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 #include "qemu/range.h" 29 #include "qapi/qmp/types.h" 30 31 static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size); 32 static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, 33 int64_t offset, int64_t length, 34 int addend, enum qcow2_discard_type type); 35 36 37 /*********************************************************/ 38 /* refcount handling */ 39 40 int qcow2_refcount_init(BlockDriverState *bs) 41 { 42 BDRVQcowState *s = bs->opaque; 43 int ret, refcount_table_size2, i; 44 45 refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t); 46 s->refcount_table = g_malloc(refcount_table_size2); 47 if (s->refcount_table_size > 0) { 48 BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_LOAD); 49 ret = bdrv_pread(bs->file, s->refcount_table_offset, 50 s->refcount_table, refcount_table_size2); 51 if (ret != refcount_table_size2) 52 goto fail; 53 for(i = 0; i < s->refcount_table_size; i++) 54 be64_to_cpus(&s->refcount_table[i]); 55 } 56 return 0; 57 fail: 58 return -ENOMEM; 59 } 60 61 void qcow2_refcount_close(BlockDriverState *bs) 62 { 63 BDRVQcowState *s = bs->opaque; 64 g_free(s->refcount_table); 65 } 66 67 68 static int load_refcount_block(BlockDriverState *bs, 69 int64_t refcount_block_offset, 70 void **refcount_block) 71 { 72 BDRVQcowState *s = bs->opaque; 73 int ret; 74 75 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_LOAD); 76 ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset, 77 refcount_block); 78 79 return ret; 80 } 81 82 /* 83 * Returns the refcount of the cluster given by its index. Any non-negative 84 * return value is the refcount of the cluster, negative values are -errno 85 * and indicate an error. 86 */ 87 static int get_refcount(BlockDriverState *bs, int64_t cluster_index) 88 { 89 BDRVQcowState *s = bs->opaque; 90 int refcount_table_index, block_index; 91 int64_t refcount_block_offset; 92 int ret; 93 uint16_t *refcount_block; 94 uint16_t refcount; 95 96 refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT); 97 if (refcount_table_index >= s->refcount_table_size) 98 return 0; 99 refcount_block_offset = s->refcount_table[refcount_table_index]; 100 if (!refcount_block_offset) 101 return 0; 102 103 ret = qcow2_cache_get(bs, s->refcount_block_cache, refcount_block_offset, 104 (void**) &refcount_block); 105 if (ret < 0) { 106 return ret; 107 } 108 109 block_index = cluster_index & 110 ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); 111 refcount = be16_to_cpu(refcount_block[block_index]); 112 113 ret = qcow2_cache_put(bs, s->refcount_block_cache, 114 (void**) &refcount_block); 115 if (ret < 0) { 116 return ret; 117 } 118 119 return refcount; 120 } 121 122 /* 123 * Rounds the refcount table size up to avoid growing the table for each single 124 * refcount block that is allocated. 125 */ 126 static unsigned int next_refcount_table_size(BDRVQcowState *s, 127 unsigned int min_size) 128 { 129 unsigned int min_clusters = (min_size >> (s->cluster_bits - 3)) + 1; 130 unsigned int refcount_table_clusters = 131 MAX(1, s->refcount_table_size >> (s->cluster_bits - 3)); 132 133 while (min_clusters > refcount_table_clusters) { 134 refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2; 135 } 136 137 return refcount_table_clusters << (s->cluster_bits - 3); 138 } 139 140 141 /* Checks if two offsets are described by the same refcount block */ 142 static int in_same_refcount_block(BDRVQcowState *s, uint64_t offset_a, 143 uint64_t offset_b) 144 { 145 uint64_t block_a = offset_a >> (2 * s->cluster_bits - REFCOUNT_SHIFT); 146 uint64_t block_b = offset_b >> (2 * s->cluster_bits - REFCOUNT_SHIFT); 147 148 return (block_a == block_b); 149 } 150 151 /* 152 * Loads a refcount block. If it doesn't exist yet, it is allocated first 153 * (including growing the refcount table if needed). 154 * 155 * Returns 0 on success or -errno in error case 156 */ 157 static int alloc_refcount_block(BlockDriverState *bs, 158 int64_t cluster_index, uint16_t **refcount_block) 159 { 160 BDRVQcowState *s = bs->opaque; 161 unsigned int refcount_table_index; 162 int ret; 163 164 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC); 165 166 /* Find the refcount block for the given cluster */ 167 refcount_table_index = cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT); 168 169 if (refcount_table_index < s->refcount_table_size) { 170 171 uint64_t refcount_block_offset = 172 s->refcount_table[refcount_table_index] & REFT_OFFSET_MASK; 173 174 /* If it's already there, we're done */ 175 if (refcount_block_offset) { 176 return load_refcount_block(bs, refcount_block_offset, 177 (void**) refcount_block); 178 } 179 } 180 181 /* 182 * If we came here, we need to allocate something. Something is at least 183 * a cluster for the new refcount block. It may also include a new refcount 184 * table if the old refcount table is too small. 185 * 186 * Note that allocating clusters here needs some special care: 187 * 188 * - We can't use the normal qcow2_alloc_clusters(), it would try to 189 * increase the refcount and very likely we would end up with an endless 190 * recursion. Instead we must place the refcount blocks in a way that 191 * they can describe them themselves. 192 * 193 * - We need to consider that at this point we are inside update_refcounts 194 * and doing the initial refcount increase. This means that some clusters 195 * have already been allocated by the caller, but their refcount isn't 196 * accurate yet. free_cluster_index tells us where this allocation ends 197 * as long as we don't overwrite it by freeing clusters. 198 * 199 * - alloc_clusters_noref and qcow2_free_clusters may load a different 200 * refcount block into the cache 201 */ 202 203 *refcount_block = NULL; 204 205 /* We write to the refcount table, so we might depend on L2 tables */ 206 ret = qcow2_cache_flush(bs, s->l2_table_cache); 207 if (ret < 0) { 208 return ret; 209 } 210 211 /* Allocate the refcount block itself and mark it as used */ 212 int64_t new_block = alloc_clusters_noref(bs, s->cluster_size); 213 if (new_block < 0) { 214 return new_block; 215 } 216 217 #ifdef DEBUG_ALLOC2 218 fprintf(stderr, "qcow2: Allocate refcount block %d for %" PRIx64 219 " at %" PRIx64 "\n", 220 refcount_table_index, cluster_index << s->cluster_bits, new_block); 221 #endif 222 223 if (in_same_refcount_block(s, new_block, cluster_index << s->cluster_bits)) { 224 /* Zero the new refcount block before updating it */ 225 ret = qcow2_cache_get_empty(bs, s->refcount_block_cache, new_block, 226 (void**) refcount_block); 227 if (ret < 0) { 228 goto fail_block; 229 } 230 231 memset(*refcount_block, 0, s->cluster_size); 