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/osdep.h" 26 #include <zlib.h> 27 28 #include "qapi/error.h" 29 #include "qemu-common.h" 30 #include "block/block_int.h" 31 #include "qcow2.h" 32 #include "qemu/bswap.h" 33 #include "trace.h" 34 35 int qcow2_shrink_l1_table(BlockDriverState *bs, uint64_t exact_size) 36 { 37 BDRVQcow2State *s = bs->opaque; 38 int new_l1_size, i, ret; 39 40 if (exact_size >= s->l1_size) { 41 return 0; 42 } 43 44 new_l1_size = exact_size; 45 46 #ifdef DEBUG_ALLOC2 47 fprintf(stderr, "shrink l1_table from %d to %d\n", s->l1_size, new_l1_size); 48 #endif 49 50 BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_WRITE_TABLE); 51 ret = bdrv_pwrite_zeroes(bs->file, s->l1_table_offset + 52 new_l1_size * sizeof(uint64_t), 53 (s->l1_size - new_l1_size) * sizeof(uint64_t), 0); 54 if (ret < 0) { 55 goto fail; 56 } 57 58 ret = bdrv_flush(bs->file->bs); 59 if (ret < 0) { 60 goto fail; 61 } 62 63 BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_FREE_L2_CLUSTERS); 64 for (i = s->l1_size - 1; i > new_l1_size - 1; i--) { 65 if ((s->l1_table[i] & L1E_OFFSET_MASK) == 0) { 66 continue; 67 } 68 qcow2_free_clusters(bs, s->l1_table[i] & L1E_OFFSET_MASK, 69 s->cluster_size, QCOW2_DISCARD_ALWAYS); 70 s->l1_table[i] = 0; 71 } 72 return 0; 73 74 fail: 75 /* 76 * If the write in the l1_table failed the image may contain a partially 77 * overwritten l1_table. In this case it would be better to clear the 78 * l1_table in memory to avoid possible image corruption. 79 */ 80 memset(s->l1_table + new_l1_size, 0, 81 (s->l1_size - new_l1_size) * sizeof(uint64_t)); 82 return ret; 83 } 84 85 int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, 86 bool exact_size) 87 { 88 BDRVQcow2State *s = bs->opaque; 89 int new_l1_size2, ret, i; 90 uint64_t *new_l1_table; 91 int64_t old_l1_table_offset, old_l1_size; 92 int64_t new_l1_table_offset, new_l1_size; 93 uint8_t data[12]; 94 95 if (min_size <= s->l1_size) 96 return 0; 97 98 /* Do a sanity check on min_size before trying to calculate new_l1_size 99 * (this prevents overflows during the while loop for the calculation of 100 * new_l1_size) */ 101 if (min_size > INT_MAX / sizeof(uint64_t)) { 102 return -EFBIG; 103 } 104 105 if (exact_size) { 106 new_l1_size = min_size; 107 } else { 108 /* Bump size up to reduce the number of times we have to grow */ 109 new_l1_size = s->l1_size; 110 if (new_l1_size == 0) { 111 new_l1_size = 1; 112 } 113 while (min_size > new_l1_size) { 114 new_l1_size = DIV_ROUND_UP(new_l1_size * 3, 2); 115 } 116 } 117 118 QEMU_BUILD_BUG_ON(QCOW_MAX_L1_SIZE > INT_MAX); 119 if (new_l1_size > QCOW_MAX_L1_SIZE / sizeof(uint64_t)) { 120 return -EFBIG; 121 } 122 123 #ifdef DEBUG_ALLOC2 124 fprintf(stderr, "grow l1_table from %d to %" PRId64 "\n", 125 s->l1_size, new_l1_size); 126 #endif 127 128 new_l1_size2 = sizeof(uint64_t) * new_l1_size; 129 new_l1_table = qemu_try_blockalign(bs->file->bs, 130 ROUND_UP(new_l1_size2, 512)); 131 if (new_l1_table == NULL) { 132 return -ENOMEM; 133 } 134 memset(new_l1_table, 0, ROUND_UP(new_l1_size2, 512)); 135 136 if (s->l1_size) { 137 memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t)); 138 } 139 140 /* write new table (align to cluster) */ 141 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ALLOC_TABLE); 142 new_l1_table_offset = qcow2_alloc_clusters(bs, new_l1_size2); 143 if (new_l1_table_offset < 0) { 144 qemu_vfree(new_l1_table); 145 return new_l1_table_offset; 146 } 147 148 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 149 if (ret < 0) { 150 goto fail; 151 } 152 153 /* the L1 position has not yet been updated, so these clusters must 154 * indeed be completely free */ 155 ret = qcow2_pre_write_overlap_check(bs, 0, new_l1_table_offset, 156 new_l1_size2); 157 if (ret < 0) { 158 goto fail; 159 } 160 161 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_WRITE_TABLE); 162 for(i = 0; i < s->l1_size; i++) 163 new_l1_table[i] = cpu_to_be64(new_l1_table[i]); 164 ret = bdrv_pwrite_sync(bs->file, new_l1_table_offset, 165 new_l1_table, new_l1_size2); 166 if (ret < 0) 167 goto fail; 168 for(i = 0; i < s->l1_size; i++) 169 new_l1_table[i] = be64_to_cpu(new_l1_table[i]); 170 171 /* set new table */ 172 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ACTIVATE_TABLE); 173 stl_be_p(data, new_l1_size); 174 stq_be_p(data + 4, new_l1_table_offset); 175 ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size), 176 data, sizeof(data)); 177 if (ret < 0) { 178 goto fail; 179 } 180 qemu_vfree(s->l1_table); 181 old_l1_table_offset = s->l1_table_offset; 182 s->l1_table_offset = new_l1_table_offset; 183 s->l1_table = new_l1_table; 184 old_l1_size = s->l1_size; 185 s->l1_size = new_l1_size; 186 qcow2_free_clusters(bs, old_l1_table_offset, old_l1_size * sizeof(uint64_t), 187 QCOW2_DISCARD_OTHER); 188 return 0; 189 fail: 190 qemu_vfree(new_l1_table); 191 qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2, 192 QCOW2_DISCARD_OTHER); 193 return ret; 194 } 195 196 /* 197 * l2_load 198 * 199 * @bs: The BlockDriverState 200 * @offset: A guest offset, used to calculate what slice of the L2 201 * table to load. 202 * @l2_offset: Offset to the L2 table in the image file. 203 * @l2_slice: Location to store the pointer to the L2 slice. 204 * 205 * Loads a L2 slice into memory (L2 slices are the parts of L2 tables 206 * that are loaded by the qcow2 cache). If the slice is in the cache, 207 * the cache is used; otherwise the L2 slice is loaded from the image 208 * file. 209 */ 210 static int l2_load(BlockDriverState *bs, uint64_t offset, 211 uint64_t l2_offset, uint64_t **l2_slice) 212 { 213 BDRVQcow2State *s = bs->opaque; 214 int start_of_slice = sizeof(uint64_t) * 215 (offset_to_l2_index(s, offset) - offset_to_l2_slice_index(s, offset)); 216 217 return qcow2_cache_get(bs, s->l2_table_cache, l2_offset + start_of_slice, 218 (void **)l2_slice); 219 } 220 221 /* 222 * Writes one sector of the L1 table to the disk (can't update single entries 223 * and we really don't want bdrv_pread to perform a read-modify-write) 224 */ 225 #define L1_ENTRIES_PER_SECTOR (512 / 8) 226 int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index) 227 { 228 BDRVQcow2State *s = bs->opaque; 229 uint64_t buf[L1_ENTRIES_PER_SECTOR] = { 0 }; 230 int l1_start_index; 231 int i, ret; 232 233 l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1); 234 for (i = 0; i < L1_ENTRIES_PER_SECTOR && l1_start_index + i < s->l1_size; 235 i++) 236 { 237 buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]); 238 } 239 240 ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1, 241 s->l1_table_offset + 8 * l1_start_index, sizeof(buf)); 242 if (ret < 0) { 243 return ret; 244 } 245 246 BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE); 247 ret = bdrv_pwrite_sync(bs->file, 248 s->l1_table_offset + 8 * l1_start_index, 249 buf, sizeof(buf)); 250 if (ret < 0) { 251 return ret; 252 } 253 254 return 0; 255 } 256 257 /* 258 * l2_allocate 259 * 260 * Allocate a new l2 entry in the file. If l1_index points to an already 261 * used entry in the L2 table (i.e. we are doing a copy on write for the L2 262 * table) copy the contents of the old L2 table into the newly allocated one. 263 * Otherwise the new table is initialized with zeros. 