Commit f561f135 authored by Kent Overstreet's avatar Kent Overstreet Committed by Stephen Rothwell

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.comSigned-off-by: default avatarKent Overstreet <kent.overstreet@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Pravin B Shelar <pshelar@ovn.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
parent 3e4f48ea
=================================
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:
......@@ -28,6 +28,7 @@ Core utilities
errseq
printk-formats
circular-buffers
generic-radix-tree
memory-allocation
mm-api
gfp_mask-from-fs-io
......
#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 */
......@@ -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
......
#include <linux/export.h>
#include <linux/generic-radix-tree.h>
#include <linux/gfp.h>
#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);
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