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  7
  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
  47 /*
  48  * Radix tree node cache.
  49  */
  50 static kmem_cache_t *radix_tree_node_cachep;
  51 static mempool_t *radix_tree_node_pool;
  52
  53 static inline struct radix_tree_node *
  54 radix_tree_node_alloc(struct radix_tree_root *root)
  55 {
  56         return mempool_alloc(radix_tree_node_pool, root->gfp_mask);
  57 }
  58
  59 static inline void
  60 radix_tree_node_free(struct radix_tree_node *node)
  61 {
  62         mempool_free(node, radix_tree_node_pool);
  63 }
  64
  65 /*
  66  *      Return the maximum key which can be store into a
  67  *      radix tree with height HEIGHT.
  68  */
  69 static inline unsigned long radix_tree_maxindex(unsigned int height)
  70 {
  71         unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
  72         unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
  73
  74         if (tmp >= RADIX_TREE_INDEX_BITS)
  75                 index = ~0UL;
  76         return index;
  77 }
  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 /**
 113  *      radix_tree_reserve    -    reserve space in a radix tree
 114  *      @root:          radix tree root
 115  *      @index:         index key
 116  *      @pslot:         pointer to reserved slot
 117  *
 118  *      Reserve a slot in a radix tree for the key @index.
 119  */
 120 int radix_tree_reserve(struct radix_tree_root *root, unsigned long index, void ***pslot)
 121 {
 122         struct radix_tree_node *node = NULL, *tmp, **slot;
 123         unsigned int height, shift;
 124         int error;
 125
 126         /* Make sure the tree is high enough.  */
 127         if (index > radix_tree_maxindex(root->height)) {
 128                 error = radix_tree_extend(root, index);
 129                 if (error)
 130                         return error;
 131         }
 132
 133         slot = &root->rnode;
 134         height = root->height;
 135         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 136
 137         while (height > 0) {
 138                 if (*slot == NULL) {
 139                         /* Have to add a child node.  */
 140                         if (!(tmp = radix_tree_node_alloc(root)))
 141                                 return -ENOMEM;
 142                         *slot = tmp;
 143                         if (node)
 144                                 node->count++;
 145                 }
 146
 147                 /* Go a level down.  */
 148                 node = *slot;
 149                 slot = (struct radix_tree_node **)
 150                         (node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK));
 151                 shift -= RADIX_TREE_MAP_SHIFT;
 152                 height--;
 153         }
 154
 155         if (*slot != NULL)
 156                 return -EEXIST;
 157         if (node)
 158                 node->count++;
 159
 160         *pslot = (void **)slot;
 161         **pslot = RADIX_TREE_SLOT_RESERVED;
 162         return 0;
 163 }
 164
 165 EXPORT_SYMBOL(radix_tree_reserve);
 166
 167
 168 /**
 169  *      radix_tree_insert    -    insert into a radix tree
 170  *      @root:          radix tree root
 171  *      @index:         index key
 172  *      @item:          item to insert
 173  *
 174  *      Insert an item into the radix tree at position @index.
 175  */
 176 int radix_tree_insert(struct radix_tree_root *root, unsigned long index, void *item)
 177 {
 178         void **slot;
 179         int error;
 180
 181         error = radix_tree_reserve(root, index, &slot);
 182         if (!error)
 183                 *slot = item;
 184         return error;
 185 }
 186
 187 EXPORT_SYMBOL(radix_tree_insert);
 188
 189
 190 /**
 191  *      radix_tree_lookup    -    perform lookup operation on a radix tree
 192  *      @root:          radix tree root
 193  *      @index:         index key
 194  *
 195  *      Lookup them item at the position @index in the radix tree @root.
 196  */
 197 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 198 {
 199         unsigned int height, shift;
 200         struct radix_tree_node **slot;
 201
 202         height = root->height;
 203         if (index > radix_tree_maxindex(height))
 204                 return NULL;
 205
 206         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 207         slot = &root->rnode;
 208
 209         while (height > 0) {
 210                 if (*slot == NULL)
 211                         return NULL;
 212
 213                 slot = (struct radix_tree_node **)
 214                         ((*slot)->slots + ((index >> shift) & RADIX_TREE_MAP_MASK));
 215                 shift -= RADIX_TREE_MAP_SHIFT;
 216                 height--;
 217         }
 218
 219         return (void *) *slot;
 220 }
 221
 222 EXPORT_SYMBOL(radix_tree_lookup);
 223
 224
 225 /**
 226  *      radix_tree_delete    -    delete an item from a radix tree
 227  *      @root:          radix tree root
 228  *      @index:         index key
 229  *
 230  *      Remove the item at @index from the radix tree rooted at @root.
 231  */
 232 int radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 233 {
 234         struct radix_tree_path path[RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2], *pathp = path;
 235         unsigned int height, shift;
 236
 237         height = root->height;
 238         if (index > radix_tree_maxindex(height))
 239                 return -ENOENT;
 240
 241         shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 242         pathp->node = NULL;
 243         pathp->slot = &root->rnode;
 244
 245         while (height > 0) {
 246                 if (*pathp->slot == NULL)
 247                         return -ENOENT;
 248
 249                 pathp[1].node = *pathp[0].slot;
 250                 pathp[1].slot = (struct radix_tree_node **)
 251                     (pathp[1].node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK));
 252                 pathp++;
 253                 shift -= RADIX_TREE_MAP_SHIFT;
 254                 height--;
 255         }
 256
 257         if (*pathp[0].slot == NULL)
 258                 return -ENOENT;
 259
 260         *pathp[0].slot = NULL;
 261         while (pathp[0].node && --pathp[0].node->count == 0) {
 262                 pathp--;
 263                 *pathp[0].slot = NULL;
 264                 radix_tree_node_free(pathp[1].node);
 265         }
 266
 267         return 0;
 268 }
 269
 270 EXPORT_SYMBOL(radix_tree_delete);
 271
 272 static void radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)
 273 {
 274         memset(node, 0, sizeof(struct radix_tree_node));
 275 }
 276
 277 static void *radix_tree_node_pool_alloc(int gfp_mask, void *data)
 278 {
 279         return kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 280 }
 281
 282 static void radix_tree_node_pool_free(void *node, void *data)
 283 {
 284         kmem_cache_free(radix_tree_node_cachep, node);
 285 }
 286
 287 /*
 288  * FIXME!  512 nodes is 200-300k of memory.  This needs to be
 289  * scaled by the amount of available memory, and hopefully
 290  * reduced also.
 291  */
 292 void __init radix_tree_init(void)
 293 {
 294         radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
 295                         sizeof(struct radix_tree_node), 0,
 296                         SLAB_HWCACHE_ALIGN, radix_tree_node_ctor, NULL);
 297         if (!radix_tree_node_cachep)
 298                 panic ("Failed to create radix_tree_node cache\n");
 299         radix_tree_node_pool = mempool_create(512, radix_tree_node_pool_alloc,
 300                         radix_tree_node_pool_free, NULL);
 301         if (!radix_tree_node_pool)
 302                 panic ("Failed to create radix_tree_node pool\n");
 303 }