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 * Modified by Nadia Derbey to make it RCU safe.
11 * Small id to pointer translation service.
13 * It uses a radix tree like structure as a sparse array indexed
14 * by the id to obtain the pointer. The bitmap makes allocating
17 * You call it to allocate an id (an int) an associate with that id a
18 * pointer or what ever, we treat it as a (void *). You can pass this
19 * id to a user for him to pass back at a later time. You then pass
20 * that id to this code and it returns your pointer.
22 * You can release ids at any time. When all ids are released, most of
23 * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
24 * don't need to go to the memory "store" during an id allocate, just
25 * so you don't need to be too concerned about locking and conflicts
26 * with the slab allocator.
29 #ifndef TEST // to test in user space...
30 #include <linux/slab.h>
31 #include <linux/init.h>
32 #include <linux/module.h>
34 #include <linux/err.h>
35 #include <linux/string.h>
36 #include <linux/idr.h>
38 static struct kmem_cache *idr_layer_cache;
40 static struct idr_layer *get_from_free_list(struct idr *idp)
45 spin_lock_irqsave(&idp->lock, flags);
46 if ((p = idp->id_free)) {
47 idp->id_free = p->ary[0];
51 spin_unlock_irqrestore(&idp->lock, flags);
55 static void idr_layer_rcu_free(struct rcu_head *head)
57 struct idr_layer *layer;
59 layer = container_of(head, struct idr_layer, rcu_head);
60 kmem_cache_free(idr_layer_cache, layer);
63 static inline void free_layer(struct idr_layer *p)
65 call_rcu(&p->rcu_head, idr_layer_rcu_free);
68 /* only called when idp->lock is held */
69 static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
71 p->ary[0] = idp->id_free;
76 static void move_to_free_list(struct idr *idp, struct idr_layer *p)
81 * Depends on the return element being zeroed.
83 spin_lock_irqsave(&idp->lock, flags);
84 __move_to_free_list(idp, p);
85 spin_unlock_irqrestore(&idp->lock, flags);
88 static void idr_mark_full(struct idr_layer **pa, int id)
90 struct idr_layer *p = pa[0];
93 __set_bit(id & IDR_MASK, &p->bitmap);
95 * If this layer is full mark the bit in the layer above to
96 * show that this part of the radix tree is full. This may
97 * complete the layer above and require walking up the radix
100 while (p->bitmap == IDR_FULL) {
104 __set_bit((id & IDR_MASK), &p->bitmap);
109 * idr_pre_get - reserver resources for idr allocation
111 * @gfp_mask: memory allocation flags
113 * This function should be called prior to locking and calling the
114 * idr_get_new* functions. It preallocates enough memory to satisfy
115 * the worst possible allocation.
117 * If the system is REALLY out of memory this function returns 0,
120 int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
122 while (idp->id_free_cnt < IDR_FREE_MAX) {
123 struct idr_layer *new;
124 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
127 move_to_free_list(idp, new);
131 EXPORT_SYMBOL(idr_pre_get);
133 static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
136 struct idr_layer *p, *new;
147 * We run around this while until we reach the leaf node...
149 n = (id >> (IDR_BITS*l)) & IDR_MASK;
151 m = find_next_bit(&bm, IDR_SIZE, n);
153 /* no space available go back to previous layer. */
156 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
158 /* if already at the top layer, we need to grow */
159 if (id >= 1 << (idp->layers * IDR_BITS)) {
161 return IDR_NEED_TO_GROW;
166 /* If we need to go up one layer, continue the
167 * loop; otherwise, restart from the top.
169 sh = IDR_BITS * (l + 1);
170 if (oid >> sh == id >> sh)
177 id = ((id >> sh) ^ n ^ m) << sh;
179 if ((id >= MAX_ID_BIT) || (id < 0))
180 return IDR_NOMORE_SPACE;
184 * Create the layer below if it is missing.
187 new = get_from_free_list(idp);
191 rcu_assign_pointer(p->ary[m], new);
202 static int idr_get_empty_slot(struct idr *idp, int starting_id,
203 struct idr_layer **pa)
205 struct idr_layer *p, *new;
212 layers = idp->layers;
214 if (!(p = get_from_free_list(idp)))
220 * Add a new layer to the top of the tree if the requested
221 * id is larger than the currently allocated space.
223 while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
226 /* special case: if the tree is currently empty,
227 * then we grow the tree by moving the top node
233 if (!(new = get_from_free_list(idp))) {
235 * The allocation failed. If we built part of
236 * the structure tear it down.
