include/linux/flex_array.h

   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
  11 struct 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
  20 struct 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
  64 struct flex_array *flex_array_alloc(int element_size, unsigned int total,
  65                 gfp_t flags);
  66 int flex_array_prealloc(struct flex_array *fa, unsigned int start,
  67                 unsigned int nr_elements, gfp_t flags);
  68 void flex_array_free(struct flex_array *fa);
  69 void flex_array_free_parts(struct flex_array *fa);
  70 int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
  71                 gfp_t flags);
  72 int flex_array_clear(struct flex_array *fa, unsigned int element_nr);
  73 void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
  74 int 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
  79 void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr);
  80
  81 #endif /* _FLEX_ARRAY_H */