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 static int 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 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 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 update_cluster_refcount(). Refcount blocks must be 758 * 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 = update_cluster_refcount(bs, cluster_index, addend, 900 QCOW2_DISCARD_SNAPSHOT); 901 } else { 902 refcount = get_refcount(bs, cluster_index); 903 } 904 905 if (refcount < 0) { 906 ret = refcount; 907 goto fail; 908 } 909 break; 910 911 case QCOW2_CLUSTER_UNALLOCATED: 912 refcount = 0; 913 break; 914 915 default: 916 abort(); 917 } 918 919 if (refcount == 1) { 920 offset |= QCOW_OFLAG_COPIED; 921 } 922 if (offset != old_offset) { 923 if (addend > 0) { 924 qcow2_cache_set_dependency(bs, s->l2_table_cache, 925 s->refcount_block_cache); 926 } 927 l2_table[j] = cpu_to_be64(offset); 928 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); 929 } 930 } 931 932 ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 933 if (ret < 0) { 934 goto fail; 935 } 936 937 938 if (addend != 0) { 939 refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend, 940 QCOW2_DISCARD_SNAPSHOT); 941 } else { 942 refcount = get_refcount(bs, l2_offset >> s->cluster_bits); 943 } 944 if (refcount < 0) { 945 ret = refcount; 946 goto fail; 947 } else if (refcount == 1) { 948 l2_offset |= QCOW_OFLAG_COPIED; 949 } 950 if (l2_offset != old_l2_offset) { 951 l1_table[i] = l2_offset; 952 l1_modified = 1; 953 } 954 } 955 } 956 957 ret = bdrv_flush(bs); 958 fail: 959 if (l2_table) { 960 qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); 961 } 962 963 s->cache_discards = false; 964 qcow2_process_discards(bs, ret); 965 966 /* Update L1 only if it isn't deleted anyway (addend = -1) */ 967 if (ret == 0 && addend >= 0 && l1_modified) { 968 for (i = 0; i < l1_size; i++) { 969 cpu_to_be64s(&l1_table[i]); 970 } 971 972 ret = bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table, l1_size2); 973 974 for (i = 0; i < l1_size; i++) { 975 be64_to_cpus(&l1_table[i]); 976 } 977 } 978 if (l1_allocated) 979 g_free(l1_table); 980 return ret; 981 } 982 983 984 985 986 /*********************************************************/ 987 /* refcount checking functions */ 988 989 990 991 /* 992 * Increases the refcount for a range of clusters in a given refcount table. 993 * This is used to construct a temporary refcount table out of L1 and L2 tables 994 * which can be compared the the refcount table saved in the image. 995 * 996 * Modifies the number of errors in res. 997 */ 998 static void inc_refcounts(BlockDriverState *bs, 999 BdrvCheckResult *res, 1000 uint16_t *refcount_table, 1001 int refcount_table_size, 1002 int64_t offset, int64_t size) 1003 { 1004 BDRVQcowState *s = bs->opaque; 1005 int64_t start, last, cluster_offset; 1006 int k; 1007 1008 if (size <= 0) 1009 return; 1010 1011 start = offset & ~(s->cluster_size - 1); 1012 last = (offset + size - 1) & ~(s->cluster_size - 1); 1013 for(cluster_offset = start; cluster_offset <= last; 1014 cluster_offset += s->cluster_size) { 1015 k = cluster_offset >> s->cluster_bits; 1016 if (k < 0) { 1017 fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n", 1018 cluster_offset); 1019 res->corruptions++; 1020 } else if (k >= refcount_table_size) { 1021 fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after " 1022 "the end of the image file, can't properly check refcounts.