rhashtable: add function to replace an element

	return err;

}

/* Internal function, please use rhashtable_replace_fast() instead */

static inline int __rhashtable_replace_fast(

	struct rhashtable *ht, struct bucket_table *tbl,

	struct rhash_head *obj_old, struct rhash_head *obj_new,

	const struct rhashtable_params params)

{

	struct rhash_head __rcu **pprev;

	struct rhash_head *he;

	spinlock_t *lock;

	unsigned int hash;

	int err = -ENOENT;

	/* Minimally, the old and new objects must have same hash

	 * (which should mean identifiers are the same).

	 */

	hash = rht_head_hashfn(ht, tbl, obj_old, params);

	if (hash != rht_head_hashfn(ht, tbl, obj_new, params))

		return -EINVAL;

	lock = rht_bucket_lock(tbl, hash);

	spin_lock_bh(lock);

	pprev = &tbl->buckets[hash];

	rht_for_each(he, tbl, hash) {

		if (he != obj_old) {

			pprev = &he->next;

			continue;

		}

		rcu_assign_pointer(obj_new->next, obj_old->next);

		rcu_assign_pointer(*pprev, obj_new);

		err = 0;

		break;

	}

	spin_unlock_bh(lock);

	return err;

}

/**

 * rhashtable_replace_fast - replace an object in hash table

 * @ht:		hash table

 * @obj_old:	pointer to hash head inside object being replaced

 * @obj_new:	pointer to hash head inside object which is new

 * @params:	hash table parameters

 *

 * Replacing an object doesn't affect the number of elements in the hash table

 * or bucket, so we don't need to worry about shrinking or expanding the

 * table here.

 *

 * Returns zero on success, -ENOENT if the entry could not be found,

 * -EINVAL if hash is not the same for the old and new objects.

 */

static inline int rhashtable_replace_fast(

	struct rhashtable *ht, struct rhash_head *obj_old,

	struct rhash_head *obj_new,

	const struct rhashtable_params params)

{

	struct bucket_table *tbl;

	int err;

	rcu_read_lock();

	tbl = rht_dereference_rcu(ht->tbl, ht);

	/* Because we have already taken (and released) the bucket

	 * lock in old_tbl, if we find that future_tbl is not yet

	 * visible then that guarantees the entry to still be in

	 * the old tbl if it exists.

	 */

	while ((err = __rhashtable_replace_fast(ht, tbl, obj_old,

						obj_new, params)) &&

	       (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))

		;

	rcu_read_unlock();

	return err;

}

#endif /* _LINUX_RHASHTABLE_H */