linux/lib/genalloc.c
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   1/*
   2 * Basic general purpose allocator for managing special purpose
   3 * memory, for example, memory that is not managed by the regular
   4 * kmalloc/kfree interface.  Uses for this includes on-device special
   5 * memory, uncached memory etc.
   6 *
   7 * It is safe to use the allocator in NMI handlers and other special
   8 * unblockable contexts that could otherwise deadlock on locks.  This
   9 * is implemented by using atomic operations and retries on any
  10 * conflicts.  The disadvantage is that there may be livelocks in
  11 * extreme cases.  For better scalability, one allocator can be used
  12 * for each CPU.
  13 *
  14 * The lockless operation only works if there is enough memory
  15 * available.  If new memory is added to the pool a lock has to be
  16 * still taken.  So any user relying on locklessness has to ensure
  17 * that sufficient memory is preallocated.
  18 *
  19 * The basic atomic operation of this allocator is cmpxchg on long.
  20 * On architectures that don't have NMI-safe cmpxchg implementation,
  21 * the allocator can NOT be used in NMI handler.  So code uses the
  22 * allocator in NMI handler should depend on
  23 * CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
  24 *
  25 * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
  26 *
  27 * This source code is licensed under the GNU General Public License,
  28 * Version 2.  See the file COPYING for more details.
  29 */
  30
  31#include <linux/slab.h>
  32#include <linux/export.h>
  33#include <linux/bitmap.h>
  34#include <linux/rculist.h>
  35#include <linux/interrupt.h>
  36#include <linux/genalloc.h>
  37
  38static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
  39{
  40        unsigned long val, nval;
  41
  42        nval = *addr;
  43        do {
  44                val = nval;
  45                if (val & mask_to_set)
  46                        return -EBUSY;
  47                cpu_relax();
  48        } while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);
  49
  50        return 0;
  51}
  52
  53static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
  54{
  55        unsigned long val, nval;
  56
  57        nval = *addr;
  58        do {
  59                val = nval;
  60                if ((val & mask_to_clear) != mask_to_clear)
  61                        return -EBUSY;
  62                cpu_relax();
  63        } while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);
  64
  65        return 0;
  66}
  67
  68/*
  69 * bitmap_set_ll - set the specified number of bits at the specified position
  70 * @map: pointer to a bitmap
  71 * @start: a bit position in @map
  72 * @nr: number of bits to set
  73 *
  74 * Set @nr bits start from @start in @map lock-lessly. Several users
  75 * can set/clear the same bitmap simultaneously without lock. If two
  76 * users set the same bit, one user will return remain bits, otherwise
  77 * return 0.
  78 */
  79static int bitmap_set_ll(unsigned long *map, int start, int nr)
  80{
  81        unsigned long *p = map + BIT_WORD(start);
  82        const int size = start + nr;
  83        int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
  84        unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
  85
  86        while (nr - bits_to_set >= 0) {
  87                if (set_bits_ll(p, mask_to_set))
  88                        return nr;
  89                nr -= bits_to_set;
  90                bits_to_set = BITS_PER_LONG;
  91                mask_to_set = ~0UL;
  92                p++;
  93        }
  94        if (nr) {
  95                mask_to_set &= BITMAP_LAST_WORD_MASK(size);
  96                if (set_bits_ll(p, mask_to_set))
  97                        return nr;
  98        }
  99
 100        return 0;
 101}
 102
 103/*
 104 * bitmap_clear_ll - clear the specified number of bits at the specified position
 105 * @map: pointer to a bitmap
 106 * @start: a bit position in @map
 107 * @nr: number of bits to set
 108 *
 109 * Clear @nr bits start from @start in @map lock-lessly. Several users
 110 * can set/clear the same bitmap simultaneously without lock. If two
 111 * users clear the same bit, one user will return remain bits,
 112 * otherwise return 0.
 113 */
 114static int bitmap_clear_ll(unsigned long *map, int start, int nr)
 115{
 116        unsigned long *p = map + BIT_WORD(start);
 117        const int size = start + nr;
 118        int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
 119        unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
 120
 121        while (nr - bits_to_clear >= 0) {
 122                if (clear_bits_ll(p, mask_to_clear))
 123                        return nr;
 124                nr -= bits_to_clear;
 125                bits_to_clear = BITS_PER_LONG;
 126                mask_to_clear = ~0UL;
 127                p++;
 128        }
 129        if (nr) {
 130                mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
 131                if (clear_bits_ll(p, mask_to_clear))
 132                        return nr;
 133        }
 134
 135        return 0;
 136}
 137
 138/**
 139 * gen_pool_create - create a new special memory pool
 140 * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
 141 * @nid: node id of the node the pool structure should be allocated on, or -1
 142 *
 143 * Create a new special memory pool that can be used to manage special purpose
 144 * memory not managed by the regular kmalloc/kfree interface.