\n", 1023 cluster_offset); 1024 res->check_errors++; 1025 } else { 1026 if (++refcount_table[k] == 0) { 1027 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64 1028 "\n", cluster_offset); 1029 res->corruptions++; 1030 } 1031 } 1032 } 1033 } 1034 1035 /* Flags for check_refcounts_l1() and check_refcounts_l2() */ 1036 enum { 1037 CHECK_OFLAG_COPIED = 0x1, /* check QCOW_OFLAG_COPIED matches refcount */ 1038 CHECK_FRAG_INFO = 0x2, /* update BlockFragInfo counters */ 1039 }; 1040 1041 /* 1042 * Increases the refcount in the given refcount table for the all clusters 1043 * referenced in the L2 table. While doing so, performs some checks on L2 1044 * entries. 1045 * 1046 * Returns the number of errors found by the checks or -errno if an internal 1047 * error occurred. 1048 */ 1049 static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res, 1050 uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset, 1051 int flags) 1052 { 1053 BDRVQcowState *s = bs->opaque; 1054 uint64_t *l2_table, l2_entry; 1055 uint64_t next_contiguous_offset = 0; 1056 int i, l2_size, nb_csectors; 1057 1058 /* Read L2 table from disk */ 1059 l2_size = s->l2_size * sizeof(uint64_t); 1060 l2_table = g_malloc(l2_size); 1061 1062 if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size) 1063 goto fail; 1064 1065 /* Do the actual checks */ 1066 for(i = 0; i < s->l2_size; i++) { 1067 l2_entry = be64_to_cpu(l2_table[i]); 1068 1069 switch (qcow2_get_cluster_type(l2_entry)) { 1070 case QCOW2_CLUSTER_COMPRESSED: 1071 /* Compressed clusters don't have QCOW_OFLAG_COPIED */ 1072 if (l2_entry & QCOW_OFLAG_COPIED) { 1073 fprintf(stderr, "ERROR: cluster %" PRId64 ": " 1074 "copied flag must never be set for compressed " 1075 "clusters\n", l2_entry >> s->cluster_bits); 1076 l2_entry &= ~QCOW_OFLAG_COPIED; 1077 res->corruptions++; 1078 } 1079 1080 /* Mark cluster as used */ 1081 nb_csectors = ((l2_entry >> s->csize_shift) & 1082 s->csize_mask) + 1; 1083 l2_entry &= s->cluster_offset_mask; 1084 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1085 l2_entry & ~511, nb_csectors * 512); 1086 1087 if (flags & CHECK_FRAG_INFO) { 1088 res->bfi.allocated_clusters++; 1089 res->bfi.compressed_clusters++; 1090 1091 /* Compressed clusters are fragmented by nature. Since they 1092 * take up sub-sector space but we only have sector granularity 1093 * I/O we need to re-read the same sectors even for adjacent 1094 * compressed clusters. 1095 */ 1096 res->bfi.fragmented_clusters++; 1097 } 1098 break; 1099 1100 case QCOW2_CLUSTER_ZERO: 1101 if ((l2_entry & L2E_OFFSET_MASK) == 0) { 1102 break; 1103 } 1104 /* fall through */ 1105 1106 case QCOW2_CLUSTER_NORMAL: 1107 { 1108 uint64_t offset = l2_entry & L2E_OFFSET_MASK; 1109 1110 if (flags & CHECK_FRAG_INFO) { 1111 res->bfi.allocated_clusters++; 1112 if (next_contiguous_offset && 1113 offset != next_contiguous_offset) { 1114 res->bfi.fragmented_clusters++; 1115 } 1116 next_contiguous_offset = offset + s->cluster_size; 1117 } 1118 1119 /* Mark cluster as used */ 1120 inc_refcounts(bs, res, refcount_table,refcount_table_size, 1121 offset, s->cluster_size); 1122 1123 /* Correct offsets are cluster aligned */ 1124 if (offset & (s->cluster_size - 1)) { 1125 fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not " 1126 "properly aligned; L2 entry corrupted.