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 */
161 return IDR_NEED_TO_GROW;
164 /* If we need to go up one layer, continue the
165 * loop; otherwise, restart from the top.
167 sh = IDR_BITS * (l + 1);
168 if (oid >> sh == id >> sh)
175 id = ((id >> sh) ^ n ^ m) << sh;
177 if ((id >= MAX_ID_BIT) || (id < 0))
178 return IDR_NOMORE_SPACE;
182 * Create the layer below if it is missing.
185 new = get_from_free_list(idp);
189 rcu_assign_pointer(p->ary[m], new);
200 static int idr_get_empty_slot(struct idr *idp, int starting_id,
201 struct idr_layer **pa)
203 struct idr_layer *p, *new;
210 layers = idp->layers;
212 if (!(p = get_from_free_list(idp)))
218 * Add a new layer to the top of the tree if the requested
219 * id is larger than the currently allocated space.
221 while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
224 /* special case: if the tree is currently empty,
225 * then we grow the tree by moving the top node
231 if (!(new = get_from_free_list(idp))) {
233 * The allocation failed. If we built part of
234 * the structure tear it down.
236 spin_lock_irqsave(&idp->lock, flags);
237 for (new = p; p && p != idp->top; new = p) {
240 new->bitmap = new->count = 0;
241 __move_to_free_list(idp, new);
243 spin_unlock_irqrestore(&idp->lock, flags);
248 new->layer = layers-1;
249 if (p->bitmap == IDR_FULL)
250 __set_bit(0, &new->bitmap);
253 rcu_assign_pointer(idp->top, p);
254 idp->layers = layers;
255 v = sub_alloc(idp, &id, pa);
256 if (v == IDR_NEED_TO_GROW)
261 static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
263 struct idr_layer *pa[MAX_LEVEL];
266 id = idr_get_empty_slot(idp, starting_id, pa);
269 * Successfully found an empty slot. Install the user
270 * pointer and mark the slot full.
272 rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
273 (struct idr_layer *)ptr);
275 idr_mark_full(pa, id);
282 * idr_get_new_above - allocate new idr entry above or equal to a start id
284 * @ptr: pointer you want associated with the ide
285 * @start_id: id to start search at
286 * @id: pointer to the allocated handle
288 * This is the allocate id function. It should be called with any
291 * If memory is required, it will return -EAGAIN, you should unlock
292 * and go back to the idr_pre_get() call. If the idr is full, it will
295 * @id returns a value in the range @starting_id ... 0x7fffffff
297 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
301 rv = idr_get_new_above_int(idp, ptr, starting_id);
303 * This is a cheap hack until the IDR code can be fixed to
304 * return proper error values.
307 return _idr_rc_to_errno(rv);
311 EXPORT_SYMBOL(idr_get_new_above);
314 * idr_get_new - allocate new idr entry
316 * @ptr: pointer you want associated with the ide
317 * @id: pointer to the allocated handle
319 * This is the allocate id function. It should be called with any
322 * If memory is required, it will return -EAGAIN, you should unlock
323 * and go back to the idr_pre_get() call. If the idr is full, it will
326 * @id returns a value in the range 0 ... 0x7fffffff
328 int idr_get_new(struct idr *idp, void *ptr, int *id)
332 rv = idr_get_new_above_int(idp, ptr, 0);
334 * This is a cheap hack until the IDR code can be fixed to
335 * return proper error values.
338 return _idr_rc_to_errno(rv);
342 EXPORT_SYMBOL(idr_get_new);
344 static void idr_remove_warning(int id)
347 "idr_remove called for id=%d which is not allocated.\n", id);
351 static void sub_remove(struct idr *idp, int shift, int id)
353 struct idr_layer *p = idp->top;
354 struct idr_layer **pa[MAX_LEVEL];
355 struct idr_layer ***paa = &pa[0];
356 struct idr_layer *to_free;
362 while ((shift > 0) && p) {
363 n = (id >> shift) & IDR_MASK;
364 __clear_bit(n, &p->bitmap);
370 if (likely(p != NULL && test_bit(n, &p->bitmap))){
371 __clear_bit(n, &p->bitmap);
372 rcu_assign_pointer(p->ary[n], NULL);
374 while(*paa && ! --((**paa)->count)){
385 idr_remove_warning(id);
389 * idr_remove - remove the given id and free it's slot
393 void idr_remove(struct idr *idp, int id)
396 struct idr_layer *to_free;
398 /* Mask off upper bits we don't use for the search. */
401 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
402 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
405 * Single child at leftmost slot: we can shrink the tree.
406 * This level is not needed anymore since when layers are
407 * inserted, they are inserted at the top of the existing
411 p = idp->top->ary[0];
412 rcu_assign_pointer(idp->top, p);
414 to_free->bitmap = to_free->count = 0;
417 while (idp->id_free_cnt >= IDR_FREE_MAX) {
418 p = get_from_free_list(idp);
420 * Note: we don't call the rcu callback here, since the only
421 * layers that fall into the freelist are those that have been
424 kmem_cache_free(idr_layer_cache, p);
428 EXPORT_SYMBOL(idr_remove);
431 * idr_remove_all - remove all ids from the given idr tree
434 * idr_destroy() only frees up unused, cached idp_layers, but this
435 * function will remove all id mappings and leave all idp_layers
438 * A typical clean-up sequence for objects stored in an idr tree, will
439 * use idr_for_each() to free all objects, if necessay, then
440 * idr_remove_all() to remove all ids, and idr_destroy() to free
441 * up the cached idr_layers.
