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] & REFT_OFFSET_MASK; 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 = 305 size_to_clusters(s, table_size * sizeof(uint64_t)); 306 blocks_clusters = 1 + 307 ((table_clusters + refcount_block_clusters - 1) 308 / refcount_block_clusters); 309 uint64_t meta_clusters = table_clusters + blocks_clusters; 310 311 last_table_size = table_size; 312 table_size = next_refcount_table_size(s, blocks_used + 313 ((meta_clusters + refcount_block_clusters - 1) 314 / refcount_block_clusters)); 315 316 } while (last_table_size != table_size); 317 318 #ifdef DEBUG_ALLOC2 319 fprintf(stderr, "qcow2: Grow refcount table %" PRId32 " => %" PRId64 "\n", 320 s->refcount_table_size, table_size); 321 #endif 322 323 /* Create the new refcount table and blocks */ 324 uint64_t meta_offset = (blocks_used * refcount_block_clusters) * 325 s->cluster_size; 326 uint64_t table_offset = meta_offset + blocks_clusters * s->cluster_size; 327 uint16_t *new_blocks = g_malloc0(blocks_clusters * s->cluster_size); 328 uint64_t *new_table = g_malloc0(table_size * sizeof(uint64_t)); 329 330 assert(meta_offset >= (s->free_cluster_index * s->cluster_size)); 331 332 /* Fill the new refcount table */ 333 memcpy(new_table, s->refcount_table, 334 s->refcount_table_size * sizeof(uint64_t)); 335 new_table[refcount_table_index] = new_block; 336 337 int i; 338 for (i = 0; i < blocks_clusters; i++) { 339 new_table[blocks_used + i] = meta_offset + (i * s->cluster_size); 340 } 341 342 /* Fill the refcount blocks */ 343 uint64_t table_clusters = size_to_clusters(s, table_size * sizeof(uint64_t)); 344 int block = 0; 345 for (i = 0; i < table_clusters + blocks_clusters; i++) { 346 new_blocks[block++] = cpu_to_be16(1); 347 } 348 349 /* Write refcount blocks to disk */ 350 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_BLOCKS); 351 ret = bdrv_pwrite_sync(bs->file, meta_offset, new_blocks, 352 blocks_clusters * s->cluster_size); 353 g_free(new_blocks); 354 if (ret < 0) { 355 goto fail_table; 356 } 357 358 /* Write refcount table to disk */ 359 for(i = 0; i < table_size; i++) { 360 cpu_to_be64s(&new_table[i]); 361 } 362 363 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_TABLE); 364 ret = bdrv_pwrite_sync(bs->file, table_offset, new_table, 365 table_size * sizeof(uint64_t)); 366 if (ret < 0) { 367 goto fail_table; 368 } 369 370 for(i = 0; i < table_size; i++) { 371 be64_to_cpus(&new_table[i]); 372 } 373 374 /* Hook up the new refcount table in the qcow2 header */ 375 uint8_t data[12]; 376 cpu_to_be64w((uint64_t*)data, table_offset); 377 cpu_to_be32w((uint32_t*)(data + 8), table_clusters); 378 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_SWITCH_TABLE); 379 ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, refcount_table_offset), 380 data, sizeof(data)); 381 if (ret < 0) { 382 goto fail_table; 383 } 384 385 /* And switch it in memory */ 386 uint64_t old_table_offset = s->refcount_table_offset; 387 uint64_t old_table_size = s->refcount_table_size; 388 389 g_free(s->refcount_table); 390 s->refcount_table = new_table; 391 s->refcount_table_size = table_size; 392 s->refcount_table_offset = table_offset; 393 394 /* Free old table. Remember, we must not change free_cluster_index */ 395 uint64_t old_free_cluster_index = s->free_cluster_index; 396 qcow2_free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t)); 397 s->free_cluster_index = old_free_cluster_index; 398 399 ret = load_refcount_block(bs, new_block, (void**) refcount_block); 400 if (ret < 0) { 401 return ret; 402 } 403 404 return 0; 405 406 fail_table: 407 g_free(new_table); 408 fail_block: 409 if (*refcount_block != NULL) { 410 qcow2_cache_put(bs, s->refcount_block_cache, (void**) refcount_block); 411 } 412 return ret; 413 } 414 415 /* XXX: cache several