1 #include <linux/bitmap.h>
2 #include <linux/export.h>
4 #include <linux/slab.h>
5 #include <linux/spinlock.h>
7 DEFINE_PER_CPU(struct ida_bitmap
*, ida_bitmap
);
8 static DEFINE_SPINLOCK(simple_ida_lock
);
10 int idr_alloc_cmn(struct idr
*idr
, void *ptr
, unsigned long *index
,
11 unsigned long start
, unsigned long end
, gfp_t gfp
,
14 struct radix_tree_iter iter
;
17 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr
)))
20 radix_tree_iter_init(&iter
, start
);
22 slot
= idr_get_free_ext(&idr
->idr_rt
, &iter
, gfp
, end
);
24 slot
= idr_get_free(&idr
->idr_rt
, &iter
, gfp
, end
);
28 radix_tree_iter_replace(&idr
->idr_rt
, &iter
, slot
, ptr
);
29 radix_tree_iter_tag_clear(&idr
->idr_rt
, &iter
, IDR_FREE
);
35 EXPORT_SYMBOL_GPL(idr_alloc_cmn
);
38 * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
40 * @ptr: pointer to be associated with the new id
41 * @start: the minimum id (inclusive)
42 * @end: the maximum id (exclusive)
43 * @gfp: memory allocation flags
45 * Allocates an ID larger than the last ID allocated if one is available.
46 * If not, it will attempt to allocate the smallest ID that is larger or
49 int idr_alloc_cyclic(struct idr
*idr
, void *ptr
, int start
, int end
, gfp_t gfp
)
51 int id
, curr
= idr
->idr_next
;
56 id
= idr_alloc(idr
, ptr
, curr
, end
, gfp
);
57 if ((id
== -ENOSPC
) && (curr
> start
))
58 id
= idr_alloc(idr
, ptr
, start
, curr
, gfp
);
61 idr
->idr_next
= id
+ 1U;
65 EXPORT_SYMBOL(idr_alloc_cyclic
);
68 * idr_for_each - iterate through all stored pointers
70 * @fn: function to be called for each pointer
71 * @data: data passed to callback function
73 * The callback function will be called for each entry in @idr, passing
74 * the id, the pointer and the data pointer passed to this function.
76 * If @fn returns anything other than %0, the iteration stops and that
77 * value is returned from this function.
79 * idr_for_each() can be called concurrently with idr_alloc() and
80 * idr_remove() if protected by RCU. Newly added entries may not be
81 * seen and deleted entries may be seen, but adding and removing entries
82 * will not cause other entries to be skipped, nor spurious ones to be seen.
84 int idr_for_each(const struct idr
*idr
,
85 int (*fn
)(int id
, void *p
, void *data
), void *data
)
87 struct radix_tree_iter iter
;
90 radix_tree_for_each_slot(slot
, &idr
->idr_rt
, &iter
, 0) {
91 int ret
= fn(iter
.index
, rcu_dereference_raw(*slot
), data
);
98 EXPORT_SYMBOL(idr_for_each
);
101 * idr_get_next - Find next populated entry
103 * @nextid: Pointer to lowest possible ID to return
105 * Returns the next populated entry in the tree with an ID greater than
106 * or equal to the value pointed to by @nextid. On exit, @nextid is updated
107 * to the ID of the found value. To use in a loop, the value pointed to by
108 * nextid must be incremented by the user.
110 void *idr_get_next(struct idr
*idr
, int *nextid
)
112 struct radix_tree_iter iter
;
116 radix_tree_for_each_slot(slot
, &idr
->idr_rt
, &iter
, *nextid
) {
117 entry
= rcu_dereference_raw(*slot
);
120 if (!radix_tree_deref_retry(entry
))
122 if (slot
!= (void *)&idr
->idr_rt
.rnode
&&
123 entry
!= (void *)RADIX_TREE_INTERNAL_NODE
)
125 slot
= radix_tree_iter_retry(&iter
);
130 if (WARN_ON_ONCE(iter
.index
> INT_MAX
))
133 *nextid
= iter
.index
;
136 EXPORT_SYMBOL(idr_get_next
);
138 void *idr_get_next_ext(struct idr
*idr
, unsigned long *nextid
)
140 struct radix_tree_iter iter
;
143 slot
= radix_tree_iter_find(&idr
->idr_rt
, &iter
, *nextid
);
147 *nextid
= iter
.index
;
148 return rcu_dereference_raw(*slot
);
150 EXPORT_SYMBOL(idr_get_next_ext
);
153 * idr_replace - replace pointer for given id
155 * @ptr: New pointer to associate with the ID
158 * Replace the pointer registered with an ID and return the old value.
