2 * Block driver for the QCOW version 2 format
4 * Copyright (c) 2004-2006 Fabrice Bellard
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:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
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
25 #include "qemu/osdep.h"
28 #include "qapi/error.h"
29 #include "qemu-common.h"
30 #include "block/block_int.h"
32 #include "qemu/bswap.h"
35 int qcow2_shrink_l1_table(BlockDriverState
*bs
, uint64_t exact_size
)
37 BDRVQcow2State
*s
= bs
->opaque
;
38 int new_l1_size
, i
, ret
;
40 if (exact_size
>= s
->l1_size
) {
44 new_l1_size
= exact_size
;
47 fprintf(stderr
, "shrink l1_table from %d to %d\n", s
->l1_size
, new_l1_size
);
50 BLKDBG_EVENT(bs
->file
, BLKDBG_L1_SHRINK_WRITE_TABLE
);
51 ret
= bdrv_pwrite_zeroes(bs
->file
, s
->l1_table_offset
+
52 new_l1_size
* sizeof(uint64_t),
53 (s
->l1_size
- new_l1_size
) * sizeof(uint64_t), 0);
58 ret
= bdrv_flush(bs
->file
->bs
);
63 BLKDBG_EVENT(bs
->file
, BLKDBG_L1_SHRINK_FREE_L2_CLUSTERS
);
64 for (i
= s
->l1_size
- 1; i
> new_l1_size
- 1; i
--) {
65 if ((s
->l1_table
[i
] & L1E_OFFSET_MASK
) == 0) {
68 qcow2_free_clusters(bs
, s
->l1_table
[i
] & L1E_OFFSET_MASK
,
69 s
->cluster_size
, QCOW2_DISCARD_ALWAYS
);
76 * If the write in the l1_table failed the image may contain a partially
77 * overwritten l1_table. In this case it would be better to clear the
78 * l1_table in memory to avoid possible image corruption.
80 memset(s
->l1_table
+ new_l1_size
, 0,
81 (s
->l1_size
- new_l1_size
) * sizeof(uint64_t));
85 int qcow2_grow_l1_table(BlockDriverState
*bs
, uint64_t min_size
,
88 BDRVQcow2State
*s
= bs
->opaque
;
89 int new_l1_size2
, ret
, i
;
90 uint64_t *new_l1_table
;
91 int64_t old_l1_table_offset
, old_l1_size
;
92 int64_t new_l1_table_offset
, new_l1_size
;
95 if (min_size
<= s
->l1_size
)
98 /* Do a sanity check on min_size before trying to calculate new_l1_size
99 * (this prevents overflows during the while loop for the calculation of
101 if (min_size
> INT_MAX
/ sizeof(uint64_t)) {
106 new_l1_size
= min_size
;
108 /* Bump size up to reduce the number of times we have to grow */
109 new_l1_size
= s
->l1_size
;
110 if (new_l1_size
== 0) {
113 while (min_size
> new_l1_size
) {
114 new_l1_size
= DIV_ROUND_UP(new_l1_size
* 3, 2);
118 QEMU_BUILD_BUG_ON(QCOW_MAX_L1_SIZE
> INT_MAX
);
119 if (new_l1_size
> QCOW_MAX_L1_SIZE
/ sizeof(uint64_t)) {
124 fprintf(stderr
, "grow l1_table from %d to %" PRId64
"\n",
125 s
->l1_size
, new_l1_size
);
128 new_l1_size2
= sizeof(uint64_t) * new_l1_size
;
129 new_l1_table
= qemu_try_blockalign(bs
->file
->bs
,
130 ROUND_UP(new_l1_size2
, 512));
131 if (new_l1_table
== NULL
) {
134 memset(new_l1_table
, 0, ROUND_UP(new_l1_size2
, 512));
137 memcpy(new_l1_table
, s
->l1_table
, s
->l1_size
* sizeof(uint64_t));
140 /* write new table (align to cluster) */
141 BLKDBG_EVENT(bs
->file
, BLKDBG_L1_GROW_ALLOC_TABLE
);
142 new_l1_table_offset
= qcow2_alloc_clusters(bs
, new_l1_size2
);
143 if (new_l1_table_offset
< 0) {
144 qemu_vfree(new_l1_table
);
145 return new_l1_table_offset
;
148 ret
= qcow2_cache_flush(bs
, s
->refcount_block_cache
);
153 /* the L1 position has not yet been updated, so these clusters must
154 * indeed be completely free */
155 ret
= qcow2_pre_write_overlap_check(bs
, 0, new_l1_table_offset
,
161 BLKDBG_EVENT(bs
->file
, BLKDBG_L1_GROW_WRITE_TABLE
);
162 for(i
= 0; i
< s
->l1_size
; i
++)
163 new_l1_table
[i
] = cpu_to_be64(new_l1_table
[i
]);
164 ret
= bdrv_pwrite_sync(bs
->file
, new_l1_table_offset
,
165 new_l1_table
, new_l1_size2
);
168 for(i
= 0; i
< s
->l1_size
; i
++)
169 new_l1_table
[i
] = be64_to_cpu(new_l1_table
[i
]);
172 BLKDBG_EVENT(bs
->file
, BLKDBG_L1_GROW_ACTIVATE_TABLE
);
173 stl_be_p(data
, new_l1_size
);
174 stq_be_p(data
+ 4, new_l1_table_offset
);
175 ret
= bdrv_pwrite_sync(bs
->file
, offsetof(QCowHeader
, l1_size
),
180 qemu_vfree(s
->l1_table
);
181 old_l1_table_offset
= s
->l1_table_offset
;
182 s
->l1_table_offset
= new_l1_table_offset
;
183 s
->l1_table
= new_l1_table
;
184 old_l1_size
= s
->l1_size
;
185 s
->l1_size
= new_l1_size
;
186 qcow2_free_clusters(bs
, old_l1_table_offset
, old_l1_size
* sizeof(uint64_t),
187 QCOW2_DISCARD_OTHER
);
190 qemu_vfree(new_l1_table
);
191 qcow2_free_clusters(bs
, new_l1_table_offset
, new_l1_size2
,
192 QCOW2_DISCARD_OTHER
);
199 * @bs: The BlockDriverState
200 * @offset: A guest offset, used to calculate what slice of the L2
202 * @l2_offset: Offset to the L2 table in the image file.
