idr.c

Lib files of linux kernel

	n = idp->layers * IDR_BITS;
	p = idp->top;
	max = 1 << n;

	id = 0;
	while (id < max) {
		while (n > IDR_BITS && p) {
			n -= IDR_BITS;
			*paa++ = p;
			p = p->ary[(id >> n) & IDR_MASK];
		}

		id += 1 << n;
		while (n < fls(id)) {
			if (p)
				free_layer(p);
			n += IDR_BITS;
			p = *--paa;
		}
	}
	rcu_assign_pointer(idp->top, NULL);
	idp->layers = 0;
}
EXPORT_SYMBOL(idr_remove_all);

/**
 * idr_destroy - release all cached layers within an idr tree
 * idp: idr handle
 */
void idr_destroy(struct idr *idp)
{
	while (idp->id_free_cnt) {
		struct idr_layer *p = get_from_free_list(idp);
		kmem_cache_free(idr_layer_cache, p);
	}
}
EXPORT_SYMBOL(idr_destroy);

/**
 * idr_find - return pointer for given id
 * @idp: idr handle
 * @id: lookup key
 *
 * Return the pointer given the id it has been registered with.  A %NULL
 * return indicates that @id is not valid or you passed %NULL in
 * idr_get_new().
 *
 * This function can be called under rcu_read_lock(), given that the leaf
 * pointers lifetimes are correctly managed.
 */
void *idr_find(struct idr *idp, int id)
{
	int n;
	struct idr_layer *p;

	n = idp->layers * IDR_BITS;
	p = rcu_dereference(idp->top);

	/* Mask off upper bits we don't use for the search. */
	id &= MAX_ID_MASK;

	if (id >= (1 << n))
		return NULL;

	while (n > 0 && p) {
		n -= IDR_BITS;
		p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
	}
	return((void *)p);
}
EXPORT_SYMBOL(idr_find);

/**
 * idr_for_each - iterate through all stored pointers
 * @idp: idr handle
 * @fn: function to be called for each pointer
 * @data: data passed back to callback function
 *
 * Iterate over the pointers registered with the given idr.  The
 * callback function will be called for each pointer currently
 * registered, passing the id, the pointer and the data pointer passed
 * to this function.  It is not safe to modify the idr tree while in
 * the callback, so functions such as idr_get_new and idr_remove are
 * not allowed.
 *
 * We check the return of @fn each time. If it returns anything other
 * than 0, we break out and return that value.
 *
 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
 */
int idr_for_each(struct idr *idp,
		 int (*fn)(int id, void *p, void *data), void *data)
{
	int n, id, max, error = 0;
	struct idr_layer *p;
	struct idr_layer *pa[MAX_LEVEL];
	struct idr_layer **paa = &pa[0];

	n = idp->layers * IDR_BITS;
	p = rcu_dereference(idp->top);
	max = 1 << n;

	id = 0;
	while (id < max) {
		while (n > 0 && p) {
			n -= IDR_BITS;
			*paa++ = p;
			p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
		}

		if (p) {
			error = fn(id, (void *)p, data);
			if (error)
				break;
		}

		id += 1 << n;
		while (n < fls(id)) {
			n += IDR_BITS;
			p = *--paa;
		}
	}

	return error;
}
EXPORT_SYMBOL(idr_for_each);

/**
 * idr_replace - replace pointer for given id
 * @idp: idr handle
 * @ptr: pointer you want associated with the id
 * @id: lookup key
 *
 * Replace the pointer registered with an id and return the old value.
 * A -ENOENT return indicates that @id was not found.
 * A -EINVAL return indicates that @id was not within valid constraints.
 *
 * The caller must serialize with writers.
 */
void *idr_replace(struct idr *idp, void *ptr, int id)
{
	int n;
	struct idr_layer *p, *old_p;

	n = idp->layers * IDR_BITS;
	p = idp->top;

	id &= MAX_ID_MASK;

	if (id >= (1 << n))
		return ERR_PTR(-EINVAL);