159 * This function can be called under the RCU read lock concurrently with
160 * idr_alloc() and idr_remove() (as long as the ID being removed is not
161 * the one being replaced!).
163 * Returns: the old value on success. %-ENOENT indicates that @id was not
164 * found. %-EINVAL indicates that @id or @ptr were not valid.
166 void *idr_replace(struct idr
*idr
, void *ptr
, int id
)
169 return ERR_PTR(-EINVAL
);
171 return idr_replace_ext(idr
, ptr
, id
);
173 EXPORT_SYMBOL(idr_replace
);
175 void *idr_replace_ext(struct idr
*idr
, void *ptr
, unsigned long id
)
177 struct radix_tree_node
*node
;
178 void __rcu
**slot
= NULL
;
181 if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr
)))
182 return ERR_PTR(-EINVAL
);
184 entry
= __radix_tree_lookup(&idr
->idr_rt
, id
, &node
, &slot
);
185 if (!slot
|| radix_tree_tag_get(&idr
->idr_rt
, id
, IDR_FREE
))
186 return ERR_PTR(-ENOENT
);
188 __radix_tree_replace(&idr
->idr_rt
, node
, slot
, ptr
, NULL
);
192 EXPORT_SYMBOL(idr_replace_ext
);
195 * DOC: IDA description
197 * The IDA is an ID allocator which does not provide the ability to
198 * associate an ID with a pointer. As such, it only needs to store one
199 * bit per ID, and so is more space efficient than an IDR. To use an IDA,
200 * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
201 * then initialise it using ida_init()). To allocate a new ID, call
202 * ida_simple_get(). To free an ID, call ida_simple_remove().
204 * If you have more complex locking requirements, use a loop around
205 * ida_pre_get() and ida_get_new() to allocate a new ID. Then use
206 * ida_remove() to free an ID. You must make sure that ida_get_new() and
207 * ida_remove() cannot be called at the same time as each other for the
210 * You can also use ida_get_new_above() if you need an ID to be allocated
211 * above a particular number. ida_destroy() can be used to dispose of an
212 * IDA without needing to free the individual IDs in it. You can use
213 * ida_is_empty() to find out whether the IDA has any IDs currently allocated.
215 * IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
216 * limitation, it should be quite straightforward to raise the maximum.
222 * The IDA uses the functionality provided by the IDR & radix tree to store
223 * bitmaps in each entry. The IDR_FREE tag means there is at least one bit
224 * free, unlike the IDR where it means at least one entry is free.
226 * I considered telling the radix tree that each slot is an order-10 node
227 * and storing the bit numbers in the radix tree, but the radix tree can't
228 * allow a single multiorder entry at index 0, which would significantly
229 * increase memory consumption for the IDA. So instead we divide the index
230 * by the number of bits in the leaf bitmap before doing a radix tree lookup.
232 * As an optimisation, if there are only a few low bits set in any given
233 * leaf, instead of allocating a 128-byte bitmap, we use the 'exceptional
234 * entry' functionality of the radix tree to store BITS_PER_LONG - 2 bits
235 * directly in the entry. By being really tricksy, we could store
236 * BITS_PER_LONG - 1 bits, but there're diminishing returns after optimising
237 * for 0-3 allocated IDs.
