[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/err.h>
#include <linux/string.h>
#include <linux/idr.h>

static struct kmem_cache *idr_layer_cache;

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

	spin_lock_irqsave(&idp->lock, flags);
	if ((p = idp->id_free)) {
		idp->id_free = p->ary[0];
		idp->id_free_cnt--;
		p->ary[0] = NULL;
	}
	spin_unlock_irqrestore(&idp->lock, flags);
	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)
{
	unsigned long flags;

	/*
	 * Depends on the return element being zeroed.
	 */
	spin_lock_irqsave(&idp->lock, flags);
	__free_layer(idp, p);
	spin_unlock_irqrestore(&idp->lock, flags);
}

/**
 * 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;
	unsigned long flags;

	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_irqsave(&idp->lock, flags);
			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_irqrestore(&idp->lock, flags);
			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);

/**
 * 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 vs idr_find(), idr_get_new(), and idr_remove().
 */
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];
	p->ary[n] = ptr;

	return old_p;
}
EXPORT_SYMBOL(idr_replace);

static void idr_cache_ctor(void * idr_layer, struct kmem_cache *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
5806f07c	32	#include <linux/err.h>
1da177e4 LT	33	#include <linux/string.h>
	34	#include <linux/idr.h>
	35
e18b890b	36	static struct kmem_cache *idr_layer_cache;
1da177e4 LT	37
	38	static struct idr_layer alloc_layer(struct idr idp)
	39	{
	40	struct idr_layer *p;
c259cc28	41	unsigned long flags;
1da177e4	42
c259cc28	43	spin_lock_irqsave(&idp->lock, flags);
1da177e4 LT	44	if ((p = idp->id_free)) {
	45	idp->id_free = p->ary[0];
	46	idp->id_free_cnt--;
	47	p->ary[0] = NULL;
	48	}
c259cc28	49	spin_unlock_irqrestore(&idp->lock, flags);
1da177e4 LT	50	return(p);
	51	}
	52
1eec0056 SR	53	/* only called when idp->lock is held */
	54	static void __free_layer(struct idr idp, struct idr_layer p)
	55	{
	56	p->ary[0] = idp->id_free;
	57	idp->id_free = p;
	58	idp->id_free_cnt++;
	59	}
	60
1da177e4 LT	61	static void free_layer(struct idr idp, struct idr_layer p)
1da177e4 LT	62	{
c259cc28 RD	63	unsigned long flags;
c259cc28 RD	64
1da177e4 LT	65	/*
	66	* Depends on the return element being zeroed.
	67	*/
c259cc28	68	spin_lock_irqsave(&idp->lock, flags);
1eec0056	69	__free_layer(idp, p);
c259cc28	70	spin_unlock_irqrestore(&idp->lock, flags);
1da177e4 LT	71	}
	72
	73	/**
	74	* idr_pre_get - reserver resources for idr allocation
	75	* @idp: idr handle
	76	* @gfp_mask: memory allocation flags
	77	*
	78	* This function should be called prior to locking and calling the
	79	* following function. It preallocates enough memory to satisfy
	80	* the worst possible allocation.
	81	*
	82	* If the system is REALLY out of memory this function returns 0,
	83	* otherwise 1.
	84	*/
fd4f2df2	85	int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
1da177e4 LT	86	{
	87	while (idp->id_free_cnt < IDR_FREE_MAX) {
	88	struct idr_layer *new;
	89	new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
e15ae2dd	90	if (new == NULL)
1da177e4 LT	91	return (0);
	92	free_layer(idp, new);
	93	}
	94	return 1;
	95	}
	96	EXPORT_SYMBOL(idr_pre_get);
	97
	98	static int sub_alloc(struct idr idp, void ptr, int *starting_id)
	99	{
	100	int n, m, sh;