238 spin_lock_irqsave(&idp->lock, flags);
239 for (new = p; p && p != idp->top; new = p) {
242 new->bitmap = new->count = 0;
243 __move_to_free_list(idp, new);
245 spin_unlock_irqrestore(&idp->lock, flags);
250 new->layer = layers-1;
251 if (p->bitmap == IDR_FULL)
252 __set_bit(0, &new->bitmap);
255 rcu_assign_pointer(idp->top, p);
256 idp->layers = layers;
257 v = sub_alloc(idp, &id, pa);
258 if (v == IDR_NEED_TO_GROW)
263 static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
265 struct idr_layer *pa[MAX_LEVEL];
268 id = idr_get_empty_slot(idp, starting_id, pa);
271 * Successfully found an empty slot. Install the user
272 * pointer and mark the slot full.
274 rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
275 (struct idr_layer *)ptr);
277 idr_mark_full(pa, id);
284 * idr_get_new_above - allocate new idr entry above or equal to a start id
286 * @ptr: pointer you want associated with the id
287 * @start_id: id to start search at
288 * @id: pointer to the allocated handle
290 * This is the allocate id function. It should be called with any
293 * If memory is required, it will return -EAGAIN, you should unlock
294 * and go back to the idr_pre_get() call. If the idr is full, it will
297 * @id returns a value in the range @starting_id ... 0x7fffffff
299 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
303 rv = idr_get_new_above_int(idp, ptr, starting_id);
305 * This is a cheap hack until the IDR code can be fixed to
306 * return proper error values.
309 return _idr_rc_to_errno(rv);
313 EXPORT_SYMBOL(idr_get_new_above);
316 * idr_get_new - allocate new idr entry
318 * @ptr: pointer you want associated with the id
319 * @id: pointer to the allocated handle
321 * This is the allocate id function. It should be called with any
324 * If memory is required, it will return -EAGAIN, you should unlock
325 * and go back to the idr_pre_get() call. If the idr is full, it will
328 * @id returns a value in the range 0 ... 0x7fffffff
330 int idr_get_new(struct idr *idp, void *ptr, int *id)
334 rv = idr_get_new_above_int(idp, ptr, 0);
336 * This is a cheap hack until the IDR code can be fixed to
337 * return proper error values.
340 return _idr_rc_to_errno(rv);
344 EXPORT_SYMBOL(idr_get_new);
346 static void idr_remove_warning(int id)
349 "idr_remove called for id=%d which is not allocated.\n", id);
353 static void sub_remove(struct idr *idp, int shift, int id)
355 struct idr_layer *p = idp->top;
356 struct idr_layer **pa[MAX_LEVEL];
357 struct idr_layer ***paa = &pa[0];
358 struct idr_layer *to_free;
364 while ((shift > 0) && p) {
365 n = (id >> shift) & IDR_MASK;
366 __clear_bit(n, &p->bitmap);
372 if (likely(p != NULL && test_bit(n, &p->bitmap))){
373 __clear_bit(n, &p->bitmap);
374 rcu_assign_pointer(p->ary[n], NULL);
376 while(*paa && ! --((**paa)->count)){
387 idr_remove_warning(id);
391 * idr_remove - remove the given id and free it's slot
395 void idr_remove(struct idr *idp, int id)
398 struct idr_layer *to_free;
400 /* Mask off upper bits we don't use for the search. */
403 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
404 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
407 * Single child at leftmost slot: we can shrink the tree.
408 * This level is not needed anymore since when layers are
409 * inserted, they are inserted at the top of the existing
413 p = idp->top->ary[0];
414 rcu_assign_pointer(idp->top, p);
416 to_free->bitmap = to_free->count = 0;
419 while (idp->id_free_cnt >= IDR_FREE_MAX) {
420 p = get_from_free_list(idp);
422 * Note: we don't call the rcu callback here, since the only
423 * layers that fall into the freelist are those that have been
426 kmem_cache_free(idr_layer_cache, p);
430 EXPORT_SYMBOL(idr_remove);
433 * idr_remove_all - remove all ids from the given idr tree
436 * idr_destroy() only frees up unused, cached idp_layers, but this
437 * function will remove all id mappings and leave all idp_layers
440 * A typical clean-up sequence for objects stored in an idr tree, will
441 * use idr_for_each() to free all objects, if necessay, then
442 * idr_remove_all() to remove all ids, and idr_destroy() to free
443 * up the cached idr_layers.
