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 MAX_IDR_FREE) 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/export.h>
33#endif
34#include <linux/err.h>
35#include <linux/string.h>
36#include <linux/idr.h>
37#include <linux/spinlock.h>
38#include <linux/percpu.h>
39#include <linux/hardirq.h>
40
41#define MAX_IDR_SHIFT (sizeof(int) * 8 - 1)
42#define MAX_IDR_BIT (1U << MAX_IDR_SHIFT)
43
44/* Leave the possibility of an incomplete final layer */
45#define MAX_IDR_LEVEL ((MAX_IDR_SHIFT + IDR_BITS - 1) / IDR_BITS)
46
47/* Number of id_layer structs to leave in free list */
48#define MAX_IDR_FREE (MAX_IDR_LEVEL * 2)
49
50static struct kmem_cache *idr_layer_cache;
51static DEFINE_PER_CPU(struct idr_layer *, idr_preload_head);
52static DEFINE_PER_CPU(int, idr_preload_cnt);
53static DEFINE_SPINLOCK(simple_ida_lock);
54
55/* the maximum ID which can be allocated given idr->layers */
56static int idr_max(int layers)
57{
58    int bits = min_t(int, layers * IDR_BITS, MAX_IDR_SHIFT);
59
60    return (1 << bits) - 1;
61}
62
63/*
64 * Prefix mask for an idr_layer at @layer. For layer 0, the prefix mask is
65 * all bits except for the lower IDR_BITS. For layer 1, 2 * IDR_BITS, and
66 * so on.
67 */
68static int idr_layer_prefix_mask(int layer)
69{
70    return ~idr_max(layer + 1);
71}
72
73static struct idr_layer *get_from_free_list(struct idr *idp)
74{
75    struct idr_layer *p;
76    unsigned long flags;
77
78    spin_lock_irqsave(&idp->lock, flags);
79    if ((p = idp->id_free)) {
80        idp->id_free = p->ary[0];
81        idp->id_free_cnt--;
82        p->ary[0] = NULL;
83    }
84    spin_unlock_irqrestore(&idp->lock, flags);
85    return(p);
86}
87
88/**
89 * idr_layer_alloc - allocate a new idr_layer
90 * @gfp_mask: allocation mask
91 * @layer_idr: optional idr to allocate from
92 *
93 * If @layer_idr is %NULL, directly allocate one using @gfp_mask or fetch
94 * one from the per-cpu preload buffer. If @layer_idr is not %NULL, fetch
95 * an idr_layer from @idr->id_free.
96 *
97 * @layer_idr is to maintain backward compatibility with the old alloc
98 * interface - idr_pre_get() and idr_get_new*() - and will be removed
99 * together with per-pool preload buffer.
100 */
101static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)
102{
103    struct idr_layer *new;
104
105    /* this is the old path, bypass to get_from_free_list() */
106    if (layer_idr)
107        return get_from_free_list(layer_idr);
108
109    /*
110     * Try to allocate directly from kmem_cache. We want to try this
111     * before preload buffer; otherwise, non-preloading idr_alloc()
112     * users will end up taking advantage of preloading ones. As the
113     * following is allowed to fail for preloaded cases, suppress
114     * warning this time.
115     */
116    new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN);
117    if (new)
118        return new;
119
120    /*
121     * Try to fetch one from the per-cpu preload buffer if in process
122     * context. See idr_preload() for details.
123     */
124    if (!in_interrupt()) {
125        preempt_disable();
126        new = __this_cpu_read(idr_preload_head);
127        if (new) {
128            __this_cpu_write(idr_preload_head, new->ary[0]);
129            __this_cpu_dec(idr_preload_cnt);
130            new->ary[0] = NULL;
131        }
132        preempt_enable();
133        if (new)
134            return new;
135    }
136
137    /*
138     * Both failed. Try kmem_cache again w/o adding __GFP_NOWARN so
139     * that memory allocation failure warning is printed as intended.
140     */
141    return kmem_cache_zalloc(idr_layer_cache, gfp_mask);
142}
143
144static void idr_layer_rcu_free(struct rcu_head *head)
145{
146    struct idr_layer *layer;
147
148    layer = container_of(head, struct idr_layer, rcu_head);
149    kmem_cache_free(idr_layer_cache, layer);
150}
151
152static inline void free_layer(struct idr *idr, struct idr_layer *p)
153{
154    if (idr->hint && idr->hint == p)
155        RCU_INIT_POINTER(idr->hint, NULL);
156    call_rcu(&p->rcu_head, idr_layer_rcu_free);
157}
158
159/* only called when idp->lock is held */
160static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
161{
162    p->ary[0] = idp->id_free;
163    idp->id_free = p;
164    idp->id_free_cnt++;
165}
166
167static void move_to_free_list(struct idr *idp, struct idr_layer *p)
168{
169    unsigned long flags;
170
171    /*
172     * Depends on the return element being zeroed.