	101	struct idr_layer p, new;
	102	struct idr_layer *pa[MAX_LEVEL];
	103	int l, id;
	104	long bm;
	105
	106	id = *starting_id;
	107	p = idp->top;
	108	l = idp->layers;
	109	pa[l--] = NULL;
	110	while (1) {
	111	/*
	112	* We run around this while until we reach the leaf node...
	113	*/
	114	n = (id >> (IDR_BITS*l)) & IDR_MASK;
	115	bm = ~p->bitmap;
	116	m = find_next_bit(&bm, IDR_SIZE, n);
	117	if (m == IDR_SIZE) {
	118	/* no space available go back to previous layer. */
	119	l++;
e15ae2dd	120	id = (id \| ((1 << (IDR_BITS * l)) - 1)) + 1;
1da177e4 LT	121	if (!(p = pa[l])) {
	122	*starting_id = id;
	123	return -2;
	124	}
	125	continue;
	126	}
	127	if (m != n) {
	128	sh = IDR_BITS*l;
	129	id = ((id >> sh) ^ n ^ m) << sh;
	130	}
	131	if ((id >= MAX_ID_BIT) \|\| (id < 0))
	132	return -3;
	133	if (l == 0)
	134	break;
	135	/*
	136	* Create the layer below if it is missing.
	137	*/
	138	if (!p->ary[m]) {
	139	if (!(new = alloc_layer(idp)))
	140	return -1;
	141	p->ary[m] = new;
	142	p->count++;
	143	}
	144	pa[l--] = p;
	145	p = p->ary[m];
	146	}
	147	/*
	148	* We have reached the leaf node, plant the
	149	* users pointer and return the raw id.
	150	*/
	151	p->ary[m] = (struct idr_layer *)ptr;
	152	__set_bit(m, &p->bitmap);
	153	p->count++;
	154	/*
	155	* If this layer is full mark the bit in the layer above
	156	* to show that this part of the radix tree is full.
	157	* This may complete the layer above and require walking
	158	* up the radix tree.
	159	*/
	160	n = id;
	161	while (p->bitmap == IDR_FULL) {
	162	if (!(p = pa[++l]))
	163	break;
	164	n = n >> IDR_BITS;
	165	__set_bit((n & IDR_MASK), &p->bitmap);
	166	}
	167	return(id);
	168	}
	169
	170	static int idr_get_new_above_int(struct idr idp, void ptr, int starting_id)
	171	{
	172	struct idr_layer p, new;
	173	int layers, v, id;
c259cc28	174	unsigned long flags;
e15ae2dd	175
1da177e4 LT	176	id = starting_id;
	177	build_up:
	178	p = idp->top;
	179	layers = idp->layers;
	180	if (unlikely(!p)) {
	181	if (!(p = alloc_layer(idp)))
	182	return -1;
	183	layers = 1;
	184	}
	185	/*
	186	* Add a new layer to the top of the tree if the requested
	187	* id is larger than the currently allocated space.
	188	*/
589777ea	189	while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
1da177e4 LT	190	layers++;
	191	if (!p->count)
	192	continue;
	193	if (!(new = alloc_layer(idp))) {
	194	/*
	195	* The allocation failed. If we built part of
	196	* the structure tear it down.
	197	*/
c259cc28	198	spin_lock_irqsave(&idp->lock, flags);
1da177e4 LT	199	for (new = p; p && p != idp->top; new = p) {
	200	p = p->ary[0];
	201	new->ary[0] = NULL;
	202	new->bitmap = new->count = 0;
1eec0056	203	__free_layer(idp, new);
1da177e4	204	}
c259cc28	205	spin_unlock_irqrestore(&idp->lock, flags);
1da177e4 LT	206	return -1;
	207	}
	208	new->ary[0] = p;
	209	new->count = 1;
	210	if (p->bitmap == IDR_FULL)
	211	__set_bit(0, &new->bitmap);
	212	p = new;
	213	}
	214	idp->top = p;
	215	idp->layers = layers;
	216	v = sub_alloc(idp, ptr, &id);
	217	if (v == -2)
	218	goto build_up;
	219	return(v);
	220	}
	221
	222	/**
7c657f2f	223	* idr_get_new_above - allocate new idr entry above or equal to a start id
1da177e4 LT	224	* @idp: idr handle
	225	* @ptr: pointer you want associated with the ide
	226	* @start_id: id to start search at
	227	* @id: pointer to the allocated handle