445 void idr_remove_all(struct idr *idp)
450 struct idr_layer *pa[MAX_LEVEL];
451 struct idr_layer **paa = &pa[0];
453 n = idp->layers * IDR_BITS;
455 rcu_assign_pointer(idp->top, NULL);
460 while (n > IDR_BITS && p) {
463 p = p->ary[(id >> n) & IDR_MASK];
468 /* Get the highest bit that the above add changed from 0->1. */
469 while (n < fls(id ^ bt_mask)) {
478 EXPORT_SYMBOL(idr_remove_all);
481 * idr_destroy - release all cached layers within an idr tree
484 void idr_destroy(struct idr *idp)
486 while (idp->id_free_cnt) {
487 struct idr_layer *p = get_from_free_list(idp);
488 kmem_cache_free(idr_layer_cache, p);
491 EXPORT_SYMBOL(idr_destroy);
494 * idr_find - return pointer for given id
498 * Return the pointer given the id it has been registered with. A %NULL
499 * return indicates that @id is not valid or you passed %NULL in
502 * This function can be called under rcu_read_lock(), given that the leaf
503 * pointers lifetimes are correctly managed.
505 void *idr_find(struct idr *idp, int id)
510 p = rcu_dereference_raw(idp->top);
513 n = (p->layer+1) * IDR_BITS;
515 /* Mask off upper bits we don't use for the search. */
524 BUG_ON(n != p->layer*IDR_BITS);
525 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
529 EXPORT_SYMBOL(idr_find);
532 * idr_for_each - iterate through all stored pointers
534 * @fn: function to be called for each pointer
535 * @data: data passed back to callback function
537 * Iterate over the pointers registered with the given idr. The
538 * callback function will be called for each pointer currently
539 * registered, passing the id, the pointer and the data pointer passed
540 * to this function. It is not safe to modify the idr tree while in
541 * the callback, so functions such as idr_get_new and idr_remove are
544 * We check the return of @fn each time. If it returns anything other
545 * than 0, we break out and return that value.
547 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
549 int idr_for_each(struct idr *idp,
550 int (*fn)(int id, void *p, void *data), void *data)
552 int n, id, max, error = 0;
554 struct idr_layer *pa[MAX_LEVEL];
555 struct idr_layer **paa = &pa[0];
557 n = idp->layers * IDR_BITS;
558 p = rcu_dereference_raw(idp->top);
566 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
570 error = fn(id, (void *)p, data);
576 while (n < fls(id)) {
584 EXPORT_SYMBOL(idr_for_each);
587 * idr_get_next - lookup next object of id to given id.
589 * @id: pointer to lookup key
591 * Returns pointer to registered object with id, which is next number to
595 void *idr_get_next(struct idr *idp, int *nextidp)
597 struct idr_layer *p, *pa[MAX_LEVEL];
598 struct idr_layer **paa = &pa[0];
603 n = idp->layers * IDR_BITS;
605 p = rcu_dereference_raw(idp->top);
613 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
622 while (n < fls(id)) {
629 EXPORT_SYMBOL(idr_get_next);
633 * idr_replace - replace pointer for given id
635 * @ptr: pointer you want associated with the id
638 * Replace the pointer registered with an id and return the old value.
639 * A -ENOENT return indicates that @id was not found.
640 * A -EINVAL return indicates that @id was not within valid constraints.
642 * The caller must serialize with writers.
644 void *idr_replace(struct idr *idp, void *ptr, int id)
647 struct idr_layer *p, *old_p;
651 return ERR_PTR(-EINVAL);
653 n = (p->layer+1) * IDR_BITS;
658 return ERR_PTR(-EINVAL);
661 while ((n > 0) && p) {
662 p = p->ary[(id >> n) & IDR_MASK];
667 if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
668 return ERR_PTR(-ENOENT);
671 rcu_assign_pointer(p->ary[n], ptr);
675 EXPORT_SYMBOL(idr_replace);
677 void __init idr_init_cache(void)
679 idr_layer_cache = kmem_cache_create("idr_layer_cache",
680 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
684 * idr_init - initialize idr handle
687 * This function is use to set up the handle (@idp) that you will pass
688 * to the rest of the functions.
690 void idr_init(struct idr *idp)
692 memset(idp, 0, sizeof(struct idr));
693 spin_lock_init(&idp->lock);
695 EXPORT_SYMBOL(idr_init);
699 * IDA - IDR based ID allocator
701 * this is id allocator without id -> pointer translation. Memory
702 * usage is much lower than full blown idr because each id only
703 * occupies a bit. ida uses a custom leaf node which contains
704 * IDA_BITMAP_BITS slots.
706 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
709 static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
713 if (!ida->free_bitmap) {
714 spin_lock_irqsave(&ida->idr.lock, flags);
715 if (!ida->free_bitmap) {
716 ida->free_bitmap = bitmap;
719 spin_unlock_irqrestore(&ida->idr.lock, flags);
726 * ida_pre_get - reserve resources for ida allocation
728 * @gfp_mask: memory allocation flag
730 * This function should be called prior to locking and calling the
731 * following function. It preallocates enough memory to satisfy the
732 * worst possible allocation.
