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)
66 call_rcu(&p->rcu_head, idr_layer_rcu_free);
68 idr_layer_rcu_free(&p->rcu_head);
72 /* only called when idp->lock is held */
73 static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
75 p->ary[0] = idp->id_free;
80 static void move_to_free_list(struct idr *idp, struct idr_layer *p)
85 * Depends on the return element being zeroed.
87 spin_lock_irqsave(&idp->lock, flags);
88 __move_to_free_list(idp, p);
89 spin_unlock_irqrestore(&idp->lock, flags);
92 static void idr_mark_full(struct idr_layer **pa, int id)
94 struct idr_layer *p = pa[0];
97 __set_bit(id & IDR_MASK, &p->bitmap);
99 * If this layer is full mark the bit in the layer above to
100 * show that this part of the radix tree is full. This may
101 * complete the layer above and require walking up the radix
104 while (p->bitmap == IDR_FULL) {
108 __set_bit((id & IDR_MASK), &p->bitmap);
113 * idr_pre_get - reserver resources for idr allocation
115 * @gfp_mask: memory allocation flags
117 * This function should be called prior to locking and calling the
118 * idr_get_new* functions. It preallocates enough memory to satisfy
119 * the worst possible allocation.
121 * If the system is REALLY out of memory this function returns 0,
124 int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
126 while (idp->id_free_cnt < IDR_FREE_MAX) {
127 struct idr_layer *new;
128 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
131 move_to_free_list(idp, new);
135 EXPORT_SYMBOL(idr_pre_get);
137 static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
140 struct idr_layer *p, *new;
151 * We run around this while until we reach the leaf node...
153 n = (id >> (IDR_BITS*l)) & IDR_MASK;
155 m = find_next_bit(&bm, IDR_SIZE, n);
157 /* no space available go back to previous layer. */
160 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
162 /* if already at the top layer, we need to grow */
165 return IDR_NEED_TO_GROW;
168 /* If we need to go up one layer, continue the
169 * loop; otherwise, restart from the top.
171 sh = IDR_BITS * (l + 1);
172 if (oid >> sh == id >> sh)
179 id = ((id >> sh) ^ n ^ m) << sh;
181 if ((id >= MAX_ID_BIT) || (id < 0))
182 return IDR_NOMORE_SPACE;
186 * Create the layer below if it is missing.
189 new = get_from_free_list(idp);
193 rcu_assign_pointer(p->ary[m], new);
204 static int idr_get_empty_slot(struct idr *idp, int starting_id,
205 struct idr_layer **pa)
207 struct idr_layer *p, *new;
214 layers = idp->layers;
216 if (!(p = get_from_free_list(idp)))
222 * Add a new layer to the top of the tree if the requested
223 * id is larger than the currently allocated space.
225 while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
228 /* special case: if the tree is currently empty,
229 * then we grow the tree by moving the top node
235 if (!(new = get_from_free_list(idp))) {
237 * The allocation failed. If we built part of
238 * the structure tear it down.
240 spin_lock_irqsave(&idp->lock, flags);
241 for (new = p; p && p != idp->top; new = p) {
244 new->bitmap = new->count = 0;
245 __move_to_free_list(idp, new);
247 spin_unlock_irqrestore(&idp->lock, flags);
252 new->layer = layers-1;
253 if (p->bitmap == IDR_FULL)
254 __set_bit(0, &new->bitmap);
257 rcu_assign_pointer(idp->top, p);
258 idp->layers = layers;
259 v = sub_alloc(idp, &id, pa);
260 if (v == IDR_NEED_TO_GROW)
265 static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
267 struct idr_layer *pa[MAX_LEVEL];
270 id = idr_get_empty_slot(idp, starting_id, pa);
273 * Successfully found an empty slot. Install the user
274 * pointer and mark the slot full.
276 rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
277 (struct idr_layer *)ptr);
279 idr_mark_full(pa, id);
286 * idr_get_new_above - allocate new idr entry above or equal to a start id
288 * @ptr: pointer you want associated with the ide
289 * @start_id: id to start search at
290 * @id: pointer to the allocated handle
292 * This is the allocate id function. It should be called with any
295 * If memory is required, it will return -EAGAIN, you should unlock
296 * and go back to the idr_pre_get() call. If the idr is full, it will
299 * @id returns a value in the range @starting_id ... 0x7fffffff
301 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
305 rv = idr_get_new_above_int(idp, ptr, starting_id);
307 * This is a cheap hack until the IDR code can be fixed to
308 * return proper error values.
