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;
146 * We run around this while until we reach the leaf node...
148 n = (id >> (IDR_BITS*l)) & IDR_MASK;
150 m = find_next_bit(&bm, IDR_SIZE, n);
152 /* no space available go back to previous layer. */
155 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
157 /* did id go over the limit? */
158 if (id >= (1 << (idp->layers * IDR_BITS))) {
160 return IDR_NEED_TO_GROW;
163 /* If we need to go up one layer, continue the
164 * loop; otherwise, restart from the top.
166 sh = IDR_BITS * (l + 1);
167 if (oid >> sh == id >> sh)
174 id = ((id >> sh) ^ n ^ m) << sh;
176 if ((id >= MAX_ID_BIT) || (id < 0))
177 return IDR_NOMORE_SPACE;
181 * Create the layer below if it is missing.
184 new = get_from_free_list(idp);
188 rcu_assign_pointer(p->ary[m], new);
199 static int idr_get_empty_slot(struct idr *idp, int starting_id,
200 struct idr_layer **pa)
202 struct idr_layer *p, *new;
209 layers = idp->layers;
211 if (!(p = get_from_free_list(idp)))
217 * Add a new layer to the top of the tree if the requested
218 * id is larger than the currently allocated space.
220 while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
223 /* special case: if the tree is currently empty,
224 * then we grow the tree by moving the top node
230 if (!(new = get_from_free_list(idp))) {
232 * The allocation failed. If we built part of
233 * the structure tear it down.
235 spin_lock_irqsave(&idp->lock, flags);
236 for (new = p; p && p != idp->top; new = p) {
239 new->bitmap = new->count = 0;
240 __move_to_free_list(idp, new);
242 spin_unlock_irqrestore(&idp->lock, flags);
247 new->layer = layers-1;
248 if (p->bitmap == IDR_FULL)
249 __set_bit(0, &new->bitmap);
252 rcu_assign_pointer(idp->top, p);
253 idp->layers = layers;
254 v = sub_alloc(idp, &id, pa);
255 if (v == IDR_NEED_TO_GROW)
260 static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
262 struct idr_layer *pa[MAX_LEVEL];
265 id = idr_get_empty_slot(idp, starting_id, pa);
268 * Successfully found an empty slot. Install the user
269 * pointer and mark the slot full.
271 rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
272 (struct idr_layer *)ptr);
274 idr_mark_full(pa, id);
281 * idr_get_new_above - allocate new idr entry above or equal to a start id
283 * @ptr: pointer you want associated with the id
284 * @start_id: id to start search at
285 * @id: pointer to the allocated handle
287 * This is the allocate id function. It should be called with any
290 * If memory is required, it will return -EAGAIN, you should unlock
291 * and go back to the idr_pre_get() call. If the idr is full, it will
294 * @id returns a value in the range @starting_id ... 0x7fffffff
296 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
300 rv = idr_get_new_above_int(idp, ptr, starting_id);
302 * This is a cheap hack until the IDR code can be fixed to
303 * return proper error values.
306 return _idr_rc_to_errno(rv);
310 EXPORT_SYMBOL(idr_get_new_above);
313 * idr_get_new - allocate new idr entry
315 * @ptr: pointer you want associated with the id
316 * @id: pointer to the allocated handle
318 * This is the allocate id function. It should be called with any
321 * If memory is required, it will return -EAGAIN, you should unlock
322 * and go back to the idr_pre_get() call. If the idr is full, it will
325 * @id returns a value in the range 0 ... 0x7fffffff
327 int idr_get_new(struct idr *idp, void *ptr, int *id)
331 rv = idr_get_new_above_int(idp, ptr, 0);
333 * This is a cheap hack until the IDR code can be fixed to
334 * return proper error values.