173     */
174    spin_lock_irqsave(&idp->lock, flags);
175    __move_to_free_list(idp, p);
176    spin_unlock_irqrestore(&idp->lock, flags);
177}
178
179static void idr_mark_full(struct idr_layer **pa, int id)
180{
181    struct idr_layer *p = pa[0];
182    int l = 0;
183
184    __set_bit(id & IDR_MASK, p->bitmap);
185    /*
186     * If this layer is full mark the bit in the layer above to
187     * show that this part of the radix tree is full. This may
188     * complete the layer above and require walking up the radix
189     * tree.
190     */
191    while (bitmap_full(p->bitmap, IDR_SIZE)) {
192        if (!(p = pa[++l]))
193            break;
194        id = id >> IDR_BITS;
195        __set_bit((id & IDR_MASK), p->bitmap);
196    }
197}
198
199int __idr_pre_get(struct idr *idp, gfp_t gfp_mask)
200{
201    while (idp->id_free_cnt < MAX_IDR_FREE) {
202        struct idr_layer *new;
203        new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
204        if (new == NULL)
205            return (0);
206        move_to_free_list(idp, new);
207    }
208    return 1;
209}
210EXPORT_SYMBOL(__idr_pre_get);
211
212/**
213 * sub_alloc - try to allocate an id without growing the tree depth
214 * @idp: idr handle
215 * @starting_id: id to start search at
216 * @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer
217 * @gfp_mask: allocation mask for idr_layer_alloc()
218 * @layer_idr: optional idr passed to idr_layer_alloc()
219 *
220 * Allocate an id in range [@starting_id, INT_MAX] from @idp without
221 * growing its depth. Returns
222 *
223 * the allocated id >= 0 if successful,
224 * -EAGAIN if the tree needs to grow for allocation to succeed,
225 * -ENOSPC if the id space is exhausted,
226 * -ENOMEM if more idr_layers need to be allocated.
227 */
228static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa,
229             gfp_t gfp_mask, struct idr *layer_idr)
230{
231    int n, m, sh;
232    struct idr_layer *p, *new;
233    int l, id, oid;
234
235    id = *starting_id;
236 restart:
237    p = idp->top;
238    l = idp->layers;
239    pa[l--] = NULL;
240    while (1) {
241        /*
242         * We run around this while until we reach the leaf node...
243         */
244        n = (id >> (IDR_BITS*l)) & IDR_MASK;
245        m = find_next_zero_bit(p->bitmap, IDR_SIZE, n);
246        if (m == IDR_SIZE) {
247            /* no space available go back to previous layer. */
248            l++;
249            oid = id;
250            id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
251
252            /* if already at the top layer, we need to grow */
253            if (id >= 1 << (idp->layers * IDR_BITS)) {
254                *starting_id = id;
255                return -EAGAIN;
256            }
257            p = pa[l];
258            BUG_ON(!p);
259
260            /* If we need to go up one layer, continue the
261             * loop; otherwise, restart from the top.
262             */
263            sh = IDR_BITS * (l + 1);
264            if (oid >> sh == id >> sh)
265                continue;
266            else
267                goto restart;
268        }
269        if (m != n) {
270            sh = IDR_BITS*l;
271            id = ((id >> sh) ^ n ^ m) << sh;
272        }
273        if ((id >= MAX_IDR_BIT) || (id < 0))
274            return -ENOSPC;
275        if (l == 0)
276            break;
277        /*
278         * Create the layer below if it is missing.
279         */
280        if (!p->ary[m]) {
281            new = idr_layer_alloc(gfp_mask, layer_idr);
282            if (!new)
283                return -ENOMEM;
284            new->layer = l-1;
285            new->prefix = id & idr_layer_prefix_mask(new->layer);
286            rcu_assign_pointer(p->ary[m], new);
287            p->count++;
288        }
289        pa[l--] = p;
290        p = p->ary[m];
291    }
292
293    pa[l] = p;
294    return id;
295}
296
297static int idr_get_empty_slot(struct idr *idp, int starting_id,
298                  struct idr_layer **pa, gfp_t gfp_mask,
299                  struct idr *layer_idr)
300{
301    struct idr_layer *p, *new;
302    int layers, v, id;
303    unsigned long flags;
304
305    id = starting_id;
306build_up:
307    p = idp->top;
308    layers = idp->layers;
309    if (unlikely(!p)) {
310        if (!(p = idr_layer_alloc(gfp_mask, layer_idr)))
311            return -ENOMEM;
312        p->layer = 0;
313        layers = 1;
314    }
315    /*
316     * Add a new layer to the top of the tree if the requested
317     * id is larger than the currently allocated space.
