2 * 2002-10-18 written by Jim Houston jim.houston@ccur.com
3 * Copyright (C) 2002 by Concurrent Computer Corporation
4 * Distributed under the GNU GPL license version 2.
6 * Modified by George Anzinger to reuse immediately and to use
7 * find bit instructions. Also removed _irq on spinlocks.
9 * Small id to pointer translation service.
11 * It uses a radix tree like structure as a sparse array indexed
12 * by the id to obtain the pointer. The bitmap makes allocating
15 * You call it to allocate an id (an int) an associate with that id a
16 * pointer or what ever, we treat it as a (void *). You can pass this
17 * id to a user for him to pass back at a later time. You then pass
18 * that id to this code and it returns your pointer.
20 * You can release ids at any time. When all ids are released, most of
21 * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
22 * don't need to go to the memory "store" during an id allocate, just
23 * so you don't need to be too concerned about locking and conflicts
24 * with the slab allocator.
27 #ifndef TEST // to test in user space...
28 #include <linux/slab.h>
29 #include <linux/init.h>
30 #include <linux/module.h>
32 #include <linux/string.h>
33 #include <linux/idr.h>
35 static kmem_cache_t *idr_layer_cache;
37 static struct idr_layer *alloc_layer(struct idr *idp)
42 spin_lock_irqsave(&idp->lock, flags);
43 if ((p = idp->id_free)) {
44 idp->id_free = p->ary[0];
48 spin_unlock_irqrestore(&idp->lock, flags);
52 /* only called when idp->lock is held */
53 static void __free_layer(struct idr *idp, struct idr_layer *p)
55 p->ary[0] = idp->id_free;
60 static void free_layer(struct idr *idp, struct idr_layer *p)
65 * Depends on the return element being zeroed.
67 spin_lock_irqsave(&idp->lock, flags);
69 spin_unlock_irqrestore(&idp->lock, flags);
73 * idr_pre_get - reserver resources for idr allocation
75 * @gfp_mask: memory allocation flags
77 * This function should be called prior to locking and calling the
78 * following function. It preallocates enough memory to satisfy
79 * the worst possible allocation.
81 * If the system is REALLY out of memory this function returns 0,
84 int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
86 while (idp->id_free_cnt < IDR_FREE_MAX) {
87 struct idr_layer *new;
88 new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
95 EXPORT_SYMBOL(idr_pre_get);
97 static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
100 struct idr_layer *p, *new;
101 struct idr_layer *pa[MAX_LEVEL];
111 * We run around this while until we reach the leaf node...
113 n = (id >> (IDR_BITS*l)) & IDR_MASK;
115 m = find_next_bit(&bm, IDR_SIZE, n);
117 /* no space available go back to previous layer. */
119 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
128 id = ((id >> sh) ^ n ^ m) << sh;
130 if ((id >= MAX_ID_BIT) || (id < 0))
135 * Create the layer below if it is missing.
138 if (!(new = alloc_layer(idp)))
147 * We have reached the leaf node, plant the
148 * users pointer and return the raw id.
150 p->ary[m] = (struct idr_layer *)ptr;
151 __set_bit(m, &p->bitmap);
154 * If this layer is full mark the bit in the layer above
155 * to show that this part of the radix tree is full.
156 * This may complete the layer above and require walking
160 while (p->bitmap == IDR_FULL) {
164 __set_bit((n & IDR_MASK), &p->bitmap);
169 static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
171 struct idr_layer *p, *new;
178 layers = idp->layers;
180 if (!(p = alloc_layer(idp)))
185 * Add a new layer to the top of the tree if the requested
186 * id is larger than the currently allocated space.
188 while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
192 if (!(new = alloc_layer(idp))) {
194 * The allocation failed. If we built part of
195 * the structure tear it down.
