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