
+ rcu_assign_pointer(root->rnode, node);
+ root->height = newheight;
} while (height > root->height);
out:
return 0;
int offset;
int error;
+ BUG_ON(radix_tree_is_indirect_ptr(item));
+
/* Make sure the tree is high enough. */
if (index > radix_tree_maxindex(root->height)) {
error = radix_tree_extend(root, index);
return error;
}
- slot = root->rnode;
+ slot = indirect_to_ptr(root->rnode);
+
height = root->height;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
/* Have to add a child node. */
if (!(slot = radix_tree_node_alloc(root)))
return -ENOMEM;
+ slot->height = height;
if (node) {
- node->slots[offset] = slot;
+ rcu_assign_pointer(node->slots[offset], slot);
node->count++;
} else
- root->rnode = slot;
+ rcu_assign_pointer(root->rnode, ptr_to_indirect(slot));
}
/* Go a level down */
if (node) {
node->count++;
- node->slots[offset] = item;
+ rcu_assign_pointer(node->slots[offset], item);
BUG_ON(tag_get(node, 0, offset));
BUG_ON(tag_get(node, 1, offset));
} else {
- root->rnode = item;
+ rcu_assign_pointer(root->rnode, item);
BUG_ON(root_tag_get(root, 0));
BUG_ON(root_tag_get(root, 1));
}
}
EXPORT_SYMBOL(radix_tree_insert);
-static inline void **__lookup_slot(struct radix_tree_root *root,
- unsigned long index)
+/*
+ * is_slot == 1 : search for the slot.
+ * is_slot == 0 : search for the node.
+ */
+static void *radix_tree_lookup_element(struct radix_tree_root *root,
+ unsigned long index, int is_slot)
{
unsigned int height, shift;
- struct radix_tree_node **slot;
+ struct radix_tree_node *node, **slot;
- height = root->height;
+ node = rcu_dereference_raw(root->rnode);
+ if (node == NULL)
+ return NULL;
+
+ if (!radix_tree_is_indirect_ptr(node)) {
+ if (index > 0)
+ return NULL;
+ return is_slot ? (void *)&root->rnode : node;
+ }
+ node = indirect_to_ptr(node);
+ height = node->height;
if (index > radix_tree_maxindex(height))
return NULL;
- if (height == 0 && root->rnode)
- return (void **)&root->rnode;
-
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
- slot = &root->rnode;
- while (height > 0) {
- if (*slot == NULL)
+ do {
+ slot = (struct radix_tree_node **)
+ (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
+ node = rcu_dereference_raw(*slot);
+ if (node == NULL)
return NULL;
- slot = (struct radix_tree_node **)
- ((*slot)->slots +
- ((index >> shift) & RADIX_TREE_MAP_MASK));
shift -= RADIX_TREE_MAP_SHIFT;
height--;
- }
+ } while (height > 0);
- return (void **)slot;
+ return is_slot ? (void *)slot : indirect_to_ptr(node);
}
/**
* @root: radix tree root
* @index: index key
*
- * Lookup the slot corresponding to the position @index in the radix tree
- * @root. This is useful for update-if-exists operations.
+ * Returns: the slot corresponding to the position @index in the
+ * radix tree @root. This is useful for update-if-exists operations.
+ *
+ * This function can be called under rcu_read_lock iff the slot is not
+ * modified by radix_tree_replace_slot, otherwise it must be called
+ * exclusive from other writers. Any dereference of the slot must be done
+ * using radix_tree_deref_slot.
*/
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
- return __lookup_slot(root, index);
+ return (void **)radix_tree_lookup_element(root, index, 1);
}
EXPORT_SYMBOL(radix_tree_lookup_slot);
* @index: index key
*
* Lookup the item at the position @index in the radix tree @root.
+ *
+ * This function can be called under rcu_read_lock, however the caller
+ * must manage lifetimes of leaf nodes (eg. RCU may also be used to free
+ * them safely). No RCU barriers are required to access or modify the
+ * returned item, however.