refcount block clusters ? */ 416 static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, 417 int64_t offset, int64_t length, int addend) 418 { 419 BDRVQcowState *s = bs->opaque; 420 int64_t start, last, cluster_offset; 421 uint16_t *refcount_block = NULL; 422 int64_t old_table_index = -1; 423 int ret; 424 425 #ifdef DEBUG_ALLOC2 426 fprintf(stderr, "update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n", 427 offset, length, addend); 428 #endif 429 if (length < 0) { 430 return -EINVAL; 431 } else if (length == 0) { 432 return 0; 433 } 434 435 if (addend < 0) { 436 qcow2_cache_set_dependency(bs, s->refcount_block_cache, 437 s->l2_table_cache); 438 } 439 440 start = offset & ~(s->cluster_size - 1); 441 last = (offset + length - 1) & ~(s->cluster_size - 1); 442 for(cluster_offset = start; cluster_offset <= last; 443 cluster_offset += s->cluster_size) 444 { 445 int block_index, refcount; 446 int64_t cluster_index = cluster_offset >> s->cluster_bits; 447 int64_t table_index = 448 cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT); 449 450 /* Load the refcount block and allocate it if needed */ 451 if (table_index != old_table_index) { 452 if (refcount_block) { 453 ret = qcow2_cache_put(bs, s->refcount_block_cache, 454 (void**) &refcount_block); 455 if (ret < 0) { 456 goto fail; 457 } 458 } 459 460 ret = alloc_refcount_block(bs, cluster_index, &refcount_block); 461 if (ret < 0) { 462 goto fail; 463 } 464 } 465 old_table_index = table_index; 466 467 qcow2_cache_entry_mark_dirty(s->refcount_block_cache, refcount_block); 468 469 /* we can update the count and save it */ 470 block_index = cluster_index & 471 ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); 472 473 refcount = be16_to_cpu(refcount_block[block_index]); 474 refcount += addend; 475 if (refcount < 0 || refcount > 0xffff) { 476 ret = -EINVAL; 477 goto fail; 478 } 479 if (refcount == 0 && cluster_index < s->free_cluster_index) { 480 s->free_cluster_index = cluster_index; 481 } 482 refcount_block[block_index] = cpu_to_be16(refcount); 483 } 484 485 ret = 0; 486 fail: 487 /* Write last changed block to disk */ 488 if (refcount_block) { 489 int wret; 490 wret = qcow2_cache_put(bs, s->refcount_block_cache, 491 (void**) &refcount_block); 492 if (wret < 0) { 493 return ret < 0 ? ret : wret; 494 } 495 } 496 497 /* 498 * Try do undo any updates if an error is returned (This may succeed in 499 * some cases like ENOSPC for allocating a new refcount block) 500 */ 501 if (ret < 0) { 502 int dummy; 503 dummy = update_refcount(bs, offset, cluster_offset - offset, -addend); 504 (void)dummy; 505 } 506 507 return ret; 508 } 509 510 /* 511 * Increases or decreases the refcount of a given cluster by one. 512 * addend must be 1 or -1. 513 * 514 * If the return value is non-negative, it is the new refcount of the cluster. 515 * If it is negative, it is -errno and indicates an error. 516 */ 517 static int update_cluster_refcount(BlockDriverState *bs, 518 int64_t cluster_index, 519 int addend) 520 { 521 BDRVQcowState *s = bs->opaque; 522 int ret; 523 524 ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend); 525 if (ret < 0) { 526 return ret; 527 } 528 529 bdrv_flush(bs->file); 530 531 return get_refcount(bs, cluster_index); 532 } 533 534 535 536 /*********************************************************/ 537 /* cluster allocation functions */ 538 539 540 541 /* return < 0 if error */ 542 static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size) 543 { 544 BDRVQcowState *s = bs->opaque; 545 int i, nb_clusters, refcount; 546 547 nb_clusters = size_to_clusters(s, size); 548 retry: 549 for(i = 0; i < nb_clusters; i++) { 550 int64_t next_cluster_index = s->free_cluster_index++; 551 refcount = get_refcount(bs, next_cluster_index); 552 553 if (refcount < 0) { 554 return refcount; 