block/qcow2-refcount.c

   1 /*
   2  * Block driver for the QCOW version 2 format
   3  *
   4  * Copyright (c) 2004-2006 Fabrice Bellard
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu-common.h"
  26 #include "block_int.h"
  27 #include "block/qcow2.h"
  28
  29 static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size);
  30 static int update_refcount(BlockDriverState *bs,
  31                             int64_t offset, int64_t length,
  32                             int addend);
  33
  34
  35 static int cache_refcount_updates = 0;
  36
  37 static int write_refcount_block(BDRVQcowState *s)
  38 {
  39     size_t size = s->cluster_size;
  40
  41     if (s->refcount_block_cache_offset == 0) {
  42         return 0;
  43     }
  44
  45     if (bdrv_pwrite(s->hd, s->refcount_block_cache_offset,
  46             s->refcount_block_cache, size) != size)
  47     {
  48         return -EIO;
  49     }
  50
  51     return 0;
  52 }
  53
  54 /*********************************************************/
  55 /* refcount handling */
  56
  57 int qcow2_refcount_init(BlockDriverState *bs)
  58 {
  59     BDRVQcowState *s = bs->opaque;
  60     int ret, refcount_table_size2, i;
  61
  62     s->refcount_block_cache = qemu_malloc(s->cluster_size);
  63     refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);
  64     s->refcount_table = qemu_malloc(refcount_table_size2);
  65     if (s->refcount_table_size > 0) {
  66         ret = bdrv_pread(s->hd, s->refcount_table_offset,
  67                          s->refcount_table, refcount_table_size2);
  68         if (ret != refcount_table_size2)
  69             goto fail;
  70         for(i = 0; i < s->refcount_table_size; i++)
  71             be64_to_cpus(&s->refcount_table[i]);
  72     }
  73     return 0;
  74  fail:
  75     return -ENOMEM;
  76 }
  77
  78 void qcow2_refcount_close(BlockDriverState *bs)
  79 {
  80     BDRVQcowState *s = bs->opaque;
  81     qemu_free(s->refcount_block_cache);
  82     qemu_free(s->refcount_table);
  83 }
  84
  85
  86 static int load_refcount_block(BlockDriverState *bs,
  87                                int64_t refcount_block_offset)
  88 {
  89     BDRVQcowState *s = bs->opaque;
  90     int ret;
  91
  92     if (cache_refcount_updates) {
  93         write_refcount_block(s);
  94     }
  95
  96     ret = bdrv_pread(s->hd, refcount_block_offset, s->refcount_block_cache,
  97                      s->cluster_size);
  98     if (ret != s->cluster_size)
  99         return -EIO;
 100     s->refcount_block_cache_offset = refcount_block_offset;
 101     return 0;
 102 }
 103
 104 static int get_refcount(BlockDriverState *bs, int64_t cluster_index)
 105 {
 106     BDRVQcowState *s = bs->opaque;
 107     int refcount_table_index, block_index;
 108     int64_t refcount_block_offset;
 109
 110     refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
 111     if (refcount_table_index >= s->refcount_table_size)
 112         return 0;
 113     refcount_block_offset = s->refcount_table[refcount_table_index];
 114     if (!refcount_block_offset)
 115         return 0;
 116     if (refcount_block_offset != s->refcount_block_cache_offset) {
 117         /* better than nothing: return allocated if read error */
 118         if (load_refcount_block(bs, refcount_block_offset) < 0)
 119             return 1;
 120     }
 121     block_index = cluster_index &
 122         ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
 123     return be16_to_cpu(s->refcount_block_cache[block_index]);
 124 }
 125
 126 static int grow_refcount_table(BlockDriverState *bs, int min_size)
 127 {
 128     BDRVQcowState *s = bs->opaque;
 129     int new_table_size, new_table_size2, refcount_table_clusters, i, ret;
 130     uint64_t *new_table;
 131     int64_t table_offset;
 132     uint8_t data[12];
 133     int old_table_size;
 134     int64_t old_table_offset;
 135
 136     if (min_size <= s->refcount_table_size)
 137         return 0;
