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, new_l1_size2); 128 if (new_l1_table == NULL) { 129 return -ENOMEM; 130 } 131 memset(new_l1_table, 0, new_l1_size2); 132 133 if (s->l1_size) { 134 memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t)); 135 } 136 137 /* write new table (align to cluster) */ 138 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ALLOC_TABLE); 139 new_l1_table_offset = qcow2_alloc_clusters(bs, new_l1_size2); 140 if (new_l1_table_offset < 0) { 141 qemu_vfree(new_l1_table); 142 return new_l1_table_offset; 143 } 144 145 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 146 if (ret < 0) { 147 goto fail; 148 } 149 150 /* the L1 position has not yet been updated, so these clusters must 151 * indeed be completely free */ 152 ret = qcow2_pre_write_overlap_check(bs, 0, new_l1_table_offset, 153 new_l1_size2, false); 154 if (ret < 0) { 155 goto fail; 156 } 157 158 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_WRITE_TABLE); 159 for(i = 0; i < s->l1_size; i++) 160 new_l1_table[i] = cpu_to_be64(new_l1_table[i]); 161 ret = bdrv_pwrite_sync(bs->file, new_l1_table_offset, 162 new_l1_table, new_l1_size2); 163 if (ret < 0) 164 goto fail; 165 for(i = 0; i < s->l1_size; i++) 166 new_l1_table[i] = be64_to_cpu(new_l1_table[i]); 167 168 /* set new table */ 169 BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ACTIVATE_TABLE); 170 stl_be_p(data, new_l1_size); 171 stq_be_p(data + 4, new_l1_table_offset); 172 ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size), 173 data, sizeof(data)); 174 if (ret < 0) { 175 goto fail; 176 } 177 qemu_vfree(s->l1_table); 178 old_l1_table_offset = s->l1_table_offset; 179 s->l1_table_offset = new_l1_table_offset; 180 s->l1_table = new_l1_table; 181 old_l1_size = s->l1_size; 182 s->l1_size = new_l1_size; 183 qcow2_free_clusters(bs, old_l1_table_offset, old_l1_size * sizeof(uint64_t), 184 QCOW2_DISCARD_OTHER); 185 return 0; 186 fail: 187 qemu_vfree(new_l1_table); 188 qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2, 189 QCOW2_DISCARD_OTHER); 190 return ret; 191 } 192 193 /* 194 * l2_load 195 * 196 * @bs: The BlockDriverState 197 * @offset: A guest offset, used to calculate what slice of the L2 198 * table to load. 199 * @l2_offset: Offset to the L2 table in the image file. 200 * @l2_slice: Location to store the pointer to the L2 slice. 201 * 202 * Loads a L2 slice into memory (L2 slices are the parts of L2 tables 203 * that are loaded by the qcow2 cache). If the slice is in the cache, 204 * the cache is used; otherwise the L2 slice is loaded from the image 205 * file. 206 */ 207 static int l2_load(BlockDriverState *bs, uint64_t offset, 208 uint64_t l2_offset, uint64_t **l2_slice) 209 { 210 BDRVQcow2State *s = bs->opaque; 211 int start_of_slice = sizeof(uint64_t) * 212 (offset_to_l2_index(s, offset) - offset_to_l2_slice_index(s, offset)); 213 214 return qcow2_cache_get(bs, s->l2_table_cache, l2_offset + start_of_slice, 215 (void **)l2_slice); 216 } 217 218 /* 219 * Writes an L1 entry to disk (note that depending on the alignment 220 * requirements this function may write more that just one entry in 221 * order to prevent bdrv_pwrite from performing a read-modify-write) 222 */ 223 int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index) 224 { 225 BDRVQcow2State *s = bs->opaque; 226 int l1_start_index; 227 int i, ret; 228 int bufsize = MAX(sizeof(uint64_t), 229 MIN(bs->file->bs->bl.request_alignment, s->cluster_size)); 230 int nentries = bufsize / sizeof(uint64_t); 231 g_autofree uint64_t *buf = g_try_new0(uint64_t, nentries); 232 233 if (buf == NULL) { 234 return -ENOMEM; 235 } 236 237 l1_start_index = QEMU_ALIGN_DOWN(l1_index, nentries); 238 for (i = 0; i < MIN(nentries, s->l1_size - l1_start_index); i++) { 239 buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]); 240 } 241 242 ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1, 243 s->l1_table_offset + 8 * l1_start_index, bufsize, false); 244 if (ret < 0) { 245 return ret; 246 } 247 248 BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE); 249 ret = bdrv_pwrite_sync(bs->file, 250 s->l1_table_offset + 8 * l1_start_index, 251 buf, bufsize); 252 if (ret < 0) { 253 return ret; 254 } 255 256 return 0; 257 } 258 259 /* 260 * l2_allocate 261 * 262 * Allocate a new l2 entry in the file. If l1_index points to an already 263 * used entry in the L2 table (i.e. we are doing a copy on write for the L2 264 * table) copy the contents of the old L2 table into the newly allocated one. 265 * Otherwise the new table is initialized with zeros. 266 * 267 */ 268 269 static int l2_allocate(BlockDriverState *bs, int l1_index) 270 { 271 BDRVQcow2State *s = bs->opaque; 272 uint64_t old_l2_offset; 273 uint64_t *l2_slice = NULL; 274 unsigned slice, slice_size2, n_slices; 275 int64_t l2_offset; 276 int ret; 277 278 old_l2_offset = s->l1_table[l1_index]; 279 280 trace_qcow2_l2_allocate(bs, l1_index); 281 282 /* allocate a new l2 entry */ 283 284 l2_offset = qcow2_alloc_clusters(bs, s->l2_size * sizeof(uint64_t)); 285 if (l2_offset < 0) { 286 ret = l2_offset; 287 goto fail; 288 } 289 290 /* The offset must fit in the offset field of the L1 table entry */ 291 assert((l2_offset & L1E_OFFSET_MASK) == l2_offset); 292 293 /* If we're allocating the table at offset 0 then something is wrong */ 294 if (l2_offset == 0) { 295 qcow2_signal_corruption(bs, true, -1, -1, "Preventing invalid " 296 "allocation of L2 table at offset 0"); 297 ret = -EIO; 298 goto fail; 299 } 300 301 ret = qcow2_cache_flush(bs, s->refcount_block_cache); 302 if (ret < 0) { 303 goto fail; 304 } 305 306 /* allocate a new entry in the l2 cache */ 307 308 slice_size2 = s->l2_slice_size * sizeof(uint64_t); 309 n_slices = s->cluster_size / slice_size2; 310 311 trace_qcow2_l2_allocate_get_empty(bs, l1_index); 312 for (slice = 0; slice < n_slices; slice++) { 313 ret = qcow2_cache_get_empty(bs, s->l2_table_cache, 314 l2_offset + slice * slice_size2, 315 (void **) &l2_slice); 316 if (ret < 0) { 317 goto fail; 318 } 319 320 if ((old_l2_offset & L1E_OFFSET_MASK) == 0) { 321 /* if there was no old l2 table, clear the new slice */ 322 memset(l2_slice, 0, slice_size2); 323 } else { 324 uint64_t *old_slice; 325 uint64_t old_l2_slice_offset = 326 (old_l2_offset & L1E_OFFSET_MASK) + slice * slice_size2; 327 328 /* if there was an old l2 table, read a slice from the disk */ 329 BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ); 