555 } else if (refcount != 0) { 556 goto retry; 557 } 558 } 559 #ifdef DEBUG_ALLOC2 560 fprintf(stderr, "alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n", 561 size, 562 (s->free_cluster_index - nb_clusters) << s->cluster_bits); 563 #endif 564 return (s->free_cluster_index - nb_clusters) << s->cluster_bits; 565 } 566 567 int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size) 568 { 569 int64_t offset; 570 int ret; 571 572 BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC); 573 offset = alloc_clusters_noref(bs, size); 574 if (offset < 0) { 575 return offset; 576 } 577 578 ret = update_refcount(bs, offset, size, 1); 579 if (ret < 0) { 580 return ret; 581 } 582 583 return offset; 584 } 585 586 int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, 587 int nb_clusters) 588 { 589 BDRVQcowState *s = bs->opaque; 590 uint64_t cluster_index; 591 uint64_t old_free_cluster_index; 592 int i, refcount, ret; 593 594 /* Check how many clusters there are free */ 595 cluster_index = offset >> s->cluster_bits; 596 for(i = 0; i < nb_clusters; i++) { 597 refcount = get_refcount(bs, cluster_index++); 598 599 if (refcount < 0) { 600 return refcount; 601 } else if (refcount != 0) { 602 break; 603 } 604 } 605 606 /* And then allocate them */ 607 old_free_cluster_index = s->free_cluster_index; 608 s->free_cluster_index = cluster_index + i; 609 610 ret = update_refcount(bs, offset, i << s->cluster_bits, 1); 611 if (ret < 0) { 612 return ret; 613 } 614 615 s->free_cluster_index = old_free_cluster_index; 616 617 return i; 618 } 619 620 /* only used to allocate compressed sectors. We try to allocate 621 contiguous sectors. size must be <= cluster_size */ 622 int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) 623 { 624 BDRVQcowState *s = bs->opaque; 625 int64_t offset, cluster_offset; 626 int free_in_cluster; 627 628 BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES); 629 assert(size > 0 && size <= s->cluster_size); 630 if (s->free_byte_offset == 0) { 631 offset = qcow2_alloc_clusters(bs, s->cluster_size); 632 if (offset < 0) { 633 return offset; 634 } 635 s->free_byte_offset = offset; 636 } 637 redo: 638 free_in_cluster = s->cluster_size - 639 (s->free_byte_offset & (s->cluster_size - 1)); 640 if (size <= free_in_cluster) { 641 /* enough space in current cluster */ 642 offset = s->free_byte_offset; 643 s->free_byte_offset += size; 644 free_in_cluster -= size; 645 if (free_in_cluster == 0) 646 s->free_byte_offset = 0; 647 if ((offset & (s->cluster_size - 1)) != 0) 648 update_cluster_refcount(bs, offset >> s->cluster_bits, 1); 649 } else { 650 offset = qcow2_alloc_clusters(bs, s->cluster_size); 651 if (offset < 0) { 652 return offset; 653 } 654 cluster_offset = s->free_byte_offset & ~(s->cluster_size - 1); 655 if ((cluster_offset + s->cluster_size) == offset) { 656 /* we are lucky: contiguous data */ 657 offset = s->free_byte_offset; 658 update_cluster_refcount(bs, offset >> s->cluster_bits, 1); 659 s->free_byte_offset += size; 660 } else { 661 s->free_byte_offset = offset; 662 goto redo; 663 } 664 } 665 666 bdrv_flush(bs->file); 667 return offset; 668 } 669 670 void qcow2_free_clusters(BlockDriverState *bs, 671 int64_t offset, int64_t size) 672 { 673 int ret; 674 675 BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_FREE); 676 ret = update_refcount(bs, offset, size, -1); 677 if (ret < 0) { 678 fprintf(stderr, "qcow2_free_clusters failed: %s\n", strerror(-ret)); 679 /* TODO Remember the clusters to free them later and avoid leaking */ 680 } 681 } 682 683 /* 684 * Free a cluster using its L2 entry (handles clusters of all types, e.g. 685 * normal cluster, compressed cluster, etc.) 686 */ 687 void qcow2_free_any_clusters(BlockDriverState *bs, 688 uint64_t l2_entry, int nb_clusters) 689 { 690 BDRVQcowState *s = bs->opaque; 