Initial import of modified Linux 2.6.28 tree

Original upstream URL:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git | branch linux-2.6.28.y

1 files changed, 886 insertions, 0 deletions

diff --git a/lib/idr.c b/lib/idr.c
new file mode 100644
index 0000000..21154ae
--- /dev/null
+++ b/lib/idr.c
@@ -0,0 +1,886 @@
+/*
+ * 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.
+ */
+
+#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 *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);
+	kmem_cache_free(idr_layer_cache, layer);
+}
+
+static inline void free_layer(struct idr_layer *p)
+{
+	call_rcu(&p->rcu_head, idr_layer_rcu_free);
+}
+
+/* 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, gfp_t gfp_mask)
+{
+	while (idp->id_free_cnt < IDR_FREE_MAX) {
+		struct idr_layer *new;
+		new = kmem_cache_zalloc(idr_layer_cache, 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 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)
+		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.
+		 */
+		kmem_cache_free(idr_layer_cache, 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;
+	max = 1 << n;
+
+	id = 0;
+	while (id < max) {
+		while (n > IDR_BITS && p) {
+			n -= IDR_BITS;
+			*paa++ = p;
+			p = p->ary[(id >> n) & IDR_MASK];
+		}
+
+		id += 1 << n;
+		while (n < fls(id)) {
+			if (p)
+				free_layer(p);
+			n += IDR_BITS;
+			p = *--paa;
+		}
+	}
+	rcu_assign_pointer(idp->top, NULL);
+	idp->layers = 0;
+}
+EXPORT_SYMBOL(idr_remove_all);
+
+/**
+ * idr_destroy - release all cached layers within an idr tree
+ * idp: idr handle
+ */
+void idr_destroy(struct idr *idp)
+{
+	while (idp->id_free_cnt) {
+		struct idr_layer *p = get_from_free_list(idp);
+		kmem_cache_free(idr_layer_cache, p);
+	}
+}
+EXPORT_SYMBOL(idr_destroy);
+
+/**
+ * idr_find - return pointer for given id
+ * @idp: idr handle
+ * @id: lookup key
+ *
+ * Return the pointer given the id it has been registered with.  A %NULL
+ * return indicates that @id is not valid or you passed %NULL in
+ * idr_get_new().
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
+ */
+void *idr_find(struct idr *idp, int id)
+{
+	int n;
+	struct idr_layer *p;
+
+	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);
+
+/**
+ * idr_for_each - iterate through all stored pointers
+ * @idp: idr handle
+ * @fn: function to be called for each pointer
+ * @data: data passed back to callback function
+ *
+ * Iterate over the pointers registered with the given idr.  The
+ * callback function will be called for each pointer currently
+ * registered, passing the id, the pointer and the data pointer passed
+ * to this function.  It is not safe to modify the idr tree while in
+ * the callback, so functions such as idr_get_new and idr_remove are
+ * not allowed.
+ *
+ * We check the return of @fn each time. If it returns anything other
+ * than 0, we break out and return that value.
+ *
+ * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
+ */
+int idr_for_each(struct idr *idp,
+		 int (*fn)(int id, void *p, void *data), void *data)
+{
+	int n, id, max, error = 0;
+	struct idr_layer *p;
+	struct idr_layer *pa[MAX_LEVEL];
+	struct idr_layer **paa = &pa[0];
+
+	n = idp->layers * IDR_BITS;
+	p = rcu_dereference(idp->top);
+	max = 1 << n;
+
+	id = 0;
+	while (id < max) {
+		while (n > 0 && p) {
+			n -= IDR_BITS;
+			*paa++ = p;
+			p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
+		}
+
+		if (p) {
+			error = fn(id, (void *)p, data);
+			if (error)
+				break;
+		}
+
+		id += 1 << n;
+		while (n < fls(id)) {
+			n += IDR_BITS;
+			p = *--paa;
+		}
+	}
+
+	return error;
+}
+EXPORT_SYMBOL(idr_for_each);
+
+/**
+ * idr_replace - replace pointer for given id
+ * @idp: idr handle
+ * @ptr: pointer you want associated with the id
+ * @id: lookup key
+ *
+ * Replace the pointer registered with an id and return the old value.
