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/*

 * 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.

 *

 * Modified by Nadia Derbey to make it RCU safe.

 *

 * 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 MAX_IDR_FREE) 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.

 */

#include 

#include 

#include 

#include 

#include 

//#include 

static inline void * __must_check ERR_PTR(long error)

{

	return (void *) error;

}

unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,

                                 unsigned long offset);

#define MAX_IDR_SHIFT		(sizeof(int) * 8 - 1)

#define MAX_IDR_BIT		(1U << MAX_IDR_SHIFT)

/* Leave the possibility of an incomplete final layer */

#define MAX_IDR_LEVEL ((MAX_IDR_SHIFT + IDR_BITS - 1) / IDR_BITS)

/* Number of id_layer structs to leave in free list */

#define MAX_IDR_FREE (MAX_IDR_LEVEL * 2)

static struct idr_layer *idr_preload_head;

static int idr_preload_cnt;

static DEFINE_SPINLOCK(simple_ida_lock);

/* the maximum ID which can be allocated given idr->layers */

static int idr_max(int layers)

{

	int bits = min_t(int, layers * IDR_BITS, MAX_IDR_SHIFT);

	return (1 << bits) - 1;

}

/*

 * Prefix mask for an idr_layer at @layer.  For layer 0, the prefix mask is

 * all bits except for the lower IDR_BITS.  For layer 1, 2 * IDR_BITS, and

 * so on.

 */

static int idr_layer_prefix_mask(int layer)

{

	return ~idr_max(layer + 1);

}

static struct idr_layer *get_from_free_list(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);

}

/**

 * idr_layer_alloc - allocate a new idr_layer

 * @gfp_mask: allocation mask

 * @layer_idr: optional idr to allocate from

 *

 * If @layer_idr is %NULL, directly allocate one using @gfp_mask or fetch

 * one from the per-cpu preload buffer.  If @layer_idr is not %NULL, fetch

 * an idr_layer from @idr->id_free.

 *

 * @layer_idr is to maintain backward compatibility with the old alloc

 * interface - idr_pre_get() and idr_get_new*() - and will be removed

 * together with per-pool preload buffer.

 */

static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)

{

	struct idr_layer *new;

	/* this is the old path, bypass to get_from_free_list() */

	if (layer_idr)

		return get_from_free_list(layer_idr);

	/* try to allocate directly from kmem_cache */

	new = kzalloc(sizeof(struct idr_layer), gfp_mask);

	if (new)

		return new;

	new = idr_preload_head;

	if (new) {

		idr_preload_head = new->ary[0];

		idr_preload_cnt--;

		new->ary[0] = NULL;

	}

	preempt_enable();

	return new;

}

static void idr_layer_rcu_free(struct rcu_head *head)

{

	struct idr_layer *layer;

    layer = container_of(head, struct idr_layer, rcu_head);

    kfree(layer);

}

static inline void free_layer(struct idr *idr, struct idr_layer *p)

{

	if (idr->hint && idr->hint == p)

		RCU_INIT_POINTER(idr->hint, NULL);

    idr_layer_rcu_free(&p->rcu_head);

}

/* only called when idp->lock is held */

static void __move_to_free_list(struct idr *idp, struct idr_layer *p)

{

	p->ary[0] = idp->id_free;

	idp->id_free = p;

	idp->id_free_cnt++;

}

static void move_to_free_list(struct idr *idp, struct idr_layer *p)

{

	unsigned long flags;

	/*

	 * Depends on the return element being zeroed.

	 */

	spin_lock_irqsave(&idp->lock, flags);

	__move_to_free_list(idp, p);

	spin_unlock_irqrestore(&idp->lock, flags);

}

static void idr_mark_full(struct idr_layer **pa, int id)

{

	struct idr_layer *p = pa[0];

	int l = 0;

	__set_bit(id & IDR_MASK, p->bitmap);

	/*

	 * 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.