197 spin_lock_irqsave(&idp->lock, flags);
198 for (new = p; p && p != idp->top; new = p) {
201 new->bitmap = new->count = 0;
202 __free_layer(idp, new);
204 spin_unlock_irqrestore(&idp->lock, flags);
209 if (p->bitmap == IDR_FULL)
210 __set_bit(0, &new->bitmap);
214 idp->layers = layers;
215 v = sub_alloc(idp, ptr, &id);
222 * idr_get_new_above - allocate new idr entry above or equal to a start id
224 * @ptr: pointer you want associated with the ide
225 * @start_id: id to start search at
226 * @id: pointer to the allocated handle
228 * This is the allocate id function. It should be called with any
231 * If memory is required, it will return -EAGAIN, you should unlock
232 * and go back to the idr_pre_get() call. If the idr is full, it will
235 * @id returns a value in the range 0 ... 0x7fffffff
237 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
241 rv = idr_get_new_above_int(idp, ptr, starting_id);
243 * This is a cheap hack until the IDR code can be fixed to
244 * return proper error values.
249 else /* Will be -3 */
255 EXPORT_SYMBOL(idr_get_new_above);
258 * idr_get_new - allocate new idr entry
260 * @ptr: pointer you want associated with the ide
261 * @id: pointer to the allocated handle
263 * This is the allocate id function. It should be called with any
266 * If memory is required, it will return -EAGAIN, you should unlock
267 * and go back to the idr_pre_get() call. If the idr is full, it will
270 * @id returns a value in the range 0 ... 0x7fffffff
272 int idr_get_new(struct idr *idp, void *ptr, int *id)
276 rv = idr_get_new_above_int(idp, ptr, 0);
278 * This is a cheap hack until the IDR code can be fixed to
279 * return proper error values.
284 else /* Will be -3 */
290 EXPORT_SYMBOL(idr_get_new);
292 static void idr_remove_warning(int id)
294 printk("idr_remove called for id=%d which is not allocated.\n", id);
298 static void sub_remove(struct idr *idp, int shift, int id)
300 struct idr_layer *p = idp->top;
301 struct idr_layer **pa[MAX_LEVEL];
302 struct idr_layer ***paa = &pa[0];
308 while ((shift > 0) && p) {
309 n = (id >> shift) & IDR_MASK;
310 __clear_bit(n, &p->bitmap);
316 if (likely(p != NULL && test_bit(n, &p->bitmap))){
317 __clear_bit(n, &p->bitmap);
319 while(*paa && ! --((**paa)->count)){
320 free_layer(idp, **paa);
326 idr_remove_warning(id);
330 * idr_remove - remove the given id and free it's slot
334 void idr_remove(struct idr *idp, int id)
338 /* Mask off upper bits we don't use for the search. */
341 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
342 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
343 idp->top->ary[0]) { // We can drop a layer
345 p = idp->top->ary[0];
346 idp->top->bitmap = idp->top->count = 0;
347 free_layer(idp, idp->top);
351 while (idp->id_free_cnt >= IDR_FREE_MAX) {
352 p = alloc_layer(idp);
353 kmem_cache_free(idr_layer_cache, p);
357 EXPORT_SYMBOL(idr_remove);
360 * idr_destroy - release all cached layers within an idr tree
363 void idr_destroy(struct idr *idp)
365 while (idp->id_free_cnt) {
366 struct idr_layer *p = alloc_layer(idp);
367 kmem_cache_free(idr_layer_cache, p);
370 EXPORT_SYMBOL(idr_destroy);
373 * idr_find - return pointer for given id
377 * Return the pointer given the id it has been registered with. A %NULL
378 * return indicates that @id is not valid or you passed %NULL in
381 * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
383 void *idr_find(struct idr *idp, int id)
388 n = idp->layers * IDR_BITS;
391 /* Mask off upper bits we don't use for the search. */
399 p = p->ary[(id >> n) & IDR_MASK];
403 EXPORT_SYMBOL(idr_find);
405 static void idr_cache_ctor(void * idr_layer, kmem_cache_t *idr_layer_cache,
408 memset(idr_layer, 0, sizeof(struct idr_layer));
411 static int init_id_cache(void)
413 if (!idr_layer_cache)
414 idr_layer_cache = kmem_cache_create("idr_layer_cache",
415 sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
420 * idr_init - initialize idr handle
423 * This function is use to set up the handle (@idp) that you will pass
424 * to the rest of the functions.
426 void idr_init(struct idr *idp)
429 memset(idp, 0, sizeof(struct idr));
430 spin_lock_init(&idp->lock);
432 EXPORT_SYMBOL(idr_init);