Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/lib/idr.c

  1 /*
  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.
  5  *
  6  * Modified by George Anzinger to reuse immediately and to use
  7  * find bit instructions.  Also removed _irq on spinlocks.
  8  *
  9  * Modified by Nadia Derbey to make it RCU safe.
 10  *
 11  * Small id to pointer translation service.
 12  *
 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
 15  * a new id quick.
 16  *
 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.
 21  */
 22 
 23 #ifndef TEST                        // to test in user space...
 24 #include <linux/slab.h>
 25 #include <linux/init.h>
 26 #include <linux/export.h>
 27 #endif
 28 #include <linux/err.h>
 29 #include <linux/string.h>
 30 #include <linux/idr.h>
 31 #include <linux/spinlock.h>
 32 #include <linux/percpu.h>
 33 
 34 #define MAX_IDR_SHIFT           (sizeof(int) * 8 - 1)
 35 #define MAX_IDR_BIT             (1U << MAX_IDR_SHIFT)
 36 
 37 /* Leave the possibility of an incomplete final layer */
 38 #define MAX_IDR_LEVEL ((MAX_IDR_SHIFT + IDR_BITS - 1) / IDR_BITS)
 39 
 40 /* Number of id_layer structs to leave in free list */
 41 #define MAX_IDR_FREE (MAX_IDR_LEVEL * 2)
 42 
 43 static struct kmem_cache *idr_layer_cache;
 44 static DEFINE_PER_CPU(struct idr_layer *, idr_preload_head);
 45 static DEFINE_PER_CPU(int, idr_preload_cnt);
 46 static DEFINE_SPINLOCK(simple_ida_lock);
 47 
 48 /* the maximum ID which can be allocated given idr->layers */
 49 static int idr_max(int layers)
 50 {
 51         int bits = min_t(int, layers * IDR_BITS, MAX_IDR_SHIFT);
 52 
 53         return (1 << bits) - 1;
 54 }
 55 
 56 /*
 57  * Prefix mask for an idr_layer at @layer.  For layer 0, the prefix mask is
 58  * all bits except for the lower IDR_BITS.  For layer 1, 2 * IDR_BITS, and
 59  * so on.
 60  */
 61 static int idr_layer_prefix_mask(int layer)
 62 {
 63         return ~idr_max(layer + 1);
 64 }
 65 
 66 static struct idr_layer *get_from_free_list(struct idr *idp)
 67 {
 68         struct idr_layer *p;
 69         unsigned long flags;
 70 
 71         spin_lock_irqsave(&idp->lock, flags);
 72         if ((p = idp->id_free)) {
 73                 idp->id_free = p->ary[0];
 74                 idp->id_free_cnt--;
 75                 p->ary[0] = NULL;
 76         }
 77         spin_unlock_irqrestore(&idp->lock, flags);
 78         return(p);
 79 }
 80 
 81 /**
 82  * idr_layer_alloc - allocate a new idr_layer
 83  * @gfp_mask: allocation mask
 84  * @layer_idr: optional idr to allocate from
 85  *
 86  * If @layer_idr is %NULL, directly allocate one using @gfp_mask or fetch
 87  * one from the per-cpu preload buffer.  If @layer_idr is not %NULL, fetch
 88  * an idr_layer from @idr->id_free.
 89  *
 90  * @layer_idr is to maintain backward compatibility with the old alloc
 91  * interface - idr_pre_get() and idr_get_new*() - and will be removed
 92  * together with per-pool preload buffer.
 93  */
 94 static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)
 95 {
 96         struct idr_layer *new;
 97 
 98         /* this is the old path, bypass to get_from_free_list() */
 99         if (layer_idr)
100                 return get_from_free_list(layer_idr);
101 
102         /*
103          * Try to allocate directly from kmem_cache.  We want to try this
104          * before preload buffer; otherwise, non-preloading idr_alloc()
105          * users will end up taking advantage of preloading ones.  As the
106          * following is allowed to fail for preloaded cases, suppress
107          * warning this time.
108          */
109         new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN);
110         if (new)
111                 return new;
112 
113         /*
114          * Try to fetch one from the per-cpu preload buffer if in process
115          * context.  See idr_preload() for details.
116          */
117         if (!in_interrupt()) {
118                 preempt_disable();
119                 new = __this_cpu_read(idr_preload_head);
120                 if (new) {
121                         __this_cpu_write(idr_preload_head, new->ary[0]);
122                         __this_cpu_dec(idr_preload_cnt);
123                         new->ary[0] = NULL;
124                 }
125                 preempt_enable();
126                 if (new)
127                         return new;
128         }
129 
130         /*
131          * Both failed.  Try kmem_cache again w/o adding __GFP_NOWARN so
132          * that memory allocation failure warning is printed as intended.
