ia64/linux-2.6.18-xen.hg

view lib/idr.c @ 912:dd42cdb0ab89

[IA64] Build blktap2 driver by default in x86 builds.

add CONFIG_XEN_BLKDEV_TAP2=y to buildconfigs/linux-defconfig_xen_ia64.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
author Isaku Yamahata <yamahata@valinux.co.jp>
date Mon Jun 29 12:09:16 2009 +0900 (2009-06-29)
parents 831230e53067
children
line source
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.
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 */
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>
36 static kmem_cache_t *idr_layer_cache;
38 static struct idr_layer *alloc_layer(struct idr *idp)
39 {
40 struct idr_layer *p;
41 unsigned long flags;
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 }
53 /* only called when idp->lock is held */
54 static 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 }
61 static void free_layer(struct idr *idp, struct idr_layer *p)
62 {
63 unsigned long flags;
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 }
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 */
85 int 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 }
96 EXPORT_SYMBOL(idr_pre_get);
98 static 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;
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 }
170 static 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;
176 id = starting_id;
177 build_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 }
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 */
238 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
239 {
240 int rv;
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 }
256 EXPORT_SYMBOL(idr_get_new_above);
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 */
273 int idr_get_new(struct idr *idp, void *ptr, int *id)
274 {
275 int rv;
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 }
291 EXPORT_SYMBOL(idr_get_new);
293 static 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 }
299 static 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;
306 *paa = NULL;
307 *++paa = &idp->top;
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 }
330 /**
331 * idr_remove - remove the given id and free it's slot
332 * idp: idr handle
333 * id: uniqueue key
334 */
335 void idr_remove(struct idr *idp, int id)
336 {
337 struct idr_layer *p;
339 /* Mask off upper bits we don't use for the search. */
340 id &= MAX_ID_MASK;
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
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 }
358 EXPORT_SYMBOL(idr_remove);
360 /**
361 * idr_destroy - release all cached layers within an idr tree
362 * idp: idr handle
363 */
364 void 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 }
371 EXPORT_SYMBOL(idr_destroy);
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 */
384 void *idr_find(struct idr *idp, int id)
385 {
386 int n;
387 struct idr_layer *p;
389 n = idp->layers * IDR_BITS;
390 p = idp->top;
392 /* Mask off upper bits we don't use for the search. */
393 id &= MAX_ID_MASK;
395 if (id >= (1 << n))
396 return NULL;
398 while (n > 0 && p) {
399 n -= IDR_BITS;
400 p = p->ary[(id >> n) & IDR_MASK];
401 }
402 return((void *)p);
403 }
404 EXPORT_SYMBOL(idr_find);
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 */
418 void *idr_replace(struct idr *idp, void *ptr, int id)
419 {
420 int n;
421 struct idr_layer *p, *old_p;
423 n = idp->layers * IDR_BITS;
424 p = idp->top;
426 id &= MAX_ID_MASK;
428 if (id >= (1 << n))
429 return ERR_PTR(-EINVAL);
431 n -= IDR_BITS;
432 while ((n > 0) && p) {
433 p = p->ary[(id >> n) & IDR_MASK];
434 n -= IDR_BITS;
435 }
437 n = id & IDR_MASK;
438 if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
439 return ERR_PTR(-ENOENT);
441 old_p = p->ary[n];
442 p->ary[n] = ptr;
444 return old_p;
445 }
446 EXPORT_SYMBOL(idr_replace);
448 static void idr_cache_ctor(void * idr_layer, kmem_cache_t *idr_layer_cache,
449 unsigned long flags)
450 {
451 memset(idr_layer, 0, sizeof(struct idr_layer));
452 }
454 static 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 }
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 */
469 void idr_init(struct idr *idp)
470 {
471 init_id_cache();
472 memset(idp, 0, sizeof(struct idr));
473 spin_lock_init(&idp->lock);
474 }
475 EXPORT_SYMBOL(idr_init);