*/
void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
- void **slot;
-
- slot = __lookup_slot(root, index);
- return slot != NULL ? *slot : NULL;
+ return radix_tree_lookup_element(root, index, 0);
}
EXPORT_SYMBOL(radix_tree_lookup);
height = root->height;
BUG_ON(index > radix_tree_maxindex(height));
- slot = root->rnode;
+ slot = indirect_to_ptr(root->rnode);
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
while (height > 0) {
void *radix_tree_tag_clear(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
- struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+ /*
+ * The radix tree path needs to be one longer than the maximum path
+ * since the "list" is null terminated.
+ */
+ struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
struct radix_tree_node *slot = NULL;
unsigned int height, shift;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
pathp->node = NULL;
- slot = root->rnode;
+ slot = indirect_to_ptr(root->rnode);
while (height > 0) {
int offset;
}
EXPORT_SYMBOL(radix_tree_tag_clear);
-#ifndef __KERNEL__ /* Only the test harness uses this at present */
/**
* radix_tree_tag_get - get a tag on a radix tree node
* @root: radix tree root
*
* 0: tag not present or not set
* 1: tag set
+ *
+ * Note that the return value of this function may not be relied on, even if
+ * the RCU lock is held, unless tag modification and node deletion are excluded
+ * from concurrency.
*/
int radix_tree_tag_get(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
unsigned int height, shift;
- struct radix_tree_node *slot;
+ struct radix_tree_node *node;
int saw_unset_tag = 0;
- height = root->height;
- if (index > radix_tree_maxindex(height))
- return 0;
-
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
- if (height == 0)
- return 1;
+ node = rcu_dereference_raw(root->rnode);
+ if (node == NULL)
+ return 0;
+
+ if (!radix_tree_is_indirect_ptr(node))
+ return (index == 0);
+ node = indirect_to_ptr(node);
+
+ height = node->height;
+ if (index > radix_tree_maxindex(height))
+ return 0;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
- slot = root->rnode;
for ( ; ; ) {
int offset;
- if (slot == NULL)
+ if (node == NULL)
return 0;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
* This is just a debug check. Later, we can bale as soon as
* we see an unset tag.
*/
- if (!tag_get(slot, tag, offset))
+ if (!tag_get(node, tag, offset))
saw_unset_tag = 1;
- if (height == 1) {
- int ret = tag_get(slot, tag, offset);
-
- BUG_ON(ret && saw_unset_tag);
- return !!ret;
- }
- slot = slot->slots[offset];
+ if (height == 1)
+ return !!tag_get(node, tag, offset);
+ node = rcu_dereference_raw(node->slots[offset]);
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
}
EXPORT_SYMBOL(radix_tree_tag_get);
-#endif
+
+/**
+ * radix_tree_range_tag_if_tagged - for each item in given range set given
+ * tag if item has another tag set
+ * @root: radix tree root
+ * @first_indexp: pointer to a starting index of a range to scan
+ * @last_index: last index of a range to scan
+ * @nr_to_tag: maximum number items to tag
+ * @iftag: tag index to test
+ * @settag: tag index to set if tested tag is set
+ *
+ * This function scans range of radix tree from first_index to last_index
+ * (inclusive). For each item in the range if iftag is set, the function sets
+ * also settag. The function stops either after tagging nr_to_tag items or
+ * after reaching last_index.
+ *
+ * The tags must be set from the leaf level only and propagated back up the
+ * path to the root. We must do this so that we resolve the full path before
+ * setting any tags on intermediate nodes. If we set tags as we descend, then
+ * we can get to the leaf node and find that the index that has the iftag
+ * set is outside the range we are scanning. This reults in dangling tags and
+ * can lead to problems with later tag operations (e.g. livelocks on lookups).
+ *
+ * The function returns number of leaves where the tag was set and sets
+ * *first_indexp to the first unscanned index.
+ * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
+ * be prepared to handle that.
