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 QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
  31                             int64_t offset, int64_t length,
  32                             int addend);
  33
  34
  35 /*********************************************************/
  36 /* refcount handling */
  37
  38 int qcow2_refcount_init(BlockDriverState *bs)
  39 {
  40     BDRVQcowState *s = bs->opaque;
  41     int ret, refcount_table_size2, i;
  42
  43     refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);
  44     s->refcount_table = qemu_malloc(refcount_table_size2);
  45     if (s->refcount_table_size > 0) {
  46         BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_LOAD);
  47         ret = bdrv_pread(bs->file, s->refcount_table_offset,
  48                          s->refcount_table, refcount_table_size2);
  49         if (ret != refcount_table_size2)
  50             goto fail;
  51         for(i = 0; i < s->refcount_table_size; i++)
  52             be64_to_cpus(&s->refcount_table[i]);
  53     }
  54     return 0;
  55  fail:
  56     return -ENOMEM;
  57 }
  58
  59 void qcow2_refcount_close(BlockDriverState *bs)
  60 {
  61     BDRVQcowState *s = bs->opaque;
  62     qemu_free(s->refcount_table);
  63 }
  64
  65
  66 static int load_refcount_block(BlockDriverState *bs,
  67                                int64_t refcount_block_offset,
  68                                void **refcount_block)
  69 {
  70     BDRVQcowState *s = bs->opaque;
  71     int ret;
  72
  73     BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_LOAD);
  74     ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset,
  75         refcount_block);
  76
  77     return ret;
  78 }
  79
  80 /*
  81  * Returns the refcount of the cluster given by its index. Any non-negative
  82  * return value is the refcount of the cluster, negative values are -errno
  83  * and indicate an error.
  84  */
  85 static int get_refcount(BlockDriverState *bs, int64_t cluster_index)
  86 {
  87     BDRVQcowState *s = bs->opaque;
  88     int refcount_table_index, block_index;
  89     int64_t refcount_block_offset;
  90     int ret;
  91     uint16_t *refcount_block;
  92     uint16_t refcount;
  93
  94     refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
  95     if (refcount_table_index >= s->refcount_table_size)
  96         return 0;
  97     refcount_block_offset = s->refcount_table[refcount_table_index];
  98     if (!refcount_block_offset)
  99         return 0;
 100
 101     ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset,
 102         (void**) &refcount_block);
 103     if (ret < 0) {
 104         return ret;
 105     }
 106
 107     block_index = cluster_index &
 108         ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
 109     refcount = be16_to_cpu(refcount_block[block_index]);
 110
 111     ret = qcow2_cache_put(bs, s->refcount_block_cache,
 112         (void**) &refcount_block);
 113     if (ret < 0) {
 114         return ret;
 115     }
 116
 117     return refcount;
 118 }
 119
 120 /*
 121  * Rounds the refcount table size up to avoid growing the table for each single
 122  * refcount block that is allocated.
 123  */
 124 static unsigned int next_refcount_table_size(BDRVQcowState *s,
 125     unsigned int min_size)
 126 {
 127     unsigned int min_clusters = (min_size >> (s->cluster_bits - 3)) + 1;
 128     unsigned int refcount_table_clusters =
 129         MAX(1, s->refcount_table_size >> (s->cluster_bits - 3));
 130
 131     while (min_clusters > refcount_table_clusters) {
 132         refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2;
 133     }
 134
 135     return refcount_table_clusters << (s->cluster_bits - 3);
 136 }
 137
 138
 139 /* Checks if two offsets are described by the same refcount block */
 140 static int in_same_refcount_block(BDRVQcowState *s, uint64_t offset_a,
 141     uint64_t offset_b)
 142 {
 143     uint64_t block_a = offset_a >> (2 * s->cluster_bits - REFCOUNT_SHIFT);
 144     uint64_t block_b = offset_b >> (2 * s->cluster_bits - REFCOUNT_SHIFT);
 145
 146     return (block_a == block_b);
 147 }
 148
 149 /*
 150  * Loads a refcount block. If it doesn't exist yet, it is allocated first
 151  * (including growing the refcount table if needed).
 152  *
 153  * Returns 0 on success or -errno in error case
 154  */
 155 static int alloc_refcount_block(BlockDriverState *bs,
 156     int64_t cluster_index, uint16_t **refcount_block)
 157 {
 158     BDRVQcowState *s = bs->opaque;
 159     unsigned int refcount_table_index;
 160     int ret;
 161
 162     BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC);
 163
 164     /* Find the refcount block for the given cluster */
 165     refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
 166
 167     if (refcount_table_index < s->refcount_table_size) {
 168
 169         uint64_t refcount_block_offset =
 170             s->refcount_table[refcount_table_index];
 171
 172         /* If it's already there, we're done */
 173         if (refcount_block_offset) {
 174              return load_refcount_block(bs, refcount_block_offset,
 175                  (void**) refcount_block);
 176         }
 177     }
 178
 179     /*
 180      * If we came here, we need to allocate something. Something is at least
 181      * a cluster for the new refcount block. It may also include a new refcount
 182      * table if the old refcount table is too small.