239 * We allow the radix tree 'exceptional' count to get out of date. Nothing
240 * in the IDA nor the radix tree code checks it. If it becomes important
241 * to maintain an accurate exceptional count, switch the rcu_assign_pointer()
242 * calls to radix_tree_iter_replace() which will correct the exceptional
245 * The IDA always requires a lock to alloc/free. If we add a 'test_bit'
246 * equivalent, it will still need locking. Going to RCU lookup would require
247 * using RCU to free bitmaps, and that's not trivial without embedding an
248 * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
249 * bitmap, which is excessive.
252 #define IDA_MAX (0x80000000U / IDA_BITMAP_BITS)
255 * ida_get_new_above - allocate new ID above or equal to a start id
257 * @start: id to start search at
258 * @id: pointer to the allocated handle
260 * Allocate new ID above or equal to @start. It should be called
261 * with any required locks to ensure that concurrent calls to
262 * ida_get_new_above() / ida_get_new() / ida_remove() are not allowed.
263 * Consider using ida_simple_get() if you do not have complex locking
266 * If memory is required, it will return %-EAGAIN, you should unlock
267 * and go back to the ida_pre_get() call. If the ida is full, it will
268 * return %-ENOSPC. On success, it will return 0.
270 * @id returns a value in the range @start ... %0x7fffffff.
272 int ida_get_new_above(struct ida
*ida
, int start
, int *id
)
274 struct radix_tree_root
*root
= &ida
->ida_rt
;
276 struct radix_tree_iter iter
;
277 struct ida_bitmap
*bitmap
;
282 index
= start
/ IDA_BITMAP_BITS
;
283 bit
= start
% IDA_BITMAP_BITS
;
284 ebit
= bit
+ RADIX_TREE_EXCEPTIONAL_SHIFT
;
286 slot
= radix_tree_iter_init(&iter
, index
);
289 slot
= radix_tree_next_slot(slot
, &iter
,
290 RADIX_TREE_ITER_TAGGED
);
292 slot
= idr_get_free(root
, &iter
, GFP_NOWAIT
, IDA_MAX
);
294 if (slot
== ERR_PTR(-ENOMEM
))
296 return PTR_ERR(slot
);
299 if (iter
.index
> index
) {
301 ebit
= RADIX_TREE_EXCEPTIONAL_SHIFT
;
303 new = iter
.index
* IDA_BITMAP_BITS
;
304 bitmap
= rcu_dereference_raw(*slot
);
305 if (radix_tree_exception(bitmap
)) {
306 unsigned long tmp
= (unsigned long)bitmap
;
307 ebit
= find_next_zero_bit(&tmp
, BITS_PER_LONG
, ebit
);
308 if (ebit
< BITS_PER_LONG
) {
310 rcu_assign_pointer(*slot
, (void *)tmp
);
311 *id
= new + ebit
- RADIX_TREE_EXCEPTIONAL_SHIFT
;
314 bitmap
= this_cpu_xchg(ida_bitmap
, NULL
);
317 memset(bitmap
, 0, sizeof(*bitmap
));
318 bitmap
->bitmap
[0] = tmp
>> RADIX_TREE_EXCEPTIONAL_SHIFT
;
319 rcu_assign_pointer(*slot
, bitmap
);
323 bit
= find_next_zero_bit(bitmap
->bitmap
,
324 IDA_BITMAP_BITS
, bit
);
328 if (bit
== IDA_BITMAP_BITS
)
331 __set_bit(bit
, bitmap
->bitmap
);
332 if (bitmap_full(bitmap
->bitmap
, IDA_BITMAP_BITS
))
333 radix_tree_iter_tag_clear(root
, &iter
,
339 if (ebit
< BITS_PER_LONG
) {
340 bitmap
= (void *)((1UL << ebit
) |
341 RADIX_TREE_EXCEPTIONAL_ENTRY
);
342 radix_tree_iter_replace(root
, &iter
, slot
,
347 bitmap
= this_cpu_xchg(ida_bitmap
, NULL
);
350 memset(bitmap
, 0, sizeof(*bitmap
));
351 __set_bit(bit
, bitmap
->bitmap
);
352 radix_tree_iter_replace(root
, &iter
, slot
, bitmap
);
359 EXPORT_SYMBOL(ida_get_new_above
);
362 * ida_remove - Free the given ID
366 * This function should not be called at the same time as ida_get_new_above().