337 return _idr_rc_to_errno(rv);
341 EXPORT_SYMBOL(idr_get_new);
343 static void idr_remove_warning(int id)
346 "idr_remove called for id=%d which is not allocated.\n", id);
350 static void sub_remove(struct idr *idp, int shift, int id)
352 struct idr_layer *p = idp->top;
353 struct idr_layer **pa[MAX_LEVEL];
354 struct idr_layer ***paa = &pa[0];
355 struct idr_layer *to_free;
361 while ((shift > 0) && p) {
362 n = (id >> shift) & IDR_MASK;
363 __clear_bit(n, &p->bitmap);
369 if (likely(p != NULL && test_bit(n, &p->bitmap))){
370 __clear_bit(n, &p->bitmap);
371 rcu_assign_pointer(p->ary[n], NULL);
373 while(*paa && ! --((**paa)->count)){
384 idr_remove_warning(id);
388 * idr_remove - remove the given id and free it's slot
392 void idr_remove(struct idr *idp, int id)
395 struct idr_layer *to_free;
397 /* Mask off upper bits we don't use for the search. */
400 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
401 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
404 * Single child at leftmost slot: we can shrink the tree.
405 * This level is not needed anymore since when layers are
406 * inserted, they are inserted at the top of the existing
410 p = idp->top->ary[0];
411 rcu_assign_pointer(idp->top, p);
413 to_free->bitmap = to_free->count = 0;
416 while (idp->id_free_cnt >= IDR_FREE_MAX) {
417 p = get_from_free_list(idp);
419 * Note: we don't call the rcu callback here, since the only
420 * layers that fall into the freelist are those that have been
423 kmem_cache_free(idr_layer_cache, p);
427 EXPORT_SYMBOL(idr_remove);
430 * idr_remove_all - remove all ids from the given idr tree
433 * idr_destroy() only frees up unused, cached idp_layers, but this
434 * function will remove all id mappings and leave all idp_layers
437 * A typical clean-up sequence for objects stored in an idr tree, will
438 * use idr_for_each() to free all objects, if necessay, then
439 * idr_remove_all() to remove all ids, and idr_destroy() to free
440 * up the cached idr_layers.
442 void idr_remove_all(struct idr *idp)
446 struct idr_layer *pa[MAX_LEVEL];
447 struct idr_layer **paa = &pa[0];
449 n = idp->layers * IDR_BITS;
451 rcu_assign_pointer(idp->top, NULL);
456 while (n > IDR_BITS && p) {
459 p = p->ary[(id >> n) & IDR_MASK];
463 while (n < fls(id)) {
472 EXPORT_SYMBOL(idr_remove_all);
475 * idr_destroy - release all cached layers within an idr tree
478 void idr_destroy(struct idr *idp)
480 while (idp->id_free_cnt) {
481 struct idr_layer *p = get_from_free_list(idp);
482 kmem_cache_free(idr_layer_cache, p);
485 EXPORT_SYMBOL(idr_destroy);
488 * idr_find - return pointer for given id
492 * Return the pointer given the id it has been registered with. A %NULL
493 * return indicates that @id is not valid or you passed %NULL in
496 * This function can be called under rcu_read_lock(), given that the leaf
497 * pointers lifetimes are correctly managed.
499 void *idr_find(struct idr *idp, int id)
504 p = rcu_dereference(idp->top);
507 n = (p->layer+1) * IDR_BITS;
509 /* Mask off upper bits we don't use for the search. */
518 BUG_ON(n != p->layer*IDR_BITS);
519 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
523 EXPORT_SYMBOL(idr_find);
526 * idr_for_each - iterate through all stored pointers
528 * @fn: function to be called for each pointer
529 * @data: data passed back to callback function
531 * Iterate over the pointers registered with the given idr. The
532 * callback function will be called for each pointer currently
533 * registered, passing the id, the pointer and the data pointer passed
534 * to this function. It is not safe to modify the idr tree while in
535 * the callback, so functions such as idr_get_new and idr_remove are
538 * We check the return of @fn each time. If it returns anything other
539 * than 0, we break out and return that value.