+ */
+unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
+ unsigned long *first_indexp, unsigned long last_index,
+ unsigned long nr_to_tag,
+ unsigned int iftag, unsigned int settag)
+{
+ unsigned int height = root->height;
+ struct radix_tree_path path[height];
+ struct radix_tree_path *pathp = path;
+ struct radix_tree_node *slot;
+ unsigned int shift;
+ unsigned long tagged = 0;
+ unsigned long index = *first_indexp;
+
+ last_index = min(last_index, radix_tree_maxindex(height));
+ if (index > last_index)
+ return 0;
+ if (!nr_to_tag)
+ return 0;
+ if (!root_tag_get(root, iftag)) {
+ *first_indexp = last_index + 1;
+ return 0;
+ }
+ if (height == 0) {
+ *first_indexp = last_index + 1;
+ root_tag_set(root, settag);
+ return 1;
+ }
+
+ shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+ slot = indirect_to_ptr(root->rnode);
+
+ /*
+ * we fill the path from (root->height - 2) to 0, leaving the index at
+ * (root->height - 1) as a terminator. Zero the node in the terminator
+ * so that we can use this to end walk loops back up the path.
+ */
+ path[height - 1].node = NULL;
+
+ for (;;) {
+ int offset;
+
+ offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+ if (!slot->slots[offset])
+ goto next;
+ if (!tag_get(slot, iftag, offset))
+ goto next;
+ if (height > 1) {
+ /* Go down one level */
+ height--;
+ shift -= RADIX_TREE_MAP_SHIFT;
+ path[height - 1].node = slot;
+ path[height - 1].offset = offset;
+ slot = slot->slots[offset];
+ continue;
+ }
+
+ /* tag the leaf */
+ tagged++;
+ tag_set(slot, settag, offset);
+
+ /* walk back up the path tagging interior nodes */
+ pathp = &path[0];
+ while (pathp->node) {
+ /* stop if we find a node with the tag already set */
+ if (tag_get(pathp->node, settag, pathp->offset))
+ break;
+ tag_set(pathp->node, settag, pathp->offset);
+ pathp++;
+ }
+
+next:
+ /* Go to next item at level determined by 'shift' */
+ index = ((index >> shift) + 1) << shift;
+ /* Overflow can happen when last_index is ~0UL... */
+ if (index > last_index || !index)
+ break;
+ if (tagged >= nr_to_tag)
+ break;
+ while (((index >> shift) & RADIX_TREE_MAP_MASK) == 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.
+ */
+ slot = path[height - 1].node;
+ height++;
+ shift += RADIX_TREE_MAP_SHIFT;
+ }
+ }
+ /*
+ * We need not to tag the root tag if there is no tag which is set with
+ * settag within the range from *first_indexp to last_index.
+ */
+ if (tagged > 0)
+ root_tag_set(root, settag);
+ *first_indexp = index;
+
+ return tagged;
+}
+EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
+
+
+/**
+ * radix_tree_next_hole - find the next hole (not-present entry)
+ * @root: tree root
+ * @index: index key
+ * @max_scan: maximum range to search
+ *
+ * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
+ * indexed hole.
+ *
+ * Returns: the index of the hole if found, otherwise returns an index
+ * outside of the set specified (in which case 'return - index >= max_scan'
+ * will be true). In rare cases of index wrap-around, 0 will be returned.
+ *
+ * radix_tree_next_hole may be called under rcu_read_lock. However, like
+ * radix_tree_gang_lookup, this will not atomically search a snapshot of
+ * the tree at a single point in time. For example, if a hole is created
+ * at index 5, then subsequently a hole is created at index 10,
+ * radix_tree_next_hole covering both indexes may return 10 if called
+ * under rcu_read_lock.
+ */
+unsigned long radix_tree_next_hole(struct radix_tree_root *root,
+ unsigned long index, unsigned long max_scan)
+{
+ unsigned long i;
+
+ for (i = 0; i < max_scan; i++) {
+ if (!radix_tree_lookup(root, index))
+ break;
+ index++;
+ if (index == 0)
+ break;
+ }
+
+ return index;
+}
+EXPORT_SYMBOL(radix_tree_next_hole);
+
+/**
+ * radix_tree_prev_hole - find the prev hole (not-present entry)
+ * @root: tree root
+ * @index: index key
+ * @max_scan: maximum range to search
+ *
+ * Search backwards in the range [max(index-max_scan+1, 0), index]
+ * for the first hole.
+ *
+ * Returns: the index of the hole if found, otherwise returns an index
+ * outside of the set specified (in which case 'index - return >= max_scan'
+ * will be true). In rare cases of wrap-around, ULONG_MAX will be returned.