264 * 265 */ 266 267 static int l2_allocate(BlockDriverState *bs, int l1_index) 268 { 269 BDRVQcow2State *s = bs->opaque; 270 uint64_t old_l2_offset; 271 uint64_t *l2_slice = NULL; 272 unsigned slice, slice_size2, n_slices; 273 int64_t l2_offset; 274 int ret; 275 276 old_l2_offset = s->l1_table[l1_index]; 277 278 trace_qcow2_l2_allocate(bs, l1_index); 279 280 /* allocate a new l2 entry */ 281 282 l2_offset = qcow2_alloc_clusters(bs, s->l2_size * sizeof(uint64_t)); 283 if (l2_offset < 0) { 284 ret = l2_offset; 285 goto fail; 286 } 287 288 /* If we're allocating the table at offset 0 then something is wrong */ 289 if (l2_offset == 0) { 290 qcow2_signal_corruption(bs, true, -1, -1, "Preventing invalid " 291 "allocation of L2 table at offset 0"); 292 ret = -EIO; 293 goto fail; 294 } 295 296 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 297 if (ret < 0) { 298 goto fail; 299 } 300 301 /* allocate a new entry in the l2 cache */ 302 303 slice_size2 = s->l2_slice_size * sizeof(uint64_t); 304 n_slices = s->cluster_size / slice_size2; 305 306 trace_qcow2_l2_allocate_get_empty(bs, l1_index); 307 for (slice = 0; slice < n_slices; slice++) { 308 ret = qcow2_cache_get_empty(bs, s->l2_table_cache, 309 l2_offset + slice * slice_size2, 310 (void **) &l2_slice); 311 if (ret < 0) { 312 goto fail; 313 } 314 315 if ((old_l2_offset & L1E_OFFSET_MASK) == 0) { 316 /* if there was no old l2 table, clear the new slice */ 317 memset(l2_slice, 0, slice_size2); 318 } else { 319 uint64_t *old_slice; 320 uint64_t old_l2_slice_offset = 321 (old_l2_offset & L1E_OFFSET_MASK) + slice * slice_size2; 322 323 /* if there was an old l2 table, read a slice from the disk */ 324 BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ); 325 ret = qcow2_cache_get(bs, s->l2_table_cache, old_l2_slice_offset, 326 (void **) &old_slice); 327 if (ret < 0) { 328 goto fail; 329 } 330 331 memcpy(l2_slice, old_slice, slice_size2); 332 333 qcow2_cache_put(s->l2_table_cache, (void **) &old_slice); 334 } 335 336 /* write the l2 slice to the file */ 337 BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_WRITE); 338 339 trace_qcow2_l2_allocate_write_l2(bs, l1_index); 340 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 341 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 342 } 343 344 ret = qcow2_cache_flush(bs, s->l2_table_cache); 345 if (ret < 0) { 346 goto fail; 347 } 348 349 /* update the L1 entry */ 350 trace_qcow2_l2_allocate_write_l1(bs, l1_index); 351 s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED; 352 ret = qcow2_write_l1_entry(bs, l1_index); 353 if (ret < 0) { 354 goto fail; 355 } 356 357 trace_qcow2_l2_allocate_done(bs, l1_index, 0); 358 return 0; 359 360 fail: 361 trace_qcow2_l2_allocate_done(bs, l1_index, ret); 362 if (l2_slice != NULL) { 363 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 364 } 365 s->l1_table[l1_index] = old_l2_offset; 366 if (l2_offset > 0) { 367 qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), 368 QCOW2_DISCARD_ALWAYS); 369 } 370 return ret; 371 } 372 373 /* 374 * Checks how many clusters in a given L2 slice are contiguous in the image 375 * file. As soon as one of the flags in the bitmask stop_flags changes compared 376 * to the first cluster, the search is stopped and the cluster is not counted 377 * as contiguous. (This allows it, for example, to stop at the first compressed 378 * cluster which may require a different handling) 379 */ 380 static int count_contiguous_clusters(int nb_clusters, int cluster_size, 381 uint64_t *l2_slice, uint64_t stop_flags) 382 { 383 int i; 384 QCow2ClusterType first_cluster_type; 385 uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED; 386 uint64_t first_entry = be64_to_cpu(l2_slice[0]); 387 uint64_t offset = first_entry & mask; 388 389 if (!offset) { 390 return 0; 391 } 392 393 /* must be allocated */ 394 first_cluster_type = qcow2_get_cluster_type(first_entry); 395 assert(first_cluster_type == QCOW2_CLUSTER_NORMAL || 396 first_cluster_type == QCOW2_CLUSTER_ZERO_ALLOC); 397 398 for (i = 0; i < nb_clusters; i++) { 399 uint64_t l2_entry = be64_to_cpu(l2_slice[i]) & mask; 400 if (offset + (uint64_t) i * cluster_size != l2_entry) { 401 break; 402 } 403 } 404 405 return i; 406 } 407 408 /* 409 * Checks how many consecutive unallocated clusters in a given L2 410 * slice have the same cluster type. 411 */ 412 static int count_contiguous_clusters_unallocated(int nb_clusters, 413 uint64_t *l2_slice, 414 QCow2ClusterType wanted_type) 415 { 416 int i; 417 418 assert(wanted_type == QCOW2_CLUSTER_ZERO_PLAIN || 419 wanted_type == QCOW2_CLUSTER_UNALLOCATED); 420 for (i = 0; i < nb_clusters; i++) { 421 uint64_t entry = be64_to_cpu(l2_slice[i]); 422 QCow2ClusterType type = qcow2_get_cluster_type(entry); 423 424 if (type != wanted_type) { 425 break; 426 } 427 } 428 429 return i; 430 } 431 432 static int coroutine_fn do_perform_cow_read(BlockDriverState *bs, 433 uint64_t src_cluster_offset, 434 unsigned offset_in_cluster, 435 QEMUIOVector *qiov) 436 { 437 int ret; 438 439 if (qiov->size == 0) { 440 return 0; 441 } 442 443 BLKDBG_EVENT(bs->file, BLKDBG_COW_READ); 444 445 if (!bs->drv) { 446 return -ENOMEDIUM; 447 } 448 449 /* Call .bdrv_co_readv() directly instead of using the public block-layer 450 * interface. This avoids double I/O throttling and request tracking, 451 * which can lead to deadlock when block layer copy-on-read is enabled. 452 */ 453 ret = bs->drv->bdrv_co_preadv(bs, src_cluster_offset + offset_in_cluster, 454 qiov->size, qiov, 0); 455 if (ret < 0) { 456 return ret; 457 } 458 459 return 0; 460 } 461 462 static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs, 463 uint64_t src_cluster_offset, 464 uint64_t cluster_offset, 465 unsigned offset_in_cluster, 466 uint8_t *buffer, 467 unsigned bytes) 468 { 469 if (bytes && bs->encrypted) { 470 BDRVQcow2State *s = bs->opaque; 471 int64_t offset = (s->crypt_physical_offset ? 472 (cluster_offset + offset_in_cluster) : 473 (src_cluster_offset + offset_in_cluster)); 474 assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0); 475 assert((bytes & ~BDRV_SECTOR_MASK) == 0); 476 assert(s->crypto); 477 if (qcrypto_block_encrypt(s->crypto, offset, buffer, bytes, NULL) < 0) { 478 return false; 479 } 480 } 481 return true; 482 } 483 484 static int coroutine_fn do_perform_cow_write(BlockDriverState *bs, 485 uint64_t cluster_offset, 486 unsigned offset_in_cluster, 487 QEMUIOVector *qiov) 488 { 489 int ret; 490 491 if (qiov->size == 0) { 492 return 0; 493 } 494 495 ret = qcow2_pre_write_overlap_check(bs, 0, 496 cluster_offset + offset_in_cluster, qiov->size); 497 if (ret < 0) { 498 return ret; 499 } 500 501 BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE); 502 ret = bdrv_co_pwritev(bs->file, cluster_offset + offset_in_cluster, 503 qiov->size, qiov, 0); 504 if (ret < 0) { 505 return ret; 506 } 507 508 return 0; 509 } 510 511 512 /* 513 * get_cluster_offset 514 * 515 * For a given offset of the virtual disk, find the cluster type and offset in 516 * the qcow2 file. The offset is stored in *cluster_offset. 517 * 518 * On entry, *bytes is the maximum number of contiguous bytes starting at 519 * offset that we are interested in. 520 * 521 * On exit, *bytes is the number of bytes starting at offset that have the same 522 * cluster type and (if applicable) are stored contiguously in the image file. 523 * Compressed clusters are always returned one by one. 524 * 525 * Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error 526 * cases. 