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 */
159 if (id
>= 1 << (idp
->layers
* IDR_BITS
)) {
161 return IDR_NEED_TO_GROW
;
166 /* If we need to go up one layer, continue the
167 * loop; otherwise, restart from the top.
169 sh
= IDR_BITS
* (l
+ 1);
170 if (oid
>> sh
== id
>> sh
)
177 id
= ((id
>> sh
) ^ n
^ m
) << sh
;
179 if ((id
>= MAX_ID_BIT
) || (id
< 0))
180 return IDR_NOMORE_SPACE
;
184 * Create the layer below if it is missing.
187 new = get_from_free_list(idp
);
191 rcu_assign_pointer(p
->ary
[m
], new);
202 static int idr_get_empty_slot(struct idr
*idp
, int starting_id
,
203 struct idr_layer
**pa
)
205 struct idr_layer
*p
, *new;
212 layers
= idp
->layers
;
214 if (!(p
= get_from_free_list(idp
)))
220 * Add a new layer to the top of the tree if the requested
221 * id is larger than the currently allocated space.
223 while ((layers
< (MAX_LEVEL
- 1)) && (id
>= (1 << (layers
*IDR_BITS
)))) {
226 /* special case: if the tree is currently empty,
227 * then we grow the tree by moving the top node
233 if (!(new = get_from_free_list(idp
))) {
235 * The allocation failed. If we built part of
236 * the structure tear it down.
238 spin_lock_irqsave(&idp
->lock
, flags
);
239 for (new = p
; p
&& p
!= idp
->top
; new = p
) {
242 new->bitmap
= new->count
= 0;
243 __move_to_free_list(idp
, new);
245 spin_unlock_irqrestore(&idp
->lock
, flags
);
250 new->layer
= layers
-1;
251 if (p
->bitmap
== IDR_FULL
)
252 __set_bit(0, &new->bitmap
);
255 rcu_assign_pointer(idp
->top
, p
);
256 idp
->layers
= layers
;
257 v
= sub_alloc(idp
, &id
, pa
);
258 if (v
== IDR_NEED_TO_GROW
)
263 static int idr_get_new_above_int(struct idr
*idp
, void *ptr
, int starting_id
)
265 struct idr_layer
*pa
[MAX_LEVEL
];
268 id
= idr_get_empty_slot(idp
, starting_id
, pa
);
271 * Successfully found an empty slot. Install the user
272 * pointer and mark the slot full.
274 rcu_assign_pointer(pa
[0]->ary
[id
& IDR_MASK
],
275 (struct idr_layer
*)ptr
);
277 idr_mark_full(pa
, id
);
284 * idr_get_new_above - allocate new idr entry above or equal to a start id
286 * @ptr: pointer you want associated with the id
287 * @start_id: id to start search at
288 * @id: pointer to the allocated handle
290 * This is the allocate id function. It should be called with any
293 * If memory is required, it will return -EAGAIN, you should unlock
294 * and go back to the idr_pre_get() call. If the idr is full, it will
297 * @id returns a value in the range @starting_id ... 0x7fffffff
299 int idr_get_new_above(struct idr
*idp
, void *ptr
, int starting_id
, int *id
)
303 rv
= idr_get_new_above_int(idp
, ptr
, starting_id
);
305 * This is a cheap hack until the IDR code can be fixed to
306 * return proper error values.
309 return _idr_rc_to_errno(rv
);
313 EXPORT_SYMBOL(idr_get_new_above
);
316 * idr_get_new - allocate new idr entry
318 * @ptr: pointer you want associated with the id
319 * @id: pointer to the allocated handle
321 * This is the allocate id function. It should be called with any
324 * If memory is required, it will return -EAGAIN, you should unlock
325 * and go back to the idr_pre_get() call. If the idr is full, it will
328 * @id returns a value in the range 0 ... 0x7fffffff
330 int idr_get_new(struct idr
*idp
, void *ptr
, int *id
)
334 rv
= idr_get_new_above_int(idp
, ptr
, 0);
336 * This is a cheap hack until the IDR code can be fixed to
337 * return proper error values.
