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
);
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