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git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - lib/idr.c
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 * Small id to pointer translation service.
11 * It uses a radix tree like structure as a sparse array indexed
12 * by the id to obtain the pointer. The bitmap makes allocating
15 * You call it to allocate an id (an int) an associate with that id a
16 * pointer or what ever, we treat it as a (void *). You can pass this
17 * id to a user for him to pass back at a later time. You then pass
18 * that id to this code and it returns your pointer.
20 * You can release ids at any time. When all ids are released, most of
21 * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
22 * don't need to go to the memory "store" during an id allocate, just
23 * so you don't need to be too concerned about locking and conflicts
24 * with the slab allocator.
27 #ifndef TEST // to test in user space...
28 #include <linux/slab.h>
29 #include <linux/init.h>
30 #include <linux/module.h>
32 #include <linux/err.h>
33 #include <linux/string.h>
34 #include <linux/idr.h>
36 static struct kmem_cache
*idr_layer_cache
;
38 static struct idr_layer
*alloc_layer(struct idr
*idp
)
43 spin_lock_irqsave(&idp
->lock
, flags
);
44 if ((p
= idp
->id_free
)) {
45 idp
->id_free
= p
->ary
[0];
49 spin_unlock_irqrestore(&idp
->lock
, flags
);
53 /* only called when idp->lock is held */
54 static void __free_layer(struct idr
*idp
, struct idr_layer
*p
)
56 p
->ary
[0] = idp
->id_free
;
61 static void free_layer(struct idr
*idp
, struct idr_layer
*p
)
66 * Depends on the return element being zeroed.
68 spin_lock_irqsave(&idp
->lock
, flags
);
70 spin_unlock_irqrestore(&idp
->lock
, flags
);
74 * idr_pre_get - reserver resources for idr allocation
76 * @gfp_mask: memory allocation flags
78 * This function should be called prior to locking and calling the
79 * following function. It preallocates enough memory to satisfy
80 * the worst possible allocation.
82 * If the system is REALLY out of memory this function returns 0,
85 int idr_pre_get(struct idr
*idp
, gfp_t gfp_mask
)
87 while (idp
->id_free_cnt
< IDR_FREE_MAX
) {
88 struct idr_layer
*new;
89 new = kmem_cache_alloc(idr_layer_cache
, gfp_mask
);
96 EXPORT_SYMBOL(idr_pre_get
);
98 static int sub_alloc(struct idr
*idp
, void *ptr
, int *starting_id
)
101 struct idr_layer
*p
, *new;
102 struct idr_layer
*pa
[MAX_LEVEL
];
112 * We run around this while until we reach the leaf node...
114 n
= (id
>> (IDR_BITS
*l
)) & IDR_MASK
;
116 m
= find_next_bit(&bm
, IDR_SIZE
, n
);
118 /* no space available go back to previous layer. */
120 id
= (id
| ((1 << (IDR_BITS
* l
)) - 1)) + 1;
129 id
= ((id
>> sh
) ^ n
^ m
) << sh
;
131 if ((id
>= MAX_ID_BIT
) || (id
< 0))
136 * Create the layer below if it is missing.
139 if (!(new = alloc_layer(idp
)))
148 * We have reached the leaf node, plant the
149 * users pointer and return the raw id.
151 p
->ary
[m
] = (struct idr_layer
*)ptr
;
152 __set_bit(m
, &p
->bitmap
);
155 * If this layer is full mark the bit in the layer above
156 * to show that this part of the radix tree is full.
157 * This may complete the layer above and require walking
161 while (p
->bitmap
== IDR_FULL
) {
165 __set_bit((n
& IDR_MASK
), &p
->bitmap
);
170 static int idr_get_new_above_int(struct idr
*idp
, void *ptr
, int starting_id
)
172 struct idr_layer
*p
, *new;
179 layers
= idp
->layers
;
181 if (!(p
= alloc_layer(idp
)))
186 * Add a new layer to the top of the tree if the requested
187 * id is larger than the currently allocated space.
189 while ((layers
< (MAX_LEVEL
- 1)) && (id
>= (1 << (layers
*IDR_BITS
)))) {
193 if (!(new = alloc_layer(idp
))) {
195 * The allocation failed. If we built part of
196 * the structure tear it down.
198 spin_lock_irqsave(&idp
->lock
, flags
);
199 for (new = p
; p
&& p
!= idp
->top
; new = p
) {
202 new->bitmap
= new->count
= 0;
203 __free_layer(idp
, new);
205 spin_unlock_irqrestore(&idp
->lock
, flags
);
210 if (p
->bitmap
== IDR_FULL
)
211 __set_bit(0, &new->bitmap
);
215 idp
->layers
= layers
;
216 v
= sub_alloc(idp
, ptr
, &id
);
223 * idr_get_new_above - allocate new idr entry above or equal to a start id
225 * @ptr: pointer you want associated with the ide
226 * @start_id: id to start search at
227 * @id: pointer to the allocated handle
229 * This is the allocate id function. It should be called with any
232 * If memory is required, it will return -EAGAIN, you should unlock
233 * and go back to the idr_pre_get() call. If the idr is full, it will
236 * @id returns a value in the range 0 ... 0x7fffffff
238 int idr_get_new_above(struct idr
*idp
, void *ptr
, int starting_id
, int *id
)
242 rv
= idr_get_new_above_int(idp
, ptr
, starting_id
);
244 * This is a cheap hack until the IDR code can be fixed to
245 * return proper error values.
