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 = g_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 g_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 = g_malloc0(blocks_clusters * s->cluster_size); 327 uint64_t *new_table = g_malloc0(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 g_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 g_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 g_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 = 0, nb_csectors, refcount; 709 int ret; 710 bool old_l2_writethrough, old_refcount_writethrough; 711 712 /* Switch caches to writeback mode during update */ 713 old_l2_writethrough = 714 qcow2_cache_set_writethrough(bs, s->l2_table_cache, false); 715 old_refcount_writethrough = 716 qcow2_cache_set_writethrough(bs, s->refcount_block_cache, false); 717 718 l2_table = NULL; 719 l1_table = NULL; 720 l1_size2 = l1_size * sizeof(uint64_t); 721 if (l1_table_offset != s->l1_table_offset) { 722 if (l1_size2 != 0) { 723 l1_table = g_malloc0(align_offset(l1_size2, 512)); 724 } else { 725 l1_table = NULL; 726 } 727 l1_allocated = 1; 728 if (bdrv_pread(bs->file, l1_table_offset, 729 l1_table, l1_size2) != l1_size2) 730 { 731 ret = -EIO; 732 goto fail; 733 } 734 735 for(i = 0;i < l1_size; i++) 736 be64_to_cpus(&l1_table[i]); 737 } else { 738 assert(l1_size == s->l1_size); 739 l1_table = s->l1_table; 740 l1_allocated = 0; 741 } 742 743 for(i = 0; i < l1_size; i++) { 744 l2_offset = l1_table[i]; 745 if (l2_offset) { 746 old_l2_offset = l2_offset; 747 l2_offset &= ~QCOW_OFLAG_COPIED; 748 749 ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, 750 (void**) &l2_table); 751 if (ret < 0) { 752 goto fail; 753 } 754 755 for(j = 0; j < s->l2_size; j++) { 756 offset = be64_to_cpu(l2_table[j]); 757 if (offset != 0) { 758 old_offset = offset; 759 offset &= ~QCOW_OFLAG_COPIED; 760 if (offset & QCOW_OFLAG_COMPRESSED) { 761 nb_csectors = ((offset >> s->csize_shift) & 762 s->csize_mask) + 1; 763 if (addend != 0) { 764 int ret; 765 ret = update_refcount(bs, 766 (offset & s->cluster_offset_mask) & ~511, 767 nb_csectors * 512, addend); 768 if (ret < 0) { 769 goto fail; 770 } 771 772 /* TODO Flushing once for the whole function should 773 * be enough */ 774 bdrv_flush(bs->file); 775 } 776 /* compressed clusters are never modified */ 777 refcount = 2; 778 } else { 779 if (addend != 0) { 780 refcount = update_cluster_refcount(bs, offset >> s->cluster_bits, addend); 781 } else { 782 refcount = get_refcount(bs, offset >> s->cluster_bits); 783 } 784 785 if (refcount < 0) { 786 ret = -EIO; 787 goto fail; 788 } 789 } 790 791 if (refcount == 1) { 792 offset |= QCOW_OFLAG_COPIED; 793 } 794 if (offset != old_offset) { 795 if (addend > 0) { 796 qcow2_cache_set_dependency(bs, s->l2_table_cache, 797 s->refcount_block_cache); 798 } 799 l2_table[j] = cpu_to_be64(offset); 800 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); 801 } 802 } 803 } 804 805 ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 806 if (ret < 0) { 807 goto fail; 808 } 809 810 811 if (addend != 0) { 812 refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend); 813 } else { 814 refcount = get_refcount(bs, l2_offset >> s->cluster_bits); 815 } 816 if (refcount < 0) { 817 ret = -EIO; 818 goto fail; 819 } else if (refcount == 1) { 820 l2_offset |= QCOW_OFLAG_COPIED; 821 } 822 if (l2_offset != old_l2_offset) { 823 l1_table[i] = l2_offset; 824 l1_modified = 1; 825 } 826 } 827 } 828 829 ret = 0; 830 fail: 831 if (l2_table) { 