	228	*
	229	* This is the allocate id function. It should be called with any
	230	* required locks.
	231	*
	232	* If memory is required, it will return -EAGAIN, you should unlock
	233	* and go back to the idr_pre_get() call. If the idr is full, it will
	234	* return -ENOSPC.
	235	*
	236	* @id returns a value in the range 0 ... 0x7fffffff
	237	*/
	238	int idr_get_new_above(struct idr idp, void ptr, int starting_id, int *id)
	239	{
	240	int rv;
e15ae2dd	241
1da177e4 LT	242	rv = idr_get_new_above_int(idp, ptr, starting_id);
	243	/*
	244	* This is a cheap hack until the IDR code can be fixed to
	245	* return proper error values.
	246	*/
	247	if (rv < 0) {
	248	if (rv == -1)
	249	return -EAGAIN;
	250	else /* Will be -3 */
	251	return -ENOSPC;
	252	}
	253	*id = rv;
	254	return 0;
	255	}
	256	EXPORT_SYMBOL(idr_get_new_above);
	257
	258	/**
	259	* idr_get_new - allocate new idr entry
	260	* @idp: idr handle
	261	* @ptr: pointer you want associated with the ide
	262	* @id: pointer to the allocated handle
	263	*
	264	* This is the allocate id function. It should be called with any
	265	* required locks.
	266	*
	267	* If memory is required, it will return -EAGAIN, you should unlock
	268	* and go back to the idr_pre_get() call. If the idr is full, it will
	269	* return -ENOSPC.
	270	*
	271	* @id returns a value in the range 0 ... 0x7fffffff
	272	*/
	273	int idr_get_new(struct idr idp, void ptr, int *id)
	274	{
	275	int rv;
e15ae2dd	276
1da177e4 LT	277	rv = idr_get_new_above_int(idp, ptr, 0);
	278	/*
	279	* This is a cheap hack until the IDR code can be fixed to
	280	* return proper error values.
	281	*/
	282	if (rv < 0) {
	283	if (rv == -1)
	284	return -EAGAIN;
	285	else /* Will be -3 */
	286	return -ENOSPC;
	287	}
	288	*id = rv;
	289	return 0;
	290	}
	291	EXPORT_SYMBOL(idr_get_new);
	292
	293	static void idr_remove_warning(int id)
	294	{
	295	printk("idr_remove called for id=%d which is not allocated.\n", id);
	296	dump_stack();
	297	}
	298
	299	static void sub_remove(struct idr *idp, int shift, int id)
	300	{
	301	struct idr_layer *p = idp->top;
	302	struct idr_layer **pa[MAX_LEVEL];
	303	struct idr_layer ***paa = &pa[0];
	304	int n;
	305
	306	*paa = NULL;
	307	*++paa = &idp->top;
	308
	309	while ((shift > 0) && p) {
	310	n = (id >> shift) & IDR_MASK;
	311	__clear_bit(n, &p->bitmap);
	312	*++paa = &p->ary[n];
	313	p = p->ary[n];
	314	shift -= IDR_BITS;
	315	}
	316	n = id & IDR_MASK;
	317	if (likely(p != NULL && test_bit(n, &p->bitmap))){
	318	__clear_bit(n, &p->bitmap);
	319	p->ary[n] = NULL;
	320	while(paa && ! --((*paa)->count)){
	321	free_layer(idp, **paa);
	322	**paa-- = NULL;
	323	}
e15ae2dd	324	if (!*paa)
1da177e4	325	idp->layers = 0;
e15ae2dd	326	} else
1da177e4	327	idr_remove_warning(id);
1da177e4 LT	328	}
	329
	330	/**
	331	* idr_remove - remove the given id and free it's slot
	332	* idp: idr handle
	333	* id: uniqueue key
	334	*/
	335	void idr_remove(struct idr *idp, int id)
	336	{
	337	struct idr_layer *p;
	338
	339	/* Mask off upper bits we don't use for the search. */
	340	id &= MAX_ID_MASK;
	341
	342	sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
e15ae2dd JJ	343	if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
e15ae2dd JJ	344	idp->top->ary[0]) { // We can drop a layer
1da177e4 LT	345
	346	p = idp->top->ary[0];
	347	idp->top->bitmap = idp->top->count = 0;