 138     /* compute new table size */
 139     refcount_table_clusters = s->refcount_table_size >> (s->cluster_bits - 3);
 140     for(;;) {
 141         if (refcount_table_clusters == 0) {
 142             refcount_table_clusters = 1;
 143         } else {
 144             refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2;
 145         }
 146         new_table_size = refcount_table_clusters << (s->cluster_bits - 3);
 147         if (min_size <= new_table_size)
 148             break;
 149     }
 150 #ifdef DEBUG_ALLOC2
 151     printf("grow_refcount_table from %d to %d\n",
 152            s->refcount_table_size,
 153            new_table_size);
 154 #endif
 155     new_table_size2 = new_table_size * sizeof(uint64_t);
 156     new_table = qemu_mallocz(new_table_size2);
 157     memcpy(new_table, s->refcount_table,
 158            s->refcount_table_size * sizeof(uint64_t));
 159     for(i = 0; i < s->refcount_table_size; i++)
 160         cpu_to_be64s(&new_table[i]);
 161     /* Note: we cannot update the refcount now to avoid recursion */
 162     table_offset = alloc_clusters_noref(bs, new_table_size2);
 163     ret = bdrv_pwrite(s->hd, table_offset, new_table, new_table_size2);
 164     if (ret != new_table_size2)
 165         goto fail;
 166     for(i = 0; i < s->refcount_table_size; i++)
 167         be64_to_cpus(&new_table[i]);
 168
 169     cpu_to_be64w((uint64_t*)data, table_offset);
 170     cpu_to_be32w((uint32_t*)(data + 8), refcount_table_clusters);
 171     if (bdrv_pwrite(s->hd, offsetof(QCowHeader, refcount_table_offset),
 172                     data, sizeof(data)) != sizeof(data))
 173         goto fail;
 174     qemu_free(s->refcount_table);
 175     old_table_offset = s->refcount_table_offset;
 176     old_table_size = s->refcount_table_size;
 177     s->refcount_table = new_table;
 178     s->refcount_table_size = new_table_size;
 179     s->refcount_table_offset = table_offset;
 180
 181     update_refcount(bs, table_offset, new_table_size2, 1);
 182     qcow2_free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t));
 183     return 0;
 184  fail:
 185     qemu_free(new_table);
 186     return -EIO;
 187 }
 188
 189
 190 static int64_t alloc_refcount_block(BlockDriverState *bs, int64_t cluster_index)
 191 {
 192     BDRVQcowState *s = bs->opaque;
 193     int64_t offset, refcount_block_offset;
 194     unsigned int refcount_table_index;
 195     int ret;
 196     uint64_t data64;
 197     int cache = cache_refcount_updates;
 198
 199     /* Find L1 index and grow refcount table if needed */
 200     refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
 201     if (refcount_table_index >= s->refcount_table_size) {
 202         ret = grow_refcount_table(bs, refcount_table_index + 1);
 203         if (ret < 0)
 204             return ret;
 205     }
 206
 207     /* Load or allocate the refcount block */
 208     refcount_block_offset = s->refcount_table[refcount_table_index];
 209     if (!refcount_block_offset) {
 210         if (cache_refcount_updates) {
 211             write_refcount_block(s);
 212             cache_refcount_updates = 0;
 213         }
 214         /* create a new refcount block */
 215         /* Note: we cannot update the refcount now to avoid recursion */
 216         offset = alloc_clusters_noref(bs, s->cluster_size);
 217         memset(s->refcount_block_cache, 0, s->cluster_size);
 218         ret = bdrv_pwrite(s->hd, offset, s->refcount_block_cache, s->cluster_size);
 219         if (ret != s->cluster_size)
 220             return -EINVAL;
 221         s->refcount_table[refcount_table_index] = offset;
 222         data64 = cpu_to_be64(offset);
 223         ret = bdrv_pwrite(s->hd, s->refcount_table_offset +
 224                           refcount_table_index * sizeof(uint64_t),
 225                           &data64, sizeof(data64));
 226         if (ret != sizeof(data64))
 227             return -EINVAL;
 228
 229         refcount_block_offset = offset;