133          */
134         return kmem_cache_zalloc(idr_layer_cache, gfp_mask);
135 }
136 
137 static void idr_layer_rcu_free(struct rcu_head *head)
138 {
139         struct idr_layer *layer;
140 
141         layer = container_of(head, struct idr_layer, rcu_head);
142         kmem_cache_free(idr_layer_cache, layer);
143 }
144 
145 static inline void free_layer(struct idr *idr, struct idr_layer *p)
146 {
147         if (idr->hint == p)
148                 RCU_INIT_POINTER(idr->hint, NULL);
149         call_rcu(&p->rcu_head, idr_layer_rcu_free);
150 }
151 
152 /* only called when idp->lock is held */
153 static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
154 {
155         p->ary[0] = idp->id_free;
156         idp->id_free = p;
157         idp->id_free_cnt++;
158 }
159 
160 static void move_to_free_list(struct idr *idp, struct idr_layer *p)
161 {
162         unsigned long flags;
163 
164         /*
165          * Depends on the return element being zeroed.
166          */
167         spin_lock_irqsave(&idp->lock, flags);
168         __move_to_free_list(idp, p);
169         spin_unlock_irqrestore(&idp->lock, flags);
170 }
171 
172 static void idr_mark_full(struct idr_layer **pa, int id)
173 {
174         struct idr_layer *p = pa[0];
175         int l = 0;
176 
177         __set_bit(id & IDR_MASK, p->bitmap);
178         /*
179          * If this layer is full mark the bit in the layer above to
180          * show that this part of the radix tree is full.  This may
181          * complete the layer above and require walking up the radix
182          * tree.
183          */
184         while (bitmap_full(p->bitmap, IDR_SIZE)) {
185                 if (!(p = pa[++l]))
186                         break;
187                 id = id >> IDR_BITS;
188                 __set_bit((id & IDR_MASK), p->bitmap);
189         }
190 }
191 
192 static int __idr_pre_get(struct idr *idp, gfp_t gfp_mask)
193 {
194         while (idp->id_free_cnt < MAX_IDR_FREE) {
195                 struct idr_layer *new;
196                 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
197                 if (new == NULL)
198                         return (0);
199                 move_to_free_list(idp, new);
200         }
201         return 1;
202 }
203 
204 /**
205  * sub_alloc - try to allocate an id without growing the tree depth
206  * @idp: idr handle
207  * @starting_id: id to start search at
208  * @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer
209  * @gfp_mask: allocation mask for idr_layer_alloc()
210  * @layer_idr: optional idr passed to idr_layer_alloc()
211  *
212  * Allocate an id in range [@starting_id, INT_MAX] from @idp without
213  * growing its depth.  Returns
214  *
215  *  the allocated id >= 0 if successful,
216  *  -EAGAIN if the tree needs to grow for allocation to succeed,
217  *  -ENOSPC if the id space is exhausted,
218  *  -ENOMEM if more idr_layers need to be allocated.
219  */
220 static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa,
221                      gfp_t gfp_mask, struct idr *layer_idr)
222 {
223         int n, m, sh;
224         struct idr_layer *p, *new;
225         int l, id, oid;
226 
227         id = *starting_id;
228  restart:
229         p = idp->top;
230         l = idp->layers;
231         pa[l--] = NULL;
232         while (1) {
233                 /*
234                  * We run around this while until we reach the leaf node...
235                  */
236                 n = (id >> (IDR_BITS*l)) & IDR_MASK;
237                 m = find_next_zero_bit(p->bitmap, IDR_SIZE, n);
238                 if (m == IDR_SIZE) {
239                         /* no space available go back to previous layer. */
240                         l++;
241                         oid = id;
242                         id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
243 
244                         /* if already at the top layer, we need to grow */
245                         if (id > idr_max(idp->layers)) {
246                                 *starting_id = id;
247                                 return -EAGAIN;
248                         }
249                         p = pa[l];
250                         BUG_ON(!p);
251 
252                         /* If we need to go up one layer, continue the
253                          * loop; otherwise, restart from the top.
254                          */
255                         sh = IDR_BITS * (l + 1);
256                         if (oid >> sh == id >> sh)
257                                 continue;
258                         else
259                                 goto restart;
260                 }
261                 if (m != n) {
262                         sh = IDR_BITS*l;
263                         id = ((id >> sh) ^ n ^ m) << sh;
264                 }
265                 if ((id >= MAX_IDR_BIT) || (id < 0))
266                         return -ENOSPC;
267                 if (l == 0)
268                         break;
269                 /*
270                  * Create the layer below if it is missing.