	n -= IDR_BITS;
	while ((n > 0) && p) {
		p = p->ary[(id >> n) & IDR_MASK];
		n -= IDR_BITS;
	}

	n = id & IDR_MASK;
	if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
		return ERR_PTR(-ENOENT);

	old_p = p->ary[n];
	rcu_assign_pointer(p->ary[n], ptr);

	return old_p;
}
EXPORT_SYMBOL(idr_replace);

static void idr_cache_ctor(void *idr_layer)
{
	memset(idr_layer, 0, sizeof(struct idr_layer));
}

void __init idr_init_cache(void)
{
	idr_layer_cache = kmem_cache_create("idr_layer_cache",
				sizeof(struct idr_layer), 0, SLAB_PANIC,
				idr_cache_ctor);
}

/**
 * idr_init - initialize idr handle
 * @idp:	idr handle
 *
 * This function is use to set up the handle (@idp) that you will pass
 * to the rest of the functions.
 */
void idr_init(struct idr *idp)
{
	memset(idp, 0, sizeof(struct idr));
	spin_lock_init(&idp->lock);
}
EXPORT_SYMBOL(idr_init);


/*
 * IDA - IDR based ID allocator
 *
 * this is id allocator without id -> pointer translation.  Memory
 * usage is much lower than full blown idr because each id only
 * occupies a bit.  ida uses a custom leaf node which contains
 * IDA_BITMAP_BITS slots.
 *
 * 2007-04-25  written by Tejun Heo <[e-mail]>
 */

static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
{
	unsigned long flags;

	if (!ida->free_bitmap) {
		spin_lock_irqsave(&ida->idr.lock, flags);
		if (!ida->free_bitmap) {
			ida->free_bitmap = bitmap;
			bitmap = NULL;
		}
		spin_unlock_irqrestore(&ida->idr.lock, flags);
	}

	kfree(bitmap);
}

/**
 * ida_pre_get - reserve resources for ida allocation
 * @ida:	ida handle
 * @gfp_mask:	memory allocation flag
 *
 * This function should be called prior to locking and calling the
 * following function.  It preallocates enough memory to satisfy the
 * worst possible allocation.
 *
 * If the system is REALLY out of memory this function returns 0,
 * otherwise 1.
 */
int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
{
	/* allocate idr_layers */
	if (!idr_pre_get(&ida->idr, gfp_mask))
		return 0;

	/* allocate free_bitmap */
	if (!ida->free_bitmap) {
		struct ida_bitmap *bitmap;

		bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
		if (!bitmap)
			return 0;

		free_bitmap(ida, bitmap);
	}

	return 1;
}
EXPORT_SYMBOL(ida_pre_get);

/**
 * ida_get_new_above - allocate new ID above or equal to a start id
 * @ida:	ida handle
 * @staring_id:	id to start search at
 * @p_id:	pointer to the allocated handle
 *
 * Allocate new ID above or equal to @ida.  It should be called with
 * any required locks.
 *
 * If memory is required, it will return -EAGAIN, you should unlock
 * and go back to the ida_pre_get() call.  If the ida is full, it will
 * return -ENOSPC.
 *
 * @p_id returns a value in the range 0 ... 0x7fffffff.
 */
int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
{
	struct idr_layer *pa[MAX_LEVEL];
	struct ida_bitmap *bitmap;
	unsigned long flags;
	int idr_id = starting_id / IDA_BITMAP_BITS;
	int offset = starting_id % IDA_BITMAP_BITS;
	int t, id;

 restart:
	/* get vacant slot */
	t = idr_get_empty_slot(&ida->idr, idr_id, pa);
	if (t < 0)
		return _idr_rc_to_errno(t);

	if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
		return -ENOSPC;

	if (t != idr_id)
		offset = 0;
	idr_id = t;

	/* if bitmap isn't there, create a new one */
	bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
	if (!bitmap) {
		spin_lock_irqsave(&ida->idr.lock, flags);
		bitmap = ida->free_bitmap;
		ida->free_bitmap = NULL;
		spin_unlock_irqrestore(&ida->idr.lock, flags);

		if (!bitmap)
			return -EAGAIN;

		memset(bitmap, 0, sizeof(struct ida_bitmap));
		rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
				(void *)bitmap);
		pa[0]->count++;
	}