330 ret = qcow2_cache_get(bs, s->l2_table_cache, old_l2_slice_offset, 331 (void **) &old_slice); 332 if (ret < 0) { 333 goto fail; 334 } 335 336 memcpy(l2_slice, old_slice, slice_size2); 337 338 qcow2_cache_put(s->l2_table_cache, (void **) &old_slice); 339 } 340 341 /* write the l2 slice to the file */ 342 BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_WRITE); 343 344 trace_qcow2_l2_allocate_write_l2(bs, l1_index); 345 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 346 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 347 } 348 349 ret = qcow2_cache_flush(bs, s->l2_table_cache); 350 if (ret < 0) { 351 goto fail; 352 } 353 354 /* update the L1 entry */ 355 trace_qcow2_l2_allocate_write_l1(bs, l1_index); 356 s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED; 357 ret = qcow2_write_l1_entry(bs, l1_index); 358 if (ret < 0) { 359 goto fail; 360 } 361 362 trace_qcow2_l2_allocate_done(bs, l1_index, 0); 363 return 0; 364 365 fail: 366 trace_qcow2_l2_allocate_done(bs, l1_index, ret); 367 if (l2_slice != NULL) { 368 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 369 } 370 s->l1_table[l1_index] = old_l2_offset; 371 if (l2_offset > 0) { 372 qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), 373 QCOW2_DISCARD_ALWAYS); 374 } 375 return ret; 376 } 377 378 /* 379 * Checks how many clusters in a given L2 slice are contiguous in the image 380 * file. As soon as one of the flags in the bitmask stop_flags changes compared 381 * to the first cluster, the search is stopped and the cluster is not counted 382 * as contiguous. (This allows it, for example, to stop at the first compressed 383 * cluster which may require a different handling) 384 */ 385 static int count_contiguous_clusters(BlockDriverState *bs, int nb_clusters, 386 int cluster_size, uint64_t *l2_slice, uint64_t stop_flags) 387 { 388 int i; 389 QCow2ClusterType first_cluster_type; 390 uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED; 391 uint64_t first_entry = be64_to_cpu(l2_slice[0]); 392 uint64_t offset = first_entry & mask; 393 394 first_cluster_type = qcow2_get_cluster_type(bs, first_entry); 395 if (first_cluster_type == QCOW2_CLUSTER_UNALLOCATED) { 396 return 0; 397 } 398 399 /* must be allocated */ 400 assert(first_cluster_type == QCOW2_CLUSTER_NORMAL || 401 first_cluster_type == QCOW2_CLUSTER_ZERO_ALLOC); 402 403 for (i = 0; i < nb_clusters; i++) { 404 uint64_t l2_entry = be64_to_cpu(l2_slice[i]) & mask; 405 if (offset + (uint64_t) i * cluster_size != l2_entry) { 406 break; 407 } 408 } 409 410 return i; 411 } 412 413 /* 414 * Checks how many consecutive unallocated clusters in a given L2 415 * slice have the same cluster type. 416 */ 417 static int count_contiguous_clusters_unallocated(BlockDriverState *bs, 418 int nb_clusters, 419 uint64_t *l2_slice, 420 QCow2ClusterType wanted_type) 421 { 422 int i; 423 424 assert(wanted_type == QCOW2_CLUSTER_ZERO_PLAIN || 425 wanted_type == QCOW2_CLUSTER_UNALLOCATED); 426 for (i = 0; i < nb_clusters; i++) { 427 uint64_t entry = be64_to_cpu(l2_slice[i]); 428 QCow2ClusterType type = qcow2_get_cluster_type(bs, entry); 429 430 if (type != wanted_type) { 431 break; 432 } 433 } 434 435 return i; 436 } 437 438 static int coroutine_fn do_perform_cow_read(BlockDriverState *bs, 439 uint64_t src_cluster_offset, 440 unsigned offset_in_cluster, 441 QEMUIOVector *qiov) 442 { 443 int ret; 444 445 if (qiov->size == 0) { 446 return 0; 447 } 448 449 BLKDBG_EVENT(bs->file, BLKDBG_COW_READ); 450 451 if (!bs->drv) { 452 return -ENOMEDIUM; 453 } 454 455 /* Call .bdrv_co_readv() directly instead of using the public block-layer 456 * interface. This avoids double I/O throttling and request tracking, 457 * which can lead to deadlock when block layer copy-on-read is enabled. 458 */ 459 ret = bs->drv->bdrv_co_preadv_part(bs, 460 src_cluster_offset + offset_in_cluster, 461 qiov->size, qiov, 0, 0); 462 if (ret < 0) { 463 return ret; 464 } 465 466 return 0; 467 } 468 469 static int coroutine_fn do_perform_cow_write(BlockDriverState *bs, 470 uint64_t cluster_offset, 471 unsigned offset_in_cluster, 472 QEMUIOVector *qiov) 473 { 474 BDRVQcow2State *s = bs->opaque; 475 int ret; 476 477 if (qiov->size == 0) { 478 return 0; 479 } 480 481 ret = qcow2_pre_write_overlap_check(bs, 0, 482 cluster_offset + offset_in_cluster, qiov->size, true); 483 if (ret < 0) { 484 return ret; 485 } 486 487 BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE); 488 ret = bdrv_co_pwritev(s->data_file, cluster_offset + offset_in_cluster, 489 qiov->size, qiov, 0); 490 if (ret < 0) { 491 return ret; 492 } 493 494 return 0; 495 } 496 497 498 /* 499 * get_cluster_offset 500 * 501 * For a given offset of the virtual disk, find the cluster type and offset in 502 * the qcow2 file. The offset is stored in *cluster_offset. 503 * 504 * On entry, *bytes is the maximum number of contiguous bytes starting at 505 * offset that we are interested in. 506 * 507 * On exit, *bytes is the number of bytes starting at offset that have the same 508 * cluster type and (if applicable) are stored contiguously in the image file. 509 * Compressed clusters are always returned one by one. 510 * 511 * Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error 512 * cases. 513 */ 514 int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset, 515 unsigned int *bytes, uint64_t *cluster_offset) 516 { 517 BDRVQcow2State *s = bs->opaque; 518 unsigned int l2_index; 519 uint64_t l1_index, l2_offset, *l2_slice; 520 int c; 521 unsigned int offset_in_cluster; 522 uint64_t bytes_available, bytes_needed, nb_clusters; 523 QCow2ClusterType type; 524 int ret; 525 526 offset_in_cluster = offset_into_cluster(s, offset); 527 bytes_needed = (uint64_t) *bytes + offset_in_cluster; 528 529 /* compute how many bytes there are between the start of the cluster 530 * containing offset and the end of the l2 slice that contains 531 * the entry pointing to it */ 532 bytes_available = 533 ((uint64_t) (s->l2_slice_size - offset_to_l2_slice_index(s, offset))) 534 << s->cluster_bits; 535 536 if (bytes_needed > bytes_available) { 537 bytes_needed = bytes_available; 538 } 539 540 *cluster_offset = 0; 541 542 /* seek to the l2 offset in the l1 table */ 543 544 l1_index = offset_to_l1_index(s, offset); 545 if (l1_index >= s->l1_size) { 546 type = QCOW2_CLUSTER_UNALLOCATED; 547 goto out; 548 } 549 550 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 551 if (!l2_offset) { 