X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=lib%2Fradix-tree.c;h=23abbd93cae1fd50b87b2ed5f8ffd95d940230b1;hb=a9d9058abab4ac17b79d500506e6c74bd16cecdc;hp=7cbdada51049738f4bd105f88f1ca0956daa390f;hpb=cfd9b7df4abd3257c9e381b0e445817b26a51c0c;p=safe%2Fjmp%2Flinux-2.6

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 7cbdada..23abbd9 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1,7 +1,8 @@
 /*
  * 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
@@ -30,6 +31,7 @@
 #include <linux/gfp.h>
 #include <linux/string.h>
 #include <linux/bitops.h>
+#include <linux/rcupdate.h>
 
 
 #ifdef __KERNEL__
@@ -45,7 +47,9 @@
 	((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;
+	struct rcu_head	rcu_head;
 	void		*slots[RADIX_TREE_MAP_SIZE];
 	unsigned long	tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
 };
@@ -56,14 +60,19 @@ struct radix_tree_path {
 };
 
 #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
@@ -72,13 +81,64 @@ struct radix_tree_preload {
 	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 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.
@@ -86,13 +146,17 @@ static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
 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];
@@ -100,13 +164,35 @@ radix_tree_node_alloc(struct radix_tree_root *root)
 			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);
+
+	/*
+	 * 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.
+	 */
+	tag_clear(node, 0, 0);
+	tag_clear(node, 1, 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);
 }
 
 /*
@@ -139,59 +225,7 @@ 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
@@ -222,11 +256,12 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 	}
 
 	do {
+		unsigned int newheight;
 		if (!(node = radix_tree_node_alloc(root)))
 			return -ENOMEM;
 
 		/* Increase the height.  */
-		node->slots[0] = root->rnode;
+		node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
 
 		/* Propagate the aggregated tag info into the new root */
 		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
@@ -234,9 +269,12 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 				tag_set(node, tag, 0);
 		}
 
+		newheight = root->height+1;
+		node->height = newheight;
 		node->count = 1;
-		root->rnode = node;
-		root->height++;
+		node = radix_tree_ptr_to_indirect(node);
+		rcu_assign_pointer(root->rnode, node);
+		root->height = newheight;
 	} while (height > root->height);
 out:
 	return 0;
@@ -258,6 +296,8 @@ int radix_tree_insert(struct radix_tree_root *root,
 	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);
@@ -265,7 +305,8 @@ int radix_tree_insert(struct radix_tree_root *root,
 			return error;
 	}
 
-	slot = root->rnode;
+	slot = radix_tree_indirect_to_ptr(root->rnode);
+
 	height = root->height;
 	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 
@@ -275,11 +316,13 @@ int radix_tree_insert(struct radix_tree_root *root,
 			/* 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,
+					radix_tree_ptr_to_indirect(slot));
 		}
 
 		/* Go a level down */
@@ -295,11 +338,11 @@ int radix_tree_insert(struct radix_tree_root *root,
 
 	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));
 	}
@@ -308,35 +351,45 @@ int radix_tree_insert(struct radix_tree_root *root,
 }
 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(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 = radix_tree_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(*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:node;
 }
 
 /**
@@ -344,12 +397,17 @@ static inline void **__lookup_slot(struct radix_tree_root *root,
  *	@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);
 
@@ -359,13 +417,15 @@ 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);
 
@@ -389,10 +449,9 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
 	struct radix_tree_node *slot;
 
 	height = root->height;
-	if (index > radix_tree_maxindex(height))
-		return NULL;
+	BUG_ON(index > radix_tree_maxindex(height));
 
-	slot = root->rnode;
+	slot = radix_tree_indirect_to_ptr(root->rnode);
 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 
 	while (height > 0) {
@@ -432,7 +491,11 @@ EXPORT_SYMBOL(radix_tree_tag_set);
 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;
 
@@ -442,7 +505,7 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
 
 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 	pathp->node = NULL;
-	slot = root->rnode;
+	slot = radix_tree_indirect_to_ptr(root->rnode);
 
 	while (height > 0) {
 		int offset;
@@ -496,27 +559,31 @@ 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(root->rnode);
+	if (node == NULL)
+		return 0;
+
+	if (!radix_tree_is_indirect_ptr(node))
+		return (index == 0);
+	node = radix_tree_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;
@@ -525,15 +592,15 @@ int radix_tree_tag_get(struct radix_tree_root *root,
 		 * 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);
+			int ret = tag_get(node, tag, offset);
 
 			BUG_ON(ret && saw_unset_tag);
-			return ret;
+			return !!ret;
 		}
-		slot = slot->slots[offset];
+		node = rcu_dereference(node->slots[offset]);
 		shift -= RADIX_TREE_MAP_SHIFT;
 		height--;
 	}
@@ -541,48 +608,118 @@ int radix_tree_tag_get(struct radix_tree_root *root,
 EXPORT_SYMBOL(radix_tree_tag_get);
 #endif
 
+/**
+ *	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, LONG_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 == LONG_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(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;
 		}
@@ -604,86 +741,183 @@ 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(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 = radix_tree_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] = rcu_dereference(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(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 = radix_tree_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(slot->slots[i]);
+		if (slot == NULL)
+			break;
+	}
 out:
 	*next_index = index;
 	return nr_found;
@@ -707,50 +941,153 @@ radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
 		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(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 = radix_tree_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] = rcu_dereference(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(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 = radix_tree_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;
 
-		root->rnode = to_free->slots[0];
+		BUG_ON(!radix_tree_is_indirect_ptr(to_free));
+		to_free = radix_tree_indirect_to_ptr(to_free);
+
+		/*
+		 * 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).
+		 */
+		newptr = to_free->slots[0];
+		if (root->height > 1)
+			newptr = radix_tree_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;
 		radix_tree_node_free(to_free);
 	}
 }
@@ -766,8 +1103,13 @@ static inline void radix_tree_shrink(struct radix_tree_root *root)
  */
 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;
@@ -777,11 +1119,12 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 		goto out;
 
 	slot = root->rnode;
-	if (height == 0 && root->rnode) {
+	if (height == 0) {
 		root_tag_clear_all(root);
 		root->rnode = NULL;
 		goto out;
 	}
+	slot = radix_tree_indirect_to_ptr(slot);
 
 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 	pathp->node = NULL;
@@ -810,25 +1153,35 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 			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 ==
+					radix_tree_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;
@@ -847,19 +1200,21 @@ int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
 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)
@@ -870,7 +1225,6 @@ 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)
@@ -879,7 +1233,7 @@ static int radix_tree_callback(struct notifier_block *nfb,
        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,
@@ -890,13 +1244,13 @@ static int radix_tree_callback(struct notifier_block *nfb,
        }
        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);
 }