+ * A -ENOENT return indicates that @id was not found.
+ * A -EINVAL return indicates that @id was not within valid constraints.
+ *
+ * The caller must serialize with writers.
+ */
+void *idr_replace(struct idr *idp, void *ptr, int id)
+{
+	int n;
+	struct idr_layer *p, *old_p;
+
+	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);
+
+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);
+
+
+/*
+ * 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 <htejun@gmail.com>
+ */
+
+static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
+{
+	unsigned long flags;
+
+	if (!ida->free_bitmap) {
+		spin_lock_irqsave(&ida->idr.lock, flags);
+		if (!ida->free_bitmap) {
+			ida->free_bitmap = bitmap;
+			bitmap = NULL;
+		}
+		spin_unlock_irqrestore(&ida->idr.lock, flags);
+	}
+
+	kfree(bitmap);
+}
+
+/**
+ * ida_pre_get - reserve resources for ida allocation
+ * @ida:	ida handle
+ * @gfp_mask:	memory allocation flag
+ *
+ * This function should be called prior to locking and calling the
+ * following function.  It preallocates enough memory to satisfy the
+ * worst possible allocation.
+ *
+ * If the system is REALLY out of memory this function returns 0,
+ * otherwise 1.
+ */
+int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
+{
+	/* allocate idr_layers */
+	if (!idr_pre_get(&ida->idr, gfp_mask))
+		return 0;
+
+	/* allocate free_bitmap */
+	if (!ida->free_bitmap) {
+		struct ida_bitmap *bitmap;
+
+		bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
+		if (!bitmap)
+			return 0;
+
+		free_bitmap(ida, bitmap);
+	}
+
+	return 1;
+}
+EXPORT_SYMBOL(ida_pre_get);
+
+/**
+ * ida_get_new_above - allocate new ID above or equal to a start id
+ * @ida:	ida handle
+ * @staring_id:	id to start search at
+ * @p_id:	pointer to the allocated handle
+ *
+ * Allocate new ID above or equal to @ida.  It should be called with
+ * any required locks.
+ *
+ * If memory is required, it will return -EAGAIN, you should unlock
+ * and go back to the ida_pre_get() call.  If the ida is full, it will
+ * return -ENOSPC.
+ *
+ * @p_id returns a value in the range 0 ... 0x7fffffff.
+ */
+int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
+{
+	struct idr_layer *pa[MAX_LEVEL];
+	struct ida_bitmap *bitmap;
+	unsigned long flags;
+	int idr_id = starting_id / IDA_BITMAP_BITS;
+	int offset = starting_id % IDA_BITMAP_BITS;
+	int t, id;
+
+ restart:
+	/* get vacant slot */
+	t = idr_get_empty_slot(&ida->idr, idr_id, pa);
+	if (t < 0)
+		return _idr_rc_to_errno(t);
+
+	if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
+		return -ENOSPC;
+
+	if (t != idr_id)
+		offset = 0;
+	idr_id = t;
+
+	/* if bitmap isn't there, create a new one */
+	bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
+	if (!bitmap) {
+		spin_lock_irqsave(&ida->idr.lock, flags);
+		bitmap = ida->free_bitmap;
+		ida->free_bitmap = NULL;
+		spin_unlock_irqrestore(&ida->idr.lock, flags);
+
+		if (!bitmap)
+			return -EAGAIN;
+
+		memset(bitmap, 0, sizeof(struct ida_bitmap));
+		rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
+				(void *)bitmap);
+		pa[0]->count++;
+	}
+
+	/* lookup for empty slot */
+	t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
+	if (t == IDA_BITMAP_BITS) {
+		/* no empty slot after offset, continue to the next chunk */
+		idr_id++;
+		offset = 0;
+		goto restart;
+	}
+
+	id = idr_id * IDA_BITMAP_BITS + t;
+	if (id >= MAX_ID_BIT)
+		return -ENOSPC;
+
+	__set_bit(t, bitmap->bitmap);
+	if (++bitmap->nr_busy == IDA_BITMAP_BITS)
+		idr_mark_full(pa, idr_id);
+
+	*p_id = id;
+
+	/* Each leaf node can handle nearly a thousand slots and the
+	 * whole idea of ida is to have small memory foot print.
