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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.
+ *
+ * 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/string.h>
+#include <linux/idr.h>
+
+static kmem_cache_t *idr_layer_cache;
+
+static struct idr_layer *alloc_layer(struct idr *idp)
+{
+ struct idr_layer *p;
+
+ spin_lock(&idp->lock);
+ if ((p = idp->id_free)) {
+ idp->id_free = p->ary[0];
+ idp->id_free_cnt--;
+ p->ary[0] = NULL;
+ }
+ spin_unlock(&idp->lock);
+ return(p);
+}
+
+static void free_layer(struct idr *idp, struct idr_layer *p)
+{
+ /*
+ * Depends on the return element being zeroed.
+ */
+ spin_lock(&idp->lock);
+ p->ary[0] = idp->id_free;
+ idp->id_free = p;
+ idp->id_free_cnt++;
+ spin_unlock(&idp->lock);
+}
+
+/**
+ * idr_pre_get - reserver resources for idr allocation
+ * @idp: idr handle
+ * @gfp_mask: memory allocation flags
+ *
+ * This function should be called prior to locking and calling the
+ * following function. It preallocates enough memory to satisfy
+ * the worst possible allocation.
+ *
+ * If the system is REALLY out of memory this function returns 0,
+ * otherwise 1.
+ */
+int idr_pre_get(struct idr *idp, unsigned gfp_mask)
+{
+ while (idp->id_free_cnt < IDR_FREE_MAX) {
+ struct idr_layer *new;
+ new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
+ if(new == NULL)
+ return (0);
+ free_layer(idp, new);
+ }
+ return 1;
+}
+EXPORT_SYMBOL(idr_pre_get);
+
+static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
+{
+ int n, m, sh;
+ struct idr_layer *p, *new;
+ struct idr_layer *pa[MAX_LEVEL];
+ int l, id;
+ long bm;
+
+ id = *starting_id;
+ p = idp->top;
+ l = idp->layers;
+ pa[l--] = NULL;
+ while (1) {
+ /*
+ * We run around this while until we reach the leaf node...
+ */
+ n = (id >> (IDR_BITS*l)) & IDR_MASK;
+ bm = ~p->bitmap;
+ m = find_next_bit(&bm, IDR_SIZE, n);
+ if (m == IDR_SIZE) {
+ /* no space available go back to previous layer. */
+ l++;
+ id = (id | ((1 << (IDR_BITS*l))-1)) + 1;
+ if (!(p = pa[l])) {
+ *starting_id = id;
+ return -2;
+ }
+ continue;
+ }
+ if (m != n) {
+ sh = IDR_BITS*l;
+ id = ((id >> sh) ^ n ^ m) << sh;
+ }
+ if ((id >= MAX_ID_BIT) || (id < 0))
+ return -3;
+ if (l == 0)
+ break;
+ /*
+ * Create the layer below if it is missing.
+ */
+ if (!p->ary[m]) {
+ if (!(new = alloc_layer(idp)))
+ return -1;
+ p->ary[m] = new;
+ p->count++;
+ }
+ pa[l--] = p;
+ p = p->ary[m];
+ }
+ /*
+ * We have reached the leaf node, plant the
+ * users pointer and return the raw id.
+ */
+ p->ary[m] = (struct idr_layer *)ptr;
+ __set_bit(m, &p->bitmap);
+ p->count++;
+ /*
+ * If this layer is full mark the bit in the layer above
+ * to show that this part of the radix tree is full.
+ * This may complete the layer above and require walking
+ * up the radix tree.
+ */
+ n = id;
+ while (p->bitmap == IDR_FULL) {
+ if (!(p = pa[++l]))
+ break;
+ n = n >> IDR_BITS;
+ __set_bit((n & IDR_MASK), &p->bitmap);
+ }
+ return(id);
+}
+
+static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
+{
+ struct idr_layer *p, *new;
+ int layers, v, id;
+
+ id = starting_id;
+build_up:
+ p = idp->top;
+ layers = idp->layers;
+ if (unlikely(!p)) {
+ if (!(p = alloc_layer(idp)))
+ return -1;
+ layers = 1;
+ }
+ /*
+ * Add a new layer to the top of the tree if the requested
+ * id is larger than the currently allocated space.
+ */
+ while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDR_BITS)))) {
+ layers++;
+ if (!p->count)
+ continue;
+ if (!(new = alloc_layer(idp))) {
+ /*
+ * The allocation failed. If we built part of
+ * the structure tear it down.
+ */
+ for (new = p; p && p != idp->top; new = p) {
+ p = p->ary[0];
+ new->ary[0] = NULL;
+ new->bitmap = new->count = 0;
+ free_layer(idp, new);
+ }
+ return -1;
+ }
+ new->ary[0] = p;
+ new->count = 1;
+ if (p->bitmap == IDR_FULL)
+ __set_bit(0, &new->bitmap);
+ p = new;
+ }
+ idp->top = p;
+ idp->layers = layers;
+ v = sub_alloc(idp, ptr, &id);
+ if (v == -2)
+ goto build_up;
+ return(v);
+}
+
+/**
+ * idr_get_new_above - allocate new idr entry above a start id
+ * @idp: idr handle
+ * @ptr: pointer you want associated with the ide
+ * @start_id: id to start search at
+ * @id: pointer to the allocated handle
+ *
+ * This is the allocate id function. It should be called with any
+ * required locks.
+ *
+ * If memory is required, it will return -EAGAIN, you should unlock
+ * and go back to the idr_pre_get() call. If the idr is full, it will
+ * return -ENOSPC.