552 type = QCOW2_CLUSTER_UNALLOCATED; 553 goto out; 554 } 555 556 if (offset_into_cluster(s, l2_offset)) { 557 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 558 " unaligned (L1 index: %#" PRIx64 ")", 559 l2_offset, l1_index); 560 return -EIO; 561 } 562 563 /* load the l2 slice in memory */ 564 565 ret = l2_load(bs, offset, l2_offset, &l2_slice); 566 if (ret < 0) { 567 return ret; 568 } 569 570 /* find the cluster offset for the given disk offset */ 571 572 l2_index = offset_to_l2_slice_index(s, offset); 573 *cluster_offset = be64_to_cpu(l2_slice[l2_index]); 574 575 nb_clusters = size_to_clusters(s, bytes_needed); 576 /* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned 577 * integers; the minimum cluster size is 512, so this assertion is always 578 * true */ 579 assert(nb_clusters <= INT_MAX); 580 581 type = qcow2_get_cluster_type(bs, *cluster_offset); 582 if (s->qcow_version < 3 && (type == QCOW2_CLUSTER_ZERO_PLAIN || 583 type == QCOW2_CLUSTER_ZERO_ALLOC)) { 584 qcow2_signal_corruption(bs, true, -1, -1, "Zero cluster entry found" 585 " in pre-v3 image (L2 offset: %#" PRIx64 586 ", L2 index: %#x)", l2_offset, l2_index); 587 ret = -EIO; 588 goto fail; 589 } 590 switch (type) { 591 case QCOW2_CLUSTER_COMPRESSED: 592 if (has_data_file(bs)) { 593 qcow2_signal_corruption(bs, true, -1, -1, "Compressed cluster " 594 "entry found in image with external data " 595 "file (L2 offset: %#" PRIx64 ", L2 index: " 596 "%#x)", l2_offset, l2_index); 597 ret = -EIO; 598 goto fail; 599 } 600 /* Compressed clusters can only be processed one by one */ 601 c = 1; 602 *cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK; 603 break; 604 case QCOW2_CLUSTER_ZERO_PLAIN: 605 case QCOW2_CLUSTER_UNALLOCATED: 606 /* how many empty clusters ? */ 607 c = count_contiguous_clusters_unallocated(bs, nb_clusters, 608 &l2_slice[l2_index], type); 609 *cluster_offset = 0; 610 break; 611 case QCOW2_CLUSTER_ZERO_ALLOC: 612 case QCOW2_CLUSTER_NORMAL: 613 /* how many allocated clusters ? */ 614 c = count_contiguous_clusters(bs, nb_clusters, s->cluster_size, 615 &l2_slice[l2_index], QCOW_OFLAG_ZERO); 616 *cluster_offset &= L2E_OFFSET_MASK; 617 if (offset_into_cluster(s, *cluster_offset)) { 618 qcow2_signal_corruption(bs, true, -1, -1, 619 "Cluster allocation offset %#" 620 PRIx64 " unaligned (L2 offset: %#" PRIx64 621 ", L2 index: %#x)", *cluster_offset, 622 l2_offset, l2_index); 623 ret = -EIO; 624 goto fail; 625 } 626 if (has_data_file(bs) && *cluster_offset != offset - offset_in_cluster) 627 { 628 qcow2_signal_corruption(bs, true, -1, -1, 629 "External data file host cluster offset %#" 630 PRIx64 " does not match guest cluster " 631 "offset: %#" PRIx64 632 ", L2 index: %#x)", *cluster_offset, 633 offset - offset_in_cluster, l2_index); 634 ret = -EIO; 635 goto fail; 636 } 637 break; 638 default: 639 abort(); 640 } 641 642 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 643 644 bytes_available = (int64_t)c * s->cluster_size; 645 646 out: 647 if (bytes_available > bytes_needed) { 648 bytes_available = bytes_needed; 649 } 650 651 /* bytes_available <= bytes_needed <= *bytes + offset_in_cluster; 652 * subtracting offset_in_cluster will therefore definitely yield something 653 * not exceeding UINT_MAX */ 654 assert(bytes_available - offset_in_cluster <= UINT_MAX); 655 *bytes = bytes_available - offset_in_cluster; 656 657 return type; 658 659 fail: 660 qcow2_cache_put(s->l2_table_cache, (void **)&l2_slice); 661 return ret; 662 } 663 664 /* 665 * get_cluster_table 666 * 667 * for a given disk offset, load (and allocate if needed) 668 * the appropriate slice of its l2 table. 669 * 670 * the cluster index in the l2 slice is given to the caller. 671 * 672 * Returns 0 on success, -errno in failure case 673 */ 674 static int get_cluster_table(BlockDriverState *bs, uint64_t offset, 675 uint64_t **new_l2_slice, 676 int *new_l2_index) 677 { 678 BDRVQcow2State *s = bs->opaque; 679 unsigned int l2_index; 680 uint64_t l1_index, l2_offset; 681 uint64_t *l2_slice = NULL; 682 int ret; 683 684 /* seek to the l2 offset in the l1 table */ 685 686 l1_index = offset_to_l1_index(s, offset); 687 if (l1_index >= s->l1_size) { 688 ret = qcow2_grow_l1_table(bs, l1_index + 1, false); 689 if (ret < 0) { 690 return ret; 691 } 692 } 693 694 assert(l1_index < s->l1_size); 695 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 696 if (offset_into_cluster(s, l2_offset)) { 697 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" PRIx64 698 " unaligned (L1 index: %#" PRIx64 ")", 699 l2_offset, l1_index); 700 return -EIO; 701 } 702 703 if (!(s->l1_table[l1_index] & QCOW_OFLAG_COPIED)) { 704 /* First allocate a new L2 table (and do COW if needed) */ 705 ret = l2_allocate(bs, l1_index); 706 if (ret < 0) { 707 return ret; 708 } 709 710 /* Then decrease the refcount of the old table */ 711 if (l2_offset) { 712 qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), 713 QCOW2_DISCARD_OTHER); 714 } 715 716 /* Get the offset of the newly-allocated l2 table */ 717 l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; 718 assert(offset_into_cluster(s, l2_offset) == 0); 719 } 720 721 /* load the l2 slice in memory */ 722 ret = l2_load(bs, offset, l2_offset, &l2_slice); 723 if (ret < 0) { 724 return ret; 725 } 726 727 /* find the cluster offset for the given disk offset */ 728 729 l2_index = offset_to_l2_slice_index(s, offset); 730 731 *new_l2_slice = l2_slice; 732 *new_l2_index = l2_index; 733 734 return 0; 735 } 736 737 /* 738 * alloc_compressed_cluster_offset 739 * 740 * For a given offset on the virtual disk, allocate a new compressed cluster 741 * and put the host offset of the cluster into *host_offset. If a cluster is 742 * already allocated at the offset, return an error. 