+ *
+ * radix_tree_next_hole may be called under rcu_read_lock. However, like
+ * radix_tree_gang_lookup, this will not atomically search a snapshot of
+ * the tree at a single point in time. For example, if a hole is created
+ * at index 10, then subsequently a hole is created at index 5,
+ * radix_tree_prev_hole covering both indexes may return 5 if called under
+ * rcu_read_lock.
+ */
+unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
+ unsigned long index, unsigned long max_scan)
+{
+ unsigned long i;
+
+ for (i = 0; i < max_scan; i++) {
+ if (!radix_tree_lookup(root, index))
+ break;
+ index--;
+ if (index == ULONG_MAX)
+ break;
+ }
+
+ return index;
+}
+EXPORT_SYMBOL(radix_tree_prev_hole);
static unsigned int
-__lookup(struct radix_tree_root *root, void **results, unsigned long index,
+__lookup(struct radix_tree_node *slot, void ***results, unsigned long index,
unsigned int max_items, unsigned long *next_index)
{
unsigned int nr_found = 0;
unsigned int shift, height;
- struct radix_tree_node *slot;
unsigned long i;
- height = root->height;
- if (height == 0) {
- if (root->rnode && index == 0)
- results[nr_found++] = root->rnode;
+ height = slot->height;
+ if (height == 0)
goto out;
- }
-
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
- slot = root->rnode;
for ( ; height > 1; height--) {
-
- for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
- i < RADIX_TREE_MAP_SIZE; i++) {
+ i = (index >> shift) & RADIX_TREE_MAP_MASK;
+ for (;;) {
if (slot->slots[i] != NULL)
break;
index &= ~((1UL << shift) - 1);
index += 1UL << shift;
if (index == 0)
goto out; /* 32-bit wraparound */
+ i++;
+ if (i == RADIX_TREE_MAP_SIZE)
+ goto out;
}
- if (i == RADIX_TREE_MAP_SIZE)
- goto out;
shift -= RADIX_TREE_MAP_SHIFT;
- slot = slot->slots[i];
+ slot = rcu_dereference_raw(slot->slots[i]);
+ if (slot == NULL)
+ goto out;
}
/* Bottom level: grab some items */
for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
index++;
if (slot->slots[i]) {
- results[nr_found++] = slot->slots[i];
+ results[nr_found++] = &(slot->slots[i]);
if (nr_found == max_items)
goto out;
}
* *@results.
*
* The implementation is naive.
+ *
+ * Like radix_tree_lookup, radix_tree_gang_lookup may be called under
+ * rcu_read_lock. In this case, rather than the returned results being
+ * an atomic snapshot of the tree at a single point in time, the semantics
+ * of an RCU protected gang lookup are as though multiple radix_tree_lookups
+ * have been issued in individual locks, and results stored in 'results'.
*/
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items)
{
- const unsigned long max_index = radix_tree_maxindex(root->height);
+ unsigned long max_index;
+ struct radix_tree_node *node;
unsigned long cur_index = first_index;
- unsigned int ret = 0;
+ unsigned int ret;
+
+ node = rcu_dereference_raw(root->rnode);
+ if (!node)
+ return 0;
+
+ if (!radix_tree_is_indirect_ptr(node)) {
+ if (first_index > 0)
+ return 0;
+ results[0] = node;
+ return 1;
+ }
+ node = indirect_to_ptr(node);
+
+ max_index = radix_tree_maxindex(node->height);
+ ret = 0;
while (ret < max_items) {
- unsigned int nr_found;
+ unsigned int nr_found, slots_found, i;
unsigned long next_index; /* Index of next search */
if (cur_index > max_index)
break;
- nr_found = __lookup(root, results + ret, cur_index,
+ slots_found = __lookup(node, (void ***)results + ret, cur_index,
max_items - ret, &next_index);
+ nr_found = 0;
+ for (i = 0; i < slots_found; i++) {
+ struct radix_tree_node *slot;
+ slot = *(((void ***)results)[ret + i]);
+ if (!slot)
+ continue;
+ results[ret + nr_found] =
+ indirect_to_ptr(rcu_dereference_raw(slot));
+ nr_found++;
+ }
ret += nr_found;
if (next_index == 0)
break;
cur_index = next_index;
}
+
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup);
+/**
+ * radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
+ * @root: radix tree root
+ * @results: where the results of the lookup are placed
+ * @first_index: start the lookup from this key
+ * @max_items: place up to this many items at *results
+ *
+ * Performs an index-ascending scan of the tree for present items. Places
+ * their slots at *@results and returns the number of items which were
+ * placed at *@results.