271                  */
272                 if (!p->ary[m]) {
273                         new = idr_layer_alloc(gfp_mask, layer_idr);
274                         if (!new)
275                                 return -ENOMEM;
276                         new->layer = l-1;
277                         new->prefix = id & idr_layer_prefix_mask(new->layer);
278                         rcu_assign_pointer(p->ary[m], new);
279                         p->count++;
280                 }
281                 pa[l--] = p;
282                 p = p->ary[m];
283         }
284 
285         pa[l] = p;
286         return id;
287 }
288 
289 static int idr_get_empty_slot(struct idr *idp, int starting_id,
290                               struct idr_layer **pa, gfp_t gfp_mask,
291                               struct idr *layer_idr)
292 {
293         struct idr_layer *p, *new;
294         int layers, v, id;
295         unsigned long flags;
296 
297         id = starting_id;
298 build_up:
299         p = idp->top;
300         layers = idp->layers;
301         if (unlikely(!p)) {
302                 if (!(p = idr_layer_alloc(gfp_mask, layer_idr)))
303                         return -ENOMEM;
304                 p->layer = 0;
305                 layers = 1;
306         }
307         /*
308          * Add a new layer to the top of the tree if the requested
309          * id is larger than the currently allocated space.
310          */
311         while (id > idr_max(layers)) {
312                 layers++;
313                 if (!p->count) {
314                         /* special case: if the tree is currently empty,
315                          * then we grow the tree by moving the top node
316                          * upwards.
317                          */
318                         p->layer++;
319                         WARN_ON_ONCE(p->prefix);
320                         continue;
321                 }
322                 if (!(new = idr_layer_alloc(gfp_mask, layer_idr))) {
323                         /*
324                          * The allocation failed.  If we built part of
325                          * the structure tear it down.
326                          */
327                         spin_lock_irqsave(&idp->lock, flags);
328                         for (new = p; p && p != idp->top; new = p) {
329                                 p = p->ary[0];
330                                 new->ary[0] = NULL;
331                                 new->count = 0;
332                                 bitmap_clear(new->bitmap, 0, IDR_SIZE);
333                                 __move_to_free_list(idp, new);
334                         }
335                         spin_unlock_irqrestore(&idp->lock, flags);
336                         return -ENOMEM;
337                 }
338                 new->ary[0] = p;
339                 new->count = 1;
340                 new->layer = layers-1;
341                 new->prefix = id & idr_layer_prefix_mask(new->layer);
342                 if (bitmap_full(p->bitmap, IDR_SIZE))
343                         __set_bit(0, new->bitmap);
344                 p = new;
345         }
346         rcu_assign_pointer(idp->top, p);
347         idp->layers = layers;
348         v = sub_alloc(idp, &id, pa, gfp_mask, layer_idr);
349         if (v == -EAGAIN)
350                 goto build_up;
351         return(v);
352 }
353 
354 /*
355  * @id and @pa are from a successful allocation from idr_get_empty_slot().
356  * Install the user pointer @ptr and mark the slot full.
357  */
358 static void idr_fill_slot(struct idr *idr, void *ptr, int id,
359                           struct idr_layer **pa)
360 {
361         /* update hint used for lookup, cleared from free_layer() */
362         rcu_assign_pointer(idr->hint, pa[0]);
363 
364         rcu_assign_pointer(pa[0]->ary[id & IDR_MASK], (struct idr_layer *)ptr);
365         pa[0]->count++;
366         idr_mark_full(pa, id);
367 }
368 
369 
370 /**
371  * idr_preload - preload for idr_alloc()
372  * @gfp_mask: allocation mask to use for preloading
373  *
374  * Preload per-cpu layer buffer for idr_alloc().  Can only be used from
375  * process context and each idr_preload() invocation should be matched with
376  * idr_preload_end().  Note that preemption is disabled while preloaded.
377  *
378  * The first idr_alloc() in the preloaded section can be treated as if it
379  * were invoked with @gfp_mask used for preloading.  This allows using more
380  * permissive allocation masks for idrs protected by spinlocks.
381  *
382  * For example, if idr_alloc() below fails, the failure can be treated as
383  * if idr_alloc() were called with GFP_KERNEL rather than GFP_NOWAIT.
384  *
385  *      idr_preload(GFP_KERNEL);
386  *      spin_lock(lock);
387  *
388  *      id = idr_alloc(idr, ptr, start, end, GFP_NOWAIT);
389  *
390  *      spin_unlock(lock);
391  *      idr_preload_end();
392  *      if (id < 0)
393  *              error;
394  */
395 void idr_preload(gfp_t gfp_mask)
396 {
397         /*
398          * Consuming preload buffer from non-process context breaks preload
399          * allocation guarantee.  Disallow usage from those contexts.
400          */
401         WARN_ON_ONCE(in_interrupt());
402         might_sleep_if(gfpflags_allow_blocking(gfp_mask));
403 
404         preempt_disable();
405 
406         /*
407          * idr_alloc() is likely to succeed w/o full idr_layer buffer and
408          * return value from idr_alloc() needs to be checked for failure
409          * anyway.  Silently give up if allocation fails.  The caller can
410          * treat failures from idr_alloc() as if idr_alloc() were called
411          * with @gfp_mask which should be enough.