 230         s->refcount_block_cache_offset = offset;
 231         update_refcount(bs, offset, s->cluster_size, 1);
 232         cache_refcount_updates = cache;
 233     } else {
 234         if (refcount_block_offset != s->refcount_block_cache_offset) {
 235             if (load_refcount_block(bs, refcount_block_offset) < 0)
 236                 return -EIO;
 237         }
 238     }
 239
 240     return refcount_block_offset;
 241 }
 242
 243 #define REFCOUNTS_PER_SECTOR (512 >> REFCOUNT_SHIFT)
 244 static int write_refcount_block_entries(BDRVQcowState *s,
 245     int64_t refcount_block_offset, int first_index, int last_index)
 246 {
 247     size_t size;
 248
 249     if (cache_refcount_updates) {
 250         return 0;
 251     }
 252
 253     first_index &= ~(REFCOUNTS_PER_SECTOR - 1);
 254     last_index = (last_index + REFCOUNTS_PER_SECTOR)
 255         & ~(REFCOUNTS_PER_SECTOR - 1);
 256
 257     size = (last_index - first_index) << REFCOUNT_SHIFT;
 258     if (bdrv_pwrite(s->hd,
 259         refcount_block_offset + (first_index << REFCOUNT_SHIFT),
 260         &s->refcount_block_cache[first_index], size) != size)
 261     {
 262         return -EIO;
 263     }
 264
 265     return 0;
 266 }
 267
 268 /* XXX: cache several refcount block clusters ? */
 269 static int update_refcount(BlockDriverState *bs,
 270                             int64_t offset, int64_t length,
 271                             int addend)
 272 {
 273     BDRVQcowState *s = bs->opaque;
 274     int64_t start, last, cluster_offset;
 275     int64_t refcount_block_offset = 0;
 276     int64_t table_index = -1, old_table_index;
 277     int first_index = -1, last_index = -1;
 278
 279 #ifdef DEBUG_ALLOC2
 280     printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
 281            offset, length, addend);
 282 #endif
 283     if (length <= 0)
 284         return -EINVAL;
 285     start = offset & ~(s->cluster_size - 1);
 286     last = (offset + length - 1) & ~(s->cluster_size - 1);
 287     for(cluster_offset = start; cluster_offset <= last;
 288         cluster_offset += s->cluster_size)
 289     {
 290         int block_index, refcount;
 291         int64_t cluster_index = cluster_offset >> s->cluster_bits;
 292
 293         /* Only write refcount block to disk when we are done with it */
 294         old_table_index = table_index;
 295         table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
 296         if ((old_table_index >= 0) && (table_index != old_table_index)) {
 297
 298             if (write_refcount_block_entries(s, refcount_block_offset,
 299                 first_index, last_index) < 0)
 300             {
 301                 return -EIO;
 302             }
 303
 304             first_index = -1;
 305             last_index = -1;
 306         }
 307
 308         /* Load the refcount block and allocate it if needed */
 309         refcount_block_offset = alloc_refcount_block(bs, cluster_index);
 310         if (refcount_block_offset < 0) {
 311             return refcount_block_offset;
 312         }
 313
 314         /* we can update the count and save it */
 315         block_index = cluster_index &
 316             ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
 317         if (first_index == -1 || block_index < first_index) {
 318             first_index = block_index;
 319         }
 320         if (block_index > last_index) {
 321             last_index = block_index;
 322         }
 323
 324         refcount = be16_to_cpu(s->refcount_block_cache[block_index]);
 325         refcount += addend;
 326         if (refcount < 0 || refcount > 0xffff)
 327             return -EINVAL;
 328         if (refcount == 0 && cluster_index < s->free_cluster_index) {
 329             s->free_cluster_index = cluster_index;
 330         }
 331         s->refcount_block_cache[block_index] = cpu_to_be16(refcount);
 332     }
 333
 334     /* Write last changed block to disk */
