root/include/linux/slab_def.h

INCLUDED FROM

DEFINITIONS

1. nearest_obj
2. obj_to_index

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_SLAB_DEF_H
   3 #define _LINUX_SLAB_DEF_H
   4 
   5 #include <linux/reciprocal_div.h>
   6 
   7 /*
   8  * Definitions unique to the original Linux SLAB allocator.
   9  */
  10 
  11 struct kmem_cache {
  12         struct array_cache __percpu *cpu_cache;
  13 
  14 /* 1) Cache tunables. Protected by slab_mutex */
  15         unsigned int batchcount;
  16         unsigned int limit;
  17         unsigned int shared;
  18 
  19         unsigned int size;
  20         struct reciprocal_value reciprocal_buffer_size;
  21 /* 2) touched by every alloc & free from the backend */
  22 
  23         slab_flags_t flags;             /* constant flags */
  24         unsigned int num;               /* # of objs per slab */
  25 
  26 /* 3) cache_grow/shrink */
  27         /* order of pgs per slab (2^n) */
  28         unsigned int gfporder;
  29 
  30         /* force GFP flags, e.g. GFP_DMA */
  31         gfp_t allocflags;
  32 
  33         size_t colour;                  /* cache colouring range */
  34         unsigned int colour_off;        /* colour offset */
  35         struct kmem_cache *freelist_cache;
  36         unsigned int freelist_size;
  37 
  38         /* constructor func */
  39         void (*ctor)(void *obj);
  40 
  41 /* 4) cache creation/removal */
  42         const char *name;
  43         struct list_head list;
  44         int refcount;
  45         int object_size;
  46         int align;
  47 
  48 /* 5) statistics */
  49 #ifdef CONFIG_DEBUG_SLAB
  50         unsigned long num_active;
  51         unsigned long num_allocations;
  52         unsigned long high_mark;
  53         unsigned long grown;
  54         unsigned long reaped;
  55         unsigned long errors;
  56         unsigned long max_freeable;
  57         unsigned long node_allocs;
  58         unsigned long node_frees;
  59         unsigned long node_overflow;
  60         atomic_t allochit;
  61         atomic_t allocmiss;
  62         atomic_t freehit;
  63         atomic_t freemiss;
  64 
  65         /*
  66          * If debugging is enabled, then the allocator can add additional
  67          * fields and/or padding to every object. 'size' contains the total
  68          * object size including these internal fields, while 'obj_offset'
  69          * and 'object_size' contain the offset to the user object and its
  70          * size.
  71          */
  72         int obj_offset;
  73 #endif /* CONFIG_DEBUG_SLAB */
  74 
  75 #ifdef CONFIG_MEMCG
  76         struct memcg_cache_params memcg_params;
  77 #endif
  78 #ifdef CONFIG_KASAN
  79         struct kasan_cache kasan_info;
  80 #endif
  81 
  82 #ifdef CONFIG_SLAB_FREELIST_RANDOM
  83         unsigned int *random_seq;
  84 #endif
  85 
  86         unsigned int useroffset;        /* Usercopy region offset */
  87         unsigned int usersize;          /* Usercopy region size */
  88 
  89         struct kmem_cache_node *node[MAX_NUMNODES];
  90 };
  91 
  92 static inline void *nearest_obj(struct kmem_cache *cache, struct page *page,
  93                                 void *x)
  94 {
  95         void *object = x - (x - page->s_mem) % cache->size;
  96         void *last_object = page->s_mem + (cache->num - 1) * cache->size;
  97 
  98         if (unlikely(object > last_object))
  99                 return last_object;
 100         else
 101                 return object;
 102 }
 103 
 104 /*
 105  * We want to avoid an expensive divide : (offset / cache->size)
 106  *   Using the fact that size is a constant for a particular cache,
 107  *   we can replace (offset / cache->size) by
 108  *   reciprocal_divide(offset, cache->reciprocal_buffer_size)
 109  */
 110 static inline unsigned int obj_to_index(const struct kmem_cache *cache,
 111                                         const struct page *page, void *obj)
 112 {
 113         u32 offset = (obj - page->s_mem);
 114         return reciprocal_divide(offset, cache->reciprocal_buffer_size);
 115 }
 116 
 117 #endif  /* _LINUX_SLAB_DEF_H */