743 * 744 * Return 0 on success and -errno in error cases 745 */ 746 int qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, 747 uint64_t offset, 748 int compressed_size, 749 uint64_t *host_offset) 750 { 751 BDRVQcow2State *s = bs->opaque; 752 int l2_index, ret; 753 uint64_t *l2_slice; 754 int64_t cluster_offset; 755 int nb_csectors; 756 757 if (has_data_file(bs)) { 758 return 0; 759 } 760 761 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 762 if (ret < 0) { 763 return ret; 764 } 765 766 /* Compression can't overwrite anything. Fail if the cluster was already 767 * allocated. */ 768 cluster_offset = be64_to_cpu(l2_slice[l2_index]); 769 if (cluster_offset & L2E_OFFSET_MASK) { 770 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 771 return -EIO; 772 } 773 774 cluster_offset = qcow2_alloc_bytes(bs, compressed_size); 775 if (cluster_offset < 0) { 776 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 777 return cluster_offset; 778 } 779 780 nb_csectors = 781 (cluster_offset + compressed_size - 1) / QCOW2_COMPRESSED_SECTOR_SIZE - 782 (cluster_offset / QCOW2_COMPRESSED_SECTOR_SIZE); 783 784 /* The offset and size must fit in their fields of the L2 table entry */ 785 assert((cluster_offset & s->cluster_offset_mask) == cluster_offset); 786 assert((nb_csectors & s->csize_mask) == nb_csectors); 787 788 cluster_offset |= QCOW_OFLAG_COMPRESSED | 789 ((uint64_t)nb_csectors << s->csize_shift); 790 791 /* update L2 table */ 792 793 /* compressed clusters never have the copied flag */ 794 795 BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED); 796 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 797 l2_slice[l2_index] = cpu_to_be64(cluster_offset); 798 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 799 800 *host_offset = cluster_offset & s->cluster_offset_mask; 801 return 0; 802 } 803 804 static int perform_cow(BlockDriverState *bs, QCowL2Meta *m) 805 { 806 BDRVQcow2State *s = bs->opaque; 807 Qcow2COWRegion *start = &m->cow_start; 808 Qcow2COWRegion *end = &m->cow_end; 809 unsigned buffer_size; 810 unsigned data_bytes = end->offset - (start->offset + start->nb_bytes); 811 bool merge_reads; 812 uint8_t *start_buffer, *end_buffer; 813 QEMUIOVector qiov; 814 int ret; 815 816 assert(start->nb_bytes <= UINT_MAX - end->nb_bytes); 817 assert(start->nb_bytes + end->nb_bytes <= UINT_MAX - data_bytes); 818 assert(start->offset + start->nb_bytes <= end->offset); 819 820 if ((start->nb_bytes == 0 && end->nb_bytes == 0) || m->skip_cow) { 821 return 0; 822 } 823 824 /* If we have to read both the start and end COW regions and the 825 * middle region is not too large then perform just one read 826 * operation */ 827 merge_reads = start->nb_bytes && end->nb_bytes && data_bytes <= 16384; 828 if (merge_reads) { 829 buffer_size = start->nb_bytes + data_bytes + end->nb_bytes; 830 } else { 831 /* If we have to do two reads, add some padding in the middle 832 * if necessary to make sure that the end region is optimally 833 * aligned. */ 834 size_t align = bdrv_opt_mem_align(bs); 835 assert(align > 0 && align <= UINT_MAX); 836 assert(QEMU_ALIGN_UP(start->nb_bytes, align) <= 837 UINT_MAX - end->nb_bytes); 838 buffer_size = QEMU_ALIGN_UP(start->nb_bytes, align) + end->nb_bytes; 839 } 840 841 /* Reserve a buffer large enough to store all the data that we're 842 * going to read */ 843 start_buffer = qemu_try_blockalign(bs, buffer_size); 844 if (start_buffer == NULL) { 845 return -ENOMEM; 846 } 847 /* The part of the buffer where the end region is located */ 848 end_buffer = start_buffer + buffer_size - end->nb_bytes; 849 850 qemu_iovec_init(&qiov, 2 + (m->data_qiov ? 851 qemu_iovec_subvec_niov(m->data_qiov, 852 m->data_qiov_offset, 853 data_bytes) 854 : 0)); 855 856 qemu_co_mutex_unlock(&s->lock); 857 /* First we read the existing data from both COW regions. We 858 * either read the whole region in one go, or the start and end 859 * regions separately. */ 860 if (merge_reads) { 861 qemu_iovec_add(&qiov, start_buffer, buffer_size); 862 ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); 863 } else { 864 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 865 ret = do_perform_cow_read(bs, m->offset, start->offset, &qiov); 866 if (ret < 0) { 867 goto fail; 868 } 869 870 qemu_iovec_reset(&qiov); 871 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 872 ret = do_perform_cow_read(bs, m->offset, end->offset, &qiov); 873 } 874 if (ret < 0) { 875 goto fail; 876 } 877 878 /* Encrypt the data if necessary before writing it */ 879 if (bs->encrypted) { 880 ret = qcow2_co_encrypt(bs, 881 m->alloc_offset + start->offset, 882 m->offset + start->offset, 883 start_buffer, start->nb_bytes); 884 if (ret < 0) { 885 goto fail; 886 } 887 888 ret = qcow2_co_encrypt(bs, 889 m->alloc_offset + end->offset, 890 m->offset + end->offset, 891 end_buffer, end->nb_bytes); 892 if (ret < 0) { 893 goto fail; 894 } 895 } 896 897 /* And now we can write everything. If we have the guest data we 898 * can write everything in one single operation */ 899 if (m->data_qiov) { 900 qemu_iovec_reset(&qiov); 901 if (start->nb_bytes) { 902 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 903 } 904 qemu_iovec_concat(&qiov, m->data_qiov, m->data_qiov_offset, data_bytes); 905 if (end->nb_bytes) { 906 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 907 } 908 /* NOTE: we have a write_aio blkdebug event here followed by 909 * a cow_write one in do_perform_cow_write(), but there's only 910 * one single I/O operation */ 911 BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); 912 ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); 913 } else { 914 /* If there's no guest data then write both COW regions separately */ 915 qemu_iovec_reset(&qiov); 916 qemu_iovec_add(&qiov, start_buffer, start->nb_bytes); 917 ret = do_perform_cow_write(bs, m->alloc_offset, start->offset, &qiov); 918 if (ret < 0) { 919 goto fail; 920 } 921 922 qemu_iovec_reset(&qiov); 923 qemu_iovec_add(&qiov, end_buffer, end->nb_bytes); 924 ret = do_perform_cow_write(bs, m->alloc_offset, end->offset, &qiov); 925 } 926 927 fail: 928 qemu_co_mutex_lock(&s->lock); 929 930 /* 931 * Before we update the L2 table to actually point to the new cluster, we 932 * need to be sure that the refcounts have been increased and COW was 933 * handled. 934 */ 935 if (ret == 0) { 936 qcow2_cache_depends_on_flush(s->l2_table_cache); 937 } 938 939 qemu_vfree(start_buffer); 940 qemu_iovec_destroy(&qiov); 941 return ret; 942 } 943 944 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) 945 { 946 BDRVQcow2State *s = bs->opaque; 947 int i, j = 0, l2_index, ret; 948 uint64_t *old_cluster, *l2_slice; 949 uint64_t cluster_offset = m->alloc_offset; 950 951 trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters); 952 assert(m->nb_clusters > 0); 953 954 old_cluster = g_try_new(uint64_t, m->nb_clusters); 955 if (old_cluster == NULL) { 956 ret = -ENOMEM; 957 goto err; 958 } 959 960 /* copy content of unmodified sectors */ 961 ret = perform_cow(bs, m); 962 if (ret < 0) { 963 goto err; 964 } 965 966 /* Update L2 table. */ 967 if (s->use_lazy_refcounts) { 968 qcow2_mark_dirty(bs); 969 } 970 if (qcow2_need_accurate_refcounts(s)) { 971 qcow2_cache_set_dependency(bs, s->l2_table_cache, 972 s->refcount_block_cache); 973 } 974 975 ret = get_cluster_table(bs, m->offset, &l2_slice, &l2_index); 976 if (ret < 0) { 977 goto err; 978 } 979 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 980 981 assert(l2_index + m->nb_clusters <= s->l2_slice_size); 982 for (i = 0; i < m->nb_clusters; i++) { 983 uint64_t offset = cluster_offset + (i << s->cluster_bits); 984 /* if two concurrent writes happen to the same unallocated cluster 985 * each write allocates separate cluster and writes data concurrently. 