232 233 /* The block describes itself, need to update the cache */ 234 int block_index = (new_block >> s->cluster_bits) & 235 ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); 236 (*refcount_block)[block_index] = cpu_to_be16(1); 237 } else { 238 /* Described somewhere else. This can recurse at most twice before we 239 * arrive at a block that describes itself. */ 240 ret = update_refcount(bs, new_block, s->cluster_size, 1, 241 QCOW2_DISCARD_NEVER); 242 if (ret < 0) { 243 goto fail_block; 244 } 245 246 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 247 if (ret < 0) { 248 goto fail_block; 249 } 250 251 /* Initialize the new refcount block only after updating its refcount, 252 * update_refcount uses the refcount cache itself */ 253 ret = qcow2_cache_get_empty(bs, s->refcount_block_cache, new_block, 254 (void**) refcount_block); 255 if (ret < 0) { 256 goto fail_block; 257 } 258 259 memset(*refcount_block, 0, s->cluster_size); 260 } 261 262 /* Now the new refcount block needs to be written to disk */ 263 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE); 264 qcow2_cache_entry_mark_dirty(s->refcount_block_cache, *refcount_block); 265 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 266 if (ret < 0) { 267 goto fail_block; 268 } 269 270 /* If the refcount table is big enough, just hook the block up there */ 271 if (refcount_table_index < s->refcount_table_size) { 272 uint64_t data64 = cpu_to_be64(new_block); 273 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_HOOKUP); 274 ret = bdrv_pwrite_sync(bs->file, 275 s->refcount_table_offset + refcount_table_index * sizeof(uint64_t), 276 &data64, sizeof(data64)); 277 if (ret < 0) { 278 goto fail_block; 279 } 280 281 s->refcount_table[refcount_table_index] = new_block; 282 return 0; 283 } 284 285 ret = qcow2_cache_put(bs, s->refcount_block_cache, (void**) refcount_block); 286 if (ret < 0) { 287 goto fail_block; 288 } 289 290 /* 291 * If we come here, we need to grow the refcount table. Again, a new 292 * refcount table needs some space and we can't simply allocate to avoid 293 * endless recursion. 294 * 295 * Therefore let's grab new refcount blocks at the end of the image, which 296 * will describe themselves and the new refcount table. This way we can 297 * reference them only in the new table and do the switch to the new 298 * refcount table at once without producing an inconsistent state in 299 * between. 300 */ 301 BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_GROW); 302 303 /* Calculate the number of refcount blocks needed so far */ 304 uint64_t refcount_block_clusters = 1 << (s->cluster_bits - REFCOUNT_SHIFT); 305 uint64_t blocks_used = (s->free_cluster_index + 306 refcount_block_clusters - 1) / refcount_block_clusters; 307 308 /* And now we need at least one block more for the new metadata */ 309 uint64_t table_size = next_refcount_table_size(s, blocks_used + 1); 310 uint64_t last_table_size; 311 uint64_t blocks_clusters; 312 do { 313 uint64_t table_clusters = 314 size_to_clusters(s, table_size * sizeof(uint64_t)); 315 blocks_clusters = 1 + 316 ((table_clusters + refcount_block_clusters - 1) 317 / refcount_block_clusters); 318 uint64_t meta_clusters = table_clusters + blocks_clusters; 319 320 last_table_size = table_size; 321 table_size = next_refcount_table_size(s, blocks_used + 322 ((meta_clusters + refcount_block_clusters - 1) 323 / refcount_block_clusters)); 324 325 } while (last_table_size != table_size); 326 327 #ifdef DEBUG_ALLOC2 328 fprintf(stderr, "qcow2: Grow refcount table %" PRId32 " => %" PRId64 "\n", 329 s->refcount_table_size, table_size); 330 #endif 331 332 /* Create the new refcount table and blocks */ 333 uint64_t meta_offset = (blocks_used * refcount_block_clusters) * 334 s->cluster_size; 335 uint64_t table_offset = meta_offset + blocks_clusters * s->cluster_size; 336 uint16_t *new_blocks = g_malloc0(blocks_clusters * s->cluster_size); 337 uint64_t *new_table = g_malloc0(table_size * sizeof(uint64_t)); 338 339 assert(meta_offset >= (s->free_cluster_index * s->cluster_size)); 340 341 /* Fill the new refcount table */ 342 memcpy(new_table, s->refcount_table, 343 s->refcount_table_size * sizeof(uint64_t)); 344 new_table[refcount_table_index] = new_block; 345 346 int i; 347 for (i = 0; i < blocks_clusters; i++) { 348 new_table[blocks_used + i] = meta_offset + (i * s->cluster_size); 349 } 350 351 /* Fill the refcount blocks */ 352 uint64_t table_clusters = size_to_clusters(s, table_size * sizeof(uint64_t)); 353 int block = 0; 354 for (i = 0; i < table_clusters + blocks_clusters; i++) { 355 new_blocks[block++] = cpu_to_be16(1); 356 } 357 358 /* Write refcount blocks to disk */ 359 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_BLOCKS); 360 ret = bdrv_pwrite_sync(bs->file, meta_offset, new_blocks, 361 blocks_clusters * s->cluster_size); 362 g_free(new_blocks); 363 if (ret < 0) { 364 goto fail_table; 365 } 366 367 /* Write refcount table to disk */ 368 for(i = 0; i < table_size; i++) { 369 cpu_to_be64s(&new_table[i]); 370 } 371 372 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_WRITE_TABLE); 373 ret = bdrv_pwrite_sync(bs->file, table_offset, new_table, 374 table_size * sizeof(uint64_t)); 375 if (ret < 0) { 376 goto fail_table; 377 } 378 379 for(i = 0; i < table_size; i++) { 380 be64_to_cpus(&new_table[i]); 381 } 382 383 /* Hook up the new refcount table in the qcow2 header */ 384 uint8_t data[12]; 385 cpu_to_be64w((uint64_t*)data, table_offset); 386 cpu_to_be32w((uint32_t*)(data + 8), table_clusters); 387 BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_SWITCH_TABLE); 388 ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, refcount_table_offset), 389 data, sizeof(data)); 390 if (ret < 0) { 391 goto fail_table; 392 } 393 394 /* And switch it in memory */ 395 uint64_t old_table_offset = s->refcount_table_offset; 396 uint64_t old_table_size = s->refcount_table_size; 397 398 g_free(s->refcount_table); 399 s->refcount_table = new_table; 400 s->refcount_table_size = table_size; 401 s->refcount_table_offset = table_offset; 402 403 /* Free old table. Remember, we must not change free_cluster_index */ 404 uint64_t old_free_cluster_index = s->free_cluster_index; 405 qcow2_free_clusters(bs, old_table_offset, old_table_size * sizeof(uint64_t), 406 QCOW2_DISCARD_OTHER); 407 s->free_cluster_index = old_free_cluster_index; 408 409 ret = load_refcount_block(bs, new_block, (void**) refcount_block); 410 if (ret < 0) { 411 return ret; 412 } 413 414 return 0; 415 416 fail_table: 417 g_free(new_table); 418 fail_block: 419 if (*refcount_block != NULL) { 420 qcow2_cache_put(bs, s->refcount_block_cache, (void**) refcount_block); 421 } 422 