203 * @l2_slice: Location to store the pointer to the L2 slice.
205 * Loads a L2 slice into memory (L2 slices are the parts of L2 tables
206 * that are loaded by the qcow2 cache). If the slice is in the cache,
207 * the cache is used; otherwise the L2 slice is loaded from the image
210 static int l2_load(BlockDriverState
*bs
, uint64_t offset
,
211 uint64_t l2_offset
, uint64_t **l2_slice
)
213 BDRVQcow2State
*s
= bs
->opaque
;
214 int start_of_slice
= sizeof(uint64_t) *
215 (offset_to_l2_index(s
, offset
) - offset_to_l2_slice_index(s
, offset
));
217 return qcow2_cache_get(bs
, s
->l2_table_cache
, l2_offset
+ start_of_slice
,
222 * Writes one sector of the L1 table to the disk (can't update single entries
223 * and we really don't want bdrv_pread to perform a read-modify-write)
225 #define L1_ENTRIES_PER_SECTOR (512 / 8)
226 int qcow2_write_l1_entry(BlockDriverState
*bs
, int l1_index
)
228 BDRVQcow2State
*s
= bs
->opaque
;
229 uint64_t buf
[L1_ENTRIES_PER_SECTOR
] = { 0 };
233 l1_start_index
= l1_index
& ~(L1_ENTRIES_PER_SECTOR
- 1);
234 for (i
= 0; i
< L1_ENTRIES_PER_SECTOR
&& l1_start_index
+ i
< s
->l1_size
;
237 buf
[i
] = cpu_to_be64(s
->l1_table
[l1_start_index
+ i
]);
240 ret
= qcow2_pre_write_overlap_check(bs
, QCOW2_OL_ACTIVE_L1
,
241 s
->l1_table_offset
+ 8 * l1_start_index
, sizeof(buf
));
246 BLKDBG_EVENT(bs
->file
, BLKDBG_L1_UPDATE
);
247 ret
= bdrv_pwrite_sync(bs
->file
,
248 s
->l1_table_offset
+ 8 * l1_start_index
,
260 * Allocate a new l2 entry in the file. If l1_index points to an already
261 * used entry in the L2 table (i.e. we are doing a copy on write for the L2
262 * table) copy the contents of the old L2 table into the newly allocated one.
263 * Otherwise the new table is initialized with zeros.
267 static int l2_allocate(BlockDriverState
*bs
, int l1_index
)
269 BDRVQcow2State
*s
= bs
->opaque
;
270 uint64_t old_l2_offset
;
271 uint64_t *l2_slice
= NULL
;
272 unsigned slice
, slice_size2
, n_slices
;
276 old_l2_offset
= s
->l1_table
[l1_index
];
278 trace_qcow2_l2_allocate(bs
, l1_index
);
280 /* allocate a new l2 entry */
282 l2_offset
= qcow2_alloc_clusters(bs
, s
->l2_size
* sizeof(uint64_t));
288 /* The offset must fit in the offset field of the L1 table entry */
289 assert((l2_offset
& L1E_OFFSET_MASK
) == l2_offset
);
291 /* If we're allocating the table at offset 0 then something is wrong */
292 if (l2_offset
== 0) {
293 qcow2_signal_corruption(bs
, true, -1, -1, "Preventing invalid "
294 "allocation of L2 table at offset 0");
299 ret
= qcow2_cache_flush(bs
, s
->refcount_block_cache
);
304 /* allocate a new entry in the l2 cache */
306 slice_size2
= s
->l2_slice_size
* sizeof(uint64_t);
307 n_slices
= s
->cluster_size
/ slice_size2
;
309 trace_qcow2_l2_allocate_get_empty(bs
, l1_index
);
310 for (slice
= 0; slice
< n_slices
; slice
++) {
311 ret
= qcow2_cache_get_empty(bs
, s
->l2_table_cache
,
312 l2_offset
+ slice
* slice_size2
,
313 (void **) &l2_slice
);
318 if ((old_l2_offset
& L1E_OFFSET_MASK
) == 0) {
319 /* if there was no old l2 table, clear the new slice */
320 memset(l2_slice
, 0, slice_size2
);
323 uint64_t old_l2_slice_offset
=
324 (old_l2_offset
& L1E_OFFSET_MASK
) + slice
* slice_size2
;
326 /* if there was an old l2 table, read a slice from the disk */
327 BLKDBG_EVENT(bs
->file
, BLKDBG_L2_ALLOC_COW_READ
);
328 ret
= qcow2_cache_get(bs
, s
->l2_table_cache
, old_l2_slice_offset
,
329 (void **) &old_slice
);
334 memcpy(l2_slice