832 qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 833 } 834 835 /* Enable writethrough cache mode again */ 836 qcow2_cache_set_writethrough(bs, s->l2_table_cache, old_l2_writethrough); 837 qcow2_cache_set_writethrough(bs, s->refcount_block_cache, 838 old_refcount_writethrough); 839 840 if (l1_modified) { 841 for(i = 0; i < l1_size; i++) 842 cpu_to_be64s(&l1_table[i]); 843 if (bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table, 844 l1_size2) < 0) 845 goto fail; 846 for(i = 0; i < l1_size; i++) 847 be64_to_cpus(&l1_table[i]); 848 } 849 if (l1_allocated) 850 g_free(l1_table); 851 return ret; 852 } 853 854 855 856 857 /*********************************************************/ 858 /* refcount checking functions */ 859 860 861 862 /* 863 * Increases the refcount for a range of clusters in a given refcount table. 864 * This is used to construct a temporary refcount table out of L1 and L2 tables 865 * which can be compared the the refcount table saved in the image. 866 * 867 * Modifies the number of errors in res. 868 */ 869 static void inc_refcounts(BlockDriverState *bs, 870 BdrvCheckResult *res, 871 uint16_t *refcount_table, 872 int refcount_table_size, 873 int64_t offset, int64_t size) 874 { 875 BDRVQcowState *s = bs->opaque; 876 int64_t start, last, cluster_offset; 877 int k; 878 879 if (size <= 0) 880 return; 881 882 start = offset & ~(s->cluster_size - 1); 883 last = (offset + size - 1) & ~(s->cluster_size - 1); 884 for(cluster_offset = start; cluster_offset <= last; 885 cluster_offset += s->cluster_size) { 886 k = cluster_offset >> s->cluster_bits; 887 if (k < 0) { 888 fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n", 889 cluster_offset); 890 res->corruptions++; 891 } else if (k >= refcount_table_size) { 892 fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after " 893 "the end of the image file, can't properly check refcounts.\n", 894 cluster_offset); 895 res->check_errors++; 896 } else { 897 if (++refcount_table[k] == 0) { 898 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64 899 "\n", cluster_offset); 900 res->corruptions++; 901 } 902 } 903 } 904 } 905 906 /* 907 * Increases the refcount in the given refcount table for the all clusters 908 * referenced in the L2 table. While doing so, performs some checks on L2 909 * entries. 910 * 911 * Returns the number of errors found by the checks or -errno if an internal 912 * error occurred. 913 */ 914 static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res, 915 uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset, 916 int check_copied) 917 { 918 BDRVQcowState *s = bs->opaque; 919 uint64_t *l2_table, offset; 920 int i, l2_size, nb_csectors, refcount; 921 922 /* Read L2 table from disk */ 923 l2_size = s->l2_size * sizeof(uint64_t); 924 l2_table = g_malloc(l2_size); 925 926 if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size) 927 goto fail; 928 929 /* Do the actual checks */ 930 for(i = 0; i < s->l2_size; i++) { 931 offset = be64_to_cpu(l2_table[i]); 932 if (offset != 0) { 933 if (offset & QCOW_OFLAG_COMPRESSED) { 934 /* Compressed clusters don't have QCOW_OFLAG_COPIED */ 935 if (offset & QCOW_OFLAG_COPIED) { 936 fprintf(stderr, "ERROR: cluster %" PRId64 ": " 937 "copied flag must never be set for compressed " 938 "clusters\n", offset >> s->cluster_bits); 939 offset &= ~QCOW_OFLAG_COPIED; 940 res->corruptions++; 941 } 942 943 /* Mark cluster as used */ 944 nb_csectors = ((offset >> s->csize_shift) & 945 s->csize_mask) + 