[net-next-2.6.git] / lib / idr.c

/*
 * 2002-10-18  written by Jim Houston jim.houston@ccur.com
 *	Copyright (C) 2002 by Concurrent Computer Corporation
 *	Distributed under the GNU GPL license version 2.
 *
 * Modified by George Anzinger to reuse immediately and to use
 * find bit instructions.  Also removed _irq on spinlocks.
 *
 * Small id to pointer translation service.
 *
 * It uses a radix tree like structure as a sparse array indexed
 * by the id to obtain the pointer.  The bitmap makes allocating
 * a new id quick.
 *
 * You call it to allocate an id (an int) an associate with that id a
 * pointer or what ever, we treat it as a (void *).  You can pass this
 * id to a user for him to pass back at a later time.  You then pass
 * that id to this code and it returns your pointer.

 * You can release ids at any time. When all ids are released, most of
 * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
 * don't need to go to the memory "store" during an id allocate, just
 * so you don't need to be too concerned about locking and conflicts
 * with the slab allocator.
 */

#ifndef TEST                        // to test in user space...
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#endif
#include <linux/string.h>
#include <linux/idr.h>

static kmem_cache_t *idr_layer_cache;

static struct idr_layer *alloc_layer(struct idr *idp)
{
	struct idr_layer *p;

	spin_lock(&idp->lock);
	if ((p = idp->id_free)) {
		idp->id_free = p->ary[0];
		idp->id_free_cnt--;
		p->ary[0] = NULL;
	}
	spin_unlock(&idp->lock);
	return(p);
}

/* only called when idp->lock is held */
static void __free_layer(struct idr *idp, struct idr_layer *p)
{
	p->ary[0] = idp->id_free;
	idp->id_free = p;
	idp->id_free_cnt++;
}

static void free_layer(struct idr *idp, struct idr_layer *p)
{
	/*
	 * Depends on the return element being zeroed.
	 */
	spin_lock(&idp->lock);
	__free_layer(idp, p);
	spin_unlock(&idp->lock);
}

/**
 * idr_pre_get - reserver resources for idr allocation
 * @idp:	idr handle
 * @gfp_mask:	memory allocation flags
 *
 * 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 idr_pre_get(struct idr *idp, gfp_t gfp_mask)
{
	while (idp->id_free_cnt < IDR_FREE_MAX) {
		struct idr_layer *new;
		new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
		if (new == NULL)
			return (0);
		free_layer(idp, new);
	}
	return 1;
}
EXPORT_SYMBOL(idr_pre_get);

static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
{
	int n, m, sh;
	struct idr_layer *p, *new;
	struct idr_layer *pa[MAX_LEVEL];
	int l, id;
	long bm;

	id = *starting_id;
	p = idp->top;
	l = idp->layers;
	pa[l--] = NULL;
	while (1) {
		/*
		 * We run around this while until we reach the leaf node...
		 */
		n = (id >> (IDR_BITS*l)) & IDR_MASK;
		bm = ~p->bitmap;
		m = find_next_bit(&bm, IDR_SIZE, n);
		if (m == IDR_SIZE) {
			/* no space available go back to previous layer. */
			l++;
			id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
			if (!(p = pa[l])) {
				*starting_id = id;
				return -2;
			}
			continue;
		}
		if (m != n) {
			sh = IDR_BITS*l;
			id = ((id >> sh) ^ n ^ m) << sh;
		}
		if ((id >= MAX_ID_BIT) || (id < 0))
			return -3;
		if (l == 0)
			break;
		/*
		 * Create the layer below if it is missing.
		 */
		if (!p->ary[m]) {
			if (!(new = alloc_layer(idp)))
				return -1;
			p->ary[m] = new;
			p->count++;
		}
		pa[l--] = p;
		p = p->ary[m];
	}
	/*
	 * We have reached the leaf node, plant the
	 * users pointer and return the raw id.
	 */
	p->ary[m] = (struct idr_layer *)ptr;
	__set_bit(m, &p->bitmap);
	p->count++;
	/*
	 * If this layer is full mark the bit in the layer above
	 * to show that this part of the radix tree is full.
	 * This may complete the layer above and require walking
	 * up the radix tree.
	 */
	n = id;
	while (p->bitmap == IDR_FULL) {
		if (!(p = pa[++l]))
			break;
		n = n >> IDR_BITS;
		__set_bit((n & IDR_MASK), &p->bitmap);
	}
	return(id);
}

