locking: Rename __RAW_SPIN_LOCK_UNLOCKED to __ARCH_SPIN_LOCK_UNLOCKED
[linux-2.6.git] / lib / radix-tree.c
index c0bd4a9..92cdd99 100644 (file)
@@ -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
 #include <linux/gfp.h>
 #include <linux/string.h>
 #include <linux/bitops.h>
+#include <linux/rcupdate.h>
 
 
 #ifdef __KERNEL__
-#define RADIX_TREE_MAP_SHIFT   6
+#define RADIX_TREE_MAP_SHIFT   (CONFIG_BASE_SMALL ? 4 : 6)
 #else
 #define RADIX_TREE_MAP_SHIFT   3       /* For more stressful testing */
 #endif
-#define RADIX_TREE_TAGS                2
 
 #define RADIX_TREE_MAP_SIZE    (1UL << RADIX_TREE_MAP_SHIFT)
 #define RADIX_TREE_MAP_MASK    (RADIX_TREE_MAP_SIZE-1)
        ((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_TAGS][RADIX_TREE_TAG_LONGS];
+       unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
 };
 
 struct radix_tree_path {
@@ -57,14 +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
@@ -73,21 +81,82 @@ 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.
  */
 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, root->gfp_mask);
-       if (ret == NULL && !(root->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];
@@ -95,13 +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);
 }
 
 /*
@@ -109,6 +200,9 @@ radix_tree_node_free(struct radix_tree_node *node)
  * 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)
 {
@@ -134,35 +228,7 @@ int radix_tree_preload(gfp_t gfp_mask)
 out:
        return ret;
 }
-
-static inline void tag_set(struct radix_tree_node *node, int tag, int offset)
-{
-       __set_bit(offset, node->tags[tag]);
-}
-
-static inline void tag_clear(struct radix_tree_node *node, int tag, int offset)
-{
-       __clear_bit(offset, node->tags[tag]);
-}
-
-static inline int tag_get(struct radix_tree_node *node, int tag, int offset)
-{
-       return test_bit(offset, node->tags[tag]);
-}
-
-/*
- * 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, 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
@@ -180,7 +246,6 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 {
        struct radix_tree_node *node;
        unsigned int height;
-       char tags[RADIX_TREE_TAGS];
        int tag;
 
        /* Figure out what the height should be.  */
@@ -193,32 +258,26 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
                goto out;
        }
 
-       /*
-        * Prepare the tag status of the top-level node for propagation
-        * into the newly-pushed top-level node(s)
-        */
-       for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
-               tags[tag] = 0;
-               if (any_tag_set(root->rnode, tag))
-                       tags[tag] = 1;
-       }
-
        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_TAGS; tag++) {
-                       if (tags[tag])
+               for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
+                       if (root_tag_get(root, tag))
                                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;
@@ -240,29 +299,33 @@ 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 && !root->rnode) ||
-                       index > radix_tree_maxindex(root->height)) {
+       if (index > radix_tree_maxindex(root->height)) {
                error = radix_tree_extend(root, index);
                if (error)
                        return error;
        }
 
-       slot = root->rnode;
+       slot = radix_tree_indirect_to_ptr(root->rnode);
+
        height = root->height;
        shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 
        offset = 0;                     /* uninitialised var warning */
-       do {
+       while (height > 0) {
                if (slot == NULL) {
                        /* 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 */
@@ -271,46 +334,65 @@ int radix_tree_insert(struct radix_tree_root *root,
                slot = node->slots[offset];
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
-       } while (height > 0);
+       }
 
        if (slot != NULL)
                return -EEXIST;
 
-       BUG_ON(!node);
-       node->count++;
-       node->slots[offset] = item;
-       BUG_ON(tag_get(node, 0, offset));
-       BUG_ON(tag_get(node, 1, offset));
+       if (node) {
+               node->count++;
+               rcu_assign_pointer(node->slots[offset], item);
+               BUG_ON(tag_get(node, 0, offset));
+               BUG_ON(tag_get(node, 1, offset));
+       } else {
+               rcu_assign_pointer(root->rnode, item);
+               BUG_ON(root_tag_get(root, 0));
+               BUG_ON(root_tag_get(root, 1));
+       }
 
        return 0;
 }
 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;
 
