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/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 l1_table = g_malloc0(align_offset(l1_size2, 512)); 741 l1_allocated = 1; 742 if (bdrv_pread(bs->file, l1_table_offset, 743 l1_table, l1_size2) != l1_size2) 744 { 745 ret = -EIO; 746 goto fail; 747 } 748 749 for(i = 0;i < l1_size; i++) 750 be64_to_cpus(&l1_table[i]); 751 } else { 752 assert(l1_size == s->l1_size); 753 l1_table = s->l1_table; 754 l1_allocated = 0; 755 } 756 757 for(i = 0; i < l1_size; i++) { 758 l2_offset = l1_table[i]; 759 if (l2_offset) { 760 old_l2_offset = l2_offset; 761 l2_offset &= L1E_OFFSET_MASK; 762 763 ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, 764 (void**) &l2_table); 765 if (ret < 0) { 766 goto fail; 767 } 768 769 for(j = 0; j < s->l2_size; j++) { 770 offset = be64_to_cpu(l2_table[j]); 771 if (offset != 0) { 772 old_offset = offset; 773 offset &= ~QCOW_OFLAG_COPIED; 774 if (offset & QCOW_OFLAG_COMPRESSED) { 775 nb_csectors = ((offset >> s->csize_shift) & 776 s->csize_mask) + 1; 777 if (addend != 0) { 778 int ret; 779 ret = update_refcount(bs, 780 (offset & s->cluster_offset_mask) & ~511, 781 nb_csectors * 512, addend); 782 if (ret < 0) { 783 goto fail; 784 } 785 786 /* TODO Flushing once for the whole function should 787 * be enough */ 788 bdrv_flush(bs->file); 789 } 790 /* compressed clusters are never modified */ 791 refcount = 2; 792 } else { 793 uint64_t cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits; 794 if (addend != 0) { 795 refcount = update_cluster_refcount(bs, cluster_index, addend); 796 } else { 797 refcount = get_refcount(bs, cluster_index); 798 } 799 800 if (refcount < 0) { 801 ret = -EIO; 802 goto fail; 803 } 804 } 805 806 if (refcount == 1) { 807 offset |= QCOW_OFLAG_COPIED; 808 } 809 if (offset != old_offset) { 810 if (addend > 0) { 811 qcow2_cache_set_dependency(bs, s->l2_table_cache, 812 s->refcount_block_cache); 813 } 814 l2_table[j] = cpu_to_be64(offset); 815 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); 816 } 817 } 818 } 819 820 ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 821 if (ret < 0) { 822 goto fail; 823 } 824 825 826 if (addend != 0) { 827 refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend); 828 } else { 829 refcount = get_refcount(bs, l2_offset >> s->cluster_bits); 830 } 831 if (refcount < 0) { 832 ret = -EIO; 833 goto fail; 834 } else if (refcount == 1) { 835 l2_offset |= QCOW_OFLAG_COPIED; 836 } 837 if (l2_offset != old_l2_offset) { 838 l1_table[i] = l2_offset; 839 l1_modified = 1; 840 } 841 } 842 } 843 844 ret = 0; 845 fail: 846 if (l2_table) { 847 qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 848 } 849 850 /* Update L1 only if it isn't deleted anyway (addend = -1) */ 851 if (addend >= 0 && l1_modified) { 852 for(i = 0; i < l1_size; i++) 853 cpu_to_be64s(&l1_table[i]); 854 if (bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table, 855 l1_size2) < 0) 856 goto fail; 857 for(i = 0; i < l1_size; i++) 858 be64_to_cpus(&l1_table[i]); 859 } 860 if (l1_allocated) 861 g_free(l1_table); 862 return ret; 863 } 864 865 866 867 868 /*********************************************************/ 869 /* refcount checking functions */ 870 871 872 873 /* 874 * Increases the refcount for a range of clusters in a given refcount table. 875 * This is used to construct a temporary refcount table out of L1 and L2 tables 876 * which can be compared the the refcount table saved in the image. 