541 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
543 int idr_for_each(struct idr *idp,
544 int (*fn)(int id, void *p, void *data), void *data)
546 int n, id, max, error = 0;
548 struct idr_layer *pa[MAX_LEVEL];
549 struct idr_layer **paa = &pa[0];
551 n = idp->layers * IDR_BITS;
552 p = rcu_dereference(idp->top);
560 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
564 error = fn(id, (void *)p, data);
570 while (n < fls(id)) {
578 EXPORT_SYMBOL(idr_for_each);
581 * idr_get_next - lookup next object of id to given id.
583 * @id: pointer to lookup key
585 * Returns pointer to registered object with id, which is next number to
589 void *idr_get_next(struct idr *idp, int *nextidp)
591 struct idr_layer *p, *pa[MAX_LEVEL];
592 struct idr_layer **paa = &pa[0];
597 n = idp->layers * IDR_BITS;
599 p = rcu_dereference(idp->top);
607 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
616 while (n < fls(id)) {
627 * idr_replace - replace pointer for given id
629 * @ptr: pointer you want associated with the id
632 * Replace the pointer registered with an id and return the old value.
633 * A -ENOENT return indicates that @id was not found.
634 * A -EINVAL return indicates that @id was not within valid constraints.
636 * The caller must serialize with writers.
638 void *idr_replace(struct idr *idp, void *ptr, int id)
641 struct idr_layer *p, *old_p;
645 return ERR_PTR(-EINVAL);
647 n = (p->layer+1) * IDR_BITS;
652 return ERR_PTR(-EINVAL);
655 while ((n > 0) && p) {
656 p = p->ary[(id >> n) & IDR_MASK];
661 if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
662 return ERR_PTR(-ENOENT);
665 rcu_assign_pointer(p->ary[n], ptr);
669 EXPORT_SYMBOL(idr_replace);
671 void __init idr_init_cache(void)
673 idr_layer_cache = kmem_cache_create("idr_layer_cache",
674 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
678 * idr_init - initialize idr handle
681 * This function is use to set up the handle (@idp) that you will pass
682 * to the rest of the functions.
684 void idr_init(struct idr *idp)
686 memset(idp, 0, sizeof(struct idr));
687 spin_lock_init(&idp->lock);
689 EXPORT_SYMBOL(idr_init);
693 * IDA - IDR based ID allocator
695 * this is id allocator without id -> pointer translation. Memory
696 * usage is much lower than full blown idr because each id only
697 * occupies a bit. ida uses a custom leaf node which contains
698 * IDA_BITMAP_BITS slots.
700 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
703 static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
707 if (!ida->free_bitmap) {
708 spin_lock_irqsave(&ida->idr.lock, flags);
709 if (!ida->free_bitmap) {
710 ida->free_bitmap = bitmap;
713 spin_unlock_irqrestore(&ida->idr.lock, flags);
720 * ida_pre_get - reserve resources for ida allocation
722 * @gfp_mask: memory allocation flag
724 * This function should be called prior to locking and calling the
725 * following function. It preallocates enough memory to satisfy the
726 * worst possible allocation.
728 * If the system is REALLY out of memory this function returns 0,
731 int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
733 /* allocate idr_layers */
734 if (!idr_pre_get(&ida->idr, gfp_mask))
737 /* allocate free_bitmap */
738 if (!ida->free_bitmap) {
739 struct ida_bitmap *bitmap;
741 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
745 free_bitmap(ida, bitmap);
750 EXPORT_SYMBOL(ida_pre_get);
753 * ida_get_new_above - allocate new ID above or equal to a start id
755 * @staring_id: id to start search at
756 * @p_id: pointer to the allocated handle
758 * Allocate new ID above or equal to @ida. It should be called with
759 * any required locks.
761 * If memory is required, it will return -EAGAIN, you should unlock
762 * and go back to the ida_pre_get() call. If the ida is full, it will
765 * @p_id returns a value in the range @starting_id ... 0x7fffffff.