318     */
319    while (id > idr_max(layers)) {
320        layers++;
321        if (!p->count) {
322            /* special case: if the tree is currently empty,
323             * then we grow the tree by moving the top node
324             * upwards.
325             */
326            p->layer++;
327            WARN_ON_ONCE(p->prefix);
328            continue;
329        }
330        if (!(new = idr_layer_alloc(gfp_mask, layer_idr))) {
331            /*
332             * The allocation failed. If we built part of
333             * the structure tear it down.
334             */
335            spin_lock_irqsave(&idp->lock, flags);
336            for (new = p; p && p != idp->top; new = p) {
337                p = p->ary[0];
338                new->ary[0] = NULL;
339                new->count = 0;
340                bitmap_clear(new->bitmap, 0, IDR_SIZE);
341                __move_to_free_list(idp, new);
342            }
343            spin_unlock_irqrestore(&idp->lock, flags);
344            return -ENOMEM;
345        }
346        new->ary[0] = p;
347        new->count = 1;
348        new->layer = layers-1;
349        new->prefix = id & idr_layer_prefix_mask(new->layer);
350        if (bitmap_full(p->bitmap, IDR_SIZE))
351            __set_bit(0, new->bitmap);
352        p = new;
353    }
354    rcu_assign_pointer(idp->top, p);
355    idp->layers = layers;
356    v = sub_alloc(idp, &id, pa, gfp_mask, layer_idr);
357    if (v == -EAGAIN)
358        goto build_up;
359    return(v);
360}
361
362/*
363 * @id and @pa are from a successful allocation from idr_get_empty_slot().
364 * Install the user pointer @ptr and mark the slot full.
365 */
366static void idr_fill_slot(struct idr *idr, void *ptr, int id,
367              struct idr_layer **pa)
368{
369    /* update hint used for lookup, cleared from free_layer() */
370    rcu_assign_pointer(idr->hint, pa[0]);
371
372    rcu_assign_pointer(pa[0]->ary[id & IDR_MASK], (struct idr_layer *)ptr);
373    pa[0]->count++;
374    idr_mark_full(pa, id);
375}
376
377int __idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
378{
379    struct idr_layer *pa[MAX_IDR_LEVEL + 1];
380    int rv;
381
382    rv = idr_get_empty_slot(idp, starting_id, pa, 0, idp);
383    if (rv < 0)
384        return rv == -ENOMEM ? -EAGAIN : rv;
385
386    idr_fill_slot(idp, ptr, rv, pa);
387    *id = rv;
388    return 0;
389}
390EXPORT_SYMBOL(__idr_get_new_above);
391
392/**
393 * idr_preload - preload for idr_alloc()
394 * @gfp_mask: allocation mask to use for preloading
395 *
396 * Preload per-cpu layer buffer for idr_alloc(). Can only be used from
397 * process context and each idr_preload() invocation should be matched with
398 * idr_preload_end(). Note that preemption is disabled while preloaded.
399 *
400 * The first idr_alloc() in the preloaded section can be treated as if it
401 * were invoked with @gfp_mask used for preloading. This allows using more
402 * permissive allocation masks for idrs protected by spinlocks.
403 *
404 * For example, if idr_alloc() below fails, the failure can be treated as
405 * if idr_alloc() were called with GFP_KERNEL rather than GFP_NOWAIT.
406 *
407 * idr_preload(GFP_KERNEL);
408 * spin_lock(lock);
409 *
410 * id = idr_alloc(idr, ptr, start, end, GFP_NOWAIT);
411 *
412 * spin_unlock(lock);
413 * idr_preload_end();
414 * if (id < 0)
415 * error;
416 */
417void idr_preload(gfp_t gfp_mask)
418{
419    /*
420     * Consuming preload buffer from non-process context breaks preload
421     * allocation guarantee. Disallow usage from those contexts.
422     */
423    WARN_ON_ONCE(in_interrupt());
424    might_sleep_if(gfp_mask & __GFP_WAIT);
425
426    preempt_disable();
427
428    /*
429     * idr_alloc() is likely to succeed w/o full idr_layer buffer and
430     * return value from idr_alloc() needs to be checked for failure
431     * anyway. Silently give up if allocation fails. The caller can
432     * treat failures from idr_alloc() as if idr_alloc() were called
433     * with @gfp_mask which should be enough.