 183      *
 184      * Note that allocating clusters here needs some special care:
 185      *
 186      * - We can't use the normal qcow2_alloc_clusters(), it would try to
 187      *   increase the refcount and very likely we would end up with an endless
 188      *   recursion. Instead we must place the refcount blocks in a way that
 189      *   they can describe them themselves.
 190      *
 191      * - We need to consider that at this point we are inside update_refcounts
 192      *   and doing the initial refcount increase. This means that some clusters
 193      *   have already been allocated by the caller, but their refcount isn't
 194      *   accurate yet. free_cluster_index tells us where this allocation ends
 195      *   as long as we don't overwrite it by freeing clusters.
 196      *
 197      * - alloc_clusters_noref and qcow2_free_clusters may load a different
 198      *   refcount block into the cache
 199      */
 200
 201     *refcount_block = NULL;
 202
 203     /* We write to the refcount table, so we might depend on L2 tables */
 204     qcow2_cache_flush(bs, s->l2_table_cache);
 205
 206     /* Allocate the refcount block itself and mark it as used */
 207     int64_t new_block = alloc_clusters_noref(bs, s->cluster_size);
 208     if (new_block < 0) {
 209         return new_block;
 210     }
 211
 212 #ifdef DEBUG_ALLOC2
 213     fprintf(stderr, "qcow2: Allocate refcount block %d for %" PRIx64
 214         " at %" PRIx64 "\n",
 215         refcount_table_index, cluster_index << s->cluster_bits, new_block);
 216 #endif
 217
 218     if (in_same_refcount_block(s, new_block, cluster_index << s->cluster_bits)) {
 219         /* Zero the new refcount block before updating it */
 220         ret = qcow2_cache_get_empty(bs, s->refcount_block_cache, new_block,
 221             (void**) refcount_block);
 222         if (ret < 0) {
 223             goto fail_block;
 224         }
 225
 226         memset(*refcount_block, 0, s->cluster_size);
 227
 228         /* The block describes itself, need to update the cache */
 229         int block_index = (new_block >> s->cluster_bits) &
 230             ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
 231         (*refcount_block)[block_index] = cpu_to_be16(1);
 232     } else {
 233         /* Described somewhere else. This can recurse at most twice before we
 234          * arrive at a block that describes itself. */
 235         ret = update_refcount(bs, new_block, s->cluster_size, 1);
 236         if (ret < 0) {
 237             goto fail_block;
 238         }
 239
 240         bdrv_flush(bs->file);
 241
 242         /* Initialize the new refcount block only after updating its refcount,
 243          * update_refcount uses the refcount cache itself */
 244         ret = qcow2_cache_get_empty(bs, s->refcount_block_cache, new_block,
 245             (void**) refcount_block);
 246         if (ret < 0) {
 247             goto fail_block;
 248         }
 249
 250         memset(*refcount_block, 0, s->cluster_size);
 251     }
 252
 253     /* Now the new refcount block needs to be written to disk */
 254     BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE);
 255     qcow2_cache_entry_mark_dirty(s->refcount_block_cache, *refcount_block);
 256     ret = qcow2_cache_flush(bs, s->refcount_block_cache);
 257     if (ret < 0) {
 258         goto fail_block;
 259     }
 260
 261     /* If the refcount table is big enough, just hook the block up there */
 262     if (refcount_table_index < s->refcount_table_size) {
 263         uint64_t data64 = cpu_to_be64(new_block);
 264         BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_HOOKUP);
 265         ret = bdrv_pwrite_sync(bs->file,
 266             s->refcount_table_offset + refcount_table_index * sizeof(uint64_t),
 267             &data64, sizeof(data64));
 268         if (ret < 0) {
 269             goto fail_block;
 270         }
 271
 272         s->refcount_table[refcount_table_index] = new_block;
 273         return 0;
 274     }
 275
 276     ret = qcow2_cache_put(bs, s->refcount_block_cache, (void**) refcount_block);
 277     if (ret < 0) {
 278         goto fail_block;
 279     }
 280
 281     /*
 282      * If we come here, we need to grow the refcount table. Again, a new
 283      * refcount table needs some space and we can't simply allocate to avoid
 284      * endless recursion.
 285      *
 286      * Therefore let's grab new refcount blocks at the end of the image, which
 287      * will describe themselves and the new refcount table. This way we can
 288      * reference them only in the new table and do the switch to the new
 289      * refcount table at once without producing an inconsistent state in
 290      * between.