986 * The first one to complete updates l2 table with pointer to its 987 * cluster the second one has to do RMW (which is done above by 988 * perform_cow()), update l2 table with its cluster pointer and free 989 * old cluster. This is what this loop does */ 990 if (l2_slice[l2_index + i] != 0) { 991 old_cluster[j++] = l2_slice[l2_index + i]; 992 } 993 994 /* The offset must fit in the offset field of the L2 table entry */ 995 assert((offset & L2E_OFFSET_MASK) == offset); 996 997 l2_slice[l2_index + i] = cpu_to_be64(offset | QCOW_OFLAG_COPIED); 998 } 999 1000 1001 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1002 1003 /* 1004 * If this was a COW, we need to decrease the refcount of the old cluster. 1005 * 1006 * Don't discard clusters that reach a refcount of 0 (e.g. compressed 1007 * clusters), the next write will reuse them anyway. 1008 */ 1009 if (!m->keep_old_clusters && j != 0) { 1010 for (i = 0; i < j; i++) { 1011 qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1, 1012 QCOW2_DISCARD_NEVER); 1013 } 1014 } 1015 1016 ret = 0; 1017 err: 1018 g_free(old_cluster); 1019 return ret; 1020 } 1021 1022 /** 1023 * Frees the allocated clusters because the request failed and they won't 1024 * actually be linked. 1025 */ 1026 void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m) 1027 { 1028 BDRVQcow2State *s = bs->opaque; 1029 if (!has_data_file(bs) && !m->keep_old_clusters) { 1030 qcow2_free_clusters(bs, m->alloc_offset, 1031 m->nb_clusters << s->cluster_bits, 1032 QCOW2_DISCARD_NEVER); 1033 } 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 /* Limit total allocation byte count to INT_MAX */ 1348 nb_clusters = MIN(nb_clusters, INT_MAX >> s->cluster_bits); 1349 1350 /* Find L2 entry for the first involved cluster */ 1351 ret = get_cluster_table(bs, guest_offset, &l2_slice, &l2_index); 1352 if (ret < 0) { 1353 return ret; 1354 } 1355 1356 entry = be64_to_cpu(l2_slice[l2_index]); 1357 nb_clusters = count_cow_clusters(bs, nb_clusters, l2_slice, l2_index); 1358 1359 /* This function is only called when there were no non-COW clusters, so if 1360 * we can't find any unallocated or COW clusters either, something is 1361 * wrong with our code. */ 1362 assert(nb_clusters > 0); 1363 1364 if (qcow2_get_cluster_type(bs, entry) == QCOW2_CLUSTER_ZERO_ALLOC && 1365 (entry & QCOW_OFLAG_COPIED) && 1366 (*host_offset == INV_OFFSET || 1367 start_of_cluster(s, *host_offset) == (entry & L2E_OFFSET_MASK))) 1368 { 1369 int preallocated_nb_clusters; 1370 1371 if (offset_into_cluster(s, entry & L2E_OFFSET_MASK)) { 1372 qcow2_signal_corruption(bs, true, -1, -1, "Preallocated zero " 1373 "cluster offset %#llx unaligned (guest " 1374 "offset: %#" PRIx64 ")", 1375 entry & L2E_OFFSET_MASK, guest_offset); 1376 ret = -EIO; 1377 goto fail; 1378 } 1379 1380 /* Try to reuse preallocated zero clusters; contiguous normal clusters 1381 * would be fine, too, but count_cow_clusters() above has limited 1382 * nb_clusters already to a range of COW clusters */ 1383 preallocated_nb_clusters = 1384 count_contiguous_clusters(bs, nb_clusters, s->cluster_size, 1385 &l2_slice[l2_index], QCOW_OFLAG_COPIED); 1386 assert(preallocated_nb_clusters > 0); 1387 1388 nb_clusters = preallocated_nb_clusters; 1389 alloc_cluster_offset = entry & L2E_OFFSET_MASK; 1390 1391 /* We want to reuse these clusters, so qcow2_alloc_cluster_link_l2() 1392 * should not free them. */ 1393 keep_old_clusters = true; 1394 } 1395 1396 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1397 1398 if (alloc_cluster_offset == INV_OFFSET) { 1399 /* Allocate, if necessary at a given offset in the image file */ 1400 alloc_cluster_offset = *host_offset == INV_OFFSET ? INV_OFFSET : 1401 start_of_cluster(s, *host_offset); 1402 ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset, 1403 &nb_clusters); 1404 if (ret < 0) { 1405 goto fail; 1406 } 1407 1408 /* Can't extend contiguous allocation */ 1409 if (nb_clusters == 0) { 1410 *bytes = 0; 1411 return 0; 1412 } 1413 1414 assert(alloc_cluster_offset != INV_OFFSET); 1415 } 1416 1417 /* 1418 * Save info needed for meta data update. 1419 * 1420 * requested_bytes: Number of bytes from the start of the first 1421 * newly allocated cluster to the end of the (possibly shortened 1422 * before) write request. 1423 * 1424 * avail_bytes: Number of bytes from the start of the first 1425 * newly allocated to the end of the last newly allocated cluster. 1426 * 1427 * nb_bytes: The number of bytes from the start of the first 1428 * newly allocated cluster to the end of the area that the write 1429 * request actually writes to (excluding COW at the end) 1430 */ 1431 uint64_t requested_bytes = *bytes + offset_into_cluster(s, guest_offset); 1432 int avail_bytes = nb_clusters << s->cluster_bits; 1433 int nb_bytes = MIN(requested_bytes, avail_bytes); 1434 QCowL2Meta *old_m = *m; 1435 1436 *m = g_malloc0(sizeof(**m)); 1437 1438 **m = (QCowL2Meta) { 1439 .next = old_m, 1440 1441 .alloc_offset = alloc_cluster_offset, 1442 .offset = start_of_cluster(s, guest_offset), 1443 .nb_clusters = nb_clusters, 1444 1445 .keep_old_clusters = keep_old_clusters, 1446 1447 .cow_start = { 1448 .offset = 0, 1449 .nb_bytes = offset_into_cluster(s, guest_offset), 1450 }, 1451 .cow_end = { 1452 .offset = nb_bytes, 1453 .nb_bytes = avail_bytes - nb_bytes, 1454 }, 1455 }; 1456 qemu_co_queue_init(&(*m)->dependent_requests); 1457 QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight); 1458 1459 *host_offset = alloc_cluster_offset + offset_into_cluster(s, guest_offset); 1460 *bytes = MIN(*bytes, nb_bytes - offset_into_cluster(s, guest_offset)); 1461 assert(*bytes != 0); 1462 1463 return 1; 1464 1465 fail: 1466 if (*m && (*m)->nb_clusters > 0) { 1467 QLIST_REMOVE(*m, next_in_flight); 1468 } 1469 return ret; 1470 } 1471 1472 /* 1473 * alloc_cluster_offset 1474 * 1475 * For a given offset on the virtual disk, find the cluster offset in qcow2 1476 * file. If the offset is not found, allocate a new cluster. 