434     */
435    while (__this_cpu_read(idr_preload_cnt) < MAX_IDR_FREE) {
436        struct idr_layer *new;
437
438        preempt_enable();
439        new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
440        preempt_disable();
441        if (!new)
442            break;
443
444        /* link the new one to per-cpu preload list */
445        new->ary[0] = __this_cpu_read(idr_preload_head);
446        __this_cpu_write(idr_preload_head, new);
447        __this_cpu_inc(idr_preload_cnt);
448    }
449}
450EXPORT_SYMBOL(idr_preload);
451
452/**
453 * idr_alloc - allocate new idr entry
454 * @idr: the (initialized) idr
455 * @ptr: pointer to be associated with the new id
456 * @start: the minimum id (inclusive)
457 * @end: the maximum id (exclusive, <= 0 for max)
458 * @gfp_mask: memory allocation flags
459 *
460 * Allocate an id in [start, end) and associate it with @ptr. If no ID is
461 * available in the specified range, returns -ENOSPC. On memory allocation
462 * failure, returns -ENOMEM.
463 *
464 * Note that @end is treated as max when <= 0. This is to always allow
465 * using @start + N as @end as long as N is inside integer range.
466 *
467 * The user is responsible for exclusively synchronizing all operations
468 * which may modify @idr. However, read-only accesses such as idr_find()
469 * or iteration can be performed under RCU read lock provided the user
470 * destroys @ptr in RCU-safe way after removal from idr.
471 */
472int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
473{
474    int max = end > 0 ? end - 1 : INT_MAX; /* inclusive upper limit */
475    struct idr_layer *pa[MAX_IDR_LEVEL + 1];
476    int id;
477
478    might_sleep_if(gfp_mask & __GFP_WAIT);
479
480    /* sanity checks */
481    if (WARN_ON_ONCE(start < 0))
482        return -EINVAL;
483    if (unlikely(max < start))
484        return -ENOSPC;
485
486    /* allocate id */
487    id = idr_get_empty_slot(idr, start, pa, gfp_mask, NULL);
488    if (unlikely(id < 0))
489        return id;
490    if (unlikely(id > max))
491        return -ENOSPC;
492
493    idr_fill_slot(idr, ptr, id, pa);
494    return id;
495}
496EXPORT_SYMBOL_GPL(idr_alloc);
497
498/**
499 * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
500 * @idr: the (initialized) idr
501 * @ptr: pointer to be associated with the new id
502 * @start: the minimum id (inclusive)
503 * @end: the maximum id (exclusive, <= 0 for max)
504 * @gfp_mask: memory allocation flags
505 *
506 * Essentially the same as idr_alloc, but prefers to allocate progressively
507 * higher ids if it can. If the "cur" counter wraps, then it will start again
508 * at the "start" end of the range and allocate one that has already been used.
509 */
510int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,
511            gfp_t gfp_mask)
512{
513    int id;
514
515    id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);
516    if (id == -ENOSPC)
517        id = idr_alloc(idr, ptr, start, end, gfp_mask);
518
519    if (likely(id >= 0))
520        idr->cur = id + 1;
521    return id;
522}
523EXPORT_SYMBOL(idr_alloc_cyclic);
524
525static void idr_remove_warning(int id)
526{
527    WARN(1, "idr_remove called for id=%d which is not allocated.\n", id);
528}
529
530static void sub_remove(struct idr *idp, int shift, int id)
531{
532    struct idr_layer *p = idp->top;
533    struct idr_layer **pa[MAX_IDR_LEVEL + 1];
534    struct idr_layer ***paa = &pa[0];
535    struct idr_layer *to_free;
536    int n;
537
538    *paa = NULL;
539    *++paa = &idp->top;
540
541    while ((shift > 0) && p) {
542        n = (id >> shift) & IDR_MASK;
543        __clear_bit(n, p->bitmap);
544        *++paa = &p->ary[n];
545        p = p->ary[n];
546        shift -= IDR_BITS;
547    }
548    n = id & IDR_MASK;
549    if (likely(p != NULL && test_bit(n, p->bitmap))) {
550        __clear_bit(n, p->bitmap);
551        rcu_assign_pointer(p->ary[n], NULL);
552        to_free = NULL;
553        while(*paa && ! --((**paa)->count)){
554            if (to_free)
555                free_layer(idp, to_free);
556            to_free = **paa;
557            **paa-- = NULL;
558        }
559        if (!*paa)
560            idp->layers = 0;
561        if (to_free)
562            free_layer(idp, to_free);
563    } else
564        idr_remove_warning(id);
565}
566
567/**
568 * idr_remove - remove the given id and free its slot
569 * @idp: idr handle
570 * @id: unique key
571 */
572void idr_remove(struct idr *idp, int id)
573{
574    struct idr_layer *p;
575    struct idr_layer *to_free;
576
577    if (id < 0)
578        return;
579
580    sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
581    if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
582        idp->top->ary[0]) {
583        /*
584         * Single child at leftmost slot: we can shrink the tree.