527 */ 528 int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset, 529 unsigned int *bytes, uint64_t *cluster_offset) 530 { 531 BDRVQcow2State *s = bs->opaque; 532 unsigned int l2_index; 533 uint64_t l1_index, l2_offset, *l2_slice; 534 int c; 535 unsigned int offset_in_cluster; 536 uint64_t bytes_available, bytes_needed, nb_clusters; 537 QCow2ClusterType type; 538 int ret; 539 540 offset_in_cluster = offset_into_cluster(s, offset); 541 bytes_needed = (uint64_t) *bytes + offset_in_cluster; 542 543 /* compute how many bytes there are between the start of the cluster 544 * containing offset and the end of the l2 slice that contains 545 * the entry pointing to it */ 546 bytes_available = 547 ((uint64_t) (s->l2_slice_size - offset_to_l2_slice_index(s, offset))) 548 << s->cluster_bits; 549 550 if (bytes_needed > bytes_available) { 551 bytes_needed = bytes_available; 552 } 553 554 *cluster_offset = 0; 555 556 /* seek to the l2 offset in the l1 table */ 557 558 l1_index = offset_to_l1_index(s, offset); 559 if (l1_index >= s->l1_size) { 560 type = QCOW2_CLUSTER_UNALLOCATED; 561 goto out; 562 } 563 564 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 565 if (!l2_offset) { 566 type = QCOW2_CLUSTER_UNALLOCATED; 567 goto out; 568 } 569 570 if (offset_into_cluster(s, l2_offset)) { 571 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 572 " unaligned (L1 index: %#" PRIx64 ")", 573 l2_offset, l1_index); 574 return -EIO; 575 } 576 577 /* load the l2 slice in memory */ 578 579 ret = l2_load(bs, offset, l2_offset, &l2_slice); 580 if (ret < 0) { 581 return ret; 582 } 583 584 /* find the cluster offset for the given disk offset */ 585 586 l2_index = offset_to_l2_slice_index(s, offset); 587 *cluster_offset = be64_to_cpu(l2_slice[l2_index]); 588 589 nb_clusters = size_to_clusters(s, bytes_needed); 590 /* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned 591 * integers; the minimum cluster size is 512, so this assertion is always 592 * true */ 593 assert(nb_clusters <= INT_MAX); 594 595 type = qcow2_get_cluster_type(*cluster_offset); 596 if (s->qcow_version < 3 && (type == QCOW2_CLUSTER_ZERO_PLAIN || 597 type == QCOW2_CLUSTER_ZERO_ALLOC)) { 598 qcow2_signal_corruption(bs, true, -1, -1, "Zero cluster entry found" 599 " in pre-v3 image (L2 offset: %#" PRIx64 600 ", L2 index: %#x)", l2_offset, l2_index); 601 ret = -EIO; 602 goto fail; 603 } 604 switch (type) { 605 case QCOW2_CLUSTER_COMPRESSED: 606 /* Compressed clusters can only be processed one by one */ 607 c = 1; 608 *cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK; 609 break; 610 case QCOW2_CLUSTER_ZERO_PLAIN: 611 case QCOW2_CLUSTER_UNALLOCATED: 612 /* how many empty clusters ? */ 613 c = count_contiguous_clusters_unallocated(nb_clusters, 614 &l2_slice[l2_index], type); 615 *cluster_offset = 0; 616 break; 617 case QCOW2_CLUSTER_ZERO_ALLOC: 618 case QCOW2_CLUSTER_NORMAL: 619 /* how many allocated clusters ? */ 620 c = count_contiguous_clusters(nb_clusters, s->cluster_size, 621 &l2_slice[l2_index], QCOW_OFLAG_ZERO); 622 *cluster_offset &= L2E_OFFSET_MASK; 623 if (offset_into_cluster(s, *cluster_offset)) { 624 qcow2_signal_corruption(bs, true, -1, -1, 625 "Cluster allocation offset %#" 626 PRIx64 " unaligned (L2 offset: %#" PRIx64 627 ", L2 index: %#x)", *cluster_offset, 628 l2_offset, l2_index); 629 ret = -EIO; 630 goto fail; 631 } 632 break; 633 default: 634 abort(); 635 } 636 637 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 638 639 bytes_available = (int64_t)c * s->cluster_size; 640 641 out: 642 if (bytes_available > bytes_needed) { 643 bytes_available = bytes_needed; 644 } 645 646 /* bytes_available <= bytes_needed <= *bytes + offset_in_cluster; 647 * subtracting offset_in_cluster will therefore definitely yield something 648 * not exceeding UINT_MAX */ 649 assert(bytes_available - offset_in_cluster <= UINT_MAX); 650 *bytes = bytes_available - offset_in_cluster; 651 652 return type; 653 654 fail: 655 qcow2_cache_put(s->l2_table_cache, (void **)&l2_slice); 656 return ret; 657 } 658 659 /* 660 * get_cluster_table 661 * 662 * for a given disk offset, load (and allocate if needed) 663 * the appropriate slice of its l2 table. 664 * 665 * the cluster index in the l2 slice is given to the caller. 666 * 667 * Returns 0 on success, -errno in failure case 668 */ 669 static int get_cluster_table(BlockDriverState *bs, uint64_t offset, 670 uint64_t **new_l2_slice, 671 int *new_l2_index) 672 { 673 BDRVQcow2State *s = bs->opaque; 674 unsigned int l2_index; 675 uint64_t l1_index, l2_offset; 676 uint64_t *l2_slice = NULL; 677 int ret; 678 679 /* seek to the l2 offset in the l1 table */ 680 681 l1_index = offset_to_l1_index(s, offset); 682 if (l1_index >= s->l1_size) { 683 ret = qcow2_grow_l1_table(bs, l1_index + 1, false); 684 if (ret < 0) { 685 return ret; 686 } 687 } 688 689 assert(l1_index < s->l1_size); 690 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 691 if (offset_into_cluster(s, l2_offset)) { 692 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 693 " unaligned (L1 index: %#" PRIx64 ")", 694 l2_offset, l1_index); 695 return -EIO; 696 } 697 698 if (!(s->l1_table[l1_index] & QCOW_OFLAG_COPIED)) { 699 /* First allocate a new L2 table (and do COW if needed) */ 700 ret = l2_allocate(bs, l1_index); 701 if (ret < 0) { 702 return ret; 703 } 704 705 /* Then decrease the refcount of the old table */ 706 if (l2_offset) { 707 qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), 708 QCOW2_DISCARD_OTHER); 709 } 710 711 /* Get the offset of the newly-allocated l2 table */ 712 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 713 assert(offset_into_cluster(s, l2_offset) == 0); 714 } 715 716 /* load the l2 slice in memory */ 717 ret = l2_load(bs, offset, l2_offset, &l2_slice); 718 if (ret < 0) { 719 return ret; 720 } 721 722 /* find the cluster offset for the given disk offset */ 723 724 l2_index = offset_to_l2_slice_index(s, offset); 725 726 *new_l2_slice = l2_slice; 727 *new_l2_index = l2_index; 728 729 return 0; 730 } 731 732 /* 733 * alloc_compressed_cluster_offset 734 * 735 * For a given offset of the disk image, return cluster offset in 736 * qcow2 file. 737 * 738 * If the offset is not found, allocate a new compressed cluster. 739 * 740 * Return the cluster offset if successful, 741 * Return 0, otherwise. 742 * 743 */ 744 745 uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, 746 uint64_t offset, 747 int compressed_size) 748 { 749 BDRVQcow2State *s = bs->opaque; 750 int l2_index, ret; 751 uint64_t *l2_slice; 752 int64_t cluster_offset; 753 int nb_csectors; 754 755 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 756 if (ret < 0) { 757 return 0; 758 } 759 760 /* Compression can't overwrite anything. Fail if the cluster was already 761 * allocated. */ 762 cluster_offset = be64_to_cpu(l2_slice[l2_index]); 763 if (cluster_offset & L2E_OFFSET_MASK) { 764 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 765 return 0; 766 } 767 768 cluster_offset = qcow2_alloc_bytes(bs, compressed_size); 769 if (cluster_offset < 0) { 770 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 771 return 0; 772 } 773 774 nb_csectors = ((cluster_offset + compressed_size - 1) >> 9) - 775 (cluster_offset >> 9); 776 777 cluster_offset |= QCOW_OFLAG_COMPRESSED | 778 ((uint64_t)nb_csectors << s->csize_shift); 779 780 /* update L2 table */ 781 782 /* compressed clusters never have the copied flag */ 783 784 BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED); 785 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 786 l2_slice[l2_index] = cpu_to_be64(cluster_offset); 787 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 788 789 return cluster_offset; 790 } 791 792 static int perform_cow(BlockDriverState *bs, QCowL2Meta *m) 793 { 794 BDRVQcow2State *s = bs->opaque; 795 Qcow2COWRegion *start = &m->cow_start; 796 Qcow2COWRegion *end = &m->cow_end; 797 unsigned buffer_size; 798 unsigned data_bytes = end->offset - (start->offset + start->nb_bytes); 799 bool merge_reads; 800 uint8_t *start_buffer, *end_buffer; 801 QEMUIOVector qiov; 802 int ret; 803 804 assert(start->nb_bytes <= UINT_MAX - end->nb_bytes); 805 assert(start->nb_bytes + end->nb_bytes <= UINT_MAX - data_bytes); 806 assert(start->offset + start->nb_bytes <= end->offset); 807 assert(!m->data_qiov || m->data_qiov->size == data_bytes); 808 809 if (start->nb_bytes == 0 && end->nb_bytes == 0) { 810 return 0; 811 } 812 813 /* If we have to read both the start and end COW regions and the 814 * middle region is not too large then perform just one read 815 * operation */ 816 merge_reads = start->nb_bytes && end->nb_bytes && data_bytes <= 16384; 817 if (merge_reads) { 818 buffer_size = start->nb_bytes + data_bytes + end->nb_bytes; 819 } else { 820 /* If we have to do two reads, add some padding in the middle 821 * if necessary to make