1#ifndef _FLEX_ARRAY_H
2#define _FLEX_ARRAY_H
3
4#include <linux/types.h>
5#include <linux/reciprocal_div.h>
6#include <asm/page.h>
7
8#define FLEX_ARRAY_PART_SIZE PAGE_SIZE
9#define FLEX_ARRAY_BASE_SIZE PAGE_SIZE
10
11struct flex_array_part;
12
13/*
14 * This is meant to replace cases where an array-like
15 * structure has gotten too big to fit into kmalloc()
16 * and the developer is getting tempted to use
17 * vmalloc().
18 */
19
20struct flex_array {
21	union {
22		struct {
23			int element_size;
24			int total_nr_elements;
25			int elems_per_part;
26			struct reciprocal_value reciprocal_elems;
27			struct flex_array_part *parts[];
28		};
29		/*
30		 * This little trick makes sure that
31		 * sizeof(flex_array) == PAGE_SIZE
32		 */
33		char padding[FLEX_ARRAY_BASE_SIZE];
34	};
35};
36
37/* Number of bytes left in base struct flex_array, excluding metadata */
38#define FLEX_ARRAY_BASE_BYTES_LEFT					\
39	(FLEX_ARRAY_BASE_SIZE - offsetof(struct flex_array, parts))
40
41/* Number of pointers in base to struct flex_array_part pages */
42#define FLEX_ARRAY_NR_BASE_PTRS						\
43	(FLEX_ARRAY_BASE_BYTES_LEFT / sizeof(struct flex_array_part *))
44
45/* Number of elements of size that fit in struct flex_array_part */
46#define FLEX_ARRAY_ELEMENTS_PER_PART(size)				\
47	(FLEX_ARRAY_PART_SIZE / size)
48
49/*
50 * Defines a statically allocated flex array and ensures its parameters are
51 * valid.
52 */
53#define DEFINE_FLEX_ARRAY(__arrayname, __element_size, __total)		\
54	struct flex_array __arrayname = { { {				\
55		.element_size = (__element_size),			\
56		.total_nr_elements = (__total),				\
57	} } };								\
58	static inline void __arrayname##_invalid_parameter(void)	\
59	{								\
60		BUILD_BUG_ON((__total) > FLEX_ARRAY_NR_BASE_PTRS *	\
61			FLEX_ARRAY_ELEMENTS_PER_PART(__element_size));	\
62	}
63
64struct flex_array *flex_array_alloc(int element_size, unsigned int total,
65		gfp_t flags);
66int flex_array_prealloc(struct flex_array *fa, unsigned int start,
67		unsigned int nr_elements, gfp_t flags);
68void flex_array_free(struct flex_array *fa);
69void flex_array_free_parts(struct flex_array *fa);
70int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
71		gfp_t flags);
72int flex_array_clear(struct flex_array *fa, unsigned int element_nr);
73void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
74int flex_array_shrink(struct flex_array *fa);
75
76#define flex_array_put_ptr(fa, nr, src, gfp) \
77	flex_array_put(fa, nr, (void *)&(src), gfp)
78
79void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr);
80
81#endif /* _FLEX_ARRAY_H */
82