\n", offset); 1127 res->corruptions++; 1128 } 1129 break; 1130 } 1131 1132 case QCOW2_CLUSTER_UNALLOCATED: 1133 break; 1134 1135 default: 1136 abort(); 1137 } 1138 } 1139 1140 g_free(l2_table); 1141 return 0; 1142 1143 fail: 1144 fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n"); 1145 g_free(l2_table); 1146 return -EIO; 1147 } 1148 1149 /* 1150 * Increases the refcount for the L1 table, its L2 tables and all referenced 1151 * clusters in the given refcount table. While doing so, performs some checks 1152 * on L1 and L2 entries. 1153 * 1154 * Returns the number of errors found by the checks or -errno if an internal 1155 * error occurred. 1156 */ 1157 static int check_refcounts_l1(BlockDriverState *bs, 1158 BdrvCheckResult *res, 1159 uint16_t *refcount_table, 1160 int refcount_table_size, 1161 int64_t l1_table_offset, int l1_size, 1162 int flags) 1163 { 1164 BDRVQcowState *s = bs->opaque; 1165 uint64_t *l1_table, l2_offset, l1_size2; 1166 int i, ret; 1167 1168 l1_size2 = l1_size * sizeof(uint64_t); 1169 1170 /* Mark L1 table as used */ 1171 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1172 l1_table_offset, l1_size2); 1173 1174 /* Read L1 table entries from disk */ 1175 if (l1_size2 == 0) { 1176 l1_table = NULL; 1177 } else { 1178 l1_table = g_malloc(l1_size2); 1179 if (bdrv_pread(bs->file, l1_table_offset, 1180 l1_table, l1_size2) != l1_size2) 1181 goto fail; 1182 for(i = 0;i < l1_size; i++) 1183 be64_to_cpus(&l1_table[i]); 1184 } 1185 1186 /* Do the actual checks */ 1187 for(i = 0; i < l1_size; i++) { 1188 l2_offset = l1_table[i]; 1189 if (l2_offset) { 1190 /* Mark L2 table as used */ 1191 l2_offset &= L1E_OFFSET_MASK; 1192 inc_refcounts(bs, res, refcount_table, refcount_table_size, 1193 l2_offset, s->cluster_size); 1194 1195 /* L2 tables are cluster aligned */ 1196 if (l2_offset & (s->cluster_size - 1)) { 1197 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not " 1198 "cluster aligned; L1 entry corrupted\n", l2_offset); 1199 res->corruptions++; 1200 } 1201 1202 /* Process and check L2 entries */ 1203 ret = check_refcounts_l2(bs, res, refcount_table, 1204 refcount_table_size, l2_offset, flags); 1205 if (ret < 0) { 1206 goto fail; 1207 } 1208 } 1209 } 1210 g_free(l1_table); 1211 return 0; 1212 1213 fail: 1214 fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n"); 1215 res->check_errors++; 1216 g_free(l1_table); 1217 return -EIO; 1218 } 1219 1220 /* 1221 * Checks the OFLAG_COPIED flag for all L1 and L2 entries. 1222 * 1223 * This function does not print an error message nor does it increment 1224 * check_errors if get_refcount fails (this is because such an error will have 1225 * been already detected and sufficiently signaled by the calling function 1226 * (qcow2_check_refcounts) by the time this function is called). 1227 */ 1228 static int check_oflag_copied(BlockDriverState *bs, BdrvCheckResult *res, 1229 BdrvCheckMode fix) 1230 { 1231 BDRVQcowState *s = bs->opaque; 1232 uint64_t *l2_table = qemu_blockalign(bs, s->cluster_size); 1233 int ret; 1234 int refcount; 1235 int i, j; 1236 1237 for (i = 0; i < s->l1_size; i++) { 1238 uint64_t l1_entry = s->l1_table[i]; 1239 uint64_t l2_offset = l1_entry & L1E_OFFSET_MASK; 1240 bool l2_dirty = false; 1241 1242 if (!l2_offset) { 1243 continue; 1244 } 1245 1246 refcount = get_refcount(bs, l2_offset >> s->cluster_bits); 1247 if (refcount < 0) { 1248 /* don't print message nor