sure that the end region is optimally 822 * aligned. */ 823 size_t align = bdrv_opt_mem_align(bs); 824 assert(align > 0 && align <= UINT_MAX); 825 assert(QEMU_ALIGN_UP(start->nb_bytes, align) <= 826 UINT_MAX - end->nb_bytes); 827 buffer_size = QEMU_ALIGN_UP(start->nb_bytes, align) + end->nb_bytes; 828 } 829 830 /* Reserve a buffer large enough to store all the data that we're 831 * going to read */ 832 start_buffer = qemu_try_blockalign(bs, buffer_size); 833 if (start_buffer == NULL) { 834 return -ENOMEM; 835 } 836 /* The part of the buffer where the end region is located */ 837 end_buffer = start_buffer + buffer_size - end->nb_bytes; 838 839 qemu_iovec_init(&qiov, 2 + (m->data_qiov ? m->data_qiov->niov : 0)); 840 841 qemu_co_mutex_unlock(&s->lock); 842 /* First we read the existing data from both COW regions. We 843 * either read the whole region in one go, or the start and end 844 * regions separately. */ 845 if (merge_reads) { 846 qemu_iovec_add(&qiov, start_buffer, buffer_size); 847 ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); 848 } else { 849 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 850 ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); 851 if (ret < 0) { 852 goto fail; 853 } 854 855 qemu_iovec_reset(&qiov); 856 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 857 ret = do_perform_cow_read(bs, m->offset, end->offset, &qiov); 858 } 859 if (ret < 0) { 860 goto fail; 861 } 862 863 /* Encrypt the data if necessary before writing it */ 864 if (bs->encrypted) { 865 if (!do_perform_cow_encrypt(bs, m->offset, m->alloc_offset, 866 start->offset, start_buffer, 867 start->nb_bytes) || 868 !do_perform_cow_encrypt(bs, m->offset, m->alloc_offset, 869 end->offset, end_buffer, end->nb_bytes)) { 870 ret = -EIO; 871 goto fail; 872 } 873 } 874 875 /* And now we can write everything. If we have the guest data we 876 * can write everything in one single operation */ 877 if (m->data_qiov) { 878 qemu_iovec_reset(&qiov); 879 if (start->nb_bytes) { 880 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 881 } 882 qemu_iovec_concat(&qiov, m->data_qiov, 0, data_bytes); 883 if (end->nb_bytes) { 884 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 885 } 886 /* NOTE: we have a write_aio blkdebug event here followed by 887 * a cow_write one in do_perform_cow_write(), but there's only 888 * one single I/O operation */ 889 BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); 890 ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); 891 } else { 892 /* If there's no guest data then write both COW regions separately */ 893 qemu_iovec_reset(&qiov); 894 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 895 ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); 896 if (ret < 0) { 897 goto fail; 898 } 899 900 qemu_iovec_reset(&qiov); 901 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 902 ret = do_perform_cow_write(bs, m->alloc_offset, end->offset, &qiov); 903 } 904 905 fail: 906 qemu_co_mutex_lock(&s->lock); 907 908 /* 909 * Before we update the L2 table to actually point to the new cluster, we 910 * need to be sure that the refcounts have been increased and COW was 911 * handled. 912 */ 913 if (ret == 0) { 914 qcow2_cache_depends_on_flush(s->l2_table_cache); 915 } 916 917 qemu_vfree(start_buffer); 918 qemu_iovec_destroy(&qiov); 919 return ret; 920 } 921 922 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) 923 { 924 BDRVQcow2State *s = bs->opaque; 925 int i, j = 0, l2_index, ret; 926 uint64_t *old_cluster, *l2_slice; 927 uint64_t cluster_offset = m->alloc_offset; 928 929 trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters); 930 assert(m->nb_clusters > 0); 931 932 old_cluster = g_try_new(uint64_t, m->nb_clusters); 933 if (old_cluster == NULL) { 934 ret = -ENOMEM; 935 goto err; 936 } 937 938 /* copy content of unmodified sectors */ 939 ret = perform_cow(bs, m); 940 if (ret < 0) { 941 goto err; 942 } 943 944 /* Update L2 table. */ 945 if (s->use_lazy_refcounts) { 946 qcow2_mark_dirty(bs); 947 } 948 if (qcow2_need_accurate_refcounts(s)) { 949 qcow2_cache_set_dependency(bs, s->l2_table_cache, 950 s->refcount_block_cache); 951 } 952 953 ret = get_cluster_table(bs, m->offset, &l2_slice, &l2_index); 954 if (ret < 0) { 955 goto err; 956 } 957 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 958 959 assert(l2_index + m->nb_clusters <= s->l2_slice_size); 960 for (i = 0; i < m->nb_clusters; i++) { 961 /* if two concurrent writes happen to the same unallocated cluster 962 * each write allocates separate cluster and writes data concurrently. 963 * The first one to complete updates l2 table with pointer to its 964 * cluster the second one has to do RMW (which is done above by 965 * perform_cow()), update l2 table with its cluster pointer and free 966 * old cluster. This is what this loop does */ 967 if (l2_slice[l2_index + i] != 0) { 968 old_cluster[j++] = l2_slice[l2_index + i]; 969 } 970 971 l2_slice[l2_index + i] = cpu_to_be64((cluster_offset + 972 (i << s->cluster_bits)) | QCOW_OFLAG_COPIED); 973 } 974 975 976 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 977 978 /* 979 * If this was a COW, we need to decrease the refcount of the old cluster. 980 * 981 * Don't discard clusters that reach a refcount of 0 (e.g. compressed 982 * clusters), the next write will reuse them anyway. 983 */ 984 if (!m->keep_old_clusters && j != 0) { 985 for (i = 0; i < j; i++) { 986 qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1, 987 QCOW2_DISCARD_NEVER); 988 } 989 } 990 991 ret = 0; 992 err: 993 g_free(old_cluster); 994 return ret; 995 } 996 997 /** 998 * Frees the allocated clusters because the request failed and they won't 999 * actually be linked. 1000 */ 1001 void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m) 1002 { 1003 BDRVQcow2State *s = bs->opaque; 1004 qcow2_free_clusters(bs, m->alloc_offset, m->nb_clusters << s->cluster_bits, 1005 QCOW2_DISCARD_NEVER); 1006 } 1007 1008 /* 1009 * Returns the number of contiguous clusters that can be used for an allocating 1010 * write, but require COW to be performed (this includes yet unallocated space, 1011 * which must copy from the backing file) 1012 */ 1013 static int count_cow_clusters(BDRVQcow2State *s, int nb_clusters, 1014 uint64_t *l2_slice, int l2_index) 1015 { 1016 int i; 1017 1018 for (i = 0; i < nb_clusters; i++) { 1019 uint64_t l2_entry = be64_to_cpu(l2_slice[l2_index + i]); 1020 QCow2ClusterType cluster_type = qcow2_get_cluster_type(l2_entry); 1021 1022 switch(cluster_type) { 1023 case QCOW2_CLUSTER_NORMAL: 1024 if (l2_entry & QCOW_OFLAG_COPIED) { 1025 goto out; 1026 } 1027 break; 1028 case QCOW2_CLUSTER_UNALLOCATED: 1029 case QCOW2_CLUSTER_COMPRESSED: 1030 case QCOW2_CLUSTER_ZERO_PLAIN: 1031 case QCOW2_CLUSTER_ZERO_ALLOC: 1032 break; 1033 default: 1034 abort(); 1035 } 1036 } 1037 1038 out: 1039 assert(i <= nb_clusters); 1040 return i; 1041 } 1042 1043 /* 1044 * Check if there already is an AIO write request in flight which allocates 1045 * the same cluster. In this case we need to wait until the previous 1046 * request has completed and updated the L2 table accordingly. 1047 * 1048 * Returns: 1049 * 0 if there was no dependency. *cur_bytes indicates the number of 1050 * bytes from guest_offset that can be read before the next 1051 * dependency must be processed (or the request is complete) 1052 * 1053 * -EAGAIN if we had to wait for another request, previously gathered 1054 * information on cluster allocation may be invalid now. The caller 1055 * must start over anyway, so consider *cur_bytes undefined. 