static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
{
	struct idr_layer *p, *new;
	int layers, v, id;

	id = starting_id;
build_up:
	p = idp->top;
	layers = idp->layers;
	if (unlikely(!p)) {
		if (!(p = alloc_layer(idp)))
			return -1;
		layers = 1;
	}
	/*
	 * Add a new layer to the top of the tree if the requested
	 * id is larger than the currently allocated space.
	 */
	while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
		layers++;
		if (!p->count)
			continue;
		if (!(new = alloc_layer(idp))) {
			/*
			 * The allocation failed.  If we built part of
			 * the structure tear it down.
			 */
			spin_lock(&idp->lock);
			for (new = p; p && p != idp->top; new = p) {
				p = p->ary[0];
				new->ary[0] = NULL;
				new->bitmap = new->count = 0;
				__free_layer(idp, new);
			}
			spin_unlock(&idp->lock);
			return -1;
		}
		new->ary[0] = p;
		new->count = 1;
		if (p->bitmap == IDR_FULL)
			__set_bit(0, &new->bitmap);
		p = new;
	}
	idp->top = p;
	idp->layers = layers;
	v = sub_alloc(idp, ptr, &id);
	if (v == -2)
		goto build_up;
	return(v);
}

/**
 * idr_get_new_above - allocate new idr entry above or equal to a start id
 * @idp: idr handle
 * @ptr: pointer you want associated with the ide
 * @start_id: id to start search at
 * @id: pointer to the allocated handle
 *
 * This is the allocate id function.  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 idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
{
	int rv;

	rv = idr_get_new_above_int(idp, ptr, starting_id);
	/*
	 * This is a cheap hack until the IDR code can be fixed to
	 * return proper error values.
	 */
	if (rv < 0) {
		if (rv == -1)
			return -EAGAIN;
		else /* Will be -3 */
			return -ENOSPC;
	}
	*id = rv;
	return 0;
}
EXPORT_SYMBOL(idr_get_new_above);

/**
 * idr_get_new - allocate new idr entry
 * @idp: idr handle
 * @ptr: pointer you want associated with the ide
 * @id: pointer to the allocated handle
 *
 * This is the allocate id function.  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 idr_get_new(struct idr *idp, void *ptr, int *id)
{
	int rv;

	rv = idr_get_new_above_int(idp, ptr, 0);
	/*
	 * This is a cheap hack until the IDR code can be fixed to
	 * return proper error values.
	 */
	if (rv < 0) {
		if (rv == -1)
			return -EAGAIN;
		else /* Will be -3 */
			return -ENOSPC;
	}
	*id = rv;
	return 0;
}
EXPORT_SYMBOL(idr_get_new);

static void idr_remove_warning(int id)
{
	printk("idr_remove called for id=%d which is not allocated.\n", id);
	dump_stack();
}

static void sub_remove(struct idr *idp, int shift, int id)
{
	struct idr_layer *p = idp->top;
	struct idr_layer **pa[MAX_LEVEL];
	struct idr_layer ***paa = &pa[0];
	int n;

	*paa = NULL;
	*++paa = &idp->top;

	while ((shift > 0) && p) {
		n = (id >> shift) & IDR_MASK;
		__clear_bit(n, &p->bitmap);
		*++paa = &p->ary[n];
		p = p->ary[n];
		shift -= IDR_BITS;
	}
	n = id & IDR_MASK;
	if (likely(p != NULL && test_bit(n, &p->bitmap))){
		__clear_bit(n, &p->bitmap);
		p->ary[n] = NULL;
		while(*paa && ! --((**paa)->count)){
			free_layer(idp, **paa);
			**paa-- = NULL;
		}
		if (!*paa)
			idp->layers = 0;
	} else
		idr_remove_warning(id);
}

/**
 * idr_remove - remove the given id and free it's slot
 * idp: idr handle
 * id: uniqueue key
 */
void idr_remove(struct idr *idp, int id)
{
	struct idr_layer *p;

