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
);