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 "qcow2.h" 30 #include "qemu/bswap.h" 31 #include "trace.h" 32 33 int qcow2_shrink_l1_table(BlockDriverState *bs, uint64_t exact_size) 34 { 35 BDRVQcow2State *s = bs->opaque; 36 int new_l1_size, i, ret; 37 38 if (exact_size >= s->l1_size) { 39 return 0; 40 } 41 42 new_l1_size = exact_size; 43 44 #ifdef DEBUG_ALLOC2 45 fprintf(stderr, "shrink l1_table from %d to %d\n", s->l1_size, new_l1_size); 46 #endif 47 48 BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_WRITE_TABLE); 49 ret = bdrv_pwrite_zeroes(bs->file, s->l1_table_offset + 50 new_l1_size * sizeof(uint64_t), 51 (s->l1_size - new_l1_size) * sizeof(uint64_t), 0); 52 if (ret < 0) { 53 goto fail; 54 } 55 56 ret = bdrv_flush(bs->file->bs); 57 if (ret < 0) { 58 goto fail; 59 } 60 61 BLKDBG_EVENT(bs->file, BLKDBG_L1_SHRINK_FREE_L2_CLUSTERS); 62 for (i = s->l1_size - 1; i > new_l1_size - 1; i--) { 63 if ((s->l1_table[i] & L1E_OFFSET_MASK) == 0) { 64 continue; 65 } 66 qcow2_free_clusters(bs, s->l1_table[i] & L1E_OFFSET_MASK, 67 s->cluster_size, QCOW2_DISCARD_ALWAYS); 68 s->l1_table[i] = 0; 69 } 70 return 0; 71 72 fail: 73 /* 74 * If the write in the l1_table failed the image may contain a partially 75 * overwritten l1_table. In this case it would be better to clear the 76 * l1_table in memory to avoid possible image corruption. 77 */ 78 memset(s->l1_table + new_l1_size, 0, 79 (s->l1_size - new_l1_size) * sizeof(uint64_t)); 80 return ret; 81 } 82 83 int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, 84 bool exact_size) 85 { 86 BDRVQcow2State *s = bs->opaque; 87 int new_l1_size2, ret, i; 88 uint64_t *new_l1_table; 89 int64_t old_l1_table_offset, old_l1_size; 90 int64_t new_l1_table_offset, new_l1_size; 91 uint8_t data[12]; 92 93 if (min_size <= s->l1_size) 94 return 0; 95 96 /* Do a sanity check on min_size before trying to calculate new_l1_size 97 * (this prevents overflows during the while loop for the calculation of 98 * new_l1_size) */ 99 if (min_size > INT_MAX / sizeof(uint64_t)) { 100 return -EFBIG; 101 } 102 103 if (exact_size) { 104 new_l1_size = min_size; 105 } else { 106 /* Bump size up to reduce the number of times we have to grow */ 107 new_l1_size = s->l1_size; 108 if (new_l1_size == 0) { 109 new_l1_size = 1; 110 } 111 while (min_size > new_l1_size) { 112 new_l1_size = DIV_ROUND_UP(new_l1_size * 3, 2); 113 } 114 } 115 116 QEMU_BUILD_BUG_ON(QCOW_MAX_L1_SIZE > INT_MAX); 117 if (new_l1_size > QCOW_MAX_L1_SIZE / sizeof(uint64_t)) { 118 return -EFBIG; 119 } 120 121 #ifdef DEBUG_ALLOC2 122 fprintf(stderr, "grow l1_table from %d to %" PRId64 "\n", 123 s->l1_size, new_l1_size); 124 #endif 125 126 new_l1_size2 = sizeof(uint64_t) * new_l1_size; 127 new_l1_table = qemu_try_blockalign(bs->file->bs, 128 ROUND_UP(new_l1_size2, 512)); 129 if (new_l1_table == NULL) { 130 return -ENOMEM; 131 } 132 memset(new_l1_table, 0, ROUND_UP(new_l1_size2, 512)); 133 134 if (s->l1_size) { 135 memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t)); 136 } 137 138 /* write new table (align to cluster) */ 139 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ALLOC_TABLE); 140 new_l1_table_offset = qcow2_alloc_clusters(bs, new_l1_size2); 141 if (new_l1_table_offset < 0) { 142 qemu_vfree(new_l1_table); 143 return new_l1_table_offset; 144 } 145 146 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 147 if (ret < 0) { 148 goto fail; 149 } 150 151 /* the L1 position has not yet been updated, so these clusters must 152 * indeed be completely free */ 153 ret = qcow2_pre_write_overlap_check(bs, 0, new_l1_table_offset, 154 new_l1_size2, false); 155 if (ret < 0) { 156 goto fail; 157 } 158 159 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_WRITE_TABLE); 160 for(i = 0; i < s->l1_size; i++) 161 new_l1_table[i] = cpu_to_be64(new_l1_table[i]); 162 ret = bdrv_pwrite_sync(bs->file, new_l1_table_offset, 163 new_l1_table, new_l1_size2); 164 if (ret < 0) 165 goto fail; 166 for(i = 0; i < s->l1_size; i++) 167 new_l1_table[i] = be64_to_cpu(new_l1_table[i]); 168 169 /* set new table */ 170 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ACTIVATE_TABLE); 171 stl_be_p(data, new_l1_size); 172 stq_be_p(data + 4, new_l1_table_offset); 173 ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size), 174 data, sizeof(data)); 175 if (ret < 0) { 176 goto fail; 177 } 178 qemu_vfree(s->l1_table); 179 old_l1_table_offset = s->l1_table_offset; 180 s->l1_table_offset = new_l1_table_offset; 181 s->l1_table = new_l1_table; 182 old_l1_size = s->l1_size; 183 s->l1_size = new_l1_size; 184 qcow2_free_clusters(bs, old_l1_table_offset, old_l1_size * sizeof(uint64_t), 185 QCOW2_DISCARD_OTHER); 186 return 0; 187 fail: 188 qemu_vfree(new_l1_table); 189 qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2, 190 QCOW2_DISCARD_OTHER); 191 return ret; 192 } 193 194 /* 195 * l2_load 196 * 197 * @bs: The BlockDriverState 198 * @offset: A guest offset, used to calculate what slice of the L2 199 * table to load. 200 * @l2_offset: Offset to the L2 table in the image file. 201 * @l2_slice: Location to store the pointer to the L2 slice. 202 * 203 * Loads a L2 slice into memory (L2 slices are the parts of L2 tables 204 * that are loaded by the qcow2 cache). If the slice is in the cache, 205 * the cache is used; otherwise the L2 slice is loaded from the image 206 * file. 207 */ 208 static int l2_load(BlockDriverState *bs, uint64_t offset, 209 uint64_t l2_offset, uint64_t **l2_slice) 210 { 211 BDRVQcow2State *s = bs->opaque; 212 int start_of_slice = sizeof(uint64_t) * 213 (offset_to_l2_index(s, offset) - offset_to_l2_slice_index(s, offset)); 214 215 return qcow2_cache_get(bs, s->l2_table_cache, l2_offset + start_of_slice, 216 (void **)l2_slice); 217 } 218 219 /* 220 * Writes one sector of the L1 table to the disk (can't update single entries 221 * and we really don't want bdrv_pread to perform a read-modify-write) 222 */ 223 #define L1_ENTRIES_PER_SECTOR (512 / 8) 224 int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index) 225 { 226 BDRVQcow2State *s = bs->opaque; 227 uint64_t buf[L1_ENTRIES_PER_SECTOR] = { 0 }; 228 int l1_start_index; 229 int i, ret; 230 231 l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1); 232 for (i = 0; i < L1_ENTRIES_PER_SECTOR && l1_start_index + i < s->l1_size; 233 i++) 234 { 235 buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]); 236 } 237 238 ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1, 239 s->l1_table_offset + 8 * l1_start_index, sizeof(buf), false); 240 if (ret < 0) { 241 return ret; 242 } 243 244 BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE); 245 ret = bdrv_pwrite_sync(bs->file, 246 s->l1_table_offset + 8 * l1_start_index, 247 buf, sizeof(buf)); 248 if (ret < 0) { 249 return ret; 250 } 251 252 return 0; 253 } 254 255 /* 256 * l2_allocate 257 * 258 * Allocate a new l2 entry in the file. If l1_index points to an already 259 * used entry in the L2 table (i.e. we are doing a copy on write for the L2 260 * table) copy the contents of the old L2 table into the newly allocated one. 261 * Otherwise the new table is initialized with zeros. 