412          */
413         while (__this_cpu_read(idr_preload_cnt) < MAX_IDR_FREE) {
414                 struct idr_layer *new;
415 
416                 preempt_enable();
417                 new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
418                 preempt_disable();
419                 if (!new)
420                         break;
421 
422                 /* link the new one to per-cpu preload list */
423                 new->ary[0] = __this_cpu_read(idr_preload_head);
424                 __this_cpu_write(idr_preload_head, new);
425                 __this_cpu_inc(idr_preload_cnt);
426         }
427 }
428 EXPORT_SYMBOL(idr_preload);
429 
430 /**
431  * idr_alloc - allocate new idr entry
432  * @idr: the (initialized) idr
433  * @ptr: pointer to be associated with the new id
434  * @start: the minimum id (inclusive)
435  * @end: the maximum id (exclusive, <= 0 for max)
436  * @gfp_mask: memory allocation flags
437  *
438  * Allocate an id in [start, end) and associate it with @ptr.  If no ID is
439  * available in the specified range, returns -ENOSPC.  On memory allocation
440  * failure, returns -ENOMEM.
441  *
442  * Note that @end is treated as max when <= 0.  This is to always allow
443  * using @start + N as @end as long as N is inside integer range.
444  *
445  * The user is responsible for exclusively synchronizing all operations
446  * which may modify @idr.  However, read-only accesses such as idr_find()
447  * or iteration can be performed under RCU read lock provided the user
448  * destroys @ptr in RCU-safe way after removal from idr.
449  */
450 int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
451 {
452         int max = end > 0 ? end - 1 : INT_MAX;  /* inclusive upper limit */
453         struct idr_layer *pa[MAX_IDR_LEVEL + 1];
454         int id;
455 
456         might_sleep_if(gfpflags_allow_blocking(gfp_mask));
457 
458         /* sanity checks */
459         if (WARN_ON_ONCE(start < 0))
460                 return -EINVAL;
461         if (unlikely(max < start))
462                 return -ENOSPC;
463 
464         /* allocate id */
465         id = idr_get_empty_slot(idr, start, pa, gfp_mask, NULL);
466         if (unlikely(id < 0))
467                 return id;
468         if (unlikely(id > max))
469                 return -ENOSPC;
470 
471         idr_fill_slot(idr, ptr, id, pa);
472         return id;
473 }
474 EXPORT_SYMBOL_GPL(idr_alloc);
475 
476 /**
477  * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
478  * @idr: the (initialized) idr
479  * @ptr: pointer to be associated with the new id
480  * @start: the minimum id (inclusive)
481  * @end: the maximum id (exclusive, <= 0 for max)
482  * @gfp_mask: memory allocation flags
483  *
484  * Essentially the same as idr_alloc, but prefers to allocate progressively
485  * higher ids if it can. If the "cur" counter wraps, then it will start again
486  * at the "start" end of the range and allocate one that has already been used.
487  */
488 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,
489                         gfp_t gfp_mask)
490 {
491         int id;
492 
493         id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);
494         if (id == -ENOSPC)
495                 id = idr_alloc(idr, ptr, start, end, gfp_mask);
496 
497         if (likely(id >= 0))
498                 idr->cur = id + 1;
499         return id;
500 }
501 EXPORT_SYMBOL(idr_alloc_cyclic);
502 
503 static void idr_remove_warning(int id)
504 {
505         WARN(1, "idr_remove called for id=%d which is not allocated.\n", id);
506 }
507 
508 static void sub_remove(struct idr *idp, int shift, int id)
509 {
510         struct idr_layer *p = idp->top;
511         struct idr_layer **pa[MAX_IDR_LEVEL + 1];
512         struct idr_layer ***paa = &pa[0];
513         struct idr_layer *to_free;
514         int n;
515 
516         *paa = NULL;
517         *++paa = &idp->top;
518 
519         while ((shift > 0) && p) {
520                 n = (id >> shift) & IDR_MASK;
521                 __clear_bit(n, p->bitmap);
522                 *++paa = &p->ary[n];
523                 p = p->ary[n];
524                 shift -= IDR_BITS;
525         }
526         n = id & IDR_MASK;
527         if (likely(p != NULL && test_bit(n, p->bitmap))) {
528                 __clear_bit(n, p->bitmap);
529                 RCU_INIT_POINTER(p->ary[n], NULL);
530                 to_free = NULL;
531                 while(*paa && ! --((**paa)->count)){
532                         if (to_free)
533                                 free_layer(idp, to_free);
534                         to_free = **paa;
535                         **paa-- = NULL;
536                 }
537                 if (!*paa)
538                         idp->layers = 0;
539                 if (to_free)
540                         free_layer(idp, to_free);
541         } else
542                 idr_remove_warning(id);
543 }
544 
545 /**
546  * idr_remove - remove the given id and free its slot
547  * @idp: idr handle
548  * @id: unique key
549  */
550 void idr_remove(struct idr *idp, int id)
551 {
552         struct idr_layer *p;
553         struct idr_layer *to_free;
554 
555         if (id < 0)
556                 return;
557 
558         if (id > idr_max(idp->layers)) {
559                 idr_remove_warning(id);
560                 return;
561         }
562 
563         sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
564         if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
565             idp->top->ary[0]) {
566                 /*
567                  * Single child at leftmost slot: we can shrink the tree.
