linux-imx

#include <linux/spinlock.h>

#include <linux/slab.h>

#include <linux/list.h>

#include <linux/list_bl.h>

#include <linux/module.h>

#include <linux/sched.h>

#include <linux/workqueue.h>

#include <linux/mbcache.h>

​

/*

 * Mbcache is a simple key-value store. Keys need not be unique, however

 * key-value pairs are expected to be unique (we use this fact in

 * mb_cache_entry_delete()).

 *

 * Ext2 and ext4 use this cache for deduplication of extended attribute blocks.

 * Ext4 also uses it for deduplication of xattr values stored in inodes.

 * They use hash of data as a key and provide a value that may represent a

 * block or inode number. That's why keys need not be unique (hash of different

 * data may be the same). However user provided value always uniquely

 * identifies a cache entry.

 *

 * We provide functions for creation and removal of entries, search by key,

 * and a special "delete entry with given key-value pair" operation. Fixed

 * size hash table is used for fast key lookups.

 */

​

struct mb_cache {

    /* Hash table of entries */

    struct hlist_bl_head    *c_hash;

    /* log2 of hash table size */

    int         c_bucket_bits;

    /* Maximum entries in cache to avoid degrading hash too much */

    unsigned long       c_max_entries;

    /* Protects c_list, c_entry_count */

    spinlock_t      c_list_lock;

    struct list_head    c_list;

    /* Number of entries in cache */

    unsigned long       c_entry_count;

    struct shrinker     c_shrink;

    /* Work for shrinking when the cache has too many entries */

    struct work_struct  c_shrink_work;

};

​

static struct kmem_cache *mb_entry_cache;

​

static unsigned long mb_cache_shrink(struct mb_cache *cache,

                     unsigned long nr_to_scan);

​

static inline struct hlist_bl_head *mb_cache_entry_head(struct mb_cache *cache,

                            u32 key)

{

    return &cache->c_hash[hash_32(key, cache->c_bucket_bits)];

}

​

/*

 * Number of entries to reclaim synchronously when there are too many entries

 * in cache

 */

#define SYNC_SHRINK_BATCH 64

​

/*

 * mb_cache_entry_create - create entry in cache

 * @cache - cache where the entry should be created