262 * 263 */ 264 265 static int l2_allocate(BlockDriverState *bs, int l1_index) 266 { 267 BDRVQcow2State *s = bs->opaque; 268 uint64_t old_l2_offset; 269 uint64_t *l2_slice = NULL; 270 unsigned slice, slice_size2, n_slices; 271 int64_t l2_offset; 272 int ret; 273 274 old_l2_offset = s->l1_table[l1_index]; 275 276 trace_qcow2_l2_allocate(bs, l1_index); 277 278 /* allocate a new l2 entry */ 279 280 l2_offset = qcow2_alloc_clusters(bs, s->l2_size * sizeof(uint64_t)); 281 if (l2_offset < 0) { 282 ret = l2_offset; 283 goto fail; 284 } 285 286 /* The offset must fit in the offset field of the L1 table entry */ 287 assert((l2_offset & L1E_OFFSET_MASK) == l2_offset); 288 289 /* If we're allocating the table at offset 0 then something is wrong */ 290 if (l2_offset == 0) { 291 qcow2_signal_corruption(bs, true, -1, -1, "Preventing invalid " 292 "allocation of L2 table at offset 0"); 293 ret = -EIO; 294 goto fail; 295 } 296 297 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 298 if (ret < 0) { 299 goto fail; 300 } 301 302 /* allocate a new entry in the l2 cache */ 303 304 slice_size2 = s->l2_slice_size * sizeof(uint64_t); 305 n_slices = s->cluster_size / slice_size2; 306 307 trace_qcow2_l2_allocate_get_empty(bs, l1_index); 308 for (slice = 0; slice < n_slices; slice++) { 309 ret = qcow2_cache_get_empty(bs, s->l2_table_cache, 310 l2_offset + slice * slice_size2, 311 (void **) &l2_slice); 312 if (ret < 0) { 313 goto fail; 314 } 315 316 if ((old_l2_offset & L1E_OFFSET_MASK) == 0) { 317 /* if there was no old l2 table, clear the new slice */ 318 memset(l2_slice, 0, slice_size2); 319 } else { 320 uint64_t *old_slice; 321 uint64_t old_l2_slice_offset = 322 (old_l2_offset & L1E_OFFSET_MASK) + slice * slice_size2; 323 324 /* if there was an old l2 table, read a slice from the disk */ 325 BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ); 326 ret = qcow2_cache_get(bs, s->l2_table_cache, old_l2_slice_offset, 327 (void **) &old_slice); 328 if (ret < 0) { 329 goto fail; 330 } 331 332 memcpy(l2_slice, old_slice, slice_size2); 333 334 qcow2_cache_put(s->l2_table_cache, (void **) &old_slice); 335 } 336 337 /* write the l2 slice to the file */ 338 BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_WRITE); 339 340 trace_qcow2_l2_allocate_write_l2(bs, l1_index); 341 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 342 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 343 } 344 345 ret = qcow2_cache_flush(bs, s->l2_table_cache); 346 if (ret < 0) { 347 goto fail; 348 } 349 350 /* update the L1 entry */ 351 trace_qcow2_l2_allocate_write_l1(bs, l1_index); 352 s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED; 353 ret = qcow2_write_l1_entry(bs, l1_index); 354 if (ret < 0) { 355 goto fail; 356 } 357 358 trace_qcow2_l2_allocate_done(bs, l1_index, 0); 359 return 0; 360 361 fail: 362 trace_qcow2_l2_allocate_done(bs, l1_index, ret); 363 if (l2_slice != NULL) { 364 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 365 } 366 s->l1_table[l1_index] = old_l2_offset; 367 if (l2_offset > 0) { 368 qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), 369 QCOW2_DISCARD_ALWAYS); 370 } 371 return ret; 372 } 373 374 /* 375 * Checks how many clusters in a given L2 slice are contiguous in the image 376 * file. As soon as one of the flags in the bitmask stop_flags changes compared 377 * to the first cluster, the search is stopped and the cluster is not counted 378 * as contiguous. (This allows it, for example, to stop at the first compressed 379 * cluster which may require a different handling) 380 */ 381 static int count_contiguous_clusters(BlockDriverState *bs, int nb_clusters, 382 int cluster_size, uint64_t *l2_slice, uint64_t stop_flags) 383 { 384 int i; 385 QCow2ClusterType first_cluster_type; 386 uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED; 387 uint64_t first_entry = be64_to_cpu(l2_slice[0]); 388 uint64_t offset = first_entry & mask; 389 390 first_cluster_type = qcow2_get_cluster_type(bs, first_entry); 391 if (first_cluster_type == QCOW2_CLUSTER_UNALLOCATED) { 392 return 0; 393 } 394 395 /* must be allocated */ 396 assert(first_cluster_type == QCOW2_CLUSTER_NORMAL || 397 first_cluster_type == QCOW2_CLUSTER_ZERO_ALLOC); 398 399 for (i = 0; i < nb_clusters; i++) { 400 uint64_t l2_entry = be64_to_cpu(l2_slice[i]) & mask; 401 if (offset + (uint64_t) i * cluster_size != l2_entry) { 402 break; 403 } 404 } 405 406 return i; 407 } 408 409 /* 410 * Checks how many consecutive unallocated clusters in a given L2 411 * slice have the same cluster type. 412 */ 413 static int count_contiguous_clusters_unallocated(BlockDriverState *bs, 414 int nb_clusters, 415 uint64_t *l2_slice, 416 QCow2ClusterType wanted_type) 417 { 418 int i; 419 420 assert(wanted_type == QCOW2_CLUSTER_ZERO_PLAIN || 421 wanted_type == QCOW2_CLUSTER_UNALLOCATED); 422 for (i = 0; i < nb_clusters; i++) { 423 uint64_t entry = be64_to_cpu(l2_slice[i]); 424 QCow2ClusterType type = qcow2_get_cluster_type(bs, entry); 425 426 if (type != wanted_type) { 427 break; 428 } 429 } 430 431 return i; 432 } 433 434 static int coroutine_fn do_perform_cow_read(BlockDriverState *bs, 435 uint64_t src_cluster_offset, 436 unsigned offset_in_cluster, 437 QEMUIOVector *qiov) 438 { 439 int ret; 440 441 if (qiov->size == 0) { 442 return 0; 443 } 444 445 BLKDBG_EVENT(bs->file, BLKDBG_COW_READ); 446 447 if (!bs->drv) { 448 return -ENOMEDIUM; 449 } 450 451 /* Call .bdrv_co_readv() directly instead of using the public block-layer 452 * interface. This avoids double I/O throttling and request tracking, 453 * which can lead to deadlock when block layer copy-on-read is enabled. 454 */ 455 ret = bs->drv->bdrv_co_preadv_part(bs, 456 src_cluster_offset + offset_in_cluster, 457 qiov->size, qiov, 0, 0); 458 if (ret < 0) { 459 return ret; 460 } 461 462 return 0; 463 } 464 465 static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs, 466 uint64_t src_cluster_offset, 467 uint64_t cluster_offset, 468 unsigned offset_in_cluster, 469 uint8_t *buffer, 470 unsigned bytes) 471 { 472 if (bytes && bs->encrypted) { 473 BDRVQcow2State *s = bs->opaque; 474 assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0); 475 assert((bytes & ~BDRV_SECTOR_MASK) == 0); 476 assert(s->crypto); 477 if (qcow2_co_encrypt(bs, cluster_offset, 478 src_cluster_offset + offset_in_cluster, 479 buffer, bytes) < 0) { 480 return false; 481 } 482 } 483 return true; 484 } 485 486 static int coroutine_fn do_perform_cow_write(BlockDriverState *bs, 487 uint64_t cluster_offset, 488 unsigned offset_in_cluster, 489 QEMUIOVector *qiov) 490 { 491 BDRVQcow2State *s = bs->opaque; 492 int ret; 493 494 if (qiov->size == 0) { 495 return 0; 496 } 497 498 ret = qcow2_pre_write_overlap_check(bs, 0, 499 cluster_offset + offset_in_cluster, qiov->size, true); 500 if (ret < 0) { 501 return ret; 502 } 503 504 BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE); 505 ret = bdrv_co_pwritev(s->data_file, cluster_offset + offset_in_cluster, 506 qiov->size, qiov, 0); 507 if (ret < 0) { 508 return ret; 509 } 510 511 return 0; 512 } 513 514 515 /* 516 * get_cluster_offset 517 * 518 * For a given offset of the virtual disk, find the cluster type and offset in 519 * the qcow2 file. The offset is stored in *cluster_offset. 520 * 521 * On entry, *bytes is the maximum number of contiguous bytes starting at 522 * offset that we are interested in. 523 * 524 * On exit, *bytes is the number of bytes starting at offset that have the same 525 * cluster type and (if applicable) are stored contiguously in the image file. 526 * Compressed clusters are always returned one by one. 527 * 528 * Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error 529 * cases. 530 */ 531 int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset, 532 unsigned int *bytes, uint64_t *cluster_offset) 533 { 534 BDRVQcow2State *s = bs->opaque; 535 unsigned int l2_index; 536 uint64_t l1_index, l2_offset, *l2_slice; 537 int c; 538 unsigned int offset_in_cluster; 539 uint64_t bytes_available, bytes_needed, nb_clusters; 540 QCow2ClusterType type; 541 int ret; 542 543 offset_in_cluster = offset_into_cluster(s, offset); 544 bytes_needed = (uint64_t) *bytes + offset_in_cluster; 545 546 /* compute how many bytes there are between the start of the cluster 547 * containing offset and the end of the l2 slice that contains 548 * the entry pointing to it */ 549 bytes_available = 550 ((uint64_t) (s->l2_slice_size - offset_to_l2_slice_index(s, offset))) 551 << s->cluster_bits; 552 553 if (bytes_needed > bytes_available) { 554 bytes_needed = bytes_available; 555 } 556 557 *cluster_offset = 0; 558 559 /* seek to the l2 offset in the l1 table */ 560 561 l1_index = offset_to_l1_index(s, offset); 562 if (l1_index >= s->l1_size) { 563 type = QCOW2_CLUSTER_UNALLOCATED; 564 goto out; 565 } 566 567 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 568 if (!l2_offset) { 569 type = QCOW2_CLUSTER_UNALLOCATED; 570 goto out; 571 } 572 573 if (offset_into_cluster(s, l2_offset)) { 574 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 575 " unaligned (L1 index: %#" PRIx64 ")", 576 l2_offset, l1_index); 577 return -EIO; 578 } 579 580 /* load the l2 slice in memory */ 581 582 ret = l2_load(bs, offset, l2_offset, &l2_slice); 583 if (ret < 0) { 584 return ret; 585 } 586 587 /* find the cluster offset for the given disk offset */ 588 589 l2_index = offset_to_l2_slice_index(s, offset); 590 *cluster_offset = be64_to_cpu(l2_slice[l2_index]); 591 592 nb_clusters = size_to_clusters(s, bytes_needed); 593 /* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned 594 * integers; the minimum cluster size is 512, so this assertion is always 595 * true */ 596 assert(nb_clusters <= INT_MAX); 597 598 type = qcow2_get_cluster_type(bs, *cluster_offset); 599 if (s->qcow_version < 3 && (type == QCOW2_CLUSTER_ZERO_PLAIN || 600 type == QCOW2_CLUSTER_ZERO_ALLOC)) { 601 qcow2_signal_corruption(bs, true, -1, -1, "Zero cluster entry found" 602 " in pre-v3 image (L2 offset: %#" PRIx64 603 ", L2 index: %#x)", l2_offset, l2_index); 604 ret = -EIO; 605 goto fail; 606 } 607 switch (type) { 608 case QCOW2_CLUSTER_COMPRESSED: 609 if (has_data_file(bs)) { 610 qcow2_signal_corruption(bs, true, -1, -1, "Compressed cluster " 611 "entry found in image with external data " 612 "file (L2 offset: %#" PRIx64 ", L2 index: " 613 "%#x)", l2_offset, l2_index); 614 ret = -EIO; 615 goto fail; 616 } 617 /* Compressed clusters can only be processed one by one */ 618 c = 1; 619 *cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK; 620 break; 621 case QCOW2_CLUSTER_ZERO_PLAIN: 622 case QCOW2_CLUSTER_UNALLOCATED: 623 /* how many empty clusters ? */ 624 c = count_contiguous_clusters_unallocated(bs, nb_clusters, 625 &l2_slice[l2_index], type); 626 *cluster_offset = 0; 627 break; 628 case QCOW2_CLUSTER_ZERO_ALLOC: 629 case QCOW2_CLUSTER_NORMAL: 630 /* how many allocated clusters ? */ 631 c = count_contiguous_clusters(bs, nb_clusters, s->cluster_size, 632 &l2_slice[l2_index], QCOW_OFLAG_ZERO); 633 *cluster_offset &= L2E_OFFSET_MASK; 634 if (offset_into_cluster(s, *cluster_offset)) { 635 qcow2_signal_corruption(bs, true, -1, -1, 636 "Cluster allocation offset %#" 637 PRIx64 " unaligned (L2 offset: %#" PRIx64 638 ", L2 index: %#x)", *cluster_offset, 639 l2_offset, l2_index); 640 ret = -EIO; 641 goto fail; 642 } 643 if (has_data_file(bs) && *cluster_offset != offset - offset_in_cluster) 644 { 645 qcow2_signal_corruption(bs, true, -1, -1, 646 "External data file host cluster offset %#" 647 PRIx64 " does not match guest cluster " 648 "offset: %#" PRIx64 649 ", L2 index: %#x)", *cluster_offset, 650 offset - offset_in_cluster, l2_index); 651 ret = -EIO; 652 goto fail; 653 } 654 break; 655 default: 656 abort(); 657 } 658 659 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 660 661 bytes_available = (int64_t)c * s->cluster_size; 662 663 out: 664 if (bytes_available > bytes_needed) { 665 bytes_available = bytes_needed; 666 } 667 668 /* bytes_available <= bytes_needed <= *bytes + offset_in_cluster; 669 * subtracting offset_in_cluster will therefore definitely yield something 670 * not exceeding UINT_MAX */ 671 assert(bytes_available - offset_in_cluster <= UINT_MAX); 672 *bytes = bytes_available - offset_in_cluster; 673 674 return type; 675 676 fail: 677 qcow2_cache_put(s->l2_table_cache, (void **)&l2_slice); 678 return ret; 679 } 680 681 /* 682 * get_cluster_table 683 * 684 * for a given disk offset, load (and allocate if needed) 685 * the appropriate slice of its l2 table. 686 * 687 * the cluster index in the l2 slice is given to the caller. 688 * 689 * Returns 0 on success, -errno in failure case 690 */ 691 static int get_cluster_table(BlockDriverState *bs, uint64_t offset, 692 uint64_t **new_l2_slice, 693 int *new_l2_index) 694 { 695 BDRVQcow2State *s = bs->opaque; 696 unsigned int l2_index; 697 uint64_t l1_index, l2_offset; 698 uint64_t *l2_slice = NULL; 699 int ret; 700 701 /* seek to the l2 offset in the l1 table */ 702 703 l1_index = offset_to_l1_index(s, offset); 704 if (l1_index >= s->l1_size) { 705 ret = qcow2_grow_l1_table(bs, l1_index + 1, false); 706 if (ret < 0) { 707 return ret; 708 } 709 } 710 711 assert(l1_index < s->l1_size); 712 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 713 if (offset_into_cluster(s, l2_offset)) { 714 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 715 " unaligned (L1 index: %#" PRIx64 ")", 716 l2_offset, l1_index); 717 return -EIO; 718 } 719 720 if (!(s->l1_table[l1_index] & QCOW_OFLAG_COPIED)) { 721 /* First allocate a new L2 table (and do COW if needed) */ 722 ret = l2_allocate(bs, l1_index); 723 if (ret < 0) { 724 return ret; 725 } 726 727 /* Then decrease the refcount of the old table */ 728 if (l2_offset) { 729 qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), 730 QCOW2_DISCARD_OTHER); 731 } 732 733 /* Get the offset of the newly-allocated l2 table */ 734 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 735 assert(offset_into_cluster(s, l2_offset) == 0); 736 } 737 738 /* load the l2 slice in memory */ 739 ret = l2_load(bs, offset, l2_offset, &l2_slice); 740 if (ret < 0) { 741 return ret; 742 } 743 744 /* find the cluster offset for the given disk offset */ 745 746 l2_index = offset_to_l2_slice_index(s, offset); 747 748 *new_l2_slice = l2_slice; 749 *new_l2_index = l2_index; 750 751 return 0; 752 } 753 754 /* 755 * alloc_compressed_cluster_offset 756 * 757 * For a given offset on the virtual disk, allocate a new compressed cluster 758 * and put the host offset of the cluster into *host_offset. If a cluster is 759 * already allocated at the offset, return an error. 760 * 761 * Return 0 on success and -errno in error cases 762 */ 763 int qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, 764 uint64_t offset, 765 int compressed_size, 766 uint64_t *host_offset) 767 { 768 BDRVQcow2State *s = bs->opaque; 769 int l2_index, ret; 770 uint64_t *l2_slice; 771 int64_t cluster_offset; 772 int nb_csectors; 773 774 if (has_data_file(bs)) { 775 return 0; 776 } 777 778 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 779 if (ret < 0) { 780 return ret; 781 } 782 783 /* Compression can't overwrite anything. Fail if the cluster was already 784 * allocated. */ 785 cluster_offset = be64_to_cpu(l2_slice[l2_index]); 786 if (cluster_offset & L2E_OFFSET_MASK) { 787 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 788 return -EIO; 789 } 790 791 cluster_offset = qcow2_alloc_bytes(bs, compressed_size); 792 if (cluster_offset < 0) { 793 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 794 return cluster_offset; 795 } 796 797 nb_csectors = 798 (cluster_offset + compressed_size - 1) / QCOW2_COMPRESSED_SECTOR_SIZE - 799 (cluster_offset / QCOW2_COMPRESSED_SECTOR_SIZE); 800 801 cluster_offset |= QCOW_OFLAG_COMPRESSED | 802 ((uint64_t)nb_csectors << s->csize_shift); 803 804 /* update L2 table */ 805 806 /* compressed clusters never have the copied flag */ 807 808 BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED); 809 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 810 l2_slice[l2_index] = cpu_to_be64(cluster_offset); 811 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 812 813 *host_offset = cluster_offset & s->cluster_offset_mask; 814 return 0; 815 } 816 817 static int perform_cow(BlockDriverState *bs, QCowL2Meta *m) 818 { 819 BDRVQcow2State *s = bs->opaque; 820 Qcow2COWRegion *start = &m->cow_start; 821 Qcow2COWRegion *end = &m->cow_end; 822 unsigned buffer_size; 823 unsigned data_bytes = end->offset - (start->offset + start->nb_bytes); 824 bool merge_reads; 825 uint8_t *start_buffer, *end_buffer; 826 QEMUIOVector qiov; 827 int ret; 828 829 assert(start->nb_bytes <= UINT_MAX - end->nb_bytes); 830 assert(start->nb_bytes + end->nb_bytes <= UINT_MAX - data_bytes); 831 assert(start->offset + start->nb_bytes <= end->offset); 832 833 if ((start->nb_bytes == 0 && end->nb_bytes == 0) || m->skip_cow) { 834 return 0; 835 } 836 837 /* If we have to read both the start and end COW regions and the 838 * middle region is not too large then perform just one read 839 * operation */ 840 merge_reads = start->nb_bytes && end->nb_bytes && data_bytes <= 16384; 841 if (merge_reads) { 842 buffer_size = start->nb_bytes + data_bytes + end->nb_bytes; 843 } else { 844 /* If we have to do two reads, add some padding in the middle 845 * if necessary to make sure that the end region is optimally 846 * aligned. */ 847 size_t align = bdrv_opt_mem_align(bs); 848 assert(align > 0 && align <= UINT_MAX); 849 assert(QEMU_ALIGN_UP(start->nb_bytes, align) <= 850 UINT_MAX - end->nb_bytes); 851 buffer_size = QEMU_ALIGN_UP(start->nb_bytes, align) + end->nb_bytes; 852 } 853 854 /* Reserve a buffer large enough to store all the data that we're 855 * going to read */ 856 start_buffer = qemu_try_blockalign(bs, buffer_size); 857 if (start_buffer == NULL) { 858 return -ENOMEM; 859 } 860 /* The part of the buffer where the end region is located */ 861 end_buffer = start_buffer + buffer_size - end->nb_bytes; 862 863 qemu_iovec_init(&qiov, 2 + (m->data_qiov ? 