443 void idr_remove_all(struct idr *idp)
447 struct idr_layer *pa[MAX_LEVEL];
448 struct idr_layer **paa = &pa[0];
450 n = idp->layers * IDR_BITS;
452 rcu_assign_pointer(idp->top, NULL);
457 while (n > IDR_BITS && p) {
460 p = p->ary[(id >> n) & IDR_MASK];
464 while (n < fls(id)) {
473 EXPORT_SYMBOL(idr_remove_all);
476 * idr_destroy - release all cached layers within an idr tree
479 void idr_destroy(struct idr *idp)
481 while (idp->id_free_cnt) {
482 struct idr_layer *p = get_from_free_list(idp);
483 kmem_cache_free(idr_layer_cache, p);
486 EXPORT_SYMBOL(idr_destroy);
489 * idr_find - return pointer for given id
493 * Return the pointer given the id it has been registered with. A %NULL
494 * return indicates that @id is not valid or you passed %NULL in
497 * This function can be called under rcu_read_lock(), given that the leaf
498 * pointers lifetimes are correctly managed.
500 void *idr_find(struct idr *idp, int id)
505 p = rcu_dereference(idp->top);
508 n = (p->layer+1) * IDR_BITS;
510 /* Mask off upper bits we don't use for the search. */
519 BUG_ON(n != p->layer*IDR_BITS);
520 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
524 EXPORT_SYMBOL(idr_find);
527 * idr_for_each - iterate through all stored pointers
529 * @fn: function to be called for each pointer
530 * @data: data passed back to callback function
532 * Iterate over the pointers registered with the given idr. The
533 * callback function will be called for each pointer currently
534 * registered, passing the id, the pointer and the data pointer passed
535 * to this function. It is not safe to modify the idr tree while in
536 * the callback, so functions such as idr_get_new and idr_remove are
539 * We check the return of @fn each time. If it returns anything other
540 * than 0, we break out and return that value.
542 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
544 int idr_for_each(struct idr *idp,
545 int (*fn)(int id, void *p, void *data), void *data)
547 int n, id, max, error = 0;
549 struct idr_layer *pa[MAX_LEVEL];
550 struct idr_layer **paa = &pa[0];
552 n = idp->layers * IDR_BITS;
553 p = rcu_dereference(idp->top);
561 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
565 error = fn(id, (void *)p, data);
571 while (n < fls(id)) {
579 EXPORT_SYMBOL(idr_for_each);
582 * idr_get_next - lookup next object of id to given id.
584 * @id: pointer to lookup key
586 * Returns pointer to registered object with id, which is next number to
590 void *idr_get_next(struct idr *idp, int *nextidp)
592 struct idr_layer *p, *pa[MAX_LEVEL];
593 struct idr_layer **paa = &pa[0];
598 n = idp->layers * IDR_BITS;
600 p = rcu_dereference(idp->top);
608 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
617 while (n < fls(id)) {
628 * idr_replace - replace pointer for given id
630 * @ptr: pointer you want associated with the id
633 * Replace the pointer registered with an id and return the old value.
634 * A -ENOENT return indicates that @id was not found.
635 * A -EINVAL return indicates that @id was not within valid constraints.
637 * The caller must serialize with writers.
639 void *idr_replace(struct idr *idp, void *ptr, int id)
642 struct idr_layer *p, *old_p;
646 return ERR_PTR(-EINVAL);
648 n = (p->layer+1) * IDR_BITS;
653 return ERR_PTR(-EINVAL);
656 while ((n > 0) && p) {
657 p = p->ary[(id >> n) & IDR_MASK];
662 if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
663 return ERR_PTR(-ENOENT);
666 rcu_assign_pointer(p->ary[n], ptr);
670 EXPORT_SYMBOL(idr_replace);
672 void __init idr_init_cache(void)
674 idr_layer_cache = kmem_cache_create("idr_layer_cache",
675 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
679 * idr_init - initialize idr handle
682 * This function is use to set up the handle (@idp) that you will pass
683 * to the rest of the functions.
685 void idr_init(struct idr *idp)
687 memset(idp, 0, sizeof(struct idr));
688 spin_lock_init(&idp->lock);
690 EXPORT_SYMBOL(idr_init);
694 * IDA - IDR based ID allocator
696 * this is id allocator without id -> pointer translation. Memory
697 * usage is much lower than full blown idr because each id only
698 * occupies a bit. ida uses a custom leaf node which contains
699 * IDA_BITMAP_BITS slots.