return ret; 423 } 424 425 void qcow2_process_discards(BlockDriverState *bs, int ret) 426 { 427 BDRVQcowState *s = bs->opaque; 428 Qcow2DiscardRegion *d, *next; 429 430 QTAILQ_FOREACH_SAFE(d, &s->discards, next, next) { 431 QTAILQ_REMOVE(&s->discards, d, next); 432 433 /* Discard is optional, ignore the return value */ 434 if (ret >= 0) { 435 bdrv_discard(bs->file, 436 d->offset >> BDRV_SECTOR_BITS, 437 d->bytes >> BDRV_SECTOR_BITS); 438 } 439 440 g_free(d); 441 } 442 } 443 444 static void update_refcount_discard(BlockDriverState *bs, 445 uint64_t offset, uint64_t length) 446 { 447 BDRVQcowState *s = bs->opaque; 448 Qcow2DiscardRegion *d, *p, *next; 449 450 QTAILQ_FOREACH(d, &s->discards, next) { 451 uint64_t new_start = MIN(offset, d->offset); 452 uint64_t new_end = MAX(offset + length, d->offset + d->bytes); 453 454 if (new_end - new_start <= length + d->bytes) { 455 /* There can't be any overlap, areas ending up here have no 456 * references any more and therefore shouldn't get freed another 457 * time. */ 458 assert(d->bytes + length == new_end - new_start); 459 d->offset = new_start; 460 d->bytes = new_end - new_start; 461 goto found; 462 } 463 } 464 465 d = g_malloc(sizeof(*d)); 466 *d = (Qcow2DiscardRegion) { 467 .bs = bs, 468 .offset = offset, 469 .bytes = length, 470 }; 471 QTAILQ_INSERT_TAIL(&s->discards, d, next); 472 473 found: 474 /* Merge discard requests if they are adjacent now */ 475 QTAILQ_FOREACH_SAFE(p, &s->discards, next, next) { 476 if (p == d 477 || p->offset > d->offset + d->bytes 478 || d->offset > p->offset + p->bytes) 479 { 480 continue; 481 } 482 483 /* Still no overlap possible */ 484 assert(p->offset == d->offset + d->bytes 485 || d->offset == p->offset + p->bytes); 486 487 QTAILQ_REMOVE(&s->discards, p, next); 488 d->offset = MIN(d->offset, p->offset); 489 d->bytes += p->bytes; 490 } 491 } 492 493 /* XXX: cache several refcount block clusters ? */ 494 static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, 495 int64_t offset, int64_t length, int addend, enum qcow2_discard_type type) 496 { 497 BDRVQcowState *s = bs->opaque; 498 int64_t start, last, cluster_offset; 499 uint16_t *refcount_block = NULL; 500 int64_t old_table_index = -1; 501 int ret; 502 503 #ifdef DEBUG_ALLOC2 504 fprintf(stderr, "update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n", 505 offset, length, addend); 506 #endif 507 if (length < 0) { 508 return -EINVAL; 509 } else if (length == 0) { 510 return 0; 511 } 512 513 if (addend < 0) { 514 qcow2_cache_set_dependency(bs, s->refcount_block_cache, 515 s->l2_table_cache); 516 } 517 518 start = offset & ~(s->cluster_size - 1); 519 last = (offset + length - 1) & ~(s->cluster_size - 1); 520 for(cluster_offset = start; cluster_offset <= last; 521 cluster_offset += s->cluster_size) 522 { 523 int block_index, refcount; 524 int64_t cluster_index = cluster_offset >> s->cluster_bits; 525 int64_t table_index = 526 cluster_index >> (s->cluster_bits - REFCOUNT_SHIFT); 527 528 /* Load the refcount block and allocate it if needed */ 529 if (table_index != old_table_index) { 530 if (refcount_block) { 531 ret = qcow2_cache_put(bs, s->refcount_block_cache, 532 (void**) &refcount_block); 533 if (ret < 0) { 534 goto fail; 535 } 536 } 537 538 ret = alloc_refcount_block(bs, cluster_index, &refcount_block); 539 if (ret < 0) { 540 goto fail; 541 } 542 } 543 old_table_index = table_index; 544 545 qcow2_cache_entry_mark_dirty(s->refcount_block_cache, refcount_block); 546 547 /* we can update the count and save it */ 548 block_index = cluster_index & 549 ((1 << (s->cluster_bits - REFCOUNT_SHIFT)) - 1); 550 551 refcount = be16_to_cpu(refcount_block[block_index]); 552 refcount += addend; 553 if (refcount < 0 || refcount > 0xffff) { 554 ret = -EINVAL; 555 goto fail; 556 } 557 if (refcount == 0 && cluster_index < s->free_cluster_index) { 558 s->free_cluster_index = cluster_index; 559 } 560 refcount_block[block_index] = cpu_to_be16(refcount); 561 562 if (refcount == 0 && s->discard_passthrough[type]) { 563 update_refcount_discard(bs, cluster_offset, s->cluster_size); 564 } 565 } 566 567 ret = 0; 568 fail: 569 if (!s->cache_discards) { 570 qcow2_process_discards(bs, ret); 571 } 572 573 /* Write last changed block to disk */ 574 if (refcount_block) { 575 int wret; 576 wret = qcow2_cache_put(bs, s->refcount_block_cache, 577 (void**) &refcount_block); 578 if (wret < 0) { 579 return ret < 0 ? ret : wret; 580 } 581 } 582 583 /* 584 * Try do undo any updates if an error is returned (This may succeed in 585 * some cases like ENOSPC for allocating a new refcount block) 586 */ 587 if (ret < 0) { 588 int dummy; 589 dummy = update_refcount(bs, offset, cluster_offset - offset, -addend, 590 QCOW2_DISCARD_NEVER); 591 (void)dummy; 592 } 593 594 return ret; 595 } 596 597 /* 598 * Increases or decreases the refcount of a given cluster by one. 599 * addend must be 1 or -1. 600 * 601 * If the return value is non-negative, it is the new refcount of the cluster. 602 * If it is negative, it is -errno and indicates an error. 603 */ 604 int qcow2_update_cluster_refcount(BlockDriverState *bs, 605 int64_t cluster_index, 606 int addend, 607 enum qcow2_discard_type type) 608 { 609 BDRVQcowState *s = bs->opaque; 610 int ret; 611 612 ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend, 613 type); 614 if (ret < 0) { 615 return ret; 616 } 617 618 return get_refcount(bs, cluster_index); 619 } 620 621 622 623 /*********************************************************/ 624 /* cluster allocation functions */ 625 626 627 628 /* return < 0 if error */ 629 static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size) 630 { 631 BDRVQcowState *s = bs->opaque; 632 int i, nb_clusters, refcount; 633 634 nb_clusters = size_to_clusters(s, size); 635 retry: 636 for(i = 0; i < nb_clusters; i++) { 637 int64_t next_cluster_index = s->free_cluster_index++; 638 refcount = get_refcount(bs, next_cluster_index); 639 640 if (refcount < 0) { 641 return refcount; 642 } else if (refcount != 0) { 643 goto retry; 644 } 645 } 646 #ifdef DEBUG_ALLOC2 647 fprintf(stderr, "alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n", 648 size, 649 (s->free_cluster_index - nb_clusters) << s->cluster_bits); 650 #endif 651 return (s->free_cluster_index - nb_clusters) << s->cluster_bits; 652 } 653 654 int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size) 655 { 656 int64_t offset; 657 int ret; 658 659 BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC); 660 offset = alloc_clusters_noref(bs, size); 661 if (offset < 0) { 662 return offset; 663 } 664 665 ret = update_refcount(bs, offset, size, 1, QCOW2_DISCARD_NEVER); 666 if (ret < 0) { 667 return ret; 668 } 669 