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                         int elems_per_part;
  25                         u32 reciprocal_elems;
  26                         struct flex_array_part *parts[];
  27                 };
  28                 /*
  29                  * This little trick makes sure that
  30                  * sizeof(flex_array) == PAGE_SIZE
  31                  */
  32                 char padding[FLEX_ARRAY_BASE_SIZE];
  33         };
  34 };
  35
  36 /* Number of bytes left in base struct flex_array, excluding metadata */
  37 #define FLEX_ARRAY_BASE_BYTES_LEFT                                      \
  38         (FLEX_ARRAY_BASE_SIZE - offsetof(struct flex_array, parts))
  39
  40 /* Number of pointers in base to struct flex_array_part pages */
  41 #define FLEX_ARRAY_NR_BASE_PTRS                                         \
  42         (FLEX_ARRAY_BASE_BYTES_LEFT / sizeof(struct flex_array_part *))
  43
  44 /* Number of elements of size that fit in struct flex_array_part */
  45 #define FLEX_ARRAY_ELEMENTS_PER_PART(size)                              \
  46         (FLEX_ARRAY_PART_SIZE / size)
  47
  48 /*
  49  * Defines a statically allocated flex array and ensures its parameters are
  50  * valid.
  51  */
  52 #define DEFINE_FLEX_ARRAY(__arrayname, __element_size, __total)         \
  53         struct flex_array __arrayname = { { {                           \
  54                 .element_size = (__element_size),                       \
  55                 .total_nr_elements = (__total),                         \
  56         } } };                                                          \
  57         static inline void __arrayname##_invalid_parameter(void)        \
  58         {                                                               \
  59                 BUILD_BUG_ON((__total) > FLEX_ARRAY_NR_BASE_PTRS *      \
  60                         FLEX_ARRAY_ELEMENTS_PER_PART(__element_size));  \
  61         }
  62
  63 struct flex_array *flex_array_alloc(int element_size, unsigned int total,
  64                 gfp_t flags);
  65 int flex_array_prealloc(struct flex_array *fa, unsigned int start,
  66                 unsigned int nr_elements, gfp_t flags);
  67 void flex_array_free(struct flex_array *fa);
  68 void flex_array_free_parts(struct flex_array *fa);
  69 int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
  70                 gfp_t flags);
  71 int flex_array_clear(struct flex_array *fa, unsigned int element_nr);
  72 void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
  73 int flex_array_shrink(struct flex_array *fa);
  74
  75 #define flex_array_put_ptr(fa, nr, src, gfp) \
  76         flex_array_put(fa, nr, (void *)&(src), gfp)
  77
  78 void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr);
  79
  80 #endif /* _FLEX_ARRAY_H */