increment check_errors */ 1249 continue; 1250 } 1251 if ((refcount == 1) != ((l1_entry & QCOW_OFLAG_COPIED) != 0)) { 1252 fprintf(stderr, "%s OFLAG_COPIED L2 cluster: l1_index=%d " 1253 "l1_entry=%" PRIx64 " refcount=%d\n", 1254 fix & BDRV_FIX_ERRORS ? "Repairing" : 1255 "ERROR", 1256 i, l1_entry, refcount); 1257 if (fix & BDRV_FIX_ERRORS) { 1258 s->l1_table[i] = refcount == 1 1259 ? l1_entry | QCOW_OFLAG_COPIED 1260 : l1_entry & ~QCOW_OFLAG_COPIED; 1261 ret = qcow2_write_l1_entry(bs, i); 1262 if (ret < 0) { 1263 res->check_errors++; 1264 goto fail; 1265 } 1266 res->corruptions_fixed++; 1267 } else { 1268 res->corruptions++; 1269 } 1270 } 1271 1272 ret = bdrv_pread(bs->file, l2_offset, l2_table, 1273 s->l2_size * sizeof(uint64_t)); 1274 if (ret < 0) { 1275 fprintf(stderr, "ERROR: Could not read L2 table: %s\n", 1276 strerror(-ret)); 1277 res->check_errors++; 1278 goto fail; 1279 } 1280 1281 for (j = 0; j < s->l2_size; j++) { 1282 uint64_t l2_entry = be64_to_cpu(l2_table[j]); 1283 uint64_t data_offset = l2_entry & L2E_OFFSET_MASK; 1284 int cluster_type = qcow2_get_cluster_type(l2_entry); 1285 1286 if ((cluster_type == QCOW2_CLUSTER_NORMAL) || 1287 ((cluster_type == QCOW2_CLUSTER_ZERO) && (data_offset != 0))) { 1288 refcount = get_refcount(bs, data_offset >> s->cluster_bits); 1289 if (refcount < 0) { 1290 /* don't print message nor increment check_errors */ 1291 continue; 1292 } 1293 if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) { 1294 fprintf(stderr, "%s OFLAG_COPIED data cluster: " 1295 "l2_entry=%" PRIx64 " refcount=%d\n", 1296 fix & BDRV_FIX_ERRORS ? "Repairing" : 1297 "ERROR", 1298 l2_entry, refcount); 1299 if (fix & BDRV_FIX_ERRORS) { 1300 l2_table[j] = cpu_to_be64(refcount == 1 1301 ? l2_entry | QCOW_OFLAG_COPIED 1302 : l2_entry & ~QCOW_OFLAG_COPIED); 1303 l2_dirty = true; 1304 res->corruptions_fixed++; 1305 } else { 1306 res->corruptions++; 1307 } 1308 } 1309 } 1310 } 1311 1312 if (l2_dirty) { 1313 ret = qcow2_pre_write_overlap_check(bs, 1314 QCOW2_OL_DEFAULT & ~QCOW2_OL_ACTIVE_L2, l2_offset, 1315 s->cluster_size); 1316 if (ret < 0) { 1317 fprintf(stderr, "ERROR: Could not write L2 table; metadata " 1318 "overlap check failed: %s\n", strerror(-ret)); 1319 res->check_errors++; 1320 goto fail; 1321 } 1322 1323 ret = bdrv_pwrite(bs->file, l2_offset, l2_table, s->cluster_size); 1324 if (ret < 0) { 1325 fprintf(stderr, "ERROR: Could not write L2 table: %s\n", 1326 strerror(-ret)); 1327 res->check_errors++; 1328 goto fail; 1329 } 1330 } 1331 } 1332 1333 ret = 0; 1334 1335 fail: 1336 qemu_vfree(l2_table); 1337 return ret; 1338 } 1339 1340 /* 1341 * Writes one sector of the refcount table to the disk 1342 */ 1343 #define RT_ENTRIES_PER_SECTOR (512 / sizeof(uint64_t)) 1344 static int write_reftable_entry(BlockDriverState *bs, int rt_index) 1345 { 1346 BDRVQcowState *s = bs->opaque; 1347 uint64_t buf[RT_ENTRIES_PER_SECTOR]; 1348 int rt_start_index; 1349 int i, ret; 1350 1351 rt_start_index = rt_index & ~(RT_ENTRIES_PER_SECTOR - 1); 1352 for (i = 0; i < RT_ENTRIES_PER_SECTOR; i++) { 1353 buf[i] = cpu_to_be64(s->refcount_table[rt_start_index + i]); 1354 } 1355 1356 ret = qcow2_pre_write_overlap_check(bs, 1357 QCOW2_OL_DEFAULT & ~QCOW2_OL_REFCOUNT_TABLE, 1358 s->refcount_table_offset + rt_start_index * sizeof(uint64_t), 1359 sizeof(buf)); 1360 if (ret < 0) { 1361 return ret; 1362 } 1363 1364 BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_UPDATE); 1365 ret = bdrv_pwrite_sync(bs->file, s->refcount_table_offset + 1366 rt_start_index * sizeof(uint64_t), buf, sizeof(buf)); 1367 if (ret < 0) { 1368 return ret; 1369 } 1370 1371 return 0; 1372 } 1373 1374 /* 1375 * Allocates a new cluster for the given refcount block (represented by its 1376 * offset in the image file) and copies the current content there. This function 1377 * does _not_ decrement the reference count for the currently occupied cluster. 