        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;
 }
 
 /**
@@ -318,12 +400,17 @@ 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);
 
@@ -333,13 +420,15 @@ 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);
 
@@ -349,24 +438,24 @@ EXPORT_SYMBOL(radix_tree_lookup);
  *     @index:         index key
  *     @tag:           tag index
  *
- *     Set the search tag corresponging to @index in the radix tree.  From
+ *     Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
+ *     corresponding to @index in the radix tree.  From
  *     the root all the way down to the leaf node.
  *
  *     Returns the address of the tagged item.   Setting a tag on a not-present
  *     item is a bug.
  */
 void *radix_tree_tag_set(struct radix_tree_root *root,
-                       unsigned long index, int tag)
+                       unsigned long index, unsigned int tag)
 {
        unsigned int height, shift;
        struct radix_tree_node *slot;
 
        height = root->height;
-       if (index > radix_tree_maxindex(height))
-               return NULL;
+       BUG_ON(index > radix_tree_maxindex(height));
 
+       slot = radix_tree_indirect_to_ptr(root->rnode);
        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
-       slot = root->rnode;
 
        while (height > 0) {
                int offset;
@@ -380,6 +469,10 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
                height--;
        }
 
+       /* set the root's tag bit */
+       if (slot && !root_tag_get(root, tag))
+               root_tag_set(root, tag);
+
        return slot;
 }
 EXPORT_SYMBOL(radix_tree_tag_set);
@@ -390,7 +483,8 @@ EXPORT_SYMBOL(radix_tree_tag_set);
  *     @index:         index key
  *     @tag:           tag index
  *
- *     Clear the search tag corresponging to @index in the radix tree.  If
+ *     Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
+ *     corresponding to @index in the radix tree.  If
  *     this causes the leaf node to have no tags set then clear the tag in the
  *     next-to-leaf node, etc.
  *
@@ -398,12 +492,15 @@ EXPORT_SYMBOL(radix_tree_tag_set);
  *     has the same return value and semantics as radix_tree_lookup().
  */
 void *radix_tree_tag_clear(struct radix_tree_root *root,
-                       unsigned long index, int tag)
+                       unsigned long index, unsigned int tag)
 {
-       struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
-       struct radix_tree_node *slot;
+       /*
+        * 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;
-       void *ret = NULL;
 
        height = root->height;
        if (index > radix_tree_maxindex(height))
@@ -411,7 +508,7 @@ 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;
@@ -428,54 +525,67 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
                height--;
        }
 
-       ret = slot;
-       if (ret == NULL)
+       if (slot == NULL)
                goto out;
 
-       do {
+       while (pathp->node) {
                if (!tag_get(pathp->node, tag, pathp->offset))
                        goto out;
                tag_clear(pathp->node, tag, pathp->offset);
                if (any_tag_set(pathp->node, tag))
                        goto out;
                pathp--;
-       } while (pathp->node);
+       }
+
+       /* clear the root's tag bit */
+       if (root_tag_get(root, tag))
+               root_tag_clear(root, tag);
+
 out:
-       return ret;
+       return slot;
 }
 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
  * @index:             index key
- * @tag:               tag index
+ * @tag:               tag index (< RADIX_TREE_MAX_TAGS)
  *
  * Return values:
  *
- *  0: tag not present
- *  1: tag present, set
- * -1: tag present, unset
+ *  0: tag not present or not set
+ *  1: tag set
  */
 int radix_tree_tag_get(struct radix_tree_root *root,
-                       unsigned long index, int tag)
+                       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;
+       /* check the root's tag bit */
+       if (!root_tag_get(root, tag))
+               return 0;
+
+       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;
@@ -484,61 +594,133 @@ 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 ? 1 : -1;
+                       return !!ret;
                }
-               slot = slot->slots[offset];
+               node = rcu_dereference(node->slots[offset]);
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }
 }
 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;
+       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;
                }
@@ -560,79 +742,182 @@ 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,
-       unsigned int max_items, unsigned long *next_index, int tag)
+__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;
 
