diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/radix-tree.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 3e69c2b66c94..fefa76e6ff96 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 |