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 MAX_IDR_FREE) 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/export.h>
34 #include <linux/err.h>
35 #include <linux/string.h>
36 #include <linux/idr.h>
37 #include <linux/spinlock.h>
39 static struct kmem_cache *idr_layer_cache;
40 static DEFINE_SPINLOCK(simple_ida_lock);
42 static struct idr_layer *get_from_free_list(struct idr *idp)
47 spin_lock_irqsave(&idp->lock, flags);
48 if ((p = idp->id_free)) {
49 idp->id_free = p->ary[0];
53 spin_unlock_irqrestore(&idp->lock, flags);
57 static void idr_layer_rcu_free(struct rcu_head *head)
59 struct idr_layer *layer;
61 layer = container_of(head, struct idr_layer, rcu_head);
62 kmem_cache_free(idr_layer_cache, layer);
65 static inline void free_layer(struct idr_layer *p)
67 call_rcu(&p->rcu_head, idr_layer_rcu_free);
70 /* only called when idp->lock is held */
71 static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
73 p->ary[0] = idp->id_free;
78 static void move_to_free_list(struct idr *idp, struct idr_layer *p)
83 * Depends on the return element being zeroed.
85 spin_lock_irqsave(&idp->lock, flags);
86 __move_to_free_list(idp, p);
87 spin_unlock_irqrestore(&idp->lock, flags);
90 static void idr_mark_full(struct idr_layer **pa, int id)
92 struct idr_layer *p = pa[0];
95 __set_bit(id & IDR_MASK, &p->bitmap);
97 * If this layer is full mark the bit in the layer above to
98 * show that this part of the radix tree is full. This may
99 * complete the layer above and require walking up the radix
102 while (p->bitmap == IDR_FULL) {
106 __set_bit((id & IDR_MASK), &p->bitmap);
111 * idr_pre_get - reserve resources for idr allocation
113 * @gfp_mask: memory allocation flags
115 * This function should be called prior to calling the idr_get_new* functions.
116 * It preallocates enough memory to satisfy the worst possible allocation. The
117 * caller should pass in GFP_KERNEL if possible. This of course requires that
118 * no spinning locks be held.
120 * If the system is REALLY out of memory this function returns %0,
123 int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
125 while (idp->id_free_cnt < MAX_IDR_FREE) {
126 struct idr_layer *new;
127 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
130 move_to_free_list(idp, new);
134 EXPORT_SYMBOL(idr_pre_get);
137 * sub_alloc - try to allocate an id without growing the tree depth
139 * @starting_id: id to start search at
140 * @id: pointer to the allocated handle
141 * @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer
143 * Allocate an id in range [@starting_id, INT_MAX] from @idp without
144 * growing its depth. Returns
146 * the allocated id >= 0 if successful,
147 * -EAGAIN if the tree needs to grow for allocation to succeed,
148 * -ENOSPC if the id space is exhausted,
149 * -ENOMEM if more idr_layers need to be allocated.
151 static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
154 struct idr_layer *p, *new;
165 * We run around this while until we reach the leaf node...
167 n = (id >> (IDR_BITS*l)) & IDR_MASK;
169 m = find_next_bit(&bm, IDR_SIZE, n);
171 /* no space available go back to previous layer. */
174 id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
176 /* if already at the top layer, we need to grow */
177 if (id >= 1 << (idp->layers * IDR_BITS)) {
184 /* If we need to go up one layer, continue the
185 * loop; otherwise, restart from the top.
187 sh = IDR_BITS * (l + 1);
188 if (oid >> sh == id >> sh)
195 id = ((id >> sh) ^ n ^ m) << sh;
197 if ((id >= MAX_IDR_BIT) || (id < 0))
202 * Create the layer below if it is missing.
205 new = get_from_free_list(idp);
209 rcu_assign_pointer(p->ary[m], new);
220 static int idr_get_empty_slot(struct idr *idp, int starting_id,
221 struct idr_layer **pa)
223 struct idr_layer *p, *new;
230 layers = idp->layers;
232 if (!(p = get_from_free_list(idp)))
238 * Add a new layer to the top of the tree if the requested
239 * id is larger than the currently allocated space.