	/* lookup for empty slot */
	t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
	if (t == IDA_BITMAP_BITS) {
		/* no empty slot after offset, continue to the next chunk */
		idr_id++;
		offset = 0;
		goto restart;
	}

	id = idr_id * IDA_BITMAP_BITS + t;
	if (id >= MAX_ID_BIT)
		return -ENOSPC;

	__set_bit(t, bitmap->bitmap);
	if (++bitmap->nr_busy == IDA_BITMAP_BITS)
		idr_mark_full(pa, idr_id);

	*p_id = id;

	/* Each leaf node can handle nearly a thousand slots and the
	 * whole idea of ida is to have small memory foot print.
	 * Throw away extra resources one by one after each successful
	 * allocation.
	 */
	if (ida->idr.id_free_cnt || ida->free_bitmap) {
		struct idr_layer *p = get_from_free_list(&ida->idr);
		if (p)
			kmem_cache_free(idr_layer_cache, p);
	}

	return 0;
}
EXPORT_SYMBOL(ida_get_new_above);

/**
 * ida_get_new - allocate new ID
 * @ida:	idr handle
 * @p_id:	pointer to the allocated handle
 *
 * Allocate new ID.  It should be called with any required locks.
 *
 * If memory is required, it will return -EAGAIN, you should unlock
 * and go back to the idr_pre_get() call.  If the idr is full, it will
 * return -ENOSPC.
 *
 * @id returns a value in the range 0 ... 0x7fffffff.
 */
int ida_get_new(struct ida *ida, int *p_id)
{
	return ida_get_new_above(ida, 0, p_id);
}
EXPORT_SYMBOL(ida_get_new);

/**
 * ida_remove - remove the given ID
 * @ida:	ida handle
 * @id:		ID to free
 */
void ida_remove(struct ida *ida, int id)
{
	struct idr_layer *p = ida->idr.top;
	int shift = (ida->idr.layers - 1) * IDR_BITS;
	int idr_id = id / IDA_BITMAP_BITS;
	int offset = id % IDA_BITMAP_BITS;
	int n;
	struct ida_bitmap *bitmap;

	/* clear full bits while looking up the leaf idr_layer */
	while ((shift > 0) && p) {
		n = (idr_id >> shift) & IDR_MASK;
		__clear_bit(n, &p->bitmap);
		p = p->ary[n];
		shift -= IDR_BITS;
	}

	if (p == NULL)
		goto err;

	n = idr_id & IDR_MASK;
	__clear_bit(n, &p->bitmap);

	bitmap = (void *)p->ary[n];
	if (!test_bit(offset, bitmap->bitmap))
		goto err;

	/* update bitmap and remove it if empty */
	__clear_bit(offset, bitmap->bitmap);
	if (--bitmap->nr_busy == 0) {
		__set_bit(n, &p->bitmap);	/* to please idr_remove() */
		idr_remove(&ida->idr, idr_id);
		free_bitmap(ida, bitmap);
	}

	return;

 err:
	printk(KERN_WARNING
	       "ida_remove called for id=%d which is not allocated.\n", id);
}
EXPORT_SYMBOL(ida_remove);

/**
 * ida_destroy - release all cached layers within an ida tree
 * ida:		ida handle
 */
void ida_destroy(struct ida *ida)
{
	idr_destroy(&ida->idr);
	kfree(ida->free_bitmap);
}
EXPORT_SYMBOL(ida_destroy);

/**
 * ida_init - initialize ida handle
 * @ida:	ida handle
 *
 * This function is use to set up the handle (@ida) that you will pass
 * to the rest of the functions.
 */
void ida_init(struct ida *ida)
{
	memset(ida, 0, sizeof(struct ida));
	idr_init(&ida->idr);

}
EXPORT_SYMBOL(ida_init);