 291      */
 292     BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_GROW);
 293
 294     /* Calculate the number of refcount blocks needed so far */
 295     uint64_t refcount_block_clusters = 1 << (s->cluster_bits - REFCOUNT_SHIFT);
 296     uint64_t blocks_used = (s->free_cluster_index +
 297         refcount_block_clusters - 1) / refcount_block_clusters;
 298
 299     /* And now we need at least one block more for the new metadata */
 300     uint64_t table_size = next_refcount_table_size(s, blocks_used + 1);
 301     uint64_t last_table_size;
 302     uint64_t blocks_clusters;
 303     do {
 304         uint64_t table_clusters = size_to_clusters(s, table_size);
 305         blocks_clusters = 1 +
 306             ((table_clusters + refcount_block_clusters - 1)
 307             / refcount_block_clusters);
 308         uint64_t meta_clusters = table_clusters + blocks_clusters;
 309
 310         last_table_size = table_size;
 311         table_size = next_refcount_table_size(s, blocks_used +
 312             ((meta_clusters + refcount_block_clusters - 1)
 313             / refcount_block_clusters));
 314
 315     } while (last_table_size != table_size);
 316
 317 #ifdef DEBUG_ALLOC2
 318     fprintf(stderr, "qcow2: Grow refcount table %" PRId32 " => %" PRId64 "\n",
 319         s->refcount_table_size, table_size);
 320 #endif
 321
 322     /* Create the new refcount table and blocks */
 323     uint64_t meta_offset = (blocks_used * refcount_block_clusters) *
 324         s->cluster_size;
 325     uint64_t table_offset = meta_offset + blocks_clusters * s->cluster_size;
 326     uint16_t *new_blocks = qemu_mallocz(blocks_clusters * s->cluster_size);
 327     uint64_t *new_table = qemu_mallocz(table_size * sizeof(uint64_t));
 328
 329     assert(meta_offset >= (s->free_cluster_index * s->cluster_size));
 330
 331     /* Fill the new refcount table */
 332     memcpy(new_table, s->refcount_table,
 333         s->refcount_table_size * sizeof(uint64_t));
 334     new_table[refcount_table_index] = new_block;
 335
 336     int i;
 337     for (i = 0; i < blocks_clusters; i++) {
 338         new_table[blocks_used + i] = meta_offset + (i * s->cluster_size);
 339     }
 340
 341     /* Fill the refcount blocks */
 342     uint64_t table_clusters = size_to_clusters(s, table_size * sizeof(uint64_t));
 343     int block = 0;
 344     for (i = 0; i < table_clusters + blocks_clusters; i++) {
 345         new_blocks[block++] = cpu_to_be16(1);
 346     }
 347
 348     /* Write refcount blocks to disk */
 349     BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_BLOCKS);
 350     ret = bdrv_pwrite_sync(bs->file, meta_offset, new_blocks,
 351         blocks_clusters * s->cluster_size);
 352     qemu_free(new_blocks);
 353     if (ret < 0) {
 354         goto fail_table;
 355     }
 356
 357     /* Write refcount table to disk */
 358     for(i = 0; i < table_size; i++) {
 359         cpu_to_be64s(&new_table[i]);
 360     }
 361
 362     BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_TABLE);
 363     ret = bdrv_pwrite_sync(bs->file, table_offset, new_table,
 364         table_size * sizeof(uint64_t));
 365     if (ret < 0) {
 366         goto fail_table;
 367     }
 368
 369     for(i = 0; i < table_size; i++) {
 370         cpu_to_be64s(&new_table[i]);
 371     }
 372
 373     /* Hook up the new refcount table in the qcow2 header */
 374     uint8_t data[12];
 375     cpu_to_be64w((uint64_t*)data, table_offset);
 376     cpu_to_be32w((uint32_t*)(data + 8), table_clusters);
 377     BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_SWITCH_TABLE);
 378     ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, refcount_table_offset),
 379         data, sizeof(data));
 380     if (ret < 0) {
 381         goto fail_table;
 382     }
 383
 384     /* And switch it in memory */
 385     uint64_t old_table_offset = s->refcount_table_offset;
 386     uint64_t old_table_size = s->refcount_table_size;
 387
 388     qemu_free(s->refcount_table);
 389     s->refcount_table = new_table;
 390     s->refcount_table_size = table_size;
 391     s->refcount_table_offset = table_offset;
 392
 393     /* Free old table. Remember, we must not change free_cluster_index */
 394     uint64_t old_free_cluster_index = s->free_cluster_index;
 395     qcow2_free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t));
 396     s->free_cluster_index = old_free_cluster_index;
 397
 398     ret = load_refcount_block(bs, new_block, (void**) refcount_block);
 399     if (ret < 0) {
 400         return ret;
 401     }
 402
 403     return new_block;
 404
 405 fail_table:
 406     qemu_free(new_table);
 407 fail_block:
 408     if (*refcount_block != NULL) {
 409         qcow2_cache_put(bs, s->refcount_block_cache, (void**) refcount_block);
 410     }
 411     return ret;
 412 }
 413
 414 /* XXX: cache several refcount block clusters ? */
 415 static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
 416     int64_t offset, int64_t length, int addend)
 417 {
 418     BDRVQcowState *s = bs->opaque;
 419     int64_t start, last, cluster_offset;
 420     uint16_t *refcount_block = NULL;
 421     int64_t old_table_index = -1;
 422     int ret;
 423
 424 #ifdef DEBUG_ALLOC2
 425     printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
 426            offset, length, addend);
 427 #endif
 428     if (length < 0) {
 429         return -EINVAL;
 430     } else if (length == 0) {
 431         return 0;
