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Diffstat (limited to 'include/linux/generic-radix-tree.h')
| -rw-r--r-- | include/linux/generic-radix-tree.h | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/include/linux/generic-radix-tree.h b/include/linux/generic-radix-tree.h new file mode 100644 index 000000000000..3a91130a4fbd --- /dev/null +++ b/include/linux/generic-radix-tree.h @@ -0,0 +1,231 @@ +#ifndef _LINUX_GENERIC_RADIX_TREE_H +#define _LINUX_GENERIC_RADIX_TREE_H + +/** + * DOC: Generic radix trees/sparse arrays: + * + * Very simple and minimalistic, supporting arbitrary size entries up to + * PAGE_SIZE. + * + * A genradix is defined with the type it will store, like so: + * + * static GENRADIX(struct foo) foo_genradix; + * + * The main operations are: + * + * - genradix_init(radix) - initialize an empty genradix + * + * - genradix_free(radix) - free all memory owned by the genradix and + * reinitialize it + * + * - genradix_ptr(radix, idx) - gets a pointer to the entry at idx, returning + * NULL if that entry does not exist + * + * - genradix_ptr_alloc(radix, idx, gfp) - gets a pointer to an entry, + * allocating it if necessary + * + * - genradix_for_each(radix, iter, p) - iterate over each entry in a genradix + * + * The radix tree allocates one page of entries at a time, so entries may exist + * that were never explicitly allocated - they will be initialized to all + * zeroes. + * + * Internally, a genradix is just a radix tree of pages, and indexing works in + * terms of byte offsets. The wrappers in this header file use sizeof on the + * type the radix contains to calculate a byte offset from the index - see + * __idx_to_offset. + */ + +#include <asm/page.h> +#include <linux/bug.h> +#include <linux/kernel.h> +#include <linux/log2.h> + +struct genradix_root; + +struct __genradix { + struct genradix_root __rcu *root; +}; + +/* + * NOTE: currently, sizeof(_type) must not be larger than PAGE_SIZE: + */ + +#define __GENRADIX_INITIALIZER \ + { \ + .tree = { \ + .root = NULL, \ + } \ + } + +/* + * We use a 0 size array to stash the type we're storing without taking any + * space at runtime - then the various accessor macros can use typeof() to get + * to it for casts/sizeof - we also force the alignment so that storing a type + * with a ridiculous alignment doesn't blow up the alignment or size of the + * genradix. + */ + +#define GENRADIX(_type) \ +struct { \ + struct __genradix tree; \ + _type type[0] __aligned(1); \ +} + +#define DEFINE_GENRADIX(_name, _type) \ + GENRADIX(_type) _name = __GENRADIX_INITIALIZER + +/** + * genradix_init - initialize a genradix + * @_radix: genradix to initialize + * + * Does not fail + */ +#define genradix_init(_radix) \ +do { \ + *(_radix) = (typeof(*_radix)) __GENRADIX_INITIALIZER; \ +} while (0) + +void __genradix_free(struct __genradix *); + +/** + * genradix_free: free all memory owned by a genradix + * @_radix: the genradix to free + * + * After freeing, @_radix will be reinitialized and empty + */ +#define genradix_free(_radix) __genradix_free(&(_radix)->tree) + +static inline size_t __idx_to_offset(size_t idx, size_t obj_size) +{ + if (__builtin_constant_p(obj_size)) + BUILD_BUG_ON(obj_size > PAGE_SIZE); + else + BUG_ON(obj_size > PAGE_SIZE); + + if (!is_power_of_2(obj_size)) { + size_t objs_per_page = PAGE_SIZE / obj_size; + + return (idx / objs_per_page) * PAGE_SIZE + + (idx % objs_per_page) * obj_size; + } else { + return idx * obj_size; + } +} + +#define __genradix_cast(_radix) (typeof((_radix)->type[0]) *) +#define __genradix_obj_size(_radix) sizeof((_radix)->type[0]) +#define __genradix_idx_to_offset(_radix, _idx) \ + __idx_to_offset(_idx, __genradix_obj_size(_radix)) + +void *__genradix_ptr(struct __genradix *, size_t); + +/** + * genradix_ptr - get a pointer to a genradix entry + * @_radix: genradix to access + * @_idx: index to fetch + * + * Returns a pointer to entry at @_idx, or NULL if that entry does not exist. + */ +#define genradix_ptr(_radix, _idx) \ + (__genradix_cast(_radix) \ + __genradix_ptr(&(_radix)->tree, \ + __genradix_idx_to_offset(_radix, _idx))) + +void *__genradix_ptr_alloc(struct __genradix *, size_t, gfp_t); + +/** + * genradix_ptr_alloc - get a pointer to a genradix entry, allocating it + * if necessary + * @_radix: genradix to access + * @_idx: index to fetch + * @_gfp: gfp mask + * + * Returns a pointer to entry at @_idx, or NULL on allocation failure + */ +#define genradix_ptr_alloc(_radix, _idx, _gfp) \ + (__genradix_cast(_radix) \ + __genradix_ptr_alloc(&(_radix)->tree, \ + __genradix_idx_to_offset(_radix, _idx), \ + _gfp)) + +struct genradix_iter { + size_t offset; + size_t pos; +}; + +/** + * genradix_iter_init - initialize a genradix_iter + * @_radix: genradix that will be iterated over + * @_idx: index to start iterating from + */ +#define genradix_iter_init(_radix, _idx) \ + ((struct genradix_iter) { \ + .pos = (_idx), \ + .offset = __genradix_idx_to_offset((_radix), (_idx)),\ + }) + +void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t); + +/** + * genradix_iter_peek - get first entry at or above iterator's current + * position + * @_iter: a genradix_iter + * @_radix: genradix being iterated over + * + * If no more entries exist at or above @_iter's current position, returns NULL + */ +#define genradix_iter_peek(_iter, _radix) \ + (__genradix_cast(_radix) \ + __genradix_iter_peek(_iter, &(_radix)->tree, \ + PAGE_SIZE / __genradix_obj_size(_radix))) + +static inline void __genradix_iter_advance(struct genradix_iter *iter, + size_t obj_size) +{ + iter->offset += obj_size; + + if (!is_power_of_2(obj_size) && + (iter->offset & (PAGE_SIZE - 1)) + obj_size > PAGE_SIZE) + iter->offset = round_up(iter->offset, PAGE_SIZE); + + iter->pos++; +} + +#define genradix_iter_advance(_iter, _radix) \ + __genradix_iter_advance(_iter, __genradix_obj_size(_radix)) + +#define genradix_for_each_from(_radix, _iter, _p, _start) \ + for (_iter = genradix_iter_init(_radix, _start); \ + (_p = genradix_iter_peek(&_iter, _radix)) != NULL; \ + genradix_iter_advance(&_iter, _radix)) + +/** + * genradix_for_each - iterate over entry in a genradix + * @_radix: genradix to iterate over + * @_iter: a genradix_iter to track current position + * @_p: pointer to genradix entry type + * + * On every iteration, @_p will point to the current entry, and @_iter.pos + * will be the current entry's index. + */ +#define genradix_for_each(_radix, _iter, _p) \ + genradix_for_each_from(_radix, _iter, _p, 0) + +int __genradix_prealloc(struct __genradix *, size_t, gfp_t); + +/** + * genradix_prealloc - preallocate entries in a generic radix tree + * @_radix: genradix to preallocate + * @_nr: number of entries to preallocate + * @_gfp: gfp mask + * + * Returns 0 on success, -ENOMEM on failure + */ +#define genradix_prealloc(_radix, _nr, _gfp) \ + __genradix_prealloc(&(_radix)->tree, \ + __genradix_idx_to_offset(_radix, _nr + 1),\ + _gfp) + + +#endif /* _LINUX_GENERIC_RADIX_TREE_H */ |