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 * Small id to pointer translation service.
10 *
11 * It uses a radix tree like structure as a sparse array indexed
12 * by the id to obtain the pointer.  The bitmap makes allocating
13 * a new id quick.
14 *
15 * You call it to allocate an id (an int) an associate with that id a
16 * pointer or what ever, we treat it as a (void *).  You can pass this
17 * id to a user for him to pass back at a later time.  You then pass
18 * that id to this code and it returns your pointer.
19
20 * You can release ids at any time. When all ids are released, most of
21 * the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
22 * don't need to go to the memory "store" during an id allocate, just
23 * so you don't need to be too concerned about locking and conflicts
24 * with the slab allocator.
25 */
26
27#ifndef TEST                            // to test in user space...
28#include <linux/slab.h>
29#include <linux/init.h>
30#include <linux/module.h>
31#endif
32#include <linux/err.h>
33#include <linux/string.h>
34#include <linux/idr.h>
35
36static struct kmem_cache *idr_layer_cache;
37
38static struct idr_layer *alloc_layer(struct idr *idp)
39{
40	struct idr_layer *p;
41	unsigned long flags;
42
43	spin_lock_irqsave(&idp->lock, flags);
44	if ((p = idp->id_free)) {
45		idp->id_free = p->ary[0];
46		idp->id_free_cnt--;
47		p->ary[0] = NULL;
48	}
49	spin_unlock_irqrestore(&idp->lock, flags);
50	return(p);
51}
52
53/* only called when idp->lock is held */
54static void __free_layer(struct idr *idp, struct idr_layer *p)
55{
56	p->ary[0] = idp->id_free;
57	idp->id_free = p;
58	idp->id_free_cnt++;
59}
60
61static void free_layer(struct idr *idp, struct idr_layer *p)
62{
63	unsigned long flags;
64
65	/*
66	 * Depends on the return element being zeroed.
67	 */
68	spin_lock_irqsave(&idp->lock, flags);
69	__free_layer(idp, p);
70	spin_unlock_irqrestore(&idp->lock, flags);
71}
72
73/**
74 * idr_pre_get - reserver resources for idr allocation
75 * @idp:	idr handle
76 * @gfp_mask:	memory allocation flags
77 *
78 * This function should be called prior to locking and calling the
79 * following function.  It preallocates enough memory to satisfy
80 * the worst possible allocation.
81 *
82 * If the system is REALLY out of memory this function returns 0,
83 * otherwise 1.
84 */
85int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
86{
87	while (idp->id_free_cnt < IDR_FREE_MAX) {
88		struct idr_layer *new;
89		new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
90		if (new == NULL)
91			return (0);
92		free_layer(idp, new);
93	}
94	return 1;
95}
96EXPORT_SYMBOL(idr_pre_get);
97
98static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
99{
100	int n, m, sh;
101	struct idr_layer *p, *new;
102	struct idr_layer *pa[MAX_LEVEL];
103	int l, id;
104	long bm;
105
106	id = *starting_id;
107	p = idp->top;
108	l = idp->layers;
109	pa[l--] = NULL;
110	while (1) {
111		/*
112		 * We run around this while until we reach the leaf node...
113		 */
114		n = (id >> (IDR_BITS*l)) & IDR_MASK;
115		bm = ~p->bitmap;
116		m = find_next_bit(&bm, IDR_SIZE, n);
117		if (m == IDR_SIZE) {
118			/* no space available go back to previous layer. */
119			l++;
120			id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
121			if (!(p = pa[l])) {
122				*starting_id = id;
123				return -2;
124			}
125			continue;
126		}
127		if (m != n) {
128			sh = IDR_BITS*l;
129			id = ((id >> sh) ^ n ^ m) << sh;
130		}
131		if ((id >= MAX_ID_BIT) || (id < 0))
132			return -3;
133		if (l == 0)
134			break;
135		/*
136		 * Create the layer below if it is missing.
137		 */
138		if (!p->ary[m]) {
139			if (!(new = alloc_layer(idp)))
140				return -1;
141			p->ary[m] = new;
142			p->count++;
143		}
144		pa[l--] = p;
145		p = p->ary[m];
146	}
147	/*
148	 * We have reached the leaf node, plant the
149	 * users pointer and return the raw id.
150	 */
151	p->ary[m] = (struct idr_layer *)ptr;
152	__set_bit(m, &p->bitmap);
153	p->count++;
154	/*
155	 * If this layer is full mark the bit in the layer above
156	 * to show that this part of the radix tree is full.
157	 * This may complete the layer above and require walking
158	 * up the radix tree.