1; 946 offset &= s->cluster_offset_mask; 947 inc_refcounts(bs, res, refcount_table, refcount_table_size, 948 offset & ~511, nb_csectors * 512); 949 } else { 950 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ 951 if (check_copied) { 952 uint64_t entry = offset; 953 offset &= ~QCOW_OFLAG_COPIED; 954 refcount = get_refcount(bs, offset >> s->cluster_bits); 955 if (refcount < 0) { 956 fprintf(stderr, "Can't get refcount for offset %" 957 PRIx64 ": %s\n", entry, strerror(-refcount)); 958 goto fail; 959 } 960 if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) { 961 fprintf(stderr, "ERROR OFLAG_COPIED: offset=%" 962 PRIx64 " refcount=%d\n", entry, refcount); 963 res->corruptions++; 964 } 965 } 966 967 /* Mark cluster as used */ 968 offset &= ~QCOW_OFLAG_COPIED; 969 inc_refcounts(bs, res, refcount_table,refcount_table_size, 970 offset, s->cluster_size); 971 972 /* Correct offsets are cluster aligned */ 973 if (offset & (s->cluster_size - 1)) { 974 fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not " 975 "properly aligned; L2 entry corrupted.\n", offset); 976 res->corruptions++; 977 } 978 } 979 } 980 } 981 982 g_free(l2_table); 983 return 0; 984 985 fail: 986 fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n"); 987 g_free(l2_table); 988 return -EIO; 989 } 990 991 /* 992 * Increases the refcount for the L1 table, its L2 tables and all referenced 993 * clusters in the given refcount table. While doing so, performs some checks 994 * on L1 and L2 entries. 995 * 996 * Returns the number of errors found by the checks or -errno if an internal 997 * error occurred. 998 */ 999 static int check_refcounts_l1(BlockDriverState *bs, 1000 BdrvCheckResult *res, 1001 uint16_t *refcount_table, 1002 int refcount_table_size, 1003 int64_t l1_table_offset, int l1_size, 1004 int check_copied) 1005 { 1006 BDRVQcowState *s = bs->opaque; 1007 uint64_t *l1_table, l2_offset, l1_size2; 1008 int i, refcount, ret; 1009 1010 l1_size2 = l1_size * sizeof(uint64_t); 1011 1012 /* Mark L1 table as used */ 1013 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1014 l1_table_offset, l1_size2); 1015 1016 /* Read L1 table entries from disk */ 1017 if (l1_size2 == 0) { 1018 l1_table = NULL; 1019 } else { 1020 l1_table = g_malloc(l1_size2); 1021 if (bdrv_pread(bs->file, l1_table_offset, 1022 l1_table, l1_size2) != l1_size2) 1023 goto fail; 1024 for(i = 0;i < l1_size; i++) 1025 be64_to_cpus(&l1_table[i]); 1026 } 1027 1028 /* Do the actual checks */ 1029 for(i = 0; i < l1_size; i++) { 1030 l2_offset = l1_table[i]; 1031 if (l2_offset) { 1032 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ 1033 if (check_copied) { 1034 refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED) 1035 >> s->cluster_bits); 1036 if (refcount < 0) { 1037 fprintf(stderr, "Can't get refcount for l2_offset %" 1038 PRIx64 ": %s\n", l2_offset, strerror(-refcount)); 1039 goto fail; 1040 } 1041 if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) { 1042 fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64 1043 " refcount=%d\n", l2_offset, refcount); 1044 res->corruptions++; 1045 } 1046 } 1047 1048 /* Mark L2 table as used */ 1049 l2_offset &= ~QCOW_OFLAG_COPIED; 1050 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1051 l2_offset, s->cluster_size); 1052 1053 /* L2 tables are cluster aligned */ 1054 if (l2_offset & (s->cluster_size - 1)) { 1055 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not " 1056 "cluster aligned; L1 entry corrupted\n", l2_offset); 1057 res->corruptions++; 1058 } 1059 1060 /* Process and check L2 entries */ 1061 ret = check_refcounts_l2(bs, res, refcount_table, 1062 refcount_table_size, l2_offset, check_copied); 1063 if (ret < 0) { 1064 goto fail; 1065 } 1066 } 1067 } 1068 g_free(l1_table); 1069 return 0; 1070 1071 fail: 1072 fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n"); 1073 res->check_errors++; 1074 g_free(l1_table); 1075 return -EIO; 1076 } 1077 1078 /* 1079 * Checks an image for refcount consistency. 