585         * This level is not needed anymore since when layers are
586         * inserted, they are inserted at the top of the existing
587         * tree.
588         */
589        to_free = idp->top;
590        p = idp->top->ary[0];
591        rcu_assign_pointer(idp->top, p);
592        --idp->layers;
593        to_free->count = 0;
594        bitmap_clear(to_free->bitmap, 0, IDR_SIZE);
595        free_layer(idp, to_free);
596    }
597    while (idp->id_free_cnt >= MAX_IDR_FREE) {
598        p = get_from_free_list(idp);
599        /*
600         * Note: we don't call the rcu callback here, since the only
601         * layers that fall into the freelist are those that have been
602         * preallocated.
603         */
604        kmem_cache_free(idr_layer_cache, p);
605    }
606    return;
607}
608EXPORT_SYMBOL(idr_remove);
609
610void __idr_remove_all(struct idr *idp)
611{
612    int n, id, max;
613    int bt_mask;
614    struct idr_layer *p;
615    struct idr_layer *pa[MAX_IDR_LEVEL + 1];
616    struct idr_layer **paa = &pa[0];
617
618    n = idp->layers * IDR_BITS;
619    p = idp->top;
620    rcu_assign_pointer(idp->top, NULL);
621    max = idr_max(idp->layers);
622
623    id = 0;
624    while (id >= 0 && id <= max) {
625        while (n > IDR_BITS && p) {
626            n -= IDR_BITS;
627            *paa++ = p;
628            p = p->ary[(id >> n) & IDR_MASK];
629        }
630
631        bt_mask = id;
632        id += 1 << n;
633        /* Get the highest bit that the above add changed from 0->1. */
634        while (n < fls(id ^ bt_mask)) {
635            if (p)
636                free_layer(idp, p);
637            n += IDR_BITS;
638            p = *--paa;
639        }
640    }
641    idp->layers = 0;
642}
643EXPORT_SYMBOL(__idr_remove_all);
644
645/**
646 * idr_destroy - release all cached layers within an idr tree
647 * @idp: idr handle
648 *
649 * Free all id mappings and all idp_layers. After this function, @idp is
650 * completely unused and can be freed / recycled. The caller is
651 * responsible for ensuring that no one else accesses @idp during or after
652 * idr_destroy().
653 *
654 * A typical clean-up sequence for objects stored in an idr tree will use
655 * idr_for_each() to free all objects, if necessay, then idr_destroy() to
656 * free up the id mappings and cached idr_layers.
657 */
658void idr_destroy(struct idr *idp)
659{
660    __idr_remove_all(idp);
661
662    while (idp->id_free_cnt) {
663        struct idr_layer *p = get_from_free_list(idp);
664        kmem_cache_free(idr_layer_cache, p);
665    }
666}
667EXPORT_SYMBOL(idr_destroy);
668
669void *idr_find_slowpath(struct idr *idp, int id)
670{
671    int n;
672    struct idr_layer *p;
673
674    if (id < 0)
675        return NULL;
676
677    p = rcu_dereference_raw(idp->top);
678    if (!p)
679        return NULL;
680    n = (p->layer+1) * IDR_BITS;
681
682    if (id > idr_max(p->layer + 1))
683        return NULL;
684    BUG_ON(n == 0);
685
686    while (n > 0 && p) {
687        n -= IDR_BITS;
688        BUG_ON(n != p->layer*IDR_BITS);
689        p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
690    }
691    return((void *)p);
692}
693EXPORT_SYMBOL(idr_find_slowpath);
694
695/**
696 * idr_for_each - iterate through all stored pointers
697 * @idp: idr handle
698 * @fn: function to be called for each pointer
699 * @data: data passed back to callback function
700 *
701 * Iterate over the pointers registered with the given idr. The
702 * callback function will be called for each pointer currently
703 * registered, passing the id, the pointer and the data pointer passed
704 * to this function. It is not safe to modify the idr tree while in
705 * the callback, so functions such as idr_get_new and idr_remove are
706 * not allowed.
707 *
708 * We check the return of @fn each time. If it returns anything other
709 * than %0, we break out and return that value.