 432     }
 433
 434     if (addend < 0) {
 435         qcow2_cache_set_dependency(bs, s->refcount_block_cache,
 436             s->l2_table_cache);
 437     }
 438
 439     start = offset & ~(s->cluster_size - 1);
 440     last = (offset + length - 1) & ~(s->cluster_size - 1);
 441     for(cluster_offset = start; cluster_offset <= last;
 442         cluster_offset += s->cluster_size)
 443     {
 444         int block_index, refcount;
 445         int64_t cluster_index = cluster_offset >> s->cluster_bits;
 446         int64_t table_index =
 447             cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT);
 448
 449         /* Load the refcount block and allocate it if needed */
 450         if (table_index != old_table_index) {
 451             if (refcount_block) {
 452                 ret = qcow2_cache_put(bs, s->refcount_block_cache,
 453                     (void**) &refcount_block);
 454                 if (ret < 0) {
 455                     goto fail;
 456                 }
 457             }
 458
 459             ret = alloc_refcount_block(bs, cluster_index, &refcount_block);
 460             if (ret < 0) {
 461                 goto fail;
 462             }
 463         }
 464         old_table_index = table_index;
 465
 466         qcow2_cache_entry_mark_dirty(s->refcount_block_cache, refcount_block);
 467
 468         /* we can update the count and save it */
 469         block_index = cluster_index &
 470             ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1);
 471
 472         refcount = be16_to_cpu(refcount_block[block_index]);
 473         refcount += addend;
 474         if (refcount < 0 || refcount > 0xffff) {
 475             ret = -EINVAL;
 476             goto fail;
 477         }
 478         if (refcount == 0 && cluster_index < s->free_cluster_index) {
 479             s->free_cluster_index = cluster_index;
 480         }
 481         refcount_block[block_index] = cpu_to_be16(refcount);
 482     }
 483
 484     ret = 0;
 485 fail:
 486     /* Write last changed block to disk */
 487     if (refcount_block) {
 488         int wret;
 489         wret = qcow2_cache_put(bs, s->refcount_block_cache,
 490             (void**) &refcount_block);
 491         if (wret < 0) {
 492             return ret < 0 ? ret : wret;
 493         }
 494     }
 495
 496     /*
 497      * Try do undo any updates if an error is returned (This may succeed in
 498      * some cases like ENOSPC for allocating a new refcount block)
 499      */
 500     if (ret < 0) {
 501         int dummy;
 502         dummy = update_refcount(bs, offset, cluster_offset - offset, -addend);
 503         (void)dummy;
 504     }
 505
 506     return ret;
 507 }
 508
 509 /*
 510  * Increases or decreases the refcount of a given cluster by one.
 511  * addend must be 1 or -1.
 512  *
 513  * If the return value is non-negative, it is the new refcount of the cluster.
 514  * If it is negative, it is -errno and indicates an error.
 515  */
 516 static int update_cluster_refcount(BlockDriverState *bs,
 517                                    int64_t cluster_index,
 518                                    int addend)
 519 {
 520     BDRVQcowState *s = bs->opaque;
 521     int ret;
 522
 523     ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend);
 524     if (ret < 0) {
 525         return ret;
 526     }
 527
 528     bdrv_flush(bs->file);
 529
 530     return get_refcount(bs, cluster_index);
 531 }
 532
 533
 534
 535 /*********************************************************/
 536 /* cluster allocation functions */
 537
 538
 539
 540 /* return < 0 if error */
 541 static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size)
 542 {
 543     BDRVQcowState *s = bs->opaque;
 544     int i, nb_clusters, refcount;
 545
 546     nb_clusters = size_to_clusters(s, size);
 547 retry:
 548     for(i = 0; i < nb_clusters; i++) {
 549         int64_t next_cluster_index = s->free_cluster_index++;
 550         refcount = get_refcount(bs, next_cluster_index);
 551
 552         if (refcount < 0) {
 553             return refcount;
 554         } else if (refcount != 0) {
 555             goto retry;
 556         }
 557     }
 558 #ifdef DEBUG_ALLOC2
 559     printf("alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n",
 560             size,
 561             (s->free_cluster_index - nb_clusters) << s->cluster_bits);
 562 #endif
 563     return (s->free_cluster_index - nb_clusters) << s->cluster_bits;
 564 }
 565
 566 int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size)
 567 {
 568     int64_t offset;
 569     int ret;
 570
 571     BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC);
 572     offset = alloc_clusters_noref(bs, size);
 573     if (offset < 0) {
 574         return offset;
 575     }
 576
 577     ret = update_refcount(bs, offset, size, 1);
 578     if (ret < 0) {
 579         return ret;
 580     }
 581
 582     return offset;
 583 }
 584
 585 /* only used to allocate compressed sectors. We try to allocate
 586    contiguous sectors. size must be <= cluster_size */
 587 int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
 588 {
 589     BDRVQcowState *s = bs->opaque;
 590     int64_t offset, cluster_offset;
 591     int free_in_cluster;
 592
 593     BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES);
 594     assert(size > 0 && size <= s->cluster_size);
 595     if (s->free_byte_offset == 0) {
 596         s->free_byte_offset = qcow2_alloc_clusters(bs, s->cluster_size);