767 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
769 struct idr_layer *pa[MAX_LEVEL];
770 struct ida_bitmap *bitmap;
772 int idr_id = starting_id / IDA_BITMAP_BITS;
773 int offset = starting_id % IDA_BITMAP_BITS;
777 /* get vacant slot */
778 t = idr_get_empty_slot(&ida->idr, idr_id, pa);
780 return _idr_rc_to_errno(t);
782 if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
789 /* if bitmap isn't there, create a new one */
790 bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
792 spin_lock_irqsave(&ida->idr.lock, flags);
793 bitmap = ida->free_bitmap;
794 ida->free_bitmap = NULL;
795 spin_unlock_irqrestore(&ida->idr.lock, flags);
800 memset(bitmap, 0, sizeof(struct ida_bitmap));
801 rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
806 /* lookup for empty slot */
807 t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
808 if (t == IDA_BITMAP_BITS) {
809 /* no empty slot after offset, continue to the next chunk */
815 id = idr_id * IDA_BITMAP_BITS + t;
816 if (id >= MAX_ID_BIT)
819 __set_bit(t, bitmap->bitmap);
820 if (++bitmap->nr_busy == IDA_BITMAP_BITS)
821 idr_mark_full(pa, idr_id);
825 /* Each leaf node can handle nearly a thousand slots and the
826 * whole idea of ida is to have small memory foot print.
827 * Throw away extra resources one by one after each successful
830 if (ida->idr.id_free_cnt || ida->free_bitmap) {
831 struct idr_layer *p = get_from_free_list(&ida->idr);
833 kmem_cache_free(idr_layer_cache, p);
838 EXPORT_SYMBOL(ida_get_new_above);
841 * ida_get_new - allocate new ID
843 * @p_id: pointer to the allocated handle
845 * Allocate new ID. It should be called with any required locks.
847 * If memory is required, it will return -EAGAIN, you should unlock
848 * and go back to the idr_pre_get() call. If the idr is full, it will
851 * @id returns a value in the range 0 ... 0x7fffffff.
853 int ida_get_new(struct ida *ida, int *p_id)
855 return ida_get_new_above(ida, 0, p_id);
857 EXPORT_SYMBOL(ida_get_new);
860 * ida_remove - remove the given ID
864 void ida_remove(struct ida *ida, int id)
866 struct idr_layer *p = ida->idr.top;
867 int shift = (ida->idr.layers - 1) * IDR_BITS;
868 int idr_id = id / IDA_BITMAP_BITS;
869 int offset = id % IDA_BITMAP_BITS;
871 struct ida_bitmap *bitmap;
873 /* clear full bits while looking up the leaf idr_layer */
874 while ((shift > 0) && p) {
875 n = (idr_id >> shift) & IDR_MASK;
876 __clear_bit(n, &p->bitmap);
884 n = idr_id & IDR_MASK;
885 __clear_bit(n, &p->bitmap);
887 bitmap = (void *)p->ary[n];
888 if (!test_bit(offset, bitmap->bitmap))
891 /* update bitmap and remove it if empty */
892 __clear_bit(offset, bitmap->bitmap);
893 if (--bitmap->nr_busy == 0) {
894 __set_bit(n, &p->bitmap); /* to please idr_remove() */
895 idr_remove(&ida->idr, idr_id);
896 free_bitmap(ida, bitmap);
903 "ida_remove called for id=%d which is not allocated.\n", id);
905 EXPORT_SYMBOL(ida_remove);
908 * ida_destroy - release all cached layers within an ida tree
911 void ida_destroy(struct ida *ida)
913 idr_destroy(&ida->idr);
914 kfree(ida->free_bitmap);
916 EXPORT_SYMBOL(ida_destroy);
919 * ida_init - initialize ida handle
922 * This function is use to set up the handle (@ida) that you will pass
923 * to the rest of the functions.
925 void ida_init(struct ida *ida)
927 memset(ida, 0, sizeof(struct ida));
931 EXPORT_SYMBOL(ida_init);