// include/linux/slab_def.h
struct kmem_cache {
        struct array_cache __percpu *cpu_cache;

/* 1) Cache tunables. Protected by slab_mutex */
        unsigned int batchcount;
        unsigned int limit;
        unsigned int shared;

        unsigned int size;
        struct reciprocal_value reciprocal_buffer_size;
/* 2) touched by every alloc & free from the backend */

        slab_flags_t flags;             /* constant flags */
        unsigned int num;               /* # of objs per slab */

/* 3) cache_grow/shrink */
        /* order of pgs per slab (2^n) */
        unsigned int gfporder;

        /* force GFP flags, e.g. GFP_DMA */
        gfp_t allocflags;

        size_t colour;                  /* cache colouring range */
        unsigned int colour_off;        /* colour offset */
        struct kmem_cache *freelist_cache;
        unsigned int freelist_size;

        /* constructor func */
        void (*ctor)(void *obj);

/* 4) cache creation/removal */
        const char *name;
        struct list_head list;
        int refcount;
        int object_size;
        int align;

/* 5) statistics */
#ifdef CONFIG_DEBUG_SLAB
        unsigned long num_active;
        unsigned long num_allocations;
        unsigned long high_mark;
        unsigned long grown;
        unsigned long reaped;
        unsigned long errors;
        unsigned long max_freeable;
        unsigned long node_allocs;
        unsigned long node_frees;
        unsigned long node_overflow;
        atomic_t allochit;
        atomic_t allocmiss;
        atomic_t freehit;
        atomic_t freemiss;
#ifdef CONFIG_DEBUG_SLAB_LEAK
        atomic_t store_user_clean;
#endif

        /*
         * If debugging is enabled, then the allocator can add additional
         * fields and/or padding to every object. 'size' contains the total
         * object size including these internal fields, while 'obj_offset'
         * and 'object_size' contain the offset to the user object and its
         * size.
         */
        int obj_offset;
#endif /* CONFIG_DEBUG_SLAB */

#ifdef CONFIG_MEMCG
        struct memcg_cache_params memcg_params;
#endif
#ifdef CONFIG_KASAN
        struct kasan_cache kasan_info;
#endif

#ifdef CONFIG_SLAB_FREELIST_RANDOM
        unsigned int *random_seq;
#endif

        unsigned int useroffset;        /* Usercopy region offset */
        unsigned int usersize;          /* Usercopy region size */

        struct kmem_cache_node *node[MAX_NUMNODES];
};

struct kmem_cache_node {
        spinlock_t list_lock;

#ifdef CONFIG_SLAB
        struct list_head slabs_partial; /* partial list first, better asm code */
        struct list_head slabs_full;
        struct list_head slabs_free;
        unsigned long total_slabs;      /* length of all slab lists */
        unsigned long free_slabs;       /* length of free slab list only */
        unsigned long free_objects;
        unsigned int free_limit;
        unsigned int colour_next;       /* Per-node cache coloring */
        struct array_cache *shared;     /* shared per node */
        struct alien_cache **alien;     /* on other nodes */
        unsigned long next_reap;        /* updated without locking */
        int free_touched;               /* updated without locking */
#endif

#ifdef CONFIG_SLUB
        unsigned long nr_partial;
        struct list_head partial;
#ifdef CONFIG_SLUB_DEBUG
        atomic_long_t nr_slabs;
        atomic_long_t total_objects;
        struct list_head full;
#endif
#endif

};

static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
{
        return s->node[node];
}