 597         if (s->free_byte_offset < 0) {
 598             return s->free_byte_offset;
 599         }
 600     }
 601  redo:
 602     free_in_cluster = s->cluster_size -
 603         (s->free_byte_offset & (s->cluster_size - 1));
 604     if (size <= free_in_cluster) {
 605         /* enough space in current cluster */
 606         offset = s->free_byte_offset;
 607         s->free_byte_offset += size;
 608         free_in_cluster -= size;
 609         if (free_in_cluster == 0)
 610             s->free_byte_offset = 0;
 611         if ((offset & (s->cluster_size - 1)) != 0)
 612             update_cluster_refcount(bs, offset >> s->cluster_bits, 1);
 613     } else {
 614         offset = qcow2_alloc_clusters(bs, s->cluster_size);
 615         if (offset < 0) {
 616             return offset;
 617         }
 618         cluster_offset = s->free_byte_offset & ~(s->cluster_size - 1);
 619         if ((cluster_offset + s->cluster_size) == offset) {
 620             /* we are lucky: contiguous data */
 621             offset = s->free_byte_offset;
 622             update_cluster_refcount(bs, offset >> s->cluster_bits, 1);
 623             s->free_byte_offset += size;
 624         } else {
 625             s->free_byte_offset = offset;
 626             goto redo;
 627         }
 628     }
 629
 630     bdrv_flush(bs->file);
 631     return offset;
 632 }
 633
 634 void qcow2_free_clusters(BlockDriverState *bs,
 635                           int64_t offset, int64_t size)
 636 {
 637     int ret;
 638
 639     BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_FREE);
 640     ret = update_refcount(bs, offset, size, -1);
 641     if (ret < 0) {
 642         fprintf(stderr, "qcow2_free_clusters failed: %s\n", strerror(-ret));
 643         /* TODO Remember the clusters to free them later and avoid leaking */
 644     }
 645 }
 646
 647 /*
 648  * free_any_clusters
 649  *
 650  * free clusters according to its type: compressed or not
 651  *
 652  */
 653
 654 void qcow2_free_any_clusters(BlockDriverState *bs,
 655     uint64_t cluster_offset, int nb_clusters)
 656 {
 657     BDRVQcowState *s = bs->opaque;
 658
 659     /* free the cluster */
 660
 661     if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
 662         int nb_csectors;
 663         nb_csectors = ((cluster_offset >> s->csize_shift) &
 664                        s->csize_mask) + 1;
 665         qcow2_free_clusters(bs,
 666             (cluster_offset & s->cluster_offset_mask) & ~511,
 667             nb_csectors * 512);
 668         return;
 669     }
 670
 671     qcow2_free_clusters(bs, cluster_offset, nb_clusters << s->cluster_bits);
 672
 673     return;
 674 }
 675
 676
 677
 678 /*********************************************************/
 679 /* snapshots and image creation */
 680
 681
 682
 683 void qcow2_create_refcount_update(QCowCreateState *s, int64_t offset,
 684     int64_t size)
 685 {
 686     int refcount;
 687     int64_t start, last, cluster_offset;
 688     uint16_t *p;
 689
 690     start = offset & ~(s->cluster_size - 1);
 691     last = (offset + size - 1)  & ~(s->cluster_size - 1);
 692     for(cluster_offset = start; cluster_offset <= last;
 693         cluster_offset += s->cluster_size) {
 694         p = &s->refcount_block[cluster_offset >> s->cluster_bits];
 695         refcount = be16_to_cpu(*p);
 696         refcount++;
 697         *p = cpu_to_be16(refcount);
 698     }
 699 }
 700
 701 /* update the refcounts of snapshots and the copied flag */
 702 int qcow2_update_snapshot_refcount(BlockDriverState *bs,
 703     int64_t l1_table_offset, int l1_size, int addend)
 704 {
 705     BDRVQcowState *s = bs->opaque;
 706     uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, l1_allocated;
 707     int64_t old_offset, old_l2_offset;
 708     int i, j, l1_modified, nb_csectors, refcount;
 709     int ret;
 710
 711     l2_table = NULL;
 712     l1_table = NULL;
 713     l1_size2 = l1_size * sizeof(uint64_t);
 714     if (l1_table_offset != s->l1_table_offset) {
 715         if (l1_size2 != 0) {
 716             l1_table = qemu_mallocz(align_offset(l1_size2, 512));
 717         } else {
 718             l1_table = NULL;
 719         }
 720         l1_allocated = 1;
 721         if (bdrv_pread(bs->file, l1_table_offset,
 722                        l1_table, l1_size2) != l1_size2)
 723             goto fail;
 724         for(i = 0;i < l1_size; i++)
 725             be64_to_cpus(&l1_table[i]);
 726     } else {
 727         assert(l1_size == s->l1_size);
 728         l1_table = s->l1_table;
 729         l1_allocated = 0;
 730     }
 731
 732     l1_modified = 0;
 733     for(i = 0; i < l1_size; i++) {
 734         l2_offset = l1_table[i];
 735         if (l2_offset) {
 736             old_l2_offset = l2_offset;
 737             l2_offset &= ~QCOW_OFLAG_COPIED;
 738
 739             ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
 740                 (void**) &l2_table);
 741             if (ret < 0) {
 742                 goto fail;
 743             }
 744
 745             for(j = 0; j < s->l2_size; j++) {
 746                 offset = be64_to_cpu(l2_table[j]);
 747                 if (offset != 0) {
 748                     old_offset = offset;
 749                     offset &= ~QCOW_OFLAG_COPIED;
 750                     if (offset & QCOW_OFLAG_COMPRESSED) {
 751                         nb_csectors = ((offset >> s->csize_shift) &