 335     if (refcount_block_offset != 0) {
 336         if (write_refcount_block_entries(s, refcount_block_offset,
 337             first_index, last_index) < 0)
 338         {
 339             return -EIO;
 340         }
 341     }
 342
 343     return 0;
 344 }
 345
 346 /* addend must be 1 or -1 */
 347 static int update_cluster_refcount(BlockDriverState *bs,
 348                                    int64_t cluster_index,
 349                                    int addend)
 350 {
 351     BDRVQcowState *s = bs->opaque;
 352     int ret;
 353
 354     ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend);
 355     if (ret < 0) {
 356         return ret;
 357     }
 358
 359     return get_refcount(bs, cluster_index);
 360 }
 361
 362
 363
 364 /*********************************************************/
 365 /* cluster allocation functions */
 366
 367
 368
 369 /* return < 0 if error */
 370 static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size)
 371 {
 372     BDRVQcowState *s = bs->opaque;
 373     int i, nb_clusters;
 374
 375     nb_clusters = size_to_clusters(s, size);
 376 retry:
 377     for(i = 0; i < nb_clusters; i++) {
 378         int64_t i = s->free_cluster_index++;
 379         if (get_refcount(bs, i) != 0)
 380             goto retry;
 381     }
 382 #ifdef DEBUG_ALLOC2
 383     printf("alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n",
 384             size,
 385             (s->free_cluster_index - nb_clusters) << s->cluster_bits);
 386 #endif
 387     return (s->free_cluster_index - nb_clusters) << s->cluster_bits;
 388 }
 389
 390 int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size)
 391 {
 392     int64_t offset;
 393
 394     offset = alloc_clusters_noref(bs, size);
 395     update_refcount(bs, offset, size, 1);
 396     return offset;
 397 }
 398
 399 /* only used to allocate compressed sectors. We try to allocate
 400    contiguous sectors. size must be <= cluster_size */
 401 int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
 402 {
 403     BDRVQcowState *s = bs->opaque;
 404     int64_t offset, cluster_offset;
 405     int free_in_cluster;
 406
 407     assert(size > 0 && size <= s->cluster_size);
 408     if (s->free_byte_offset == 0) {
 409         s->free_byte_offset = qcow2_alloc_clusters(bs, s->cluster_size);
 410     }
 411  redo:
 412     free_in_cluster = s->cluster_size -
 413         (s->free_byte_offset & (s->cluster_size - 1));
 414     if (size <= free_in_cluster) {
 415         /* enough space in current cluster */
 416         offset = s->free_byte_offset;
 417         s->free_byte_offset += size;
 418         free_in_cluster -= size;
 419         if (free_in_cluster == 0)
 420             s->free_byte_offset = 0;
 421         if ((offset & (s->cluster_size - 1)) != 0)
 422             update_cluster_refcount(bs, offset >> s->cluster_bits, 1);
 423     } else {
 424         offset = qcow2_alloc_clusters(bs, s->cluster_size);
 425         cluster_offset = s->free_byte_offset & ~(s->cluster_size - 1);
 426         if ((cluster_offset + s->cluster_size) == offset) {
 427             /* we are lucky: contiguous data */
 428             offset = s->free_byte_offset;
 429             update_cluster_refcount(bs, offset >> s->cluster_bits, 1);
 430             s->free_byte_offset += size;
 431         } else {
 432             s->free_byte_offset = offset;
 433             goto redo;
 434         }
 435     }
 436     return offset;
 437 }
 438
 439 void qcow2_free_clusters(BlockDriverState *bs,
 440                           int64_t offset, int64_t size)
 441 {
 442     update_refcount(bs, offset, size, -1);
 443 }
 444
 445 /*
 446  * free_any_clusters
 447  *
 448  * free clusters according to its type: compressed or not
 449  *
 450  */
 451
 452 void qcow2_free_any_clusters(BlockDriverState *bs,
 453     uint64_t cluster_offset, int nb_clusters)
 454 {
 455     BDRVQcowState *s = bs->opaque;
 456
 457     /* free the cluster */
 458