+ *
+ * The implementation is naive.
+ *
+ * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
+ * be dereferenced with radix_tree_deref_slot, and if using only RCU
+ * protection, radix_tree_deref_slot may fail requiring a retry.
+ */
+unsigned int
+radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results,
+ unsigned long first_index, unsigned int max_items)
+{
+ unsigned long max_index;
+ struct radix_tree_node *node;
+ unsigned long cur_index = first_index;
+ unsigned int ret;
+
+ node = rcu_dereference_raw(root->rnode);
+ if (!node)
+ return 0;
+
+ if (!radix_tree_is_indirect_ptr(node)) {
+ if (first_index > 0)
+ return 0;
+ results[0] = (void **)&root->rnode;
+ return 1;
+ }
+ node = indirect_to_ptr(node);
+
+ max_index = radix_tree_maxindex(node->height);
+
+ ret = 0;
+ while (ret < max_items) {
+ unsigned int slots_found;
+ unsigned long next_index; /* Index of next search */
+
+ if (cur_index > max_index)
+ break;
+ slots_found = __lookup(node, results + ret, cur_index,
+ max_items - ret, &next_index);
+ ret += slots_found;
+ if (next_index == 0)
+ break;
+ cur_index = next_index;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
+
/*
* FIXME: the two tag_get()s here should use find_next_bit() instead of
* open-coding the search.
*/
static unsigned int
-__lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
+__lookup_tag(struct radix_tree_node *slot, void ***results, unsigned long index,
unsigned int max_items, unsigned long *next_index, unsigned int tag)
{
unsigned int nr_found = 0;
- unsigned int shift;
- unsigned int height = root->height;
- struct radix_tree_node *slot;
+ unsigned int shift, height;
- if (height == 0) {
- if (root->rnode && index == 0)
- results[nr_found++] = root->rnode;
+ height = slot->height;
+ if (height == 0)
goto out;
- }
-
- shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
- slot = root->rnode;
+ shift = (height-1) * RADIX_TREE_MAP_SHIFT;
- do {
- unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
+ while (height > 0) {
+ unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
- for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
- if (tag_get(slot, tag, i)) {
- BUG_ON(slot->slots[i] == NULL);
+ for (;;) {
+ if (tag_get(slot, tag, i))
break;
- }
index &= ~((1UL << shift) - 1);
index += 1UL << shift;
if (index == 0)
goto out; /* 32-bit wraparound */
+ i++;
+ if (i == RADIX_TREE_MAP_SIZE)
+ goto out;
}
- if (i == RADIX_TREE_MAP_SIZE)
- goto out;
height--;
if (height == 0) { /* Bottom level: grab some items */
unsigned long j = index & RADIX_TREE_MAP_MASK;
for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
index++;
- if (tag_get(slot, tag, j)) {
- BUG_ON(slot->slots[j] == NULL);
- results[nr_found++] = slot->slots[j];
+ if (!tag_get(slot, tag, j))
+ continue;
+ /*
+ * Even though the tag was found set, we need to
+ * recheck that we have a non-NULL node, because
+ * if this lookup is lockless, it may have been
+ * subsequently deleted.
+ *
+ * Similar care must be taken in any place that
+ * lookup ->slots[x] without a lock (ie. can't
+ * rely on its value remaining the same).
