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