159	 */
160	n = id;
161	while (p->bitmap == IDR_FULL) {
162		if (!(p = pa[++l]))
163			break;
164		n = n >> IDR_BITS;
165		__set_bit((n & IDR_MASK), &p->bitmap);
166	}
167	return(id);
168}
169
170static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
171{
172	struct idr_layer *p, *new;
173	int layers, v, id;
174	unsigned long flags;
175
176	id = starting_id;
177build_up:
178	p = idp->top;
179	layers = idp->layers;
180	if (unlikely(!p)) {
181		if (!(p = alloc_layer(idp)))
182			return -1;
183		layers = 1;
184	}
185	/*
186	 * Add a new layer to the top of the tree if the requested
187	 * id is larger than the currently allocated space.
188	 */
189	while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
190		layers++;
191		if (!p->count)
192			continue;
193		if (!(new = alloc_layer(idp))) {
194			/*
195			 * The allocation failed.  If we built part of
196			 * the structure tear it down.
197			 */
198			spin_lock_irqsave(&idp->lock, flags);
199			for (new = p; p && p != idp->top; new = p) {
200				p = p->ary[0];
201				new->ary[0] = NULL;
202				new->bitmap = new->count = 0;
203				__free_layer(idp, new);
204			}
205			spin_unlock_irqrestore(&idp->lock, flags);
206			return -1;
207		}
208		new->ary[0] = p;
209		new->count = 1;
210		if (p->bitmap == IDR_FULL)
211			__set_bit(0, &new->bitmap);
212		p = new;
213	}
214	idp->top = p;
215	idp->layers = layers;
216	v = sub_alloc(idp, ptr, &id);
217	if (v == -2)
218		goto build_up;
219	return(v);
220}
221
222/**
223 * idr_get_new_above - allocate new idr entry above or equal to a start id
224 * @idp: idr handle
225 * @ptr: pointer you want associated with the ide
226 * @start_id: id to start search at
227 * @id: pointer to the allocated handle
228 *
229 * This is the allocate id function.  It should be called with any
230 * required locks.
231 *
232 * If memory is required, it will return -EAGAIN, you should unlock
233 * and go back to the idr_pre_get() call.  If the idr is full, it will
234 * return -ENOSPC.
235 *
236 * @id returns a value in the range 0 ... 0x7fffffff
237 */
238int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
239{
240	int rv;
241
242	rv = idr_get_new_above_int(idp, ptr, starting_id);
243	/*
244	 * This is a cheap hack until the IDR code can be fixed to
245	 * return proper error values.
246	 */
247	if (rv < 0) {
248		if (rv == -1)
249			return -EAGAIN;
250		else /* Will be -3 */
251			return -ENOSPC;
252	}
253	*id = rv;
254	return 0;
255}
256EXPORT_SYMBOL(idr_get_new_above);
257
258/**
259 * idr_get_new - allocate new idr entry
260 * @idp: idr handle
261 * @ptr: pointer you want associated with the ide
262 * @id: pointer to the allocated handle
263 *
264 * This is the allocate id function.  It should be called with any
265 * required locks.
266 *
267 * If memory is required, it will return -EAGAIN, you should unlock
268 * and go back to the idr_pre_get() call.  If the idr is full, it will
269 * return -ENOSPC.
270 *
271 * @id returns a value in the range 0 ... 0x7fffffff
272 */
273int idr_get_new(struct idr *idp, void *ptr, int *id)
274{
275	int rv;
276
277	rv = idr_get_new_above_int(idp, ptr, 0);
278	/*
279	 * This is a cheap hack until the IDR code can be fixed to
280	 * return proper error values.