691 692 switch (qcow2_get_cluster_type(l2_entry)) { 693 case QCOW2_CLUSTER_COMPRESSED: 694 { 695 int nb_csectors; 696 nb_csectors = ((l2_entry >> s->csize_shift) & 697 s->csize_mask) + 1; 698 qcow2_free_clusters(bs, 699 (l2_entry & s->cluster_offset_mask) & ~511, 700 nb_csectors * 512); 701 } 702 break; 703 case QCOW2_CLUSTER_NORMAL: 704 qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK, 705 nb_clusters << s->cluster_bits); 706 break; 707 case QCOW2_CLUSTER_UNALLOCATED: 708 case QCOW2_CLUSTER_ZERO: 709 break; 710 default: 711 abort(); 712 } 713 } 714 715 716 717 /*********************************************************/ 718 /* snapshots and image creation */ 719 720 721 722 /* update the refcounts of snapshots and the copied flag */ 723 int qcow2_update_snapshot_refcount(BlockDriverState *bs, 724 int64_t l1_table_offset, int l1_size, int addend) 725 { 726 BDRVQcowState *s = bs->opaque; 727 uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, l1_allocated; 728 int64_t old_offset, old_l2_offset; 729 int i, j, l1_modified = 0, nb_csectors, refcount; 730 int ret; 731 732 l2_table = NULL; 733 l1_table = NULL; 734 l1_size2 = l1_size * sizeof(uint64_t); 735 736 /* WARNING: qcow2_snapshot_goto relies on this function not using the 737 * l1_table_offset when it is the current s->l1_table_offset! Be careful 738 * when changing this! */ 739 if (l1_table_offset != s->l1_table_offset) { 740 if (l1_size2 != 0) { 741 l1_table = g_malloc0(align_offset(l1_size2, 512)); 742 } else { 743 l1_table = NULL; 744 } 745 l1_allocated = 1; 746 if (bdrv_pread(bs->file, l1_table_offset, 747 l1_table, l1_size2) != l1_size2) 748 { 749 ret = -EIO; 750 goto fail; 751 } 752 753 for(i = 0;i < l1_size; i++) 754 be64_to_cpus(&l1_table[i]); 755 } else { 756 assert(l1_size == s->l1_size); 757 l1_table = s->l1_table; 758 l1_allocated = 0; 759 } 760 761 for(i = 0; i < l1_size; i++) { 762 l2_offset = l1_table[i]; 763 if (l2_offset) { 764 old_l2_offset = l2_offset; 765 l2_offset &= L1E_OFFSET_MASK; 766 767 ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, 768 (void**) &l2_table); 769 if (ret < 0) { 770 goto fail; 771 } 772 773 for(j = 0; j < s->l2_size; j++) { 774 offset = be64_to_cpu(l2_table[j]); 775 if (offset != 0) { 776 old_offset = offset; 777 offset &= ~QCOW_OFLAG_COPIED; 778 if (offset & QCOW_OFLAG_COMPRESSED) { 779 nb_csectors = ((offset >> s->csize_shift) & 780 s->csize_mask) + 1; 781 if (addend != 0) { 782 int ret; 783 ret = update_refcount(bs, 784 (offset & s->cluster_offset_mask) & ~511, 785 nb_csectors * 512, addend); 786 if (ret < 0) { 787 goto fail; 788 } 789 790 /* TODO Flushing once for the whole function should 791 * be enough */ 792 bdrv_flush(bs->file); 793 } 794 /* compressed clusters are never modified */ 795 refcount = 2; 796 } else { 797 uint64_t cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits; 798 if (addend != 0) { 799 refcount = update_cluster_refcount(bs, cluster_index, addend); 800 } else { 801 refcount = get_refcount(bs, cluster_index); 802 } 803 804 if (refcount < 0) { 805 ret = -EIO; 806 goto fail; 807 } 808 } 809 810 if (refcount == 1) { 811 offset |= QCOW_OFLAG_COPIED; 812 } 813 if (offset != old_offset) { 814 if (addend > 0) { 815 qcow2_cache_set_dependency(bs, s->l2_table_cache, 816 s->refcount_block_cache); 817 } 818 l2_table[j] = cpu_to_be64(offset); 819 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); 820 } 821 } 822 } 823 824 ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 825 if (ret < 0) { 826 goto fail; 827 } 828 829 830 if (addend != 0) { 831 refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend); 832 } else { 833 refcount = get_refcount(bs, l2_offset >> s->cluster_bits); 834 } 835 if (refcount < 0) { 836 ret = -EIO; 837 goto fail; 838 } else if (refcount == 1) { 839 l2_offset |= QCOW_OFLAG_COPIED; 840 } 841 if (l2_offset != old_l2_offset) { 842 l1_table[i] = l2_offset; 843 l1_modified = 1; 844 } 845 } 846 } 847 848 ret = 0; 849 fail: 850 if (l2_table) { 851 qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 852 } 853 854 /* Update L1 only if it isn't deleted anyway (addend = -1) */ 855 if (addend >= 0 && l1_modified) { 856 for(i = 0; i < l1_size; i++) 857 cpu_to_be64s(&l1_table[i]); 858 if (bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table, 859 l1_size2) < 0) 860 goto fail; 861 for(i = 0; i < l1_size; i++) 862 be64_to_cpus(&l1_table[i]); 863 } 864 if (l1_allocated) 865 g_free(l1_table); 866 return ret; 867 } 868 869 870 871 872 /*********************************************************/ 873 /* refcount checking functions */ 874 875 876 877 /* 878 * Increases the refcount for a range of clusters in a given refcount table. 879 * This is used to construct a temporary refcount table out of L1 and L2 tables 880 * which can be compared the the refcount table saved in the image. 881 * 882 * Modifies the number of errors in res. 883 */ 884 static void inc_refcounts(BlockDriverState *bs, 885 BdrvCheckResult *res, 886 uint16_t *refcount_table, 887 int refcount_table_size, 888 int64_t offset, int64_t size) 889 { 890 BDRVQcowState *s = bs->opaque; 891 int64_t start, last, cluster_offset; 892 int k; 893 894 if (size <= 0) 895 return; 896 897 start = offset & ~(s->cluster_size - 1); 898 last = (offset + size - 1) & ~(s->cluster_size - 1); 899 for(cluster_offset = start; cluster_offset <= last; 900 cluster_offset += s->cluster_size) { 901 k = cluster_offset >> s->cluster_bits; 902 if (k < 0) { 903 fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n", 904 cluster_offset); 905 res->corruptions++; 906 } else if (k >= refcount_table_size) { 907 fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after " 908 "the end of the image file, can't properly check refcounts.\n", 909 cluster_offset); 910 res->check_errors++; 911 } else { 912 if (++refcount_table[k] == 0) { 913 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64 914 "\n", cluster_offset); 915 res->corruptions++; 916 } 917 } 918 } 919 } 920 921 /* 922 * Increases the refcount in the given refcount table for the all clusters 923 * referenced in the L2 table. While doing so, performs some checks on L2 924 * entries. 925 * 926 * Returns the number of errors found by the checks or -errno if an internal 927 * error occurred. 928 */ 929 static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res, 930 uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset, 931 int check_copied) 932 { 933 BDRVQcowState *s = bs->opaque; 934 uint64_t *l2_table, l2_entry; 935 int i, l2_size, nb_csectors, refcount; 936 937 /* Read L2 table from disk */ 938 l2_size = s->l2_size * sizeof(uint64_t); 939 l2_table = g_malloc(l2_size); 940 941 if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size) 942 goto fail; 943 944 /* Do the actual checks */ 945 for(i = 0; i < s->l2_size; i++) { 946 l2_entry = be64_to_cpu(l2_table[i]); 947 948 switch (qcow2_get_cluster_type(l2_entry)) { 949 case QCOW2_CLUSTER_COMPRESSED: 950 /* Compressed clusters don't have QCOW_OFLAG_COPIED */ 951 if (l2_entry & QCOW_OFLAG_COPIED) { 952 fprintf(stderr, "ERROR: cluster %" PRId64 ": " 953 "copied flag must never be set for compressed " 954 "clusters\n", l2_entry >> s->cluster_bits); 955 l2_entry &= ~QCOW_OFLAG_COPIED; 956 res->corruptions++; 957 } 958 959 /* Mark cluster as used */ 960 nb_csectors = ((l2_entry >> s->csize_shift) & 961 s->csize_mask) + 1; 962 l2_entry &= s->cluster_offset_mask; 963 inc_refcounts(bs, res, refcount_table, refcount_table_size, 964 l2_entry & ~511, nb_csectors * 512); 965 break; 966 967 case QCOW2_CLUSTER_ZERO: 968 if ((l2_entry & L2E_OFFSET_MASK) == 0) { 969 break; 