lib/radix-tree.c

   1 /*
   2  * Copyright (C) 2001 Momchil Velikov
   3  * Portions Copyright (C) 2001 Christoph Hellwig
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation; either version 2, or (at
   8  * your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  */
  19
  20 #include <linux/errno.h>
  21 #include <linux/init.h>
  22 #include <linux/kernel.h>
  23 #include <linux/mempool.h>
  24 #include <linux/module.h>
  25 #include <linux/radix-tree.h>
  26 #include <linux/slab.h>
  27 #include <linux/string.h>
  28
  29 /*
  30  * Radix tree node definition.
  31  */
  32 #define RADIX_TREE_MAP_SHIFT  6
  33 #define RADIX_TREE_MAP_SIZE  (1UL << RADIX_TREE_MAP_SHIFT)
  34 #define RADIX_TREE_MAP_MASK  (RADIX_TREE_MAP_SIZE-1)
  35
  36 struct radix_tree_node {
  37         unsigned int    count;
  38         void            *slots[RADIX_TREE_MAP_SIZE];
  39 };
  40
  41 struct radix_tree_path {
  42         struct radix_tree_node *node, **slot;
  43 };
  44
  45 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
  46 #define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
  47
  48 /*
  49  * Radix tree node cache.
  50  */
  51 static kmem_cache_t *radix_tree_node_cachep;
  52 static mempool_t *radix_tree_node_pool;
  53
  54 static inline struct radix_tree_node *
  55 radix_tree_node_alloc(struct radix_tree_root *root)
  56 {
  57         return mempool_alloc(radix_tree_node_pool, root->gfp_mask);
  58 }
  59
  60 static inline void
  61 radix_tree_node_free(struct radix_tree_node *node)
  62 {
  63         mempool_free(node, radix_tree_node_pool);
  64 }
  65
  66 /*
  67  *      Return the maximum key which can be store into a
  68  *      radix tree with height HEIGHT.
  69  */
  70 static inline unsigned long radix_tree_maxindex(unsigned int height)
  71 {
  72         unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
  73         unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
  74
  75         if (tmp >= RADIX_TREE_INDEX_BITS)
  76                 index = ~0UL;
  77         return index;
  78 }
  79
  80 /*
  81  *      Extend a radix tree so it can store key @index.
  82  */
  83 static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
  84 {
  85         struct radix_tree_node *node;
  86         unsigned int height;
  87
  88         /* Figure out what the height should be.  */
  89         height = root->height + 1;
  90         while (index > radix_tree_maxindex(height))
  91                 height++;
  92
  93         if (root->rnode) {
  94                 do {
  95                         if (!(node = radix_tree_node_alloc(root)))
  96                                 return -ENOMEM;
  97
  98                         /* Increase the height.  */
  99                         node->slots[0] = root->rnode;
 100                         if (root->rnode)
 101                                 node->count = 1;
 102                         root->rnode = node;
 103                         root->height++;
 104                 } while (height > root->height);
 105         } else
 106                 root->height = height;
 107
 108         return 0;
 109 }
 110
 111 /**
 112  *      radix_tree_insert    -    insert into a radix tree
 113  *      @root:          radix tree root
 114  *      @index:         index key
 115  *      @item:          item to insert
 116  *
 117  *      Insert an item into the radix tree at position @index.