1477 * 1478 * If the cluster was already allocated, m->nb_clusters is set to 0 and 1479 * other fields in m are meaningless. 1480 * 1481 * If the cluster is newly allocated, m->nb_clusters is set to the number of 1482 * contiguous clusters that have been allocated. In this case, the other 1483 * fields of m are valid and contain information about the first allocated 1484 * cluster. 1485 * 1486 * If the request conflicts with another write request in flight, the coroutine 1487 * is queued and will be reentered when the dependency has completed. 1488 * 1489 * Return 0 on success and -errno in error cases 1490 */ 1491 int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, 1492 unsigned int *bytes, uint64_t *host_offset, 1493 QCowL2Meta **m) 1494 { 1495 BDRVQcow2State *s = bs->opaque; 1496 uint64_t start, remaining; 1497 uint64_t cluster_offset; 1498 uint64_t cur_bytes; 1499 int ret; 1500 1501 trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, *bytes); 1502 1503 again: 1504 start = offset; 1505 remaining = *bytes; 1506 cluster_offset = INV_OFFSET; 1507 *host_offset = INV_OFFSET; 1508 cur_bytes = 0; 1509 *m = NULL; 1510 1511 while (true) { 1512 1513 if (*host_offset == INV_OFFSET && cluster_offset != INV_OFFSET) { 1514 *host_offset = start_of_cluster(s, cluster_offset); 1515 } 1516 1517 assert(remaining >= cur_bytes); 1518 1519 start += cur_bytes; 1520 remaining -= cur_bytes; 1521 1522 if (cluster_offset != INV_OFFSET) { 1523 cluster_offset += cur_bytes; 1524 } 1525 1526 if (remaining == 0) { 1527 break; 1528 } 1529 1530 cur_bytes = remaining; 1531 1532 /* 1533 * Now start gathering as many contiguous clusters as possible: 1534 * 1535 * 1. Check for overlaps with in-flight allocations 1536 * 1537 * a) Overlap not in the first cluster -> shorten this request and 1538 * let the caller handle the rest in its next loop iteration. 1539 * 1540 * b) Real overlaps of two requests. Yield and restart the search 1541 * for contiguous clusters (the situation could have changed 1542 * while we were sleeping) 1543 * 1544 * c) TODO: Request starts in the same cluster as the in-flight 1545 * allocation ends. Shorten the COW of the in-fight allocation, 1546 * set cluster_offset to write to the same cluster and set up 1547 * the right synchronisation between the in-flight request and 1548 * the new one. 1549 */ 1550 ret = handle_dependencies(bs, start, &cur_bytes, m); 1551 if (ret == -EAGAIN) { 1552 /* Currently handle_dependencies() doesn't yield if we already had 1553 * an allocation. If it did, we would have to clean up the L2Meta 1554 * structs before starting over. */ 1555 assert(*m == NULL); 1556 goto again; 1557 } else if (ret < 0) { 1558 return ret; 1559 } else if (cur_bytes == 0) { 1560 break; 1561 } else { 1562 /* handle_dependencies() may have decreased cur_bytes (shortened 1563 * the allocations below) so that the next dependency is processed 1564 * correctly during the next loop iteration. */ 1565 } 1566 1567 /* 1568 * 2. Count contiguous COPIED clusters. 1569 */ 1570 ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m); 1571 if (ret < 0) { 1572 return ret; 1573 } else if (ret) { 1574 continue; 1575 } else if (cur_bytes == 0) { 1576 break; 1577 } 1578 1579 /* 1580 * 3. If the request still hasn't completed, allocate new clusters, 1581 * considering any cluster_offset of steps 1c or 2. 1582 */ 1583 ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m); 1584 if (ret < 0) { 1585 return ret; 1586 } else if (ret) { 1587 continue; 1588 } else { 1589 assert(cur_bytes == 0); 1590 break; 1591 } 1592 } 1593 1594 *bytes -= remaining; 1595 assert(*bytes > 0); 1596 assert(*host_offset != INV_OFFSET); 1597 1598 return 0; 1599 } 1600 1601 /* 1602 * This discards as many clusters of nb_clusters as possible at once (i.e. 1603 * all clusters in the same L2 slice) and returns the number of discarded 1604 * clusters. 1605 */ 1606 static int discard_in_l2_slice(BlockDriverState *bs, uint64_t offset, 1607 uint64_t nb_clusters, 1608 enum qcow2_discard_type type, bool full_discard) 1609 { 1610 BDRVQcow2State *s = bs->opaque; 1611 uint64_t *l2_slice; 1612 int l2_index; 1613 int ret; 1614 int i; 1615 1616 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 1617 if (ret < 0) { 1618 return ret; 1619 } 1620 1621 /* Limit nb_clusters to one L2 slice */ 1622 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1623 assert(nb_clusters <= INT_MAX); 1624 1625 for (i = 0; i < nb_clusters; i++) { 1626 uint64_t old_l2_entry; 1627 1628 old_l2_entry = be64_to_cpu(l2_slice[l2_index + i]); 1629 1630 /* 1631 * If full_discard is false, make sure that a discarded area reads back 1632 * as zeroes for v3 images (we cannot do it for v2 without actually 1633 * writing a zero-filled buffer). We can skip the operation if the 1634 * cluster is already marked as zero, or if it's unallocated and we 1635 * don't have a backing file. 1636 * 1637 * TODO We might want to use bdrv_block_status(bs) here, but we're 1638 * holding s->lock, so that doesn't work today. 1639 * 1640 * If full_discard is true, the sector should not read back as zeroes, 1641 * but rather fall through to the backing file. 1642 */ 1643 switch (qcow2_get_cluster_type(bs, old_l2_entry)) { 1644 case QCOW2_CLUSTER_UNALLOCATED: 1645 if (full_discard || !bs->backing) { 1646 continue; 1647 } 1648 break; 1649 1650 case QCOW2_CLUSTER_ZERO_PLAIN: 1651 if (!full_discard) { 1652 continue; 1653 } 1654 break; 1655 1656 case QCOW2_CLUSTER_ZERO_ALLOC: 1657 case QCOW2_CLUSTER_NORMAL: 1658 case QCOW2_CLUSTER_COMPRESSED: 1659 break; 1660 1661 default: 1662 abort(); 1663 } 1664 1665 /* First remove L2 entries */ 1666 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1667 if (!full_discard && s->qcow_version >= 3) { 1668 l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); 1669 } else { 1670 l2_slice[l2_index + i] = cpu_to_be64(0); 1671 } 1672 1673 /* Then decrease the refcount */ 1674 qcow2_free_any_clusters(bs, old_l2_entry, 1, type); 1675 } 1676 1677 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1678 1679 return nb_clusters; 1680 } 1681 1682 int qcow2_cluster_discard(BlockDriverState *bs, uint64_t offset, 1683 uint64_t bytes, enum qcow2_discard_type type, 