970 } 971 /* fall through */ 972 973 case QCOW2_CLUSTER_NORMAL: 974 { 975 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ 976 uint64_t offset = l2_entry & L2E_OFFSET_MASK; 977 978 if (check_copied) { 979 refcount = get_refcount(bs, offset >> s->cluster_bits); 980 if (refcount < 0) { 981 fprintf(stderr, "Can't get refcount for offset %" 982 PRIx64 ": %s\n", l2_entry, strerror(-refcount)); 983 goto fail; 984 } 985 if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) { 986 fprintf(stderr, "ERROR OFLAG_COPIED: offset=%" 987 PRIx64 " refcount=%d\n", l2_entry, refcount); 988 res->corruptions++; 989 } 990 } 991 992 /* Mark cluster as used */ 993 inc_refcounts(bs, res, refcount_table,refcount_table_size, 994 offset, s->cluster_size); 995 996 /* Correct offsets are cluster aligned */ 997 if (offset & (s->cluster_size - 1)) { 998 fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not " 999 "properly aligned; L2 entry corrupted.\n", offset); 1000 res->corruptions++; 1001 } 1002 break; 1003 } 1004 1005 case QCOW2_CLUSTER_UNALLOCATED: 1006 break; 1007 1008 default: 1009 abort(); 1010 } 1011 } 1012 1013 g_free(l2_table); 1014 return 0; 1015 1016 fail: 1017 fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n"); 1018 g_free(l2_table); 1019 return -EIO; 1020 } 1021 1022 /* 1023 * Increases the refcount for the L1 table, its L2 tables and all referenced 1024 * clusters in the given refcount table. While doing so, performs some checks 1025 * on L1 and L2 entries. 1026 * 1027 * Returns the number of errors found by the checks or -errno if an internal 1028 * error occurred. 1029 */ 1030 static int check_refcounts_l1(BlockDriverState *bs, 1031 BdrvCheckResult *res, 1032 uint16_t *refcount_table, 1033 int refcount_table_size, 1034 int64_t l1_table_offset, int l1_size, 1035 int check_copied) 1036 { 1037 BDRVQcowState *s = bs->opaque; 1038 uint64_t *l1_table, l2_offset, l1_size2; 1039 int i, refcount, ret; 1040 1041 l1_size2 = l1_size * sizeof(uint64_t); 1042 1043 /* Mark L1 table as used */ 1044 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1045 l1_table_offset, l1_size2); 1046 1047 /* Read L1 table entries from disk */ 1048 if (l1_size2 == 0) { 1049 l1_table = NULL; 1050 } else { 1051 l1_table = g_malloc(l1_size2); 1052 if (bdrv_pread(bs->file, l1_table_offset, 1053 l1_table, l1_size2) != l1_size2) 1054 goto fail; 1055 for(i = 0;i < l1_size; i++) 1056 be64_to_cpus(&l1_table[i]); 1057 } 1058 1059 /* Do the actual checks */ 1060 for(i = 0; i < l1_size; i++) { 1061 l2_offset = l1_table[i]; 1062 if (l2_offset) { 1063 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ 1064 if (check_copied) { 1065 refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED) 1066 >> s->cluster_bits); 1067 if (refcount < 0) { 1068 fprintf(stderr, "Can't get refcount for l2_offset %" 1069 PRIx64 ": %s\n", l2_offset, strerror(-refcount)); 1070 goto fail; 1071 } 1072 if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) { 1073 fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64 1074 " refcount=%d\n", l2_offset, refcount); 1075 res->corruptions++; 1076 } 1077 } 1078 1079 /* Mark L2 table as used */ 1080 l2_offset &= L1E_OFFSET_MASK; 1081 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1082 l2_offset, s->cluster_size); 1083 1084 /* L2 tables are cluster aligned */ 1085 if (l2_offset & (s->cluster_size - 1)) { 1086 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not " 1087 "cluster aligned; L1 entry corrupted\n", l2_offset); 1088 res->corruptions++; 1089 } 1090 1091 /* Process and check L2 entries */ 1092 ret = check_refcounts_l2(bs, res, refcount_table, 1093 refcount_table_size, l2_offset, check_copied); 1094 if (ret < 0) { 1095 goto fail; 1096 } 1097 } 1098 } 1099 g_free(l1_table); 1100 return 0; 1101 1102 fail: 1103 fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n"); 1104 res->check_errors++; 1105 g_free(l1_table); 1106 return -EIO; 1107 } 1108 1109 /* 1110 * Checks an image for refcount consistency. 