1080 * 1081 * Returns 0 if no errors are found, the number of errors in case the image is 1082 * detected as corrupted, and -errno when an internal error occurred. 1083 */ 1084 int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res) 1085 { 1086 BDRVQcowState *s = bs->opaque; 1087 int64_t size; 1088 int nb_clusters, refcount1, refcount2, i; 1089 QCowSnapshot *sn; 1090 uint16_t *refcount_table; 1091 int ret; 1092 1093 size = bdrv_getlength(bs->file); 1094 nb_clusters = size_to_clusters(s, size); 1095 refcount_table = g_malloc0(nb_clusters * sizeof(uint16_t)); 1096 1097 /* header */ 1098 inc_refcounts(bs, res, refcount_table, nb_clusters, 1099 0, s->cluster_size); 1100 1101 /* current L1 table */ 1102 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1103 s->l1_table_offset, s->l1_size, 1); 1104 if (ret < 0) { 1105 goto fail; 1106 } 1107 1108 /* snapshots */ 1109 for(i = 0; i < s->nb_snapshots; i++) { 1110 sn = s->snapshots + i; 1111 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1112 sn->l1_table_offset, sn->l1_size, 0); 1113 if (ret < 0) { 1114 goto fail; 1115 } 1116 } 1117 inc_refcounts(bs, res, refcount_table, nb_clusters, 1118 s->snapshots_offset, s->snapshots_size); 1119 1120 /* refcount data */ 1121 inc_refcounts(bs, res, refcount_table, nb_clusters, 1122 s->refcount_table_offset, 1123 s->refcount_table_size * sizeof(uint64_t)); 1124 1125 for(i = 0; i < s->refcount_table_size; i++) { 1126 uint64_t offset, cluster; 1127 offset = s->refcount_table[i]; 1128 cluster = offset >> s->cluster_bits; 1129 1130 /* Refcount blocks are cluster aligned */ 1131 if (offset & (s->cluster_size - 1)) { 1132 fprintf(stderr, "ERROR refcount block %d is not " 1133 "cluster aligned; refcount table entry corrupted\n", i); 1134 res->corruptions++; 1135 continue; 1136 } 1137 1138 if (cluster >= nb_clusters) { 1139 fprintf(stderr, "ERROR refcount block %d is outside image\n", i); 1140 res->corruptions++; 1141 continue; 1142 } 1143 1144 if (offset != 0) { 1145 inc_refcounts(bs, res, refcount_table, nb_clusters, 1146 offset, s->cluster_size); 1147 if (refcount_table[cluster] != 1) { 1148 fprintf(stderr, "ERROR refcount block %d refcount=%d\n", 1149 i, refcount_table[cluster]); 1150 res->corruptions++; 1151 } 1152 } 1153 } 1154 1155 /* compare ref counts */ 1156 for(i = 0; i < nb_clusters; i++) { 1157 refcount1 = get_refcount(bs, i); 1158 if (refcount1 < 0) { 1159 fprintf(stderr, "Can't get refcount for cluster %d: %s\n", 1160 i, strerror(-refcount1)); 1161 res->check_errors++; 1162 continue; 1163 } 1164 1165 refcount2 = refcount_table[i]; 1166 if (refcount1 != refcount2) { 1167 fprintf(stderr, "%s cluster %d refcount=%d reference=%d\n", 1168 refcount1 < refcount2 ? "ERROR" : "Leaked", 1169 i, refcount1, refcount2); 1170 if (refcount1 < refcount2) { 1171 res->corruptions++; 1172 } else { 1173 res->leaks++; 1174 } 1175 } 1176 } 1177 1178 ret = 0; 1179 1180 fail: 1181 g_free(refcount_table); 1182 1183 return ret; 1184 } 1185 1186