	 */

	while (bitmap_full(p->bitmap, IDR_SIZE)) {

		if (!(p = pa[++l]))

			break;

		id = id >> IDR_BITS;

		__set_bit((id & IDR_MASK), p->bitmap);

	}

}

int __idr_pre_get(struct idr *idp, gfp_t gfp_mask)

{

	while (idp->id_free_cnt < MAX_IDR_FREE) {

       struct idr_layer *new;

       new = kzalloc(sizeof(struct idr_layer), gfp_mask);

       if (new == NULL)

           return (0);

       move_to_free_list(idp, new);

   }

   return 1;

}

EXPORT_SYMBOL(__idr_pre_get);

/**

 * sub_alloc - try to allocate an id without growing the tree depth

 * @idp: idr handle

 * @starting_id: id to start search at

 * @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer

 * @gfp_mask: allocation mask for idr_layer_alloc()

 * @layer_idr: optional idr passed to idr_layer_alloc()

 *

 * Allocate an id in range [@starting_id, INT_MAX] from @idp without

 * growing its depth.  Returns

 *

 *  the allocated id >= 0 if successful,

 *  -EAGAIN if the tree needs to grow for allocation to succeed,

 *  -ENOSPC if the id space is exhausted,

 *  -ENOMEM if more idr_layers need to be allocated.

 */

static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa,

		     gfp_t gfp_mask, struct idr *layer_idr)

{

	int n, m, sh;

	struct idr_layer *p, *new;

	int l, id, oid;

	id = *starting_id;

 restart:

	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;

		m = find_next_zero_bit(p->bitmap, IDR_SIZE, n);

		if (m == IDR_SIZE) {

			/* no space available go back to previous layer. */

			l++;

			oid = id;

			id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;

			/* if already at the top layer, we need to grow */

			if (id >= 1 << (idp->layers * IDR_BITS)) {

				*starting_id = id;

				return -EAGAIN;

			}

			p = pa[l];

			BUG_ON(!p);

			/* If we need to go up one layer, continue the

			 * loop; otherwise, restart from the top.

			 */

			sh = IDR_BITS * (l + 1);

			if (oid >> sh == id >> sh)

				continue;

			else

				goto restart;

		}

		if (m != n) {

			sh = IDR_BITS*l;

			id = ((id >> sh) ^ n ^ m) << sh;

		}

		if ((id >= MAX_IDR_BIT) || (id < 0))

			return -ENOSPC;

		if (l == 0)

			break;

		/*

		 * Create the layer below if it is missing.

		 */

		if (!p->ary[m]) {

			new = idr_layer_alloc(gfp_mask, layer_idr);

			if (!new)

				return -ENOMEM;

			new->layer = l-1;

			new->prefix = id & idr_layer_prefix_mask(new->layer);

			rcu_assign_pointer(p->ary[m], new);

			p->count++;

		}

		pa[l--] = p;

		p = p->ary[m];

	}

	pa[l] = p;

	return id;

}

static int idr_get_empty_slot(struct idr *idp, int starting_id,

			      struct idr_layer **pa, gfp_t gfp_mask,

			      struct idr *layer_idr)

{

	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 = idr_layer_alloc(gfp_mask, layer_idr)))

			return -ENOMEM;

		p->layer = 0;

		layers = 1;

	}

	/*

	 * Add a new layer to the top of the tree if the requested

	 * id is larger than the currently allocated space.

	 */

	while (id > idr_max(layers)) {

		layers++;

		if (!p->count) {

			/* special case: if the tree is currently empty,

			 * then we grow the tree by moving the top node

			 * upwards.

			 */

			p->layer++;

			WARN_ON_ONCE(p->prefix);

			continue;

		}

		if (!(new = idr_layer_alloc(gfp_mask, layer_idr))) {

			/*

			 * 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->count = 0;

				bitmap_clear(new->bitmap, 0, IDR_SIZE);

				__move_to_free_list(idp, new);

			}

			spin_unlock_irqrestore(&idp->lock, flags);

			return -ENOMEM;

		}

		new->ary[0] = p;

		new->count = 1;

		new->layer = layers-1;

		new->prefix = id & idr_layer_prefix_mask(new->layer);

		if (bitmap_full(p->bitmap, IDR_SIZE))

			__set_bit(0, new->bitmap);

		p = new;

	}

	rcu_assign_pointer(idp->top, p);

	idp->layers = layers;

	v = sub_alloc(idp, &id, pa, gfp_mask, layer_idr);

	if (v == -EAGAIN)

		goto build_up;

	return(v);

}

/*

 * @id and @pa are from a successful allocation from idr_get_empty_slot().

 * Install the user pointer @ptr and mark the slot full.