864 qemu_iovec_subvec_niov(m->data_qiov, 865 m->data_qiov_offset, 866 data_bytes) 867 : 0)); 868 869 qemu_co_mutex_unlock(&s->lock); 870 /* First we read the existing data from both COW regions. We 871 * either read the whole region in one go, or the start and end 872 * regions separately. */ 873 if (merge_reads) { 874 qemu_iovec_add(&qiov, start_buffer, buffer_size); 875 ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); 876 } else { 877 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 878 ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); 879 if (ret < 0) { 880 goto fail; 881 } 882 883 qemu_iovec_reset(&qiov); 884 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 885 ret = do_perform_cow_read(bs, m->offset, end->offset, &qiov); 886 } 887 if (ret < 0) { 888 goto fail; 889 } 890 891 /* Encrypt the data if necessary before writing it */ 892 if (bs->encrypted) { 893 if (!do_perform_cow_encrypt(bs, m->offset, m->alloc_offset, 894 start->offset, start_buffer, 895 start->nb_bytes) || 896 !do_perform_cow_encrypt(bs, m->offset, m->alloc_offset, 897 end->offset, end_buffer, end->nb_bytes)) { 898 ret = -EIO; 899 goto fail; 900 } 901 } 902 903 /* And now we can write everything. If we have the guest data we 904 * can write everything in one single operation */ 905 if (m->data_qiov) { 906 qemu_iovec_reset(&qiov); 907 if (start->nb_bytes) { 908 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 909 } 910 qemu_iovec_concat(&qiov, m->data_qiov, m->data_qiov_offset, data_bytes); 911 if (end->nb_bytes) { 912 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 913 } 914 /* NOTE: we have a write_aio blkdebug event here followed by 915 * a cow_write one in do_perform_cow_write(), but there's only 916 * one single I/O operation */ 917 BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); 918 ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); 919 } else { 920 /* If there's no guest data then write both COW regions separately */ 921 qemu_iovec_reset(&qiov); 922 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 923 ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); 924 if (ret < 0) { 925 goto fail; 926 } 927 928 qemu_iovec_reset(&qiov); 929 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 930 ret = do_perform_cow_write(bs, m->alloc_offset, end->offset, &qiov); 931 } 932 933 fail: 934 qemu_co_mutex_lock(&s->lock); 935 936 /* 937 * Before we update the L2 table to actually point to the new cluster, we 938 * need to be sure that the refcounts have been increased and COW was 939 * handled. 940 */ 941 if (ret == 0) { 942 qcow2_cache_depends_on_flush(s->l2_table_cache); 943 } 944 945 qemu_vfree(start_buffer); 946 qemu_iovec_destroy(&qiov); 947 return ret; 948 } 949 950 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) 951 { 952 BDRVQcow2State *s = bs->opaque; 953 int i, j = 0, l2_index, ret; 954 uint64_t *old_cluster, *l2_slice; 955 uint64_t cluster_offset = m->alloc_offset; 956 957 trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters); 958 assert(m->nb_clusters > 0); 959 960 old_cluster = g_try_new(uint64_t, m->nb_clusters); 961 if (old_cluster == NULL) { 962 ret = -ENOMEM; 963 goto err; 964 } 965 966 /* copy content of unmodified sectors */ 967 ret = perform_cow(bs, m); 968 if (ret < 0) { 969 goto err; 970 } 971 972 /* Update L2 table. */ 973 if (s->use_lazy_refcounts) { 974 qcow2_mark_dirty(bs); 975 } 976 if (qcow2_need_accurate_refcounts(s)) { 977 qcow2_cache_set_dependency(bs, s->l2_table_cache, 978 s->refcount_block_cache); 979 } 980 981 ret = get_cluster_table(bs, m->offset, &l2_slice, &l2_index); 982 if (ret < 0) { 983 goto err; 984 } 985 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 986 987 assert(l2_index + m->nb_clusters <= s->l2_slice_size); 988 for (i = 0; i < m->nb_clusters; i++) { 989 /* if two concurrent writes happen to the same unallocated cluster 990 * each write allocates separate cluster and writes data concurrently. 991 * The first one to complete updates l2 table with pointer to its 992 * cluster the second one has to do RMW (which is done above by 993 * perform_cow()), update l2 table with its cluster pointer and free 994 * old cluster. This is what this loop does */ 995 if (l2_slice[l2_index + i] != 0) { 996 old_cluster[j++] = l2_slice[l2_index + i]; 997 } 998 999 l2_slice[l2_index + i] = cpu_to_be64((cluster_offset + 1000 (i << s->cluster_bits)) | QCOW_OFLAG_COPIED); 1001 } 1002 1003 1004 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1005 1006 /* 1007 * If this was a COW, we need to decrease the refcount of the old cluster. 1008 * 1009 * Don't discard clusters that reach a refcount of 0 (e.g. compressed 1010 * clusters), the next write will reuse them anyway. 1011 */ 1012 if (!m->keep_old_clusters && j != 0) { 1013 for (i = 0; i < j; i++) { 1014 qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1, 1015 QCOW2_DISCARD_NEVER); 1016 } 1017 } 1018 1019 ret = 0; 1020 err: 1021 g_free(old_cluster); 1022 return ret; 1023 } 1024 1025 /** 1026 * Frees the allocated clusters because the request failed and they won't 1027 * actually be linked. 1028 */ 1029 void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m) 1030 { 1031 BDRVQcow2State *s = bs->opaque; 1032 qcow2_free_clusters(bs, m->alloc_offset, m->nb_clusters << s->cluster_bits, 1033 QCOW2_DISCARD_NEVER); 1034 } 1035 1036 /* 1037 * Returns the number of contiguous clusters that can be used for an allocating 1038 * write, but require COW to be performed (this includes yet unallocated space, 1039 * which must copy from the backing file) 1040 */ 1041 static int count_cow_clusters(BlockDriverState *bs, int nb_clusters, 1042 uint64_t *l2_slice, int l2_index) 1043 { 1044 int i; 1045 1046 for (i = 0; i < nb_clusters; i++) { 1047 uint64_t l2_entry = be64_to_cpu(l2_slice[l2_index + i]); 1048 QCow2ClusterType cluster_type = qcow2_get_cluster_type(bs, l2_entry); 1049 1050 switch(cluster_type) { 1051 case QCOW2_CLUSTER_NORMAL: 1052 if (l2_entry & QCOW_OFLAG_COPIED) { 1053 goto out; 1054 } 1055 break; 1056 case QCOW2_CLUSTER_UNALLOCATED: 1057 case QCOW2_CLUSTER_COMPRESSED: 1058 case QCOW2_CLUSTER_ZERO_PLAIN: 1059 case QCOW2_CLUSTER_ZERO_ALLOC: 1060 break; 1061 default: 1062 abort(); 1063 } 1064 } 1065 1066 out: 1067 assert(i <= nb_clusters); 1068 return i; 1069 } 1070 1071 /* 1072 * Check if there already is an AIO write request in flight which allocates 1073 * the same cluster. In this case we need to wait until the previous 1074 * request has completed and updated the L2 table accordingly. 1075 * 1076 * Returns: 1077 * 0 if there was no dependency. *cur_bytes indicates the number of 1078 * bytes from guest_offset that can be read before the next 1079 * dependency must be processed (or the request is complete) 1080 * 1081 * -EAGAIN if we had to wait for another request, previously gathered 1082 * information on cluster allocation may be invalid now. The caller 1083 * must start over anyway, so consider *cur_bytes undefined. 