877 * 878 * Modifies the number of errors in res. 879 */ 880 static void inc_refcounts(BlockDriverState *bs, 881 BdrvCheckResult *res, 882 uint16_t *refcount_table, 883 int refcount_table_size, 884 int64_t offset, int64_t size) 885 { 886 BDRVQcowState *s = bs->opaque; 887 int64_t start, last, cluster_offset; 888 int k; 889 890 if (size <= 0) 891 return; 892 893 start = offset & ~(s->cluster_size - 1); 894 last = (offset + size - 1) & ~(s->cluster_size - 1); 895 for(cluster_offset = start; cluster_offset <= last; 896 cluster_offset += s->cluster_size) { 897 k = cluster_offset >> s->cluster_bits; 898 if (k < 0) { 899 fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n", 900 cluster_offset); 901 res->corruptions++; 902 } else if (k >= refcount_table_size) { 903 fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after " 904 "the end of the image file, can't properly check refcounts.\n", 905 cluster_offset); 906 res->check_errors++; 907 } else { 908 if (++refcount_table[k] == 0) { 909 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64 910 "\n", cluster_offset); 911 res->corruptions++; 912 } 913 } 914 } 915 } 916 917 /* 918 * Increases the refcount in the given refcount table for the all clusters 919 * referenced in the L2 table. While doing so, performs some checks on L2 920 * entries. 921 * 922 * Returns the number of errors found by the checks or -errno if an internal 923 * error occurred. 924 */ 925 static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res, 926 uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset, 927 int check_copied) 928 { 929 BDRVQcowState *s = bs->opaque; 930 uint64_t *l2_table, l2_entry; 931 int i, l2_size, nb_csectors, refcount; 932 933 /* Read L2 table from disk */ 934 l2_size = s->l2_size * sizeof(uint64_t); 935 l2_table = g_malloc(l2_size); 936 937 if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size) 938 goto fail; 939 940 /* Do the actual checks */ 941 for(i = 0; i < s->l2_size; i++) { 942 l2_entry = be64_to_cpu(l2_table[i]); 943 944 switch (qcow2_get_cluster_type(l2_entry)) { 945 case QCOW2_CLUSTER_COMPRESSED: 946 /* Compressed clusters don't have QCOW_OFLAG_COPIED */ 947 if (l2_entry & QCOW_OFLAG_COPIED) { 948 fprintf(stderr, "ERROR: cluster %" PRId64 ": " 949 "copied flag must never be set for compressed " 950 "clusters\n", l2_entry >> s->cluster_bits); 951 l2_entry &= ~QCOW_OFLAG_COPIED; 952 res->corruptions++; 953 } 954 955 /* Mark cluster as used */ 956 nb_csectors = ((l2_entry >> s->csize_shift) & 957 s->csize_mask) + 1; 958 l2_entry &= s->cluster_offset_mask; 959 inc_refcounts(bs, res, refcount_table, refcount_table_size, 960 l2_entry & ~511, nb_csectors * 512); 961 break; 962 963 case QCOW2_CLUSTER_ZERO: 964 if ((l2_entry & L2E_OFFSET_MASK) == 0) { 965 break; 966 } 967 /* fall through */ 968 969 case QCOW2_CLUSTER_NORMAL: 970 { 971 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ 972 uint64_t offset = l2_entry & L2E_OFFSET_MASK; 973 974 if (check_copied) { 975 refcount = get_refcount(bs, offset >> s->cluster_bits); 976 if (refcount < 0) { 977 fprintf(stderr, "Can't get refcount for offset %" 978 PRIx64 ": %s\n", l2_entry, strerror(-refcount)); 979 goto fail; 980 } 981 if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) { 982 fprintf(stderr, "ERROR OFLAG_COPIED: offset=%" 983 PRIx64 " refcount=%d\n", l2_entry, refcount); 984 res->corruptions++; 985 } 986 } 987 988 /* Mark cluster as used */ 989 inc_refcounts(bs, res, refcount_table,refcount_table_size, 990 offset, s->cluster_size); 991 992 /* Correct offsets are cluster aligned */ 993 if (offset & (s->cluster_size - 1)) { 994 fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not " 995 "properly aligned; L2 entry corrupted.