241 while ((layers < (MAX_IDR_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
244 /* special case: if the tree is currently empty,
245 * then we grow the tree by moving the top node
251 if (!(new = get_from_free_list(idp))) {
253 * The allocation failed. If we built part of
254 * the structure tear it down.
256 spin_lock_irqsave(&idp->lock, flags);
257 for (new = p; p && p != idp->top; new = p) {
260 new->bitmap = new->count = 0;
261 __move_to_free_list(idp, new);
263 spin_unlock_irqrestore(&idp->lock, flags);
268 new->layer = layers-1;
269 if (p->bitmap == IDR_FULL)
270 __set_bit(0, &new->bitmap);
273 rcu_assign_pointer(idp->top, p);
274 idp->layers = layers;
275 v = sub_alloc(idp, &id, pa);
281 static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
283 struct idr_layer *pa[MAX_IDR_LEVEL];
286 id = idr_get_empty_slot(idp, starting_id, pa);
289 * Successfully found an empty slot. Install the user
290 * pointer and mark the slot full.
292 rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
293 (struct idr_layer *)ptr);
295 idr_mark_full(pa, id);
302 * idr_get_new_above - allocate new idr entry above or equal to a start id
304 * @ptr: pointer you want associated with the id
305 * @starting_id: id to start search at
306 * @id: pointer to the allocated handle
308 * This is the allocate id function. It should be called with any
311 * If allocation from IDR's private freelist fails, idr_get_new_above() will
312 * return %-EAGAIN. The caller should retry the idr_pre_get() call to refill
313 * IDR's preallocation and then retry the idr_get_new_above() call.
315 * If the idr is full idr_get_new_above() will return %-ENOSPC.
317 * @id returns a value in the range @starting_id ... %0x7fffffff
319 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
323 rv = idr_get_new_above_int(idp, ptr, starting_id);
325 return rv == -ENOMEM ? -EAGAIN : rv;
329 EXPORT_SYMBOL(idr_get_new_above);
331 static void idr_remove_warning(int id)
334 "idr_remove called for id=%d which is not allocated.\n", id);
338 static void sub_remove(struct idr *idp, int shift, int id)
340 struct idr_layer *p = idp->top;
341 struct idr_layer **pa[MAX_IDR_LEVEL];
342 struct idr_layer ***paa = &pa[0];
343 struct idr_layer *to_free;
349 while ((shift > 0) && p) {
350 n = (id >> shift) & IDR_MASK;
351 __clear_bit(n, &p->bitmap);
357 if (likely(p != NULL && test_bit(n, &p->bitmap))){
358 __clear_bit(n, &p->bitmap);
359 rcu_assign_pointer(p->ary[n], NULL);
361 while(*paa && ! --((**paa)->count)){
372 idr_remove_warning(id);
376 * idr_remove - remove the given id and free its slot
380 void idr_remove(struct idr *idp, int id)
383 struct idr_layer *to_free;
385 /* Mask off upper bits we don't use for the search. */
388 sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
389 if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
392 * Single child at leftmost slot: we can shrink the tree.
393 * This level is not needed anymore since when layers are
394 * inserted, they are inserted at the top of the existing
398 p = idp->top->ary[0];
399 rcu_assign_pointer(idp->top, p);
401 to_free->bitmap = to_free->count = 0;
404 while (idp->id_free_cnt >= MAX_IDR_FREE) {
405 p = get_from_free_list(idp);
407 * Note: we don't call the rcu callback here, since the only
408 * layers that fall into the freelist are those that have been
411 kmem_cache_free(idr_layer_cache, p);
415 EXPORT_SYMBOL(idr_remove);
417 void __idr_remove_all(struct idr *idp)
422 struct idr_layer *pa[MAX_IDR_LEVEL];
423 struct idr_layer **paa = &pa[0];
425 n = idp->layers * IDR_BITS;
427 rcu_assign_pointer(idp->top, NULL);
432 while (n > IDR_BITS && p) {
435 p = p->ary[(id >> n) & IDR_MASK];
440 /* Get the highest bit that the above add changed from 0->1. */
441 while (n < fls(id ^ bt_mask)) {
450 EXPORT_SYMBOL(__idr_remove_all);
453 * idr_destroy - release all cached layers within an idr tree
456 * Free all id mappings and all idp_layers. After this function, @idp is
457 * completely unused and can be freed / recycled. The caller is
458 * responsible for ensuring that no one else accesses @idp during or after
461 * A typical clean-up sequence for objects stored in an idr tree will use
462 * idr_for_each() to free all objects, if necessay, then idr_destroy() to
463 * free up the id mappings and cached idr_layers.