, old_slice
, slice_size2
);
336 qcow2_cache_put(s
->l2_table_cache
, (void **) &old_slice
);
339 /* write the l2 slice to the file */
340 BLKDBG_EVENT(bs
->file
, BLKDBG_L2_ALLOC_WRITE
);
342 trace_qcow2_l2_allocate_write_l2(bs
, l1_index
);
343 qcow2_cache_entry_mark_dirty(s
->l2_table_cache
, l2_slice
);
344 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
347 ret
= qcow2_cache_flush(bs
, s
->l2_table_cache
);
352 /* update the L1 entry */
353 trace_qcow2_l2_allocate_write_l1(bs
, l1_index
);
354 s
->l1_table
[l1_index
] = l2_offset
| QCOW_OFLAG_COPIED
;
355 ret
= qcow2_write_l1_entry(bs
, l1_index
);
360 trace_qcow2_l2_allocate_done(bs
, l1_index
, 0);
364 trace_qcow2_l2_allocate_done(bs
, l1_index
, ret
);
365 if (l2_slice
!= NULL
) {
366 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
368 s
->l1_table
[l1_index
] = old_l2_offset
;
370 qcow2_free_clusters(bs
, l2_offset
, s
->l2_size
* sizeof(uint64_t),
371 QCOW2_DISCARD_ALWAYS
);
377 * Checks how many clusters in a given L2 slice are contiguous in the image
378 * file. As soon as one of the flags in the bitmask stop_flags changes compared
379 * to the first cluster, the search is stopped and the cluster is not counted
380 * as contiguous. (This allows it, for example, to stop at the first compressed
381 * cluster which may require a different handling)
383 static int count_contiguous_clusters(BlockDriverState
*bs
, int nb_clusters
,
384 int cluster_size
, uint64_t *l2_slice
, uint64_t stop_flags
)
387 QCow2ClusterType first_cluster_type
;
388 uint64_t mask
= stop_flags
| L2E_OFFSET_MASK
| QCOW_OFLAG_COMPRESSED
;
389 uint64_t first_entry
= be64_to_cpu(l2_slice
[0]);
390 uint64_t offset
= first_entry
& mask
;
396 /* must be allocated */
397 first_cluster_type
= qcow2_get_cluster_type(bs
, first_entry
);
398 assert(first_cluster_type
== QCOW2_CLUSTER_NORMAL
||
399 first_cluster_type
== QCOW2_CLUSTER_ZERO_ALLOC
);
401 for (i
= 0; i
< nb_clusters
; i
++) {
402 uint64_t l2_entry
= be64_to_cpu(l2_slice
[i
]) & mask
;
403 if (offset
+ (uint64_t) i
* cluster_size
!= l2_entry
) {
412 * Checks how many consecutive unallocated clusters in a given L2
413 * slice have the same cluster type.
415 static int count_contiguous_clusters_unallocated(BlockDriverState
*bs
,
418 QCow2ClusterType wanted_type
)
422 assert(wanted_type
== QCOW2_CLUSTER_ZERO_PLAIN
||
423 wanted_type
== QCOW2_CLUSTER_UNALLOCATED
);
424 for (i
= 0; i
< nb_clusters
; i
++) {
425 uint64_t entry
= be64_to_cpu(l2_slice
[i
]);
426 QCow2ClusterType type
= qcow2_get_cluster_type(bs
, entry
);
428 if (type
!= wanted_type
) {
436 static int coroutine_fn
do_perform_cow_read(BlockDriverState
*bs
,
437 uint64_t src_cluster_offset
,
438 unsigned offset_in_cluster
,
443 if (qiov
->size
== 0) {
447 BLKDBG_EVENT(bs
->file
, BLKDBG_COW_READ
);
453 /* Call .bdrv_co_readv() directly instead of using the public block-layer
454 * interface. This avoids double I/O throttling and request tracking,
455 * which can lead to deadlock when block layer copy-on-read is enabled.
457 ret
= bs
->drv
->bdrv_co_preadv(bs
, src_cluster_offset
+ offset_in_cluster
,
458 qiov
->size
, qiov
, 0);
466 static bool coroutine_fn
do_perform_cow_encrypt(BlockDriverState
*bs
,
467 uint64_t src_cluster_offset
,
468 uint64_t cluster_offset
,
469 unsigned offset_in_cluster
,
473 if (bytes
&& bs
->encrypted
) {
474 BDRVQcow2State
*s
= bs
->opaque
;
475 int64_t offset
= (s
->crypt_physical_offset
?