\n", offset); 996 res->corruptions++; 997 } 998 break; 999 } 1000 1001 case QCOW2_CLUSTER_UNALLOCATED: 1002 break; 1003 1004 default: 1005 abort(); 1006 } 1007 } 1008 1009 g_free(l2_table); 1010 return 0; 1011 1012 fail: 1013 fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n"); 1014 g_free(l2_table); 1015 return -EIO; 1016 } 1017 1018 /* 1019 * Increases the refcount for the L1 table, its L2 tables and all referenced 1020 * clusters in the given refcount table. While doing so, performs some checks 1021 * on L1 and L2 entries. 1022 * 1023 * Returns the number of errors found by the checks or -errno if an internal 1024 * error occurred. 1025 */ 1026 static int check_refcounts_l1(BlockDriverState *bs, 1027 BdrvCheckResult *res, 1028 uint16_t *refcount_table, 1029 int refcount_table_size, 1030 int64_t l1_table_offset, int l1_size, 1031 int check_copied) 1032 { 1033 BDRVQcowState *s = bs->opaque; 1034 uint64_t *l1_table, l2_offset, l1_size2; 1035 int i, refcount, ret; 1036 1037 l1_size2 = l1_size * sizeof(uint64_t); 1038 1039 /* Mark L1 table as used */ 1040 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1041 l1_table_offset, l1_size2); 1042 1043 /* Read L1 table entries from disk */ 1044 if (l1_size2 == 0) { 1045 l1_table = NULL; 1046 } else { 1047 l1_table = g_malloc(l1_size2); 1048 if (bdrv_pread(bs->file, l1_table_offset, 1049 l1_table, l1_size2) != l1_size2) 1050 goto fail; 1051 for(i = 0;i < l1_size; i++) 1052 be64_to_cpus(&l1_table[i]); 1053 } 1054 1055 /* Do the actual checks */ 1056 for(i = 0; i < l1_size; i++) { 1057 l2_offset = l1_table[i]; 1058 if (l2_offset) { 1059 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */ 1060 if (check_copied) { 1061 refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED) 1062 >> s->cluster_bits); 1063 if (refcount < 0) { 1064 fprintf(stderr, "Can't get refcount for l2_offset %" 1065 PRIx64 ": %s\n", l2_offset, strerror(-refcount)); 1066 goto fail; 1067 } 1068 if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) { 1069 fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64 1070 " refcount=%d\n", l2_offset, refcount); 1071 res->corruptions++; 1072 } 1073 } 1074 1075 /* Mark L2 table as used */ 1076 l2_offset &= L1E_OFFSET_MASK; 1077 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1078 l2_offset, s->cluster_size); 1079 1080 /* L2 tables are cluster aligned */ 1081 if (l2_offset & (s->cluster_size - 1)) { 1082 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not " 1083 "cluster aligned; L1 entry corrupted\n", l2_offset); 1084 res->corruptions++; 1085 } 1086 1087 /* Process and check L2 entries */ 1088 ret = check_refcounts_l2(bs, res, refcount_table, 1089 refcount_table_size, l2_offset, check_copied); 1090 if (ret < 0) { 1091 goto fail; 1092 } 1093 } 1094 } 1095 g_free(l1_table); 1096 return 0; 1097 1098 fail: 1099 fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n"); 1100 res->check_errors++; 1101 g_free(l1_table); 1102 return -EIO; 1103 } 1104 1105 /* 1106 * Checks an image for refcount consistency. 1107 * 1108 * Returns 0 if no errors are found, the number of errors in case the image is 1109 * detected as corrupted, and -errno when an internal error occurred. 