1111 * 1112 * Returns 0 if no errors are found, the number of errors in case the image is 1113 * detected as corrupted, and -errno when an internal error occurred. 1114 */ 1115 int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res, 1116 BdrvCheckMode fix) 1117 { 1118 BDRVQcowState *s = bs->opaque; 1119 int64_t size, i; 1120 int nb_clusters, refcount1, refcount2; 1121 QCowSnapshot *sn; 1122 uint16_t *refcount_table; 1123 int ret; 1124 1125 size = bdrv_getlength(bs->file); 1126 nb_clusters = size_to_clusters(s, size); 1127 refcount_table = g_malloc0(nb_clusters * sizeof(uint16_t)); 1128 1129 /* header */ 1130 inc_refcounts(bs, res, refcount_table, nb_clusters, 1131 0, s->cluster_size); 1132 1133 /* current L1 table */ 1134 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1135 s->l1_table_offset, s->l1_size, 1); 1136 if (ret < 0) { 1137 goto fail; 1138 } 1139 1140 /* snapshots */ 1141 for(i = 0; i < s->nb_snapshots; i++) { 1142 sn = s->snapshots + i; 1143 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1144 sn->l1_table_offset, sn->l1_size, 0); 1145 if (ret < 0) { 1146 goto fail; 1147 } 1148 } 1149 inc_refcounts(bs, res, refcount_table, nb_clusters, 1150 s->snapshots_offset, s->snapshots_size); 1151 1152 /* refcount data */ 1153 inc_refcounts(bs, res, refcount_table, nb_clusters, 1154 s->refcount_table_offset, 1155 s->refcount_table_size * sizeof(uint64_t)); 1156 1157 for(i = 0; i < s->refcount_table_size; i++) { 1158 uint64_t offset, cluster; 1159 offset = s->refcount_table[i]; 1160 cluster = offset >> s->cluster_bits; 1161 1162 /* Refcount blocks are cluster aligned */ 1163 if (offset & (s->cluster_size - 1)) { 1164 fprintf(stderr, "ERROR refcount block %" PRId64 " is not " 1165 "cluster aligned; refcount table entry corrupted\n", i); 1166 res->corruptions++; 1167 continue; 1168 } 1169 1170 if (cluster >= nb_clusters) { 1171 fprintf(stderr, "ERROR refcount block %" PRId64 1172 " is outside image\n", i); 1173 res->corruptions++; 1174 continue; 1175 } 1176 1177 if (offset != 0) { 1178 inc_refcounts(bs, res, refcount_table, nb_clusters, 1179 offset, s->cluster_size); 1180 if (refcount_table[cluster] != 1) { 1181 fprintf(stderr, "ERROR refcount block %" PRId64 1182 " refcount=%d\n", 1183 i, refcount_table[cluster]); 1184 res->corruptions++; 1185 } 1186 } 1187 } 1188 1189 /* compare ref counts */ 1190 for(i = 0; i < nb_clusters; i++) { 1191 refcount1 = get_refcount(bs, i); 1192 if (refcount1 < 0) { 1193 fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n", 1194 i, strerror(-refcount1)); 1195 res->check_errors++; 1196 continue; 1197 } 1198 1199 refcount2 = refcount_table[i]; 1200 if (refcount1 != refcount2) { 1201 1202 /* Check if we're allowed to fix the mismatch */ 1203 int *num_fixed = NULL; 1204 if (refcount1 > refcount2 && (fix & BDRV_FIX_LEAKS)) { 1205 num_fixed = &res->leaks_fixed; 1206 } else if (refcount1 < refcount2 && (fix & BDRV_FIX_ERRORS)) { 1207 num_fixed = &res->corruptions_fixed; 1208 } 1209 1210 fprintf(stderr, "%s cluster %" PRId64 " refcount=%d reference=%d\n", 1211 num_fixed != NULL ? "Repairing" : 1212 refcount1 < refcount2 ? "ERROR" : 1213 "Leaked", 1214 i, refcount1, refcount2); 1215 1216 if (num_fixed) { 1217 ret = update_refcount(bs, i << s->cluster_bits, 1, 1218 refcount2 - refcount1); 1219 if (ret >= 0) { 1220 (*num_fixed)++; 1221 continue; 1222 } 1223 } 1224 1225 /* And if we couldn't, print an error */ 1226 if (refcount1 < refcount2) { 1227 res->corruptions++; 1228 } else { 1229 res->leaks++; 1230 } 1231 } 1232 } 1233 1234 ret = 0; 1235 1236 fail: 1237 g_free(refcount_table); 1238 1239 return ret; 1240 } 1241 1242