670 return offset; 671 } 672 673 int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, 674 int nb_clusters) 675 { 676 BDRVQcowState *s = bs->opaque; 677 uint64_t cluster_index; 678 uint64_t old_free_cluster_index; 679 int i, refcount, ret; 680 681 /* Check how many clusters there are free */ 682 cluster_index = offset >> s->cluster_bits; 683 for(i = 0; i < nb_clusters; i++) { 684 refcount = get_refcount(bs, cluster_index++); 685 686 if (refcount < 0) { 687 return refcount; 688 } else if (refcount != 0) { 689 break; 690 } 691 } 692 693 /* And then allocate them */ 694 old_free_cluster_index = s->free_cluster_index; 695 s->free_cluster_index = cluster_index + i; 696 697 ret = update_refcount(bs, offset, i << s->cluster_bits, 1, 698 QCOW2_DISCARD_NEVER); 699 if (ret < 0) { 700 return ret; 701 } 702 703 s->free_cluster_index = old_free_cluster_index; 704 705 return i; 706 } 707 708 /* only used to allocate compressed sectors. We try to allocate 709 contiguous sectors. size must be <= cluster_size */ 710 int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) 711 { 712 BDRVQcowState *s = bs->opaque; 713 int64_t offset, cluster_offset; 714 int free_in_cluster; 715 716 BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES); 717 assert(size > 0 && size <= s->cluster_size); 718 if (s->free_byte_offset == 0) { 719 offset = qcow2_alloc_clusters(bs, s->cluster_size); 720 if (offset < 0) { 721 return offset; 722 } 723 s->free_byte_offset = offset; 724 } 725 redo: 726 free_in_cluster = s->cluster_size - 727 (s->free_byte_offset & (s->cluster_size - 1)); 728 if (size <= free_in_cluster) { 729 /* enough space in current cluster */ 730 offset = s->free_byte_offset; 731 s->free_byte_offset += size; 732 free_in_cluster -= size; 733 if (free_in_cluster == 0) 734 s->free_byte_offset = 0; 735 if ((offset & (s->cluster_size - 1)) != 0) 736 qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1, 737 QCOW2_DISCARD_NEVER); 738 } else { 739 offset = qcow2_alloc_clusters(bs, s->cluster_size); 740 if (offset < 0) { 741 return offset; 742 } 743 cluster_offset = s->free_byte_offset & ~(s->cluster_size - 1); 744 if ((cluster_offset + s->cluster_size) == offset) { 745 /* we are lucky: contiguous data */ 746 offset = s->free_byte_offset; 747 qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1, 748 QCOW2_DISCARD_NEVER); 749 s->free_byte_offset += size; 750 } else { 751 s->free_byte_offset = offset; 752 goto redo; 753 } 754 } 755 756 /* The cluster refcount was incremented, either by qcow2_alloc_clusters() 757 * or explicitly by qcow2_update_cluster_refcount(). Refcount blocks must 758 * be flushed before the caller's L2 table updates. 759 */ 760 qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache); 761 return offset; 762 } 763 764 void qcow2_free_clusters(BlockDriverState *bs, 765 int64_t offset, int64_t size, 766 enum qcow2_discard_type type) 767 { 768 int ret; 769 770 BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_FREE); 771 ret = update_refcount(bs, offset, size, -1, type); 772 if (ret < 0) { 773 fprintf(stderr, "qcow2_free_clusters failed: %s\n", strerror(-ret)); 774 /* TODO Remember the clusters to free them later and avoid leaking */ 775 } 776 } 777 778 /* 779 * Free a cluster using its L2 entry (handles clusters of all types, e.g. 780 * normal cluster, compressed cluster, etc.) 781 */ 782 void qcow2_free_any_clusters(BlockDriverState *bs, uint64_t l2_entry, 783 int nb_clusters, enum qcow2_discard_type type) 784 { 785 BDRVQcowState *s = bs->opaque; 786 787 switch (qcow2_get_cluster_type(l2_entry)) { 788 case QCOW2_CLUSTER_COMPRESSED: 789 { 790 int nb_csectors; 791 nb_csectors = ((l2_entry >> s->csize_shift) & 792 s->csize_mask) + 1; 793 qcow2_free_clusters(bs, 794 (l2_entry & s->cluster_offset_mask) & ~511, 795 nb_csectors * 512, type); 796 } 797 break; 798 case QCOW2_CLUSTER_NORMAL: 799 qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK, 800 nb_clusters << s->cluster_bits, type); 801 break; 802 case QCOW2_CLUSTER_UNALLOCATED: 803 case QCOW2_CLUSTER_ZERO: 804 break; 805 default: 806 abort(); 807 } 808 } 809 810 811 812 /*********************************************************/ 813 /* snapshots and image creation */ 814 815 816 817 /* update the refcounts of snapshots and the copied flag */ 818 int qcow2_update_snapshot_refcount(BlockDriverState *bs, 819 int64_t l1_table_offset, int l1_size, int addend) 820 { 821 BDRVQcowState *s = bs->opaque; 822 uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, l1_allocated; 823 int64_t old_offset, old_l2_offset; 824 int i, j, l1_modified = 0, nb_csectors, refcount; 825 int ret; 826 827 l2_table = NULL; 828 l1_table = NULL; 829 l1_size2 = l1_size * sizeof(uint64_t); 830 831 s->cache_discards = true; 832 833 /* WARNING: qcow2_snapshot_goto relies on this function not using the 834 * l1_table_offset when it is the current s->l1_table_offset! Be careful 835 * when changing this! */ 836 if (l1_table_offset != s->l1_table_offset) { 837 l1_table = g_malloc0(align_offset(l1_size2, 512)); 838 l1_allocated = 1; 839 840 ret = bdrv_pread(bs->file, l1_table_offset, l1_table, l1_size2); 841 if (ret < 0) { 842 goto fail; 843 } 844 845 for(i = 0;i < l1_size; i++) 846 be64_to_cpus(&l1_table[i]); 847 } else { 848 assert(l1_size == s->l1_size); 849 l1_table = s->l1_table; 850 l1_allocated = 0; 851 } 852 853 for(i = 0; i < l1_size; i++) { 854 l2_offset = l1_table[i]; 855 if (l2_offset) { 856 old_l2_offset = l2_offset; 857 l2_offset &= L1E_OFFSET_MASK; 858 859 ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, 860 (void**) &l2_table); 861 if (ret < 0) { 862 goto fail; 863 } 864 865 for(j = 0; j < s->l2_size; j++) { 866 uint64_t cluster_index; 867 868 offset = be64_to_cpu(l2_table[j]); 869 old_offset = offset; 870 offset &= ~QCOW_OFLAG_COPIED; 871 872 switch (qcow2_get_cluster_type(offset)) { 873 case QCOW2_CLUSTER_COMPRESSED: 874 nb_csectors = ((offset >> s->csize_shift) & 875 s->csize_mask) + 1; 876 if (addend != 0) { 877 int ret; 878 ret = update_refcount(bs, 879 (offset & s->cluster_offset_mask) & ~511, 880 nb_csectors * 512, addend, 881 QCOW2_DISCARD_SNAPSHOT); 882 if (ret < 0) { 883 goto fail; 884 } 885 } 886 /* compressed clusters are never modified */ 887 refcount = 2; 888 break; 889 890 case QCOW2_CLUSTER_NORMAL: 891 case QCOW2_CLUSTER_ZERO: 892 cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits; 893 if (!cluster_index) { 894 /* unallocated */ 895 refcount = 0; 896 break; 897 } 898 if (addend != 0) { 899 refcount = qcow2_update_cluster_refcount(bs, 900 cluster_index, addend, 901 QCOW2_DISCARD_SNAPSHOT); 902 } else { 903 refcount = get_refcount(bs, cluster_index); 904 } 905 906 if (refcount < 0) { 907 ret = refcount; 908 goto fail; 909 } 910 break; 911 912 case QCOW2_CLUSTER_UNALLOCATED: 913 refcount = 0; 914 break; 915 916 default: 917 abort(); 918 } 919 920 if (refcount == 1) { 921 offset |= QCOW_OFLAG_COPIED; 922 } 923 if (offset != old_offset) { 924 if (addend > 0) { 925 qcow2_cache_set_dependency(bs, s->l2_table_cache, 926 s->refcount_block_cache); 927 } 928 l2_table[j] = cpu_to_be64(offset); 929 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); 930 } 931 } 932 933 ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 934 if (ret < 0) { 935 goto fail; 936 } 937 938 939 if (addend != 0) { 940 refcount = qcow2_update_cluster_refcount(bs, l2_offset >> 941 s->cluster_bits, addend, QCOW2_DISCARD_SNAPSHOT); 942 } else { 943 refcount = get_refcount(bs, l2_offset >> s->cluster_bits); 944 } 945 if (refcount < 0) { 946 ret = refcount; 947 goto fail; 948 } else if (refcount == 1) { 949 l2_offset |= QCOW_OFLAG_COPIED; 950 } 951 if (l2_offset != old_l2_offset) { 952 l1_table[i] = l2_offset; 953 l1_modified = 1; 954 } 955 } 956 } 957 958 ret = bdrv_flush(bs); 959 fail: 960 if (l2_table) { 961 qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 962 } 963 964 s->cache_discards = false; 965 qcow2_process_discards(bs, ret); 966 967 /* Update L1 only if it isn't deleted anyway (addend = -1) */ 968 if (ret == 0 && addend >= 0 && l1_modified) { 969 for (i = 0; i < l1_size; i++) { 970 cpu_to_be64s(&l1_table[i]); 971 } 972 973 ret = bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table, l1_size2); 974 975 for (i = 0; i < l1_size; i++) { 976 be64_to_cpus(&l1_table[i]); 977 } 978 } 979 if (l1_allocated) 980 g_free(l1_table); 981 return ret; 982 } 983 984 985 986 987 /*********************************************************/ 988 /* refcount checking functions */ 989 990 991 992 /* 993 * Increases the refcount for a range of clusters in a given refcount table. 994 * This is used to construct a temporary refcount table out of L1 and L2 tables 995 * which can be compared the the refcount table saved in the image. 996 * 997 * Modifies the number of errors in res. 998 */ 999 static void inc_refcounts(BlockDriverState *bs, 1000 BdrvCheckResult *res, 1001 uint16_t *refcount_table, 1002 int refcount_table_size, 1003 int64_t offset, int64_t size) 1004 { 1005 BDRVQcowState *s = bs->opaque; 1006 int64_t start, last, cluster_offset; 1007 int k; 1008 1009 if (size <= 0) 1010 return; 1011 1012 start = offset & ~(s->cluster_size - 1); 1013 last = (offset + size - 1) & ~(s->cluster_size - 1); 1014 for(cluster_offset = start; cluster_offset <= last; 1015 cluster_offset += s->cluster_size) { 1016 k = cluster_offset >> s->cluster_bits; 1017 if (k < 0) { 1018 fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n", 1019 cluster_offset); 1020 res->corruptions++; 1021 } else if (k >= refcount_table_size) { 1022 fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after " 1023 "the end of the image file, can't properly check refcounts.\n", 1024 cluster_offset); 1025 res->check_errors++; 1026 } else { 1027 if (++refcount_table[k] == 0) { 1028 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64 1029 "\n", cluster_offset); 1030 res->corruptions++; 1031 } 1032 } 1033 } 1034 } 1035 1036 /* Flags for check_refcounts_l1() and check_refcounts_l2() */ 1037 enum { 1038 CHECK_OFLAG_COPIED = 0x1, /* check QCOW_OFLAG_COPIED matches refcount */ 1039 CHECK_FRAG_INFO = 0x2, /* update BlockFragInfo counters */ 1040 }; 1041 1042 /* 1043 * Increases the refcount in the given refcount table for the all clusters 1044 * referenced in the L2 table. While doing so, performs some checks on L2 1045 * entries. 1046 * 1047 * Returns the number of errors found by the checks or -errno if an internal 1048 * error occurred. 1049 */ 1050 static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res, 1051 uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset, 1052 int flags) 1053 { 1054 BDRVQcowState *s = bs->opaque; 1055 uint64_t *l2_table, l2_entry; 1056 uint64_t next_contiguous_offset = 0; 1057 int i, l2_size, nb_csectors; 1058 1059 /* Read L2 table from disk */ 1060 l2_size = s->l2_size * sizeof(uint64_t); 1061 l2_table = g_malloc(l2_size); 1062 1063 if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size) 1064 goto fail; 1065 1066 /* Do the actual checks */ 1067 for(i = 0; i < s->l2_size; i++) { 1068 l2_entry = be64_to_cpu(l2_table[i]); 1069 1070 switch (qcow2_get_cluster_type(l2_entry)) { 1071 case QCOW2_CLUSTER_COMPRESSED: 1072 /* Compressed clusters don't have QCOW_OFLAG_COPIED */ 1073 if (l2_entry & QCOW_OFLAG_COPIED) { 1074 fprintf(stderr, "ERROR: cluster %" PRId64 ": " 1075 "copied flag must never be set for compressed " 1076 "clusters\n", l2_entry >> s->cluster_bits); 1077 l2_entry &= ~QCOW_OFLAG_COPIED; 1078 res->corruptions++; 1079 } 1080 1081 /* Mark cluster as used */ 1082 nb_csectors = ((l2_entry >> s->csize_shift) & 1083 s->csize_mask) + 1; 1084 l2_entry &= s->cluster_offset_mask; 1085 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1086 l2_entry & ~511, nb_csectors * 512); 1087 1088 if (flags & CHECK_FRAG_INFO) { 1089 res->bfi.allocated_clusters++; 1090 res->bfi.compressed_clusters++; 1091 1092 /* Compressed clusters are fragmented by nature. Since they 1093 * take up sub-sector space but we only have sector granularity 1094 * I/O we need to re-read the same sectors even for adjacent 1095 * compressed clusters. 1096 */ 1097 res->bfi.fragmented_clusters++; 1098 } 1099 break; 1100 1101 case QCOW2_CLUSTER_ZERO: 1102 if ((l2_entry & L2E_OFFSET_MASK) == 0) { 1103 break; 1104 } 1105 /* fall through */ 1106 1107 case QCOW2_CLUSTER_NORMAL: 1108 { 1109 uint64_t offset = l2_entry & L2E_OFFSET_MASK; 1110 1111 if (flags & CHECK_FRAG_INFO) { 1112 res->bfi.allocated_clusters++; 1113 if (next_contiguous_offset && 1114 offset != next_contiguous_offset) { 1115 res->bfi.fragmented_clusters++; 1116 } 1117 next_contiguous_offset = offset + s->cluster_size; 1118 } 1119 1120 /* Mark cluster as used */ 1121 inc_refcounts(bs, res, refcount_table,refcount_table_size, 1122 offset, s->cluster_size); 1123 1124 /* Correct offsets are cluster aligned */ 1125 if (offset & (s->cluster_size - 1)) { 1126 fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not " 1127 "properly aligned; L2 entry corrupted.\n", offset); 1128 res->corruptions++; 1129 } 1130 break; 1131 } 1132 1133 case QCOW2_CLUSTER_UNALLOCATED: 1134 break; 1135 1136 default: 1137 abort(); 1138 } 1139 } 1140 1141 g_free(l2_table); 1142 return 0; 1143 1144 fail: 1145 fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n"); 1146 g_free(l2_table); 1147 return -EIO; 1148 } 1149 1150 /* 1151 * Increases the refcount for the L1 table, its L2 tables and all referenced 1152 * clusters in the given refcount table. While doing so, performs some checks 1153 * on L1 and L2 entries. 