 459     if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
 460         int nb_csectors;
 461         nb_csectors = ((cluster_offset >> s->csize_shift) &
 462                        s->csize_mask) + 1;
 463         qcow2_free_clusters(bs,
 464             (cluster_offset & s->cluster_offset_mask) & ~511,
 465             nb_csectors * 512);
 466         return;
 467     }
 468
 469     qcow2_free_clusters(bs, cluster_offset, nb_clusters << s->cluster_bits);
 470
 471     return;
 472 }
 473
 474
 475
 476 /*********************************************************/
 477 /* snapshots and image creation */
 478
 479
 480
 481 void qcow2_create_refcount_update(QCowCreateState *s, int64_t offset,
 482     int64_t size)
 483 {
 484     int refcount;
 485     int64_t start, last, cluster_offset;
 486     uint16_t *p;
 487
 488     start = offset & ~(s->cluster_size - 1);
 489     last = (offset + size - 1)  & ~(s->cluster_size - 1);
 490     for(cluster_offset = start; cluster_offset <= last;
 491         cluster_offset += s->cluster_size) {
 492         p = &s->refcount_block[cluster_offset >> s->cluster_bits];
 493         refcount = be16_to_cpu(*p);
 494         refcount++;
 495         *p = cpu_to_be16(refcount);
 496     }
 497 }
 498
 499 /* update the refcounts of snapshots and the copied flag */
 500 int qcow2_update_snapshot_refcount(BlockDriverState *bs,
 501     int64_t l1_table_offset, int l1_size, int addend)
 502 {
 503     BDRVQcowState *s = bs->opaque;
 504     uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, l1_allocated;
 505     int64_t old_offset, old_l2_offset;
 506     int l2_size, i, j, l1_modified, l2_modified, nb_csectors, refcount;
 507
 508     qcow2_l2_cache_reset(bs);
 509     cache_refcount_updates = 1;
 510
 511     l2_table = NULL;
 512     l1_table = NULL;
 513     l1_size2 = l1_size * sizeof(uint64_t);
 514     if (l1_table_offset != s->l1_table_offset) {
 515         if (l1_size2 != 0) {
 516             l1_table = qemu_mallocz(align_offset(l1_size2, 512));
 517         } else {
 518             l1_table = NULL;
 519         }
 520         l1_allocated = 1;
 521         if (bdrv_pread(s->hd, l1_table_offset,
 522                        l1_table, l1_size2) != l1_size2)
 523             goto fail;
 524         for(i = 0;i < l1_size; i++)
 525             be64_to_cpus(&l1_table[i]);
 526     } else {
 527         assert(l1_size == s->l1_size);
 528         l1_table = s->l1_table;
 529         l1_allocated = 0;
 530     }
 531
 532     l2_size = s->l2_size * sizeof(uint64_t);
 533     l2_table = qemu_malloc(l2_size);
 534     l1_modified = 0;
 535     for(i = 0; i < l1_size; i++) {
 536         l2_offset = l1_table[i];
 537         if (l2_offset) {
 538             old_l2_offset = l2_offset;
 539             l2_offset &= ~QCOW_OFLAG_COPIED;
 540             l2_modified = 0;
 541             if (bdrv_pread(s->hd, l2_offset, l2_table, l2_size) != l2_size)
 542                 goto fail;
 543             for(j = 0; j < s->l2_size; j++) {
 544                 offset = be64_to_cpu(l2_table[j]);
 545                 if (offset != 0) {
 546                     old_offset = offset;
 547                     offset &= ~QCOW_OFLAG_COPIED;
 548                     if (offset & QCOW_OFLAG_COMPRESSED) {
 549                         nb_csectors = ((offset >> s->csize_shift) &
 550                                        s->csize_mask) + 1;
 551                         if (addend != 0)
 552                             update_refcount(bs, (offset & s->cluster_offset_mask) & ~511,
 553                                             nb_csectors * 512, addend);
 554                         /* compressed clusters are never modified */
 555                         refcount = 2;
 556                     } else {
 557                         if (addend != 0) {
 558                             refcount = update_cluster_refcount(bs, offset >> s->cluster_bits, addend);
 559                         } else {