568                  * This level is not needed anymore since when layers are
569                  * inserted, they are inserted at the top of the existing
570                  * tree.
571                  */
572                 to_free = idp->top;
573                 p = idp->top->ary[0];
574                 rcu_assign_pointer(idp->top, p);
575                 --idp->layers;
576                 to_free->count = 0;
577                 bitmap_clear(to_free->bitmap, 0, IDR_SIZE);
578                 free_layer(idp, to_free);
579         }
580 }
581 EXPORT_SYMBOL(idr_remove);
582 
583 static void __idr_remove_all(struct idr *idp)
584 {
585         int n, id, max;
586         int bt_mask;
587         struct idr_layer *p;
588         struct idr_layer *pa[MAX_IDR_LEVEL + 1];
589         struct idr_layer **paa = &pa[0];
590 
591         n = idp->layers * IDR_BITS;
592         *paa = idp->top;
593         RCU_INIT_POINTER(idp->top, NULL);
594         max = idr_max(idp->layers);
595 
596         id = 0;
597         while (id >= 0 && id <= max) {
598                 p = *paa;
599                 while (n > IDR_BITS && p) {
600                         n -= IDR_BITS;
601                         p = p->ary[(id >> n) & IDR_MASK];
602                         *++paa = p;
603                 }
604 
605                 bt_mask = id;
606                 id += 1 << n;
607                 /* Get the highest bit that the above add changed from 0->1. */
608                 while (n < fls(id ^ bt_mask)) {
609                         if (*paa)
610                                 free_layer(idp, *paa);
611                         n += IDR_BITS;
612                         --paa;
613                 }
614         }
615         idp->layers = 0;
616 }
617 
618 /**
619  * idr_destroy - release all cached layers within an idr tree
620  * @idp: idr handle
621  *
622  * Free all id mappings and all idp_layers.  After this function, @idp is
623  * completely unused and can be freed / recycled.  The caller is
624  * responsible for ensuring that no one else accesses @idp during or after
625  * idr_destroy().
626  *
627  * A typical clean-up sequence for objects stored in an idr tree will use
628  * idr_for_each() to free all objects, if necessary, then idr_destroy() to
629  * free up the id mappings and cached idr_layers.
630  */
631 void idr_destroy(struct idr *idp)
632 {
633         __idr_remove_all(idp);
634 
635         while (idp->id_free_cnt) {
636                 struct idr_layer *p = get_from_free_list(idp);
637                 kmem_cache_free(idr_layer_cache, p);
638         }
639 }
640 EXPORT_SYMBOL(idr_destroy);
641 
642 void *idr_find_slowpath(struct idr *idp, int id)
643 {
644         int n;
645         struct idr_layer *p;
646 
647         if (id < 0)
648                 return NULL;
649 
650         p = rcu_dereference_raw(idp->top);
651         if (!p)
652                 return NULL;
653         n = (p->layer+1) * IDR_BITS;
654 
655         if (id > idr_max(p->layer + 1))
656                 return NULL;
657         BUG_ON(n == 0);
658 
659         while (n > 0 && p) {
660                 n -= IDR_BITS;
661                 BUG_ON(n != p->layer*IDR_BITS);
662                 p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
663         }
664         return((void *)p);
665 }
666 EXPORT_SYMBOL(idr_find_slowpath);
667 
668 /**
669  * idr_for_each - iterate through all stored pointers
670  * @idp: idr handle
671  * @fn: function to be called for each pointer
672  * @data: data passed back to callback function
673  *
674  * Iterate over the pointers registered with the given idr.  The
675  * callback function will be called for each pointer currently
676  * registered, passing the id, the pointer and the data pointer passed
677  * to this function.  It is not safe to modify the idr tree while in
678  * the callback, so functions such as idr_get_new and idr_remove are
679  * not allowed.
680  *
681  * We check the return of @fn each time. If it returns anything other
682  * than %0, we break out and return that value.
683  *
684  * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
685  */
686 int idr_for_each(struct idr *idp,
687                  int (*fn)(int id, void *p, void *data), void *data)
688 {
689         int n, id, max, error = 0;
690         struct idr_layer *p;
691         struct idr_layer *pa[MAX_IDR_LEVEL + 1];
692         struct idr_layer **paa = &pa[0];
693 
694         n = idp->layers * IDR_BITS;
695         *paa = rcu_dereference_raw(idp->top);
696         max = idr_max(idp->layers);
697 
698         id = 0;
699         while (id >= 0 && id <= max) {
700                 p = *paa;
701                 while (n > 0 && p) {
702                         n -= IDR_BITS;
703                         p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
704                         *++paa = p;
705                 }
706 
707                 if (p) {
708                         error = fn(id, (void *)p, data);
709                         if (error)
710                                 break;
711                 }
712 
713                 id += 1 << n;
714                 while (n < fls(id)) {
715                         n += IDR_BITS;
716                         --paa;
717                 }
718         }
719 
720         return error;
721 }
722 EXPORT_SYMBOL(idr_for_each);
723 
724 /**
725  * idr_get_next - lookup next object of id to given id.
