qcow2: Fix alloc_cluster_abort() for pre-existing clusters
[qemu.git] / block / qcow2-cluster.c
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 /* The zero flag is only supported by version 3 and newer */
1801 if (s->qcow_version < 3) {
1802 return -ENOTSUP;
1803 }
1804
1805 /* Each L2 slice is handled by its own loop iteration */
1806 nb_clusters = size_to_clusters(s, bytes);
1807
1808 s->cache_discards = true;
1809
1810 while (nb_clusters > 0) {
1811 cleared = zero_in_l2_slice(bs, offset, nb_clusters, flags);
1812 if (cleared < 0) {
1813 ret = cleared;
1814 goto fail;
1815 }
1816
1817 nb_clusters -= cleared;
1818 offset += (cleared * s->cluster_size);
1819 }
1820
1821 ret = 0;
1822 fail:
1823 s->cache_discards = false;
1824 qcow2_process_discards(bs, ret);
1825
1826 return ret;
1827 }
1828
1829 /*
1830 * Expands all zero clusters in a specific L1 table (or deallocates them, for
1831 * non-backed non-pre-allocated zero clusters).
1832 *
1833 * l1_entries and *visited_l1_entries are used to keep track of progress for
1834 * status_cb(). l1_entries contains the total number of L1 entries and
1835 * *visited_l1_entries counts all visited L1 entries.
1836 */
1837 static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
1838 int l1_size, int64_t *visited_l1_entries,
1839 int64_t l1_entries,
1840 BlockDriverAmendStatusCB *status_cb,
1841 void *cb_opaque)
1842 {
1843 BDRVQcow2State *s = bs->opaque;
1844 bool is_active_l1 = (l1_table == s->l1_table);
1845 uint64_t *l2_slice = NULL;
1846 unsigned slice, slice_size2, n_slices;
1847 int ret;
1848 int i, j;
1849
1850 slice_size2 = s->l2_slice_size * sizeof(uint64_t);
1851 n_slices = s->cluster_size / slice_size2;
1852
1853 if (!is_active_l1) {
1854 /* inactive L2 tables require a buffer to be stored in when loading
1855 * them from disk */
1856 l2_slice = qemu_try_blockalign(bs->file->bs, slice_size2);
1857 if (l2_slice == NULL) {
1858 return -ENOMEM;
1859 }
1860 }
1861
1862 for (i = 0; i < l1_size; i++) {
1863 uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK;
1864 uint64_t l2_refcount;
1865
1866 if (!l2_offset) {
1867 /* unallocated */
1868 (*visited_l1_entries)++;
1869 if (status_cb) {
1870 status_cb(bs, *visited_l1_entries, l1_entries, cb_opaque);
1871 }
1872 continue;
1873 }
1874
1875 if (offset_into_cluster(s, l2_offset)) {
1876 qcow2_signal_corruption(bs, true, -1, -1, "L2 table offset %#"
1877 PRIx64 " unaligned (L1 index: %#x)",
1878 l2_offset, i);
1879 ret = -EIO;
1880 goto fail;
1881 }
1882
1883 ret = qcow2_get_refcount(bs, l2_offset >> s->cluster_bits,
1884 &l2_refcount);
1885 if (ret < 0) {
1886 goto fail;
1887 }
1888
1889 for (slice = 0; slice < n_slices; slice++) {
1890 uint64_t slice_offset = l2_offset + slice * slice_size2;
1891 bool l2_dirty = false;
1892 if (is_active_l1) {
1893 /* get active L2 tables from cache */
1894 ret = qcow2_cache_get(bs, s->l2_table_cache, slice_offset,
1895 (void **)&l2_slice);
1896 } else {
1897 /* load inactive L2 tables from disk */
1898 ret = bdrv_pread(bs->file, slice_offset, l2_slice, slice_size2);
1899 }
1900 if (ret < 0) {
1901 goto fail;
1902 }
1903
1904 for (j = 0; j < s->l2_slice_size; j++) {
1905 uint64_t l2_entry = be64_to_cpu(l2_slice[j]);
1906 int64_t offset = l2_entry & L2E_OFFSET_MASK;
1907 QCow2ClusterType cluster_type =
1908 qcow2_get_cluster_type(bs, l2_entry);
1909
1910 if (cluster_type != QCOW2_CLUSTER_ZERO_PLAIN &&
1911 cluster_type != QCOW2_CLUSTER_ZERO_ALLOC) {
1912 continue;
1913 }
1914
1915 if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN) {
1916 if (!bs->backing) {
1917 /* not backed; therefore we can simply deallocate the
1918 * cluster */
1919 l2_slice[j] = 0;
1920 l2_dirty = true;
1921 continue;
1922 }
1923
1924 offset = qcow2_alloc_clusters(bs, s->cluster_size);
1925 if (offset < 0) {
1926 ret = offset;
1927 goto fail;
1928 }
1929
1930 /* The offset must fit in the offset field */
1931 assert((offset & L2E_OFFSET_MASK) == offset);
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 }