+ */
+ if (slot->slots[j]) {
+ results[nr_found++] = &(slot->slots[j]);
if (nr_found == max_items)
goto out;
}
}
}
shift -= RADIX_TREE_MAP_SHIFT;
- slot = slot->slots[i];
- } while (height > 0);
+ slot = rcu_dereference_raw(slot->slots[i]);
+ if (slot == NULL)
+ break;
+ }
out:
*next_index = index;
return nr_found;
unsigned long first_index, unsigned int max_items,
unsigned int tag)
{
- const unsigned long max_index = radix_tree_maxindex(root->height);
+ struct radix_tree_node *node;
+ unsigned long max_index;
unsigned long cur_index = first_index;
- unsigned int ret = 0;
+ unsigned int ret;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
+ node = rcu_dereference_raw(root->rnode);
+ if (!node)
+ return 0;
+
+ if (!radix_tree_is_indirect_ptr(node)) {
+ if (first_index > 0)
+ return 0;
+ results[0] = node;
+ return 1;
+ }
+ node = indirect_to_ptr(node);
+
+ max_index = radix_tree_maxindex(node->height);
+
+ ret = 0;
while (ret < max_items) {
- unsigned int nr_found;
+ unsigned int nr_found, slots_found, i;
unsigned long next_index; /* Index of next search */
if (cur_index > max_index)
break;
- nr_found = __lookup_tag(root, results + ret, cur_index,
- max_items - ret, &next_index, tag);
+ slots_found = __lookup_tag(node, (void ***)results + ret,
+ cur_index, max_items - ret, &next_index, tag);
+ nr_found = 0;
+ for (i = 0; i < slots_found; i++) {
+ struct radix_tree_node *slot;
+ slot = *(((void ***)results)[ret + i]);
+ if (!slot)
+ continue;
+ results[ret + nr_found] =
+ indirect_to_ptr(rcu_dereference_raw(slot));
+ nr_found++;
+ }
ret += nr_found;
if (next_index == 0)
break;
cur_index = next_index;
}
+
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
+/**
+ * radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
+ * radix tree based on a tag
+ * @root: radix tree root
+ * @results: where the results of the lookup are placed
+ * @first_index: start the lookup from this key
+ * @max_items: place up to this many items at *results
+ * @tag: the tag index (< RADIX_TREE_MAX_TAGS)
+ *
+ * Performs an index-ascending scan of the tree for present items which
+ * have the tag indexed by @tag set. Places the slots at *@results and
+ * returns the number of slots which were placed at *@results.
+ */
+unsigned int
+radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
+ unsigned long first_index, unsigned int max_items,
+ unsigned int tag)
+{
+ struct radix_tree_node *node;
+ unsigned long max_index;
+ unsigned long cur_index = first_index;
+ unsigned int ret;
+
+ /* check the root's tag bit */
+ if (!root_tag_get(root, tag))
+ return 0;
+
+ node = rcu_dereference_raw(root->rnode);
+ if (!node)
+ return 0;
+
+ if (!radix_tree_is_indirect_ptr(node)) {
+ if (first_index > 0)
+ return 0;
+ results[0] = (void **)&root->rnode;
+ return 1;
+ }
+ node = indirect_to_ptr(node);
+
+ max_index = radix_tree_maxindex(node->height);
+
+ ret = 0;
+ while (ret < max_items) {
+ unsigned int slots_found;
+ unsigned long next_index; /* Index of next search */
+
+ if (cur_index > max_index)
+ break;
+ slots_found = __lookup_tag(node, results + ret,
+ cur_index, max_items - ret, &next_index, tag);
+ ret += slots_found;
+ if (next_index == 0)
+ break;
+ cur_index = next_index;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
+
+
/**
* radix_tree_shrink - shrink height of a radix tree to minimal
* @root radix tree root
static inline void radix_tree_shrink(struct radix_tree_root *root)
{
/* try to shrink tree height */
- while (root->height > 0 &&
- root->rnode->count == 1 &&
- root->rnode->slots[0]) {
+ while (root->height > 0) {
struct radix_tree_node *to_free = root->rnode;
+ void *newptr;
+
+ BUG_ON(!radix_tree_is_indirect_ptr(to_free));
+ to_free = indirect_to_ptr(to_free);
- root->rnode = to_free->slots[0];
+ /*
+ * The candidate node has more than one child, or its child
+ * is not at the leftmost slot, we cannot shrink.
+ */
+ if (to_free->count != 1)
+ break;
+ if (!to_free->slots[0])
+ break;
+
+ /*
+ * We don't need rcu_assign_pointer(), since we are simply
+ * moving the node from one part of the tree to another: if it
+ * was safe to dereference the old pointer to it
+ * (to_free->slots[0]), it will be safe to dereference the new
+ * one (root->rnode) as far as dependent read barriers go.
