Root/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 * 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.
27 */
28
29#ifndef TEST // to test in user space...
30#include <linux/slab.h>
31#include <linux/init.h>
32#include <linux/module.h>
33#endif
34#include <linux/err.h>
35#include <linux/string.h>
36#include <linux/idr.h>
37
38static struct kmem_cache *idr_layer_cache;
39
40static struct idr_layer *get_from_free_list(struct idr *idp)
41{
42    struct idr_layer *p;
43    unsigned long flags;
44
45    spin_lock_irqsave(&idp->lock, flags);
46    if ((p = idp->id_free)) {
47        idp->id_free = p->ary[0];
48        idp->id_free_cnt--;
49        p->ary[0] = NULL;
50    }
51    spin_unlock_irqrestore(&idp->lock, flags);
52    return(p);
53}
54
55static void idr_layer_rcu_free(struct rcu_head *head)
56{
57    struct idr_layer *layer;
58
59    layer = container_of(head, struct idr_layer, rcu_head);
60    kmem_cache_free(idr_layer_cache, layer);
61}
62
63static inline void free_layer(struct idr_layer *p)
64{
65    call_rcu(&p->rcu_head, idr_layer_rcu_free);
66}
67
68/* only called when idp->lock is held */
69static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
70{
71    p->ary[0] = idp->id_free;
72    idp->id_free = p;
73    idp->id_free_cnt++;
74}
75
76static void move_to_free_list(struct idr *idp, struct idr_layer *p)
77{
78    unsigned long flags;
79
80    /*
81     * Depends on the return element being zeroed.
82     */
83    spin_lock_irqsave(&idp->lock, flags);
84    __move_to_free_list(idp, p);
85    spin_unlock_irqrestore(&idp->lock, flags);
86}
87
88static void idr_mark_full(struct idr_layer **pa, int id)
89{
90    struct idr_layer *p = pa[0];
91    int l = 0;
92
93    __set_bit(id & IDR_MASK, &p->bitmap);
94    /*
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
98     * tree.
99     */
100    while (p->bitmap == IDR_FULL) {
101        if (!(p = pa[++l]))
102            break;
103        id = id >> IDR_BITS;
104        __set_bit((id & IDR_MASK), &p->bitmap);
105    }
106}
107
108/**
109 * idr_pre_get - reserver resources for idr allocation
110 * @idp: idr handle
111 * @gfp_mask: memory allocation flags
112 *
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.
116 *
117 * If the system is REALLY out of memory this function returns 0,
118 * otherwise 1.
119 */
120int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
121{
122    while (idp->id_free_cnt < IDR_FREE_MAX) {
123        struct idr_layer *new;
124        new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
125        if (new == NULL)
126            return (0);
127        move_to_free_list(idp, new);
128    }
129    return 1;
130}
131EXPORT_SYMBOL(idr_pre_get);
132
133static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
134{
135    int n, m, sh;
136    struct idr_layer *p, *new;
137    int l, id, oid;
138    unsigned long bm;
139
140    id = *starting_id;
141 restart:
142    p = idp->top;
143    l = idp->layers;
144    pa[l--] = NULL;
145    while (1) {
146        /*
147         * We run around this while until we reach the leaf node...
148         */
149        n = (id >> (IDR_BITS*l)) & IDR_MASK;
150        bm = ~p->bitmap;
151        m = find_next_bit(&bm, IDR_SIZE, n);
152        if (m == IDR_SIZE) {
153            /* no space available go back to previous layer. */
154            l++;
155            oid = id;
156            id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
157
158            /* if already at the top layer, we need to grow */
159            if (id >= 1 << (idp->layers * IDR_BITS)) {
160                *starting_id = id;
161                return IDR_NEED_TO_GROW;
162            }
163            p = pa[l];
164            BUG_ON(!p);
165
166            /* If we need to go up one layer, continue the
167             * loop; otherwise, restart from the top.
168             */
169            sh = IDR_BITS * (l + 1);
170            if (oid >> sh == id >> sh)
171                continue;
172            else
173                goto restart;
174        }
175        if (m != n) {
176            sh = IDR_BITS*l;
177            id = ((id >> sh) ^ n ^ m) << sh;
178        }
179        if ((id >= MAX_ID_BIT) || (id < 0))
180            return IDR_NOMORE_SPACE;
181        if (l == 0)
182            break;
183        /*
184         * Create the layer below if it is missing.