465 void idr_destroy(struct idr *idp)
467 __idr_remove_all(idp);
469 while (idp->id_free_cnt) {
470 struct idr_layer *p = get_from_free_list(idp);
471 kmem_cache_free(idr_layer_cache, p);
474 EXPORT_SYMBOL(idr_destroy);
477 * idr_find - return pointer for given id
481 * Return the pointer given the id it has been registered with. A %NULL
482 * return indicates that @id is not valid or you passed %NULL in
485 * This function can be called under rcu_read_lock(), given that the leaf
486 * pointers lifetimes are correctly managed.
488 void *idr_find(struct idr *idp, int id)
493 p = rcu_dereference_raw(idp->top);
496 n = (p->layer+1) * IDR_BITS;
498 /* Mask off upper bits we don't use for the search. */
507 BUG_ON(n != p->layer*IDR_BITS);
508 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
512 EXPORT_SYMBOL(idr_find);
515 * idr_for_each - iterate through all stored pointers
517 * @fn: function to be called for each pointer
518 * @data: data passed back to callback function
520 * Iterate over the pointers registered with the given idr. The
521 * callback function will be called for each pointer currently
522 * registered, passing the id, the pointer and the data pointer passed
523 * to this function. It is not safe to modify the idr tree while in
524 * the callback, so functions such as idr_get_new and idr_remove are
527 * We check the return of @fn each time. If it returns anything other
528 * than %0, we break out and return that value.
530 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
532 int idr_for_each(struct idr *idp,
533 int (*fn)(int id, void *p, void *data), void *data)
535 int n, id, max, error = 0;
537 struct idr_layer *pa[MAX_IDR_LEVEL];
538 struct idr_layer **paa = &pa[0];
540 n = idp->layers * IDR_BITS;
541 p = rcu_dereference_raw(idp->top);
549 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
553 error = fn(id, (void *)p, data);
559 while (n < fls(id)) {
567 EXPORT_SYMBOL(idr_for_each);
570 * idr_get_next - lookup next object of id to given id.
572 * @nextidp: pointer to lookup key
574 * Returns pointer to registered object with id, which is next number to
575 * given id. After being looked up, *@nextidp will be updated for the next
578 * This function can be called under rcu_read_lock(), given that the leaf
579 * pointers lifetimes are correctly managed.
581 void *idr_get_next(struct idr *idp, int *nextidp)
583 struct idr_layer *p, *pa[MAX_IDR_LEVEL];
584 struct idr_layer **paa = &pa[0];
589 p = rcu_dereference_raw(idp->top);
592 n = (p->layer + 1) * IDR_BITS;
599 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
608 * Proceed to the next layer at the current level. Unlike
609 * idr_for_each(), @id isn't guaranteed to be aligned to
610 * layer boundary at this point and adding 1 << n may
611 * incorrectly skip IDs. Make sure we jump to the
612 * beginning of the next layer using round_up().
614 id = round_up(id + 1, 1 << n);
615 while (n < fls(id)) {
622 EXPORT_SYMBOL(idr_get_next);
626 * idr_replace - replace pointer for given id
628 * @ptr: pointer you want associated with the id
631 * Replace the pointer registered with an id and return the old value.
632 * A %-ENOENT return indicates that @id was not found.
633 * A %-EINVAL return indicates that @id was not within valid constraints.
635 * The caller must serialize with writers.