311 return _idr_rc_to_errno(rv);
315 EXPORT_SYMBOL(idr_get_new_above);
318 * idr_get_new - allocate new idr entry
320 * @ptr: pointer you want associated with the ide
321 * @id: pointer to the allocated handle
323 * This is the allocate id function. It should be called with any
326 * If memory is required, it will return -EAGAIN, you should unlock
327 * and go back to the idr_pre_get() call. If the idr is full, it will
330 * @id returns a value in the range 0 ... 0x7fffffff
332 int idr_get_new(struct idr *idp, void *ptr, int *id)
336 rv = idr_get_new_above_int(idp, ptr, 0);
338 * This is a cheap hack until the IDR code can be fixed to
339 * return proper error values.
342 return _idr_rc_to_errno(rv);
346 EXPORT_SYMBOL(idr_get_new);
348 static void idr_remove_warning(int id)
351 "idr_remove called for id=%d which is not allocated.\n", id);
355 static void sub_remove(struct idr *idp, int shift, int id)
357 struct idr_layer *p = idp->top;
358 struct idr_layer **pa[MAX_LEVEL];
359 struct idr_layer ***paa = &pa[0];
360 struct idr_layer *to_free;
366 while ((shift > 0) && p) {
367 n = (id >> shift) & IDR_MASK;
368 __clear_bit(n, &p->bitmap);
374 if (likely(p != NULL && test_bit(n, &p->bitmap))){
375 __clear_bit(n, &p->bitmap);
376 rcu_assign_pointer(p->ary[n], NULL);
378 while(*paa && ! --((**paa)->count)){
389 idr_remove_warning(id);
393 * idr_remove - remove the given id and free it's slot
397 void idr_remove(struct idr *idp, int id)
400 struct idr_layer *to_free;
402 /* Mask off upper bits we don't use for the search. */
405 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
406 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
409 * Single child at leftmost slot: we can shrink the tree.
410 * This level is not needed anymore since when layers are
411 * inserted, they are inserted at the top of the existing
415 p = idp->top->ary[0];
416 rcu_assign_pointer(idp->top, p);
418 to_free->bitmap = to_free->count = 0;
421 while (idp->id_free_cnt >= IDR_FREE_MAX) {
422 p = get_from_free_list(idp);
424 * Note: we don't call the rcu callback here, since the only
425 * layers that fall into the freelist are those that have been
428 kmem_cache_free(idr_layer_cache, p);
432 EXPORT_SYMBOL(idr_remove);
435 * idr_remove_all - remove all ids from the given idr tree
438 * idr_destroy() only frees up unused, cached idp_layers, but this
439 * function will remove all id mappings and leave all idp_layers
442 * A typical clean-up sequence for objects stored in an idr tree, will
443 * use idr_for_each() to free all objects, if necessay, then
444 * idr_remove_all() to remove all ids, and idr_destroy() to free
445 * up the cached idr_layers.
447 void idr_remove_all(struct idr *idp)
451 struct idr_layer *pa[MAX_LEVEL];
452 struct idr_layer **paa = &pa[0];
454 n = idp->layers * IDR_BITS;
456 rcu_assign_pointer(idp->top, NULL);
461 while (n > IDR_BITS && p) {
464 p = p->ary[(id >> n) & IDR_MASK];
468 while (n < fls(id)) {
477 EXPORT_SYMBOL(idr_remove_all);
480 * idr_destroy - release all cached layers within an idr tree
483 void idr_destroy(struct idr *idp)
485 while (idp->id_free_cnt) {
486 struct idr_layer *p = get_from_free_list(idp);
487 kmem_cache_free(idr_layer_cache, p);
490 EXPORT_SYMBOL(idr_destroy);
493 * idr_find - return pointer for given id
497 * Return the pointer given the id it has been registered with. A %NULL
498 * return indicates that @id is not valid or you passed %NULL in
501 * This function can be called under rcu_read_lock(), given that the leaf
502 * pointers lifetimes are correctly managed.