185         */
186        if (!p->ary[m]) {
187            new = get_from_free_list(idp);
188            if (!new)
189                return -1;
190            new->layer = l-1;
191            rcu_assign_pointer(p->ary[m], new);
192            p->count++;
193        }
194        pa[l--] = p;
195        p = p->ary[m];
196    }
197
198    pa[l] = p;
199    return id;
200}
201
202static int idr_get_empty_slot(struct idr *idp, int starting_id,
203                  struct idr_layer **pa)
204{
205    struct idr_layer *p, *new;
206    int layers, v, id;
207    unsigned long flags;
208
209    id = starting_id;
210build_up:
211    p = idp->top;
212    layers = idp->layers;
213    if (unlikely(!p)) {
214        if (!(p = get_from_free_list(idp)))
215            return -1;
216        p->layer = 0;
217        layers = 1;
218    }
219    /*
220     * Add a new layer to the top of the tree if the requested
221     * id is larger than the currently allocated space.
222     */
223    while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
224        layers++;
225        if (!p->count) {
226            /* special case: if the tree is currently empty,
227             * then we grow the tree by moving the top node
228             * upwards.
229             */
230            p->layer++;
231            continue;
232        }
233        if (!(new = get_from_free_list(idp))) {
234            /*
235             * The allocation failed. If we built part of
236             * the structure tear it down.
237             */
238            spin_lock_irqsave(&idp->lock, flags);
239            for (new = p; p && p != idp->top; new = p) {
240                p = p->ary[0];
241                new->ary[0] = NULL;
242                new->bitmap = new->count = 0;
243                __move_to_free_list(idp, new);
244            }
245            spin_unlock_irqrestore(&idp->lock, flags);
246            return -1;
247        }
248        new->ary[0] = p;
249        new->count = 1;
250        new->layer = layers-1;
251        if (p->bitmap == IDR_FULL)
252            __set_bit(0, &new->bitmap);
253        p = new;
254    }
255    rcu_assign_pointer(idp->top, p);
256    idp->layers = layers;
257    v = sub_alloc(idp, &id, pa);
258    if (v == IDR_NEED_TO_GROW)
259        goto build_up;
260    return(v);
261}
262
263static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
264{
265    struct idr_layer *pa[MAX_LEVEL];
266    int id;
267
268    id = idr_get_empty_slot(idp, starting_id, pa);
269    if (id >= 0) {
270        /*
271         * Successfully found an empty slot. Install the user
272         * pointer and mark the slot full.
273         */
274        rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
275                (struct idr_layer *)ptr);
276        pa[0]->count++;
277        idr_mark_full(pa, id);
278    }
279
280    return id;
281}
282
283/**
284 * idr_get_new_above - allocate new idr entry above or equal to a start id
285 * @idp: idr handle
286 * @ptr: pointer you want associated with the id
287 * @start_id: id to start search at
288 * @id: pointer to the allocated handle
289 *
290 * This is the allocate id function. It should be called with any
291 * required locks.
292 *
293 * If memory is required, it will return -EAGAIN, you should unlock
294 * and go back to the idr_pre_get() call. If the idr is full, it will
295 * return -ENOSPC.
296 *
297 * @id returns a value in the range @starting_id ... 0x7fffffff
298 */
299int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
300{
301    int rv;
302
303    rv = idr_get_new_above_int(idp, ptr, starting_id);
304    /*
305     * This is a cheap hack until the IDR code can be fixed to
306     * return proper error values.
307     */
308    if (rv < 0)
309        return _idr_rc_to_errno(rv);
310    *id = rv;
311    return 0;
312}
313EXPORT_SYMBOL(idr_get_new_above);
314
315/**
316 * idr_get_new - allocate new idr entry
317 * @idp: idr handle
318 * @ptr: pointer you want associated with the id
319 * @id: pointer to the allocated handle
320 *
321 * This is the allocate id function. It should be called with any
322 * required locks.
323 *
324 * If memory is required, it will return -EAGAIN, you should unlock
325 * and go back to the idr_pre_get() call. If the idr is full, it will
326 * return -ENOSPC.
327 *
328 * @id returns a value in the range 0 ... 0x7fffffff
329 */
330int idr_get_new(struct idr *idp, void *ptr, int *id)
331{
332    int rv;
333
334    rv = idr_get_new_above_int(idp, ptr, 0);
335    /*
336     * This is a cheap hack until the IDR code can be fixed to
337     * return proper error values.