1154 * 1155 * Returns the number of errors found by the checks or -errno if an internal 1156 * error occurred. 1157 */ 1158 static int check_refcounts_l1(BlockDriverState *bs, 1159 BdrvCheckResult *res, 1160 uint16_t *refcount_table, 1161 int refcount_table_size, 1162 int64_t l1_table_offset, int l1_size, 1163 int flags) 1164 { 1165 BDRVQcowState *s = bs->opaque; 1166 uint64_t *l1_table, l2_offset, l1_size2; 1167 int i, ret; 1168 1169 l1_size2 = l1_size * sizeof(uint64_t); 1170 1171 /* Mark L1 table as used */ 1172 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1173 l1_table_offset, l1_size2); 1174 1175 /* Read L1 table entries from disk */ 1176 if (l1_size2 == 0) { 1177 l1_table = NULL; 1178 } else { 1179 l1_table = g_malloc(l1_size2); 1180 if (bdrv_pread(bs->file, l1_table_offset, 1181 l1_table, l1_size2) != l1_size2) 1182 goto fail; 1183 for(i = 0;i < l1_size; i++) 1184 be64_to_cpus(&l1_table[i]); 1185 } 1186 1187 /* Do the actual checks */ 1188 for(i = 0; i < l1_size; i++) { 1189 l2_offset = l1_table[i]; 1190 if (l2_offset) { 1191 /* Mark L2 table as used */ 1192 l2_offset &= L1E_OFFSET_MASK; 1193 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1194 l2_offset, s->cluster_size); 1195 1196 /* L2 tables are cluster aligned */ 1197 if (l2_offset & (s->cluster_size - 1)) { 1198 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not " 1199 "cluster aligned; L1 entry corrupted\n", l2_offset); 1200 res->corruptions++; 1201 } 1202 1203 /* Process and check L2 entries */ 1204 ret = check_refcounts_l2(bs, res, refcount_table, 1205 refcount_table_size, l2_offset, flags); 1206 if (ret < 0) { 1207 goto fail; 1208 } 1209 } 1210 } 1211 g_free(l1_table); 1212 return 0; 1213 1214 fail: 1215 fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n"); 1216 res->check_errors++; 1217 g_free(l1_table); 1218 return -EIO; 1219 } 1220 1221 /* 1222 * Checks the OFLAG_COPIED flag for all L1 and L2 entries. 1223 * 1224 * This function does not print an error message nor does it increment 1225 * check_errors if get_refcount fails (this is because such an error will have 1226 * been already detected and sufficiently signaled by the calling function 1227 * (qcow2_check_refcounts) by the time this function is called). 1228 */ 1229 static int check_oflag_copied(BlockDriverState *bs, BdrvCheckResult *res, 1230 BdrvCheckMode fix) 1231 { 1232 BDRVQcowState *s = bs->opaque; 1233 uint64_t *l2_table = qemu_blockalign(bs, s->cluster_size); 1234 int ret; 1235 int refcount; 1236 int i, j; 1237 1238 for (i = 0; i < s->l1_size; i++) { 1239 uint64_t l1_entry = s->l1_table[i]; 1240 uint64_t l2_offset = l1_entry & L1E_OFFSET_MASK; 1241 bool l2_dirty = false; 1242 1243 if (!l2_offset) { 1244 continue; 1245 } 1246 1247 refcount = get_refcount(bs, l2_offset >> s->cluster_bits); 1248 if (refcount < 0) { 1249 /* don't print message nor increment check_errors */ 1250 continue; 1251 } 1252 if ((refcount == 1) != ((l1_entry & QCOW_OFLAG_COPIED) != 0)) { 1253 fprintf(stderr, "%s OFLAG_COPIED L2 cluster: l1_index=%d " 1254 "l1_entry=%" PRIx64 " refcount=%d\n", 1255 fix & BDRV_FIX_ERRORS ? "Repairing" : 1256 "ERROR", 1257 i, l1_entry, refcount); 1258 if (fix & BDRV_FIX_ERRORS) { 1259 s->l1_table[i] = refcount == 1 1260 ? l1_entry | QCOW_OFLAG_COPIED 1261 : l1_entry & ~QCOW_OFLAG_COPIED; 1262 ret = qcow2_write_l1_entry(bs, i); 1263 if (ret < 0) { 1264 res->check_errors++; 1265 goto fail; 1266 } 1267 res->corruptions_fixed++; 1268 } else { 1269 res->corruptions++; 1270 } 1271 } 1272 1273 ret = bdrv_pread(bs->file, l2_offset, l2_table, 1274 s->l2_size * sizeof(uint64_t)); 1275 if (ret < 0) { 1276 fprintf(stderr, "ERROR: Could not read L2 table: %s\n", 1277 strerror(-ret)); 1278 res->check_errors++; 1279 goto fail; 1280 } 1281 1282 for (j = 0; j < s->l2_size; j++) { 1283 uint64_t l2_entry = be64_to_cpu(l2_table[j]); 1284 uint64_t data_offset = l2_entry & L2E_OFFSET_MASK; 1285 int cluster_type = qcow2_get_cluster_type(l2_entry); 1286 1287 if ((cluster_type == QCOW2_CLUSTER_NORMAL) || 1288 ((cluster_type == QCOW2_CLUSTER_ZERO) && (data_offset != 0))) { 1289 refcount = get_refcount(bs, data_offset >> s->cluster_bits); 1290 if (refcount < 0) { 1291 /* don't print message nor increment check_errors */ 1292 continue; 1293 } 1294 if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) { 1295 fprintf(stderr, "%s OFLAG_COPIED data cluster: " 1296 "l2_entry=%" PRIx64 " refcount=%d\n", 1297 fix & BDRV_FIX_ERRORS ? "Repairing" : 1298 "ERROR", 1299 l2_entry, refcount); 1300 if (fix & BDRV_FIX_ERRORS) { 1301 l2_table[j] = cpu_to_be64(refcount == 1 1302 ? l2_entry | QCOW_OFLAG_COPIED 1303 : l2_entry & ~QCOW_OFLAG_COPIED); 1304 l2_dirty = true; 1305 res->corruptions_fixed++; 1306 } else { 1307 res->corruptions++; 1308 } 1309 } 1310 } 1311 } 1312 1313 if (l2_dirty) { 1314 ret = qcow2_pre_write_overlap_check(bs, 1315 QCOW2_OL_DEFAULT & ~QCOW2_OL_ACTIVE_L2, l2_offset, 1316 s->cluster_size); 1317 if (ret < 0) { 1318 fprintf(stderr, "ERROR: Could not write L2 table; metadata " 1319 "overlap check failed: %s\n", strerror(-ret)); 1320 res->check_errors++; 1321 goto fail; 1322 } 1323 1324 ret = bdrv_pwrite(bs->file, l2_offset, l2_table, s->cluster_size); 1325 if (ret < 0) { 1326 fprintf(stderr, "ERROR: Could not write L2 table: %s\n", 1327 strerror(-ret)); 1328 res->check_errors++; 1329 goto fail; 1330 } 1331 } 1332 } 1333 1334 ret = 0; 1335 1336 fail: 1337 qemu_vfree(l2_table); 1338 return ret; 1339 } 1340 1341 /* 1342 * Writes one sector of the refcount table to the disk 1343 */ 1344 #define RT_ENTRIES_PER_SECTOR (512 / sizeof(uint64_t)) 1345 static int write_reftable_entry(BlockDriverState *bs, int rt_index) 1346 { 1347 BDRVQcowState *s = bs->opaque; 1348 uint64_t buf[RT_ENTRIES_PER_SECTOR]; 1349 int rt_start_index; 1350 int i, ret; 1351 1352 rt_start_index = rt_index & ~(RT_ENTRIES_PER_SECTOR - 1); 1353 for (i = 0; i < RT_ENTRIES_PER_SECTOR; i++) { 1354 buf[i] = cpu_to_be64(s->refcount_table[rt_start_index + i]); 1355 } 1356 1357 ret = qcow2_pre_write_overlap_check(bs, 1358 QCOW2_OL_DEFAULT & ~QCOW2_OL_REFCOUNT_TABLE, 1359 s->refcount_table_offset + rt_start_index * sizeof(uint64_t), 1360 sizeof(buf)); 1361 if (ret < 0) { 1362 return ret; 1363 } 1364 1365 BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_UPDATE); 1366 ret = bdrv_pwrite_sync(bs->file, s->refcount_table_offset + 1367 rt_start_index * sizeof(uint64_t), buf, sizeof(buf)); 1368 if (ret < 0) { 1369 return ret; 1370 } 1371 1372 return 0; 1373 } 1374 1375 /* 1376 * Allocates a new cluster for the given refcount block (represented by its 1377 * offset in the image file) and copies the current content there. This function 1378 * does _not_ decrement the reference count for the currently occupied cluster. 