476 (cluster_offset
+ offset_in_cluster
) :
477 (src_cluster_offset
+ offset_in_cluster
));
478 assert((offset_in_cluster
& ~BDRV_SECTOR_MASK
) == 0);
479 assert((bytes
& ~BDRV_SECTOR_MASK
) == 0);
481 if (qcrypto_block_encrypt(s
->crypto
, offset
, buffer
, bytes
, NULL
) < 0) {
488 static int coroutine_fn
do_perform_cow_write(BlockDriverState
*bs
,
489 uint64_t cluster_offset
,
490 unsigned offset_in_cluster
,
495 if (qiov
->size
== 0) {
499 ret
= qcow2_pre_write_overlap_check(bs
, 0,
500 cluster_offset
+ offset_in_cluster
, qiov
->size
);
505 BLKDBG_EVENT(bs
->file
, BLKDBG_COW_WRITE
);
506 ret
= bdrv_co_pwritev(bs
->file
, cluster_offset
+ offset_in_cluster
,
507 qiov
->size
, qiov
, 0);
519 * For a given offset of the virtual disk, find the cluster type and offset in
520 * the qcow2 file. The offset is stored in *cluster_offset.
522 * On entry, *bytes is the maximum number of contiguous bytes starting at
523 * offset that we are interested in.
525 * On exit, *bytes is the number of bytes starting at offset that have the same
526 * cluster type and (if applicable) are stored contiguously in the image file.
527 * Compressed clusters are always returned one by one.
529 * Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error
532 int qcow2_get_cluster_offset(BlockDriverState
*bs
, uint64_t offset
,
533 unsigned int *bytes
, uint64_t *cluster_offset
)
535 BDRVQcow2State
*s
= bs
->opaque
;
536 unsigned int l2_index
;
537 uint64_t l1_index
, l2_offset
, *l2_slice
;
539 unsigned int offset_in_cluster
;
540 uint64_t bytes_available
, bytes_needed
, nb_clusters
;
541 QCow2ClusterType type
;
544 offset_in_cluster
= offset_into_cluster(s
, offset
);
545 bytes_needed
= (uint64_t) *bytes
+ offset_in_cluster
;
547 /* compute how many bytes there are between the start of the cluster
548 * containing offset and the end of the l2 slice that contains
549 * the entry pointing to it */
551 ((uint64_t) (s
->l2_slice_size
- offset_to_l2_slice_index(s
, offset
)))
554 if (bytes_needed
> bytes_available
) {
555 bytes_needed
= bytes_available
;
560 /* seek to the l2 offset in the l1 table */
562 l1_index
= offset_to_l1_index(s
, offset
);
563 if (l1_index
>= s
->l1_size
) {
564 type
= QCOW2_CLUSTER_UNALLOCATED
;
568 l2_offset
= s
->l1_table
[l1_index
] & L1E_OFFSET_MASK
;
570 type
= QCOW2_CLUSTER_UNALLOCATED
;
574 if (offset_into_cluster(s
, l2_offset
)) {
575 qcow2_signal_corruption(bs
, true, -1, -1, "L2 table offset %#" PRIx64
576 " unaligned (L1 index: %#" PRIx64
")",
577 l2_offset
, l1_index
);
581 /* load the l2 slice in memory */
583 ret
= l2_load(bs
, offset
, l2_offset
, &l2_slice
);
588 /* find the cluster offset for the given disk offset */
590 l2_index
= offset_to_l2_slice_index(s
, offset
);
591 *cluster_offset
= be64_to_cpu(l2_slice
[l2_index
]);
593 nb_clusters
= size_to_clusters(s
, bytes_needed
);
594 /* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned
595 * integers; the minimum cluster size is 512, so this assertion is always
597 assert(nb_clusters
<= INT_MAX
);
599 type
= qcow2_get_cluster_type(bs
, *cluster_offset
);
600 if (s
->qcow_version
< 3 && (type
== QCOW2_CLUSTER_ZERO_PLAIN
||
601 type
== QCOW2_CLUSTER_ZERO_ALLOC
)) {
602 qcow2_signal_corruption(bs
, true, -1, -1, "Zero cluster entry found"
603 " in pre-v3 image (L2 offset: %#" PRIx64
604 ", L2 index: %#x)", l2_offset
, l2_index
);
609 case QCOW2_CLUSTER_COMPRESSED
:
610 /* Compressed clusters can only be processed one by one */
612 *cluster_offset
&= L2E_COMPRESSED_OFFSET_SIZE_MASK
;
614 case QCOW2_CLUSTER_ZERO_PLAIN
:
615 case QCOW2_CLUSTER_UNALLOCATED
:
616 /* how many empty clusters ? */
617 c
= count_contiguous_clusters_unallocated(bs
, nb_clusters
,
618 &l2_slice
[l2_index
], type
);
621 case QCOW2_CLUSTER_ZERO_ALLOC
:
622 case QCOW2_CLUSTER_NORMAL
:
623 /* how many allocated clusters ? */
624 c
= count_contiguous_clusters(bs
, nb_clusters
, s
->cluster_size
,
625 &l2_slice
[l2_index
], QCOW_OFLAG_ZERO
);
626 *cluster_offset
&= L2E_OFFSET_MASK
;
627 if (offset_into_cluster(s
, *cluster_offset
)) {
628 qcow2_signal_corruption(bs
, true, -1, -1,
629 "Cluster allocation offset %#"
630 PRIx64
" unaligned (L2 offset: %#" PRIx64
631 ", L2 index: %#x)", *cluster_offset
,
632 l2_offset
, l2_index
);
641 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
643 bytes_available
= (int64_t)c
* s
->cluster_size
;
646 if (bytes_available
> bytes_needed
) {
647 bytes_available
= bytes_needed
;
650 /* bytes_available <= bytes_needed <= *bytes + offset_in_cluster;
651 * subtracting offset_in_cluster will therefore definitely yield something
652 * not exceeding UINT_MAX */
653 assert(bytes_available
- offset_in_cluster
<= UINT_MAX
);
654 *bytes
= bytes_available
- offset_in_cluster
;
659 qcow2_cache_put(s
->l2_table_cache
, (void **)&l2_slice
);
666 * for a given disk offset, load (and allocate if needed)
667 * the appropriate slice of its l2 table.