338     */
339    if (rv < 0)
340        return _idr_rc_to_errno(rv);
341    *id = rv;
342    return 0;
343}
344EXPORT_SYMBOL(idr_get_new);
345
346static void idr_remove_warning(int id)
347{
348    printk(KERN_WARNING
349        "idr_remove called for id=%d which is not allocated.\n", id);
350    dump_stack();
351}
352
353static void sub_remove(struct idr *idp, int shift, int id)
354{
355    struct idr_layer *p = idp->top;
356    struct idr_layer **pa[MAX_LEVEL];
357    struct idr_layer ***paa = &pa[0];
358    struct idr_layer *to_free;
359    int n;
360
361    *paa = NULL;
362    *++paa = &idp->top;
363
364    while ((shift > 0) && p) {
365        n = (id >> shift) & IDR_MASK;
366        __clear_bit(n, &p->bitmap);
367        *++paa = &p->ary[n];
368        p = p->ary[n];
369        shift -= IDR_BITS;
370    }
371    n = id & IDR_MASK;
372    if (likely(p != NULL && test_bit(n, &p->bitmap))){
373        __clear_bit(n, &p->bitmap);
374        rcu_assign_pointer(p->ary[n], NULL);
375        to_free = NULL;
376        while(*paa && ! --((**paa)->count)){
377            if (to_free)
378                free_layer(to_free);
379            to_free = **paa;
380            **paa-- = NULL;
381        }
382        if (!*paa)
383            idp->layers = 0;
384        if (to_free)
385            free_layer(to_free);
386    } else
387        idr_remove_warning(id);
388}
389
390/**
391 * idr_remove - remove the given id and free it's slot
392 * @idp: idr handle
393 * @id: unique key
394 */
395void idr_remove(struct idr *idp, int id)
396{
397    struct idr_layer *p;
398    struct idr_layer *to_free;
399
400    /* Mask off upper bits we don't use for the search. */
401    id &= MAX_ID_MASK;
402
403    sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
404    if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
405        idp->top->ary[0]) {
406        /*
407         * Single child at leftmost slot: we can shrink the tree.
408         * This level is not needed anymore since when layers are
409         * inserted, they are inserted at the top of the existing
410         * tree.
411         */
412        to_free = idp->top;
413        p = idp->top->ary[0];
414        rcu_assign_pointer(idp->top, p);
415        --idp->layers;
416        to_free->bitmap = to_free->count = 0;
417        free_layer(to_free);
418    }
419    while (idp->id_free_cnt >= IDR_FREE_MAX) {
420        p = get_from_free_list(idp);
421        /*
422         * Note: we don't call the rcu callback here, since the only
423         * layers that fall into the freelist are those that have been
424         * preallocated.
425         */
426        kmem_cache_free(idr_layer_cache, p);
427    }
428    return;
429}
430EXPORT_SYMBOL(idr_remove);
431
432/**
433 * idr_remove_all - remove all ids from the given idr tree
434 * @idp: idr handle
435 *
436 * idr_destroy() only frees up unused, cached idp_layers, but this
437 * function will remove all id mappings and leave all idp_layers
438 * unused.
439 *
440 * A typical clean-up sequence for objects stored in an idr tree, will
441 * use idr_for_each() to free all objects, if necessay, then
442 * idr_remove_all() to remove all ids, and idr_destroy() to free
443 * up the cached idr_layers.
444 */
445void idr_remove_all(struct idr *idp)
446{
447    int n, id, max;
448    int bt_mask;
449    struct idr_layer *p;
450    struct idr_layer *pa[MAX_LEVEL];
451    struct idr_layer **paa = &pa[0];
452
453    n = idp->layers * IDR_BITS;
454    p = idp->top;
455    rcu_assign_pointer(idp->top, NULL);
456    max = 1 << n;
457
458    id = 0;
459    while (id < max) {
460        while (n > IDR_BITS && p) {
461            n -= IDR_BITS;
462            *paa++ = p;
463            p = p->ary[(id >> n) & IDR_MASK];
464        }
465
466        bt_mask = id;
467        id += 1 << n;
468        /* Get the highest bit that the above add changed from 0->1. */
469        while (n < fls(id ^ bt_mask)) {
470            if (p)
471                free_layer(p);
472            n += IDR_BITS;
473            p = *--paa;
474        }
475    }
476    idp->layers = 0;
477}
478EXPORT_SYMBOL(idr_remove_all);
479
480/**
481 * idr_destroy - release all cached layers within an idr tree
482 * idp: idr handle
483 */
484void idr_destroy(struct idr *idp)
485{
486    while (idp->id_free_cnt) {
487        struct idr_layer *p = get_from_free_list(idp);
488        kmem_cache_free(idr_layer_cache, p);
489    }
490}
491EXPORT_SYMBOL(idr_destroy);
492
493/**
494 * idr_find - return pointer for given id
495 * @idp: idr handle
496 * @id: lookup key
497 *
498 * Return the pointer given the id it has been registered with. A %NULL
499 * return indicates that @id is not valid or you passed %NULL in
500 * idr_get_new().