+ *
+ * @id returns a value in the range 0 ... 0x7fffffff
+ */
+int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
+{
+ int rv;
+ rv = idr_get_new_above_int(idp, ptr, starting_id);
+ /*
+ * This is a cheap hack until the IDR code can be fixed to
+ * return proper error values.
+ */
+ if (rv < 0) {
+ if (rv == -1)
+ return -EAGAIN;
+ else /* Will be -3 */
+ return -ENOSPC;
+ }
+ *id = rv;
+ return 0;
+}
+EXPORT_SYMBOL(idr_get_new_above);
+
+/**
+ * idr_get_new - allocate new idr entry
+ * @idp: idr handle
+ * @ptr: pointer you want associated with the ide
+ * @id: pointer to the allocated handle
+ *
+ * This is the allocate id function. It should be called with any
+ * required locks.
+ *
+ * If memory is required, it will return -EAGAIN, you should unlock
+ * and go back to the idr_pre_get() call. If the idr is full, it will
+ * return -ENOSPC.
+ *
+ * @id returns a value in the range 0 ... 0x7fffffff
+ */
+int idr_get_new(struct idr *idp, void *ptr, int *id)
+{
+ int rv;
+ rv = idr_get_new_above_int(idp, ptr, 0);
+ /*
+ * This is a cheap hack until the IDR code can be fixed to
+ * return proper error values.
+ */
+ if (rv < 0) {
+ if (rv == -1)
+ return -EAGAIN;
+ else /* Will be -3 */
+ return -ENOSPC;
+ }
+ *id = rv;
+ return 0;
+}
+EXPORT_SYMBOL(idr_get_new);
+
+static void idr_remove_warning(int id)
+{
+ printk("idr_remove called for id=%d which is not allocated.\n", id);
+ dump_stack();
+}
+
+static void sub_remove(struct idr *idp, int shift, int id)
+{
+ struct idr_layer *p = idp->top;
+ struct idr_layer **pa[MAX_LEVEL];
+ struct idr_layer ***paa = &pa[0];
+ int n;
+
+ *paa = NULL;
+ *++paa = &idp->top;
+
+ while ((shift > 0) && p) {
+ n = (id >> shift) & IDR_MASK;
+ __clear_bit(n, &p->bitmap);
+ *++paa = &p->ary[n];
+ p = p->ary[n];
+ shift -= IDR_BITS;
+ }
+ n = id & IDR_MASK;
+ if (likely(p != NULL && test_bit(n, &p->bitmap))){
+ __clear_bit(n, &p->bitmap);
+ p->ary[n] = NULL;
+ while(*paa && ! --((**paa)->count)){
+ free_layer(idp, **paa);
+ **paa-- = NULL;
+ }
+ if ( ! *paa )
+ idp->layers = 0;
+ } else {
+ idr_remove_warning(id);
+ }
+}
+
+/**
+ * idr_remove - remove the given id and free it's slot
+ * idp: idr handle
+ * id: uniqueue key
+ */
+void idr_remove(struct idr *idp, int id)
+{
+ struct idr_layer *p;
+
+ /* Mask off upper bits we don't use for the search. */
+ id &= MAX_ID_MASK;
+
+ sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
+ if ( idp->top && idp->top->count == 1 &&
+ (idp->layers > 1) &&
+ idp->top->ary[0]){ // We can drop a layer
+
+ p = idp->top->ary[0];
+ idp->top->bitmap = idp->top->count = 0;
+ free_layer(idp, idp->top);
+ idp->top = p;
+ --idp->layers;
+ }
+ while (idp->id_free_cnt >= IDR_FREE_MAX) {
+
+ p = alloc_layer(idp);
+ kmem_cache_free(idr_layer_cache, p);
+ return;
+ }
+}
+EXPORT_SYMBOL(idr_remove);
+
+/**
+ * idr_find - return pointer for given id
+ * @idp: idr handle
+ * @id: lookup key
+ *
+ * Return the pointer given the id it has been registered with. A %NULL
+ * return indicates that @id is not valid or you passed %NULL in
+ * idr_get_new().
+ *
+ * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
+ */
+void *idr_find(struct idr *idp, int id)
+{
+ int n;
+ struct idr_layer *p;
+
+ n = idp->layers * IDR_BITS;
+ p = idp->top;
+
+ /* Mask off upper bits we don't use for the search. */
+ id &= MAX_ID_MASK;
+
+ if (id >= (1 << n))
+ return NULL;
+
+ while (n > 0 && p) {
+ n -= IDR_BITS;
+ p = p->ary[(id >> n) & IDR_MASK];
+ }
+ return((void *)p);
+}
+EXPORT_SYMBOL(idr_find);
+
+static void idr_cache_ctor(void * idr_layer,
+ kmem_cache_t *idr_layer_cache, unsigned long flags)
+{
+ memset(idr_layer, 0, sizeof(struct idr_layer));
+}
+
+static int init_id_cache(void)
+{
+ if (!idr_layer_cache)
+ idr_layer_cache = kmem_cache_create("idr_layer_cache",
+ sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
+ return 0;
+}
+
+/**
+ * idr_init - initialize idr handle
+ * @idp: idr handle
+ *
+ * This function is use to set up the handle (@idp) that you will pass
+ * to the rest of the functions.
+ */
+void idr_init(struct idr *idp)
+{
+ init_id_cache();
+ memset(idp, 0, sizeof(struct idr));
+ spin_lock_init(&idp->lock);
+}
+EXPORT_SYMBOL(idr_init);
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