xfs_mru_cache.c

linux 内核源代码

}

int
xfs_mru_cache_init(void)
{
	xfs_mru_elem_zone = kmem_zone_init(sizeof(xfs_mru_cache_elem_t),
	                                 "xfs_mru_cache_elem");
	if (!xfs_mru_elem_zone)
		return ENOMEM;

	xfs_mru_reap_wq = create_singlethread_workqueue("xfs_mru_cache");
	if (!xfs_mru_reap_wq) {
		kmem_zone_destroy(xfs_mru_elem_zone);
		return ENOMEM;
	}

	return 0;
}

void
xfs_mru_cache_uninit(void)
{
	destroy_workqueue(xfs_mru_reap_wq);
	kmem_zone_destroy(xfs_mru_elem_zone);
}

/*
 * To initialise a struct xfs_mru_cache pointer, call xfs_mru_cache_create()
 * with the address of the pointer, a lifetime value in milliseconds, a group
 * count and a free function to use when deleting elements.  This function
 * returns 0 if the initialisation was successful.
 */
int
xfs_mru_cache_create(
	xfs_mru_cache_t		**mrup,
	unsigned int		lifetime_ms,
	unsigned int		grp_count,
	xfs_mru_cache_free_func_t free_func)
{
	xfs_mru_cache_t	*mru = NULL;
	int		err = 0, grp;
	unsigned int	grp_time;

	if (mrup)
		*mrup = NULL;

	if (!mrup || !grp_count || !lifetime_ms || !free_func)
		return EINVAL;

	if (!(grp_time = msecs_to_jiffies(lifetime_ms) / grp_count))
		return EINVAL;

	if (!(mru = kmem_zalloc(sizeof(*mru), KM_SLEEP)))
		return ENOMEM;

	/* An extra list is needed to avoid reaping up to a grp_time early. */
	mru->grp_count = grp_count + 1;
	mru->lists = kmem_zalloc(mru->grp_count * sizeof(*mru->lists), KM_SLEEP);

	if (!mru->lists) {
		err = ENOMEM;
		goto exit;
	}

	for (grp = 0; grp < mru->grp_count; grp++)
		INIT_LIST_HEAD(mru->lists + grp);

	/*
	 * We use GFP_KERNEL radix tree preload and do inserts under a
	 * spinlock so GFP_ATOMIC is appropriate for the radix tree itself.
	 */
	INIT_RADIX_TREE(&mru->store, GFP_ATOMIC);
	INIT_LIST_HEAD(&mru->reap_list);
	spinlock_init(&mru->lock, "xfs_mru_cache");
	INIT_DELAYED_WORK(&mru->work, _xfs_mru_cache_reap);

	mru->grp_time  = grp_time;
	mru->free_func = free_func;

	*mrup = mru;

exit:
	if (err && mru && mru->lists)
		kmem_free(mru->lists, mru->grp_count * sizeof(*mru->lists));
	if (err && mru)
		kmem_free(mru, sizeof(*mru));

	return err;
}

/*
 * Call xfs_mru_cache_flush() to flush out all cached entries, calling their
 * free functions as they're deleted.  When this function returns, the caller is
 * guaranteed that all the free functions for all the elements have finished
 * executing and the reaper is not running.
 */
void
xfs_mru_cache_flush(
	xfs_mru_cache_t		*mru)
{
	if (!mru || !mru->lists)
		return;

	mutex_spinlock(&mru->lock);
	if (mru->queued) {
		mutex_spinunlock(&mru->lock, 0);
		cancel_rearming_delayed_workqueue(xfs_mru_reap_wq, &mru->work);
		mutex_spinlock(&mru->lock);
	}

	_xfs_mru_cache_migrate(mru, jiffies + mru->grp_count * mru->grp_time);
	_xfs_mru_cache_clear_reap_list(mru);

	mutex_spinunlock(&mru->lock, 0);
}

void
xfs_mru_cache_destroy(
	xfs_mru_cache_t		*mru)
{
	if (!mru || !mru->lists)
		return;

	xfs_mru_cache_flush(mru);

	kmem_free(mru->lists, mru->grp_count * sizeof(*mru->lists));
	kmem_free(mru, sizeof(*mru));
}

/*
 * To insert an element, call xfs_mru_cache_insert() with the data store, the
 * element's key and the client data pointer.  This function returns 0 on
 * success or ENOMEM if memory for the data element couldn't be allocated.
 */
int
xfs_mru_cache_insert(
	xfs_mru_cache_t	*mru,
	unsigned long	key,
	void		*value)
{
	xfs_mru_cache_elem_t *elem;