501 *
502 * This function can be called under rcu_read_lock(), given that the leaf
503 * pointers lifetimes are correctly managed.
504 */
505void *idr_find(struct idr *idp, int id)
506{
507    int n;
508    struct idr_layer *p;
509
510    p = rcu_dereference_raw(idp->top);
511    if (!p)
512        return NULL;
513    n = (p->layer+1) * IDR_BITS;
514
515    /* Mask off upper bits we don't use for the search. */
516    id &= MAX_ID_MASK;
517
518    if (id >= (1 << n))
519        return NULL;
520    BUG_ON(n == 0);
521
522    while (n > 0 && p) {
523        n -= IDR_BITS;
524        BUG_ON(n != p->layer*IDR_BITS);
525        p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
526    }
527    return((void *)p);
528}
529EXPORT_SYMBOL(idr_find);
530
531/**
532 * idr_for_each - iterate through all stored pointers
533 * @idp: idr handle
534 * @fn: function to be called for each pointer
535 * @data: data passed back to callback function
536 *
537 * Iterate over the pointers registered with the given idr. The
538 * callback function will be called for each pointer currently
539 * registered, passing the id, the pointer and the data pointer passed
540 * to this function. It is not safe to modify the idr tree while in
541 * the callback, so functions such as idr_get_new and idr_remove are
542 * not allowed.
543 *
544 * We check the return of @fn each time. If it returns anything other
545 * than 0, we break out and return that value.
546 *
547 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
548 */
549int idr_for_each(struct idr *idp,
550         int (*fn)(int id, void *p, void *data), void *data)
551{
552    int n, id, max, error = 0;
553    struct idr_layer *p;
554    struct idr_layer *pa[MAX_LEVEL];
555    struct idr_layer **paa = &pa[0];
556
557    n = idp->layers * IDR_BITS;
558    p = rcu_dereference_raw(idp->top);
559    max = 1 << n;
560
561    id = 0;
562    while (id < max) {
563        while (n > 0 && p) {
564            n -= IDR_BITS;
565            *paa++ = p;
566            p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
567        }
568
569        if (p) {
570            error = fn(id, (void *)p, data);
571            if (error)
572                break;
573        }
574
575        id += 1 << n;
576        while (n < fls(id)) {
577            n += IDR_BITS;
578            p = *--paa;
579        }
580    }
581
582    return error;
583}
584EXPORT_SYMBOL(idr_for_each);
585
586/**
587 * idr_get_next - lookup next object of id to given id.
588 * @idp: idr handle
589 * @id: pointer to lookup key
590 *
591 * Returns pointer to registered object with id, which is next number to
592 * given id.
593 */
594
595void *idr_get_next(struct idr *idp, int *nextidp)
596{
597    struct idr_layer *p, *pa[MAX_LEVEL];
598    struct idr_layer **paa = &pa[0];
599    int id = *nextidp;
600    int n, max;
601
602    /* find first ent */
603    n = idp->layers * IDR_BITS;
604    max = 1 << n;
605    p = rcu_dereference_raw(idp->top);
606    if (!p)
607        return NULL;
608
609    while (id < max) {
610        while (n > 0 && p) {
611            n -= IDR_BITS;
612            *paa++ = p;
613            p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
614        }
615
616        if (p) {
617            *nextidp = id;
618            return p;
619        }
620
621        id += 1 << n;
622        while (n < fls(id)) {
623            n += IDR_BITS;
624            p = *--paa;
625        }
626    }
627    return NULL;
628}
629EXPORT_SYMBOL(idr_get_next);
630
631
632/**
633 * idr_replace - replace pointer for given id
634 * @idp: idr handle
635 * @ptr: pointer you want associated with the id
636 * @id: lookup key
637 *
638 * Replace the pointer registered with an id and return the old value.
639 * A -ENOENT return indicates that @id was not found.
640 * A -EINVAL return indicates that @id was not within valid constraints.
641 *
642 * The caller must serialize with writers.