726  * @idp: idr handle
727  * @nextidp:  pointer to lookup key
728  *
729  * Returns pointer to registered object with id, which is next number to
730  * given id. After being looked up, *@nextidp will be updated for the next
731  * iteration.
732  *
733  * This function can be called under rcu_read_lock(), given that the leaf
734  * pointers lifetimes are correctly managed.
735  */
736 void *idr_get_next(struct idr *idp, int *nextidp)
737 {
738         struct idr_layer *p, *pa[MAX_IDR_LEVEL + 1];
739         struct idr_layer **paa = &pa[0];
740         int id = *nextidp;
741         int n, max;
742 
743         /* find first ent */
744         p = *paa = rcu_dereference_raw(idp->top);
745         if (!p)
746                 return NULL;
747         n = (p->layer + 1) * IDR_BITS;
748         max = idr_max(p->layer + 1);
749 
750         while (id >= 0 && id <= max) {
751                 p = *paa;
752                 while (n > 0 && p) {
753                         n -= IDR_BITS;
754                         p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
755                         *++paa = p;
756                 }
757 
758                 if (p) {
759                         *nextidp = id;
760                         return p;
761                 }
762 
763                 /*
764                  * Proceed to the next layer at the current level.  Unlike
765                  * idr_for_each(), @id isn't guaranteed to be aligned to
766                  * layer boundary at this point and adding 1 << n may
767                  * incorrectly skip IDs.  Make sure we jump to the
768                  * beginning of the next layer using round_up().
769                  */
770                 id = round_up(id + 1, 1 << n);
771                 while (n < fls(id)) {
772                         n += IDR_BITS;
773                         --paa;
774                 }
775         }
776         return NULL;
777 }
778 EXPORT_SYMBOL(idr_get_next);
779 
780 
781 /**
782  * idr_replace - replace pointer for given id
783  * @idp: idr handle
784  * @ptr: pointer you want associated with the id
785  * @id: lookup key
786  *
787  * Replace the pointer registered with an id and return the old value.
788  * A %-ENOENT return indicates that @id was not found.
789  * A %-EINVAL return indicates that @id was not within valid constraints.
790  *
791  * The caller must serialize with writers.
792  */
793 void *idr_replace(struct idr *idp, void *ptr, int id)
794 {
795         int n;
796         struct idr_layer *p, *old_p;
797 
798         if (id < 0)
799                 return ERR_PTR(-EINVAL);
800 
801         p = idp->top;
802         if (!p)
803                 return ERR_PTR(-ENOENT);
804 
805         if (id > idr_max(p->layer + 1))
806                 return ERR_PTR(-ENOENT);
807 
808         n = p->layer * IDR_BITS;
809         while ((n > 0) && p) {
810                 p = p->ary[(id >> n) & IDR_MASK];
811                 n -= IDR_BITS;
812         }
813 
814         n = id & IDR_MASK;
815         if (unlikely(p == NULL || !test_bit(n, p->bitmap)))
816                 return ERR_PTR(-ENOENT);
817 
818         old_p = p->ary[n];
819         rcu_assign_pointer(p->ary[n], ptr);
820 
821         return old_p;
822 }
823 EXPORT_SYMBOL(idr_replace);
824 
825 void __init idr_init_cache(void)
826 {
827         idr_layer_cache = kmem_cache_create("idr_layer_cache",
828                                 sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
829 }
830 
831 /**
832  * idr_init - initialize idr handle
833  * @idp:        idr handle
834  *
835  * This function is use to set up the handle (@idp) that you will pass
836  * to the rest of the functions.
837  */
838 void idr_init(struct idr *idp)
839 {
840         memset(idp, 0, sizeof(struct idr));
841         spin_lock_init(&idp->lock);
842 }
843 EXPORT_SYMBOL(idr_init);
844 
845 static int idr_has_entry(int id, void *p, void *data)
846 {
847         return 1;
848 }
849 
850 bool idr_is_empty(struct idr *idp)
851 {
852         return !idr_for_each(idp, idr_has_entry, NULL);
853 }
854 EXPORT_SYMBOL(idr_is_empty);
855 
856 /**
857  * DOC: IDA description
858  * IDA - IDR based ID allocator
859  *
860  * This is id allocator without id -> pointer translation.  Memory
861  * usage is much lower than full blown idr because each id only
862  * occupies a bit.  ida uses a custom leaf node which contains
863  * IDA_BITMAP_BITS slots.
