lib/generic-radix-tree.c: Add peek_prev()

This patch adds genradix_peek_prev(), genradix_iter_rewind(), and
genradix_for_each_reverse(), for iterating backwards over a generic
radix tree.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-09-12 01:17:22 -04:00
parent 9492261ff2
commit 73badee428
2 changed files with 119 additions and 1 deletions

View File

@ -117,6 +117,11 @@ static inline size_t __idx_to_offset(size_t idx, size_t obj_size)
#define __genradix_cast(_radix) (typeof((_radix)->type[0]) *)
#define __genradix_obj_size(_radix) sizeof((_radix)->type[0])
#define __genradix_objs_per_page(_radix) \
(PAGE_SIZE / sizeof((_radix)->type[0]))
#define __genradix_page_remainder(_radix) \
(PAGE_SIZE % sizeof((_radix)->type[0]))
#define __genradix_idx_to_offset(_radix, _idx) \
__idx_to_offset(_idx, __genradix_obj_size(_radix))
@ -180,7 +185,25 @@ void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t);
#define genradix_iter_peek(_iter, _radix) \
(__genradix_cast(_radix) \
__genradix_iter_peek(_iter, &(_radix)->tree, \
PAGE_SIZE / __genradix_obj_size(_radix)))
__genradix_objs_per_page(_radix)))
void *__genradix_iter_peek_prev(struct genradix_iter *, struct __genradix *,
size_t, size_t);
/**
* genradix_iter_peek_prev - get first entry at or below iterator's current
* position
* @_iter: a genradix_iter
* @_radix: genradix being iterated over
*
* If no more entries exist at or below @_iter's current position, returns NULL
*/
#define genradix_iter_peek_prev(_iter, _radix) \
(__genradix_cast(_radix) \
__genradix_iter_peek_prev(_iter, &(_radix)->tree, \
__genradix_objs_per_page(_radix), \
__genradix_obj_size(_radix) + \
__genradix_page_remainder(_radix)))
static inline void __genradix_iter_advance(struct genradix_iter *iter,
size_t obj_size)
@ -203,6 +226,25 @@ static inline void __genradix_iter_advance(struct genradix_iter *iter,
#define genradix_iter_advance(_iter, _radix) \
__genradix_iter_advance(_iter, __genradix_obj_size(_radix))
static inline void __genradix_iter_rewind(struct genradix_iter *iter,
size_t obj_size)
{
if (iter->offset == 0 ||
iter->offset == SIZE_MAX) {
iter->offset = SIZE_MAX;
return;
}
if ((iter->offset & (PAGE_SIZE - 1)) == 0)
iter->offset -= PAGE_SIZE % obj_size;
iter->offset -= obj_size;
iter->pos--;
}
#define genradix_iter_rewind(_iter, _radix) \
__genradix_iter_rewind(_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; \
@ -220,6 +262,23 @@ static inline void __genradix_iter_advance(struct genradix_iter *iter,
#define genradix_for_each(_radix, _iter, _p) \
genradix_for_each_from(_radix, _iter, _p, 0)
#define genradix_last_pos(_radix) \
(SIZE_MAX / PAGE_SIZE * __genradix_objs_per_page(_radix) - 1)
/**
* genradix_for_each_reverse - iterate over entry in a genradix, reverse order
* @_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_reverse(_radix, _iter, _p) \
for (_iter = genradix_iter_init(_radix, genradix_last_pos(_radix));\
(_p = genradix_iter_peek_prev(&_iter, _radix)) != NULL;\
genradix_iter_rewind(&_iter, _radix))
int __genradix_prealloc(struct __genradix *, size_t, gfp_t);
/**

View File

@ -1,4 +1,5 @@
#include <linux/atomic.h>
#include <linux/export.h>
#include <linux/generic-radix-tree.h>
#include <linux/gfp.h>
@ -212,6 +213,64 @@ restart:
}
EXPORT_SYMBOL(__genradix_iter_peek);
void *__genradix_iter_peek_prev(struct genradix_iter *iter,
struct __genradix *radix,
size_t objs_per_page,
size_t obj_size_plus_page_remainder)
{
struct genradix_root *r;
struct genradix_node *n;
unsigned level, i;
if (iter->offset == SIZE_MAX)
return NULL;
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)) {
iter->offset = genradix_depth_size(level);
iter->pos = (iter->offset >> PAGE_SHIFT) * objs_per_page;
iter->offset -= obj_size_plus_page_remainder;
iter->pos--;
}
while (level) {
level--;
i = (iter->offset >> genradix_depth_shift(level)) &
(GENRADIX_ARY - 1);
while (!n->children[i]) {
size_t objs_per_ptr = genradix_depth_size(level);
iter->offset = round_down(iter->offset, objs_per_ptr);
iter->pos = (iter->offset >> PAGE_SHIFT) * objs_per_page;
if (!iter->offset)
return NULL;
iter->offset -= obj_size_plus_page_remainder;
iter->pos--;
if (!i)
goto restart;
--i;
}
n = n->children[i];
}
return &n->data[iter->offset & (PAGE_SIZE - 1)];
}
EXPORT_SYMBOL(__genradix_iter_peek_prev);
static void genradix_free_recurse(struct genradix_node *n, unsigned level)
{
if (level) {