1084 */ 1085 static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset, 1086 uint64_t *cur_bytes, QCowL2Meta **m) 1087 { 1088 BDRVQcow2State *s = bs->opaque; 1089 QCowL2Meta *old_alloc; 1090 uint64_t bytes = *cur_bytes; 1091 1092 QLIST_FOREACH(old_alloc, &s->cluster_allocs, next_in_flight) { 1093 1094 uint64_t start = guest_offset; 1095 uint64_t end = start + bytes; 1096 uint64_t old_start = l2meta_cow_start(old_alloc); 1097 uint64_t old_end = l2meta_cow_end(old_alloc); 1098 1099 if (end <= old_start || start >= old_end) { 1100 /* No intersection */ 1101 } else { 1102 if (start < old_start) { 1103 /* Stop at the start of a running allocation */ 1104 bytes = old_start - start; 1105 } else { 1106 bytes = 0; 1107 } 1108 1109 /* Stop if already an l2meta exists. After yielding, it wouldn't 1110 * be valid any more, so we'd have to clean up the old L2Metas 1111 * and deal with requests depending on them before starting to 1112 * gather new ones. Not worth the trouble. */ 1113 if (bytes == 0 && *m) { 1114 *cur_bytes = 0; 1115 return 0; 1116 } 1117 1118 if (bytes == 0) { 1119 /* Wait for the dependency to complete. We need to recheck 1120 * the free/allocated clusters when we continue. */ 1121 qemu_co_queue_wait(&old_alloc->dependent_requests, &s->lock); 1122 return -EAGAIN; 1123 } 1124 } 1125 } 1126 1127 /* Make sure that existing clusters and new allocations are only used up to 1128 * the next dependency if we shortened the request above */ 1129 *cur_bytes = bytes; 1130 1131 return 0; 1132 } 1133 1134 /* 1135 * Checks how many already allocated clusters that don't require a copy on 1136 * write there are at the given guest_offset (up to *bytes). If *host_offset is 1137 * not INV_OFFSET, only physically contiguous clusters beginning at this host 1138 * offset are counted. 1139 * 1140 * Note that guest_offset may not be cluster aligned. In this case, the 1141 * returned *host_offset points to exact byte referenced by guest_offset and 1142 * therefore isn't cluster aligned as well. 1143 * 1144 * Returns: 1145 * 0: if no allocated clusters are available at the given offset. 1146 * *bytes is normally unchanged. It is set to 0 if the cluster 1147 * is allocated and doesn't need COW, but doesn't have the right 1148 * physical offset. 1149 * 1150 * 1: if allocated clusters that don't require a COW are available at 1151 * the requested offset. *bytes may have decreased and describes 1152 * the length of the area that can be written to. 1153 * 1154 * -errno: in error cases 1155 */ 1156 static int handle_copied(BlockDriverState *bs, uint64_t guest_offset, 1157 uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) 1158 { 1159 BDRVQcow2State *s = bs->opaque; 1160 int l2_index; 1161 uint64_t cluster_offset; 1162 uint64_t *l2_slice; 1163 uint64_t nb_clusters; 1164 unsigned int keep_clusters; 1165 int ret; 1166 1167 trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset, *host_offset, 1168 *bytes); 1169 1170 assert(*host_offset == INV_OFFSET || offset_into_cluster(s, guest_offset) 1171 == offset_into_cluster(s, *host_offset)); 1172 1173 /* 1174 * Calculate the number of clusters to look for. We stop at L2 slice 1175 * boundaries to keep things simple. 1176 */ 1177 nb_clusters = 1178 size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); 1179 1180 l2_index = offset_to_l2_slice_index(s, guest_offset); 1181 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1182 assert(nb_clusters <= INT_MAX); 1183 1184 /* Find L2 entry for the first involved cluster */ 1185 ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index); 1186 if (ret < 0) { 1187 return ret; 1188 } 1189 1190 cluster_offset = be64_to_cpu(l2_slice[l2_index]); 1191 1192 /* Check how many clusters are already allocated and don't need COW */ 1193 if (qcow2_get_cluster_type(bs, cluster_offset) == QCOW2_CLUSTER_NORMAL 1194 && (cluster_offset & QCOW_OFLAG_COPIED)) 1195 { 1196 /* If a specific host_offset is required, check it */ 1197 bool offset_matches = 1198 (cluster_offset & L2E_OFFSET_MASK) == *host_offset; 1199 1200 if (offset_into_cluster(s, cluster_offset & L2E_OFFSET_MASK)) { 1201 qcow2_signal_corruption(bs, true, -1, -1, "Data cluster offset " 1202 "%#llx unaligned (guest offset: %#" PRIx64 1203 ")", cluster_offset & L2E_OFFSET_MASK, 1204 guest_offset); 1205 ret = -EIO; 1206 goto out; 1207 } 1208 1209 if (*host_offset != INV_OFFSET && !offset_matches) { 1210 *bytes = 0; 1211 ret = 0; 1212 goto out; 1213 } 1214 1215 /* We keep all QCOW_OFLAG_COPIED clusters */ 1216 keep_clusters = 1217 count_contiguous_clusters(bs, nb_clusters, s->cluster_size, 1218 &l2_slice[l2_index], 1219 QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO); 1220 assert(keep_clusters <= nb_clusters); 1221 1222 *bytes = MIN(*bytes, 1223 keep_clusters * s->cluster_size 1224 - offset_into_cluster(s, guest_offset)); 1225 1226 ret = 1; 1227 } else { 1228 ret = 0; 1229 } 1230 1231 /* Cleanup */ 1232 out: 1233 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1234 1235 /* Only return a host offset if we actually made progress. Otherwise we 1236 * would make requirements for handle_alloc() that it can't fulfill */ 1237 if (ret > 0) { 1238 *host_offset = (cluster_offset & L2E_OFFSET_MASK) 1239 + offset_into_cluster(s, guest_offset); 1240 } 1241 1242 return ret; 1243 } 1244 1245 /* 1246 * Allocates new clusters for the given guest_offset. 1247 * 1248 * At most *nb_clusters are allocated, and on return *nb_clusters is updated to 1249 * contain the number of clusters that have been allocated and are contiguous 1250 * in the image file. 1251 * 1252 * If *host_offset is not INV_OFFSET, it specifies the offset in the image file 1253 * at which the new clusters must start. *nb_clusters can be 0 on return in 1254 * this case if the cluster at host_offset is already in use. If *host_offset 1255 * is INV_OFFSET, the clusters can be allocated anywhere in the image file. 1256 * 1257 * *host_offset is updated to contain the offset into the image file at which 1258 * the first allocated cluster starts. 1259 * 1260 * Return 0 on success and -errno in error cases. -EAGAIN means that the 1261 * function has been waiting for another request and the allocation must be 1262 * restarted, but the whole request should not be failed. 1263 */ 1264 static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset, 1265 uint64_t *host_offset, uint64_t *nb_clusters) 1266 { 1267 BDRVQcow2State *s = bs->opaque; 1268 1269 trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset, 1270 *host_offset, *nb_clusters); 1271 1272 if (has_data_file(bs)) { 1273 assert(*host_offset == INV_OFFSET || 1274 *host_offset == start_of_cluster(s, guest_offset)); 1275 *host_offset = start_of_cluster(s, guest_offset); 1276 return 0; 1277 } 1278 1279 /* Allocate new clusters */ 1280 trace_qcow2_cluster_alloc_phys(qemu_coroutine_self()); 1281 if (*host_offset == INV_OFFSET) { 1282 int64_t cluster_offset = 1283 qcow2_alloc_clusters(bs, *nb_clusters * s->cluster_size); 1284 if (cluster_offset < 0) { 1285 return cluster_offset; 1286 } 1287 *host_offset = cluster_offset; 1288 return 0; 1289 } else { 1290 int64_t ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters); 1291 if (ret < 0) { 1292 return ret; 1293 } 1294 *nb_clusters = ret; 1295 return 0; 1296 } 1297 } 1298 1299 /* 1300 * Allocates new clusters for an area that either is yet unallocated or needs a 1301 * copy on write. If *host_offset is not INV_OFFSET, clusters are only 1302 * allocated if the new allocation can match the specified host offset. 1303 * 1304 * Note that guest_offset may not be cluster aligned. In this case, the 1305 * returned *host_offset points to exact byte referenced by guest_offset and 1306 * therefore isn't cluster aligned as well. 1307 * 1308 * Returns: 1309 * 0: if no clusters could be allocated. *bytes is set to 0, 1310 * *host_offset is left unchanged. 1311 * 1312 * 1: if new clusters were allocated. *bytes may be decreased if the 1313 * new allocation doesn't cover all of the requested area. 1314 * *host_offset is updated to contain the host offset of the first 1315 * newly allocated cluster. 