 560                             refcount = get_refcount(bs, offset >> s->cluster_bits);
 561                         }
 562                     }
 563
 564                     if (refcount == 1) {
 565                         offset |= QCOW_OFLAG_COPIED;
 566                     }
 567                     if (offset != old_offset) {
 568                         l2_table[j] = cpu_to_be64(offset);
 569                         l2_modified = 1;
 570                     }
 571                 }
 572             }
 573             if (l2_modified) {
 574                 if (bdrv_pwrite(s->hd,
 575                                 l2_offset, l2_table, l2_size) != l2_size)
 576                     goto fail;
 577             }
 578
 579             if (addend != 0) {
 580                 refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend);
 581             } else {
 582                 refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
 583             }
 584             if (refcount == 1) {
 585                 l2_offset |= QCOW_OFLAG_COPIED;
 586             }
 587             if (l2_offset != old_l2_offset) {
 588                 l1_table[i] = l2_offset;
 589                 l1_modified = 1;
 590             }
 591         }
 592     }
 593     if (l1_modified) {
 594         for(i = 0; i < l1_size; i++)
 595             cpu_to_be64s(&l1_table[i]);
 596         if (bdrv_pwrite(s->hd, l1_table_offset, l1_table,
 597                         l1_size2) != l1_size2)
 598             goto fail;
 599         for(i = 0; i < l1_size; i++)
 600             be64_to_cpus(&l1_table[i]);
 601     }
 602     if (l1_allocated)
 603         qemu_free(l1_table);
 604     qemu_free(l2_table);
 605     cache_refcount_updates = 0;
 606     write_refcount_block(s);
 607     return 0;
 608  fail:
 609     if (l1_allocated)
 610         qemu_free(l1_table);
 611     qemu_free(l2_table);
 612     cache_refcount_updates = 0;
 613     write_refcount_block(s);
 614     return -EIO;
 615 }
 616
 617
 618
 619
 620 /*********************************************************/
 621 /* refcount checking functions */
 622
 623
 624
 625 /*
 626  * Increases the refcount for a range of clusters in a given refcount table.
 627  * This is used to construct a temporary refcount table out of L1 and L2 tables
 628  * which can be compared the the refcount table saved in the image.
 629  *
 630  * Returns the number of errors in the image that were found
 631  */
 632 static int inc_refcounts(BlockDriverState *bs,
 633                           uint16_t *refcount_table,
 634                           int refcount_table_size,
 635                           int64_t offset, int64_t size)
 636 {
 637     BDRVQcowState *s = bs->opaque;
 638     int64_t start, last, cluster_offset;
 639     int k;
 640     int errors = 0;
 641
 642     if (size <= 0)
 643         return 0;
 644
 645     start = offset & ~(s->cluster_size - 1);
 646     last = (offset + size - 1) & ~(s->cluster_size - 1);
 647     for(cluster_offset = start; cluster_offset <= last;
 648         cluster_offset += s->cluster_size) {
 649         k = cluster_offset >> s->cluster_bits;
 650         if (k < 0 || k >= refcount_table_size) {
 651             fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n",
 652                 cluster_offset);
 653             errors++;
 654         } else {
 655             if (++refcount_table[k] == 0) {
 656                 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64
 657                     "\n", cluster_offset);
 658                 errors++;
 659             }
 660         }
 661     }
 662
 663     return errors;
 664 }
 665
 666 /*
 667  * Increases the refcount in the given refcount table for the all clusters
 668  * referenced in the L2 table. While doing so, performs some checks on L2
 669  * entries.
 670  *
 671  * Returns the number of errors found by the checks or -errno if an internal
 672  * error occurred.