340 return _idr_rc_to_errno(rv
);
344 EXPORT_SYMBOL(idr_get_new
);
346 static void idr_remove_warning(int id
)
349 "idr_remove called for id=%d which is not allocated.\n", id
);
353 static void sub_remove(struct idr
*idp
, int shift
, int id
)
355 struct idr_layer
*p
= idp
->top
;
356 struct idr_layer
**pa
[MAX_LEVEL
];
357 struct idr_layer
***paa
= &pa
[0];
358 struct idr_layer
*to_free
;
364 while ((shift
> 0) && p
) {
365 n
= (id
>> shift
) & IDR_MASK
;
366 __clear_bit(n
, &p
->bitmap
);
372 if (likely(p
!= NULL
&& test_bit(n
, &p
->bitmap
))){
373 __clear_bit(n
, &p
->bitmap
);
374 rcu_assign_pointer(p
->ary
[n
], NULL
);
376 while(*paa
&& ! --((**paa
)->count
)){
387 idr_remove_warning(id
);
391 * idr_remove - remove the given id and free it's slot
395 void idr_remove(struct idr
*idp
, int id
)
398 struct idr_layer
*to_free
;
400 /* Mask off upper bits we don't use for the search. */
403 sub_remove(idp
, (idp
->layers
- 1) * IDR_BITS
, id
);
404 if (idp
->top
&& idp
->top
->count
== 1 && (idp
->layers
> 1) &&
407 * Single child at leftmost slot: we can shrink the tree.
408 * This level is not needed anymore since when layers are
409 * inserted, they are inserted at the top of the existing
413 p
= idp
->top
->ary
[0];
414 rcu_assign_pointer(idp
->top
, p
);
416 to_free
->bitmap
= to_free
->count
= 0;
419 while (idp
->id_free_cnt
>= IDR_FREE_MAX
) {
420 p
= get_from_free_list(idp
);
422 * Note: we don't call the rcu callback here, since the only
423 * layers that fall into the freelist are those that have been
426 kmem_cache_free(idr_layer_cache
, p
);
430 EXPORT_SYMBOL(idr_remove
);
433 * idr_remove_all - remove all ids from the given idr tree
436 * idr_destroy() only frees up unused, cached idp_layers, but this
437 * function will remove all id mappings and leave all idp_layers
440 * A typical clean-up sequence for objects stored in an idr tree, will
441 * use idr_for_each() to free all objects, if necessay, then
442 * idr_remove_all() to remove all ids, and idr_destroy() to free
443 * up the cached idr_layers.
445 void idr_remove_all(struct idr
*idp
)
449 struct idr_layer
*pa
[MAX_LEVEL
];
450 struct idr_layer
**paa
= &pa
[0];
452 n
= idp
->layers
* IDR_BITS
;
454 rcu_assign_pointer(idp
->top
, NULL
);
459 while (n
> IDR_BITS
&& p
) {
462 p
= p
->ary
[(id
>> n
) & IDR_MASK
];
466 while (n
< fls(id
)) {
475 EXPORT_SYMBOL(idr_remove_all
);
478 * idr_destroy - release all cached layers within an idr tree
481 void idr_destroy(struct idr
*idp
)
483 while (idp
->id_free_cnt
) {
484 struct idr_layer
*p
= get_from_free_list(idp
);
485 kmem_cache_free(idr_layer_cache
, p
);
488 EXPORT_SYMBOL(idr_destroy
);
491 * idr_find - return pointer for given id
495 * Return the pointer given the id it has been registered with. A %NULL
496 * return indicates that @id is not valid or you passed %NULL in
499 * This function can be called under rcu_read_lock(), given that the leaf
500 * pointers lifetimes are correctly managed.
502 void *idr_find(struct idr
*idp
, int id
)
507 p
= rcu_dereference_raw(idp
->top
);
510 n
= (p
->layer
+1) * IDR_BITS
;
512 /* Mask off upper bits we don't use for the search. */
521 BUG_ON(n
!= p
->layer
*IDR_BITS
);
522 p
= rcu_dereference_raw(p
->ary
[(id
>> n
) & IDR_MASK
]);
526 EXPORT_SYMBOL(idr_find
);
529 * idr_for_each - iterate through all stored pointers
531 * @fn: function to be called for each pointer
532 * @data: data passed back to callback function
534 * Iterate over the pointers registered with the given idr. The
535 * callback function will be called for each pointer currently
536 * registered, passing the id, the pointer and the data pointer passed
537 * to this function. It is not safe to modify the idr tree while in
538 * the callback, so functions such as idr_get_new and idr_remove are
541 * We check the return of @fn each time. If it returns anything other
542 * than 0, we break out and return that value.
544 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
546 int idr_for_each(struct idr
*idp
,
547 int (*fn
)(int id
, void *p
, void *data
), void *data
)
549 int n
, id
, max
, error
= 0;
551 struct idr_layer
*pa
[MAX_LEVEL
];
552 struct idr_layer
**paa
= &pa
[0];
554 n
= idp
->layers
* IDR_BITS
;
555 p
= rcu_dereference_raw(idp
->top
);
563 p
= rcu_dereference_raw(p
->ary
[(id
>> n
) & IDR_MASK
]);
567 error
= fn(id
, (void *)p
, data
);
573 while (n
< fls(id
)) {
581 EXPORT_SYMBOL(idr_for_each
);
584 * idr_get_next - lookup next object of id to given id.