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

	sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
	if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
	    idp->top->ary[0]) {  // We can drop a layer

		p = idp->top->ary[0];
		idp->top->bitmap = idp->top->count = 0;
		free_layer(idp, idp->top);
		idp->top = p;
		--idp->layers;
	}
	while (idp->id_free_cnt >= IDR_FREE_MAX) {
		p = alloc_layer(idp);
		kmem_cache_free(idr_layer_cache, p);
		return;
	}
}
EXPORT_SYMBOL(idr_remove);

/**
 * 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 = alloc_layer(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().
 *
 * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
 */
void *idr_find(struct idr *idp, int id)
{
	int n;
	struct idr_layer *p;

	n = idp->layers * IDR_BITS;
	p = 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 = p->ary[(id >> n) & IDR_MASK];
	}
	return((void *)p);
}
EXPORT_SYMBOL(idr_find);

static void idr_cache_ctor(void * idr_layer, kmem_cache_t *idr_layer_cache,
		unsigned long flags)
{
	memset(idr_layer, 0, sizeof(struct idr_layer));
}

static  int init_id_cache(void)
{
	if (!idr_layer_cache)
		idr_layer_cache = kmem_cache_create("idr_layer_cache",
			sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
	return 0;
}

/**
 * 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)
{
	init_id_cache();
	memset(idp, 0, sizeof(struct idr));
	spin_lock_init(&idp->lock);
}
EXPORT_SYMBOL(idr_init);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* 2002-10-18 written by Jim Houston jim.houston@ccur.com
	3	* Copyright (C) 2002 by Concurrent Computer Corporation
	4	* Distributed under the GNU GPL license version 2.
	5	*
	6	* Modified by George Anzinger to reuse immediately and to use
	7	* find bit instructions. Also removed _irq on spinlocks.
	8	*
e15ae2dd	9	* Small id to pointer translation service.
1da177e4	10	*
e15ae2dd	11	* It uses a radix tree like structure as a sparse array indexed
1da177e4	12	* by the id to obtain the pointer. The bitmap makes allocating
e15ae2dd	13	* a new id quick.
1da177e4 LT	14	*
	15	* You call it to allocate an id (an int) an associate with that id a
	16	* pointer or what ever, we treat it as a (void *). You can pass this
	17	* id to a user for him to pass back at a later time. You then pass
	18	* that id to this code and it returns your pointer.
	19
e15ae2dd	20	* You can release ids at any time. When all ids are released, most of
1da177e4	21	* the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
e15ae2dd	22	* don't need to go to the memory "store" during an id allocate, just
1da177e4 LT	23	* so you don't need to be too concerned about locking and conflicts
	24	* with the slab allocator.
	25	*/
	26
	27	#ifndef TEST // to test in user space...
	28	#include <linux/slab.h>
	29	#include <linux/init.h>
	30	#include <linux/module.h>
	31	#endif
	32	#include <linux/string.h>
	33	#include <linux/idr.h>
	34
	35	static kmem_cache_t *idr_layer_cache;
	36
	37	static struct idr_layer alloc_layer(struct idr idp)
	38	{
	39	struct idr_layer *p;
	40
	41	spin_lock(&idp->lock);
	42	if ((p = idp->id_free)) {
	43	idp->id_free = p->ary[0];
	44	idp->id_free_cnt--;
	45	p->ary[0] = NULL;
	46	}
	47	spin_unlock(&idp->lock);
	48	return(p);
	49	}
	50
1eec0056 SR	51	/* only called when idp->lock is held */
	52	static void __free_layer(struct idr idp, struct idr_layer p)