1379 * 1380 * This function prints an informative message to stderr on error (and returns 1381 * -errno); on success, 0 is returned. 1382 */ 1383 static int64_t realloc_refcount_block(BlockDriverState *bs, int reftable_index, 1384 uint64_t offset) 1385 { 1386 BDRVQcowState *s = bs->opaque; 1387 int64_t new_offset = 0; 1388 void *refcount_block = NULL; 1389 int ret; 1390 1391 /* allocate new refcount block */ 1392 new_offset = qcow2_alloc_clusters(bs, s->cluster_size); 1393 if (new_offset < 0) { 1394 fprintf(stderr, "Could not allocate new cluster: %s\n", 1395 strerror(-new_offset)); 1396 ret = new_offset; 1397 goto fail; 1398 } 1399 1400 /* fetch current refcount block content */ 1401 ret = qcow2_cache_get(bs, s->refcount_block_cache, offset, &refcount_block); 1402 if (ret < 0) { 1403 fprintf(stderr, "Could not fetch refcount block: %s\n", strerror(-ret)); 1404 goto fail; 1405 } 1406 1407 /* new block has not yet been entered into refcount table, therefore it is 1408 * no refcount block yet (regarding this check) */ 1409 ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT, new_offset, 1410 s->cluster_size); 1411 if (ret < 0) { 1412 fprintf(stderr, "Could not write refcount block; metadata overlap " 1413 "check failed: %s\n", strerror(-ret)); 1414 /* the image will be marked corrupt, so don't even attempt on freeing 1415 * the cluster */ 1416 new_offset = 0; 1417 goto fail; 1418 } 1419 1420 /* write to new block */ 1421 ret = bdrv_write(bs->file, new_offset / BDRV_SECTOR_SIZE, refcount_block, 1422 s->cluster_sectors); 1423 if (ret < 0) { 1424 fprintf(stderr, "Could not write refcount block: %s\n", strerror(-ret)); 1425 goto fail; 1426 } 1427 1428 /* update refcount table */ 1429 assert(!(new_offset & (s->cluster_size - 1))); 1430 s->refcount_table[reftable_index] = new_offset; 1431 ret = write_reftable_entry(bs, reftable_index); 1432 if (ret < 0) { 1433 fprintf(stderr, "Could not update refcount table: %s\n", 1434 strerror(-ret)); 1435 goto fail; 1436 } 1437 1438 fail: 1439 if (new_offset && (ret < 0)) { 1440 qcow2_free_clusters(bs, new_offset, s->cluster_size, 1441 QCOW2_DISCARD_ALWAYS); 1442 } 1443 if (refcount_block) { 1444 if (ret < 0) { 1445 qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block); 1446 } else { 1447 ret = qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block); 1448 } 1449 } 1450 if (ret < 0) { 1451 return ret; 1452 } 1453 return new_offset; 1454 } 1455 1456 /* 1457 * Checks an image for refcount consistency. 1458 * 1459 * Returns 0 if no errors are found, the number of errors in case the image is 1460 * detected as corrupted, and -errno when an internal error occurred. 1461 */ 1462 int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res, 1463 BdrvCheckMode fix) 1464 { 1465 BDRVQcowState *s = bs->opaque; 1466 int64_t size, i, highest_cluster; 1467 int nb_clusters, refcount1, refcount2; 1468 QCowSnapshot *sn; 1469 uint16_t *refcount_table; 1470 int ret; 1471 1472 size = bdrv_getlength(bs->file); 1473 nb_clusters = size_to_clusters(s, size); 1474 refcount_table = g_malloc0(nb_clusters * sizeof(uint16_t)); 1475 1476 res->bfi.total_clusters = 1477 size_to_clusters(s, bs->total_sectors * BDRV_SECTOR_SIZE); 1478 1479 /* header */ 1480 inc_refcounts(bs, res, refcount_table, nb_clusters, 1481 0, s->cluster_size); 1482 1483 /* current L1 table */ 1484 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1485 s->l1_table_offset, s->l1_size, 1486 CHECK_OFLAG_COPIED | CHECK_FRAG_INFO); 1487 if (ret < 0) { 1488 goto fail; 1489 } 1490 1491 /* snapshots */ 1492 for(i = 0; i < s->nb_snapshots; i++) { 1493 sn = s->snapshots + i; 1494 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1495 sn->l1_table_offset, sn->l1_size, 0); 1496 if (ret < 0) { 1497 goto fail; 1498 } 1499 } 1500 inc_refcounts(bs, res, refcount_table, nb_clusters, 1501 s->snapshots_offset, s->snapshots_size); 1502 1503 /* refcount data */ 1504 inc_refcounts(bs, res, refcount_table, nb_clusters, 1505 s->refcount_table_offset, 1506 s->refcount_table_size * sizeof(uint64_t)); 1507 1508 for(i = 0; i < s->refcount_table_size; i++) { 1509 uint64_t offset, cluster; 1510 offset = s->refcount_table[i]; 1511 cluster = offset >> s->cluster_bits; 1512 1513 /* Refcount blocks are cluster aligned */ 1514 if (offset & (s->cluster_size - 1)) { 1515 fprintf(stderr, "ERROR refcount block %" PRId64 " is not " 1516 "cluster aligned; refcount table entry corrupted\n", i); 1517 res->corruptions++; 1518 continue; 1519 } 1520 1521 if (cluster >= nb_clusters) { 1522 fprintf(stderr, "ERROR refcount block %" PRId64 1523 " is outside image\n", i); 1524 res->corruptions++; 1525 continue; 1526 } 1527 1528 if (offset != 0) { 1529 inc_refcounts(bs, res, refcount_table, nb_clusters, 1530 offset, s->cluster_size); 1531 if (refcount_table[cluster] != 1) { 1532 fprintf(stderr, "%s refcount block %" PRId64 1533 " refcount=%d\n", 1534 fix & BDRV_FIX_ERRORS ? "Repairing" : 1535 "ERROR", 1536 i, refcount_table[cluster]); 1537 1538 if (fix & BDRV_FIX_ERRORS) { 1539 int64_t new_offset; 1540 1541 new_offset = realloc_refcount_block(bs, i, offset); 1542 if (new_offset < 0) { 1543 res->corruptions++; 1544 continue; 1545 } 1546 1547 /* update refcounts */ 1548 if ((new_offset >> s->cluster_bits) >= nb_clusters) { 1549 /* increase refcount_table size if necessary */ 1550 int old_nb_clusters = nb_clusters; 1551 nb_clusters = (new_offset >> s->cluster_bits) + 1; 1552 refcount_table = g_realloc(refcount_table, 1553 nb_clusters * sizeof(uint16_t)); 1554 memset(&refcount_table[old_nb_clusters], 0, (nb_clusters 1555 - old_nb_clusters) * sizeof(uint16_t)); 1556 } 1557 refcount_table[cluster]--; 1558 inc_refcounts(bs, res, refcount_table, nb_clusters, 1559 new_offset, s->cluster_size); 1560 1561 res->corruptions_fixed++; 1562 } else { 1563 res->corruptions++; 1564 } 1565 } 1566 } 1567 } 1568 1569 /* compare ref counts */ 1570 for (i = 0, highest_cluster = 0; i < nb_clusters; i++) { 1571 refcount1 = get_refcount(bs, i); 1572 if (refcount1 < 0) { 1573 fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n", 1574 i, strerror(-refcount1)); 1575 res->check_errors++; 1576 continue; 1577 } 1578 1579 refcount2 = refcount_table[i]; 1580 1581 if (refcount1 > 0 || refcount2 > 0) { 1582 highest_cluster = i; 1583 } 1584 1585 if (refcount1 != refcount2) { 1586 1587 /* Check if we're allowed to fix the mismatch */ 1588 int *num_fixed = NULL; 1589 if (refcount1 > refcount2 && (fix & BDRV_FIX_LEAKS)) { 1590 num_fixed = &res->leaks_fixed; 1591 } else if (refcount1 < refcount2 && (fix & BDRV_FIX_ERRORS)) { 1592 num_fixed = &res->corruptions_fixed; 1593 } 1594 1595 fprintf(stderr, "%s cluster %" PRId64 " refcount=%d reference=%d\n", 1596 num_fixed != NULL ? "Repairing" : 1597 refcount1 < refcount2 ? "ERROR" : 1598 "Leaked", 1599 i, refcount1, refcount2); 1600 1601 if (num_fixed) { 1602 ret = update_refcount(bs, i << s->cluster_bits, 1, 1603 refcount2 - refcount1, 1604 QCOW2_DISCARD_ALWAYS); 1605 if (ret >= 0) { 1606 (*num_fixed)++; 1607 continue; 1608 } 1609 } 1610 1611 /* And if we couldn't, print an error */ 1612 if (refcount1 < refcount2) { 1613 res->corruptions++; 1614 } else { 1615 res->leaks++; 1616 } 1617 } 1618 } 1619 1620 /* check OFLAG_COPIED */ 1621 ret = check_oflag_copied(bs, res, fix); 1622 if (ret < 0) { 1623 goto fail; 1624 } 1625 1626 res->image_end_offset = (highest_cluster + 1) * s->cluster_size; 1627 ret = 0; 1628 1629 fail: 1630 g_free(refcount_table); 1631 1632 return ret; 1633 } 1634 1635 #define overlaps_with(ofs, sz) \ 1636 ranges_overlap(offset, size, ofs, sz) 1637 1638 /* 1639 * Checks if the given offset into the image file is actually free to use by 1640 * looking for overlaps with important metadata sections (L1/L2 tables etc.), 1641 * i.e. a sanity check without relying on the refcount tables. 1642 * 1643 * The chk parameter specifies exactly what checks to perform (being a bitmask 1644 * of QCow2MetadataOverlap values). 1645 * 1646 * Returns: 1647 * - 0 if writing to this offset will not affect the mentioned metadata 1648 * - a positive QCow2MetadataOverlap value indicating one overlapping section 1649 * - a negative value (-errno) indicating an error while performing a check, 1650 * e.g. when bdrv_read failed on QCOW2_OL_INACTIVE_L2 1651 */ 1652 int qcow2_check_metadata_overlap(BlockDriverState *bs, int chk, int64_t offset, 1653 int64_t size) 1654 { 1655 BDRVQcowState *s = bs->opaque; 1656 int i, j; 1657 1658 if (!size) { 1659 return 0; 1660 } 1661 1662 if (chk & QCOW2_OL_MAIN_HEADER) { 1663 if (offset < s->cluster_size) { 1664 return QCOW2_OL_MAIN_HEADER; 1665 } 1666 } 1667 1668 /* align range to test to cluster boundaries */ 1669 size = align_offset(offset_into_cluster(s, offset) + size, s->cluster_size); 1670 offset = start_of_cluster(s, offset); 1671 1672 if ((chk & QCOW2_OL_ACTIVE_L1) && s->l1_size) { 1673 if (overlaps_with(s->l1_table_offset, s->l1_size * sizeof(uint64_t))) { 1674 return QCOW2_OL_ACTIVE_L1; 1675 } 1676 } 1677 1678 if ((chk & QCOW2_OL_REFCOUNT_TABLE) && s->refcount_table_size) { 1679 if (overlaps_with(s->refcount_table_offset, 1680 s->refcount_table_size * sizeof(uint64_t))) { 1681 return QCOW2_OL_REFCOUNT_TABLE; 1682 } 1683 } 1684 1685 if ((chk & QCOW2_OL_SNAPSHOT_TABLE) && s->snapshots_size) { 1686 if (overlaps_with(s->snapshots_offset, s->snapshots_size)) { 1687 return QCOW2_OL_SNAPSHOT_TABLE; 1688 } 1689 } 1690 1691 if ((chk & QCOW2_OL_INACTIVE_L1) && s->snapshots) { 1692 for (i = 0; i < s->nb_snapshots; i++) { 1693 if (s->snapshots[i].l1_size && 1694 overlaps_with(s->snapshots[i].l1_table_offset, 1695 s->snapshots[i].l1_size * sizeof(uint64_t))) { 1696 return QCOW2_OL_INACTIVE_L1; 1697 } 1698 } 1699 } 1700 1701 if ((chk & QCOW2_OL_ACTIVE_L2) && s->l1_table) { 1702 for (i = 0; i < s->l1_size; i++) { 1703 if ((s->l1_table[i] & L1E_OFFSET_MASK) && 1704 overlaps_with(s->l1_table[i] & L1E_OFFSET_MASK, 1705 s->cluster_size)) { 1706 return QCOW2_OL_ACTIVE_L2; 1707 } 1708 } 1709 } 1710 1711 if ((chk & QCOW2_OL_REFCOUNT_BLOCK) && s->refcount_table) { 1712 for (i = 0; i < s->refcount_table_size; i++) { 1713 if ((s->refcount_table[i] & REFT_OFFSET_MASK) && 1714 overlaps_with(s->refcount_table[i] & REFT_OFFSET_MASK, 1715 s->cluster_size)) { 1716 return QCOW2_OL_REFCOUNT_BLOCK; 1717 } 1718 } 1719 } 1720 1721 if ((chk & QCOW2_OL_INACTIVE_L2) && s->snapshots) { 1722 for (i = 0; i < s->nb_snapshots; i++) { 1723 uint64_t l1_ofs = s->snapshots[i].l1_table_offset; 1724 uint32_t l1_sz = s->snapshots[i].l1_size; 1725 uint64_t *l1 = g_malloc(l1_sz * sizeof(uint64_t)); 1726 int ret; 1727 1728 ret = bdrv_read(bs->file, l1_ofs / BDRV_SECTOR_SIZE, (uint8_t *)l1, 1729 l1_sz * sizeof(uint64_t) / BDRV_SECTOR_SIZE); 1730 1731 if (ret < 0) { 1732 g_free(l1); 1733 return ret; 1734 } 1735 1736 for (j = 0; j < l1_sz; j++) { 1737 if ((l1[j] & L1E_OFFSET_MASK) && 1738 overlaps_with(l1[j] & L1E_OFFSET_MASK, s->cluster_size)) { 1739 g_free(l1); 1740 return QCOW2_OL_INACTIVE_L2; 1741 } 1742 } 1743 1744 g_free(l1); 1745 } 1746 } 1747 1748 return 0; 1749 } 1750 1751 static const char *metadata_ol_names[] = { 1752 [QCOW2_OL_MAIN_HEADER_BITNR] = "qcow2_header", 1753 [QCOW2_OL_ACTIVE_L1_BITNR] = "active L1 table", 1754 [QCOW2_OL_ACTIVE_L2_BITNR] = "active L2 table", 1755 [QCOW2_OL_REFCOUNT_TABLE_BITNR] = "refcount table", 1756 [QCOW2_OL_REFCOUNT_BLOCK_BITNR] = "refcount block", 1757 [QCOW2_OL_SNAPSHOT_TABLE_BITNR] = "snapshot table", 1758 [QCOW2_OL_INACTIVE_L1_BITNR] = "inactive L1 table", 1759 [QCOW2_OL_INACTIVE_L2_BITNR] = "inactive L2 table", 1760 }; 1761 1762 /* 1763 * First performs a check for metadata overlaps (through 1764 * qcow2_check_metadata_overlap); if that fails with a negative value (error 1765 * while performing a check), that value is returned. If an impending overlap 1766 * is detected, the BDS will be made unusable, the qcow2 file marked corrupt 1767 * and -EIO returned. 1768 * 1769 * Returns 0 if there were neither overlaps nor errors while checking for 1770 * overlaps; or a negative value (-errno) on error. 1771 */ 1772 int qcow2_pre_write_overlap_check(BlockDriverState *bs, int chk, int64_t offset, 1773 int64_t size) 1774 { 1775 int ret = qcow2_check_metadata_overlap(bs, chk, offset, size); 1776 1777 if (ret < 0) { 1778 return ret; 1779 } else if (ret > 0) { 1780 int metadata_ol_bitnr = ffs(ret) - 1; 1781 char *message; 1782 QObject *data; 1783 1784 assert(metadata_ol_bitnr < QCOW2_OL_MAX_BITNR); 1785 1786 fprintf(stderr, "qcow2: Preventing invalid write on metadata (overlaps " 1787 "with %s); image marked as corrupt.\n", 1788 metadata_ol_names[metadata_ol_bitnr]); 1789 message = g_strdup_printf("Prevented %s overwrite", 1790 metadata_ol_names[metadata_ol_bitnr]); 1791 data = qobject_from_jsonf("{ 'device': %s, 'msg': %s, 'offset': %" 1792 PRId64 ", 'size': %" PRId64 " }", bs->device_name, message, 1793 offset, size); 1794 monitor_protocol_event(QEVENT_BLOCK_IMAGE_CORRUPTED, data); 1795 g_free(message); 1796 qobject_decref(data); 1797 1798 qcow2_mark_corrupt(bs); 1799 bs->drv = NULL; /* make BDS unusable */ 1800 return -EIO; 1801 } 1802 1803 return 0; 1804 } 1805