 673  */
 674 static int check_refcounts_l2(BlockDriverState *bs,
 675     uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset,
 676     int check_copied)
 677 {
 678     BDRVQcowState *s = bs->opaque;
 679     uint64_t *l2_table, offset;
 680     int i, l2_size, nb_csectors, refcount;
 681     int errors = 0;
 682
 683     /* Read L2 table from disk */
 684     l2_size = s->l2_size * sizeof(uint64_t);
 685     l2_table = qemu_malloc(l2_size);
 686
 687     if (bdrv_pread(s->hd, l2_offset, l2_table, l2_size) != l2_size)
 688         goto fail;
 689
 690     /* Do the actual checks */
 691     for(i = 0; i < s->l2_size; i++) {
 692         offset = be64_to_cpu(l2_table[i]);
 693         if (offset != 0) {
 694             if (offset & QCOW_OFLAG_COMPRESSED) {
 695                 /* Compressed clusters don't have QCOW_OFLAG_COPIED */
 696                 if (offset & QCOW_OFLAG_COPIED) {
 697                     fprintf(stderr, "ERROR: cluster %" PRId64 ": "
 698                         "copied flag must never be set for compressed "
 699                         "clusters\n", offset >> s->cluster_bits);
 700                     offset &= ~QCOW_OFLAG_COPIED;
 701                     errors++;
 702                 }
 703
 704                 /* Mark cluster as used */
 705                 nb_csectors = ((offset >> s->csize_shift) &
 706                                s->csize_mask) + 1;
 707                 offset &= s->cluster_offset_mask;
 708                 errors += inc_refcounts(bs, refcount_table,
 709                               refcount_table_size,
 710                               offset & ~511, nb_csectors * 512);
 711             } else {
 712                 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
 713                 if (check_copied) {
 714                     uint64_t entry = offset;
 715                     offset &= ~QCOW_OFLAG_COPIED;
 716                     refcount = get_refcount(bs, offset >> s->cluster_bits);
 717                     if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) {
 718                         fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
 719                             PRIx64 " refcount=%d\n", entry, refcount);
 720                         errors++;
 721                     }
 722                 }
 723
 724                 /* Mark cluster as used */
 725                 offset &= ~QCOW_OFLAG_COPIED;
 726                 errors += inc_refcounts(bs, refcount_table,
 727                               refcount_table_size,
 728                               offset, s->cluster_size);
 729
 730                 /* Correct offsets are cluster aligned */
 731                 if (offset & (s->cluster_size - 1)) {
 732                     fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
 733                         "properly aligned; L2 entry corrupted.\n", offset);
 734                     errors++;
 735                 }
 736             }
 737         }
 738     }
 739
 740     qemu_free(l2_table);
 741     return errors;
 742
 743 fail:
 744     fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
 745     qemu_free(l2_table);
 746     return -EIO;
 747 }
 748
 749 /*
 750  * Increases the refcount for the L1 table, its L2 tables and all referenced
 751  * clusters in the given refcount table. While doing so, performs some checks
 752  * on L1 and L2 entries.
 753  *
 754  * Returns the number of errors found by the checks or -errno if an internal
 755  * error occurred.
 756  */
 757 static int check_refcounts_l1(BlockDriverState *bs,
 758                               uint16_t *refcount_table,
 759                               int refcount_table_size,
 760                               int64_t l1_table_offset, int l1_size,
 761                               int check_copied)
 762 {
 763     BDRVQcowState *s = bs->opaque;
 764     uint64_t *l1_table, l2_offset, l1_size2;
 765     int i, refcount, ret;
 766     int errors = 0;
 767
 768     l1_size2 = l1_size * sizeof(uint64_t);
 769
 770     /* Mark L1 table as used */
 771     errors += inc_refcounts(bs, refcount_table, refcount_table_size,
 772                   l1_table_offset, l1_size2);
 773
 774     /* Read L1 table entries from disk */
 775     if (l1_size2 == 0) {
 776         l1_table = NULL;
 777     } else {
 778         l1_table = qemu_malloc(l1_size2);
 779         if (bdrv_pread(s->hd, l1_table_offset,