1316 * 1317 * -errno: in error cases 1318 */ 1319 static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset, 1320 uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) 1321 { 1322 BDRVQcow2State *s = bs->opaque; 1323 int l2_index; 1324 uint64_t *l2_slice; 1325 uint64_t entry; 1326 uint64_t nb_clusters; 1327 int ret; 1328 bool keep_old_clusters = false; 1329 1330 uint64_t alloc_cluster_offset = INV_OFFSET; 1331 1332 trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset, 1333 *bytes); 1334 assert(*bytes > 0); 1335 1336 /* 1337 * Calculate the number of clusters to look for. We stop at L2 slice 1338 * boundaries to keep things simple. 1339 */ 1340 nb_clusters = 1341 size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); 1342 1343 l2_index = offset_to_l2_slice_index(s, guest_offset); 1344 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1345 assert(nb_clusters <= INT_MAX); 1346 1347 /* Find L2 entry for the first involved cluster */ 1348 ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index); 1349 if (ret < 0) { 1350 return ret; 1351 } 1352 1353 entry = be64_to_cpu(l2_slice[l2_index]); 1354 1355 /* For the moment, overwrite compressed clusters one by one */ 1356 if (entry & QCOW_OFLAG_COMPRESSED) { 1357 nb_clusters = 1; 1358 } else { 1359 nb_clusters = count_cow_clusters(bs, nb_clusters, l2_slice, l2_index); 1360 } 1361 1362 /* This function is only called when there were no non-COW clusters, so if 1363 * we can't find any unallocated or COW clusters either, something is 1364 * wrong with our code. */ 1365 assert(nb_clusters > 0); 1366 1367 if (qcow2_get_cluster_type(bs, entry) == QCOW2_CLUSTER_ZERO_ALLOC && 1368 (entry & QCOW_OFLAG_COPIED) && 1369 (*host_offset == INV_OFFSET || 1370 start_of_cluster(s, *host_offset) == (entry & L2E_OFFSET_MASK))) 1371 { 1372 int preallocated_nb_clusters; 1373 1374 if (offset_into_cluster(s, entry & L2E_OFFSET_MASK)) { 1375 qcow2_signal_corruption(bs, true, -1, -1, "Preallocated zero " 1376 "cluster offset %#llx unaligned (guest " 1377 "offset: %#" PRIx64 ")", 1378 entry & L2E_OFFSET_MASK, guest_offset); 1379 ret = -EIO; 1380 goto fail; 1381 } 1382 1383 /* Try to reuse preallocated zero clusters; contiguous normal clusters 1384 * would be fine, too, but count_cow_clusters() above has limited 1385 * nb_clusters already to a range of COW clusters */ 1386 preallocated_nb_clusters = 1387 count_contiguous_clusters(bs, nb_clusters, s->cluster_size, 1388 &l2_slice[l2_index], QCOW_OFLAG_COPIED); 1389 assert(preallocated_nb_clusters > 0); 1390 1391 nb_clusters = preallocated_nb_clusters; 1392 alloc_cluster_offset = entry & L2E_OFFSET_MASK; 1393 1394 /* We want to reuse these clusters, so qcow2_alloc_cluster_link_l2() 1395 * should not free them. */ 1396 keep_old_clusters = true; 1397 } 1398 1399 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1400 1401 if (alloc_cluster_offset == INV_OFFSET) { 1402 /* Allocate, if necessary at a given offset in the image file */ 1403 alloc_cluster_offset = *host_offset == INV_OFFSET ? INV_OFFSET : 1404 start_of_cluster(s, *host_offset); 1405 ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset, 1406 &nb_clusters); 1407 if (ret < 0) { 1408 goto fail; 1409 } 1410 1411 /* Can't extend contiguous allocation */ 1412 if (nb_clusters == 0) { 1413 *bytes = 0; 1414 return 0; 1415 } 1416 1417 assert(alloc_cluster_offset != INV_OFFSET); 1418 } 1419 1420 /* 1421 * Save info needed for meta data update. 1422 * 1423 * requested_bytes: Number of bytes from the start of the first 1424 * newly allocated cluster to the end of the (possibly shortened 1425 * before) write request. 1426 * 1427 * avail_bytes: Number of bytes from the start of the first 1428 * newly allocated to the end of the last newly allocated cluster. 1429 * 1430 * nb_bytes: The number of bytes from the start of the first 1431 * newly allocated cluster to the end of the area that the write 1432 * request actually writes to (excluding COW at the end) 1433 */ 1434 uint64_t requested_bytes = *bytes + offset_into_cluster(s, guest_offset); 1435 int avail_bytes = MIN(INT_MAX, nb_clusters << s->cluster_bits); 1436 int nb_bytes = MIN(requested_bytes, avail_bytes); 1437 QCowL2Meta *old_m = *m; 1438 1439 *m = g_malloc0(sizeof(**m)); 1440 1441 **m = (QCowL2Meta) { 1442 .next = old_m, 1443 1444 .alloc_offset = alloc_cluster_offset, 1445 .offset = start_of_cluster(s, guest_offset), 1446 .nb_clusters = nb_clusters, 1447 1448 .keep_old_clusters = keep_old_clusters, 1449 1450 .cow_start = { 1451 .offset = 0, 1452 .nb_bytes = offset_into_cluster(s, guest_offset), 1453 }, 1454 .cow_end = { 1455 .offset = nb_bytes, 1456 .nb_bytes = avail_bytes - nb_bytes, 1457 }, 1458 }; 1459 qemu_co_queue_init(&(*m)->dependent_requests); 1460 QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight); 1461 1462 *host_offset = alloc_cluster_offset + offset_into_cluster(s, guest_offset); 1463 *bytes = MIN(*bytes, nb_bytes - offset_into_cluster(s, guest_offset)); 1464 assert(*bytes != 0); 1465 1466 return 1; 1467 1468 fail: 1469 if (*m && (*m)->nb_clusters > 0) { 1470 QLIST_REMOVE(*m, next_in_flight); 1471 } 1472 return ret; 1473 } 1474 1475 /* 1476 * alloc_cluster_offset 1477 * 1478 * For a given offset on the virtual disk, find the cluster offset in qcow2 1479 * file. If the offset is not found, allocate a new cluster. 1480 * 1481 * If the cluster was already allocated, m->nb_clusters is set to 0 and 1482 * other fields in m are meaningless. 1483 * 1484 * If the cluster is newly allocated, m->nb_clusters is set to the number of 1485 * contiguous clusters that have been allocated. In this case, the other 1486 * fields of m are valid and contain information about the first allocated 1487 * cluster. 1488 * 1489 * If the request conflicts with another write request in flight, the coroutine 1490 * is queued and will be reentered when the dependency has completed. 1491 * 1492 * Return 0 on success and -errno in error cases 1493 */ 1494 int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, 1495 unsigned int *bytes, uint64_t *host_offset, 1496 QCowL2Meta **m) 1497 { 1498 BDRVQcow2State *s = bs->opaque; 1499 uint64_t start, remaining; 1500 uint64_t cluster_offset; 1501 uint64_t cur_bytes; 1502 int ret; 1503 1504 trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, *bytes); 1505 1506 again: 1507 start = offset; 1508 remaining = *bytes; 1509 cluster_offset = INV_OFFSET; 1510 *host_offset = INV_OFFSET; 1511 cur_bytes = 0; 1512 *m = NULL; 1513 1514 while (true) { 1515 1516 if (*host_offset == INV_OFFSET && cluster_offset != INV_OFFSET) { 1517 *host_offset = start_of_cluster(s, cluster_offset); 1518 } 1519 1520 assert(remaining >= cur_bytes); 1521 1522 start += cur_bytes; 1523 remaining -= cur_bytes; 1524 1525 if (cluster_offset != INV_OFFSET) { 1526 cluster_offset += cur_bytes; 1527 } 1528 1529 if (remaining == 0) { 1530 break; 1531 } 1532 1533 cur_bytes = remaining; 1534 1535 /* 1536 * Now start gathering as many contiguous clusters as possible: 1537 * 1538 * 1. Check for overlaps with in-flight allocations 1539 * 1540 * a) Overlap not in the first cluster -> shorten this request and 1541 * let the caller handle the rest in its next loop iteration. 1542 * 1543 * b) Real overlaps of two requests. Yield and restart the search 1544 * for contiguous clusters (the situation could have changed 1545 * while we were sleeping) 1546 * 1547 * c) TODO: Request starts in the same cluster as the in-flight 1548 * allocation ends. Shorten the COW of the in-fight allocation, 1549 * set cluster_offset to write to the same cluster and set up 1550 * the right synchronisation between the in-flight request and 1551 * the new one. 1552 */ 1553 ret = handle_dependencies(bs, start, &cur_bytes, m); 1554 if (ret == -EAGAIN) { 1555 /* Currently handle_dependencies() doesn't yield if we already had 1556 * an allocation. If it did, we would have to clean up the L2Meta 1557 * structs before starting over. */ 1558 assert(*m == NULL); 1559 goto again; 1560 } else if (ret < 0) { 1561 return ret; 1562 } else if (cur_bytes == 0) { 1563 break; 1564 } else { 1565 /* handle_dependencies() may have decreased cur_bytes (shortened 1566 * the allocations below) so that the next dependency is processed 1567 * correctly during the next loop iteration. */ 1568 } 1569 1570 /* 1571 * 2. Count contiguous COPIED clusters. 