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/string.h>
33 #include <linux/idr.h>
35 static kmem_cache_t
*idr_layer_cache
;
37 static struct idr_layer
*alloc_layer(struct idr
*idp
)
41 spin_lock(&idp
->lock
);
42 if ((p
= idp
->id_free
)) {
43 idp
->id_free
= p
->ary
[0];
47 spin_unlock(&idp
->lock
);
51 static void free_layer(struct idr
*idp
, struct idr_layer
*p
)
54 * Depends on the return element being zeroed.
56 spin_lock(&idp
->lock
);
57 p
->ary
[0] = idp
->id_free
;
60 spin_unlock(&idp
->lock
);
64 * idr_pre_get - reserver resources for idr allocation
66 * @gfp_mask: memory allocation flags
68 * This function should be called prior to locking and calling the
69 * following function. It preallocates enough memory to satisfy
70 * the worst possible allocation.
72 * If the system is REALLY out of memory this function returns 0,
75 int idr_pre_get(struct idr
*idp
, gfp_t gfp_mask
)
77 while (idp
->id_free_cnt
< IDR_FREE_MAX
) {
78 struct idr_layer
*new;
79 new = kmem_cache_alloc(idr_layer_cache
, gfp_mask
);
86 EXPORT_SYMBOL(idr_pre_get
);
88 static int sub_alloc(struct idr
*idp
, void *ptr
, int *starting_id
)
91 struct idr_layer
*p
, *new;
92 struct idr_layer
*pa
[MAX_LEVEL
];
102 * We run around this while until we reach the leaf node...
104 n
= (id
>> (IDR_BITS
*l
)) & IDR_MASK
;
106 m
= find_next_bit(&bm
, IDR_SIZE
, n
);
108 /* no space available go back to previous layer. */
110 id
= (id
| ((1 << (IDR_BITS
* l
)) - 1)) + 1;
119 id
= ((id
>> sh
) ^ n
^ m
) << sh
;
121 if ((id
>= MAX_ID_BIT
) || (id
< 0))
126 * Create the layer below if it is missing.
129 if (!(new = alloc_layer(idp
)))
138 * We have reached the leaf node, plant the
139 * users pointer and return the raw id.
141 p
->ary
[m
] = (struct idr_layer
*)ptr
;
142 __set_bit(m
, &p
->bitmap
);
145 * If this layer is full mark the bit in the layer above
146 * to show that this part of the radix tree is full.
147 * This may complete the layer above and require walking
151 while (p
->bitmap
== IDR_FULL
) {
155 __set_bit((n
& IDR_MASK
), &p
->bitmap
);
160 static int idr_get_new_above_int(struct idr
*idp
, void *ptr
, int starting_id
)
162 struct idr_layer
*p
, *new;
168 layers
= idp
->layers
;
170 if (!(p
= alloc_layer(idp
)))
175 * Add a new layer to the top of the tree if the requested
176 * id is larger than the currently allocated space.
178 while ((layers
< (MAX_LEVEL
- 1)) && (id
>= (1 << (layers
*IDR_BITS
)))) {
182 if (!(new = alloc_layer(idp
))) {
184 * The allocation failed. If we built part of
185 * the structure tear it down.
187 for (new = p
; p
&& p
!= idp
->top
; new = p
) {
190 new->bitmap
= new->count
= 0;
191 free_layer(idp
, new);
197 if (p
->bitmap
== IDR_FULL
)
198 __set_bit(0, &new->bitmap
);
202 idp
->layers
= layers
;
203 v
= sub_alloc(idp
, ptr
, &id
);
210 * idr_get_new_above - allocate new idr entry above or equal to a start id
212 * @ptr: pointer you want associated with the ide
213 * @start_id: id to start search at
214 * @id: pointer to the allocated handle
216 * This is the allocate id function. It should be called with any
219 * If memory is required, it will return -EAGAIN, you should unlock
220 * and go back to the idr_pre_get() call. If the idr is full, it will
223 * @id returns a value in the range 0 ... 0x7fffffff
225 int idr_get_new_above(struct idr
*idp
, void *ptr
, int starting_id
, int *id
)
229 rv
= idr_get_new_above_int(idp
, ptr
, starting_id
);
231 * This is a cheap hack until the IDR code can be fixed to
232 * return proper error values.