864  *
865  * 2007-04-25  written by Tejun Heo <htejun@gmail.com>
866  */
867 
868 static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
869 {
870         unsigned long flags;
871 
872         if (!ida->free_bitmap) {
873                 spin_lock_irqsave(&ida->idr.lock, flags);
874                 if (!ida->free_bitmap) {
875                         ida->free_bitmap = bitmap;
876                         bitmap = NULL;
877                 }
878                 spin_unlock_irqrestore(&ida->idr.lock, flags);
879         }
880 
881         kfree(bitmap);
882 }
883 
884 /**
885  * ida_pre_get - reserve resources for ida allocation
886  * @ida:        ida handle
887  * @gfp_mask:   memory allocation flag
888  *
889  * This function should be called prior to locking and calling the
890  * following function.  It preallocates enough memory to satisfy the
891  * worst possible allocation.
892  *
893  * If the system is REALLY out of memory this function returns %0,
894  * otherwise %1.
895  */
896 int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
897 {
898         /* allocate idr_layers */
899         if (!__idr_pre_get(&ida->idr, gfp_mask))
900                 return 0;
901 
902         /* allocate free_bitmap */
903         if (!ida->free_bitmap) {
904                 struct ida_bitmap *bitmap;
905 
906                 bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
907                 if (!bitmap)
908                         return 0;
909 
910                 free_bitmap(ida, bitmap);
911         }
912 
913         return 1;
914 }
915 EXPORT_SYMBOL(ida_pre_get);
916 
917 /**
918  * ida_get_new_above - allocate new ID above or equal to a start id
919  * @ida:        ida handle
920  * @starting_id: id to start search at
921  * @p_id:       pointer to the allocated handle
922  *
923  * Allocate new ID above or equal to @starting_id.  It should be called
924  * with any required locks.
925  *
926  * If memory is required, it will return %-EAGAIN, you should unlock
927  * and go back to the ida_pre_get() call.  If the ida is full, it will
928  * return %-ENOSPC.
929  *
930  * Note that callers must ensure that concurrent access to @ida is not possible.
931  * See ida_simple_get() for a varaint which takes care of locking.
932  *
933  * @p_id returns a value in the range @starting_id ... %0x7fffffff.
934  */
935 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
936 {
937         struct idr_layer *pa[MAX_IDR_LEVEL + 1];
938         struct ida_bitmap *bitmap;
939         unsigned long flags;
940         int idr_id = starting_id / IDA_BITMAP_BITS;
941         int offset = starting_id % IDA_BITMAP_BITS;
942         int t, id;
943 
944  restart:
945         /* get vacant slot */
946         t = idr_get_empty_slot(&ida->idr, idr_id, pa, 0, &ida->idr);
947         if (t < 0)
948                 return t == -ENOMEM ? -EAGAIN : t;
949 
950         if (t * IDA_BITMAP_BITS >= MAX_IDR_BIT)
951                 return -ENOSPC;
952 
953         if (t != idr_id)
954                 offset = 0;
955         idr_id = t;
956 
957         /* if bitmap isn't there, create a new one */
958         bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
959         if (!bitmap) {
960                 spin_lock_irqsave(&ida->idr.lock, flags);
961                 bitmap = ida->free_bitmap;
962                 ida->free_bitmap = NULL;
963                 spin_unlock_irqrestore(&ida->idr.lock, flags);
964 
965                 if (!bitmap)
966                         return -EAGAIN;
967 
968                 memset(bitmap, 0, sizeof(struct ida_bitmap));
969                 rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
970                                 (void *)bitmap);
971                 pa[0]->count++;
972         }
973 
974         /* lookup for empty slot */
975         t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
976         if (t == IDA_BITMAP_BITS) {
977                 /* no empty slot after offset, continue to the next chunk */
978                 idr_id++;
979                 offset = 0;
980                 goto restart;
981         }
982 
983         id = idr_id * IDA_BITMAP_BITS + t;
984         if (id >= MAX_IDR_BIT)
985                 return -ENOSPC;
986 
987         __set_bit(t, bitmap->bitmap);
988         if (++bitmap->nr_busy == IDA_BITMAP_BITS)
989                 idr_mark_full(pa, idr_id);
990 
991         *p_id = id;
992 
993         /* Each leaf node can handle nearly a thousand slots and the
994          * whole idea of ida is to have small memory foot print.
995          * Throw away extra resources one by one after each successful
996          * allocation.