637 void *idr_replace(struct idr *idp, void *ptr, int id)
640 struct idr_layer *p, *old_p;
644 return ERR_PTR(-EINVAL);
646 n = (p->layer+1) * IDR_BITS;
651 return ERR_PTR(-EINVAL);
654 while ((n > 0) && p) {
655 p = p->ary[(id >> n) & IDR_MASK];
660 if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
661 return ERR_PTR(-ENOENT);
664 rcu_assign_pointer(p->ary[n], ptr);
668 EXPORT_SYMBOL(idr_replace);
670 void __init idr_init_cache(void)
672 idr_layer_cache = kmem_cache_create("idr_layer_cache",
673 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
677 * idr_init - initialize idr handle
680 * This function is use to set up the handle (@idp) that you will pass
681 * to the rest of the functions.
683 void idr_init(struct idr *idp)
685 memset(idp, 0, sizeof(struct idr));
686 spin_lock_init(&idp->lock);
688 EXPORT_SYMBOL(idr_init);
692 * DOC: IDA description
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 * @starting_id: id to start search at
756 * @p_id: pointer to the allocated handle
758 * Allocate new ID above or equal to @starting_id. It should be called
759 * with 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_IDR_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 t == -ENOMEM ? -EAGAIN : t;
782 if (t * IDA_BITMAP_BITS >= MAX_IDR_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_IDR_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_remove - remove the given ID
845 void ida_remove(struct ida *ida, int id)
847 struct idr_layer *p = ida->idr.top;
848 int shift = (ida->idr.layers - 1) * IDR_BITS;
849 int idr_id = id / IDA_BITMAP_BITS;
850 int offset = id % IDA_BITMAP_BITS;
852 struct ida_bitmap *bitmap;
854 /* clear full bits while looking up the leaf idr_layer */
855 while ((shift > 0) && p) {
856 n = (idr_id >> shift) & IDR_MASK;
857 __clear_bit(n, &p->bitmap);
865 n = idr_id & IDR_MASK;
866 __clear_bit(n, &p->bitmap);
868 bitmap = (void *)p->ary[n];
869 if (!test_bit(offset, bitmap->bitmap))
872 /* update bitmap and remove it if empty */
873 __clear_bit(offset, bitmap->bitmap);
874 if (--bitmap->nr_busy == 0) {
875 __set_bit(n, &p->bitmap); /* to please idr_remove() */
876 idr_remove(&ida->idr, idr_id);
877 free_bitmap(ida, bitmap);
884 "ida_remove called for id=%d which is not allocated.\n", id);
886 EXPORT_SYMBOL(ida_remove);
889 * ida_destroy - release all cached layers within an ida tree
892 void ida_destroy(struct ida *ida)
894 idr_destroy(&ida->idr);
895 kfree(ida->free_bitmap);
897 EXPORT_SYMBOL(ida_destroy);
900 * ida_simple_get - get a new id.
901 * @ida: the (initialized) ida.
902 * @start: the minimum id (inclusive, < 0x8000000)
903 * @end: the maximum id (exclusive, < 0x8000000 or 0)
904 * @gfp_mask: memory allocation flags
906 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
907 * On memory allocation failure, returns -ENOMEM.
909 * Use ida_simple_remove() to get rid of an id.
911 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
918 BUG_ON((int)start < 0);
919 BUG_ON((int)end < 0);
929 if (!ida_pre_get(ida, gfp_mask))
932 spin_lock_irqsave(&simple_ida_lock, flags);
933 ret = ida_get_new_above(ida, start, &id);
942 spin_unlock_irqrestore(&simple_ida_lock, flags);
944 if (unlikely(ret == -EAGAIN))
949 EXPORT_SYMBOL(ida_simple_get);
952 * ida_simple_remove - remove an allocated id.
953 * @ida: the (initialized) ida.
954 * @id: the id returned by ida_simple_get.
956 void ida_simple_remove(struct ida *ida, unsigned int id)
961 spin_lock_irqsave(&simple_ida_lock, flags);
963 spin_unlock_irqrestore(&simple_ida_lock, flags);
965 EXPORT_SYMBOL(ida_simple_remove);
968 * ida_init - initialize ida handle
971 * This function is use to set up the handle (@ida) that you will pass
972 * to the rest of the functions.
974 void ida_init(struct ida *ida)
976 memset(ida, 0, sizeof(struct ida));
980 EXPORT_SYMBOL(ida_init);