	53	{
	54	p->ary[0] = idp->id_free;
	55	idp->id_free = p;
	56	idp->id_free_cnt++;
	57	}
	58
1da177e4 LT	59	static void free_layer(struct idr idp, struct idr_layer p)
	60	{
	61	/*
	62	* Depends on the return element being zeroed.
	63	*/
	64	spin_lock(&idp->lock);
1eec0056	65	__free_layer(idp, p);
1da177e4 LT	66	spin_unlock(&idp->lock);
	67	}
	68
	69	/**
	70	* idr_pre_get - reserver resources for idr allocation
	71	* @idp: idr handle
	72	* @gfp_mask: memory allocation flags
	73	*
	74	* This function should be called prior to locking and calling the
	75	* following function. It preallocates enough memory to satisfy
	76	* the worst possible allocation.
	77	*
	78	* If the system is REALLY out of memory this function returns 0,
	79	* otherwise 1.
	80	*/
fd4f2df2	81	int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
1da177e4 LT	82	{
	83	while (idp->id_free_cnt < IDR_FREE_MAX) {
	84	struct idr_layer *new;
	85	new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
e15ae2dd	86	if (new == NULL)
1da177e4 LT	87	return (0);
	88	free_layer(idp, new);
	89	}
	90	return 1;
	91	}
	92	EXPORT_SYMBOL(idr_pre_get);
	93
	94	static int sub_alloc(struct idr idp, void ptr, int *starting_id)
	95	{
	96	int n, m, sh;
	97	struct idr_layer p, new;
	98	struct idr_layer *pa[MAX_LEVEL];
	99	int l, id;
	100	long bm;
	101
	102	id = *starting_id;
	103	p = idp->top;
	104	l = idp->layers;
	105	pa[l--] = NULL;
	106	while (1) {
	107	/*
	108	* We run around this while until we reach the leaf node...
	109	*/
	110	n = (id >> (IDR_BITS*l)) & IDR_MASK;
	111	bm = ~p->bitmap;
	112	m = find_next_bit(&bm, IDR_SIZE, n);
	113	if (m == IDR_SIZE) {
	114	/* no space available go back to previous layer. */
	115	l++;
e15ae2dd	116	id = (id \| ((1 << (IDR_BITS * l)) - 1)) + 1;
1da177e4 LT	117	if (!(p = pa[l])) {
	118	*starting_id = id;
	119	return -2;
	120	}
	121	continue;
	122	}
	123	if (m != n) {
	124	sh = IDR_BITS*l;
	125	id = ((id >> sh) ^ n ^ m) << sh;
	126	}
	127	if ((id >= MAX_ID_BIT) \|\| (id < 0))
	128	return -3;
	129	if (l == 0)
	130	break;
	131	/*
	132	* Create the layer below if it is missing.
	133	*/
	134	if (!p->ary[m]) {
	135	if (!(new = alloc_layer(idp)))
	136	return -1;
	137	p->ary[m] = new;
	138	p->count++;
	139	}
	140	pa[l--] = p;
	141	p = p->ary[m];
	142	}
	143	/*
	144	* We have reached the leaf node, plant the
	145	* users pointer and return the raw id.
	146	*/
	147	p->ary[m] = (struct idr_layer *)ptr;
	148	__set_bit(m, &p->bitmap);
	149	p->count++;
	150	/*
	151	* If this layer is full mark the bit in the layer above
	152	* to show that this part of the radix tree is full.
	153	* This may complete the layer above and require walking
	154	* up the radix tree.
	155	*/
	156	n = id;
	157	while (p->bitmap == IDR_FULL) {
	158	if (!(p = pa[++l]))
	159	break;
	160	n = n >> IDR_BITS;
	161	__set_bit((n & IDR_MASK), &p->bitmap);
	162	}
	163	return(id);
	164	}
	165
	166	static int idr_get_new_above_int(struct idr idp, void ptr, int starting_id)
	167	{
	168	struct idr_layer p, new;
	169	int layers, v, id;
e15ae2dd	170
1da177e4 LT	171	id = starting_id;
	172	build_up:
	173	p = idp->top;
	174	layers = idp->layers;
	175	if (unlikely(!p)) {
	176	if (!(p = alloc_layer(idp)))
	177	return -1;
	178	layers = 1;
	179	}
	180	/*
	181	* Add a new layer to the top of the tree if the requested
	182	* id is larger than the currently allocated space.