250 else /* Will be -3 */
256 EXPORT_SYMBOL(idr_get_new_above
);
259 * idr_get_new - allocate new idr entry
261 * @ptr: pointer you want associated with the ide
262 * @id: pointer to the allocated handle
264 * This is the allocate id function. It should be called with any
267 * If memory is required, it will return -EAGAIN, you should unlock
268 * and go back to the idr_pre_get() call. If the idr is full, it will
271 * @id returns a value in the range 0 ... 0x7fffffff
273 int idr_get_new(struct idr
*idp
, void *ptr
, int *id
)
277 rv
= idr_get_new_above_int(idp
, ptr
, 0);
279 * This is a cheap hack until the IDR code can be fixed to
280 * return proper error values.
285 else /* Will be -3 */
291 EXPORT_SYMBOL(idr_get_new
);
293 static void idr_remove_warning(int id
)
295 printk("idr_remove called for id=%d which is not allocated.\n", id
);
299 static void sub_remove(struct idr
*idp
, int shift
, int id
)
301 struct idr_layer
*p
= idp
->top
;
302 struct idr_layer
**pa
[MAX_LEVEL
];
303 struct idr_layer
***paa
= &pa
[0];
309 while ((shift
> 0) && p
) {
310 n
= (id
>> shift
) & IDR_MASK
;
311 __clear_bit(n
, &p
->bitmap
);
317 if (likely(p
!= NULL
&& test_bit(n
, &p
->bitmap
))){
318 __clear_bit(n
, &p
->bitmap
);
320 while(*paa
&& ! --((**paa
)->count
)){
321 free_layer(idp
, **paa
);
327 idr_remove_warning(id
);
331 * idr_remove - remove the given id and free it's slot
335 void idr_remove(struct idr
*idp
, int id
)
339 /* Mask off upper bits we don't use for the search. */
342 sub_remove(idp
, (idp
->layers
- 1) * IDR_BITS
, id
);
343 if (idp
->top
&& idp
->top
->count
== 1 && (idp
->layers
> 1) &&
344 idp
->top
->ary
[0]) { // We can drop a layer
346 p
= idp
->top
->ary
[0];
347 idp
->top
->bitmap
= idp
->top
->count
= 0;
348 free_layer(idp
, idp
->top
);
352 while (idp
->id_free_cnt
>= IDR_FREE_MAX
) {
353 p
= alloc_layer(idp
);
354 kmem_cache_free(idr_layer_cache
, p
);
358 EXPORT_SYMBOL(idr_remove
);
361 * idr_destroy - release all cached layers within an idr tree
364 void idr_destroy(struct idr
*idp
)
366 while (idp
->id_free_cnt
) {
367 struct idr_layer
*p
= alloc_layer(idp
);
368 kmem_cache_free(idr_layer_cache
, p
);
371 EXPORT_SYMBOL(idr_destroy
);
374 * idr_find - return pointer for given id
378 * Return the pointer given the id it has been registered with. A %NULL
379 * return indicates that @id is not valid or you passed %NULL in
382 * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
384 void *idr_find(struct idr
*idp
, int id
)
389 n
= idp
->layers
* IDR_BITS
;
392 /* Mask off upper bits we don't use for the search. */
400 p
= p
->ary
[(id
>> n
) & IDR_MASK
];
404 EXPORT_SYMBOL(idr_find
);
407 * idr_replace - replace pointer for given id
409 * @ptr: pointer you want associated with the id
412 * Replace the pointer registered with an id and return the old value.
413 * A -ENOENT return indicates that @id was not found.
414 * A -EINVAL return indicates that @id was not within valid constraints.
416 * The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
418 void *idr_replace(struct idr
*idp
, void *ptr
, int id
)
421 struct idr_layer
*p
, *old_p
;
423 n
= idp
->layers
* IDR_BITS
;
429 return ERR_PTR(-EINVAL
);
432 while ((n
> 0) && p
) {
433 p
= p
->ary
[(id
>> n
) & IDR_MASK
];
438 if (unlikely(p
== NULL
|| !test_bit(n
, &p
->bitmap
)))
439 return ERR_PTR(-ENOENT
);
446 EXPORT_SYMBOL(idr_replace
);
448 static void idr_cache_ctor(void * idr_layer
, struct kmem_cache
*idr_layer_cache
,
451 memset(idr_layer
, 0, sizeof(struct idr_layer
));
454 static int init_id_cache(void)
456 if (!idr_layer_cache
)
457 idr_layer_cache
= kmem_cache_create("idr_layer_cache",
458 sizeof(struct idr_layer
), 0, 0, idr_cache_ctor
, NULL
);
463 * idr_init - initialize idr handle
466 * This function is use to set up the handle (@idp) that you will pass
467 * to the rest of the functions.
469 void idr_init(struct idr
*idp
)
472 memset(idp
, 0, sizeof(struct idr
));
473 spin_lock_init(&idp
->lock
);
475 EXPORT_SYMBOL(idr_init
);