281	 */
282	if (rv < 0) {
283		if (rv == -1)
284			return -EAGAIN;
285		else /* Will be -3 */
286			return -ENOSPC;
287	}
288	*id = rv;
289	return 0;
290}
291EXPORT_SYMBOL(idr_get_new);
292
293static void idr_remove_warning(int id)
294{
295	printk("idr_remove called for id=%d which is not allocated.\n", id);
296	dump_stack();
297}
298
299static void sub_remove(struct idr *idp, int shift, int id)
300{
301	struct idr_layer *p = idp->top;
302	struct idr_layer **pa[MAX_LEVEL];
303	struct idr_layer ***paa = &pa[0];
304	int n;
305
306	*paa = NULL;
307	*++paa = &idp->top;
308
309	while ((shift > 0) && p) {
310		n = (id >> shift) & IDR_MASK;
311		__clear_bit(n, &p->bitmap);
312		*++paa = &p->ary[n];
313		p = p->ary[n];
314		shift -= IDR_BITS;
315	}
316	n = id & IDR_MASK;
317	if (likely(p != NULL && test_bit(n, &p->bitmap))){
318		__clear_bit(n, &p->bitmap);
319		p->ary[n] = NULL;
320		while(*paa && ! --((**paa)->count)){
321			free_layer(idp, **paa);
322			**paa-- = NULL;
323		}
324		if (!*paa)
325			idp->layers = 0;
326	} else
327		idr_remove_warning(id);
328}
329
330/**
331 * idr_remove - remove the given id and free it's slot
332 * @idp: idr handle
333 * @id: unique key
334 */
335void idr_remove(struct idr *idp, int id)
336{
337	struct idr_layer *p;
338
339	/* Mask off upper bits we don't use for the search. */
340	id &= MAX_ID_MASK;
341
342	sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
343	if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
344	    idp->top->ary[0]) {  // We can drop a layer
345
346		p = idp->top->ary[0];
347		idp->top->bitmap = idp->top->count = 0;
348		free_layer(idp, idp->top);
349		idp->top = p;
350		--idp->layers;
351	}
352	while (idp->id_free_cnt >= IDR_FREE_MAX) {
353		p = alloc_layer(idp);
354		kmem_cache_free(idr_layer_cache, p);
355		return;
356	}
357}
358EXPORT_SYMBOL(idr_remove);
359
360/**
361 * idr_destroy - release all cached layers within an idr tree
362 * idp: idr handle
363 */
364void idr_destroy(struct idr *idp)
365{
366	while (idp->id_free_cnt) {
367		struct idr_layer *p = alloc_layer(idp);
368		kmem_cache_free(idr_layer_cache, p);
369	}
370}
371EXPORT_SYMBOL(idr_destroy);
372
373/**
374 * idr_find - return pointer for given id
375 * @idp: idr handle
376 * @id: lookup key
377 *
378 * Return the pointer given the id it has been registered with.  A %NULL
379 * return indicates that @id is not valid or you passed %NULL in
380 * idr_get_new().
381 *
382 * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
383 */
384void *idr_find(struct idr *idp, int id)
385{
386	int n;
387	struct idr_layer *p;
388
389	n = idp->layers * IDR_BITS;
390	p = idp->top;
391
392	/* Mask off upper bits we don't use for the search. */
393	id &= MAX_ID_MASK;
394
395	if (id >= (1 << n))
396		return NULL;
397
398	while (n > 0 && p) {
399		n -= IDR_BITS;
400		p = p->ary[(id >> n) & IDR_MASK];
401	}
402	return((void *)p);
403}
404EXPORT_SYMBOL(idr_find);
405
406/**
407 * idr_replace - replace pointer for given id
408 * @idp: idr handle
409 * @ptr: pointer you want associated with the id
410 * @id: lookup key
411 *
412 * Replace the pointer registered with an id and return the old value.
413 * A -ENOENT return indicates that @id was not found.
414 * A -EINVAL return indicates that @id was not within valid constraints.
415 *
416 * The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
417 */
418void *idr_replace(struct idr *idp, void *ptr, int id)
419{
420	int n;
421	struct idr_layer *p, *old_p;
422
423	n = idp->layers * IDR_BITS;
424	p = idp->top;
425
426	id &= MAX_ID_MASK;
427
428	if (id >= (1 << n))
429		return ERR_PTR(-EINVAL);
430
431	n -= IDR_BITS;
432	while ((n > 0) && p) {
433		p = p->ary[(id >> n) & IDR_MASK];
434		n -= IDR_BITS;
435	}
436
437	n = id & IDR_MASK;
438	if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
439		return ERR_PTR(-ENOENT);
440
441	old_p = p->ary[n];
442	p->ary[n] = ptr;
443
444	return old_p;
445}
446EXPORT_SYMBOL(idr_replace);
447
448static void idr_cache_ctor(void * idr_layer, struct kmem_cache *idr_layer_cache,
449		unsigned long flags)
450{
451	memset(idr_layer, 0, sizeof(struct idr_layer));
452}
453
454static  int init_id_cache(void)
455{
456	if (!idr_layer_cache)
457		idr_layer_cache = kmem_cache_create("idr_layer_cache",
458			sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
459	return 0;
460}
461
462/**
463 * idr_init - initialize idr handle
464 * @idp:	idr handle
465 *
466 * This function is use to set up the handle (@idp) that you will pass
467 * to the rest of the functions.
468 */
469void idr_init(struct idr *idp)
470{
471	init_id_cache();
472	memset(idp, 0, sizeof(struct idr));
473	spin_lock_init(&idp->lock);
474}
475EXPORT_SYMBOL(idr_init);
476