586 * @id: pointer to lookup key
588 * Returns pointer to registered object with id, which is next number to
592 void *idr_get_next(struct idr
*idp
, int *nextidp
)
594 struct idr_layer
*p
, *pa
[MAX_LEVEL
];
595 struct idr_layer
**paa
= &pa
[0];
600 n
= idp
->layers
* IDR_BITS
;
602 p
= rcu_dereference(idp
->top
);
610 p
= rcu_dereference(p
->ary
[(id
>> n
) & IDR_MASK
]);
619 while (n
< fls(id
)) {
630 * idr_replace - replace pointer for given id
632 * @ptr: pointer you want associated with the id
635 * Replace the pointer registered with an id and return the old value.
636 * A -ENOENT return indicates that @id was not found.
637 * A -EINVAL return indicates that @id was not within valid constraints.
639 * The caller must serialize with writers.
641 void *idr_replace(struct idr
*idp
, void *ptr
, int id
)
644 struct idr_layer
*p
, *old_p
;
648 return ERR_PTR(-EINVAL
);
650 n
= (p
->layer
+1) * IDR_BITS
;
655 return ERR_PTR(-EINVAL
);
658 while ((n
> 0) && p
) {
659 p
= p
->ary
[(id
>> n
) & IDR_MASK
];
664 if (unlikely(p
== NULL
|| !test_bit(n
, &p
->bitmap
)))
665 return ERR_PTR(-ENOENT
);
668 rcu_assign_pointer(p
->ary
[n
], ptr
);
672 EXPORT_SYMBOL(idr_replace
);
674 void __init
idr_init_cache(void)
676 idr_layer_cache
= kmem_cache_create("idr_layer_cache",
677 sizeof(struct idr_layer
), 0, SLAB_PANIC
, NULL
);
681 * idr_init - initialize idr handle
684 * This function is use to set up the handle (@idp) that you will pass
685 * to the rest of the functions.
687 void idr_init(struct idr
*idp
)
689 memset(idp
, 0, sizeof(struct idr
));
690 spin_lock_init(&idp
->lock
);
692 EXPORT_SYMBOL(idr_init
);
696 * IDA - IDR based ID allocator
698 * this is id allocator without id -> pointer translation. Memory
699 * usage is much lower than full blown idr because each id only
700 * occupies a bit. ida uses a custom leaf node which contains
701 * IDA_BITMAP_BITS slots.
703 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
706 static void free_bitmap(struct ida
*ida
, struct ida_bitmap
*bitmap
)
710 if (!ida
->free_bitmap
) {
711 spin_lock_irqsave(&ida
->idr
.lock
, flags
);
712 if (!ida
->free_bitmap
) {
713 ida
->free_bitmap
= bitmap
;
716 spin_unlock_irqrestore(&ida
->idr
.lock
, flags
);
723 * ida_pre_get - reserve resources for ida allocation
725 * @gfp_mask: memory allocation flag
727 * This function should be called prior to locking and calling the
728 * following function. It preallocates enough memory to satisfy the
729 * worst possible allocation.
731 * If the system is REALLY out of memory this function returns 0,
734 int ida_pre_get(struct ida
*ida
, gfp_t gfp_mask
)
736 /* allocate idr_layers */
737 if (!idr_pre_get(&ida
->idr
, gfp_mask
))
740 /* allocate free_bitmap */
741 if (!ida
->free_bitmap
) {
742 struct ida_bitmap
*bitmap
;
744 bitmap
= kmalloc(sizeof(struct ida_bitmap
), gfp_mask
);
748 free_bitmap(ida
, bitmap
);
753 EXPORT_SYMBOL(ida_pre_get
);
756 * ida_get_new_above - allocate new ID above or equal to a start id
758 * @staring_id: id to start search at
759 * @p_id: pointer to the allocated handle
761 * Allocate new ID above or equal to @ida. It should be called with
762 * any required locks.
764 * If memory is required, it will return -EAGAIN, you should unlock
765 * and go back to the ida_pre_get() call. If the ida is full, it will
768 * @p_id returns a value in the range @starting_id ... 0x7fffffff.
