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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 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.

 */

#include 

#include 

#include "drm.h"

#include "drmP.h"

#include "drm_crtc.h"

#define ADDR "=m" (*(volatile long *) addr)

static inline void __set_bit(int nr, volatile void *addr)

{

        asm volatile("bts %1,%0"

                     : ADDR

                     : "Ir" (nr) : "memory");

}

static inline void __clear_bit(int nr, volatile void *addr)

{

        asm volatile("btr %1,%0" : ADDR : "Ir" (nr));

}

static inline int constant_test_bit(int nr, const volatile void *addr)

{

        return ((1UL << (nr % 32)) &

                (((unsigned long *)addr)[nr / 32])) != 0;

}

static inline int variable_test_bit(int nr, volatile const void *addr)

{

        int oldbit;

        asm volatile("bt %2,%1\n\t"

                     "sbb %0,%0"

                     : "=r" (oldbit)

                     : "m" (*(unsigned long *)addr), "Ir" (nr));

        return oldbit;

};

#define test_bit(nr,addr)                       \

        (__builtin_constant_p(nr) ?             \

         constant_test_bit((nr),(addr)) :       \

         variable_test_bit((nr),(addr)))

static inline int fls(int x)

{

        int r;

        __asm__("bsrl %1,%0\n\t"

                "jnz 1f\n\t"

                "movl $-1,%0\n"

                "1:" : "=r" (r) : "rm" (x));

        return r+1;

}

static inline unsigned long __ffs(unsigned long word)

{

        __asm__("bsfl %1,%0"

                :"=r" (word)

                :"rm" (word));

        return word;

}

static inline unsigned find_first_bit(const unsigned long *addr, unsigned size)

{

        unsigned x = 0;

        while (x < size) {

                unsigned long val = *addr++;

                if (val)

                        return __ffs(val) + x;

                x += (sizeof(*addr)<<3);

        }

        return x;

}

int find_next_bit(const unsigned long *addr, int size, int offset)

{

    const unsigned long *p = addr + (offset >> 5);

    int set = 0, bit = offset & 31, res;

    if (bit)

    {

        /*

         * Look for nonzero in the first 32 bits:

         */

        __asm__("bsfl %1,%0\n\t"

                "jne 1f\n\t"

                "movl $32, %0\n"

                "1:"

                : "=r" (set)

                : "r" (*p >> bit));

        if (set < (32 - bit))

                return set + offset;

        set = 32 - bit;

        p++;

    }

    /*

     * No set bit yet, search remaining full words for a bit

     */

    res = find_first_bit (p, size - 32 * (p - addr));

    return (offset + set + res);

}

#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))

#define rcu_dereference(p)     ({ \

                                typeof(p) _________p1 = ACCESS_ONCE(p); \

                                (_________p1); \

                                })

#define rcu_assign_pointer(p, v) \

        ({ \

                if (!__builtin_constant_p(v) || \

                    ((v) != NULL)) \

                (p) = (v); \

        })

//static struct kmem_cache *idr_layer_cache;

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);

}

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_layer *p)

{

    kfree(p);

}

/* 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 (p->bitmap == IDR_FULL) {

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

			break;

		id = id >> IDR_BITS;

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

	}

}

/**

 * 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

 * idr_get_new* functions. 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, u32_t gfp_mask)

{

   while (idp->id_free_cnt < IDR_FREE_MAX) {

       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);

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

{

	int n, m, sh;

	struct idr_layer *p, *new;

	int l, id, oid;

	unsigned long bm;

	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;

		bm = ~p->bitmap;

		m = find_next_bit(&bm, 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 (!(p = pa[l])) {

				*starting_id = id;

				return IDR_NEED_TO_GROW;

			}

			/* 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_ID_BIT) || (id < 0))

			return IDR_NOMORE_SPACE;

		if (l == 0)

			break;

		/*

		 * Create the layer below if it is missing.

