Initial import

1 files changed, 1147 insertions, 0 deletions

diff --git a/lib/idr.c b/lib/idr.c
new file mode 100644
index 000000000..5335c43ad
--- /dev/null
+++ b/lib/idr.c
@@ -0,0 +1,1147 @@
+/*
+ * 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.
+ */
+
+#ifndef TEST                        // to test in user space...
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#endif
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/idr.h>
+#include <linux/spinlock.h>
+#include <linux/percpu.h>
+
+#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 kmem_cache *idr_layer_cache;
+static DEFINE_PER_CPU(struct idr_layer *, idr_preload_head);
+static DEFINE_PER_CPU(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.  We want to try this
+	 * before preload buffer; otherwise, non-preloading idr_alloc()
+	 * users will end up taking advantage of preloading ones.  As the
+	 * following is allowed to fail for preloaded cases, suppress
+	 * warning this time.
+	 */
+	new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN);
+	if (new)
+		return new;
+
+	/*
+	 * Try to fetch one from the per-cpu preload buffer if in process
+	 * context.  See idr_preload() for details.
+	 */
+	if (!in_interrupt()) {
+		preempt_disable();
+		new = __this_cpu_read(idr_preload_head);
+		if (new) {
+			__this_cpu_write(idr_preload_head, new->ary[0]);
+			__this_cpu_dec(idr_preload_cnt);
+			new->ary[0] = NULL;
+		}
+		preempt_enable();
+		if (new)
+			return new;
+	}
+
+	/*
+	 * Both failed.  Try kmem_cache again w/o adding __GFP_NOWARN so
+	 * that memory allocation failure warning is printed as intended.
+	 */
+	return kmem_cache_zalloc(idr_layer_cache, gfp_mask);
+}
+
+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 *idr, struct idr_layer *p)
+{
+	if (idr->hint == p)
+		RCU_INIT_POINTER(idr->hint, NULL);
+	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 (bitmap_full(p->bitmap, IDR_SIZE)) {
+		if (!(p = pa[++l]))
+			break;
+		id = id >> IDR_BITS;
+		__set_bit((id & IDR_MASK), p->bitmap);
+	}
+}
+
+static int __idr_pre_get(struct idr *idp, gfp_t gfp_mask)
+{
+	while (idp->id_free_cnt < MAX_IDR_FREE) {
+		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;
+}
+
+/**
+ * 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 > idr_max(idp->layers)) {
+				*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);
+}
+
+
+/**
+ * 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)
+{
+	/*
+	 * Consuming preload buffer from non-process context breaks preload
+	 * allocation guarantee.  Disallow usage from those contexts.
+	 */
+	WARN_ON_ONCE(in_interrupt());
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+
+	preempt_disable();
+
+	/*
+	 * 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 (__this_cpu_read(idr_preload_cnt) < MAX_IDR_FREE) {
+		struct idr_layer *new;
+
+		preempt_enable();
+		new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
+		preempt_disable();
+		if (!new)
+			break;
+
+		/* link the new one to per-cpu preload list */
+		new->ary[0] = __this_cpu_read(idr_preload_head);
+		__this_cpu_write(idr_preload_head, new);
+		__this_cpu_inc(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;
+
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+
+	/* 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_INIT_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;
+
+	if (id > idr_max(idp->layers)) {
+		idr_remove_warning(id);
+		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);
+	}
+}
+EXPORT_SYMBOL(idr_remove);
+
+static 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;
+	*paa = idp->top;
+	RCU_INIT_POINTER(idp->top, NULL);
+	max = idr_max(idp->layers);
+
+	id = 0;
+	while (id >= 0 && id <= max) {
+		p = *paa;
+		while (n > IDR_BITS && p) {
+			n -= IDR_BITS;
+			p = p->ary[(id >> n) & IDR_MASK];
+			*++paa = p;
+		}
+
+		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 (*paa)
+				free_layer(idp, *paa);
+			n += IDR_BITS;
+			--paa;
+		}
+	}
+	idp->layers = 0;
+}
+
+/**
+ * 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 necessary, 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);
+		kmem_cache_free(idr_layer_cache, 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;
+	*paa = rcu_dereference_raw(idp->top);
+	max = idr_max(idp->layers);
+
+	id = 0;
+	while (id >= 0 && id <= max) {
+		p = *paa;
+		while (n > 0 && p) {
+			n -= IDR_BITS;
+			p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
+			*++paa = p;
+		}
+
+		if (p) {
+			error = fn(id, (void *)p, data);
+			if (error)
+				break;
+		}
+
+		id += 1 << n;
+		while (n < fls(id)) {
+			n += IDR_BITS;
+			--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 = *paa = 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) {
+		p = *paa;
+		while (n > 0 && p) {
+			n -= IDR_BITS;
+			p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
+			*++paa = p;
+		}
+
+		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;
+			--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(-ENOENT);
+
+	if (id > idr_max(p->layer + 1))
+		return ERR_PTR(-ENOENT);
+
+	n = p->layer * 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);
+
+static int idr_has_entry(int id, void *p, void *data)
+{
+	return 1;
+}
+
+bool idr_is_empty(struct idr *idp)
+{
+	return !idr_for_each(idp, idr_has_entry, NULL);
+}
+EXPORT_SYMBOL(idr_is_empty);
+
+/**
+ * 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 <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
+ * @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)
+			kmem_cache_free(idr_layer_cache, 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;
+
+	if (idr_id > idr_max(ida->idr.layers))
+		goto err;
+
+	/* 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 (!bitmap || !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);
+			ret = -ENOSPC;
+		} else {
+			ret = id;
+		}
+	}
+	spin_unlock_irqrestore(&simple_ida_lock, flags);
+
+	if (unlikely(ret == -EAGAIN))
+		goto again;
+
+	return ret;
+}
+EXPORT_SYMBOL(ida_simple_get);
+
+/**
+ * ida_simple_remove - remove an allocated id.
+ * @ida: the (initialized) ida.
+ * @id: the id returned by ida_simple_get.
+ */
+void ida_simple_remove(struct ida *ida, unsigned int id)
+{
+	unsigned long flags;
+
+	BUG_ON((int)id < 0);
+	spin_lock_irqsave(&simple_ida_lock, flags);
+	ida_remove(ida, id);
+	spin_unlock_irqrestore(&simple_ida_lock, flags);
+}
+EXPORT_SYMBOL(ida_simple_remove);
+
+/**
+ * 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);