 752                                        s->csize_mask) + 1;
 753                         if (addend != 0) {
 754                             int ret;
 755                             ret = update_refcount(bs,
 756                                 (offset & s->cluster_offset_mask) & ~511,
 757                                 nb_csectors * 512, addend);
 758                             if (ret < 0) {
 759                                 goto fail;
 760                             }
 761
 762                             /* TODO Flushing once for the whole function should
 763                              * be enough */
 764                             bdrv_flush(bs->file);
 765                         }
 766                         /* compressed clusters are never modified */
 767                         refcount = 2;
 768                     } else {
 769                         if (addend != 0) {
 770                             refcount = update_cluster_refcount(bs, offset >> s->cluster_bits, addend);
 771                         } else {
 772                             refcount = get_refcount(bs, offset >> s->cluster_bits);
 773                         }
 774
 775                         if (refcount < 0) {
 776                             goto fail;
 777                         }
 778                     }
 779
 780                     if (refcount == 1) {
 781                         offset |= QCOW_OFLAG_COPIED;
 782                     }
 783                     if (offset != old_offset) {
 784                         if (addend > 0) {
 785                             qcow2_cache_set_dependency(bs, s->l2_table_cache,
 786                                 s->refcount_block_cache);
 787                         }
 788                         l2_table[j] = cpu_to_be64(offset);
 789                         qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
 790                     }
 791                 }
 792             }
 793
 794             ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
 795             if (ret < 0) {
 796                 goto fail;
 797             }
 798
 799
 800             if (addend != 0) {
 801                 refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend);
 802             } else {
 803                 refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
 804             }
 805             if (refcount < 0) {
 806                 goto fail;
 807             } else if (refcount == 1) {
 808                 l2_offset |= QCOW_OFLAG_COPIED;
 809             }
 810             if (l2_offset != old_l2_offset) {
 811                 l1_table[i] = l2_offset;
 812                 l1_modified = 1;
 813             }
 814         }
 815     }
 816     if (l1_modified) {
 817         for(i = 0; i < l1_size; i++)
 818             cpu_to_be64s(&l1_table[i]);
 819         if (bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table,
 820                         l1_size2) < 0)
 821             goto fail;
 822         for(i = 0; i < l1_size; i++)
 823             be64_to_cpus(&l1_table[i]);
 824     }
 825     if (l1_allocated)
 826         qemu_free(l1_table);
 827     return 0;
 828  fail:
 829     if (l2_table) {
 830         qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
 831     }
 832
 833     if (l1_allocated)
 834         qemu_free(l1_table);
 835     return -EIO;
 836 }
 837
 838
 839
 840
 841 /*********************************************************/
 842 /* refcount checking functions */
 843
 844
 845
 846 /*
 847  * Increases the refcount for a range of clusters in a given refcount table.
 848  * This is used to construct a temporary refcount table out of L1 and L2 tables
 849  * which can be compared the the refcount table saved in the image.
 850  *
 851  * Modifies the number of errors in res.
 852  */
 853 static void inc_refcounts(BlockDriverState *bs,
 854                           BdrvCheckResult *res,
 855                           uint16_t *refcount_table,
 856                           int refcount_table_size,
 857                           int64_t offset, int64_t size)
 858 {
 859     BDRVQcowState *s = bs->opaque;
 860     int64_t start, last, cluster_offset;
 861     int k;
 862
 863     if (size <= 0)
 864         return;
 865
 866     start = offset & ~(s->cluster_size - 1);
 867     last = (offset + size - 1) & ~(s->cluster_size - 1);
 868     for(cluster_offset = start; cluster_offset <= last;
 869         cluster_offset += s->cluster_size) {
 870         k = cluster_offset >> s->cluster_bits;
 871         if (k < 0) {
 872             fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n",
 873                 cluster_offset);
 874             res->corruptions++;
 875         } else if (k >= refcount_table_size) {
 876             fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after "
 877                 "the end of the image file, can't properly check refcounts.\n",
 878                 cluster_offset);
 879             res->check_errors++;
 880         } else {
 881             if (++refcount_table[k] == 0) {
 882                 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64
 883                     "\n", cluster_offset);
 884                 res->corruptions++;
 885             }
 886         }
 887     }
 888 }
 889
 890 /*
 891  * Increases the refcount in the given refcount table for the all clusters
 892  * referenced in the L2 table. While doing so, performs some checks on L2
 893  * entries.