+	 * Throw away extra resources one by one after each successful
+	 * allocation.
+	 */
+	if (ida->idr.id_free_cnt || ida->free_bitmap) {
+		struct idr_layer *p = get_from_free_list(&ida->idr);
+		if (p)
+			kmem_cache_free(idr_layer_cache, p);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(ida_get_new_above);
+
+/**
+ * ida_get_new - allocate new ID
+ * @ida:	idr handle
+ * @p_id:	pointer to the allocated handle
+ *
+ * Allocate new ID.  It should be called with any required locks.
+ *
+ * If memory is required, it will return -EAGAIN, you should unlock
+ * and go back to the idr_pre_get() call.  If the idr is full, it will
+ * return -ENOSPC.
+ *
+ * @id returns a value in the range 0 ... 0x7fffffff.
+ */
+int ida_get_new(struct ida *ida, int *p_id)
+{
+	return ida_get_new_above(ida, 0, p_id);
+}
+EXPORT_SYMBOL(ida_get_new);
+
+/**
+ * ida_remove - remove the given ID
+ * @ida:	ida handle
+ * @id:		ID to free
+ */
+void ida_remove(struct ida *ida, int id)
+{
+	struct idr_layer *p = ida->idr.top;
+	int shift = (ida->idr.layers - 1) * IDR_BITS;
+	int idr_id = id / IDA_BITMAP_BITS;
+	int offset = id % IDA_BITMAP_BITS;
+	int n;
+	struct ida_bitmap *bitmap;
+
+	/* clear full bits while looking up the leaf idr_layer */
+	while ((shift > 0) && p) {
+		n = (idr_id >> shift) & IDR_MASK;
+		__clear_bit(n, &p->bitmap);
+		p = p->ary[n];
+		shift -= IDR_BITS;
+	}
+
+	if (p == NULL)
+		goto err;
+
+	n = idr_id & IDR_MASK;
+	__clear_bit(n, &p->bitmap);
+
+	bitmap = (void *)p->ary[n];
+	if (!test_bit(offset, bitmap->bitmap))
+		goto err;
+
+	/* update bitmap and remove it if empty */
+	__clear_bit(offset, bitmap->bitmap);
+	if (--bitmap->nr_busy == 0) {
+		__set_bit(n, &p->bitmap);	/* to please idr_remove() */
+		idr_remove(&ida->idr, idr_id);
+		free_bitmap(ida, bitmap);
+	}
+
+	return;
+
+ err:
+	printk(KERN_WARNING
+	       "ida_remove called for id=%d which is not allocated.\n", id);
+}
+EXPORT_SYMBOL(ida_remove);
+
+/**
+ * ida_destroy - release all cached layers within an ida tree
+ * ida:		ida handle
+ */
+void ida_destroy(struct ida *ida)
+{
+	idr_destroy(&ida->idr);
+	kfree(ida->free_bitmap);
+}
+EXPORT_SYMBOL(ida_destroy);
+
+/**
+ * ida_init - initialize ida handle
+ * @ida:	ida handle
+ *
+ * This function is use to set up the handle (@ida) that you will pass
+ * to the rest of the functions.
+ */
+void ida_init(struct ida *ida)
+{
+	memset(ida, 0, sizeof(struct ida));
+	idr_init(&ida->idr);
+
+}
+EXPORT_SYMBOL(ida_init);