368 void ida_remove(struct ida
*ida
, int id
)
370 unsigned long index
= id
/ IDA_BITMAP_BITS
;
371 unsigned offset
= id
% IDA_BITMAP_BITS
;
372 struct ida_bitmap
*bitmap
;
374 struct radix_tree_iter iter
;
377 slot
= radix_tree_iter_lookup(&ida
->ida_rt
, &iter
, index
);
381 bitmap
= rcu_dereference_raw(*slot
);
382 if (radix_tree_exception(bitmap
)) {
383 btmp
= (unsigned long *)slot
;
384 offset
+= RADIX_TREE_EXCEPTIONAL_SHIFT
;
385 if (offset
>= BITS_PER_LONG
)
388 btmp
= bitmap
->bitmap
;
390 if (!test_bit(offset
, btmp
))
393 __clear_bit(offset
, btmp
);
394 radix_tree_iter_tag_set(&ida
->ida_rt
, &iter
, IDR_FREE
);
395 if (radix_tree_exception(bitmap
)) {
396 if (rcu_dereference_raw(*slot
) ==
397 (void *)RADIX_TREE_EXCEPTIONAL_ENTRY
)
398 radix_tree_iter_delete(&ida
->ida_rt
, &iter
, slot
);
399 } else if (bitmap_empty(btmp
, IDA_BITMAP_BITS
)) {
401 radix_tree_iter_delete(&ida
->ida_rt
, &iter
, slot
);
405 WARN(1, "ida_remove called for id=%d which is not allocated.\n", id
);
407 EXPORT_SYMBOL(ida_remove
);
410 * ida_destroy - Free the contents of an ida
413 * Calling this function releases all resources associated with an IDA. When
414 * this call returns, the IDA is empty and can be reused or freed. The caller
415 * should not allow ida_remove() or ida_get_new_above() to be called at the
418 void ida_destroy(struct ida
*ida
)
420 struct radix_tree_iter iter
;
423 radix_tree_for_each_slot(slot
, &ida
->ida_rt
, &iter
, 0) {
424 struct ida_bitmap
*bitmap
= rcu_dereference_raw(*slot
);
425 if (!radix_tree_exception(bitmap
))
427 radix_tree_iter_delete(&ida
->ida_rt
, &iter
, slot
);
430 EXPORT_SYMBOL(ida_destroy
);
433 * ida_simple_get - get a new id.
434 * @ida: the (initialized) ida.
435 * @start: the minimum id (inclusive, < 0x8000000)
436 * @end: the maximum id (exclusive, < 0x8000000 or 0)
437 * @gfp_mask: memory allocation flags
439 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
440 * On memory allocation failure, returns -ENOMEM.
442 * Compared to ida_get_new_above() this function does its own locking, and
443 * should be used unless there are special requirements.
445 * Use ida_simple_remove() to get rid of an id.
447 int ida_simple_get(struct ida
*ida
, unsigned int start
, unsigned int end
,
454 BUG_ON((int)start
< 0);
455 BUG_ON((int)end
< 0);
465 if (!ida_pre_get(ida
, gfp_mask
))
468 spin_lock_irqsave(&simple_ida_lock
, flags
);
469 ret
= ida_get_new_above(ida
, start
, &id
);
478 spin_unlock_irqrestore(&simple_ida_lock
, flags
);
480 if (unlikely(ret
== -EAGAIN
))
485 EXPORT_SYMBOL(ida_simple_get
);
488 * ida_simple_remove - remove an allocated id.
489 * @ida: the (initialized) ida.
490 * @id: the id returned by ida_simple_get.
492 * Use to release an id allocated with ida_simple_get().
494 * Compared to ida_remove() this function does its own locking, and should be
495 * used unless there are special requirements.
497 void ida_simple_remove(struct ida
*ida
, unsigned int id
)
502 spin_lock_irqsave(&simple_ida_lock
, flags
);
504 spin_unlock_irqrestore(&simple_ida_lock
, flags
);
506 EXPORT_SYMBOL(ida_simple_remove
);