 780                        l1_table, l1_size2) != l1_size2)
 781             goto fail;
 782         for(i = 0;i < l1_size; i++)
 783             be64_to_cpus(&l1_table[i]);
 784     }
 785
 786     /* Do the actual checks */
 787     for(i = 0; i < l1_size; i++) {
 788         l2_offset = l1_table[i];
 789         if (l2_offset) {
 790             /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
 791             if (check_copied) {
 792                 refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED)
 793                     >> s->cluster_bits);
 794                 if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) {
 795                     fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64
 796                         " refcount=%d\n", l2_offset, refcount);
 797                     errors++;
 798                 }
 799             }
 800
 801             /* Mark L2 table as used */
 802             l2_offset &= ~QCOW_OFLAG_COPIED;
 803             errors += inc_refcounts(bs, refcount_table,
 804                           refcount_table_size,
 805                           l2_offset,
 806                           s->cluster_size);
 807
 808             /* L2 tables are cluster aligned */
 809             if (l2_offset & (s->cluster_size - 1)) {
 810                 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "
 811                     "cluster aligned; L1 entry corrupted\n", l2_offset);
 812                 errors++;
 813             }
 814
 815             /* Process and check L2 entries */
 816             ret = check_refcounts_l2(bs, refcount_table, refcount_table_size,
 817                 l2_offset, check_copied);
 818             if (ret < 0) {
 819                 goto fail;
 820             }
 821             errors += ret;
 822         }
 823     }
 824     qemu_free(l1_table);
 825     return errors;
 826
 827 fail:
 828     fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
 829     qemu_free(l1_table);
 830     return -EIO;
 831 }
 832
 833 /*
 834  * Checks an image for refcount consistency.
 835  *
 836  * Returns 0 if no errors are found, the number of errors in case the image is
 837  * detected as corrupted, and -errno when an internal error occured.
 838  */
 839 int qcow2_check_refcounts(BlockDriverState *bs)
 840 {
 841     BDRVQcowState *s = bs->opaque;
 842     int64_t size;
 843     int nb_clusters, refcount1, refcount2, i;
 844     QCowSnapshot *sn;
 845     uint16_t *refcount_table;
 846     int ret, errors = 0;
 847
 848     size = bdrv_getlength(s->hd);
 849     nb_clusters = size_to_clusters(s, size);
 850     refcount_table = qemu_mallocz(nb_clusters * sizeof(uint16_t));
 851
 852     /* header */
 853     errors += inc_refcounts(bs, refcount_table, nb_clusters,
 854                   0, s->cluster_size);
 855
 856     /* current L1 table */
 857     ret = check_refcounts_l1(bs, refcount_table, nb_clusters,
 858                        s->l1_table_offset, s->l1_size, 1);
 859     if (ret < 0) {
 860         return ret;
 861     }
 862     errors += ret;
 863
 864     /* snapshots */
 865     for(i = 0; i < s->nb_snapshots; i++) {
 866         sn = s->snapshots + i;
 867         check_refcounts_l1(bs, refcount_table, nb_clusters,
 868                            sn->l1_table_offset, sn->l1_size, 0);
 869     }
 870     errors += inc_refcounts(bs, refcount_table, nb_clusters,
 871                   s->snapshots_offset, s->snapshots_size);
 872
 873     /* refcount data */
 874     errors += inc_refcounts(bs, refcount_table, nb_clusters,
 875                   s->refcount_table_offset,
 876                   s->refcount_table_size * sizeof(uint64_t));
 877     for(i = 0; i < s->refcount_table_size; i++) {
 878         int64_t offset;
 879         offset = s->refcount_table[i];
 880         if (offset != 0) {
 881             errors += inc_refcounts(bs, refcount_table, nb_clusters,
 882                           offset, s->cluster_size);
 883         }
 884     }
 885
 886     /* compare ref counts */
 887     for(i = 0; i < nb_clusters; i++) {
 888         refcount1 = get_refcount(bs, i);
 889         refcount2 = refcount_table[i];
 890         if (refcount1 != refcount2) {
 891             fprintf(stderr, "ERROR cluster %d refcount=%d reference=%d\n",
 892                    i, refcount1, refcount2);
 893             errors++;
 894         }
 895     }
 896
 897     qemu_free(refcount_table);
 898
 899     return errors;
 900 }
 901