1378 * 1379 * This function prints an informative message to stderr on error (and returns 1380 * -errno); on success, 0 is returned. 1381 */ 1382 static int64_t realloc_refcount_block(BlockDriverState *bs, int reftable_index, 1383 uint64_t offset) 1384 { 1385 BDRVQcowState *s = bs->opaque; 1386 int64_t new_offset = 0; 1387 void *refcount_block = NULL; 1388 int ret; 1389 1390 /* allocate new refcount block */ 1391 new_offset = qcow2_alloc_clusters(bs, s->cluster_size); 1392 if (new_offset < 0) { 1393 fprintf(stderr, "Could not allocate new cluster: %s\n", 1394 strerror(-new_offset)); 1395 ret = new_offset; 1396 goto fail; 1397 } 1398 1399 /* fetch current refcount block content */ 1400 ret = qcow2_cache_get(bs, s->refcount_block_cache, offset, &refcount_block); 1401 if (ret < 0) { 1402 fprintf(stderr, "Could not fetch refcount block: %s\n", strerror(-ret)); 1403 goto fail; 1404 } 1405 1406 /* new block has not yet been entered into refcount table, therefore it is 1407 * no refcount block yet (regarding this check) */ 1408 ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT, new_offset, 1409 s->cluster_size); 1410 if (ret < 0) { 1411 fprintf(stderr, "Could not write refcount block; metadata overlap " 1412 "check failed: %s\n", strerror(-ret)); 1413 /* the image will be marked corrupt, so don't even attempt on freeing 1414 * the cluster */ 1415 new_offset = 0; 1416 goto fail; 1417 } 1418 1419 /* write to new block */ 1420 ret = bdrv_write(bs->file, new_offset / BDRV_SECTOR_SIZE, refcount_block, 1421 s->cluster_sectors); 1422 if (ret < 0) { 1423 fprintf(stderr, "Could not write refcount block: %s\n", strerror(-ret)); 1424 goto fail; 1425 } 1426 1427 /* update refcount table */ 1428 assert(!(new_offset & (s->cluster_size - 1))); 1429 s->refcount_table[reftable_index] = new_offset; 1430 ret = write_reftable_entry(bs, reftable_index); 1431 if (ret < 0) { 1432 fprintf(stderr, "Could not update refcount table: %s\n", 1433 strerror(-ret)); 1434 goto fail; 1435 } 1436 1437 fail: 1438 if (new_offset && (ret < 0)) { 1439 qcow2_free_clusters(bs, new_offset, s->cluster_size, 1440 QCOW2_DISCARD_ALWAYS); 1441 } 1442 if (refcount_block) { 1443 if (ret < 0) { 1444 qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block); 1445 } else { 1446 ret = qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block); 1447 } 1448 } 1449 if (ret < 0) { 1450 return ret; 1451 } 1452 return new_offset; 1453 } 1454 1455 /* 1456 * Checks an image for refcount consistency. 1457 * 1458 * Returns 0 if no errors are found, the number of errors in case the image is 1459 * detected as corrupted, and -errno when an internal error occurred. 