 894  *
 895  * Returns the number of errors found by the checks or -errno if an internal
 896  * error occurred.
 897  */
 898 static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
 899     uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset,
 900     int check_copied)
 901 {
 902     BDRVQcowState *s = bs->opaque;
 903     uint64_t *l2_table, offset;
 904     int i, l2_size, nb_csectors, refcount;
 905
 906     /* Read L2 table from disk */
 907     l2_size = s->l2_size * sizeof(uint64_t);
 908     l2_table = qemu_malloc(l2_size);
 909
 910     if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size)
 911         goto fail;
 912
 913     /* Do the actual checks */
 914     for(i = 0; i < s->l2_size; i++) {
 915         offset = be64_to_cpu(l2_table[i]);
 916         if (offset != 0) {
 917             if (offset & QCOW_OFLAG_COMPRESSED) {
 918                 /* Compressed clusters don't have QCOW_OFLAG_COPIED */
 919                 if (offset & QCOW_OFLAG_COPIED) {
 920                     fprintf(stderr, "ERROR: cluster %" PRId64 ": "
 921                         "copied flag must never be set for compressed "
 922                         "clusters\n", offset >> s->cluster_bits);
 923                     offset &= ~QCOW_OFLAG_COPIED;
 924                     res->corruptions++;
 925                 }
 926
 927                 /* Mark cluster as used */
 928                 nb_csectors = ((offset >> s->csize_shift) &
 929                                s->csize_mask) + 1;
 930                 offset &= s->cluster_offset_mask;
 931                 inc_refcounts(bs, res, refcount_table, refcount_table_size,
 932                     offset & ~511, nb_csectors * 512);
 933             } else {
 934                 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
 935                 if (check_copied) {
 936                     uint64_t entry = offset;
 937                     offset &= ~QCOW_OFLAG_COPIED;
 938                     refcount = get_refcount(bs, offset >> s->cluster_bits);
 939                     if (refcount < 0) {
 940                         fprintf(stderr, "Can't get refcount for offset %"
 941                             PRIx64 ": %s\n", entry, strerror(-refcount));
 942                         goto fail;
 943                     }
 944                     if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) {
 945                         fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
 946                             PRIx64 " refcount=%d\n", entry, refcount);
 947                         res->corruptions++;
 948                     }
 949                 }
 950
 951                 /* Mark cluster as used */
 952                 offset &= ~QCOW_OFLAG_COPIED;
 953                 inc_refcounts(bs, res, refcount_table,refcount_table_size,
 954                     offset, s->cluster_size);
 955
 956                 /* Correct offsets are cluster aligned */
 957                 if (offset & (s->cluster_size - 1)) {
 958                     fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
 959                         "properly aligned; L2 entry corrupted.\n", offset);
 960                     res->corruptions++;
 961                 }
 962             }
 963         }
 964     }
 965
 966     qemu_free(l2_table);
 967     return 0;
 968
 969 fail:
 970     fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n");
 971     qemu_free(l2_table);
 972     return -EIO;
 973 }
 974
 975 /*
 976  * Increases the refcount for the L1 table, its L2 tables and all referenced
 977  * clusters in the given refcount table. While doing so, performs some checks
 978  * on L1 and L2 entries.
 979  *
 980  * Returns the number of errors found by the checks or -errno if an internal
 981  * error occurred.
 982  */
 983 static int check_refcounts_l1(BlockDriverState *bs,
 984                               BdrvCheckResult *res,
 985                               uint16_t *refcount_table,
 986                               int refcount_table_size,
 987                               int64_t l1_table_offset, int l1_size,
 988                               int check_copied)
 989 {
 990     BDRVQcowState *s = bs->opaque;
 991     uint64_t *l1_table, l2_offset, l1_size2;
 992     int i, refcount, ret;
 993
 994     l1_size2 = l1_size * sizeof(uint64_t);
 995
 996     /* Mark L1 table as used */
 997     inc_refcounts(bs, res, refcount_table, refcount_table_size,
 998         l1_table_offset, l1_size2);
 999
1000     /* Read L1 table entries from disk */
1001     if (l1_size2 == 0) {
1002         l1_table = NULL;
1003     } else {
1004         l1_table = qemu_malloc(l1_size2);
1005         if (bdrv_pread(bs->file, l1_table_offset,
1006                        l1_table, l1_size2) != l1_size2)
1007             goto fail;
1008         for(i = 0;i < l1_size; i++)
1009             be64_to_cpus(&l1_table[i]);
1010     }
1011
1012     /* Do the actual checks */
1013     for(i = 0; i < l1_size; i++) {
1014         l2_offset = l1_table[i];
1015         if (l2_offset) {
1016             /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
1017             if (check_copied) {
1018                 refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED)
1019                     >> s->cluster_bits);
1020                 if (refcount < 0) {
1021                     fprintf(stderr, "Can't get refcount for l2_offset %"
1022                         PRIx64 ": %s\n", l2_offset, strerror(-refcount));
1023                     goto fail;
1024                 }
1025                 if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) {
1026                     fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64
1027                         " refcount=%d\n", l2_offset, refcount);
1028                     res->corruptions++;
1029                 }
1030             }
1031
1032             /* Mark L2 table as used */
1033             l2_offset &= ~QCOW_OFLAG_COPIED;
1034             inc_refcounts(bs, res, refcount_table, refcount_table_size,
1035                 l2_offset, s->cluster_size);
1036
1037             /* L2 tables are cluster aligned */
1038             if (l2_offset & (s->cluster_size - 1)) {
1039                 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "
1040                     "cluster aligned; L1 entry corrupted\n", l2_offset);
1041                 res->corruptions++;
1042             }
1043
1044             /* Process and check L2 entries */
1045             ret = check_refcounts_l2(bs, res, refcount_table,
1046                 refcount_table_size, l2_offset, check_copied);
1047             if (ret < 0) {
1048                 goto fail;
1049             }
1050         }
1051     }
1052     qemu_free(l1_table);
1053     return 0;
1054
1055 fail:
1056     fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
1057     res->check_errors++;
1058     qemu_free(l1_table);
1059     return -EIO;
1060 }
1061
1062 /*
1063  * Checks an image for refcount consistency.