669 * the cluster index in the l2 slice is given to the caller.
671 * Returns 0 on success, -errno in failure case
673 static int get_cluster_table(BlockDriverState
*bs
, uint64_t offset
,
674 uint64_t **new_l2_slice
,
677 BDRVQcow2State
*s
= bs
->opaque
;
678 unsigned int l2_index
;
679 uint64_t l1_index
, l2_offset
;
680 uint64_t *l2_slice
= NULL
;
683 /* seek to the l2 offset in the l1 table */
685 l1_index
= offset_to_l1_index(s
, offset
);
686 if (l1_index
>= s
->l1_size
) {
687 ret
= qcow2_grow_l1_table(bs
, l1_index
+ 1, false);
693 assert(l1_index
< s
->l1_size
);
694 l2_offset
= s
->l1_table
[l1_index
] & L1E_OFFSET_MASK
;
695 if (offset_into_cluster(s
, l2_offset
)) {
696 qcow2_signal_corruption(bs
, true, -1, -1, "L2 table offset %#" PRIx64
697 " unaligned (L1 index: %#" PRIx64
")",
698 l2_offset
, l1_index
);
702 if (!(s
->l1_table
[l1_index
] & QCOW_OFLAG_COPIED
)) {
703 /* First allocate a new L2 table (and do COW if needed) */
704 ret
= l2_allocate(bs
, l1_index
);
709 /* Then decrease the refcount of the old table */
711 qcow2_free_clusters(bs
, l2_offset
, s
->l2_size
* sizeof(uint64_t),
712 QCOW2_DISCARD_OTHER
);
715 /* Get the offset of the newly-allocated l2 table */
716 l2_offset
= s
->l1_table
[l1_index
] & L1E_OFFSET_MASK
;
717 assert(offset_into_cluster(s
, l2_offset
) == 0);
720 /* load the l2 slice in memory */
721 ret
= l2_load(bs
, offset
, l2_offset
, &l2_slice
);
726 /* find the cluster offset for the given disk offset */
728 l2_index
= offset_to_l2_slice_index(s
, offset
);
730 *new_l2_slice
= l2_slice
;
731 *new_l2_index
= l2_index
;
737 * alloc_compressed_cluster_offset
739 * For a given offset of the disk image, return cluster offset in
742 * If the offset is not found, allocate a new compressed cluster.
744 * Return the cluster offset if successful,
745 * Return 0, otherwise.
749 uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState
*bs
,
753 BDRVQcow2State
*s
= bs
->opaque
;
756 int64_t cluster_offset
;
759 ret
= get_cluster_table(bs
, offset
, &l2_slice
, &l2_index
);
764 /* Compression can't overwrite anything. Fail if the cluster was already
766 cluster_offset
= be64_to_cpu(l2_slice
[l2_index
]);
767 if (cluster_offset
& L2E_OFFSET_MASK
) {
768 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
772 cluster_offset
= qcow2_alloc_bytes(bs
, compressed_size
);
773 if (cluster_offset
< 0) {
774 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
778 nb_csectors
= ((cluster_offset
+ compressed_size
- 1) >> 9) -
779 (cluster_offset
>> 9);
781 cluster_offset
|= QCOW_OFLAG_COMPRESSED
|
782 ((uint64_t)nb_csectors
<< s
->csize_shift
);
784 /* update L2 table */
786 /* compressed clusters never have the copied flag */
788 BLKDBG_EVENT(bs
->file
, BLKDBG_L2_UPDATE_COMPRESSED
);
789 qcow2_cache_entry_mark_dirty(s
->l2_table_cache
, l2_slice
);
790 l2_slice
[l2_index
] = cpu_to_be64(cluster_offset
);
791 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
793 return cluster_offset
;
796 static int perform_cow(BlockDriverState
*bs
, QCowL2Meta
*m
)
798 BDRVQcow2State
*s
= bs
->opaque
;
799 Qcow2COWRegion
*start
= &m
->cow_start
;
800 Qcow2COWRegion
*end
= &m
->cow_end
;
801 unsigned buffer_size
;
802 unsigned data_bytes
= end
->offset
- (start
->offset
+ start
->nb_bytes
);
804 uint8_t *start_buffer
, *end_buffer
;
808 assert(start
->nb_bytes
<= UINT_MAX
- end
->nb_bytes
);
809 assert(start
->nb_bytes
+ end
->nb_bytes
<= UINT_MAX
- data_bytes
);
810 assert(start
->offset
+ start
->nb_bytes
<= end
->offset
);
811 assert(!m
->data_qiov
|| m
->data_qiov
->size
== data_bytes
);
813 if (start
->nb_bytes
== 0 && end
->nb_bytes
== 0) {
817 /* If we have to read both the start and end COW regions and the
818 * middle region is not too large then perform just one read
820 merge_reads
= start
->nb_bytes
&& end
->nb_bytes
&& data_bytes
<= 16384;
822 buffer_size
= start
->nb_bytes
+ data_bytes
+ end
->nb_bytes
;
824 /* If we have to do two reads, add some padding in the middle
825 * if necessary to make sure that the end region is optimally