1684 bool full_discard) 1685 { 1686 BDRVQcow2State *s = bs->opaque; 1687 uint64_t end_offset = offset + bytes; 1688 uint64_t nb_clusters; 1689 int64_t cleared; 1690 int ret; 1691 1692 /* Caller must pass aligned values, except at image end */ 1693 assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); 1694 assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || 1695 end_offset == bs->total_sectors << BDRV_SECTOR_BITS); 1696 1697 nb_clusters = size_to_clusters(s, bytes); 1698 1699 s->cache_discards = true; 1700 1701 /* Each L2 slice is handled by its own loop iteration */ 1702 while (nb_clusters > 0) { 1703 cleared = discard_in_l2_slice(bs, offset, nb_clusters, type, 1704 full_discard); 1705 if (cleared < 0) { 1706 ret = cleared; 1707 goto fail; 1708 } 1709 1710 nb_clusters -= cleared; 1711 offset += (cleared * s->cluster_size); 1712 } 1713 1714 ret = 0; 1715 fail: 1716 s->cache_discards = false; 1717 qcow2_process_discards(bs, ret); 1718 1719 return ret; 1720 } 1721 1722 /* 1723 * This zeroes as many clusters of nb_clusters as possible at once (i.e. 1724 * all clusters in the same L2 slice) and returns the number of zeroed 1725 * clusters. 1726 */ 1727 static int zero_in_l2_slice(BlockDriverState *bs, uint64_t offset, 1728 uint64_t nb_clusters, int flags) 1729 { 1730 BDRVQcow2State *s = bs->opaque; 1731 uint64_t *l2_slice; 1732 int l2_index; 1733 int ret; 1734 int i; 1735 bool unmap = !!(flags & BDRV_REQ_MAY_UNMAP); 1736 1737 ret = get_cluster_table(bs, offset, &l2_slice, &l2_index); 1738 if (ret < 0) { 1739 return ret; 1740 } 1741 1742 /* Limit nb_clusters to one L2 slice */ 1743 nb_clusters = MIN(nb_clusters, s->l2_slice_size - l2_index); 1744 assert(nb_clusters <= INT_MAX); 1745 1746 for (i = 0; i < nb_clusters; i++) { 1747 uint64_t old_offset; 1748 QCow2ClusterType cluster_type; 1749 1750 old_offset = be64_to_cpu(l2_slice[l2_index + i]); 1751 1752 /* 1753 * Minimize L2 changes if the cluster already reads back as 1754 * zeroes with correct allocation. 1755 */ 1756 cluster_type = qcow2_get_cluster_type(bs, old_offset); 1757 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN || 1758 (cluster_type == QCOW2_CLUSTER_ZERO_ALLOC && !unmap)) { 1759 continue; 1760 } 1761 1762 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 1763 if (cluster_type == QCOW2_CLUSTER_COMPRESSED || unmap) { 1764 l2_slice[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); 1765 qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); 1766 } else { 1767 l2_slice[l2_index + i] |= cpu_to_be64(QCOW_OFLAG_ZERO); 1768 } 1769 } 1770 1771 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 1772 1773 return nb_clusters; 1774 } 1775 1776 int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset, 1777 uint64_t bytes, int flags) 1778 { 1779 BDRVQcow2State *s = bs->opaque; 1780 uint64_t end_offset = offset + bytes; 1781 uint64_t nb_clusters; 1782 int64_t cleared; 1783 int ret; 1784 1785 /* If we have to stay in sync with an external data file, zero out 1786 * s->data_file first. */ 1787 if (data_file_is_raw(bs)) { 1788 assert(has_data_file(bs)); 1789 ret = bdrv_co_pwrite_zeroes(s->data_file, offset, bytes, flags); 1790 if (ret < 0) { 1791 return ret; 1792 } 1793 } 1794 1795 /* Caller must pass aligned values, except at image end */ 1796 assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); 1797 assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) || 1798 end_offset >= bs->total_sectors << BDRV_SECTOR_BITS); 1799 1800 /* 1801 * The zero flag is only supported by version 3 and newer. However, if we 1802 * have no backing file, we can resort to discard in version 2. 1803 */ 1804 if (s->qcow_version < 3) { 1805 if (!bs->backing) { 1806 return qcow2_cluster_discard(bs, offset, bytes, 1807 QCOW2_DISCARD_REQUEST, false); 1808 } 1809 return -ENOTSUP; 1810 } 1811 1812 /* Each L2 slice is handled by its own loop iteration */ 1813 nb_clusters = size_to_clusters(s, bytes); 1814 1815 s->cache_discards = true; 1816 1817 while (nb_clusters > 0) { 1818 cleared = zero_in_l2_slice(bs, offset, nb_clusters, flags); 1819 if (cleared < 0) { 1820 ret = cleared; 1821 goto fail; 1822 } 1823 1824 nb_clusters -= cleared; 1825 offset += (cleared * s->cluster_size); 1826 } 1827 1828 ret = 0; 1829 fail: 1830 s->cache_discards = false; 1831 qcow2_process_discards(bs, ret); 1832 1833 return ret; 1834 } 1835 1836 /* 1837 * Expands all zero clusters in a specific L1 table (or deallocates them, for 1838 * non-backed non-pre-allocated zero clusters). 1839 * 1840 * l1_entries and *visited_l1_entries are used to keep track of progress for 1841 * status_cb(). l1_entries contains the total number of L1 entries and 1842 * *visited_l1_entries counts all visited L1 entries. 1843 */ 1844 static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table, 1845 int l1_size, int64_t *visited_l1_entries, 1846 int64_t l1_entries, 1847 BlockDriverAmendStatusCB *status_cb, 1848 void *cb_opaque) 1849 { 1850 BDRVQcow2State *s = bs->opaque; 1851 bool is_active_l1 = (l1_table == s->l1_table); 1852 uint64_t *l2_slice = NULL; 1853 unsigned slice, slice_size2, n_slices; 1854 int ret; 1855 int i, j; 1856 1857 slice_size2 = s->l2_slice_size * sizeof(uint64_t); 1858 n_slices = s->cluster_size / slice_size2; 1859 1860 if (!is_active_l1) { 1861 /* inactive L2 tables require a buffer to be stored in when loading 1862 * them from disk */ 1863 l2_slice = qemu_try_blockalign(bs->file->bs, slice_size2); 1864 if (l2_slice == NULL) { 1865 return -ENOMEM; 1866 } 1867 } 1868 1869 for (i = 0; i < l1_size; i++) { 1870 uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK; 1871 uint64_t l2_refcount; 1872 1873 if (!l2_offset) { 1874 /* unallocated */ 1875 (*visited_l1_entries)++; 1876 if (status_cb) { 1877 status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); 1878 } 1879 continue; 1880 } 1881 1882 if (offset_into_cluster(s, l2_offset)) { 1883 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#" 1884 PRIx64 " unaligned (L1 index: %#x)", 1885 l2_offset, i); 1886 ret = -EIO; 1887 goto fail; 1888 } 1889 1890 ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits, 1891 &l2_refcount); 1892 if (ret < 0) { 1893 goto fail; 1894 } 1895 1896 for (slice = 0; slice < n_slices; slice++) { 1897 uint64_t slice_offset = l2_offset + slice * slice_size2; 1898 bool l2_dirty = false; 1899 if (is_active_l1) { 1900 /* get active L2 tables from cache */ 1901 ret = qcow2_cache_get(bs, s->l2_table_cache, slice_offset, 1902 (void **)&l2_slice); 1903 } else { 1904 /* load inactive L2 tables from disk */ 1905 ret = bdrv_pread(bs->file, slice_offset, l2_slice, slice_size2); 1906 } 1907 if (ret < 0) { 1908 goto fail; 1909 } 1910 1911 for (j = 0; j < s->l2_slice_size; j++) { 1912 uint64_t l2_entry = be64_to_cpu(l2_slice[j]); 1913 int64_t offset = l2_entry & L2E_OFFSET_MASK; 1914 QCow2ClusterType cluster_type = 1915 qcow2_get_cluster_type(bs, l2_entry); 1916 1917 if (cluster_type != QCOW2_CLUSTER_ZERO_PLAIN && 1918 cluster_type != QCOW2_CLUSTER_ZERO_ALLOC) { 1919 continue; 1920 } 1921 1922 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1923 if (!bs->backing) { 1924 /* not backed; therefore we can simply deallocate the 1925 * cluster */ 1926 l2_slice[j] = 0; 1927 l2_dirty = true; 1928 continue; 1929 } 1930 1931 offset = qcow2_alloc_clusters(bs, s->cluster_size); 1932 if (offset < 0) { 1933 ret = offset; 1934 goto fail; 1935 } 1936 1937 /* The offset must fit in the offset field */ 1938 assert((offset & L2E_OFFSET_MASK) == offset); 1939 1940 if (l2_refcount > 1) { 1941 /* For shared L2 tables, set the refcount accordingly 1942 * (it is already 1 and needs to be l2_refcount) */ 1943 ret = qcow2_update_cluster_refcount( 1944 bs, offset >> s->cluster_bits, 1945 refcount_diff(1, l2_refcount), false, 1946 QCOW2_DISCARD_OTHER); 1947 if (ret < 0) { 1948 qcow2_free_clusters(bs, offset, s->cluster_size, 1949 QCOW2_DISCARD_OTHER); 1950 goto fail; 1951 } 1952 } 1953 } 1954 1955 if (offset_into_cluster(s, offset)) { 1956 int l2_index = slice * s->l2_slice_size + j; 1957 qcow2_signal_corruption( 1958 bs, true, -1, -1, 1959 "Cluster allocation offset " 1960 "%#" PRIx64 " unaligned (L2 offset: %#" 1961 PRIx64 ", L2 index: %#x)", offset, 1962 l2_offset, l2_index); 1963 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1964 qcow2_free_clusters(bs, offset, s->cluster_size, 1965 QCOW2_DISCARD_ALWAYS); 1966 } 1967 ret = -EIO; 1968 goto fail; 1969 } 1970 1971 ret = qcow2_pre_write_overlap_check(bs, 0, offset, 1972 s->cluster_size, true); 1973 if (ret < 0) { 1974 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1975 qcow2_free_clusters(bs, offset, s->cluster_size, 1976 QCOW2_DISCARD_ALWAYS); 1977 } 1978 goto fail; 1979 } 1980 1981 ret = bdrv_pwrite_zeroes(s->data_file, offset, 1982 s->cluster_size, 0); 1983 if (ret < 0) { 1984 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) { 1985 qcow2_free_clusters(bs, offset, s->cluster_size, 1986 QCOW2_DISCARD_ALWAYS); 1987 } 1988 goto fail; 1989 } 1990 1991 if (l2_refcount == 1) { 1992 l2_slice[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED); 1993 } else { 1994 l2_slice[j] = cpu_to_be64(offset); 1995 } 1996 l2_dirty = true; 1997 } 1998 1999 if (is_active_l1) { 2000 if (l2_dirty) { 2001 qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 2002 qcow2_cache_depends_on_flush(s->l2_table_cache); 2003 } 2004 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 2005 } else { 2006 if (l2_dirty) { 2007 ret = qcow2_pre_write_overlap_check( 2008 bs, QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2, 2009 slice_offset, slice_size2, false); 2010 if (ret < 0) { 2011 goto fail; 2012 } 2013 2014 ret = bdrv_pwrite(bs->file, slice_offset, 2015 l2_slice, slice_size2); 2016 if (ret < 0) { 2017 goto fail; 2018 } 2019 } 2020 } 2021 } 2022 2023 (*visited_l1_entries)++; 2024 if (status_cb) { 2025 status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque); 2026 } 2027 } 2028 2029 ret = 0; 2030 2031 fail: 2032 if (l2_slice) { 2033 if (!is_active_l1) { 2034 qemu_vfree(l2_slice); 2035 } else { 2036 qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice); 2037 } 2038 } 2039 return ret; 2040 } 2041 2042 /* 2043 * For backed images, expands all zero clusters on the image. For non-backed 2044 * images, deallocates all non-pre-allocated zero clusters (and claims the 2045 * allocation for pre-allocated ones). This is important for downgrading to a 2046 * qcow2 version which doesn't yet support metadata zero clusters. 2047 */ 2048 int qcow2_expand_zero_clusters(BlockDriverState *bs, 2049 BlockDriverAmendStatusCB *status_cb, 2050 void *cb_opaque) 2051 { 2052 BDRVQcow2State *s = bs->opaque; 2053 uint64_t *l1_table = NULL; 2054 int64_t l1_entries = 0, visited_l1_entries = 0; 2055 int ret; 2056 int i, j; 2057 2058 if (status_cb) { 2059 l1_entries = s->l1_size; 2060 for (i = 0; i < s->nb_snapshots; i++) { 2061 l1_entries += s->snapshots[i].l1_size; 2062 } 2063 } 2064 2065 ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size, 2066 &visited_l1_entries, l1_entries, 2067 status_cb, cb_opaque); 2068 if (ret < 0) { 2069 goto fail; 2070 } 2071 2072 /* Inactive L1 tables may point to active L2 tables - therefore it is 2073 * necessary to flush the L2 table cache before trying to access the L2 2074 * tables pointed to by inactive L1 entries (else we might try to expand 2075 * zero clusters that have already been expanded); furthermore, it is also 2076 * necessary to empty the L2 table cache, since it may contain tables which 2077 * are now going to be modified directly on disk, bypassing the cache. 2078 * qcow2_cache_empty() does both for us. */ 2079 ret = qcow2_cache_empty(bs, s->l2_table_cache); 2080 if (ret < 0) { 2081 goto fail; 2082 } 2083 2084 for (i = 0; i < s->nb_snapshots; i++) { 2085 int l1_size2; 2086 uint64_t *new_l1_table; 2087 Error *local_err = NULL; 2088 2089 ret = qcow2_validate_table(bs, s->snapshots[i].l1_table_offset, 2090 s->snapshots[i].l1_size, sizeof(uint64_t), 2091 QCOW_MAX_L1_SIZE, "Snapshot L1 table", 2092 &local_err); 2093 if (ret < 0) { 2094 error_report_err(local_err); 2095 goto fail; 2096 } 2097 2098 l1_size2 = s->snapshots[i].l1_size * sizeof(uint64_t); 2099 new_l1_table = g_try_realloc(l1_table, l1_size2); 2100 2101 if (!new_l1_table) { 2102 ret = -ENOMEM; 2103 goto fail; 2104 } 2105 2106 l1_table = new_l1_table; 2107 2108 ret = bdrv_pread(bs->file, s->snapshots[i].l1_table_offset, 2109 l1_table, l1_size2); 2110 if (ret < 0) { 2111 goto fail; 2112 } 2113 2114 for (j = 0; j < s->snapshots[i].l1_size; j++) { 2115 be64_to_cpus(&l1_table[j]); 2116 } 2117 2118 ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size, 2119 &visited_l1_entries, l1_entries, 2120 status_cb, cb_opaque); 2121 if (ret < 0) { 2122 goto fail; 2123 } 2124 } 2125 2126 ret = 0; 2127 2128 fail: 2129 g_free(l1_table); 2130 return ret; 2131 } 2132