1056 */ 1057 static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset, 1058 uint64_t *cur_bytes, QCowL2Meta **m) 1059 { 1060 BDRVQcow2State *s = bs->opaque; 1061 QCowL2Meta *old_alloc; 1062 uint64_t bytes = *cur_bytes; 1063 1064 QLIST_FOREACH(old_alloc, &s->cluster_allocs, next_in_flight) { 1065 1066 uint64_t start = guest_offset; 1067 uint64_t end = start + bytes; 1068 uint64_t old_start = l2meta_cow_start(old_alloc); 1069 uint64_t old_end = l2meta_cow_end(old_alloc); 1070 1071 if (end <= old_start || start >= old_end) { 1072 /* No intersection */ 1073 } else { 1074 if (start < old_start) { 1075 /* Stop at the start of a running allocation */ 1076 bytes = old_start - start; 1077 } else { 1078 bytes = 0; 1079 } 1080 1081 /* Stop if already an l2meta exists. After yielding, it wouldn't 1082 * be valid any more, so we'd have to clean up the old L2Metas 1083 * and deal with requests depending on them before starting to 1084 * gather new ones. Not worth the trouble. */ 1085 if (bytes == 0 && *m) { 1086 *cur_bytes = 0; 1087 return 0; 1088 } 1089 1090 if (bytes == 0) { 1091 /* Wait for the dependency to complete. We need to recheck 1092 * the free/allocated clusters when we continue. */ 1093 qemu_co_queue_wait(&old_alloc->dependent_requests, &s->lock); 1094 return -EAGAIN; 1095 } 1096 } 1097 } 1098 1099 /* Make sure that existing clusters and new allocations are only used up to 1100 * the next dependency if we shortened the request above */ 1101 *cur_bytes = bytes; 1102 1103 return 0; 1104 } 1105 1106 /* 1107 * Checks how many already allocated clusters that don't require a copy on 1108 * write there are at the given guest_offset (up to *bytes). If 1109 * *host_offset is not zero, only physically contiguous clusters beginning at 1110 * this host offset are counted. 1111 * 1112 * Note that guest_offset may not be cluster aligned. In this case, the 1113 * returned *host_offset points to exact byte referenced by guest_offset and 1114 * therefore isn't cluster aligned as well. 1115 * 1116 * Returns: 1117 * 0: if no allocated clusters are available at the given offset. 1118 * *bytes is normally unchanged. It is set to 0 if the cluster 1119 * is allocated and doesn't need COW, but doesn't have the right 1120 * physical offset. 1121 * 1122 * 1: if allocated clusters that don't require a COW are available at 1123 * the requested offset. *bytes may have decreased and describes 1124 * the length of the area that can be written to. 1125 * 1126 * -errno: in error cases 1127 */ 1128 static int handle_copied(BlockDriverState *bs, uint64_t guest_offset, 1129 uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) 1130 { 1131 BDRVQcow2State *s = bs->opaque; 1132 int l2_index; 1133 uint64_t cluster_offset; 1134 uint64_t *l2_slice; 1135 uint64_t nb_clusters; 1136 unsigned int keep_clusters; 1137 int ret; 1138 1139 trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset, *host_offset, 1140 *bytes); 1141 1142 assert(*host_offset == 0 || offset_into_cluster(s, guest_offset) 1143 == offset_into_cluster(s, *host_offset)); 1144 1145 /* 1146 * Calculate the number of clusters to look for. We stop at L2 slice 1147 * boundaries to keep things simple. 1148 */ 1149 nb_clusters = 1150 size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); 1151 1152 l2_index = offset_to_l2_slice_index(s, guest_offset); 1153 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1154 assert(nb_clusters <= INT_MAX); 1155 1156 /* Find L2 entry for the first involved cluster */ 1157 ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index); 1158 if (ret < 0) { 1159 return ret; 1160 } 1161 1162 cluster_offset = be64_to_cpu(l2_slice[l2_index]); 1163 1164 /* Check how many clusters are already allocated and don't need COW */ 1165 if (qcow2_get_cluster_type(cluster_offset) == QCOW2_CLUSTER_NORMAL 1166 && (cluster_offset & QCOW_OFLAG_COPIED)) 1167 { 1168 /* If a specific host_offset is required, check it */ 1169 bool offset_matches = 1170 (cluster_offset & L2E_OFFSET_MASK) == *host_offset; 1171 1172 if (offset_into_cluster(s, cluster_offset & L2E_OFFSET_MASK)) { 1173 qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset " 1174 "%#llx unaligned (guest offset: %#" PRIx64 1175 ")", cluster_offset & L2E_OFFSET_MASK, 1176 guest_offset); 1177 ret = -EIO; 1178 goto out; 1179 } 1180 1181 if (*host_offset != 0 && !offset_matches) { 1182 *bytes = 0; 1183 ret = 0; 1184 goto out; 1185 } 1186 1187 /* We keep all QCOW_OFLAG_COPIED clusters */ 1188 keep_clusters = 1189 count_contiguous_clusters(nb_clusters, s->cluster_size, 1190 &l2_slice[l2_index], 1191 QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO); 1192 assert(keep_clusters <= nb_clusters); 1193 1194 *bytes = MIN(*bytes, 1195 keep_clusters * s->cluster_size 1196 - offset_into_cluster(s, guest_offset)); 1197 1198 ret = 1; 1199 } else { 1200 ret = 0; 1201 } 1202 1203 /* Cleanup */ 1204 out: 1205 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1206 1207 /* Only return a host offset if we actually made progress. Otherwise we 1208 * would make requirements for handle_alloc() that it can't fulfill */ 1209 if (ret > 0) { 1210 *host_offset = (cluster_offset & L2E_OFFSET_MASK) 1211 + offset_into_cluster(s, guest_offset); 1212 } 1213 1214 return ret; 1215 } 1216 1217 /* 1218 * Allocates new clusters for the given guest_offset. 1219 * 1220 * At most *nb_clusters are allocated, and on return *nb_clusters is updated to 1221 * contain the number of clusters that have been allocated and are contiguous 1222 * in the image file. 1223 * 1224 * If *host_offset is non-zero, it specifies the offset in the image file at 1225 * which the new clusters must start. *nb_clusters can be 0 on return in this 1226 * case if the cluster at host_offset is already in use. If *host_offset is 1227 * zero, the clusters can be allocated anywhere in the image file. 1228 * 1229 * *host_offset is updated to contain the offset into the image file at which 1230 * the first allocated cluster starts. 1231 * 1232 * Return 0 on success and -errno in error cases. -EAGAIN means that the 1233 * function has been waiting for another request and the allocation must be 1234 * restarted, but the whole request should not be failed. 1235 */ 1236 static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset, 1237 uint64_t *host_offset, uint64_t *nb_clusters) 1238 { 1239 BDRVQcow2State *s = bs->opaque; 1240 1241 trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset, 1242 *host_offset, *nb_clusters); 1243 1244 /* Allocate new clusters */ 1245 trace_qcow2_cluster_alloc_phys(qemu_coroutine_self()); 1246 if (*host_offset == 0) { 1247 int64_t cluster_offset = 1248 qcow2_alloc_clusters(bs, *nb_clusters * s->cluster_size); 1249 if (cluster_offset < 0) { 1250 return cluster_offset; 1251 } 1252 *host_offset = cluster_offset; 1253 return 0; 1254 } else { 1255 int64_t ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters); 1256 if (ret < 0) { 1257 return ret; 1258 } 1259 *nb_clusters = ret; 1260 return 0; 1261 } 1262 } 1263 1264 /* 1265 * Allocates new clusters for an area that either is yet unallocated or needs a 1266 * copy on write. If *host_offset is non-zero, clusters are only allocated if 1267 * the new allocation can match the specified host offset. 1268 * 1269 * Note that guest_offset may not be cluster aligned. In this case, the 1270 * returned *host_offset points to exact byte referenced by guest_offset and 1271 * therefore isn't cluster aligned as well. 1272 * 1273 * Returns: 1274 * 0: if no clusters could be allocated. *bytes is set to 0, 1275 * *host_offset is left unchanged. 1276 * 1277 * 1: if new clusters were allocated. *bytes may be decreased if the 1278 * new allocation doesn't cover all of the requested area. 1279 * *host_offset is updated to contain the host offset of the first 1280 * newly allocated cluster. 