827 size_t align
= bdrv_opt_mem_align(bs
);
828 assert(align
> 0 && align
<= UINT_MAX
);
829 assert(QEMU_ALIGN_UP(start
->nb_bytes
, align
) <=
830 UINT_MAX
- end
->nb_bytes
);
831 buffer_size
= QEMU_ALIGN_UP(start
->nb_bytes
, align
) + end
->nb_bytes
;
834 /* Reserve a buffer large enough to store all the data that we're
836 start_buffer
= qemu_try_blockalign(bs
, buffer_size
);
837 if (start_buffer
== NULL
) {
840 /* The part of the buffer where the end region is located */
841 end_buffer
= start_buffer
+ buffer_size
- end
->nb_bytes
;
843 qemu_iovec_init(&qiov
, 2 + (m
->data_qiov
? m
->data_qiov
->niov
: 0));
845 qemu_co_mutex_unlock(&s
->lock
);
846 /* First we read the existing data from both COW regions. We
847 * either read the whole region in one go, or the start and end
848 * regions separately. */
850 qemu_iovec_add(&qiov
, start_buffer
, buffer_size
);
851 ret
= do_perform_cow_read(bs
, m
->offset
, start
->offset
, &qiov
);
853 qemu_iovec_add(&qiov
, start_buffer
, start
->nb_bytes
);
854 ret
= do_perform_cow_read(bs
, m
->offset
, start
->offset
, &qiov
);
859 qemu_iovec_reset(&qiov
);
860 qemu_iovec_add(&qiov
, end_buffer
, end
->nb_bytes
);
861 ret
= do_perform_cow_read(bs
, m
->offset
, end
->offset
, &qiov
);
867 /* Encrypt the data if necessary before writing it */
869 if (!do_perform_cow_encrypt(bs
, m
->offset
, m
->alloc_offset
,
870 start
->offset
, start_buffer
,
872 !do_perform_cow_encrypt(bs
, m
->offset
, m
->alloc_offset
,
873 end
->offset
, end_buffer
, end
->nb_bytes
)) {
879 /* And now we can write everything. If we have the guest data we
880 * can write everything in one single operation */
882 qemu_iovec_reset(&qiov
);
883 if (start
->nb_bytes
) {
884 qemu_iovec_add(&qiov
, start_buffer
, start
->nb_bytes
);
886 qemu_iovec_concat(&qiov
, m
->data_qiov
, 0, data_bytes
);
888 qemu_iovec_add(&qiov
, end_buffer
, end
->nb_bytes
);
890 /* NOTE: we have a write_aio blkdebug event here followed by
891 * a cow_write one in do_perform_cow_write(), but there's only
892 * one single I/O operation */
893 BLKDBG_EVENT(bs
->file
, BLKDBG_WRITE_AIO
);
894 ret
= do_perform_cow_write(bs
, m
->alloc_offset
, start
->offset
, &qiov
);
896 /* If there's no guest data then write both COW regions separately */
897 qemu_iovec_reset(&qiov
);
898 qemu_iovec_add(&qiov
, start_buffer
, start
->nb_bytes
);
899 ret
= do_perform_cow_write(bs
, m
->alloc_offset
, start
->offset
, &qiov
);
904 qemu_iovec_reset(&qiov
);
905 qemu_iovec_add(&qiov
, end_buffer
, end
->nb_bytes
);
906 ret
= do_perform_cow_write(bs
, m
->alloc_offset
, end
->offset
, &qiov
);
910 qemu_co_mutex_lock(&s
->lock
);
913 * Before we update the L2 table to actually point to the new cluster, we
914 * need to be sure that the refcounts have been increased and COW was
918 qcow2_cache_depends_on_flush(s
->l2_table_cache
);
921 qemu_vfree(start_buffer
);
922 qemu_iovec_destroy(&qiov
);
926 int qcow2_alloc_cluster_link_l2(BlockDriverState
*bs
, QCowL2Meta
*m
)
928 BDRVQcow2State
*s
= bs
->opaque
;
929 int i
, j
= 0, l2_index
, ret
;
930 uint64_t *old_cluster
, *l2_slice
;
931 uint64_t cluster_offset
= m
->alloc_offset
;
933 trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m
->nb_clusters
);
934 assert(m
->nb_clusters
> 0);
936 old_cluster
= g_try_new(uint64_t, m
->nb_clusters
);
937 if (old_cluster
== NULL
) {
942 /* copy content of unmodified sectors */
943 ret
= perform_cow(bs
, m
);
948 /* Update L2 table. */
949 if (s
->use_lazy_refcounts
) {
950 qcow2_mark_dirty(bs
);
952 if (qcow2_need_accurate_refcounts(s
)) {
953 qcow2_cache_set_dependency(bs
, s
->l2_table_cache
,
954 s
->refcount_block_cache
);
957 ret
= get_cluster_table(bs
, m
->offset
, &l2_slice
, &l2_index
);
961 qcow2_cache_entry_mark_dirty(s
->l2_table_cache
, l2_slice
);
963 assert(l2_index
+ m
->nb_clusters
<= s
->l2_slice_size
);
964 for (i
= 0; i
< m
->nb_clusters
; i
++) {
965 /* if two concurrent writes happen to the same unallocated cluster
966 * each write allocates separate cluster and writes data concurrently.