+ */
+ newptr = to_free->slots[0];
+ if (root->height > 1)
+ newptr = ptr_to_indirect(newptr);
+ root->rnode = newptr;
root->height--;
- /* must only free zeroed nodes into the slab */
- tag_clear(to_free, 0, 0);
- tag_clear(to_free, 1, 0);
- to_free->slots[0] = NULL;
- to_free->count = 0;
+
+ /*
+ * We have a dilemma here. The node's slot[0] must not be
+ * NULLed in case there are concurrent lookups expecting to
+ * find the item. However if this was a bottom-level node,
+ * then it may be subject to the slot pointer being visible
+ * to callers dereferencing it. If item corresponding to
+ * slot[0] is subsequently deleted, these callers would expect
+ * their slot to become empty sooner or later.
+ *
+ * For example, lockless pagecache will look up a slot, deref
+ * the page pointer, and if the page is 0 refcount it means it
+ * was concurrently deleted from pagecache so try the deref
+ * again. Fortunately there is already a requirement for logic
+ * to retry the entire slot lookup -- the indirect pointer
+ * problem (replacing direct root node with an indirect pointer
+ * also results in a stale slot). So tag the slot as indirect
+ * to force callers to retry.
+ */
+ if (root->height == 0)
+ *((unsigned long *)&to_free->slots[0]) |=
+ RADIX_TREE_INDIRECT_PTR;
+
radix_tree_node_free(to_free);
}
}
*/
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
- struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+ /*
+ * The radix tree path needs to be one longer than the maximum path
+ * since the "list" is null terminated.
+ */
+ struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
struct radix_tree_node *slot = NULL;
+ struct radix_tree_node *to_free;
unsigned int height, shift;
int tag;
int offset;
goto out;
slot = root->rnode;
- if (height == 0 && root->rnode) {
+ if (height == 0) {
root_tag_clear_all(root);
root->rnode = NULL;
goto out;
}
+ slot = indirect_to_ptr(slot);
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
pathp->node = NULL;
radix_tree_tag_clear(root, index, tag);
}
+ to_free = NULL;
/* Now free the nodes we do not need anymore */
while (pathp->node) {
pathp->node->slots[pathp->offset] = NULL;
pathp->node->count--;
+ /*
+ * Queue the node for deferred freeing after the
+ * last reference to it disappears (set NULL, above).
+ */
+ if (to_free)
+ radix_tree_node_free(to_free);
if (pathp->node->count) {
- if (pathp->node == root->rnode)
+ if (pathp->node == indirect_to_ptr(root->rnode))
radix_tree_shrink(root);
goto out;
}
/* Node with zero slots in use so free it */
- radix_tree_node_free(pathp->node);
-
+ to_free = pathp->node;
pathp--;
+
}
root_tag_clear_all(root);
root->height = 0;
root->rnode = NULL;
+ if (to_free)
+ radix_tree_node_free(to_free);
out:
return slot;
EXPORT_SYMBOL(radix_tree_tagged);
static void
-radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
+radix_tree_node_ctor(void *node)
{
memset(node, 0, sizeof(struct radix_tree_node));
}
static __init unsigned long __maxindex(unsigned int height)
{
- unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
- unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
-
- if (tmp >= RADIX_TREE_INDEX_BITS)
- index = ~0UL;
- return index;
+ 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)
height_to_maxindex[i] = __maxindex(i);
}
-#ifdef CONFIG_HOTPLUG_CPU
static int radix_tree_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
struct radix_tree_preload *rtp;
/* Free per-cpu pool of perloaded nodes */
- if (action == CPU_DEAD) {
+ if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
rtp = &per_cpu(radix_tree_preloads, cpu);
while (rtp->nr) {
kmem_cache_free(radix_tree_node_cachep,
}
return NOTIFY_OK;
}
-#endif /* CONFIG_HOTPLUG_CPU */
void __init radix_tree_init(void)
{
radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
sizeof(struct radix_tree_node), 0,
- SLAB_PANIC, radix_tree_node_ctor, NULL);
+ SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
+ radix_tree_node_ctor);
radix_tree_init_maxindex();
hotcpu_notifier(radix_tree_callback, 0);
}
Code Review / linux-2.6.git / blobdiff