770 int ida_get_new_above(struct ida
*ida
, int starting_id
, int *p_id
)
772 struct idr_layer
*pa
[MAX_LEVEL
];
773 struct ida_bitmap
*bitmap
;
775 int idr_id
= starting_id
/ IDA_BITMAP_BITS
;
776 int offset
= starting_id
% IDA_BITMAP_BITS
;
780 /* get vacant slot */
781 t
= idr_get_empty_slot(&ida
->idr
, idr_id
, pa
);
783 return _idr_rc_to_errno(t
);
785 if (t
* IDA_BITMAP_BITS
>= MAX_ID_BIT
)
792 /* if bitmap isn't there, create a new one */
793 bitmap
= (void *)pa
[0]->ary
[idr_id
& IDR_MASK
];
795 spin_lock_irqsave(&ida
->idr
.lock
, flags
);
796 bitmap
= ida
->free_bitmap
;
797 ida
->free_bitmap
= NULL
;
798 spin_unlock_irqrestore(&ida
->idr
.lock
, flags
);
803 memset(bitmap
, 0, sizeof(struct ida_bitmap
));
804 rcu_assign_pointer(pa
[0]->ary
[idr_id
& IDR_MASK
],
809 /* lookup for empty slot */
810 t
= find_next_zero_bit(bitmap
->bitmap
, IDA_BITMAP_BITS
, offset
);
811 if (t
== IDA_BITMAP_BITS
) {
812 /* no empty slot after offset, continue to the next chunk */
818 id
= idr_id
* IDA_BITMAP_BITS
+ t
;
819 if (id
>= MAX_ID_BIT
)
822 __set_bit(t
, bitmap
->bitmap
);
823 if (++bitmap
->nr_busy
== IDA_BITMAP_BITS
)
824 idr_mark_full(pa
, idr_id
);
828 /* Each leaf node can handle nearly a thousand slots and the
829 * whole idea of ida is to have small memory foot print.
830 * Throw away extra resources one by one after each successful
833 if (ida
->idr
.id_free_cnt
|| ida
->free_bitmap
) {
834 struct idr_layer
*p
= get_from_free_list(&ida
->idr
);
836 kmem_cache_free(idr_layer_cache
, p
);
841 EXPORT_SYMBOL(ida_get_new_above
);
844 * ida_get_new - allocate new ID
846 * @p_id: pointer to the allocated handle
848 * Allocate new ID. It should be called with any required locks.
850 * If memory is required, it will return -EAGAIN, you should unlock
851 * and go back to the idr_pre_get() call. If the idr is full, it will
854 * @id returns a value in the range 0 ... 0x7fffffff.
856 int ida_get_new(struct ida
*ida
, int *p_id
)
858 return ida_get_new_above(ida
, 0, p_id
);
860 EXPORT_SYMBOL(ida_get_new
);
863 * ida_remove - remove the given ID
867 void ida_remove(struct ida
*ida
, int id
)
869 struct idr_layer
*p
= ida
->idr
.top
;
870 int shift
= (ida
->idr
.layers
- 1) * IDR_BITS
;
871 int idr_id
= id
/ IDA_BITMAP_BITS
;
872 int offset
= id
% IDA_BITMAP_BITS
;
874 struct ida_bitmap
*bitmap
;
876 /* clear full bits while looking up the leaf idr_layer */
877 while ((shift
> 0) && p
) {
878 n
= (idr_id
>> shift
) & IDR_MASK
;
879 __clear_bit(n
, &p
->bitmap
);
887 n
= idr_id
& IDR_MASK
;
888 __clear_bit(n
, &p
->bitmap
);
890 bitmap
= (void *)p
->ary
[n
];
891 if (!test_bit(offset
, bitmap
->bitmap
))
894 /* update bitmap and remove it if empty */
895 __clear_bit(offset
, bitmap
->bitmap
);
896 if (--bitmap
->nr_busy
== 0) {
897 __set_bit(n
, &p
->bitmap
); /* to please idr_remove() */
898 idr_remove(&ida
->idr
, idr_id
);
899 free_bitmap(ida
, bitmap
);
906 "ida_remove called for id=%d which is not allocated.\n", id
);
908 EXPORT_SYMBOL(ida_remove
);
911 * ida_destroy - release all cached layers within an ida tree
914 void ida_destroy(struct ida
*ida
)
916 idr_destroy(&ida
->idr
);
917 kfree(ida
->free_bitmap
);
919 EXPORT_SYMBOL(ida_destroy
);
922 * ida_init - initialize ida handle
925 * This function is use to set up the handle (@ida) that you will pass
926 * to the rest of the functions.
928 void ida_init(struct ida
*ida
)
930 memset(ida
, 0, sizeof(struct ida
));
934 EXPORT_SYMBOL(ida_init
);
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