 145 */
 146struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
 147{
 148        struct gen_pool *pool;
 149
 150        pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
 151        if (pool != NULL) {
 152                spin_lock_init(&pool->lock);
 153                INIT_LIST_HEAD(&pool->chunks);
 154                pool->min_alloc_order = min_alloc_order;
 155        }
 156        return pool;
 157}
 158EXPORT_SYMBOL(gen_pool_create);
 159
 160/**
 161 * gen_pool_add_virt - add a new chunk of special memory to the pool
 162 * @pool: pool to add new memory chunk to
 163 * @virt: virtual starting address of memory chunk to add to pool
 164 * @phys: physical starting address of memory chunk to add to pool
 165 * @size: size in bytes of the memory chunk to add to pool
 166 * @nid: node id of the node the chunk structure and bitmap should be
 167 *       allocated on, or -1
 168 *
 169 * Add a new chunk of special memory to the specified pool.
 170 *
 171 * Returns 0 on success or a -ve errno on failure.
 172 */
 173int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
 174                 size_t size, int nid)
 175{
 176        struct gen_pool_chunk *chunk;
 177        int nbits = size >> pool->min_alloc_order;
 178        int nbytes = sizeof(struct gen_pool_chunk) +
 179                                BITS_TO_LONGS(nbits) * sizeof(long);
 180
 181        chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);
 182        if (unlikely(chunk == NULL))
 183                return -ENOMEM;
 184
 185        chunk->phys_addr = phys;
 186        chunk->start_addr = virt;
 187        chunk->end_addr = virt + size;
 188        atomic_set(&chunk->avail, size);
 189
 190        spin_lock(&pool->lock);
 191        list_add_rcu(&chunk->next_chunk, &pool->chunks);
 192        spin_unlock(&pool->lock);
 193
 194        return 0;
 195}
 196EXPORT_SYMBOL(gen_pool_add_virt);
 197
 198/**
 199 * gen_pool_virt_to_phys - return the physical address of memory
 200 * @pool: pool to allocate from
 201 * @addr: starting address of memory
 202 *
 203 * Returns the physical address on success, or -1 on error.
 204 */
 205phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
 206{
 207        struct gen_pool_chunk *chunk;
 208        phys_addr_t paddr = -1;
 209
 210        rcu_read_lock();
 211        list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
 212                if (addr >= chunk->start_addr && addr < chunk->end_addr) {
 213                        paddr = chunk->phys_addr + (addr - chunk->start_addr);
 214                        break;
 215                }
 216        }
 217        rcu_read_unlock();
 218
 219        return paddr;
 220}
 221EXPORT_SYMBOL(gen_pool_virt_to_phys);
 222
 223/**
 224 * gen_pool_destroy - destroy a special memory pool
 225 * @pool: pool to destroy
 226 *
 227 * Destroy the specified special memory pool. Verifies that there are no
 228 * outstanding allocations.
 229 */
 230void gen_pool_destroy(struct gen_pool *pool)
 231{
 232        struct list_head *_chunk, *_next_chunk;
 233        struct gen_pool_chunk *chunk;
 234        int order = pool->min_alloc_order;
 235        int bit, end_bit;
 236
 237        list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
 238                chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
 239                list_del(&chunk->next_chunk);
 240
 241                end_bit = (chunk->end_addr - chunk->start_addr) >> order;
 242                bit = find_next_bit(chunk->bits, end_bit, 0);
 243                BUG_ON(bit < end_bit);
 244
 245                kfree(chunk);
 246        }
 247        kfree(pool);
 248        return;
 249}
 250EXPORT_SYMBOL(gen_pool_destroy);
 251
 252/**
 253 * gen_pool_alloc - allocate special memory from the pool
 254 * @pool: pool to allocate from
 255 * @size: number of bytes to allocate from the pool
 256 *
 257 * Allocate the requested number of bytes from the specified pool.
 258 * Uses a first-fit algorithm. Can not be used in NMI handler on
 259 * architectures without NMI-safe cmpxchg implementation.