1281 * 1282 * -errno: in error cases 1283 */ 1284 static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset, 1285 uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) 1286 { 1287 BDRVQcow2State *s = bs->opaque; 1288 int l2_index; 1289 uint64_t *l2_slice; 1290 uint64_t entry; 1291 uint64_t nb_clusters; 1292 int ret; 1293 bool keep_old_clusters = false; 1294 1295 uint64_t alloc_cluster_offset = 0; 1296 1297 trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset, 1298 *bytes); 1299 assert(*bytes > 0); 1300 1301 /* 1302 * Calculate the number of clusters to look for. We stop at L2 slice 1303 * boundaries to keep things simple. 1304 */ 1305 nb_clusters = 1306 size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); 1307 1308 l2_index = offset_to_l2_slice_index(s, guest_offset); 1309 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1310 assert(nb_clusters <= INT_MAX); 1311 1312 /* Find L2 entry for the first involved cluster */ 1313 ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index); 1314 if (ret < 0) { 1315 return ret; 1316 } 1317 1318 entry = be64_to_cpu(l2_slice[l2_index]); 1319 1320 /* For the moment, overwrite compressed clusters one by one */ 1321 if (entry & QCOW_OFLAG_COMPRESSED) { 1322 nb_clusters = 1; 1323 } else { 1324 nb_clusters = count_cow_clusters(s, nb_clusters, l2_slice, l2_index); 1325 } 1326 1327 /* This function is only called when there were no non-COW clusters, so if 1328 * we can't find any unallocated or COW clusters either, something is 1329 * wrong with our code. */ 1330 assert(nb_clusters > 0); 1331 1332 if (qcow2_get_cluster_type(entry) == QCOW2_CLUSTER_ZERO_ALLOC && 1333 (entry & QCOW_OFLAG_COPIED) && 1334 (!*host_offset || 1335 start_of_cluster(s, *host_offset) == (entry & L2E_OFFSET_MASK))) 1336 { 1337 int preallocated_nb_clusters; 1338 1339 if (offset_into_cluster(s, entry & L2E_OFFSET_MASK)) { 1340 qcow2_signal_corruption(bs, true, -1, -1, "Preallocated zero " 1341 "cluster offset %#llx unaligned (guest " 1342 "offset: %#" PRIx64 ")", 1343 entry & L2E_OFFSET_MASK, guest_offset); 1344 ret = -EIO; 1345 goto fail; 1346 } 1347 1348 /* Try to reuse preallocated zero clusters; contiguous normal clusters 1349 * would be fine, too, but count_cow_clusters() above has limited 1350 * nb_clusters already to a range of COW clusters */ 1351 preallocated_nb_clusters = 1352 count_contiguous_clusters(nb_clusters, s->cluster_size, 1353 &l2_slice[l2_index], QCOW_OFLAG_COPIED); 1354 assert(preallocated_nb_clusters > 0); 1355 1356 nb_clusters = preallocated_nb_clusters; 1357 alloc_cluster_offset = entry & L2E_OFFSET_MASK; 1358 1359 /* We want to reuse these clusters, so qcow2_alloc_cluster_link_l2() 1360 * should not free them. */ 1361 keep_old_clusters = true; 1362 } 1363 1364 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1365 1366 if (!alloc_cluster_offset) { 1367 /* Allocate, if necessary at a given offset in the image file */ 1368 alloc_cluster_offset = start_of_cluster(s, *host_offset); 1369 ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset, 1370 &nb_clusters); 1371 if (ret < 0) { 1372 goto fail; 1373 } 1374 1375 /* Can't extend contiguous allocation */ 1376 if (nb_clusters == 0) { 1377 *bytes = 0; 1378 return 0; 1379 } 1380 1381 /* !*host_offset would overwrite the image header and is reserved for 1382 * "no host offset preferred". If 0 was a valid host offset, it'd 1383 * trigger the following overlap check; do that now to avoid having an 1384 * invalid value in *host_offset. */ 1385 if (!alloc_cluster_offset) { 1386 ret = qcow2_pre_write_overlap_check(bs, 0, alloc_cluster_offset, 1387 nb_clusters * s->cluster_size); 1388 assert(ret < 0); 1389 goto fail; 1390 } 1391 } 1392 1393 /* 1394 * Save info needed for meta data update. 1395 * 1396 * requested_bytes: Number of bytes from the start of the first 1397 * newly allocated cluster to the end of the (possibly shortened 1398 * before) write request. 1399 * 1400 * avail_bytes: Number of bytes from the start of the first 1401 * newly allocated to the end of the last newly allocated cluster. 1402 * 1403 * nb_bytes: The number of bytes from the start of the first 1404 * newly allocated cluster to the end of the area that the write 1405 * request actually writes to (excluding COW at the end) 1406 */ 1407 uint64_t requested_bytes = *bytes + offset_into_cluster(s, guest_offset); 1408 int avail_bytes = MIN(INT_MAX, nb_clusters << s->cluster_bits); 1409 int nb_bytes = MIN(requested_bytes, avail_bytes); 1410 QCowL2Meta *old_m = *m; 1411 1412 *m = g_malloc0(sizeof(**m)); 1413 1414 **m = (QCowL2Meta) { 1415 .next = old_m, 1416 1417 .alloc_offset = alloc_cluster_offset, 1418 .offset = start_of_cluster(s, guest_offset), 1419 .nb_clusters = nb_clusters, 1420 1421 .keep_old_clusters = keep_old_clusters, 1422 1423 .cow_start = { 1424 .offset = 0, 1425 .nb_bytes = offset_into_cluster(s, guest_offset), 1426 }, 1427 .cow_end = { 1428 .offset = nb_bytes, 1429 .nb_bytes = avail_bytes - nb_bytes, 1430 }, 1431 }; 1432 qemu_co_queue_init(&(*m)->dependent_requests); 1433 QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight); 1434 1435 *host_offset = alloc_cluster_offset + offset_into_cluster(s, guest_offset); 1436 *bytes = MIN(*bytes, nb_bytes - offset_into_cluster(s, guest_offset)); 1437 assert(*bytes != 0); 1438 1439 return 1; 1440 1441 fail: 1442 if (*m && (*m)->nb_clusters > 0) { 1443 QLIST_REMOVE(*m, next_in_flight); 1444 } 1445 return ret; 1446 } 1447 1448 /* 1449 * alloc_cluster_offset 1450 * 1451 * For a given offset on the virtual disk, find the cluster offset in qcow2 1452 * file. If the offset is not found, allocate a new cluster. 1453 * 1454 * If the cluster was already allocated, m->nb_clusters is set to 0 and 1455 * other fields in m are meaningless. 1456 * 1457 * If the cluster is newly allocated, m->nb_clusters is set to the number of 1458 * contiguous clusters that have been allocated. In this case, the other 1459 * fields of m are valid and contain information about the first allocated 1460 * cluster. 1461 * 1462 * If the request conflicts with another write request in flight, the coroutine 1463 * is queued and will be reentered when the dependency has completed. 1464 * 1465 * Return 0 on success and -errno in error cases 1466 */ 1467 int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, 1468 unsigned int *bytes, uint64_t *host_offset, 1469 QCowL2Meta **m) 1470 { 1471 BDRVQcow2State *s = bs->opaque; 1472 uint64_t start, remaining; 1473 uint64_t cluster_offset; 1474 uint64_t cur_bytes; 1475 int ret; 1476 1477 trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, *bytes); 1478 1479 again: 1480 start = offset; 1481 remaining = *bytes; 1482 cluster_offset = 0; 1483 *host_offset = 0; 1484 cur_bytes = 0; 1485 *m = NULL; 1486 1487 while (true) { 1488 1489 if (!*host_offset) { 1490 *host_offset = start_of_cluster(s, cluster_offset); 1491 } 1492 1493 assert(remaining >= cur_bytes); 1494 1495 start += cur_bytes; 1496 remaining -= cur_bytes; 1497 cluster_offset += cur_bytes; 1498 1499 if (remaining == 0) { 1500 break; 1501 } 1502 1503 cur_bytes = remaining; 1504 1505 /* 1506 * Now start gathering as many contiguous clusters as possible: 1507 * 1508 * 1. Check for overlaps with in-flight allocations 1509 * 1510 * a) Overlap not in the first cluster -> shorten this request and 1511 * let the caller handle the rest in its next loop iteration. 1512 * 1513 * b) Real overlaps of two requests. Yield and restart the search 1514 * for contiguous clusters (the situation could have changed 1515 * while we were sleeping) 1516 * 1517 * c) TODO: Request starts in the same cluster as the in-flight 1518 * allocation ends. Shorten the COW of the in-fight allocation, 1519 * set cluster_offset to write to the same cluster and set up 1520 * the right synchronisation between the in-flight request and 1521 * the new one. 1522 */ 1523 ret = handle_dependencies(bs, start, &cur_bytes, m); 1524 if (ret == -EAGAIN) { 1525 /* Currently handle_dependencies() doesn't yield if we already had 1526 * an allocation. If it did, we would have to clean up the L2Meta 1527 * structs before starting over. */ 1528 assert(*m == NULL); 1529 goto again; 1530 } else if (ret < 0) { 1531 return ret; 1532 } else if (cur_bytes == 0) { 1533 break; 1534 } else { 1535 /* handle_dependencies() may have decreased cur_bytes (shortened 1536 * the allocations below) so that the next dependency is processed 1537 * correctly during the next loop iteration. */ 1538 } 1539 1540 /* 1541 * 2. Count contiguous COPIED clusters. 