/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MBCACHE_H
#define _LINUX_MBCACHE_H

#include <linux/hash.h>
#include <linux/list_bl.h>
#include <linux/list.h>
#include <linux/atomic.h>
#include <linux/fs.h>

struct mb_cache;

/* Cache entry flags */
enum {
        MBE_REFERENCED_B = 0,
        MBE_REUSABLE_B
};

struct mb_cache_entry {
        /* List of entries in cache - protected by cache->c_list_lock */
        struct list_head        e_list;
        /*
         * Hash table list - protected by hash chain bitlock. The entry is
         * guaranteed to be hashed while e_refcnt > 0.
         */
        struct hlist_bl_node    e_hash_list;
        /*
         * Entry refcount. Once it reaches zero, entry is unhashed and freed.
         * While refcount > 0, the entry is guaranteed to stay in the hash and
         * e.g. mb_cache_entry_try_delete() will fail.
         */
        atomic_t                e_refcnt;
        /* Key in hash - stable during lifetime of the entry */
        u32                     e_key;
        unsigned long           e_flags;
        /* User provided value - stable during lifetime of the entry */
        u64                     e_value;
};

struct mb_cache *mb_cache_create(int bucket_bits);
void mb_cache_destroy(struct mb_cache *cache);

int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key,
                          u64 value, bool reusable);
void __mb_cache_entry_free(struct mb_cache *cache,
                           struct mb_cache_entry *entry);
void mb_cache_entry_wait_unused(struct mb_cache_entry *entry);
static inline void mb_cache_entry_put(struct mb_cache *cache,
                                      struct mb_cache_entry *entry)
{
        unsigned int cnt = atomic_dec_return(&entry->e_refcnt);

        if (cnt > 0) {
                if (cnt <= 2)
                        wake_up_var(&entry->e_refcnt);
                return;
        }
        __mb_cache_entry_free(cache, entry);
}

struct mb_cache_entry *mb_cache_entry_delete_or_get(struct mb_cache *cache,
                                                    u32 key, u64 value);
struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key,
                                          u64 value);
struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache,
                                                 u32 key);
struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache,
                                                struct mb_cache_entry *entry);
void mb_cache_entry_touch(struct mb_cache *cache,
                          struct mb_cache_entry *entry);

#endif  /* _LINUX_MBCACHE_H */