1460 */ 1461 int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res, 1462 BdrvCheckMode fix) 1463 { 1464 BDRVQcowState *s = bs->opaque; 1465 int64_t size, i, highest_cluster; 1466 int nb_clusters, refcount1, refcount2; 1467 QCowSnapshot *sn; 1468 uint16_t *refcount_table; 1469 int ret; 1470 1471 size = bdrv_getlength(bs->file); 1472 nb_clusters = size_to_clusters(s, size); 1473 refcount_table = g_malloc0(nb_clusters * sizeof(uint16_t)); 1474 1475 res->bfi.total_clusters = 1476 size_to_clusters(s, bs->total_sectors * BDRV_SECTOR_SIZE); 1477 1478 /* header */ 1479 inc_refcounts(bs, res, refcount_table, nb_clusters, 1480 0, s->cluster_size); 1481 1482 /* current L1 table */ 1483 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1484 s->l1_table_offset, s->l1_size, 1485 CHECK_OFLAG_COPIED | CHECK_FRAG_INFO); 1486 if (ret < 0) { 1487 goto fail; 1488 } 1489 1490 /* snapshots */ 1491 for(i = 0; i < s->nb_snapshots; i++) { 1492 sn = s->snapshots + i; 1493 ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters, 1494 sn->l1_table_offset, sn->l1_size, 0); 1495 if (ret < 0) { 1496 goto fail; 1497 } 1498 } 1499 inc_refcounts(bs, res, refcount_table, nb_clusters, 1500 s->snapshots_offset, s->snapshots_size); 1501 1502 /* refcount data */ 1503 inc_refcounts(bs, res, refcount_table, nb_clusters, 1504 s->refcount_table_offset, 1505 s->refcount_table_size * sizeof(uint64_t)); 1506 1507 for(i = 0; i < s->refcount_table_size; i++) { 1508 uint64_t offset, cluster; 1509 offset = s->refcount_table[i]; 1510 cluster = offset >> s->cluster_bits; 1511 1512 /* Refcount blocks are cluster aligned */ 1513 if (offset & (s->cluster_size - 1)) { 1514 fprintf(stderr, "ERROR refcount block %" PRId64 " is not " 1515 "cluster aligned; refcount table entry corrupted\n", i); 1516 res->corruptions++; 1517 continue; 1518 } 1519 1520 if (cluster >= nb_clusters) { 1521 fprintf(stderr, "ERROR refcount block %" PRId64 1522 " is outside image\n", i); 1523 res->corruptions++; 1524 continue; 1525 } 1526 1527 if (offset != 0) { 1528 inc_refcounts(bs, res, refcount_table, nb_clusters, 1529 offset, s->cluster_size); 1530 if (refcount_table[cluster] != 1) { 1531 fprintf(stderr, "%s refcount block %" PRId64 1532 " refcount=%d\n", 1533 fix & BDRV_FIX_ERRORS ? "Repairing" : 1534 "ERROR", 1535 i, refcount_table[cluster]); 1536 1537 if (fix & BDRV_FIX_ERRORS) { 1538 int64_t new_offset; 1539 1540 new_offset = realloc_refcount_block(bs, i, offset); 1541 if (new_offset < 0) { 1542 res->corruptions++; 1543 continue; 1544 } 1545 1546 /* update refcounts */ 1547 if ((new_offset >> s->cluster_bits) >= nb_clusters) { 1548 /* increase refcount_table size if necessary */ 1549 int old_nb_clusters = nb_clusters; 1550 nb_clusters = (new_offset >> s->cluster_bits) + 1; 1551 refcount_table = g_realloc(refcount_table, 1552 nb_clusters * sizeof(uint16_t)); 1553 memset(&refcount_table[old_nb_clusters], 0, (nb_clusters 1554 - old_nb_clusters) * sizeof(uint16_t)); 1555 } 1556 refcount_table[cluster]--; 1557 inc_refcounts(bs, res, refcount_table, nb_clusters, 1558 new_offset, s->cluster_size); 1559 1560 res->corruptions_fixed++; 1561 } else { 1562 res->corruptions++; 1563 } 1564 } 1565 } 1566 } 1567 1568 /* compare ref counts */ 1569 for (i = 0, highest_cluster = 0; i < nb_clusters; i++) { 1570 refcount1 = get_refcount(bs, i); 1571 if (refcount1 < 0) { 1572 fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n", 1573 i, strerror(-refcount1)); 1574 res->check_errors++; 1575 continue; 1576 } 1577 1578 refcount2 = refcount_table[i]; 1579 1580 if (refcount1 > 0 || refcount2 > 0) { 1581 highest_cluster = i; 1582 } 1583 1584 if (refcount1 != refcount2) { 1585 1586 /* Check if we're allowed to fix the mismatch */ 1587 int *num_fixed = NULL; 1588 if (refcount1 > refcount2 && (fix & BDRV_FIX_LEAKS)) { 1589 num_fixed = &res->leaks_fixed; 1590 } else if (refcount1 < refcount2 && (fix & BDRV_FIX_ERRORS)) { 1591 num_fixed = &res->corruptions_fixed; 1592 } 1593 1594 fprintf(stderr, "%s cluster %" PRId64 " refcount=%d reference=%d\n", 1595 num_fixed != NULL ? "Repairing" : 1596 refcount1 < refcount2 ? "ERROR" : 1597 "Leaked", 1598 i, refcount1, refcount2); 1599 1600 if (num_fixed) { 1601 ret = update_refcount(bs, i << s->cluster_bits, 1, 1602 refcount2 - refcount1, 1603 QCOW2_DISCARD_ALWAYS); 1604 if (ret >= 0) { 1605 (*num_fixed)++; 1606 continue; 1607 } 1608 } 1609 1610 /* And if we couldn't, print an error */ 1611 if (refcount1 < refcount2) { 1612 res->corruptions++; 1613 } else { 1614 res->leaks++; 1615 } 1616 } 1617 } 1618 1619 /* check OFLAG_COPIED */ 1620 ret = check_oflag_copied(bs, res, fix); 1621 if (ret < 0) { 1622 goto fail; 1623 } 1624 1625 res->image_end_offset = (highest_cluster + 1) * s->cluster_size; 1626 ret = 0; 1627 1628 fail: 1629 g_free(refcount_table); 1630 1631 return ret; 1632 } 1633 1634 #define overlaps_with(ofs, sz) \ 1635 ranges_overlap(offset, size, ofs, sz) 1636 1637 /* 1638 * Checks if the given offset into the image file is actually free to use by 1639 * looking for overlaps with important metadata sections (L1/L2 tables etc.), 1640 * i.e. a sanity check without relying on the refcount tables. 1641 * 1642 * The chk parameter specifies exactly what checks to perform (being a bitmask 1643 * of QCow2MetadataOverlap values). 1644 * 1645 * Returns: 1646 * - 0 if writing to this offset will not affect the mentioned metadata 1647 * - a positive QCow2MetadataOverlap value indicating one overlapping section 1648 * - a negative value (-errno) indicating an error while performing a check, 1649 * e.g. when bdrv_read failed on QCOW2_OL_INACTIVE_L2 1650 */ 1651 int qcow2_check_metadata_overlap(BlockDriverState *bs, int chk, int64_t offset, 1652 int64_t size) 1653 { 1654 BDRVQcowState *s = bs->opaque; 1655 int i, j; 1656 1657 if (!size) { 1658 return 0; 1659 } 1660 1661 if (chk & QCOW2_OL_MAIN_HEADER) { 1662 if (offset < s->cluster_size) { 1663 return QCOW2_OL_MAIN_HEADER; 1664 } 1665 } 1666 1667 /* align range to test to cluster boundaries */ 1668 size = align_offset(offset_into_cluster(s, offset) + size, s->cluster_size); 1669 offset = start_of_cluster(s, offset); 1670 1671 if ((chk & QCOW2_OL_ACTIVE_L1) && s->l1_size) { 1672 if (overlaps_with(s->l1_table_offset, s->l1_size * sizeof(uint64_t))) { 1673 return QCOW2_OL_ACTIVE_L1; 1674 } 1675 } 1676 1677 if ((chk & QCOW2_OL_REFCOUNT_TABLE) && s->refcount_table_size) { 1678 if (overlaps_with(s->refcount_table_offset, 1679 s->refcount_table_size * sizeof(uint64_t))) { 1680 return QCOW2_OL_REFCOUNT_TABLE; 1681 } 1682 } 1683 1684 if ((chk & QCOW2_OL_SNAPSHOT_TABLE) && s->snapshots_size) { 1685 if (overlaps_with(s->snapshots_offset, s->snapshots_size)) { 1686 return QCOW2_OL_SNAPSHOT_TABLE; 1687 } 1688 } 1689 1690 if ((chk & QCOW2_OL_INACTIVE_L1) && s->snapshots) { 1691 for (i = 0; i < s->nb_snapshots; i++) { 1692 if (s->snapshots[i].l1_size && 1693 overlaps_with(s->snapshots[i].l1_table_offset, 1694 s->snapshots[i].l1_size * sizeof(uint64_t))) { 1695 return QCOW2_OL_INACTIVE_L1; 1696 } 1697 } 1698 } 1699 1700 if ((chk & QCOW2_OL_ACTIVE_L2) && s->l1_table) { 1701 for (i = 0; i < s->l1_size; i++) { 1702 if ((s->l1_table[i] & L1E_OFFSET_MASK) && 1703 overlaps_with(s->l1_table[i] & L1E_OFFSET_MASK, 1704 s->cluster_size)) { 1705 return QCOW2_OL_ACTIVE_L2; 1706 } 1707 } 1708 } 1709 1710 if ((chk & QCOW2_OL_REFCOUNT_BLOCK) && s->refcount_table) { 1711 for (i = 0; i < s->refcount_table_size; i++) { 1712 if ((s->refcount_table[i] & REFT_OFFSET_MASK) && 1713 overlaps_with(s->refcount_table[i] & REFT_OFFSET_MASK, 1714 s->cluster_size)) { 1715 return QCOW2_OL_REFCOUNT_BLOCK; 1716 } 1717 } 1718 } 1719 1720 if ((chk & QCOW2_OL_INACTIVE_L2) && s->snapshots) { 1721 for (i = 0; i < s->nb_snapshots; i++) { 1722 uint64_t l1_ofs = s->snapshots[i].l1_table_offset; 1723 uint32_t l1_sz = s->snapshots[i].l1_size; 1724 uint64_t *l1 = g_malloc(l1_sz * sizeof(uint64_t)); 1725 int ret; 1726 1727 ret = bdrv_read(bs->file, l1_ofs / BDRV_SECTOR_SIZE, (uint8_t *)l1, 1728 l1_sz * sizeof(uint64_t) / BDRV_SECTOR_SIZE); 1729 1730 if (ret < 0) { 1731 g_free(l1); 1732 return ret; 1733 } 1734 1735 for (j = 0; j < l1_sz; j++) { 1736 if ((l1[j] & L1E_OFFSET_MASK) && 1737 overlaps_with(l1[j] & L1E_OFFSET_MASK, s->cluster_size)) { 1738 g_free(l1); 1739 return QCOW2_OL_INACTIVE_L2; 1740 } 1741 } 1742 1743 g_free(l1); 1744 } 1745 } 1746 1747 return 0; 1748 } 1749 1750 static const char *metadata_ol_names[] = { 1751 [QCOW2_OL_MAIN_HEADER_BITNR] = "qcow2_header", 1752 [QCOW2_OL_ACTIVE_L1_BITNR] = "active L1 table", 1753 [QCOW2_OL_ACTIVE_L2_BITNR] = "active L2 table", 1754 [QCOW2_OL_REFCOUNT_TABLE_BITNR] = "refcount table", 1755 [QCOW2_OL_REFCOUNT_BLOCK_BITNR] = "refcount block", 1756 [QCOW2_OL_SNAPSHOT_TABLE_BITNR] = "snapshot table", 1757 [QCOW2_OL_INACTIVE_L1_BITNR] = "inactive L1 table", 1758 [QCOW2_OL_INACTIVE_L2_BITNR] = "inactive L2 table", 1759 }; 1760 1761 /* 1762 * First performs a check for metadata overlaps (through 1763 * qcow2_check_metadata_overlap); if that fails with a negative value (error 1764 * while performing a check), that value is returned. If an impending overlap 1765 * is detected, the BDS will be made unusable, the qcow2 file marked corrupt 1766 * and -EIO returned. 1767 * 1768 * Returns 0 if there were neither overlaps nor errors while checking for 1769 * overlaps; or a negative value (-errno) on error. 1770 */ 1771 int qcow2_pre_write_overlap_check(BlockDriverState *bs, int chk, int64_t offset, 1772 int64_t size) 1773 { 1774 int ret = qcow2_check_metadata_overlap(bs, chk, offset, size); 1775 1776 if (ret < 0) { 1777 return ret; 1778 } else if (ret > 0) { 1779 int metadata_ol_bitnr = ffs(ret) - 1; 1780 char *message; 1781 QObject *data; 1782 1783 assert(metadata_ol_bitnr < QCOW2_OL_MAX_BITNR); 1784 1785 fprintf(stderr, "qcow2: Preventing invalid write on metadata (overlaps " 1786 "with %s); image marked as corrupt.\n", 1787 metadata_ol_names[metadata_ol_bitnr]); 1788 message = g_strdup_printf("Prevented %s overwrite", 1789 metadata_ol_names[metadata_ol_bitnr]); 1790 data = qobject_from_jsonf("{ 'device': %s, 'msg': %s, 'offset': %" 1791 PRId64 ", 'size': %" PRId64 " }", bs->device_name, message, 1792 offset, size); 1793 monitor_protocol_event(QEVENT_BLOCK_IMAGE_CORRUPTED, data); 1794 g_free(message); 1795 qobject_decref(data); 1796 1797 qcow2_mark_corrupt(bs); 1798 bs->drv = NULL; /* make BDS unusable */ 1799 return -EIO; 1800 } 1801 1802 return 0; 1803 } 1804