504 void *idr_find(struct idr *idp, int id)
509 p = rcu_dereference(idp->top);
512 n = (p->layer+1) * IDR_BITS;
514 /* Mask off upper bits we don't use for the search. */
523 BUG_ON(n != p->layer*IDR_BITS);
524 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
528 EXPORT_SYMBOL(idr_find);
531 * idr_for_each - iterate through all stored pointers
533 * @fn: function to be called for each pointer
534 * @data: data passed back to callback function
536 * Iterate over the pointers registered with the given idr. The
537 * callback function will be called for each pointer currently
538 * registered, passing the id, the pointer and the data pointer passed
539 * to this function. It is not safe to modify the idr tree while in
540 * the callback, so functions such as idr_get_new and idr_remove are
543 * We check the return of @fn each time. If it returns anything other
544 * than 0, we break out and return that value.
546 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
548 int idr_for_each(struct idr *idp,
549 int (*fn)(int id, void *p, void *data), void *data)
551 int n, id, max, error = 0;
553 struct idr_layer *pa[MAX_LEVEL];
554 struct idr_layer **paa = &pa[0];
556 n = idp->layers * IDR_BITS;
557 p = rcu_dereference(idp->top);
565 p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
569 error = fn(id, (void *)p, data);
575 while (n < fls(id)) {
583 EXPORT_SYMBOL(idr_for_each);
586 * idr_replace - replace pointer for given id
588 * @ptr: pointer you want associated with the id
591 * Replace the pointer registered with an id and return the old value.
592 * A -ENOENT return indicates that @id was not found.
593 * A -EINVAL return indicates that @id was not within valid constraints.
595 * The caller must serialize with writers.
597 void *idr_replace(struct idr *idp, void *ptr, int id)
600 struct idr_layer *p, *old_p;
604 return ERR_PTR(-EINVAL);
606 n = (p->layer+1) * IDR_BITS;
611 return ERR_PTR(-EINVAL);
614 while ((n > 0) && p) {
615 p = p->ary[(id >> n) & IDR_MASK];
620 if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
621 return ERR_PTR(-ENOENT);
624 rcu_assign_pointer(p->ary[n], ptr);
628 EXPORT_SYMBOL(idr_replace);
630 void __init idr_init_cache(void)
632 idr_layer_cache = kmem_cache_create("idr_layer_cache",
633 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
637 * idr_init - initialize idr handle
640 * This function is use to set up the handle (@idp) that you will pass
641 * to the rest of the functions.
643 void idr_init(struct idr *idp)
645 memset(idp, 0, sizeof(struct idr));
646 spin_lock_init(&idp->lock);
648 EXPORT_SYMBOL(idr_init);
652 * IDA - IDR based ID allocator
654 * this is id allocator without id -> pointer translation. Memory
655 * usage is much lower than full blown idr because each id only
656 * occupies a bit. ida uses a custom leaf node which contains
657 * IDA_BITMAP_BITS slots.
659 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
662 static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
666 if (!ida->free_bitmap) {
667 spin_lock_irqsave(&ida->idr.lock, flags);
668 if (!ida->free_bitmap) {
669 ida->free_bitmap = bitmap;
672 spin_unlock_irqrestore(&ida->idr.lock, flags);
679 * ida_pre_get - reserve resources for ida allocation
681 * @gfp_mask: memory allocation flag
683 * This function should be called prior to locking and calling the
684 * following function. It preallocates enough memory to satisfy the
685 * worst possible allocation.
687 * If the system is REALLY out of memory this function returns 0,
690 int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
692 /* allocate idr_layers */
693 if (!idr_pre_get(&ida->idr, gfp_mask))
696 /* allocate free_bitmap */
697 if (!ida->free_bitmap) {
698 struct ida_bitmap *bitmap;
700 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
704 free_bitmap(ida, bitmap);
709 EXPORT_SYMBOL(ida_pre_get);
712 * ida_get_new_above - allocate new ID above or equal to a start id
714 * @staring_id: id to start search at
715 * @p_id: pointer to the allocated handle
717 * Allocate new ID above or equal to @ida. It should be called with
718 * any required locks.