643 */
644void *idr_replace(struct idr *idp, void *ptr, int id)
645{
646    int n;
647    struct idr_layer *p, *old_p;
648
649    p = idp->top;
650    if (!p)
651        return ERR_PTR(-EINVAL);
652
653    n = (p->layer+1) * IDR_BITS;
654
655    id &= MAX_ID_MASK;
656
657    if (id >= (1 << n))
658        return ERR_PTR(-EINVAL);
659
660    n -= IDR_BITS;
661    while ((n > 0) && p) {
662        p = p->ary[(id >> n) & IDR_MASK];
663        n -= IDR_BITS;
664    }
665
666    n = id & IDR_MASK;
667    if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
668        return ERR_PTR(-ENOENT);
669
670    old_p = p->ary[n];
671    rcu_assign_pointer(p->ary[n], ptr);
672
673    return old_p;
674}
675EXPORT_SYMBOL(idr_replace);
676
677void __init idr_init_cache(void)
678{
679    idr_layer_cache = kmem_cache_create("idr_layer_cache",
680                sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
681}
682
683/**
684 * idr_init - initialize idr handle
685 * @idp: idr handle
686 *
687 * This function is use to set up the handle (@idp) that you will pass
688 * to the rest of the functions.
689 */
690void idr_init(struct idr *idp)
691{
692    memset(idp, 0, sizeof(struct idr));
693    spin_lock_init(&idp->lock);
694}
695EXPORT_SYMBOL(idr_init);
696
697
698/*
699 * IDA - IDR based ID allocator
700 *
701 * this is id allocator without id -> pointer translation. Memory
702 * usage is much lower than full blown idr because each id only
703 * occupies a bit. ida uses a custom leaf node which contains
704 * IDA_BITMAP_BITS slots.
705 *
706 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
707 */
708
709static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
710{
711    unsigned long flags;
712
713    if (!ida->free_bitmap) {
714        spin_lock_irqsave(&ida->idr.lock, flags);
715        if (!ida->free_bitmap) {
716            ida->free_bitmap = bitmap;
717            bitmap = NULL;
718        }
719        spin_unlock_irqrestore(&ida->idr.lock, flags);
720    }
721
722    kfree(bitmap);
723}
724
725/**
726 * ida_pre_get - reserve resources for ida allocation
727 * @ida: ida handle
728 * @gfp_mask: memory allocation flag
729 *
730 * This function should be called prior to locking and calling the
731 * following function. It preallocates enough memory to satisfy the
732 * worst possible allocation.
733 *
734 * If the system is REALLY out of memory this function returns 0,
735 * otherwise 1.
736 */
737int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
738{
739    /* allocate idr_layers */
740    if (!idr_pre_get(&ida->idr, gfp_mask))
741        return 0;
742
743    /* allocate free_bitmap */
744    if (!ida->free_bitmap) {
745        struct ida_bitmap *bitmap;
746
747        bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
748        if (!bitmap)
749            return 0;
750
751        free_bitmap(ida, bitmap);
752    }
753
754    return 1;
755}
756EXPORT_SYMBOL(ida_pre_get);
757
758/**
759 * ida_get_new_above - allocate new ID above or equal to a start id
760 * @ida: ida handle
761 * @staring_id: id to start search at
762 * @p_id: pointer to the allocated handle
763 *
764 * Allocate new ID above or equal to @ida. It should be called with
765 * any required locks.
766 *
767 * If memory is required, it will return -EAGAIN, you should unlock
768 * and go back to the ida_pre_get() call. If the ida is full, it will
769 * return -ENOSPC.
770 *
771 * @p_id returns a value in the range @starting_id ... 0x7fffffff.