967 * The first one to complete updates l2 table with pointer to its
968 * cluster the second one has to do RMW (which is done above by
969 * perform_cow()), update l2 table with its cluster pointer and free
970 * old cluster. This is what this loop does */
971 if (l2_slice
[l2_index
+ i
] != 0) {
972 old_cluster
[j
++] = l2_slice
[l2_index
+ i
];
975 l2_slice
[l2_index
+ i
] = cpu_to_be64((cluster_offset
+
976 (i
<< s
->cluster_bits
)) | QCOW_OFLAG_COPIED
);
980 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
983 * If this was a COW, we need to decrease the refcount of the old cluster.
985 * Don't discard clusters that reach a refcount of 0 (e.g. compressed
986 * clusters), the next write will reuse them anyway.
988 if (!m
->keep_old_clusters
&& j
!= 0) {
989 for (i
= 0; i
< j
; i
++) {
990 qcow2_free_any_clusters(bs
, be64_to_cpu(old_cluster
[i
]), 1,
991 QCOW2_DISCARD_NEVER
);
1002 * Frees the allocated clusters because the request failed and they won't
1003 * actually be linked.
1005 void qcow2_alloc_cluster_abort(BlockDriverState
*bs
, QCowL2Meta
*m
)
1007 BDRVQcow2State
*s
= bs
->opaque
;
1008 qcow2_free_clusters(bs
, m
->alloc_offset
, m
->nb_clusters
<< s
->cluster_bits
,
1009 QCOW2_DISCARD_NEVER
);
1013 * Returns the number of contiguous clusters that can be used for an allocating
1014 * write, but require COW to be performed (this includes yet unallocated space,
1015 * which must copy from the backing file)
1017 static int count_cow_clusters(BlockDriverState
*bs
, int nb_clusters
,
1018 uint64_t *l2_slice
, int l2_index
)
1022 for (i
= 0; i
< nb_clusters
; i
++) {
1023 uint64_t l2_entry
= be64_to_cpu(l2_slice
[l2_index
+ i
]);
1024 QCow2ClusterType cluster_type
= qcow2_get_cluster_type(bs
, l2_entry
);
1026 switch(cluster_type
) {
1027 case QCOW2_CLUSTER_NORMAL
:
1028 if (l2_entry
& QCOW_OFLAG_COPIED
) {
1032 case QCOW2_CLUSTER_UNALLOCATED
:
1033 case QCOW2_CLUSTER_COMPRESSED
:
1034 case QCOW2_CLUSTER_ZERO_PLAIN
:
1035 case QCOW2_CLUSTER_ZERO_ALLOC
:
1043 assert(i
<= nb_clusters
);
1048 * Check if there already is an AIO write request in flight which allocates
1049 * the same cluster. In this case we need to wait until the previous
1050 * request has completed and updated the L2 table accordingly.
1053 * 0 if there was no dependency. *cur_bytes indicates the number of
1054 * bytes from guest_offset that can be read before the next
1055 * dependency must be processed (or the request is complete)
1057 * -EAGAIN if we had to wait for another request, previously gathered
1058 * information on cluster allocation may be invalid now. The caller
1059 * must start over anyway, so consider *cur_bytes undefined.
1061 static int handle_dependencies(BlockDriverState
*bs
, uint64_t guest_offset
,
1062 uint64_t *cur_bytes
, QCowL2Meta
**m
)
1064 BDRVQcow2State
*s
= bs
->opaque
;
1065 QCowL2Meta
*old_alloc
;
1066 uint64_t bytes
= *cur_bytes
;
1068 QLIST_FOREACH(old_alloc
, &s
->cluster_allocs
, next_in_flight
) {
1070 uint64_t start
= guest_offset
;
1071 uint64_t end
= start
+ bytes
;
1072 uint64_t old_start
= l2meta_cow_start(old_alloc
);
1073 uint64_t old_end
= l2meta_cow_end(old_alloc
);
1075 if (end
<= old_start
|| start
>= old_end
) {
1076 /* No intersection */
1078 if (start
< old_start
) {
1079 /* Stop at the start of a running allocation */
1080 bytes
= old_start
- start
;
1085 /* Stop if already an l2meta exists. After yielding, it wouldn't
1086 * be valid any more, so we'd have to clean up the old L2Metas
1087 * and deal with requests depending on them before starting to
1088 * gather new ones. Not worth the trouble. */
1089 if (bytes
== 0 && *m
) {
1095 /* Wait for the dependency to complete. We need to recheck
1096 * the free/allocated clusters when we continue. */
1097 qemu_co_queue_wait(&old_alloc
->dependent_requests
, &s
->lock
);
1103 /* Make sure that existing clusters and new allocations are only used up to
1104 * the next dependency if we shortened the request above */
1111 * Checks how many already allocated clusters that don't require a copy on
1112 * write there are at the given guest_offset (up to *bytes). If
1113 * *host_offset is not zero, only physically contiguous clusters beginning at
1114 * this host offset are counted.