	183	*/
589777ea	184	while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
1da177e4 LT	185	layers++;
	186	if (!p->count)
	187	continue;
	188	if (!(new = alloc_layer(idp))) {
	189	/*
	190	* The allocation failed. If we built part of
	191	* the structure tear it down.
	192	*/
1eec0056	193	spin_lock(&idp->lock);
1da177e4 LT	194	for (new = p; p && p != idp->top; new = p) {
	195	p = p->ary[0];
	196	new->ary[0] = NULL;
	197	new->bitmap = new->count = 0;
1eec0056	198	__free_layer(idp, new);
1da177e4	199	}
1eec0056	200	spin_unlock(&idp->lock);
1da177e4 LT	201	return -1;
	202	}
	203	new->ary[0] = p;
	204	new->count = 1;
	205	if (p->bitmap == IDR_FULL)
	206	__set_bit(0, &new->bitmap);
	207	p = new;
	208	}
	209	idp->top = p;
	210	idp->layers = layers;
	211	v = sub_alloc(idp, ptr, &id);
	212	if (v == -2)
	213	goto build_up;
	214	return(v);
	215	}
	216
	217	/**
7c657f2f	218	* idr_get_new_above - allocate new idr entry above or equal to a start id
1da177e4 LT	219	* @idp: idr handle
	220	* @ptr: pointer you want associated with the ide
	221	* @start_id: id to start search at
	222	* @id: pointer to the allocated handle
	223	*
	224	* This is the allocate id function. It should be called with any
	225	* required locks.
	226	*
	227	* If memory is required, it will return -EAGAIN, you should unlock
	228	* and go back to the idr_pre_get() call. If the idr is full, it will
	229	* return -ENOSPC.
	230	*
	231	* @id returns a value in the range 0 ... 0x7fffffff
	232	*/
	233	int idr_get_new_above(struct idr idp, void ptr, int starting_id, int *id)
	234	{
	235	int rv;
e15ae2dd	236
1da177e4 LT	237	rv = idr_get_new_above_int(idp, ptr, starting_id);
	238	/*
	239	* This is a cheap hack until the IDR code can be fixed to
	240	* return proper error values.
	241	*/
	242	if (rv < 0) {
	243	if (rv == -1)
	244	return -EAGAIN;
	245	else /* Will be -3 */
	246	return -ENOSPC;
	247	}
	248	*id = rv;
	249	return 0;
	250	}
	251	EXPORT_SYMBOL(idr_get_new_above);
	252
	253	/**
	254	* idr_get_new - allocate new idr entry
	255	* @idp: idr handle
	256	* @ptr: pointer you want associated with the ide
	257	* @id: pointer to the allocated handle
	258	*
	259	* This is the allocate id function. It should be called with any
	260	* required locks.
	261	*
	262	* If memory is required, it will return -EAGAIN, you should unlock
	263	* and go back to the idr_pre_get() call. If the idr is full, it will
	264	* return -ENOSPC.
	265	*
	266	* @id returns a value in the range 0 ... 0x7fffffff
	267	*/
	268	int idr_get_new(struct idr idp, void ptr, int *id)
	269	{
	270	int rv;
e15ae2dd	271
1da177e4 LT	272	rv = idr_get_new_above_int(idp, ptr, 0);
	273	/*
	274	* This is a cheap hack until the IDR code can be fixed to
	275	* return proper error values.
	276	*/
	277	if (rv < 0) {
	278	if (rv == -1)
	279	return -EAGAIN;
	280	else /* Will be -3 */
	281	return -ENOSPC;
	282	}
	283	*id = rv;
	284	return 0;
	285	}
	286	EXPORT_SYMBOL(idr_get_new);
	287
	288	static void idr_remove_warning(int id)
	289	{
	290	printk("idr_remove called for id=%d which is not allocated.\n", id);
	291	dump_stack();
	292	}
	293
	294	static void sub_remove(struct idr *idp, int shift, int id)
	295	{
	296	struct idr_layer *p = idp->top;
	297	struct idr_layer **pa[MAX_LEVEL];
	298	struct idr_layer ***paa = &pa[0];
	299	int n;
	300
	301	*paa = NULL;
	302	*++paa = &idp->top;
	303