 260 */
 261unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
 262{
 263        struct gen_pool_chunk *chunk;
 264        unsigned long addr = 0;
 265        int order = pool->min_alloc_order;
 266        int nbits, start_bit = 0, end_bit, remain;
 267
 268#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 269        BUG_ON(in_nmi());
 270#endif
 271
 272        if (size == 0)
 273                return 0;
 274
 275        nbits = (size + (1UL << order) - 1) >> order;
 276        rcu_read_lock();
 277        list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
 278                if (size > atomic_read(&chunk->avail))
 279                        continue;
 280
 281                end_bit = (chunk->end_addr - chunk->start_addr) >> order;
 282retry:
 283                start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit,
 284                                                       start_bit, nbits, 0);
 285                if (start_bit >= end_bit)
 286                        continue;
 287                remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
 288                if (remain) {
 289                        remain = bitmap_clear_ll(chunk->bits, start_bit,
 290                                                 nbits - remain);
 291                        BUG_ON(remain);
 292                        goto retry;
 293                }
 294
 295                addr = chunk->start_addr + ((unsigned long)start_bit << order);
 296                size = nbits << order;
 297                atomic_sub(size, &chunk->avail);
 298                break;
 299        }
 300        rcu_read_unlock();
 301        return addr;
 302}
 303EXPORT_SYMBOL(gen_pool_alloc);
 304
 305/**
 306 * gen_pool_free - free allocated special memory back to the pool
 307 * @pool: pool to free to
 308 * @addr: starting address of memory to free back to pool
 309 * @size: size in bytes of memory to free
 310 *
 311 * Free previously allocated special memory back to the specified
 312 * pool.  Can not be used in NMI handler on architectures without
 313 * NMI-safe cmpxchg implementation.
 314 */
 315void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
 316{
 317        struct gen_pool_chunk *chunk;
 318        int order = pool->min_alloc_order;
 319        int start_bit, nbits, remain;
 320
 321#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 322        BUG_ON(in_nmi());
 323#endif
 324
 325        nbits = (size + (1UL << order) - 1) >> order;
 326        rcu_read_lock();
 327        list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
 328                if (addr >= chunk->start_addr && addr < chunk->end_addr) {
 329                        BUG_ON(addr + size > chunk->end_addr);
 330                        start_bit = (addr - chunk->start_addr) >> order;
 331                        remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
 332                        BUG_ON(remain);
 333                        size = nbits << order;
 334                        atomic_add(size, &chunk->avail);
 335                        rcu_read_unlock();
 336                        return;
 337                }
 338        }
 339        rcu_read_unlock();
 340        BUG();
 341}
 342EXPORT_SYMBOL(gen_pool_free);
 343
 344/**
 345 * gen_pool_for_each_chunk - call func for every chunk of generic memory pool
 346 * @pool:       the generic memory pool
 347 * @func:       func to call
 348 * @data:       additional data used by @func
 349 *
 350 * Call @func for every chunk of generic memory pool.  The @func is
 351 * called with rcu_read_lock held.
 352 */
 353void gen_pool_for_each_chunk(struct gen_pool *pool,
 354        void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),
 355        void *data)
 356{
 357        struct gen_pool_chunk *chunk;
 358
 359        rcu_read_lock();
 360        list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
 361                func(pool, chunk, data);
 362        rcu_read_unlock();
 363}
 364EXPORT_SYMBOL(gen_pool_for_each_chunk);
 365
 366/**
 367 * gen_pool_avail - get available free space of the pool
 368 * @pool: pool to get available free space
 369 *
 370 * Return available free space of the specified pool.
 371 */
 372size_t gen_pool_avail(struct gen_pool *pool)
 373{
 374        struct gen_pool_chunk *chunk;
 375        size_t avail = 0;
 376
 377        rcu_read_lock();
 378        list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
 379                avail += atomic_read(&chunk->avail);
 380        rcu_read_unlock();
 381        return avail;
 382}
 383EXPORT_SYMBOL_GPL(gen_pool_avail);
 384
 385/**
 386 * gen_pool_size - get size in bytes of memory managed by the pool
 387 * @pool: pool to get size
 388 *
 389 * Return size in bytes of memory managed by the pool.
 390 */
 391size_t gen_pool_size(struct gen_pool *pool)
 392{
 393        struct gen_pool_chunk *chunk;
 394        size_t size = 0;
 395
 396        rcu_read_lock();
 397        list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
 398                size += chunk->end_addr - chunk->start_addr;
 399        rcu_read_unlock();
 400        return size;
 401}
 402EXPORT_SYMBOL_GPL(gen_pool_size);
 403
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