710 *
711 * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
712 */
713int idr_for_each(struct idr *idp,
714         int (*fn)(int id, void *p, void *data), void *data)
715{
716    int n, id, max, error = 0;
717    struct idr_layer *p;
718    struct idr_layer *pa[MAX_IDR_LEVEL + 1];
719    struct idr_layer **paa = &pa[0];
720
721    n = idp->layers * IDR_BITS;
722    p = rcu_dereference_raw(idp->top);
723    max = idr_max(idp->layers);
724
725    id = 0;
726    while (id >= 0 && id <= max) {
727        while (n > 0 && p) {
728            n -= IDR_BITS;
729            *paa++ = p;
730            p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
731        }
732
733        if (p) {
734            error = fn(id, (void *)p, data);
735            if (error)
736                break;
737        }
738
739        id += 1 << n;
740        while (n < fls(id)) {
741            n += IDR_BITS;
742            p = *--paa;
743        }
744    }
745
746    return error;
747}
748EXPORT_SYMBOL(idr_for_each);
749
750/**
751 * idr_get_next - lookup next object of id to given id.
752 * @idp: idr handle
753 * @nextidp: pointer to lookup key
754 *
755 * Returns pointer to registered object with id, which is next number to
756 * given id. After being looked up, *@nextidp will be updated for the next
757 * iteration.
758 *
759 * This function can be called under rcu_read_lock(), given that the leaf
760 * pointers lifetimes are correctly managed.
761 */
762void *idr_get_next(struct idr *idp, int *nextidp)
763{
764    struct idr_layer *p, *pa[MAX_IDR_LEVEL + 1];
765    struct idr_layer **paa = &pa[0];
766    int id = *nextidp;
767    int n, max;
768
769    /* find first ent */
770    p = rcu_dereference_raw(idp->top);
771    if (!p)
772        return NULL;
773    n = (p->layer + 1) * IDR_BITS;
774    max = idr_max(p->layer + 1);
775
776    while (id >= 0 && id <= max) {
777        while (n > 0 && p) {
778            n -= IDR_BITS;
779            *paa++ = p;
780            p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
781        }
782
783        if (p) {
784            *nextidp = id;
785            return p;
786        }
787
788        /*
789         * Proceed to the next layer at the current level. Unlike
790         * idr_for_each(), @id isn't guaranteed to be aligned to
791         * layer boundary at this point and adding 1 << n may
792         * incorrectly skip IDs. Make sure we jump to the
793         * beginning of the next layer using round_up().
794         */
795        id = round_up(id + 1, 1 << n);
796        while (n < fls(id)) {
797            n += IDR_BITS;
798            p = *--paa;
799        }
800    }
801    return NULL;
802}
803EXPORT_SYMBOL(idr_get_next);
804
805
806/**
807 * idr_replace - replace pointer for given id
808 * @idp: idr handle
809 * @ptr: pointer you want associated with the id
810 * @id: lookup key
811 *
812 * Replace the pointer registered with an id and return the old value.
813 * A %-ENOENT return indicates that @id was not found.
814 * A %-EINVAL return indicates that @id was not within valid constraints.
815 *
816 * The caller must serialize with writers.
817 */
818void *idr_replace(struct idr *idp, void *ptr, int id)
819{
820    int n;
821    struct idr_layer *p, *old_p;
822
823    if (id < 0)
824        return ERR_PTR(-EINVAL);
825
826    p = idp->top;
827    if (!p)
828        return ERR_PTR(-EINVAL);
829
830    n = (p->layer+1) * IDR_BITS;
831
832    if (id >= (1 << n))
833        return ERR_PTR(-EINVAL);
834
835    n -= IDR_BITS;
836    while ((n > 0) && p) {
837        p = p->ary[(id >> n) & IDR_MASK];
838        n -= IDR_BITS;
839    }
840
841    n = id & IDR_MASK;
842    if (unlikely(p == NULL || !test_bit(n, p->bitmap)))
843        return ERR_PTR(-ENOENT);
844
845    old_p = p->ary[n];
846    rcu_assign_pointer(p->ary[n], ptr);
847
848    return old_p;
849}
850EXPORT_SYMBOL(idr_replace);
851
852void __init idr_init_cache(void)
853{
854    idr_layer_cache = kmem_cache_create("idr_layer_cache",
855                sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
856}
857
858/**
859 * idr_init - initialize idr handle
860 * @idp: idr handle
861 *
862 * This function is use to set up the handle (@idp) that you will pass
863 * to the rest of the functions.
864 */
865void idr_init(struct idr *idp)
866{
867    memset(idp, 0, sizeof(struct idr));
868    spin_lock_init(&idp->lock);
869}
870EXPORT_SYMBOL(idr_init);
871
872
873/**
874 * DOC: IDA description
875 * IDA - IDR based ID allocator
876 *
877 * This is id allocator without id -> pointer translation. Memory
878 * usage is much lower than full blown idr because each id only
879 * occupies a bit. ida uses a custom leaf node which contains
880 * IDA_BITMAP_BITS slots.