	ASSERT(mru && mru->lists);
	if (!mru || !mru->lists)
		return EINVAL;

	elem = kmem_zone_zalloc(xfs_mru_elem_zone, KM_SLEEP);
	if (!elem)
		return ENOMEM;

	if (radix_tree_preload(GFP_KERNEL)) {
		kmem_zone_free(xfs_mru_elem_zone, elem);
		return ENOMEM;
	}

	INIT_LIST_HEAD(&elem->list_node);
	elem->key = key;
	elem->value = value;

	mutex_spinlock(&mru->lock);

	radix_tree_insert(&mru->store, key, elem);
	radix_tree_preload_end();
	_xfs_mru_cache_list_insert(mru, elem);

	mutex_spinunlock(&mru->lock, 0);

	return 0;
}

/*
 * To remove an element without calling the free function, call
 * xfs_mru_cache_remove() with the data store and the element's key.  On success
 * the client data pointer for the removed element is returned, otherwise this
 * function will return a NULL pointer.
 */
void *
xfs_mru_cache_remove(
	xfs_mru_cache_t	*mru,
	unsigned long	key)
{
	xfs_mru_cache_elem_t *elem;
	void		*value = NULL;

	ASSERT(mru && mru->lists);
	if (!mru || !mru->lists)
		return NULL;

	mutex_spinlock(&mru->lock);
	elem = radix_tree_delete(&mru->store, key);
	if (elem) {
		value = elem->value;
		list_del(&elem->list_node);
	}

	mutex_spinunlock(&mru->lock, 0);

	if (elem)
		kmem_zone_free(xfs_mru_elem_zone, elem);

	return value;
}

/*
 * To remove and element and call the free function, call xfs_mru_cache_delete()
 * with the data store and the element's key.
 */
void
xfs_mru_cache_delete(
	xfs_mru_cache_t	*mru,
	unsigned long	key)
{
	void		*value = xfs_mru_cache_remove(mru, key);

	if (value)
		mru->free_func(key, value);
}

/*
 * To look up an element using its key, call xfs_mru_cache_lookup() with the
 * data store and the element's key.  If found, the element will be moved to the
 * head of the MRU list to indicate that it's been touched.
 *
 * The internal data structures are protected by a spinlock that is STILL HELD
 * when this function returns.  Call xfs_mru_cache_done() to release it.  Note
 * that it is not safe to call any function that might sleep in the interim.
 *
 * The implementation could have used reference counting to avoid this
 * restriction, but since most clients simply want to get, set or test a member
 * of the returned data structure, the extra per-element memory isn't warranted.
 *
 * If the element isn't found, this function returns NULL and the spinlock is
 * released.  xfs_mru_cache_done() should NOT be called when this occurs.
 */
void *
xfs_mru_cache_lookup(
	xfs_mru_cache_t	*mru,
	unsigned long	key)
{
	xfs_mru_cache_elem_t *elem;

	ASSERT(mru && mru->lists);
	if (!mru || !mru->lists)
		return NULL;

	mutex_spinlock(&mru->lock);
	elem = radix_tree_lookup(&mru->store, key);
	if (elem) {
		list_del(&elem->list_node);
		_xfs_mru_cache_list_insert(mru, elem);
	}
	else
		mutex_spinunlock(&mru->lock, 0);

	return elem ? elem->value : NULL;
}

/*
 * To look up an element using its key, but leave its location in the internal
 * lists alone, call xfs_mru_cache_peek().  If the element isn't found, this
 * function returns NULL.
 *
 * See the comments above the declaration of the xfs_mru_cache_lookup() function
 * for important locking information pertaining to this call.
 */
void *
xfs_mru_cache_peek(
	xfs_mru_cache_t	*mru,
	unsigned long	key)
{
	xfs_mru_cache_elem_t *elem;

	ASSERT(mru && mru->lists);
	if (!mru || !mru->lists)
		return NULL;

	mutex_spinlock(&mru->lock);
	elem = radix_tree_lookup(&mru->store, key);
	if (!elem)
		mutex_spinunlock(&mru->lock, 0);

	return elem ? elem->value : NULL;
}

/*
 * To release the internal data structure spinlock after having performed an
 * xfs_mru_cache_lookup() or an xfs_mru_cache_peek(), call xfs_mru_cache_done()
 * with the data store pointer.
 */
void
xfs_mru_cache_done(
	xfs_mru_cache_t	*mru)
{
	mutex_spinunlock(&mru->lock, 0);
}