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