	304	while ((shift > 0) && p) {
	305	n = (id >> shift) & IDR_MASK;
	306	__clear_bit(n, &p->bitmap);
	307	*++paa = &p->ary[n];
	308	p = p->ary[n];
	309	shift -= IDR_BITS;
	310	}
	311	n = id & IDR_MASK;
	312	if (likely(p != NULL && test_bit(n, &p->bitmap))){
	313	__clear_bit(n, &p->bitmap);
	314	p->ary[n] = NULL;
	315	while(paa && ! --((*paa)->count)){
	316	free_layer(idp, **paa);
	317	**paa-- = NULL;
	318	}
e15ae2dd	319	if (!*paa)
1da177e4	320	idp->layers = 0;
e15ae2dd	321	} else
1da177e4	322	idr_remove_warning(id);
1da177e4 LT	323	}
	324
	325	/**
	326	* idr_remove - remove the given id and free it's slot
	327	* idp: idr handle
	328	* id: uniqueue key
	329	*/
	330	void idr_remove(struct idr *idp, int id)
	331	{
	332	struct idr_layer *p;
	333
	334	/* Mask off upper bits we don't use for the search. */
	335	id &= MAX_ID_MASK;
	336
	337	sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
e15ae2dd JJ	338	if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
e15ae2dd JJ	339	idp->top->ary[0]) { // We can drop a layer
1da177e4 LT	340
	341	p = idp->top->ary[0];
	342	idp->top->bitmap = idp->top->count = 0;
	343	free_layer(idp, idp->top);
	344	idp->top = p;
	345	--idp->layers;
	346	}
	347	while (idp->id_free_cnt >= IDR_FREE_MAX) {
1da177e4 LT	348	p = alloc_layer(idp);
	349	kmem_cache_free(idr_layer_cache, p);
	350	return;
	351	}
	352	}
	353	EXPORT_SYMBOL(idr_remove);
	354
8d3b3591 AM	355	/**
	356	* idr_destroy - release all cached layers within an idr tree
	357	* idp: idr handle
	358	*/
	359	void idr_destroy(struct idr *idp)
	360	{
	361	while (idp->id_free_cnt) {
	362	struct idr_layer *p = alloc_layer(idp);
	363	kmem_cache_free(idr_layer_cache, p);
	364	}
	365	}
	366	EXPORT_SYMBOL(idr_destroy);
	367
1da177e4 LT	368	/**
	369	* idr_find - return pointer for given id
	370	* @idp: idr handle
	371	* @id: lookup key
	372	*
	373	* Return the pointer given the id it has been registered with. A %NULL
	374	* return indicates that @id is not valid or you passed %NULL in
	375	* idr_get_new().
	376	*
	377	* The caller must serialize idr_find() vs idr_get_new() and idr_remove().
	378	*/
	379	void idr_find(struct idr idp, int id)
	380	{
	381	int n;
	382	struct idr_layer *p;
	383
	384	n = idp->layers * IDR_BITS;
	385	p = idp->top;
	386
	387	/* Mask off upper bits we don't use for the search. */
	388	id &= MAX_ID_MASK;
	389
	390	if (id >= (1 << n))
	391	return NULL;
	392
	393	while (n > 0 && p) {
	394	n -= IDR_BITS;
	395	p = p->ary[(id >> n) & IDR_MASK];
	396	}
	397	return((void *)p);
	398	}
	399	EXPORT_SYMBOL(idr_find);
	400
e15ae2dd JJ	401	static void idr_cache_ctor(void * idr_layer, kmem_cache_t *idr_layer_cache,
e15ae2dd JJ	402	unsigned long flags)
1da177e4 LT	403	{
	404	memset(idr_layer, 0, sizeof(struct idr_layer));
	405	}
	406
	407	static int init_id_cache(void)
	408	{
	409	if (!idr_layer_cache)
e15ae2dd	410	idr_layer_cache = kmem_cache_create("idr_layer_cache",
1da177e4 LT	411	sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
	412	return 0;
	413	}
	414
	415	/**
	416	* idr_init - initialize idr handle
	417	* @idp: idr handle
	418	*
	419	* This function is use to set up the handle (@idp) that you will pass
	420	* to the rest of the functions.
	421	*/
	422	void idr_init(struct idr *idp)
	423	{
	424	init_id_cache();
	425	memset(idp, 0, sizeof(struct idr));
	426	spin_lock_init(&idp->lock);
	427	}
	428	EXPORT_SYMBOL(idr_init);