772 */
773int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
774{
775    struct idr_layer *pa[MAX_LEVEL];
776    struct ida_bitmap *bitmap;
777    unsigned long flags;
778    int idr_id = starting_id / IDA_BITMAP_BITS;
779    int offset = starting_id % IDA_BITMAP_BITS;
780    int t, id;
781
782 restart:
783    /* get vacant slot */
784    t = idr_get_empty_slot(&ida->idr, idr_id, pa);
785    if (t < 0)
786        return _idr_rc_to_errno(t);
787
788    if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
789        return -ENOSPC;
790
791    if (t != idr_id)
792        offset = 0;
793    idr_id = t;
794
795    /* if bitmap isn't there, create a new one */
796    bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
797    if (!bitmap) {
798        spin_lock_irqsave(&ida->idr.lock, flags);
799        bitmap = ida->free_bitmap;
800        ida->free_bitmap = NULL;
801        spin_unlock_irqrestore(&ida->idr.lock, flags);
802
803        if (!bitmap)
804            return -EAGAIN;
805
806        memset(bitmap, 0, sizeof(struct ida_bitmap));
807        rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
808                (void *)bitmap);
809        pa[0]->count++;
810    }
811
812    /* lookup for empty slot */
813    t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
814    if (t == IDA_BITMAP_BITS) {
815        /* no empty slot after offset, continue to the next chunk */
816        idr_id++;
817        offset = 0;
818        goto restart;
819    }
820
821    id = idr_id * IDA_BITMAP_BITS + t;
822    if (id >= MAX_ID_BIT)
823        return -ENOSPC;
824
825    __set_bit(t, bitmap->bitmap);
826    if (++bitmap->nr_busy == IDA_BITMAP_BITS)
827        idr_mark_full(pa, idr_id);
828
829    *p_id = id;
830
831    /* Each leaf node can handle nearly a thousand slots and the
832     * whole idea of ida is to have small memory foot print.
833     * Throw away extra resources one by one after each successful
834     * allocation.
835     */
836    if (ida->idr.id_free_cnt || ida->free_bitmap) {
837        struct idr_layer *p = get_from_free_list(&ida->idr);
838        if (p)
839            kmem_cache_free(idr_layer_cache, p);
840    }
841
842    return 0;
843}
844EXPORT_SYMBOL(ida_get_new_above);
845
846/**
847 * ida_get_new - allocate new ID
848 * @ida: idr handle
849 * @p_id: pointer to the allocated handle
850 *
851 * Allocate new ID. It should be called with any required locks.
852 *
853 * If memory is required, it will return -EAGAIN, you should unlock
854 * and go back to the idr_pre_get() call. If the idr is full, it will
855 * return -ENOSPC.
856 *
857 * @id returns a value in the range 0 ... 0x7fffffff.
858 */
859int ida_get_new(struct ida *ida, int *p_id)
860{
861    return ida_get_new_above(ida, 0, p_id);
862}
863EXPORT_SYMBOL(ida_get_new);
864
865/**
866 * ida_remove - remove the given ID
867 * @ida: ida handle
868 * @id: ID to free
869 */
870void ida_remove(struct ida *ida, int id)
871{
872    struct idr_layer *p = ida->idr.top;
873    int shift = (ida->idr.layers - 1) * IDR_BITS;
874    int idr_id = id / IDA_BITMAP_BITS;
875    int offset = id % IDA_BITMAP_BITS;
876    int n;
877    struct ida_bitmap *bitmap;
878
879    /* clear full bits while looking up the leaf idr_layer */
880    while ((shift > 0) && p) {
881        n = (idr_id >> shift) & IDR_MASK;
882        __clear_bit(n, &p->bitmap);
883        p = p->ary[n];
884        shift -= IDR_BITS;
885    }
886
887    if (p == NULL)
888        goto err;
889
890    n = idr_id & IDR_MASK;
891    __clear_bit(n, &p->bitmap);
892
893    bitmap = (void *)p->ary[n];
894    if (!test_bit(offset, bitmap->bitmap))
895        goto err;
896
897    /* update bitmap and remove it if empty */
898    __clear_bit(offset, bitmap->bitmap);
899    if (--bitmap->nr_busy == 0) {
900        __set_bit(n, &p->bitmap); /* to please idr_remove() */
901        idr_remove(&ida->idr, idr_id);
902        free_bitmap(ida, bitmap);
903    }
904
905    return;
906
907 err:
908    printk(KERN_WARNING
909           "ida_remove called for id=%d which is not allocated.\n", id);
910}
911EXPORT_SYMBOL(ida_remove);
912
913/**
914 * ida_destroy - release all cached layers within an ida tree
915 * ida: ida handle
916 */
917void ida_destroy(struct ida *ida)
918{
919    idr_destroy(&ida->idr);
920    kfree(ida->free_bitmap);
921}
922EXPORT_SYMBOL(ida_destroy);
923
924/**
925 * ida_init - initialize ida handle
926 * @ida: ida handle
927 *
928 * This function is use to set up the handle (@ida) that you will pass
929 * to the rest of the functions.
930 */
931void ida_init(struct ida *ida)
932{
933    memset(ida, 0, sizeof(struct ida));
934    idr_init(&ida->idr);
935
936}
937EXPORT_SYMBOL(ida_init);
938

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