881 *
882 * 2007-04-25 written by Tejun Heo <htejun@gmail.com>
883 */
884
885static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
886{
887    unsigned long flags;
888
889    if (!ida->free_bitmap) {
890        spin_lock_irqsave(&ida->idr.lock, flags);
891        if (!ida->free_bitmap) {
892            ida->free_bitmap = bitmap;
893            bitmap = NULL;
894        }
895        spin_unlock_irqrestore(&ida->idr.lock, flags);
896    }
897
898    kfree(bitmap);
899}
900
901/**
902 * ida_pre_get - reserve resources for ida allocation
903 * @ida: ida handle
904 * @gfp_mask: memory allocation flag
905 *
906 * This function should be called prior to locking and calling the
907 * following function. It preallocates enough memory to satisfy the
908 * worst possible allocation.
909 *
910 * If the system is REALLY out of memory this function returns %0,
911 * otherwise %1.
912 */
913int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
914{
915    /* allocate idr_layers */
916    if (!__idr_pre_get(&ida->idr, gfp_mask))
917        return 0;
918
919    /* allocate free_bitmap */
920    if (!ida->free_bitmap) {
921        struct ida_bitmap *bitmap;
922
923        bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
924        if (!bitmap)
925            return 0;
926
927        free_bitmap(ida, bitmap);
928    }
929
930    return 1;
931}
932EXPORT_SYMBOL(ida_pre_get);
933
934/**
935 * ida_get_new_above - allocate new ID above or equal to a start id
936 * @ida: ida handle
937 * @starting_id: id to start search at
938 * @p_id: pointer to the allocated handle
939 *
940 * Allocate new ID above or equal to @starting_id. It should be called
941 * with any required locks.
942 *
943 * If memory is required, it will return %-EAGAIN, you should unlock
944 * and go back to the ida_pre_get() call. If the ida is full, it will
945 * return %-ENOSPC.
946 *
947 * @p_id returns a value in the range @starting_id ... %0x7fffffff.
948 */
949int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
950{
951    struct idr_layer *pa[MAX_IDR_LEVEL + 1];
952    struct ida_bitmap *bitmap;
953    unsigned long flags;
954    int idr_id = starting_id / IDA_BITMAP_BITS;
955    int offset = starting_id % IDA_BITMAP_BITS;
956    int t, id;
957
958 restart:
959    /* get vacant slot */
960    t = idr_get_empty_slot(&ida->idr, idr_id, pa, 0, &ida->idr);
961    if (t < 0)
962        return t == -ENOMEM ? -EAGAIN : t;
963
964    if (t * IDA_BITMAP_BITS >= MAX_IDR_BIT)
965        return -ENOSPC;
966
967    if (t != idr_id)
968        offset = 0;
969    idr_id = t;
970
971    /* if bitmap isn't there, create a new one */
972    bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
973    if (!bitmap) {
974        spin_lock_irqsave(&ida->idr.lock, flags);
975        bitmap = ida->free_bitmap;
976        ida->free_bitmap = NULL;
977        spin_unlock_irqrestore(&ida->idr.lock, flags);
978
979        if (!bitmap)
980            return -EAGAIN;
981
982        memset(bitmap, 0, sizeof(struct ida_bitmap));
983        rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
984                (void *)bitmap);
985        pa[0]->count++;
986    }
987
988    /* lookup for empty slot */
989    t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
990    if (t == IDA_BITMAP_BITS) {
991        /* no empty slot after offset, continue to the next chunk */
992        idr_id++;
993        offset = 0;
994        goto restart;
995    }
996
997    id = idr_id * IDA_BITMAP_BITS + t;
998    if (id >= MAX_IDR_BIT)
999        return -ENOSPC;
1000
1001    __set_bit(t, bitmap->bitmap);
1002    if (++bitmap->nr_busy == IDA_BITMAP_BITS)
1003        idr_mark_full(pa, idr_id);
1004
1005    *p_id = id;
1006
1007    /* Each leaf node can handle nearly a thousand slots and the
1008     * whole idea of ida is to have small memory foot print.
1009     * Throw away extra resources one by one after each successful
1010     * allocation.