	348	free_layer(idp, idp->top);
	349	idp->top = p;
	350	--idp->layers;
	351	}
	352	while (idp->id_free_cnt >= IDR_FREE_MAX) {
1da177e4 LT	353	p = alloc_layer(idp);
	354	kmem_cache_free(idr_layer_cache, p);
	355	return;
	356	}
	357	}
	358	EXPORT_SYMBOL(idr_remove);
	359
8d3b3591 AM	360	/**
	361	* idr_destroy - release all cached layers within an idr tree
	362	* idp: idr handle
	363	*/
	364	void idr_destroy(struct idr *idp)
	365	{
	366	while (idp->id_free_cnt) {
	367	struct idr_layer *p = alloc_layer(idp);
	368	kmem_cache_free(idr_layer_cache, p);
	369	}
	370	}
	371	EXPORT_SYMBOL(idr_destroy);
	372
1da177e4 LT	373	/**
	374	* idr_find - return pointer for given id
	375	* @idp: idr handle
	376	* @id: lookup key
	377	*
	378	* Return the pointer given the id it has been registered with. A %NULL
	379	* return indicates that @id is not valid or you passed %NULL in
	380	* idr_get_new().
	381	*
	382	* The caller must serialize idr_find() vs idr_get_new() and idr_remove().
	383	*/
	384	void idr_find(struct idr idp, int id)
	385	{
	386	int n;
	387	struct idr_layer *p;
	388
	389	n = idp->layers * IDR_BITS;
	390	p = idp->top;
	391
	392	/* Mask off upper bits we don't use for the search. */
	393	id &= MAX_ID_MASK;
	394
	395	if (id >= (1 << n))
	396	return NULL;
	397
	398	while (n > 0 && p) {
	399	n -= IDR_BITS;
	400	p = p->ary[(id >> n) & IDR_MASK];
	401	}
	402	return((void *)p);
	403	}
	404	EXPORT_SYMBOL(idr_find);
	405
5806f07c JM	406	/**
	407	* idr_replace - replace pointer for given id
	408	* @idp: idr handle
	409	* @ptr: pointer you want associated with the id
	410	* @id: lookup key
	411	*
	412	* Replace the pointer registered with an id and return the old value.
	413	* A -ENOENT return indicates that @id was not found.
	414	* A -EINVAL return indicates that @id was not within valid constraints.
	415	*
	416	* The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
	417	*/
	418	void idr_replace(struct idr idp, void *ptr, int id)
	419	{
	420	int n;
	421	struct idr_layer p, old_p;
	422
	423	n = idp->layers * IDR_BITS;
	424	p = idp->top;
	425
	426	id &= MAX_ID_MASK;
	427
	428	if (id >= (1 << n))
	429	return ERR_PTR(-EINVAL);
	430
	431	n -= IDR_BITS;
	432	while ((n > 0) && p) {
	433	p = p->ary[(id >> n) & IDR_MASK];
	434	n -= IDR_BITS;
	435	}
	436
	437	n = id & IDR_MASK;
	438	if (unlikely(p == NULL \|\| !test_bit(n, &p->bitmap)))
	439	return ERR_PTR(-ENOENT);
	440
	441	old_p = p->ary[n];
	442	p->ary[n] = ptr;
	443
	444	return old_p;
	445	}
	446	EXPORT_SYMBOL(idr_replace);
	447
e18b890b	448	static void idr_cache_ctor(void * idr_layer, struct kmem_cache *idr_layer_cache,
e15ae2dd	449	unsigned long flags)
1da177e4 LT	450	{
	451	memset(idr_layer, 0, sizeof(struct idr_layer));
	452	}
	453
	454	static int init_id_cache(void)
	455	{
	456	if (!idr_layer_cache)
e15ae2dd	457	idr_layer_cache = kmem_cache_create("idr_layer_cache",
1da177e4 LT	458	sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
	459	return 0;
	460	}
	461
	462	/**
	463	* idr_init - initialize idr handle
	464	* @idp: idr handle
	465	*
	466	* This function is use to set up the handle (@idp) that you will pass
	467	* to the rest of the functions.
	468	*/
	469	void idr_init(struct idr *idp)
	470	{
	471	init_id_cache();
	472	memset(idp, 0, sizeof(struct idr));
	473	spin_lock_init(&idp->lock);
	474	}
	475	EXPORT_SYMBOL(idr_init);