1110 */ 1111 int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res, 1112 BdrvCheckMode fix) 1113 { 1114 BDRVQcowState *s = bs->opaque; 1115 int64_t size, i; 1116 int nb_clusters, refcount1, refcount2; 1117 QCowSnapshot *sn; 1118 uint16_t *refcount_table; 1119 int ret; 1120 1121 size = bdrv_getlength(bs->file); 1122 nb_clusters = size_to_clusters(s, size); 1123 refcount_table = g_malloc0(nb_clusters * sizeof(uint16_t)); 1124 1125 /* header */ 1126 inc_refcounts(bs, res, refcount_table, nb_clusters, 1127 0, s->cluster_size); 1128 1129 /* current L1 table */ 1130 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1131 s->l1_table_offset, s->l1_size, 1); 1132 if (ret < 0) { 1133 goto fail; 1134 } 1135 1136 /* snapshots */ 1137 for(i = 0; i < s->nb_snapshots; i++) { 1138 sn = s->snapshots + i; 1139 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1140 sn->l1_table_offset, sn->l1_size, 0); 1141 if (ret < 0) { 1142 goto fail; 1143 } 1144 } 1145 inc_refcounts(bs, res, refcount_table, nb_clusters, 1146 s->snapshots_offset, s->snapshots_size); 1147 1148 /* refcount data */ 1149 inc_refcounts(bs, res, refcount_table, nb_clusters, 1150 s->refcount_table_offset, 1151 s->refcount_table_size * sizeof(uint64_t)); 1152 1153 for(i = 0; i < s->refcount_table_size; i++) { 1154 uint64_t offset, cluster; 1155 offset = s->refcount_table[i]; 1156 cluster = offset >> s->cluster_bits; 1157 1158 /* Refcount blocks are cluster aligned */ 1159 if (offset & (s->cluster_size - 1)) { 1160 fprintf(stderr, "ERROR refcount block %" PRId64 " is not " 1161 "cluster aligned; refcount table entry corrupted\n", i); 1162 res->corruptions++; 1163 continue; 1164 } 1165 1166 if (cluster >= nb_clusters) { 1167 fprintf(stderr, "ERROR refcount block %" PRId64 1168 " is outside image\n", i); 1169 res->corruptions++; 1170 continue; 1171 } 1172 1173 if (offset != 0) { 1174 inc_refcounts(bs, res, refcount_table, nb_clusters, 1175 offset, s->cluster_size); 1176 if (refcount_table[cluster] != 1) { 1177 fprintf(stderr, "ERROR refcount block %" PRId64 1178 " refcount=%d\n", 1179 i, refcount_table[cluster]); 1180 res->corruptions++; 1181 } 1182 } 1183 } 1184 1185 /* compare ref counts */ 1186 for(i = 0; i < nb_clusters; i++) { 1187 refcount1 = get_refcount(bs, i); 1188 if (refcount1 < 0) { 1189 fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n", 1190 i, strerror(-refcount1)); 1191 res->check_errors++; 1192 continue; 1193 } 1194 1195 refcount2 = refcount_table[i]; 1196 if (refcount1 != refcount2) { 1197 1198 /* Check if we're allowed to fix the mismatch */ 1199 int *num_fixed = NULL; 1200 if (refcount1 > refcount2 && (fix & BDRV_FIX_LEAKS)) { 1201 num_fixed = &res->leaks_fixed; 1202 } else if (refcount1 < refcount2 && (fix & BDRV_FIX_ERRORS)) { 1203 num_fixed = &res->corruptions_fixed; 1204 } 1205 1206 fprintf(stderr, "%s cluster %" PRId64 " refcount=%d reference=%d\n", 1207 num_fixed != NULL ? "Repairing" : 1208 refcount1 < refcount2 ? "ERROR" : 1209 "Leaked", 1210 i, refcount1, refcount2); 1211 1212 if (num_fixed) { 1213 ret = update_refcount(bs, i << s->cluster_bits, 1, 1214 refcount2 - refcount1); 1215 if (ret >= 0) { 1216 (*num_fixed)++; 1217 continue; 1218 } 1219 } 1220 1221 /* And if we couldn't, print an error */ 1222 if (refcount1 < refcount2) { 1223 res->corruptions++; 1224 } else { 1225 res->leaks++; 1226 } 1227 } 1228 } 1229 1230 ret = 0; 1231 1232 fail: 1233 g_free(refcount_table); 1234 1235 return ret; 1236 } 1237 1238