From ba20ba2e3743bac786dff777954c11930256075e Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Mon, 11 Mar 2019 23:31:14 -0700 Subject: [PATCH] generic radix trees Very simple radix tree implementation that supports storing arbitrary size entries, up to PAGE_SIZE - upcoming patches will convert existing flex_array users to genradixes. The new genradix code has a much simpler API and implementation, and doesn't have a hard limit on the number of elements like flex_array does. Link: http://lkml.kernel.org/r/20181217131929.11727-5-kent.overstreet@gmail.com Signed-off-by: Kent Overstreet Cc: Alexey Dobriyan Cc: Al Viro Cc: Dave Hansen Cc: Eric Paris Cc: Marcelo Ricardo Leitner Cc: Matthew Wilcox Cc: Neil Horman Cc: Paul Moore Cc: Pravin B Shelar Cc: Shaohua Li Cc: Stephen Smalley Cc: Vlad Yasevich Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/core-api/generic-radix-tree.rst | 12 + Documentation/core-api/index.rst | 1 + include/linux/generic-radix-tree.h | 231 ++++++++++++++++++ lib/Makefile | 3 +- lib/generic-radix-tree.c | 217 ++++++++++++++++ 5 files changed, 463 insertions(+), 1 deletion(-) create mode 100644 Documentation/core-api/generic-radix-tree.rst create mode 100644 include/linux/generic-radix-tree.h create mode 100644 lib/generic-radix-tree.c diff --git a/Documentation/core-api/generic-radix-tree.rst b/Documentation/core-api/generic-radix-tree.rst new file mode 100644 index 000000000000..ed42839ae42f --- /dev/null +++ b/Documentation/core-api/generic-radix-tree.rst @@ -0,0 +1,12 @@ +================================= +Generic radix trees/sparse arrays +================================= + +.. kernel-doc:: include/linux/generic-radix-tree.h + :doc: Generic radix trees/sparse arrays + +generic radix tree functions +---------------------------- + +.. kernel-doc:: include/linux/generic-radix-tree.h + :functions: diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index 3adee82be311..6870baffef82 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -28,6 +28,7 @@ Core utilities errseq printk-formats circular-buffers + generic-radix-tree memory-allocation mm-api gfp_mask-from-fs-io 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 +#include +#include +#include + +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 */ diff --git a/lib/Makefile b/lib/Makefile index 647517940b29..b798b41d01ae 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -38,7 +38,8 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \ gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \ bsearch.o find_bit.o llist.o memweight.o kfifo.o \ percpu-refcount.o rhashtable.o reciprocal_div.o \ - once.o refcount.o usercopy.o errseq.o bucket_locks.o + once.o refcount.o usercopy.o errseq.o bucket_locks.o \ + generic-radix-tree.o obj-$(CONFIG_STRING_SELFTEST) += test_string.o obj-y += string_helpers.o obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c new file mode 100644 index 000000000000..a7bafc413730 --- /dev/null +++ b/lib/generic-radix-tree.c @@ -0,0 +1,217 @@ + +#include +#include +#include + +#define GENRADIX_ARY (PAGE_SIZE / sizeof(struct genradix_node *)) +#define GENRADIX_ARY_SHIFT ilog2(GENRADIX_ARY) + +struct genradix_node { + union { + /* Interior node: */ + struct genradix_node *children[GENRADIX_ARY]; + + /* Leaf: */ + u8 data[PAGE_SIZE]; + }; +}; + +static inline int genradix_depth_shift(unsigned depth) +{ + return PAGE_SHIFT + GENRADIX_ARY_SHIFT * depth; +} + +/* + * Returns size (of data, in bytes) that a tree of a given depth holds: + */ +static inline size_t genradix_depth_size(unsigned depth) +{ + return 1UL << genradix_depth_shift(depth); +} + +/* depth that's needed for a genradix that can address up to ULONG_MAX: */ +#define GENRADIX_MAX_DEPTH \ + DIV_ROUND_UP(BITS_PER_LONG - PAGE_SHIFT, GENRADIX_ARY_SHIFT) + +#define GENRADIX_DEPTH_MASK \ + ((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1)) + +unsigned genradix_root_to_depth(struct genradix_root *r) +{ + return (unsigned long) r & GENRADIX_DEPTH_MASK; +} + +struct genradix_node *genradix_root_to_node(struct genradix_root *r) +{ + return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK); +} + +/* + * Returns pointer to the specified byte @offset within @radix, or NULL if not + * allocated + */ +void *__genradix_ptr(struct __genradix *radix, size_t offset) +{ + struct genradix_root *r = READ_ONCE(radix->root); + struct genradix_node *n = genradix_root_to_node(r); + unsigned level = genradix_root_to_depth(r); + + if (ilog2(offset) >= genradix_depth_shift(level)) + return NULL; + + while (1) { + if (!n) + return NULL; + if (!level) + break; + + level--; + + n = n->children[offset >> genradix_depth_shift(level)]; + offset &= genradix_depth_size(level) - 1; + } + + return &n->data[offset]; +} +EXPORT_SYMBOL(__genradix_ptr); + +/* + * Returns pointer to the specified byte @offset within @radix, allocating it if + * necessary - newly allocated slots are always zeroed out: + */ +void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset, + gfp_t gfp_mask) +{ + struct genradix_root *v = READ_ONCE(radix->root); + struct genradix_node *n, *new_node = NULL; + unsigned level; + + /* Increase tree depth if necessary: */ + while (1) { + struct genradix_root *r = v, *new_root; + + n = genradix_root_to_node(r); + level = genradix_root_to_depth(r); + + if (n && ilog2(offset) < genradix_depth_shift(level)) + break; + + if (!new_node) { + new_node = (void *) + __get_free_page(gfp_mask|__GFP_ZERO); + if (!new_node) + return NULL; + } + + new_node->children[0] = n; + new_root = ((struct genradix_root *) + ((unsigned long) new_node | (n ? level + 1 : 0))); + + if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) { + v = new_root; + new_node = NULL; + } + } + + while (level--) { + struct genradix_node **p = + &n->children[offset >> genradix_depth_shift(level)]; + offset &= genradix_depth_size(level) - 1; + + n = READ_ONCE(*p); + if (!n) { + if (!new_node) { + new_node = (void *) + __get_free_page(gfp_mask|__GFP_ZERO); + if (!new_node) + return NULL; + } + + if (!(n = cmpxchg_release(p, NULL, new_node))) + swap(n, new_node); + } + } + + if (new_node) + free_page((unsigned long) new_node); + + return &n->data[offset]; +} +EXPORT_SYMBOL(__genradix_ptr_alloc); + +void *__genradix_iter_peek(struct genradix_iter *iter, + struct __genradix *radix, + size_t objs_per_page) +{ + struct genradix_root *r; + struct genradix_node *n; + unsigned level, i; +restart: + r = READ_ONCE(radix->root); + if (!r) + return NULL; + + n = genradix_root_to_node(r); + level = genradix_root_to_depth(r); + + if (ilog2(iter->offset) >= genradix_depth_shift(level)) + return NULL; + + while (level) { + level--; + + i = (iter->offset >> genradix_depth_shift(level)) & + (GENRADIX_ARY - 1); + + while (!n->children[i]) { + i++; + iter->offset = round_down(iter->offset + + genradix_depth_size(level), + genradix_depth_size(level)); + iter->pos = (iter->offset >> PAGE_SHIFT) * + objs_per_page; + if (i == GENRADIX_ARY) + goto restart; + } + + n = n->children[i]; + } + + return &n->data[iter->offset & (PAGE_SIZE - 1)]; +} +EXPORT_SYMBOL(__genradix_iter_peek); + +static void genradix_free_recurse(struct genradix_node *n, unsigned level) +{ + if (level) { + unsigned i; + + for (i = 0; i < GENRADIX_ARY; i++) + if (n->children[i]) + genradix_free_recurse(n->children[i], level - 1); + } + + free_page((unsigned long) n); +} + +int __genradix_prealloc(struct __genradix *radix, size_t size, + gfp_t gfp_mask) +{ + size_t offset; + + for (offset = 0; offset < size; offset += PAGE_SIZE) + if (!__genradix_ptr_alloc(radix, offset, gfp_mask)) + return -ENOMEM; + + return 0; +} +EXPORT_SYMBOL(__genradix_prealloc); + +void __genradix_free(struct __genradix *radix) +{ + struct genradix_root *r = xchg(&radix->root, NULL); + + genradix_free_recurse(genradix_root_to_node(r), + genradix_root_to_depth(r)); +} +EXPORT_SYMBOL(__genradix_free);