 */

static void idr_fill_slot(struct idr *idr, void *ptr, int id,

			  struct idr_layer **pa)

{

	/* update hint used for lookup, cleared from free_layer() */

	rcu_assign_pointer(idr->hint, pa[0]);

	rcu_assign_pointer(pa[0]->ary[id & IDR_MASK], (struct idr_layer *)ptr);

		pa[0]->count++;

		idr_mark_full(pa, id);

}

int __idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)

{

	struct idr_layer *pa[MAX_IDR_LEVEL + 1];

	int rv;

	rv = idr_get_empty_slot(idp, starting_id, pa, 0, idp);

	if (rv < 0)

		return rv == -ENOMEM ? -EAGAIN : rv;

	idr_fill_slot(idp, ptr, rv, pa);

	*id = rv;

    return 0;

}

EXPORT_SYMBOL(__idr_get_new_above);

/**

 * idr_preload - preload for idr_alloc()

 * @gfp_mask: allocation mask to use for preloading

 *

 * Preload per-cpu layer buffer for idr_alloc().  Can only be used from

 * process context and each idr_preload() invocation should be matched with

 * idr_preload_end().  Note that preemption is disabled while preloaded.

 *

 * The first idr_alloc() in the preloaded section can be treated as if it

 * were invoked with @gfp_mask used for preloading.  This allows using more

 * permissive allocation masks for idrs protected by spinlocks.

 *

 * For example, if idr_alloc() below fails, the failure can be treated as

 * if idr_alloc() were called with GFP_KERNEL rather than GFP_NOWAIT.

 *

 *	idr_preload(GFP_KERNEL);

 *	spin_lock(lock);

 *

 *	id = idr_alloc(idr, ptr, start, end, GFP_NOWAIT);

 *

 *	spin_unlock(lock);

 *	idr_preload_end();

 *	if (id < 0)

 *		error;

 */

void idr_preload(gfp_t gfp_mask)

{

	/*

	 * idr_alloc() is likely to succeed w/o full idr_layer buffer and

	 * return value from idr_alloc() needs to be checked for failure

	 * anyway.  Silently give up if allocation fails.  The caller can

	 * treat failures from idr_alloc() as if idr_alloc() were called

	 * with @gfp_mask which should be enough.

	 */

	while (idr_preload_cnt < MAX_IDR_FREE) {

		struct idr_layer *new;

		new = kzalloc(sizeof(struct idr_layer), gfp_mask);

		if (!new)

			break;

		/* link the new one to per-cpu preload list */

		new->ary[0] = idr_preload_head;

		idr_preload_head = new;

		idr_preload_cnt++;

	}

}

EXPORT_SYMBOL(idr_preload);

/**

 * idr_alloc - allocate new idr entry

 * @idr: the (initialized) idr

 * @ptr: pointer to be associated with the new id

 * @start: the minimum id (inclusive)

 * @end: the maximum id (exclusive, <= 0 for max)

 * @gfp_mask: memory allocation flags

 *

 * Allocate an id in [start, end) and associate it with @ptr.  If no ID is

 * available in the specified range, returns -ENOSPC.  On memory allocation

 * failure, returns -ENOMEM.

 *

 * Note that @end is treated as max when <= 0.  This is to always allow

 * using @start + N as @end as long as N is inside integer range.

 *

 * The user is responsible for exclusively synchronizing all operations

 * which may modify @idr.  However, read-only accesses such as idr_find()

 * or iteration can be performed under RCU read lock provided the user

 * destroys @ptr in RCU-safe way after removal from idr.

 */

int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)

{

	int max = end > 0 ? end - 1 : INT_MAX;	/* inclusive upper limit */

	struct idr_layer *pa[MAX_IDR_LEVEL + 1];

	int id;

	/* sanity checks */

	if (WARN_ON_ONCE(start < 0))

		return -EINVAL;

	if (unlikely(max < start))

		return -ENOSPC;

	/* allocate id */

	id = idr_get_empty_slot(idr, start, pa, gfp_mask, NULL);

	if (unlikely(id < 0))

		return id;

	if (unlikely(id > max))

		return -ENOSPC;

	idr_fill_slot(idr, ptr, id, pa);

	return id;

}

EXPORT_SYMBOL_GPL(idr_alloc);

/**

 * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion

 * @idr: the (initialized) idr

 * @ptr: pointer to be associated with the new id

 * @start: the minimum id (inclusive)

 * @end: the maximum id (exclusive, <= 0 for max)

 * @gfp_mask: memory allocation flags

 *

 * Essentially the same as idr_alloc, but prefers to allocate progressively

 * higher ids if it can. If the "cur" counter wraps, then it will start again

 * at the "start" end of the range and allocate one that has already been used.