1572 */ 1573 ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m); 1574 if (ret < 0) { 1575 return ret; 1576 } else if (ret) { 1577 continue; 1578 } else if (cur_bytes == 0) { 1579 break; 1580 } 1581 1582 /* 1583 * 3. If the request still hasn't completed, allocate new clusters, 1584 * considering any cluster_offset of steps 1c or 2. 1585 */ 1586 ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m); 1587 if (ret < 0) { 1588 return ret; 1589 } else if (ret) { 1590 continue; 1591 } else { 1592 assert(cur_bytes == 0); 1593 break; 1594 } 1595 } 1596 1597 *bytes -= remaining; 1598 assert(*bytes > 0); 1599 assert(*host_offset != INV_OFFSET); 1600 1601 return 0; 1602 } 1603 1604 /* 1605 * This discards as many clusters of nb_clusters as possible at once (i.e. 1606 * all clusters in the same L2 slice) and returns the number of discarded 1607 * clusters. 1608 */ 1609 static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, 1610 uint64_t nb_clusters, 1611 enum qcow2_discard_type type, bool full_discard) 1612 { 1613 BDRVQcow2State *s = bs->opaque; 1614 uint64_t *l2_slice; 1615 int l2_index; 1616 int ret; 1617 int i; 1618 1619 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 1620 if (ret < 0) { 1621 return ret; 1622 } 1623 1624 /* Limit nb_clusters to one L2 slice */ 1625 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1626 assert(nb_clusters <= INT_MAX); 1627 1628 for (i = 0; i < nb_clusters; i++) { 1629 uint64_t old_l2_entry; 1630 1631 old_l2_entry = be64_to_cpu(l2_slice[l2_index + i]); 1632 1633 /* 1634 * If full_discard is false, make sure that a discarded area reads back 1635 * as zeroes for v3 images (we cannot do it for v2 without actually 1636 * writing a zero-filled buffer). We can skip the operation if the 1637 * cluster is already marked as zero, or if it's unallocated and we 1638 * don't have a backing file. 1639 * 1640 * TODO We might want to use bdrv_block_status(bs) here, but we're 1641 * holding s->lock, so that doesn't work today. 1642 * 1643 * If full_discard is true, the sector should not read back as zeroes, 1644 * but rather fall through to the backing file. 1645 */ 1646 switch (qcow2_get_cluster_type(bs, old_l2_entry)) { 1647 case QCOW2_CLUSTER_UNALLOCATED: 1648 if (full_discard || !bs->backing) { 1649 continue; 1650 } 1651 break; 1652 1653 case QCOW2_CLUSTER_ZERO_PLAIN: 1654 if (!full_discard) { 1655 continue; 1656 } 1657 break; 1658 1659 case QCOW2_CLUSTER_ZERO_ALLOC: 1660 case QCOW2_CLUSTER_NORMAL: 1661 case QCOW2_CLUSTER_COMPRESSED: 1662 break; 1663 1664 default: 1665 abort(); 1666 } 1667 1668 /* First remove L2 entries */ 1669 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1670 if (!full_discard && s->qcow_version >= 3) { 1671 l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); 1672 } else { 1673 l2_slice[l2_index + i] = cpu_to_be64(0); 1674 } 1675 1676 /* Then decrease the refcount */ 1677 qcow2_free_any_clusters(bs, old_l2_entry, 1, type); 1678 } 1679 1680 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1681 1682 return nb_clusters; 1683 } 1684 1685 int qcow2_cluster_discard(BlockDriverState *bs, uint64_t offset, 1686 uint64_t bytes, enum qcow2_discard_type type, 1687 bool full_discard) 1688 { 1689 BDRVQcow2State *s = bs->opaque; 1690 uint64_t end_offset = offset + bytes; 1691 uint64_t nb_clusters; 1692 int64_t cleared; 1693 int ret; 1694 1695 /* Caller must pass aligned values, except at image end */ 1696 assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); 1697 assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || 1698 end_offset == bs->total_sectors << BDRV_SECTOR_BITS); 1699 1700 nb_clusters = size_to_clusters(s, bytes); 1701 1702 s->cache_discards = true; 1703 1704 /* Each L2 slice is handled by its own loop iteration */ 1705 while (nb_clusters > 0) { 1706 cleared = discard_in_l2_slice(bs, offset, nb_clusters, type, 1707 full_discard); 1708 if (cleared < 0) { 1709 ret = cleared; 1710 goto fail; 1711 } 1712 1713 nb_clusters -= cleared; 1714 offset += (cleared * s->cluster_size); 1715 } 1716 1717 ret = 0; 1718 fail: 1719 s->cache_discards = false; 1720 qcow2_process_discards(bs, ret); 1721 1722 return ret; 1723 } 1724 1725 /* 1726 * This zeroes as many clusters of nb_clusters as possible at once (i.e. 1727 * all clusters in the same L2 slice) and returns the number of zeroed 1728 * clusters. 1729 */ 1730 static int zero_in_l2_slice(BlockDriverState *bs, uint64_t offset, 1731 uint64_t nb_clusters, int flags) 1732 { 1733 BDRVQcow2State *s = bs->opaque; 1734 uint64_t *l2_slice; 1735 int l2_index; 1736 int ret; 1737 int i; 1738 bool unmap = !!(flags & BDRV_REQ_MAY_UNMAP); 1739 1740 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 1741 if (ret < 0) { 1742 return ret; 1743 } 1744 1745 /* Limit nb_clusters to one L2 slice */ 1746 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1747 assert(nb_clusters <= INT_MAX); 1748 1749 for (i = 0; i < nb_clusters; i++) { 1750 uint64_t old_offset; 1751 QCow2ClusterType cluster_type; 1752 1753 old_offset = be64_to_cpu(l2_slice[l2_index + i]); 1754 1755 /* 1756 * Minimize L2 changes if the cluster already reads back as 1757 * zeroes with correct allocation. 1758 */ 1759 cluster_type = qcow2_get_cluster_type(bs, old_offset); 1760 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN || 1761 (cluster_type == QCOW2_CLUSTER_ZERO_ALLOC && !unmap)) { 1762 continue; 1763 } 1764 1765 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1766 if (cluster_type == QCOW2_CLUSTER_COMPRESSED || unmap) { 1767 l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); 1768 qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); 1769 } else { 1770 l2_slice[l2_index + i] |= cpu_to_be64(QCOW_OFLAG_ZERO); 1771 } 1772 } 1773 1774 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1775 1776 return nb_clusters; 1777 } 1778 1779 int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset, 1780 uint64_t bytes, int flags) 1781 { 1782 BDRVQcow2State *s = bs->opaque; 1783 uint64_t end_offset = offset + bytes; 1784 uint64_t nb_clusters; 1785 int64_t cleared; 1786 int ret; 1787 1788 /* If we have to stay in sync with an external data file, zero out 1789 * s->data_file first. */ 1790 if (data_file_is_raw(bs)) { 1791 assert(has_data_file(bs)); 1792 ret = bdrv_co_pwrite_zeroes(s->data_file, offset, bytes, flags); 1793 if (ret < 0) { 1794 return ret; 1795 } 1796 } 1797 1798 /* Caller must pass aligned values, except at image end */ 1799 assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); 1800 assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || 1801 end_offset == bs->total_sectors << BDRV_SECTOR_BITS); 1802 1803 /* The zero flag is only supported by version 3 and newer */ 1804 if (s->qcow_version < 3) { 1805 return -ENOTSUP; 1806 } 1807 1808 /* Each L2 slice is handled by its own loop iteration */ 1809 nb_clusters = size_to_clusters(s, bytes); 1810 1811 s->cache_discards = true; 1812 1813 while (nb_clusters > 0) { 1814 cleared = zero_in_l2_slice(bs, offset, nb_clusters, flags); 1815 if (cleared < 0) { 1816 ret = cleared; 1817 goto fail; 1818 } 1819 1820 nb_clusters -= cleared; 1821 offset += (cleared * s->cluster_size); 1822 } 1823 1824 ret = 0; 1825 fail: 1826 s->cache_discards = false; 1827 qcow2_process_discards(bs, ret); 1828 1829 return ret; 1830 } 1831 1832 /* 1833 * Expands all zero clusters in a specific L1 table (or deallocates them, for 1834 * non-backed non-pre-allocated zero clusters). 1835 * 1836 * l1_entries and *visited_l1_entries are used to keep track of progress for 1837 * status_cb(). l1_entries contains the total number of L1 entries and 1838 * *visited_l1_entries counts all visited L1 entries. 