		 */

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

			new = get_from_free_list(idp);

			if (!new)

				return -1;

			new->layer = l-1;

			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)

{

	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 = get_from_free_list(idp)))

			return -1;

		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 ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {

		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++;

			continue;

		}

		if (!(new = get_from_free_list(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;

				__move_to_free_list(idp, new);

			}

//           spin_unlock_irqrestore(&idp->lock, flags);

			return -1;

		}

		new->ary[0] = p;

		new->count = 1;

		new->layer = layers-1;

		if (p->bitmap == IDR_FULL)

			__set_bit(0, &new->bitmap);

		p = new;

	}

	rcu_assign_pointer(idp->top, p);

	idp->layers = layers;

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

	if (v == IDR_NEED_TO_GROW)

		goto build_up;

	return(v);

}

static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)

{

	struct idr_layer *pa[MAX_LEVEL];

	int id;

	id = idr_get_empty_slot(idp, starting_id, pa);

	if (id >= 0) {

		/*

		 * Successfully found an empty slot.  Install the user

		 * pointer and mark the slot full.

		 */

		rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],

				(struct idr_layer *)ptr);

		pa[0]->count++;

		idr_mark_full(pa, id);

	}

	return id;

}

/**

 * 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 @starting_id ... 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)

    {

        dbgprintf("fail\n");

        return _idr_rc_to_errno(rv);

    };

	*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)

		return _idr_rc_to_errno(rv);

	*id = rv;

	return 0;

}

EXPORT_SYMBOL(idr_get_new);

static void idr_remove_warning(int id)

{

	printk(KERN_WARNING

		"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];

	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(to_free);

			to_free = **paa;

			**paa-- = NULL;

		}

		if (!*paa)

			idp->layers = 0;

		if (to_free)

			free_layer(to_free);

	} else

		idr_remove_warning(id);

}

/**

 * idr_remove - remove the given id and free it's slot

 * @idp: idr handle

 * @id: unique key

 */

void idr_remove(struct idr *idp, int id)

{

	struct idr_layer *p;

	struct idr_layer *to_free;

	/* 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]) {

		/*

		 * 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->bitmap = to_free->count = 0;

		free_layer(to_free);

	}

	while (idp->id_free_cnt >= IDR_FREE_MAX) {

		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);

/**

 * idr_remove_all - remove all ids from the given idr tree

 * @idp: idr handle

 *

 * idr_destroy() only frees up unused, cached idp_layers, but this

 * function will remove all id mappings and leave all idp_layers

 * unused.

 *

 * 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_remove_all() to remove all ids, and idr_destroy() to free

 * up the cached idr_layers.

 */

void idr_remove_all(struct idr *idp)

{

	int n, id, max;

	struct idr_layer *p;

	struct idr_layer *pa[MAX_LEVEL];

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

	n = idp->layers * IDR_BITS;

	p = idp->top;

	rcu_assign_pointer(idp->top, NULL);

	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;

		}

	}

	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);

        kfree(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;

	p = rcu_dereference(idp->top);

	if (!p)

		return NULL;

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

	/* Mask off upper bits we don't use for the search. */

	id &= MAX_ID_MASK;

	if (id >= (1 << n))

		return NULL;

	BUG_ON(n == 0);

	while (n > 0 && p) {

		n -= IDR_BITS;

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

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

	}

	return((void *)p);

}

EXPORT_SYMBOL(idr_find);

#if 0

/**

 * 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_get_next - lookup next object of id to given id.

 * @idp: idr handle

 * @id:  pointer to lookup key

 *

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

 * given id.

 */

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

{

	struct idr_layer *p, *pa[MAX_LEVEL];

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

	int id = *nextidp;

	int n, max;

	/* find first ent */

	n = idp->layers * IDR_BITS;

	max = 1 << n;

	p = rcu_dereference(idp->top);

	if (!p)

		return NULL;

	while (id < max) {

		while (n > 0 && p) {

			n -= IDR_BITS;

			*paa++ = p;

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

		}

		if (p) {

			*nextidp = id;

			return p;

		}

		id += 1 << n;

		while (n < fls(id)) {

			n += IDR_BITS;

			p = *--paa;

		}

	}

	return NULL;

}

/**

 * 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;

	p = idp->top;

	if (!p)

		return ERR_PTR(-EINVAL);

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

	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);

#endif

void 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);

#if 0

/*

 * 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

 * @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 @starting_id ... 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);

#endif