1011     */
1012    if (ida->idr.id_free_cnt || ida->free_bitmap) {
1013        struct idr_layer *p = get_from_free_list(&ida->idr);
1014        if (p)
1015            kmem_cache_free(idr_layer_cache, p);
1016    }
1017
1018    return 0;
1019}
1020EXPORT_SYMBOL(ida_get_new_above);
1021
1022/**
1023 * ida_remove - remove the given ID
1024 * @ida: ida handle
1025 * @id: ID to free
1026 */
1027void ida_remove(struct ida *ida, int id)
1028{
1029    struct idr_layer *p = ida->idr.top;
1030    int shift = (ida->idr.layers - 1) * IDR_BITS;
1031    int idr_id = id / IDA_BITMAP_BITS;
1032    int offset = id % IDA_BITMAP_BITS;
1033    int n;
1034    struct ida_bitmap *bitmap;
1035
1036    /* clear full bits while looking up the leaf idr_layer */
1037    while ((shift > 0) && p) {
1038        n = (idr_id >> shift) & IDR_MASK;
1039        __clear_bit(n, p->bitmap);
1040        p = p->ary[n];
1041        shift -= IDR_BITS;
1042    }
1043
1044    if (p == NULL)
1045        goto err;
1046
1047    n = idr_id & IDR_MASK;
1048    __clear_bit(n, p->bitmap);
1049
1050    bitmap = (void *)p->ary[n];
1051    if (!test_bit(offset, bitmap->bitmap))
1052        goto err;
1053
1054    /* update bitmap and remove it if empty */
1055    __clear_bit(offset, bitmap->bitmap);
1056    if (--bitmap->nr_busy == 0) {
1057        __set_bit(n, p->bitmap); /* to please idr_remove() */
1058        idr_remove(&ida->idr, idr_id);
1059        free_bitmap(ida, bitmap);
1060    }
1061
1062    return;
1063
1064 err:
1065    WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
1066}
1067EXPORT_SYMBOL(ida_remove);
1068
1069/**
1070 * ida_destroy - release all cached layers within an ida tree
1071 * @ida: ida handle
1072 */
1073void ida_destroy(struct ida *ida)
1074{
1075    idr_destroy(&ida->idr);
1076    kfree(ida->free_bitmap);
1077}
1078EXPORT_SYMBOL(ida_destroy);
1079
1080/**
1081 * ida_simple_get - get a new id.
1082 * @ida: the (initialized) ida.
1083 * @start: the minimum id (inclusive, < 0x8000000)
1084 * @end: the maximum id (exclusive, < 0x8000000 or 0)
1085 * @gfp_mask: memory allocation flags
1086 *
1087 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
1088 * On memory allocation failure, returns -ENOMEM.
1089 *
1090 * Use ida_simple_remove() to get rid of an id.
1091 */
1092int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
1093           gfp_t gfp_mask)
1094{
1095    int ret, id;
1096    unsigned int max;
1097    unsigned long flags;
1098
1099    BUG_ON((int)start < 0);
1100    BUG_ON((int)end < 0);
1101
1102    if (end == 0)
1103        max = 0x80000000;
1104    else {
1105        BUG_ON(end < start);
1106        max = end - 1;
1107    }
1108
1109again:
1110    if (!ida_pre_get(ida, gfp_mask))
1111        return -ENOMEM;
1112
1113    spin_lock_irqsave(&simple_ida_lock, flags);
1114    ret = ida_get_new_above(ida, start, &id);
1115    if (!ret) {
1116        if (id > max) {
1117            ida_remove(ida, id);
1118            ret = -ENOSPC;
1119        } else {
1120            ret = id;
1121        }
1122    }
1123    spin_unlock_irqrestore(&simple_ida_lock, flags);
1124
1125    if (unlikely(ret == -EAGAIN))
1126        goto again;
1127
1128    return ret;
1129}
1130EXPORT_SYMBOL(ida_simple_get);
1131
1132/**
1133 * ida_simple_remove - remove an allocated id.
1134 * @ida: the (initialized) ida.
1135 * @id: the id returned by ida_simple_get.
1136 */
1137void ida_simple_remove(struct ida *ida, unsigned int id)
1138{
1139    unsigned long flags;
1140
1141    BUG_ON((int)id < 0);
1142    spin_lock_irqsave(&simple_ida_lock, flags);
1143    ida_remove(ida, id);
1144    spin_unlock_irqrestore(&simple_ida_lock, flags);
1145}
1146EXPORT_SYMBOL(ida_simple_remove);
1147
1148/**
1149 * ida_init - initialize ida handle
1150 * @ida: ida handle
1151 *
1152 * This function is use to set up the handle (@ida) that you will pass
1153 * to the rest of the functions.
1154 */
1155void ida_init(struct ida *ida)
1156{
1157    memset(ida, 0, sizeof(struct ida));
1158    idr_init(&ida->idr);
1159
1160}
1161EXPORT_SYMBOL(ida_init);
1162

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