701 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
704 static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
708 if (!ida->free_bitmap) {
709 spin_lock_irqsave(&ida->idr.lock, flags);
710 if (!ida->free_bitmap) {
711 ida->free_bitmap = bitmap;
714 spin_unlock_irqrestore(&ida->idr.lock, flags);
721 * ida_pre_get - reserve resources for ida allocation
723 * @gfp_mask: memory allocation flag
725 * This function should be called prior to locking and calling the
726 * following function. It preallocates enough memory to satisfy the
727 * worst possible allocation.
729 * If the system is REALLY out of memory this function returns 0,
732 int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
734 /* allocate idr_layers */
735 if (!idr_pre_get(&ida->idr, gfp_mask))
738 /* allocate free_bitmap */
739 if (!ida->free_bitmap) {
740 struct ida_bitmap *bitmap;
742 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
746 free_bitmap(ida, bitmap);
751 EXPORT_SYMBOL(ida_pre_get);
754 * ida_get_new_above - allocate new ID above or equal to a start id
756 * @staring_id: id to start search at
757 * @p_id: pointer to the allocated handle
759 * Allocate new ID above or equal to @ida. It should be called with
760 * any required locks.
762 * If memory is required, it will return -EAGAIN, you should unlock
763 * and go back to the ida_pre_get() call. If the ida is full, it will
766 * @p_id returns a value in the range @starting_id ... 0x7fffffff.
768 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
770 struct idr_layer *pa[MAX_LEVEL];
771 struct ida_bitmap *bitmap;
773 int idr_id = starting_id / IDA_BITMAP_BITS;
774 int offset = starting_id % IDA_BITMAP_BITS;
778 /* get vacant slot */
779 t = idr_get_empty_slot(&ida->idr, idr_id, pa);
781 return _idr_rc_to_errno(t);
783 if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
790 /* if bitmap isn't there, create a new one */
791 bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
793 spin_lock_irqsave(&ida->idr.lock, flags);
794 bitmap = ida->free_bitmap;
795 ida->free_bitmap = NULL;
796 spin_unlock_irqrestore(&ida->idr.lock, flags);
801 memset(bitmap, 0, sizeof(struct ida_bitmap));
802 rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
807 /* lookup for empty slot */
808 t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
809 if (t == IDA_BITMAP_BITS) {
810 /* no empty slot after offset, continue to the next chunk */
816 id = idr_id * IDA_BITMAP_BITS + t;
817 if (id >= MAX_ID_BIT)
820 __set_bit(t, bitmap->bitmap);
821 if (++bitmap->nr_busy == IDA_BITMAP_BITS)
822 idr_mark_full(pa, idr_id);
826 /* Each leaf node can handle nearly a thousand slots and the
827 * whole idea of ida is to have small memory foot print.
828 * Throw away extra resources one by one after each successful
831 if (ida->idr.id_free_cnt || ida->free_bitmap) {
832 struct idr_layer *p = get_from_free_list(&ida->idr);
834 kmem_cache_free(idr_layer_cache, p);
839 EXPORT_SYMBOL(ida_get_new_above);
842 * ida_get_new - allocate new ID
844 * @p_id: pointer to the allocated handle
846 * Allocate new ID. It should be called with any required locks.
848 * If memory is required, it will return -EAGAIN, you should unlock
849 * and go back to the idr_pre_get() call. If the idr is full, it will
852 * @id returns a value in the range 0 ... 0x7fffffff.
854 int ida_get_new(struct ida *ida, int *p_id)
856 return ida_get_new_above(ida, 0, p_id);
858 EXPORT_SYMBOL(ida_get_new);
861 * ida_remove - remove the given ID
865 void ida_remove(struct ida *ida, int id)
867 struct idr_layer *p = ida->idr.top;
868 int shift = (ida->idr.layers - 1) * IDR_BITS;
869 int idr_id = id / IDA_BITMAP_BITS;
870 int offset = id % IDA_BITMAP_BITS;
872 struct ida_bitmap *bitmap;
874 /* clear full bits while looking up the leaf idr_layer */
875 while ((shift > 0) && p) {
876 n = (idr_id >> shift) & IDR_MASK;
877 __clear_bit(n, &p->bitmap);
885 n = idr_id & IDR_MASK;
886 __clear_bit(n, &p->bitmap);
888 bitmap = (void *)p->ary[n];
889 if (!test_bit(offset, bitmap->bitmap))
892 /* update bitmap and remove it if empty */
893 __clear_bit(offset, bitmap->bitmap);
894 if (--bitmap->nr_busy == 0) {
895 __set_bit(n, &p->bitmap); /* to please idr_remove() */
896 idr_remove(&ida->idr, idr_id);
897 free_bitmap(ida, bitmap);
904 "ida_remove called for id=%d which is not allocated.\n", id);
906 EXPORT_SYMBOL(ida_remove);
909 * ida_destroy - release all cached layers within an ida tree
912 void ida_destroy(struct ida *ida)
914 idr_destroy(&ida->idr);
915 kfree(ida->free_bitmap);
917 EXPORT_SYMBOL(ida_destroy);
920 * ida_init - initialize ida handle
923 * This function is use to set up the handle (@ida) that you will pass
924 * to the rest of the functions.
926 void ida_init(struct ida *ida)
928 memset(ida, 0, sizeof(struct ida));
932 EXPORT_SYMBOL(ida_init);