 118  */
 119 int radix_tree_insert(struct radix_tree_root *root, unsigned long index, void *item)
 120 {
 121         struct radix_tree_node *node = NULL, *tmp, **slot;
 122         unsigned int height, shift;
 123         int error;
 124
 125         /* Make sure the tree is high enough.  */
 126         if (index > radix_tree_maxindex(root->height)) {
 127                 error = radix_tree_extend(root, index);
 128                 if (error)
 129                         return error;
 130         }
 131
 132         slot = &root->rnode;
 133         height = root->height;
 134         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 135
 136         while (height > 0) {
 137                 if (*slot == NULL) {
 138                         /* Have to add a child node.  */
 139                         if (!(tmp = radix_tree_node_alloc(root)))
 140                                 return -ENOMEM;
 141                         *slot = tmp;
 142                         if (node)
 143                                 node->count++;
 144                 }
 145
 146                 /* Go a level down.  */
 147                 node = *slot;
 148                 slot = (struct radix_tree_node **)
 149                         (node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK));
 150                 shift -= RADIX_TREE_MAP_SHIFT;
 151                 height--;
 152         }
 153
 154         if (*slot != NULL)
 155                 return -EEXIST;
 156         if (node)
 157                 node->count++;
 158
 159         *slot = item;
 160         return 0;
 161 }
 162 EXPORT_SYMBOL(radix_tree_insert);
 163
 164 /**
 165  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 166  *      @root:          radix tree root
 167  *      @index:         index key
 168  *
 169  *      Lookup them item at the position @index in the radix tree @root.
 170  */
 171 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 172 {
 173         unsigned int height, shift;
 174         struct radix_tree_node **slot;
 175
 176         height = root->height;
 177         if (index > radix_tree_maxindex(height))
 178                 return NULL;
 179
 180         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 181         slot = &root->rnode;
 182
 183         while (height > 0) {
 184                 if (*slot == NULL)
 185                         return NULL;
 186
 187                 slot = (struct radix_tree_node **)
 188                         ((*slot)->slots + ((index >> shift) & RADIX_TREE_MAP_MASK));
 189                 shift -= RADIX_TREE_MAP_SHIFT;
 190                 height--;
 191         }
 192
 193         return (void *) *slot;
 194 }
 195 EXPORT_SYMBOL(radix_tree_lookup);
 196
 197 static /* inline */ unsigned int
 198 __lookup(struct radix_tree_root *root, void **results, unsigned long index,
 199         unsigned int max_items, unsigned long *next_index,
 200         unsigned long max_index)
 201 {
 202         unsigned int nr_found = 0;
 203         unsigned int shift;
 204         unsigned int height = root->height;
 205         struct radix_tree_node *slot;
 206
 207         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 208         slot = root->rnode;
 209
 210         while (height > 0) {
 211                 unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
 212                 for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
 213                         if (slot->slots[i] != NULL)
 214                                 break;
 215                         index &= ~((1 << shift) - 1);
 216                         index += 1 << shift;
 217                 }
 218                 if (i == RADIX_TREE_MAP_SIZE)
 219                         goto out;
 220                 height--;
 221                 shift -= RADIX_TREE_MAP_SHIFT;
 222                 if (height == 0) {
 223                         /* Bottom level: grab some items */
 224                         unsigned long j;
 225
 226                         BUG_ON((shift + RADIX_TREE_MAP_SHIFT) != 0);
 227
 228                         j = index & RADIX_TREE_MAP_MASK;
 229                         for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
 230                                 index++;
 231                                 if (slot->slots[j]) {
 232                                         results[nr_found++] = slot->slots[j];
 233                                         if (nr_found == max_items)
 234                                                 goto out;
 235                                 }
 236                         }
 237                 }
 238                 slot = slot->slots[i];
 239         }
 240 out:
 241         *next_index = index;
 242         return nr_found;
 243 }
 244
 245 /**
 246  *      radix_tree_gang_lookup - perform multiple lookup on a radix tree
 247  *      @root:          radix tree root
 248  *      @results:       where the results of the lookup are placed
 249  *      @first_index:   start the lookup from this key
 250  *      @max_items:     place up to this many items at *results
 251  *
 252  *      Performs an index-ascending scan of the tree for present items.  Places
 253  *      them at *@results and returns the number of items which were placed at
 254  *      *@results.
 255  *
 256  *      The implementation is naive.