1542 */ 1543 ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m); 1544 if (ret < 0) { 1545 return ret; 1546 } else if (ret) { 1547 continue; 1548 } else if (cur_bytes == 0) { 1549 break; 1550 } 1551 1552 /* 1553 * 3. If the request still hasn't completed, allocate new clusters, 1554 * considering any cluster_offset of steps 1c or 2. 1555 */ 1556 ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m); 1557 if (ret < 0) { 1558 return ret; 1559 } else if (ret) { 1560 continue; 1561 } else { 1562 assert(cur_bytes == 0); 1563 break; 1564 } 1565 } 1566 1567 *bytes -= remaining; 1568 assert(*bytes > 0); 1569 assert(*host_offset != 0); 1570 1571 return 0; 1572 } 1573 1574 /* 1575 * This discards as many clusters of nb_clusters as possible at once (i.e. 1576 * all clusters in the same L2 slice) and returns the number of discarded 1577 * clusters. 1578 */ 1579 static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, 1580 uint64_t nb_clusters, 1581 enum qcow2_discard_type type, bool full_discard) 1582 { 1583 BDRVQcow2State *s = bs->opaque; 1584 uint64_t *l2_slice; 1585 int l2_index; 1586 int ret; 1587 int i; 1588 1589 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 1590 if (ret < 0) { 1591 return ret; 1592 } 1593 1594 /* Limit nb_clusters to one L2 slice */ 1595 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1596 assert(nb_clusters <= INT_MAX); 1597 1598 for (i = 0; i < nb_clusters; i++) { 1599 uint64_t old_l2_entry; 1600 1601 old_l2_entry = be64_to_cpu(l2_slice[l2_index + i]); 1602 1603 /* 1604 * If full_discard is false, make sure that a discarded area reads back 1605 * as zeroes for v3 images (we cannot do it for v2 without actually 1606 * writing a zero-filled buffer). We can skip the operation if the 1607 * cluster is already marked as zero, or if it's unallocated and we 1608 * don't have a backing file. 1609 * 1610 * TODO We might want to use bdrv_block_status(bs) here, but we're 1611 * holding s->lock, so that doesn't work today. 1612 * 1613 * If full_discard is true, the sector should not read back as zeroes, 1614 * but rather fall through to the backing file. 1615 */ 1616 switch (qcow2_get_cluster_type(old_l2_entry)) { 1617 case QCOW2_CLUSTER_UNALLOCATED: 1618 if (full_discard || !bs->backing) { 1619 continue; 1620 } 1621 break; 1622 1623 case QCOW2_CLUSTER_ZERO_PLAIN: 1624 if (!full_discard) { 1625 continue; 1626 } 1627 break; 1628 1629 case QCOW2_CLUSTER_ZERO_ALLOC: 1630 case QCOW2_CLUSTER_NORMAL: 1631 case QCOW2_CLUSTER_COMPRESSED: 1632 break; 1633 1634 default: 1635 abort(); 1636 } 1637 1638 /* First remove L2 entries */ 1639 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1640 if (!full_discard && s->qcow_version >= 3) { 1641 l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); 1642 } else { 1643 l2_slice[l2_index + i] = cpu_to_be64(0); 1644 } 1645 1646 /* Then decrease the refcount */ 1647 qcow2_free_any_clusters(bs, old_l2_entry, 1, type); 1648 } 1649 1650 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1651 1652 return nb_clusters; 1653 } 1654 1655 int qcow2_cluster_discard(BlockDriverState *bs, uint64_t offset, 1656 uint64_t bytes, enum qcow2_discard_type type, 1657 bool full_discard) 1658 { 1659 BDRVQcow2State *s = bs->opaque; 1660 uint64_t end_offset = offset + bytes; 1661 uint64_t nb_clusters; 1662 int64_t cleared; 1663 int ret; 1664 1665 /* Caller must pass aligned values, except at image end */ 1666 assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); 1667 assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || 1668 end_offset == bs->total_sectors << BDRV_SECTOR_BITS); 1669 1670 nb_clusters = size_to_clusters(s, bytes); 1671 1672 s->cache_discards = true; 1673 1674 /* Each L2 slice is handled by its own loop iteration */ 1675 while (nb_clusters > 0) { 1676 cleared = discard_in_l2_slice(bs, offset, nb_clusters, type, 1677 full_discard); 1678 if (cleared < 0) { 1679 ret = cleared; 1680 goto fail; 1681 } 1682 1683 nb_clusters -= cleared; 1684 offset += (cleared * s->cluster_size); 1685 } 1686 1687 ret = 0; 1688 fail: 1689 s->cache_discards = false; 1690 qcow2_process_discards(bs, ret); 1691 1692 return ret; 1693 } 1694 1695 /* 1696 * This zeroes as many clusters of nb_clusters as possible at once (i.e. 1697 * all clusters in the same L2 slice) and returns the number of zeroed 1698 * clusters. 1699 */ 1700 static int zero_in_l2_slice(BlockDriverState *bs, uint64_t offset, 1701 uint64_t nb_clusters, int flags) 1702 { 1703 BDRVQcow2State *s = bs->opaque; 1704 uint64_t *l2_slice; 1705 int l2_index; 1706 int ret; 1707 int i; 1708 bool unmap = !!(flags & BDRV_REQ_MAY_UNMAP); 1709 1710 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 1711 if (ret < 0) { 1712 return ret; 1713 } 1714 1715 /* Limit nb_clusters to one L2 slice */ 1716 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1717 assert(nb_clusters <= INT_MAX); 1718 1719 for (i = 0; i < nb_clusters; i++) { 1720 uint64_t old_offset; 1721 QCow2ClusterType cluster_type; 1722 1723 old_offset = be64_to_cpu(l2_slice[l2_index + i]); 1724 1725 /* 1726 * Minimize L2 changes if the cluster already reads back as 1727 * zeroes with correct allocation. 1728 */ 1729 cluster_type = qcow2_get_cluster_type(old_offset); 1730 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN || 1731 (cluster_type == QCOW2_CLUSTER_ZERO_ALLOC && !unmap)) { 1732 continue; 1733 } 1734 1735 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1736 if (cluster_type == QCOW2_CLUSTER_COMPRESSED || unmap) { 1737 l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); 1738 qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); 1739 } else { 1740 l2_slice[l2_index + i] |= cpu_to_be64(QCOW_OFLAG_ZERO); 1741 } 1742 } 1743 1744 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1745 1746 return nb_clusters; 1747 } 1748 1749 int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset, 1750 uint64_t bytes, int flags) 1751 { 1752 BDRVQcow2State *s = bs->opaque; 1753 uint64_t end_offset = offset + bytes; 1754 uint64_t nb_clusters; 1755 int64_t cleared; 1756 int ret; 1757 1758 /* Caller must pass aligned values, except at image end */ 1759 assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); 1760 assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || 1761 end_offset == bs->total_sectors << BDRV_SECTOR_BITS); 1762 1763 /* The zero flag is only supported by version 3 and newer */ 1764 if (s->qcow_version < 3) { 1765 return -ENOTSUP; 1766 } 1767 1768 /* Each L2 slice is handled by its own loop iteration */ 1769 nb_clusters = size_to_clusters(s, bytes); 1770 1771 s->cache_discards = true; 1772 1773 while (nb_clusters > 0) { 1774 cleared = zero_in_l2_slice(bs, offset, nb_clusters, flags); 1775 if (cleared < 0) { 1776 ret = cleared; 1777 goto fail; 1778 } 1779 1780 nb_clusters -= cleared; 1781 offset += (cleared * s->cluster_size); 1782 } 1783 1784 ret = 0; 1785 fail: 1786 s->cache_discards = false; 1787 qcow2_process_discards(bs, ret); 1788 1789 return ret; 1790 } 1791 1792 /* 1793 * Expands all zero clusters in a specific L1 table (or deallocates them, for 1794 * non-backed non-pre-allocated zero clusters). 1795 * 1796 * l1_entries and *visited_l1_entries are used to keep track of progress for 1797 * status_cb(). l1_entries contains the total number of L1 entries and 1798 * *visited_l1_entries counts all visited L1 entries. 