1064  *
1065  * Returns 0 if no errors are found, the number of errors in case the image is
1066  * detected as corrupted, and -errno when an internal error occurred.
1067  */
1068 int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res)
1069 {
1070     BDRVQcowState *s = bs->opaque;
1071     int64_t size;
1072     int nb_clusters, refcount1, refcount2, i;
1073     QCowSnapshot *sn;
1074     uint16_t *refcount_table;
1075     int ret;
1076
1077     size = bdrv_getlength(bs->file);
1078     nb_clusters = size_to_clusters(s, size);
1079     refcount_table = qemu_mallocz(nb_clusters * sizeof(uint16_t));
1080
1081     /* header */
1082     inc_refcounts(bs, res, refcount_table, nb_clusters,
1083         0, s->cluster_size);
1084
1085     /* current L1 table */
1086     ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
1087                        s->l1_table_offset, s->l1_size, 1);
1088     if (ret < 0) {
1089         return ret;
1090     }
1091
1092     /* snapshots */
1093     for(i = 0; i < s->nb_snapshots; i++) {
1094         sn = s->snapshots + i;
1095         ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
1096             sn->l1_table_offset, sn->l1_size, 0);
1097         if (ret < 0) {
1098             return ret;
1099         }
1100     }
1101     inc_refcounts(bs, res, refcount_table, nb_clusters,
1102         s->snapshots_offset, s->snapshots_size);
1103
1104     /* refcount data */
1105     inc_refcounts(bs, res, refcount_table, nb_clusters,
1106         s->refcount_table_offset,
1107         s->refcount_table_size * sizeof(uint64_t));
1108
1109     for(i = 0; i < s->refcount_table_size; i++) {
1110         uint64_t offset, cluster;
1111         offset = s->refcount_table[i];
1112         cluster = offset >> s->cluster_bits;
1113
1114         /* Refcount blocks are cluster aligned */
1115         if (offset & (s->cluster_size - 1)) {
1116             fprintf(stderr, "ERROR refcount block %d is not "
1117                 "cluster aligned; refcount table entry corrupted\n", i);
1118             res->corruptions++;
1119             continue;
1120         }
1121
1122         if (cluster >= nb_clusters) {
1123             fprintf(stderr, "ERROR refcount block %d is outside image\n", i);
1124             res->corruptions++;
1125             continue;
1126         }
1127
1128         if (offset != 0) {
1129             inc_refcounts(bs, res, refcount_table, nb_clusters,
1130                 offset, s->cluster_size);
1131             if (refcount_table[cluster] != 1) {
1132                 fprintf(stderr, "ERROR refcount block %d refcount=%d\n",
1133                     i, refcount_table[cluster]);
1134                 res->corruptions++;
1135             }
1136         }
1137     }
1138
1139     /* compare ref counts */
1140     for(i = 0; i < nb_clusters; i++) {
1141         refcount1 = get_refcount(bs, i);
1142         if (refcount1 < 0) {
1143             fprintf(stderr, "Can't get refcount for cluster %d: %s\n",
1144                 i, strerror(-refcount1));
1145             res->check_errors++;
1146             continue;
1147         }
1148
1149         refcount2 = refcount_table[i];
1150         if (refcount1 != refcount2) {
1151             fprintf(stderr, "%s cluster %d refcount=%d reference=%d\n",
1152                    refcount1 < refcount2 ? "ERROR" : "Leaked",
1153                    i, refcount1, refcount2);
1154             if (refcount1 < refcount2) {
1155                 res->corruptions++;
1156             } else {
1157                 res->leaks++;
1158             }
1159         }
1160     }
1161
1162     qemu_free(refcount_table);
1163
1164     return 0;
1165 }
1166