720 * If memory is required, it will return -EAGAIN, you should unlock
721 * and go back to the ida_pre_get() call. If the ida is full, it will
724 * @p_id returns a value in the range @starting_id ... 0x7fffffff.
726 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
728 struct idr_layer *pa[MAX_LEVEL];
729 struct ida_bitmap *bitmap;
731 int idr_id = starting_id / IDA_BITMAP_BITS;
732 int offset = starting_id % IDA_BITMAP_BITS;
736 /* get vacant slot */
737 t = idr_get_empty_slot(&ida->idr, idr_id, pa);
739 return _idr_rc_to_errno(t);
741 if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
748 /* if bitmap isn't there, create a new one */
749 bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
751 spin_lock_irqsave(&ida->idr.lock, flags);
752 bitmap = ida->free_bitmap;
753 ida->free_bitmap = NULL;
754 spin_unlock_irqrestore(&ida->idr.lock, flags);
759 memset(bitmap, 0, sizeof(struct ida_bitmap));
760 rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
765 /* lookup for empty slot */
766 t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
767 if (t == IDA_BITMAP_BITS) {
768 /* no empty slot after offset, continue to the next chunk */
774 id = idr_id * IDA_BITMAP_BITS + t;
775 if (id >= MAX_ID_BIT)
778 __set_bit(t, bitmap->bitmap);
779 if (++bitmap->nr_busy == IDA_BITMAP_BITS)
780 idr_mark_full(pa, idr_id);
784 /* Each leaf node can handle nearly a thousand slots and the
785 * whole idea of ida is to have small memory foot print.
786 * Throw away extra resources one by one after each successful
789 if (ida->idr.id_free_cnt || ida->free_bitmap) {
790 struct idr_layer *p = get_from_free_list(&ida->idr);
792 kmem_cache_free(idr_layer_cache, p);
797 EXPORT_SYMBOL(ida_get_new_above);
800 * ida_get_new - allocate new ID
802 * @p_id: pointer to the allocated handle
804 * Allocate new ID. It should be called with any required locks.
806 * If memory is required, it will return -EAGAIN, you should unlock
807 * and go back to the idr_pre_get() call. If the idr is full, it will
810 * @id returns a value in the range 0 ... 0x7fffffff.
812 int ida_get_new(struct ida *ida, int *p_id)
814 return ida_get_new_above(ida, 0, p_id);
816 EXPORT_SYMBOL(ida_get_new);
819 * ida_remove - remove the given ID
823 void ida_remove(struct ida *ida, int id)
825 struct idr_layer *p = ida->idr.top;
826 int shift = (ida->idr.layers - 1) * IDR_BITS;
827 int idr_id = id / IDA_BITMAP_BITS;
828 int offset = id % IDA_BITMAP_BITS;
830 struct ida_bitmap *bitmap;
832 /* clear full bits while looking up the leaf idr_layer */
833 while ((shift > 0) && p) {
834 n = (idr_id >> shift) & IDR_MASK;
835 __clear_bit(n, &p->bitmap);
843 n = idr_id & IDR_MASK;
844 __clear_bit(n, &p->bitmap);
846 bitmap = (void *)p->ary[n];
847 if (!test_bit(offset, bitmap->bitmap))
850 /* update bitmap and remove it if empty */
851 __clear_bit(offset, bitmap->bitmap);
852 if (--bitmap->nr_busy == 0) {
853 __set_bit(n, &p->bitmap); /* to please idr_remove() */
854 idr_remove(&ida->idr, idr_id);
855 free_bitmap(ida, bitmap);
862 "ida_remove called for id=%d which is not allocated.\n", id);
864 EXPORT_SYMBOL(ida_remove);
867 * ida_destroy - release all cached layers within an ida tree
870 void ida_destroy(struct ida *ida)
872 idr_destroy(&ida->idr);
873 kfree(ida->free_bitmap);
875 EXPORT_SYMBOL(ida_destroy);
878 * ida_init - initialize ida handle
881 * This function is use to set up the handle (@ida) that you will pass
882 * to the rest of the functions.
884 void ida_init(struct ida *ida)
886 memset(ida, 0, sizeof(struct ida));
890 EXPORT_SYMBOL(ida_init);