1799 */ 1800 static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table, 1801 int l1_size, int64_t *visited_l1_entries, 1802 int64_t l1_entries, 1803 BlockDriverAmendStatusCB *status_cb, 1804 void *cb_opaque) 1805 { 1806 BDRVQcow2State *s = bs->opaque; 1807 bool is_active_l1 = (l1_table == s->l1_table); 1808 uint64_t *l2_slice = NULL; 1809 unsigned slice, slice_size2, n_slices; 1810 int ret; 1811 int i, j; 1812 1813 slice_size2 = s->l2_slice_size * sizeof(uint64_t); 1814 n_slices = s->cluster_size / slice_size2; 1815 1816 if (!is_active_l1) { 1817 /* inactive L2 tables require a buffer to be stored in when loading 1818 * them from disk */ 1819 l2_slice = qemu_try_blockalign(bs->file->bs, slice_size2); 1820 if (l2_slice == NULL) { 1821 return -ENOMEM; 1822 } 1823 } 1824 1825 for (i = 0; i < l1_size; i++) { 1826 uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK; 1827 uint64_t l2_refcount; 1828 1829 if (!l2_offset) { 1830 /* unallocated */ 1831 (*visited_l1_entries)++; 1832 if (status_cb) { 1833 status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); 1834 } 1835 continue; 1836 } 1837 1838 if (offset_into_cluster(s, l2_offset)) { 1839 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" 1840 PRIx64 " unaligned (L1 index: %#x)", 1841 l2_offset, i); 1842 ret = -EIO; 1843 goto fail; 1844 } 1845 1846 ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits, 1847 &l2_refcount); 1848 if (ret < 0) { 1849 goto fail; 1850 } 1851 1852 for (slice = 0; slice < n_slices; slice++) { 1853 uint64_t slice_offset = l2_offset + slice * slice_size2; 1854 bool l2_dirty = false; 1855 if (is_active_l1) { 1856 /* get active L2 tables from cache */ 1857 ret = qcow2_cache_get(bs, s->l2_table_cache, slice_offset, 1858 (void **)&l2_slice); 1859 } else { 1860 /* load inactive L2 tables from disk */ 1861 ret = bdrv_pread(bs->file, slice_offset, l2_slice, slice_size2); 1862 } 1863 if (ret < 0) { 1864 goto fail; 1865 } 1866 1867 for (j = 0; j < s->l2_slice_size; j++) { 1868 uint64_t l2_entry = be64_to_cpu(l2_slice[j]); 1869 int64_t offset = l2_entry & L2E_OFFSET_MASK; 1870 QCow2ClusterType cluster_type = 1871 qcow2_get_cluster_type(l2_entry); 1872 1873 if (cluster_type != QCOW2_CLUSTER_ZERO_PLAIN && 1874 cluster_type != QCOW2_CLUSTER_ZERO_ALLOC) { 1875 continue; 1876 } 1877 1878 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1879 if (!bs->backing) { 1880 /* not backed; therefore we can simply deallocate the 1881 * cluster */ 1882 l2_slice[j] = 0; 1883 l2_dirty = true; 1884 continue; 1885 } 1886 1887 offset = qcow2_alloc_clusters(bs, s->cluster_size); 1888 if (offset < 0) { 1889 ret = offset; 1890 goto fail; 1891 } 1892 1893 if (l2_refcount > 1) { 1894 /* For shared L2 tables, set the refcount accordingly 1895 * (it is already 1 and needs to be l2_refcount) */ 1896 ret = qcow2_update_cluster_refcount( 1897 bs, offset >> s->cluster_bits, 1898 refcount_diff(1, l2_refcount), false, 1899 QCOW2_DISCARD_OTHER); 1900 if (ret < 0) { 1901 qcow2_free_clusters(bs, offset, s->cluster_size, 1902 QCOW2_DISCARD_OTHER); 1903 goto fail; 1904 } 1905 } 1906 } 1907 1908 if (offset_into_cluster(s, offset)) { 1909 int l2_index = slice * s->l2_slice_size + j; 1910 qcow2_signal_corruption( 1911 bs, true, -1, -1, 1912 "Cluster allocation offset " 1913 "%#" PRIx64 " unaligned (L2 offset: %#" 1914 PRIx64 ", L2 index: %#x)", offset, 1915 l2_offset, l2_index); 1916 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1917 qcow2_free_clusters(bs, offset, s->cluster_size, 1918 QCOW2_DISCARD_ALWAYS); 1919 } 1920 ret = -EIO; 1921 goto fail; 1922 } 1923 1924 ret = qcow2_pre_write_overlap_check(bs, 0, offset, 1925 s->cluster_size); 1926 if (ret < 0) { 1927 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1928 qcow2_free_clusters(bs, offset, s->cluster_size, 1929 QCOW2_DISCARD_ALWAYS); 1930 } 1931 goto fail; 1932 } 1933 1934 ret = bdrv_pwrite_zeroes(bs->file, offset, s->cluster_size, 0); 1935 if (ret < 0) { 1936 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1937 qcow2_free_clusters(bs, offset, s->cluster_size, 1938 QCOW2_DISCARD_ALWAYS); 1939 } 1940 goto fail; 1941 } 1942 1943 if (l2_refcount == 1) { 1944 l2_slice[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED); 1945 } else { 1946 l2_slice[j] = cpu_to_be64(offset); 1947 } 1948 l2_dirty = true; 1949 } 1950 1951 if (is_active_l1) { 1952 if (l2_dirty) { 1953 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1954 qcow2_cache_depends_on_flush(s->l2_table_cache); 1955 } 1956 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1957 } else { 1958 if (l2_dirty) { 1959 ret = qcow2_pre_write_overlap_check( 1960 bs, QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2, 1961 slice_offset, slice_size2); 1962 if (ret < 0) { 1963 goto fail; 1964 } 1965 1966 ret = bdrv_pwrite(bs->file, slice_offset, 1967 l2_slice, slice_size2); 1968 if (ret < 0) { 1969 goto fail; 1970 } 1971 } 1972 } 1973 } 1974 1975 (*visited_l1_entries)++; 1976 if (status_cb) { 1977 status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); 1978 } 1979 } 1980 1981 ret = 0; 1982 1983 fail: 1984 if (l2_slice) { 1985 if (!is_active_l1) { 1986 qemu_vfree(l2_slice); 1987 } else { 1988 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1989 } 1990 } 1991 return ret; 1992 } 1993 1994 /* 1995 * For backed images, expands all zero clusters on the image. For non-backed 1996 * images, deallocates all non-pre-allocated zero clusters (and claims the 1997 * allocation for pre-allocated ones). This is important for downgrading to a 1998 * qcow2 version which doesn't yet support metadata zero clusters. 1999 */ 2000 int qcow2_expand_zero_clusters(BlockDriverState *bs, 2001 BlockDriverAmendStatusCB *status_cb, 2002 void *cb_opaque) 2003 { 2004 BDRVQcow2State *s = bs->opaque; 2005 uint64_t *l1_table = NULL; 2006 int64_t l1_entries = 0, visited_l1_entries = 0; 2007 int ret; 2008 int i, j; 2009 2010 if (status_cb) { 2011 l1_entries = s->l1_size; 2012 for (i = 0; i < s->nb_snapshots; i++) { 2013 l1_entries += s->snapshots[i].l1_size; 2014 } 2015 } 2016 2017 ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size, 2018 &visited_l1_entries, l1_entries, 2019 status_cb, cb_opaque); 2020 if (ret < 0) { 2021 goto fail; 2022 } 2023 2024 /* Inactive L1 tables may point to active L2 tables - therefore it is 2025 * necessary to flush the L2 table cache before trying to access the L2 2026 * tables pointed to by inactive L1 entries (else we might try to expand 2027 * zero clusters that have already been expanded); furthermore, it is also 2028 * necessary to empty the L2 table cache, since it may contain tables which 2029 * are now going to be modified directly on disk, bypassing the cache. 2030 * qcow2_cache_empty() does both for us. */ 2031 ret = qcow2_cache_empty(bs, s->l2_table_cache); 2032 if (ret < 0) { 2033 goto fail; 2034 } 2035 2036 for (i = 0; i < s->nb_snapshots; i++) { 2037 int l1_size2; 2038 uint64_t *new_l1_table; 2039 Error *local_err = NULL; 2040 2041 ret = qcow2_validate_table(bs, s->snapshots[i].l1_table_offset, 2042 s->snapshots[i].l1_size, sizeof(uint64_t), 2043 QCOW_MAX_L1_SIZE, "Snapshot L1 table", 2044 &local_err); 2045 if (ret < 0) { 2046 error_report_err(local_err); 2047 goto fail; 2048 } 2049 2050 l1_size2 = s->snapshots[i].l1_size * sizeof(uint64_t); 2051 new_l1_table = g_try_realloc(l1_table, l1_size2); 2052 2053 if (!new_l1_table) { 2054 ret = -ENOMEM; 2055 goto fail; 2056 } 2057 2058 l1_table = new_l1_table; 2059 2060 ret = bdrv_pread(bs->file, s->snapshots[i].l1_table_offset, 2061 l1_table, l1_size2); 2062 if (ret < 0) { 2063 goto fail; 2064 } 2065 2066 for (j = 0; j < s->snapshots[i].l1_size; j++) { 2067 be64_to_cpus(&l1_table[j]); 2068 } 2069 2070 ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size, 2071 &visited_l1_entries, l1_entries, 2072 status_cb, cb_opaque); 2073 if (ret < 0) { 2074 goto fail; 2075 } 2076 } 2077 2078 ret = 0; 2079 2080 fail: 2081 g_free(l1_table); 2082 return ret; 2083 } 2084