237 else /* Will be -3 */
243 EXPORT_SYMBOL(idr_get_new_above
);
246 * idr_get_new - allocate new idr entry
248 * @ptr: pointer you want associated with the ide
249 * @id: pointer to the allocated handle
251 * This is the allocate id function. It should be called with any
254 * If memory is required, it will return -EAGAIN, you should unlock
255 * and go back to the idr_pre_get() call. If the idr is full, it will
258 * @id returns a value in the range 0 ... 0x7fffffff
260 int idr_get_new(struct idr
*idp
, void *ptr
, int *id
)
264 rv
= idr_get_new_above_int(idp
, ptr
, 0);
266 * This is a cheap hack until the IDR code can be fixed to
267 * return proper error values.
272 else /* Will be -3 */
278 EXPORT_SYMBOL(idr_get_new
);
280 static void idr_remove_warning(int id
)
282 printk("idr_remove called for id=%d which is not allocated.\n", id
);
286 static void sub_remove(struct idr
*idp
, int shift
, int id
)
288 struct idr_layer
*p
= idp
->top
;
289 struct idr_layer
**pa
[MAX_LEVEL
];
290 struct idr_layer
***paa
= &pa
[0];
296 while ((shift
> 0) && p
) {
297 n
= (id
>> shift
) & IDR_MASK
;
298 __clear_bit(n
, &p
->bitmap
);
304 if (likely(p
!= NULL
&& test_bit(n
, &p
->bitmap
))){
305 __clear_bit(n
, &p
->bitmap
);
307 while(*paa
&& ! --((**paa
)->count
)){
308 free_layer(idp
, **paa
);
314 idr_remove_warning(id
);
318 * idr_remove - remove the given id and free it's slot
322 void idr_remove(struct idr
*idp
, int id
)
326 /* Mask off upper bits we don't use for the search. */
329 sub_remove(idp
, (idp
->layers
- 1) * IDR_BITS
, id
);
330 if (idp
->top
&& idp
->top
->count
== 1 && (idp
->layers
> 1) &&
331 idp
->top
->ary
[0]) { // We can drop a layer
333 p
= idp
->top
->ary
[0];
334 idp
->top
->bitmap
= idp
->top
->count
= 0;
335 free_layer(idp
, idp
->top
);
339 while (idp
->id_free_cnt
>= IDR_FREE_MAX
) {
340 p
= alloc_layer(idp
);
341 kmem_cache_free(idr_layer_cache
, p
);
345 EXPORT_SYMBOL(idr_remove
);
348 * idr_destroy - release all cached layers within an idr tree
351 void idr_destroy(struct idr
*idp
)
353 while (idp
->id_free_cnt
) {
354 struct idr_layer
*p
= alloc_layer(idp
);
355 kmem_cache_free(idr_layer_cache
, p
);
358 EXPORT_SYMBOL(idr_destroy
);
361 * idr_find - return pointer for given id
365 * Return the pointer given the id it has been registered with. A %NULL
366 * return indicates that @id is not valid or you passed %NULL in
369 * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
371 void *idr_find(struct idr
*idp
, int id
)
376 n
= idp
->layers
* IDR_BITS
;
379 /* Mask off upper bits we don't use for the search. */
387 p
= p
->ary
[(id
>> n
) & IDR_MASK
];
391 EXPORT_SYMBOL(idr_find
);
393 static void idr_cache_ctor(void * idr_layer
, kmem_cache_t
*idr_layer_cache
,
396 memset(idr_layer
, 0, sizeof(struct idr_layer
));
399 static int init_id_cache(void)
401 if (!idr_layer_cache
)
402 idr_layer_cache
= kmem_cache_create("idr_layer_cache",
403 sizeof(struct idr_layer
), 0, 0, idr_cache_ctor
, NULL
);
408 * idr_init - initialize idr handle
411 * This function is use to set up the handle (@idp) that you will pass
412 * to the rest of the functions.
414 void idr_init(struct idr
*idp
)
417 memset(idp
, 0, sizeof(struct idr
));
418 spin_lock_init(&idp
->lock
);
420 EXPORT_SYMBOL(idr_init
);