 */

int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,

			gfp_t gfp_mask)

{

	int id;

	id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);

	if (id == -ENOSPC)

		id = idr_alloc(idr, ptr, start, end, gfp_mask);

	if (likely(id >= 0))

		idr->cur = id + 1;

	return id;

}

EXPORT_SYMBOL(idr_alloc_cyclic);

static void idr_remove_warning(int id)

{

	WARN(1, "idr_remove called for id=%d which is not allocated.\n", id);

}

static void sub_remove(struct idr *idp, int shift, int id)

{

	struct idr_layer *p = idp->top;

	struct idr_layer **pa[MAX_IDR_LEVEL + 1];

	struct idr_layer ***paa = &pa[0];

	struct idr_layer *to_free;

	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);

		rcu_assign_pointer(p->ary[n], NULL);

		to_free = NULL;

		while(*paa && ! --((**paa)->count)){

			if (to_free)

				free_layer(idp, to_free);

			to_free = **paa;

			**paa-- = NULL;

		}

		if (!*paa)

			idp->layers = 0;

		if (to_free)

			free_layer(idp, to_free);

	} else

		idr_remove_warning(id);

}

/**

 * idr_remove - remove the given id and free its slot

 * @idp: idr handle

 * @id: unique key

 */

void idr_remove(struct idr *idp, int id)

{

	struct idr_layer *p;

	struct idr_layer *to_free;

	if (id < 0)

		return;

	sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);

	if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&

	    idp->top->ary[0]) {

		/*

		 * Single child at leftmost slot: we can shrink the tree.

		 * This level is not needed anymore since when layers are

		 * inserted, they are inserted at the top of the existing

		 * tree.

		 */

		to_free = idp->top;

		p = idp->top->ary[0];

		rcu_assign_pointer(idp->top, p);

		--idp->layers;

		to_free->count = 0;

		bitmap_clear(to_free->bitmap, 0, IDR_SIZE);

		free_layer(idp, to_free);

	}

	while (idp->id_free_cnt >= MAX_IDR_FREE) {

		p = get_from_free_list(idp);

		/*

		 * Note: we don't call the rcu callback here, since the only

		 * layers that fall into the freelist are those that have been

		 * preallocated.

		 */

        kfree(p);

	}

	return;

}

EXPORT_SYMBOL(idr_remove);

void __idr_remove_all(struct idr *idp)

{

	int n, id, max;

	int bt_mask;

	struct idr_layer *p;

	struct idr_layer *pa[MAX_IDR_LEVEL + 1];

	struct idr_layer **paa = &pa[0];

	n = idp->layers * IDR_BITS;

	p = idp->top;

	rcu_assign_pointer(idp->top, NULL);

	max = idr_max(idp->layers);

	id = 0;

	while (id >= 0 && id <= max) {

		while (n > IDR_BITS && p) {

			n -= IDR_BITS;

			*paa++ = p;

			p = p->ary[(id >> n) & IDR_MASK];

		}

		bt_mask = id;

		id += 1 << n;

		/* Get the highest bit that the above add changed from 0->1. */

		while (n < fls(id ^ bt_mask)) {

			if (p)

				free_layer(idp, p);

			n += IDR_BITS;

			p = *--paa;

		}

	}

	idp->layers = 0;

}

EXPORT_SYMBOL(__idr_remove_all);

/**

 * idr_destroy - release all cached layers within an idr tree

 * @idp: idr handle

 *

 * Free all id mappings and all idp_layers.  After this function, @idp is

 * completely unused and can be freed / recycled.  The caller is

 * responsible for ensuring that no one else accesses @idp during or after

 * idr_destroy().

 *

 * A typical clean-up sequence for objects stored in an idr tree will use

 * idr_for_each() to free all objects, if necessay, then idr_destroy() to

 * free up the id mappings and cached idr_layers.

 */

void idr_destroy(struct idr *idp)

{

	__idr_remove_all(idp);

	while (idp->id_free_cnt) {

		struct idr_layer *p = get_from_free_list(idp);

        kfree(p);

	}

}

EXPORT_SYMBOL(idr_destroy);

void *idr_find_slowpath(struct idr *idp, int id)

{

	int n;

	struct idr_layer *p;

	if (id < 0)

		return NULL;

	p = rcu_dereference_raw(idp->top);

	if (!p)

		return NULL;

	n = (p->layer+1) * IDR_BITS;

	if (id > idr_max(p->layer + 1))

		return NULL;

	BUG_ON(n == 0);

	while (n > 0 && p) {

		n -= IDR_BITS;

		BUG_ON(n != p->layer*IDR_BITS);

		p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);

	}

	return((void *)p);

}

EXPORT_SYMBOL(idr_find_slowpath);

/**

 * 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_IDR_LEVEL + 1];

	struct idr_layer **paa = &pa[0];

	n = idp->layers * IDR_BITS;

	p = rcu_dereference_raw(idp->top);

	max = idr_max(idp->layers);

	id = 0;

	while (id >= 0 && id <= max) {

		while (n > 0 && p) {

			n -= IDR_BITS;

			*paa++ = p;

			p = rcu_dereference_raw(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_get_next - lookup next object of id to given id.