734 * If the system is REALLY out of memory this function returns 0,
737 int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
739 /* allocate idr_layers */
740 if (!idr_pre_get(&ida->idr, gfp_mask))
743 /* allocate free_bitmap */
744 if (!ida->free_bitmap) {
745 struct ida_bitmap *bitmap;
747 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
751 free_bitmap(ida, bitmap);
756 EXPORT_SYMBOL(ida_pre_get);
759 * ida_get_new_above - allocate new ID above or equal to a start id
761 * @staring_id: id to start search at
762 * @p_id: pointer to the allocated handle
764 * Allocate new ID above or equal to @ida. It should be called with
765 * any required locks.
767 * If memory is required, it will return -EAGAIN, you should unlock
768 * and go back to the ida_pre_get() call. If the ida is full, it will
771 * @p_id returns a value in the range @starting_id ... 0x7fffffff.
773 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
775 struct idr_layer *pa[MAX_LEVEL];
776 struct ida_bitmap *bitmap;
778 int idr_id = starting_id / IDA_BITMAP_BITS;
779 int offset = starting_id % IDA_BITMAP_BITS;
783 /* get vacant slot */
784 t = idr_get_empty_slot(&ida->idr, idr_id, pa);
786 return _idr_rc_to_errno(t);
788 if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
795 /* if bitmap isn't there, create a new one */
796 bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
798 spin_lock_irqsave(&ida->idr.lock, flags);
799 bitmap = ida->free_bitmap;
800 ida->free_bitmap = NULL;
801 spin_unlock_irqrestore(&ida->idr.lock, flags);
806 memset(bitmap, 0, sizeof(struct ida_bitmap));
807 rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
812 /* lookup for empty slot */
813 t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
814 if (t == IDA_BITMAP_BITS) {
815 /* no empty slot after offset, continue to the next chunk */
821 id = idr_id * IDA_BITMAP_BITS + t;
822 if (id >= MAX_ID_BIT)
825 __set_bit(t, bitmap->bitmap);
826 if (++bitmap->nr_busy == IDA_BITMAP_BITS)
827 idr_mark_full(pa, idr_id);
831 /* Each leaf node can handle nearly a thousand slots and the
832 * whole idea of ida is to have small memory foot print.
833 * Throw away extra resources one by one after each successful
836 if (ida->idr.id_free_cnt || ida->free_bitmap) {
837 struct idr_layer *p = get_from_free_list(&ida->idr);
839 kmem_cache_free(idr_layer_cache, p);
844 EXPORT_SYMBOL(ida_get_new_above);
847 * ida_get_new - allocate new ID
849 * @p_id: pointer to the allocated handle
851 * Allocate new ID. It should be called with any required locks.
853 * If memory is required, it will return -EAGAIN, you should unlock
854 * and go back to the idr_pre_get() call. If the idr is full, it will
857 * @id returns a value in the range 0 ... 0x7fffffff.
859 int ida_get_new(struct ida *ida, int *p_id)
861 return ida_get_new_above(ida, 0, p_id);
863 EXPORT_SYMBOL(ida_get_new);
866 * ida_remove - remove the given ID
870 void ida_remove(struct ida *ida, int id)
872 struct idr_layer *p = ida->idr.top;
873 int shift = (ida->idr.layers - 1) * IDR_BITS;
874 int idr_id = id / IDA_BITMAP_BITS;
875 int offset = id % IDA_BITMAP_BITS;
877 struct ida_bitmap *bitmap;
879 /* clear full bits while looking up the leaf idr_layer */
880 while ((shift > 0) && p) {
881 n = (idr_id >> shift) & IDR_MASK;
882 __clear_bit(n, &p->bitmap);
890 n = idr_id & IDR_MASK;
891 __clear_bit(n, &p->bitmap);
893 bitmap = (void *)p->ary[n];
894 if (!test_bit(offset, bitmap->bitmap))
897 /* update bitmap and remove it if empty */
898 __clear_bit(offset, bitmap->bitmap);
899 if (--bitmap->nr_busy == 0) {
900 __set_bit(n, &p->bitmap); /* to please idr_remove() */
901 idr_remove(&ida->idr, idr_id);
902 free_bitmap(ida, bitmap);
909 "ida_remove called for id=%d which is not allocated.\n", id);
911 EXPORT_SYMBOL(ida_remove);
914 * ida_destroy - release all cached layers within an ida tree
917 void ida_destroy(struct ida *ida)
919 idr_destroy(&ida->idr);
920 kfree(ida->free_bitmap);
922 EXPORT_SYMBOL(ida_destroy);
925 * ida_init - initialize ida handle
928 * This function is use to set up the handle (@ida) that you will pass
929 * to the rest of the functions.
931 void ida_init(struct ida *ida)
933 memset(ida, 0, sizeof(struct ida));
937 EXPORT_SYMBOL(ida_init);