 257  */
 258 unsigned int
 259 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 260                         unsigned long first_index, unsigned int max_items)
 261 {
 262         const unsigned long max_index = radix_tree_maxindex(root->height);
 263         unsigned long cur_index = first_index;
 264         unsigned int ret = 0;
 265
 266         if (root->rnode == NULL)
 267                 goto out;
 268         if (max_index == 0) {                   /* Bah.  Special case */
 269                 if (first_index == 0) {
 270                         if (max_items > 0) {
 271                                 *results = root->rnode;
 272                                 ret = 1;
 273                         }
 274                 }
 275                 goto out;
 276         }
 277         while (ret < max_items) {
 278                 unsigned int nr_found;
 279                 unsigned long next_index;       /* Index of next search */
 280
 281                 if (cur_index > max_index)
 282                         break;
 283                 nr_found = __lookup(root, results + ret, cur_index,
 284                                 max_items - ret, &next_index, max_index);
 285                 ret += nr_found;
 286                 if (next_index == max_index)
 287                         break;
 288                 cur_index = next_index;
 289         }
 290 out:
 291         return ret;
 292 }
 293 EXPORT_SYMBOL(radix_tree_gang_lookup);
 294
 295 /**
 296  *      radix_tree_delete    -    delete an item from a radix tree
 297  *      @root:          radix tree root
 298  *      @index:         index key
 299  *
 300  *      Remove the item at @index from the radix tree rooted at @root.
 301  */
 302 int radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 303 {
 304         struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
 305         unsigned int height, shift;
 306
 307         height = root->height;
 308         if (index > radix_tree_maxindex(height))
 309                 return -ENOENT;
 310
 311         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 312         pathp->node = NULL;
 313         pathp->slot = &root->rnode;
 314
 315         while (height > 0) {
 316                 if (*pathp->slot == NULL)
 317                         return -ENOENT;
 318
 319                 pathp[1].node = *pathp[0].slot;
 320                 pathp[1].slot = (struct radix_tree_node **)
 321                     (pathp[1].node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK));
 322                 pathp++;
 323                 shift -= RADIX_TREE_MAP_SHIFT;
 324                 height--;
 325         }
 326
 327         if (*pathp[0].slot == NULL)
 328                 return -ENOENT;
 329
 330         *pathp[0].slot = NULL;
 331         while (pathp[0].node && --pathp[0].node->count == 0) {
 332                 pathp--;
 333                 *pathp[0].slot = NULL;
 334                 radix_tree_node_free(pathp[1].node);
 335         }
 336
 337         if (root->rnode == NULL)
 338                 root->height = 0;  /* Empty tree, we can reset the height */
 339
 340         return 0;
 341 }
 342 EXPORT_SYMBOL(radix_tree_delete);
 343
 344 static void radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
 345 {
 346         memset(node, 0, sizeof(struct radix_tree_node));
 347 }
 348
 349 static void *radix_tree_node_pool_alloc(int gfp_mask, void *data)
 350 {
 351         return kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 352 }
 353
 354 static void radix_tree_node_pool_free(void *node, void *data)
 355 {
 356         kmem_cache_free(radix_tree_node_cachep, node);
 357 }
 358
 359 /*
 360  * FIXME!  512 nodes is 200-300k of memory.  This needs to be
 361  * scaled by the amount of available memory, and hopefully
 362  * reduced also.
 363  */
 364 void __init radix_tree_init(void)
 365 {
 366         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
 367                         sizeof(struct radix_tree_node), 0,
 368                         SLAB_HWCACHE_ALIGN, radix_tree_node_ctor, NULL);
 369         if (!radix_tree_node_cachep)
 370                 panic ("Failed to create radix_tree_node cache\n");
 371         radix_tree_node_pool = mempool_create(512, radix_tree_node_pool_alloc,
 372                         radix_tree_node_pool_free, NULL);
 373         if (!radix_tree_node_pool)
 374                 panic ("Failed to create radix_tree_node pool\n");
 375 }