 * @idp: idr handle

 * @nextidp:  pointer to lookup key

 *

 * Returns pointer to registered object with id, which is next number to

 * given id. After being looked up, *@nextidp will be updated for the next

 * iteration.

 *

 * This function can be called under rcu_read_lock(), given that the leaf

 * pointers lifetimes are correctly managed.

 */

void *idr_get_next(struct idr *idp, int *nextidp)

{

	struct idr_layer *p, *pa[MAX_IDR_LEVEL + 1];

	struct idr_layer **paa = &pa[0];

	int id = *nextidp;

	int n, max;

	/* find first ent */

	p = rcu_dereference_raw(idp->top);

	if (!p)

		return NULL;

	n = (p->layer + 1) * IDR_BITS;

	max = idr_max(p->layer + 1);

	while (id >= 0 && id <= max) {

		while (n > 0 && p) {

			n -= IDR_BITS;

			*paa++ = p;

			p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);

		}

		if (p) {

			*nextidp = id;

			return p;

		}

		/*

		 * Proceed to the next layer at the current level.  Unlike

		 * idr_for_each(), @id isn't guaranteed to be aligned to

		 * layer boundary at this point and adding 1 << n may

		 * incorrectly skip IDs.  Make sure we jump to the

		 * beginning of the next layer using round_up().

		 */

		id = round_up(id + 1, 1 << n);

		while (n < fls(id)) {

			n += IDR_BITS;

			p = *--paa;

		}

	}

	return NULL;

}

EXPORT_SYMBOL(idr_get_next);

/**

 * 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;

	if (id < 0)

		return ERR_PTR(-EINVAL);

	p = idp->top;

	if (!p)

		return ERR_PTR(-EINVAL);

	n = (p->layer+1) * IDR_BITS;

	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);

void __init idr_init_cache(void)

{

    //idr_layer_cache = kmem_cache_create("idr_layer_cache",

    //           sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);

}

/**

 * 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);

/**

 * DOC: IDA description

 * 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 

 */

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

 * @starting_id: id to start search at

 * @p_id:	pointer to the allocated handle

 *

 * Allocate new ID above or equal to @starting_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 ida_pre_get() call.  If the ida is full, it will

 * return %-ENOSPC.

 *

 * @p_id returns a value in the range @starting_id ... %0x7fffffff.

 */

int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)

{

	struct idr_layer *pa[MAX_IDR_LEVEL + 1];

	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, 0, &ida->idr);

	if (t < 0)

		return t == -ENOMEM ? -EAGAIN : t;

	if (t * IDA_BITMAP_BITS >= MAX_IDR_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_IDR_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)

			kfree(p);

	}

	return 0;

}

EXPORT_SYMBOL(ida_get_new_above);

/**

 * 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:

	WARN(1, "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_simple_get - get a new id.

 * @ida: the (initialized) ida.

 * @start: the minimum id (inclusive, < 0x8000000)

 * @end: the maximum id (exclusive, < 0x8000000 or 0)

 * @gfp_mask: memory allocation flags

 *

 * Allocates an id in the range start <= id < end, or returns -ENOSPC.

 * On memory allocation failure, returns -ENOMEM.

 *

 * Use ida_simple_remove() to get rid of an id.

 */

int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,

		   gfp_t gfp_mask)

{

	int ret, id;

	unsigned int max;

	unsigned long flags;

	BUG_ON((int)start < 0);

	BUG_ON((int)end < 0);

	if (end == 0)

		max = 0x80000000;

	else {

		BUG_ON(end < start);

		max = end - 1;

	}

again:

	if (!ida_pre_get(ida, gfp_mask))

		return -ENOMEM;

	spin_lock_irqsave(&simple_ida_lock, flags);

	ret = ida_get_new_above(ida, start, &id);

	if (!ret) {

		if (id > max) {

			ida_remove(ida, id);