include/linux/flex_array.h

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