1839 */ 1840 static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table, 1841 int l1_size, int64_t *visited_l1_entries, 1842 int64_t l1_entries, 1843 BlockDriverAmendStatusCB *status_cb, 1844 void *cb_opaque) 1845 { 1846 BDRVQcow2State *s = bs->opaque; 1847 bool is_active_l1 = (l1_table == s->l1_table); 1848 uint64_t *l2_slice = NULL; 1849 unsigned slice, slice_size2, n_slices; 1850 int ret; 1851 int i, j; 1852 1853 slice_size2 = s->l2_slice_size * sizeof(uint64_t); 1854 n_slices = s->cluster_size / slice_size2; 1855 1856 if (!is_active_l1) { 1857 /* inactive L2 tables require a buffer to be stored in when loading 1858 * them from disk */ 1859 l2_slice = qemu_try_blockalign(bs->file->bs, slice_size2); 1860 if (l2_slice == NULL) { 1861 return -ENOMEM; 1862 } 1863 } 1864 1865 for (i = 0; i < l1_size; i++) { 1866 uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK; 1867 uint64_t l2_refcount; 1868 1869 if (!l2_offset) { 1870 /* unallocated */ 1871 (*visited_l1_entries)++; 1872 if (status_cb) { 1873 status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); 1874 } 1875 continue; 1876 } 1877 1878 if (offset_into_cluster(s, l2_offset)) { 1879 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" 1880 PRIx64 " unaligned (L1 index: %#x)", 1881 l2_offset, i); 1882 ret = -EIO; 1883 goto fail; 1884 } 1885 1886 ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits, 1887 &l2_refcount); 1888 if (ret < 0) { 1889 goto fail; 1890 } 1891 1892 for (slice = 0; slice < n_slices; slice++) { 1893 uint64_t slice_offset = l2_offset + slice * slice_size2; 1894 bool l2_dirty = false; 1895 if (is_active_l1) { 1896 /* get active L2 tables from cache */ 1897 ret = qcow2_cache_get(bs, s->l2_table_cache, slice_offset, 1898 (void **)&l2_slice); 1899 } else { 1900 /* load inactive L2 tables from disk */ 1901 ret = bdrv_pread(bs->file, slice_offset, l2_slice, slice_size2); 1902 } 1903 if (ret < 0) { 1904 goto fail; 1905 } 1906 1907 for (j = 0; j < s->l2_slice_size; j++) { 1908 uint64_t l2_entry = be64_to_cpu(l2_slice[j]); 1909 int64_t offset = l2_entry & L2E_OFFSET_MASK; 1910 QCow2ClusterType cluster_type = 1911 qcow2_get_cluster_type(bs, l2_entry); 1912 1913 if (cluster_type != QCOW2_CLUSTER_ZERO_PLAIN && 1914 cluster_type != QCOW2_CLUSTER_ZERO_ALLOC) { 1915 continue; 1916 } 1917 1918 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1919 if (!bs->backing) { 1920 /* not backed; therefore we can simply deallocate the 1921 * cluster */ 1922 l2_slice[j] = 0; 1923 l2_dirty = true; 1924 continue; 1925 } 1926 1927 offset = qcow2_alloc_clusters(bs, s->cluster_size); 1928 if (offset < 0) { 1929 ret = offset; 1930 goto fail; 1931 } 1932 1933 if (l2_refcount > 1) { 1934 /* For shared L2 tables, set the refcount accordingly 1935 * (it is already 1 and needs to be l2_refcount) */ 1936 ret = qcow2_update_cluster_refcount( 1937 bs, offset >> s->cluster_bits, 1938 refcount_diff(1, l2_refcount), false, 1939 QCOW2_DISCARD_OTHER); 1940 if (ret < 0) { 1941 qcow2_free_clusters(bs, offset, s->cluster_size, 1942 QCOW2_DISCARD_OTHER); 1943 goto fail; 1944 } 1945 } 1946 } 1947 1948 if (offset_into_cluster(s, offset)) { 1949 int l2_index = slice * s->l2_slice_size + j; 1950 qcow2_signal_corruption( 1951 bs, true, -1, -1, 1952 "Cluster allocation offset " 1953 "%#" PRIx64 " unaligned (L2 offset: %#" 1954 PRIx64 ", L2 index: %#x)", offset, 1955 l2_offset, l2_index); 1956 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1957 qcow2_free_clusters(bs, offset, s->cluster_size, 1958 QCOW2_DISCARD_ALWAYS); 1959 } 1960 ret = -EIO; 1961 goto fail; 1962 } 1963 1964 ret = qcow2_pre_write_overlap_check(bs, 0, offset, 1965 s->cluster_size, true); 1966 if (ret < 0) { 1967 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1968 qcow2_free_clusters(bs, offset, s->cluster_size, 1969 QCOW2_DISCARD_ALWAYS); 1970 } 1971 goto fail; 1972 } 1973 1974 ret = bdrv_pwrite_zeroes(s->data_file, offset, 1975 s->cluster_size, 0); 1976 if (ret < 0) { 1977 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1978 qcow2_free_clusters(bs, offset, s->cluster_size, 1979 QCOW2_DISCARD_ALWAYS); 1980 } 1981 goto fail; 1982 } 1983 1984 if (l2_refcount == 1) { 1985 l2_slice[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED); 1986 } else { 1987 l2_slice[j] = cpu_to_be64(offset); 1988 } 1989 l2_dirty = true; 1990 } 1991 1992 if (is_active_l1) { 1993 if (l2_dirty) { 1994 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1995 qcow2_cache_depends_on_flush(s->l2_table_cache); 1996 } 1997 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1998 } else { 1999 if (l2_dirty) { 2000 ret = qcow2_pre_write_overlap_check( 2001 bs, QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2, 2002 slice_offset, slice_size2, false); 2003 if (ret < 0) { 2004 goto fail; 2005 } 2006 2007 ret = bdrv_pwrite(bs->file, slice_offset, 2008 l2_slice, slice_size2); 2009 if (ret < 0) { 2010 goto fail; 2011 } 2012 } 2013 } 2014 } 2015 2016 (*visited_l1_entries)++; 2017 if (status_cb) { 2018 status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); 2019 } 2020 } 2021 2022 ret = 0; 2023 2024 fail: 2025 if (l2_slice) { 2026 if (!is_active_l1) { 2027 qemu_vfree(l2_slice); 2028 } else { 2029 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 2030 } 2031 } 2032 return ret; 2033 } 2034 2035 /* 2036 * For backed images, expands all zero clusters on the image. For non-backed 2037 * images, deallocates all non-pre-allocated zero clusters (and claims the 2038 * allocation for pre-allocated ones). This is important for downgrading to a 2039 * qcow2 version which doesn't yet support metadata zero clusters. 2040 */ 2041 int qcow2_expand_zero_clusters(BlockDriverState *bs, 2042 BlockDriverAmendStatusCB *status_cb, 2043 void *cb_opaque) 2044 { 2045 BDRVQcow2State *s = bs->opaque; 2046 uint64_t *l1_table = NULL; 2047 int64_t l1_entries = 0, visited_l1_entries = 0; 2048 int ret; 2049 int i, j; 2050 2051 if (status_cb) { 2052 l1_entries = s->l1_size; 2053 for (i = 0; i < s->nb_snapshots; i++) { 2054 l1_entries += s->snapshots[i].l1_size; 2055 } 2056 } 2057 2058 ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size, 2059 &visited_l1_entries, l1_entries, 2060 status_cb, cb_opaque); 2061 if (ret < 0) { 2062 goto fail; 2063 } 2064 2065 /* Inactive L1 tables may point to active L2 tables - therefore it is 2066 * necessary to flush the L2 table cache before trying to access the L2 2067 * tables pointed to by inactive L1 entries (else we might try to expand 2068 * zero clusters that have already been expanded); furthermore, it is also 2069 * necessary to empty the L2 table cache, since it may contain tables which 2070 * are now going to be modified directly on disk, bypassing the cache. 2071 * qcow2_cache_empty() does both for us. */ 2072 ret = qcow2_cache_empty(bs, s->l2_table_cache); 2073 if (ret < 0) { 2074 goto fail; 2075 } 2076 2077 for (i = 0; i < s->nb_snapshots; i++) { 2078 int l1_size2; 2079 uint64_t *new_l1_table; 2080 Error *local_err = NULL; 2081 2082 ret = qcow2_validate_table(bs, s->snapshots[i].l1_table_offset, 2083 s->snapshots[i].l1_size, sizeof(uint64_t), 2084 QCOW_MAX_L1_SIZE, "Snapshot L1 table", 2085 &local_err); 2086 if (ret < 0) { 2087 error_report_err(local_err); 2088 goto fail; 2089 } 2090 2091 l1_size2 = s->snapshots[i].l1_size * sizeof(uint64_t); 2092 new_l1_table = g_try_realloc(l1_table, l1_size2); 2093 2094 if (!new_l1_table) { 2095 ret = -ENOMEM; 2096 goto fail; 2097 } 2098 2099 l1_table = new_l1_table; 2100 2101 ret = bdrv_pread(bs->file, s->snapshots[i].l1_table_offset, 2102 l1_table, l1_size2); 2103 if (ret < 0) { 2104 goto fail; 2105 } 2106 2107 for (j = 0; j < s->snapshots[i].l1_size; j++) { 2108 be64_to_cpus(&l1_table[j]); 2109 } 2110 2111 ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size, 2112 &visited_l1_entries, l1_entries, 2113 status_cb, cb_opaque); 2114 if (ret < 0) { 2115 goto fail; 2116 } 2117 } 2118 2119 ret = 0; 2120 2121 fail: 2122 g_free(l1_table); 2123 return ret; 2124 } 2125