1 files changed, 151 insertions, 0 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 3e69c2b66c9..fefa76e6ff9 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -3,6 +3,7 @@
  * Portions Copyright (C) 2001 Christoph Hellwig
  * Copyright (C) 2005 SGI, Christoph Lameter
  * Copyright (C) 2006 Nick Piggin
+ * Copyright (C) 2012 Konstantin Khlebnikov
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -146,6 +147,43 @@ static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
         }
         return 0;
 }
+
+/**
+ * radix_tree_find_next_bit - find the next set bit in a memory region
+ *
+ * @addr: The address to base the search on
+ * @size: The bitmap size in bits
+ * @offset: The bitnumber to start searching at
+ *
+ * Unrollable variant of find_next_bit() for constant size arrays.
+ * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
+ * Returns next bit offset, or size if nothing found.
+ */
+static __always_inline unsigned long
+radix_tree_find_next_bit(const unsigned long *addr,
+                         unsigned long size, unsigned long offset)
+{
+        if (!__builtin_constant_p(size))
+                return find_next_bit(addr, size, offset);
+
+        if (offset < size) {
+                unsigned long tmp;
+
+                addr += offset / BITS_PER_LONG;
+                tmp = *addr >> (offset % BITS_PER_LONG);
+                if (tmp)
+                        return __ffs(tmp) + offset;
+                offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
+                while (offset < size) {
+                        tmp = *++addr;
+                        if (tmp)
+                                return __ffs(tmp) + offset;
+                        offset += BITS_PER_LONG;
+                }
+        }
+        return size;
+}
+
 /*
  * This assumes that the caller has performed appropriate preallocation, and
  * that the caller has pinned this thread of control to the current CPU.
@@ -613,6 +651,119 @@ int radix_tree_tag_get(struct radix_tree_root *root,
 EXPORT_SYMBOL(radix_tree_tag_get);
 
 /**
+ * radix_tree_next_chunk - find next chunk of slots for iteration
+ *
+ * @root:       radix tree root
+ * @iter:       iterator state
+ * @flags:      RADIX_TREE_ITER_* flags and tag index
+ * Returns:     pointer to chunk first slot, or NULL if iteration is over
+ */
+void **radix_tree_next_chunk(struct radix_tree_root *root,
+                             struct radix_tree_iter *iter, unsigned flags)
+{
+        unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
+        struct radix_tree_node *rnode, *node;
+        unsigned long index, offset;
+
+        if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
+                return NULL;
+
+        /*
+         * Catch next_index overflow after ~0UL. iter->index never overflows
+         * during iterating; it can be zero only at the beginning.
+         * And we cannot overflow iter->next_index in a single step,
+         * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
+         */
+        index = iter->next_index;
+        if (!index && iter->index)
+                return NULL;
+
+        rnode = rcu_dereference_raw(root->rnode);
+        if (radix_tree_is_indirect_ptr(rnode)) {
+                rnode = indirect_to_ptr(rnode);
+        } else if (rnode && !index) {
+                /* Single-slot tree */
+                iter->index = 0;
+                iter->next_index = 1;
+                iter->tags = 1;
+                return (void **)&root->rnode;
+        } else
+                return NULL;
+
+restart:
+        shift = (rnode->height - 1) * RADIX_TREE_MAP_SHIFT;
+        offset = index >> shift;
+
+        /* Index outside of the tree */
+        if (offset >= RADIX_TREE_MAP_SIZE)
+                return NULL;
+
+        node = rnode;
+        while (1) {
+                if ((flags & RADIX_TREE_ITER_TAGGED) ?
+                                !test_bit(offset, node->tags[tag]) :
+                                !node->slots[offset]) {
+                        /* Hole detected */
+                        if (flags & RADIX_TREE_ITER_CONTIG)
+                                return NULL;
+
+                        if (flags & RADIX_TREE_ITER_TAGGED)
+                                offset = radix_tree_find_next_bit(
+                                                node->tags[tag],
+                                                RADIX_TREE_MAP_SIZE,
+                                                offset + 1);
+                        else
+                                while (++offset < RADIX_TREE_MAP_SIZE) {
+                                        if (node->slots[offset])
+                                                break;
+                                }
+                        index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
+                        index += offset << shift;
+                        /* Overflow after ~0UL */
+                        if (!index)
+                                return NULL;
+                        if (offset == RADIX_TREE_MAP_SIZE)
+                                goto restart;
+                }
+
+                /* This is leaf-node */
+                if (!shift)
+                        break;
+
+                node = rcu_dereference_raw(node->slots[offset]);
+                if (node == NULL)
+                        goto restart;
+                shift -= RADIX_TREE_MAP_SHIFT;
+                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+        }
+
+        /* Update the iterator state */
+        iter->index = index;
+        iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
+
+        /* Construct iter->tags bit-mask from node->tags[tag] array */
+        if (flags & RADIX_TREE_ITER_TAGGED) {
+                unsigned tag_long, tag_bit;
+
+                tag_long = offset / BITS_PER_LONG;
+                tag_bit  = offset % BITS_PER_LONG;
+                iter->tags = node->tags[tag][tag_long] >> tag_bit;
+                /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
+                if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
+                        /* Pick tags from next element */
+                        if (tag_bit)
+                                iter->tags |= node->tags[tag][tag_long + 1] <<
+                                                (BITS_PER_LONG - tag_bit);
+                        /* Clip chunk size, here only BITS_PER_LONG tags */
+                        iter->next_index = index + BITS_PER_LONG;
+                }
+        }
+
+        return node->slots + offset;
+}
+EXPORT_SYMBOL(radix_tree_next_chunk);
+
+/**
  * 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