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  * 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
  36 static kmem_cache_t *idr_layer_cache;
  37
  38 static 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 */
  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 }
  60
  61 static 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  */
  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);
  97
  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;
 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
 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;
 175
 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 }
 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  */
 238 int 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 }
 256 EXPORT_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  */
 273 int 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 }
 291 EXPORT_SYMBOL(idr_get_new);
 292
 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 }
 298
 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;
 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: uniqueue key
 334  */
 335 void 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 }
 358 EXPORT_SYMBOL(idr_remove);
 359
 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);
 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  */
 384 void *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 }
 404 EXPORT_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  */
 418 void *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 }
 446 EXPORT_SYMBOL(idr_replace);
 447
 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 }
 453
 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 }
 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  */
 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);