997          */
998         if (ida->idr.id_free_cnt || ida->free_bitmap) {
999                 struct idr_layer *p = get_from_free_list(&ida->idr);
1000                 if (p)
1001                         kmem_cache_free(idr_layer_cache, p);
1002         }
1003 
1004         return 0;
1005 }
1006 EXPORT_SYMBOL(ida_get_new_above);
1007 
1008 /**
1009  * ida_remove - remove the given ID
1010  * @ida:        ida handle
1011  * @id:         ID to free
1012  */
1013 void ida_remove(struct ida *ida, int id)
1014 {
1015         struct idr_layer *p = ida->idr.top;
1016         int shift = (ida->idr.layers - 1) * IDR_BITS;
1017         int idr_id = id / IDA_BITMAP_BITS;
1018         int offset = id % IDA_BITMAP_BITS;
1019         int n;
1020         struct ida_bitmap *bitmap;
1021 
1022         if (idr_id > idr_max(ida->idr.layers))
1023                 goto err;
1024 
1025         /* clear full bits while looking up the leaf idr_layer */
1026         while ((shift > 0) && p) {
1027                 n = (idr_id >> shift) & IDR_MASK;
1028                 __clear_bit(n, p->bitmap);
1029                 p = p->ary[n];
1030                 shift -= IDR_BITS;
1031         }
1032 
1033         if (p == NULL)
1034                 goto err;
1035 
1036         n = idr_id & IDR_MASK;
1037         __clear_bit(n, p->bitmap);
1038 
1039         bitmap = (void *)p->ary[n];
1040         if (!bitmap || !test_bit(offset, bitmap->bitmap))
1041                 goto err;
1042 
1043         /* update bitmap and remove it if empty */
1044         __clear_bit(offset, bitmap->bitmap);
1045         if (--bitmap->nr_busy == 0) {
1046                 __set_bit(n, p->bitmap);        /* to please idr_remove() */
1047                 idr_remove(&ida->idr, idr_id);
1048                 free_bitmap(ida, bitmap);
1049         }
1050 
1051         return;
1052 
1053  err:
1054         WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
1055 }
1056 EXPORT_SYMBOL(ida_remove);
1057 
1058 /**
1059  * ida_destroy - release all cached layers within an ida tree
1060  * @ida:                ida handle
1061  */
1062 void ida_destroy(struct ida *ida)
1063 {
1064         idr_destroy(&ida->idr);
1065         kfree(ida->free_bitmap);
1066 }
1067 EXPORT_SYMBOL(ida_destroy);
1068 
1069 /**
1070  * ida_simple_get - get a new id.
1071  * @ida: the (initialized) ida.
1072  * @start: the minimum id (inclusive, < 0x8000000)
1073  * @end: the maximum id (exclusive, < 0x8000000 or 0)
1074  * @gfp_mask: memory allocation flags
1075  *
1076  * Allocates an id in the range start <= id < end, or returns -ENOSPC.
1077  * On memory allocation failure, returns -ENOMEM.
1078  *
1079  * Compared to ida_get_new_above() this function does its own locking, and
1080  * should be used unless there are special requirements.
1081  *
1082  * Use ida_simple_remove() to get rid of an id.
1083  */
1084 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
1085                    gfp_t gfp_mask)
1086 {
1087         int ret, id;
1088         unsigned int max;
1089         unsigned long flags;
1090 
1091         BUG_ON((int)start < 0);
1092         BUG_ON((int)end < 0);
1093 
1094         if (end == 0)
1095                 max = 0x80000000;
1096         else {
1097                 BUG_ON(end < start);
1098                 max = end - 1;
1099         }
1100 
1101 again:
1102         if (!ida_pre_get(ida, gfp_mask))
1103                 return -ENOMEM;
1104 
1105         spin_lock_irqsave(&simple_ida_lock, flags);
1106         ret = ida_get_new_above(ida, start, &id);
1107         if (!ret) {
1108                 if (id > max) {
1109                         ida_remove(ida, id);
1110                         ret = -ENOSPC;
1111                 } else {
1112                         ret = id;
1113                 }
1114         }
1115         spin_unlock_irqrestore(&simple_ida_lock, flags);
1116 
1117         if (unlikely(ret == -EAGAIN))
1118                 goto again;
1119 
1120         return ret;
1121 }
1122 EXPORT_SYMBOL(ida_simple_get);
1123 
1124 /**
1125  * ida_simple_remove - remove an allocated id.
1126  * @ida: the (initialized) ida.
1127  * @id: the id returned by ida_simple_get.
1128  *
1129  * Use to release an id allocated with ida_simple_get().
1130  *
1131  * Compared to ida_remove() this function does its own locking, and should be
1132  * used unless there are special requirements.
1133  */
1134 void ida_simple_remove(struct ida *ida, unsigned int id)
1135 {
1136         unsigned long flags;
1137 
1138         BUG_ON((int)id < 0);
1139         spin_lock_irqsave(&simple_ida_lock, flags);
1140         ida_remove(ida, id);
1141         spin_unlock_irqrestore(&simple_ida_lock, flags);
1142 }
1143 EXPORT_SYMBOL(ida_simple_remove);
1144 
1145 /**
1146  * ida_init - initialize ida handle
1147  * @ida:        ida handle
1148  *
1149  * This function is use to set up the handle (@ida) that you will pass
1150  * to the rest of the functions.
1151  */
1152 void ida_init(struct ida *ida)
1153 {
1154         memset(ida, 0, sizeof(struct ida));
1155         idr_init(&ida->idr);
1156 
1157 }
1158 EXPORT_SYMBOL(ida_init);
1159 

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us