-       shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
-       slot = root->rnode;
+       height = slot->height;
+       if (height == 0)
+               goto out;
+       shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 
        while (height > 0) {
-               unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
+               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];
+               slot = rcu_dereference(slot->slots[i]);
+               if (slot == NULL)
+                       break;
        }
 out:
        *next_index = index;
@@ -646,7 +931,7 @@ out:
  *     @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
+ *     @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 items at *@results and
@@ -654,48 +939,156 @@ out:
  */
 unsigned int
 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
-               unsigned long first_index, unsigned int max_items, int tag)
+               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 > 1 &&
-                       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 = radix_tree_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).
+                */
+               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);
        }
 }
@@ -711,13 +1104,14 @@ 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;
-       struct radix_tree_path *orig_pathp;
-       struct radix_tree_node *slot;
+       /*
+        * 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;
-       void *ret = NULL;
-       char tags[RADIX_TREE_TAGS];
-       int nr_cleared_tags;
        int tag;
        int offset;
 
@@ -725,11 +1119,18 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
        if (index > radix_tree_maxindex(height))
                goto out;
 
+       slot = 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;
-       slot = root->rnode;
 
-       for ( ; height > 0; height--) {
+       do {
                if (slot == NULL)
                        goto out;
 
@@ -739,58 +1140,52 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
                pathp->node = slot;
                slot = slot->slots[offset];
                shift -= RADIX_TREE_MAP_SHIFT;
-       }
+               height--;
+       } while (height > 0);
 
-       ret = slot;
-       if (ret == NULL)
+       if (slot == NULL)
                goto out;
 
-       orig_pathp = pathp;
-
        /*
         * Clear all tags associated with the just-deleted item
         */
-       nr_cleared_tags = 0;
-       for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
-               if (tag_get(pathp->node, tag, pathp->offset)) {
-                       tag_clear(pathp->node, tag, pathp->offset);
-                       tags[tag] = 0;
-                       nr_cleared_tags++;
-               } else
-                       tags[tag] = 1;
-       }
-
-       for (pathp--; nr_cleared_tags && pathp->node; pathp--) {
-               for (tag = 0; tag < RADIX_TREE_TAGS; tag++) {
-                       if (tags[tag])
-                               continue;
-
-                       tag_clear(pathp->node, tag, pathp->offset);
-                       if (any_tag_set(pathp->node, tag)) {
-                               tags[tag] = 1;
-                               nr_cleared_tags--;
-                       }
-               }
+       for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
+               if (tag_get(pathp->node, tag, pathp->offset))
+                       radix_tree_tag_clear(root, index, tag);
        }
 
+       to_free = NULL;
        /* Now free the nodes we do not need anymore */
-       for (pathp = orig_pathp; pathp->node; pathp--) {
+       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->rnode = NULL;
+       root_tag_clear_all(root);
        root->height = 0;
+       root->rnode = NULL;
+       if (to_free)
+               radix_tree_node_free(to_free);
+
 out:
-       return ret;
+       return slot;
 }
 EXPORT_SYMBOL(radix_tree_delete);
 
@@ -799,30 +1194,28 @@ EXPORT_SYMBOL(radix_tree_delete);
  *     @root:          radix tree root
  *     @tag:           tag to test
  */
-int radix_tree_tagged(struct radix_tree_root *root, int tag)
+int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
 {
-       struct radix_tree_node *rnode;
-       rnode = root->rnode;
-       if (!rnode)
-               return 0;
-       return any_tag_set(rnode, tag);
+       return root_tag_get(root, 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)
@@ -833,7 +1226,6 @@ 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)
@@ -842,7 +1234,7 @@ 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,
@@ -853,13 +1245,13 @@ 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);
 }