diff options
| -rw-r--r-- | include/linux/radix-tree.h | 196 | ||||
| -rw-r--r-- | lib/radix-tree.c | 151 |
2 files changed, 347 insertions, 0 deletions
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index e9a48234e693..0d04cd69ab9b 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -2,6 +2,7 @@ * Copyright (C) 2001 Momchil Velikov * Portions Copyright (C) 2001 Christoph Hellwig * 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 @@ -257,4 +258,199 @@ static inline void radix_tree_preload_end(void) preempt_enable(); } +/** + * struct radix_tree_iter - radix tree iterator state + * + * @index: index of current slot + * @next_index: next-to-last index for this chunk + * @tags: bit-mask for tag-iterating + * + * This radix tree iterator works in terms of "chunks" of slots. A chunk is a + * subinterval of slots contained within one radix tree leaf node. It is + * described by a pointer to its first slot and a struct radix_tree_iter + * which holds the chunk's position in the tree and its size. For tagged + * iteration radix_tree_iter also holds the slots' bit-mask for one chosen + * radix tree tag. + */ +struct radix_tree_iter { + unsigned long index; + unsigned long next_index; + unsigned long tags; +}; + +#define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */ +#define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */ +#define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */ + +/** + * radix_tree_iter_init - initialize radix tree iterator + * + * @iter: pointer to iterator state + * @start: iteration starting index + * Returns: NULL + */ +static __always_inline void ** +radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start) +{ + /* + * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it + * in the case of a successful tagged chunk lookup. If the lookup was + * unsuccessful or non-tagged then nobody cares about ->tags. + * + * Set index to zero to bypass next_index overflow protection. + * See the comment in radix_tree_next_chunk() for details. + */ + iter->index = 0; + iter->next_index = start; + return NULL; +} + +/** + * 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 there no more left + * + * This function looks up the next chunk in the radix tree starting from + * @iter->next_index. It returns a pointer to the chunk's first slot. + * Also it fills @iter with data about chunk: position in the tree (index), + * its end (next_index), and constructs a bit mask for tagged iterating (tags). + */ +void **radix_tree_next_chunk(struct radix_tree_root *root, + struct radix_tree_iter *iter, unsigned flags); + +/** + * radix_tree_chunk_size - get current chunk size + * + * @iter: pointer to radix tree iterator + * Returns: current chunk size + */ +static __always_inline unsigned +radix_tree_chunk_size(struct radix_tree_iter *iter) +{ + return iter->next_index - iter->index; +} + +/** + * radix_tree_next_slot - find next slot in chunk + * + * @slot: pointer to current slot + * @iter: pointer to interator state + * @flags: RADIX_TREE_ITER_*, should be constant + * Returns: pointer to next slot, or NULL if there no more left + * + * This function updates @iter->index in the case of a successful lookup. + * For tagged lookup it also eats @iter->tags. + */ +static __always_inline void ** +radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags) +{ + if (flags & RADIX_TREE_ITER_TAGGED) { + iter->tags >>= 1; + if (likely(iter->tags & 1ul)) { + iter->index++; + return slot + 1; + } + if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) { + unsigned offset = __ffs(iter->tags); + + iter->tags >>= offset; + iter->index += offset + 1; + return slot + offset + 1; + } + } else { + unsigned size = radix_tree_chunk_size(iter) - 1; + + while (size--) { + slot++; + iter->index++; + if (likely(*slot)) + return slot; + if (flags & RADIX_TREE_ITER_CONTIG) + break; + } + } + return NULL; +} + +/** + * radix_tree_for_each_chunk - iterate over chunks + * + * @slot: the void** variable for pointer to chunk first slot + * @root: the struct radix_tree_root pointer + * @iter: the struct radix_tree_iter pointer + * @start: iteration starting index + * @flags: RADIX_TREE_ITER_* and tag index + * + * Locks can be released and reacquired between iterations. + */ +#define radix_tree_for_each_chunk(slot, root, iter, start, flags) \ + for (slot = radix_tree_iter_init(iter, start) ; \ + (slot = radix_tree_next_chunk(root, iter, flags)) ;) + +/** + * radix_tree_for_each_chunk_slot - iterate over slots in one chunk + * + * @slot: the void** variable, at the beginning points to chunk first slot + * @iter: the struct radix_tree_iter pointer + * @flags: RADIX_TREE_ITER_*, should be constant + * + * This macro is designed to be nested inside radix_tree_for_each_chunk(). + * @slot points to the radix tree slot, @iter->index contains its index. + */ +#define radix_tree_for_each_chunk_slot(slot, iter, flags) \ + for (; slot ; slot = radix_tree_next_slot(slot, iter, flags)) + +/** + * radix_tree_for_each_slot - iterate over non-empty slots + * + * @slot: the void** variable for pointer to slot + * @root: the struct radix_tree_root pointer + * @iter: the struct radix_tree_iter pointer + * @start: iteration starting index + * + * @slot points to radix tree slot, @iter->index contains its index. + */ +#define radix_tree_for_each_slot(slot, root, iter, start) \ + for (slot = radix_tree_iter_init(iter, start) ; \ + slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \ + slot = radix_tree_next_slot(slot, iter, 0)) + +/** + * radix_tree_for_each_contig - iterate over contiguous slots + * + * @slot: the void** variable for pointer to slot + * @root: the struct radix_tree_root pointer + * @iter: the struct radix_tree_iter pointer + * @start: iteration starting index + * + * @slot points to radix tree slot, @iter->index contains its index. + */ +#define radix_tree_for_each_contig(slot, root, iter, start) \ + for (slot = radix_tree_iter_init(iter, start) ; \ + slot || (slot = radix_tree_next_chunk(root, iter, \ + RADIX_TREE_ITER_CONTIG)) ; \ + slot = radix_tree_next_slot(slot, iter, \ + RADIX_TREE_ITER_CONTIG)) + +/** + * radix_tree_for_each_tagged - iterate over tagged slots + * + * @slot: the void** variable for pointer to slot + * @root: the struct radix_tree_root pointer + * @iter: the struct radix_tree_iter pointer + * @start: iteration starting index + * @tag: tag index + * + * @slot points to radix tree slot, @iter->index contains its index. + */ +#define radix_tree_for_each_tagged(slot, root, iter, start, tag) \ + for (slot = radix_tree_iter_init(iter, start) ; \ + slot || (slot = radix_tree_next_chunk(root, iter, \ + RADIX_TREE_ITER_TAGGED | tag)) ; \ + slot = radix_tree_next_slot(slot, iter, \ + RADIX_TREE_ITER_TAGGED)) + #endif /* _LINUX_RADIX_TREE_H */ 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 |