1116 * Note that guest_offset may not be cluster aligned. In this case, the
1117 * returned *host_offset points to exact byte referenced by guest_offset and
1118 * therefore isn't cluster aligned as well.
1121 * 0: if no allocated clusters are available at the given offset.
1122 * *bytes is normally unchanged. It is set to 0 if the cluster
1123 * is allocated and doesn't need COW, but doesn't have the right
1126 * 1: if allocated clusters that don't require a COW are available at
1127 * the requested offset. *bytes may have decreased and describes
1128 * the length of the area that can be written to.
1130 * -errno: in error cases
1132 static int handle_copied(BlockDriverState
*bs
, uint64_t guest_offset
,
1133 uint64_t *host_offset
, uint64_t *bytes
, QCowL2Meta
**m
)
1135 BDRVQcow2State
*s
= bs
->opaque
;
1137 uint64_t cluster_offset
;
1139 uint64_t nb_clusters
;
1140 unsigned int keep_clusters
;
1143 trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset
, *host_offset
,
1146 assert(*host_offset
== 0 || offset_into_cluster(s
, guest_offset
)
1147 == offset_into_cluster(s
, *host_offset
));
1150 * Calculate the number of clusters to look for. We stop at L2 slice
1151 * boundaries to keep things simple.
1154 size_to_clusters(s
, offset_into_cluster(s
, guest_offset
) + *bytes
);
1156 l2_index
= offset_to_l2_slice_index(s
, guest_offset
);
1157 nb_clusters
= MIN(nb_clusters
, s
->l2_slice_size
- l2_index
);
1158 assert(nb_clusters
<= INT_MAX
);
1160 /* Find L2 entry for the first involved cluster */
1161 ret
= get_cluster_table(bs
, guest_offset
, &l2_slice
, &l2_index
);
1166 cluster_offset
= be64_to_cpu(l2_slice
[l2_index
]);
1168 /* Check how many clusters are already allocated and don't need COW */
1169 if (qcow2_get_cluster_type(bs
, cluster_offset
) == QCOW2_CLUSTER_NORMAL
1170 && (cluster_offset
& QCOW_OFLAG_COPIED
))
1172 /* If a specific host_offset is required, check it */
1173 bool offset_matches
=
1174 (cluster_offset
& L2E_OFFSET_MASK
) == *host_offset
;
1176 if (offset_into_cluster(s
, cluster_offset
& L2E_OFFSET_MASK
)) {
1177 qcow2_signal_corruption(bs
, true, -1, -1, "Data cluster offset "
1178 "%#llx unaligned (guest offset: %#" PRIx64
1179 ")", cluster_offset
& L2E_OFFSET_MASK
,
1185 if (*host_offset
!= 0 && !offset_matches
) {
1191 /* We keep all QCOW_OFLAG_COPIED clusters */
1193 count_contiguous_clusters(bs
, nb_clusters
, s
->cluster_size
,
1194 &l2_slice
[l2_index
],
1195 QCOW_OFLAG_COPIED
| QCOW_OFLAG_ZERO
);
1196 assert(keep_clusters
<= nb_clusters
);
1198 *bytes
= MIN(*bytes
,
1199 keep_clusters
* s
->cluster_size
1200 - offset_into_cluster(s
, guest_offset
));
1209 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
1211 /* Only return a host offset if we actually made progress. Otherwise we
1212 * would make requirements for handle_alloc() that it can't fulfill */
1214 *host_offset
= (cluster_offset
& L2E_OFFSET_MASK
)
1215 + offset_into_cluster(s
, guest_offset
);
1222 * Allocates new clusters for the given guest_offset.
1224 * At most *nb_clusters are allocated, and on return *nb_clusters is updated to
1225 * contain the number of clusters that have been allocated and are contiguous
1226 * in the image file.
1228 * If *host_offset is non-zero, it specifies the offset in the image file at
1229 * which the new clusters must start. *nb_clusters can be 0 on return in this
1230 * case if the cluster at host_offset is already in use. If *host_offset is
1231 * zero, the clusters can be allocated anywhere in the image file.
1233 * *host_offset is updated to contain the offset into the image file at which
1234 * the first allocated cluster starts.
1236 * Return 0 on success and -errno in error cases. -EAGAIN means that the
1237 * function has been waiting for another request and the allocation must be
1238 * restarted, but the whole request should not be failed.
1240 static int do_alloc_cluster_offset(BlockDriverState
*bs
, uint64_t guest_offset
,
1241 uint64_t *host_offset
, uint64_t *nb_clusters
)
1243 BDRVQcow2State
*s
= bs
->opaque
;
1245 trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset
,
1246 *host_offset
, *nb_clusters
);
1248 /* Allocate new clusters */
1249 trace_qcow2_cluster_alloc_phys(qemu_coroutine_self());
1250 if (*host_offset
== 0) {
1251 int64_t cluster_offset
=
1252 qcow2_alloc_clusters(bs
, *nb_clusters
* s
->cluster_size
);
1253 if (cluster_offset
< 0) {
1254 return cluster_offset
;
1256 *host_offset
= cluster_offset
;
1259 int64_t ret
= qcow2_alloc_clusters_at(bs
, *host_offset
, *nb_clusters
);
1269 * Allocates new clusters for an area that either is yet unallocated or needs a
1270 * copy on write. If *host_offset is non-zero, clusters are only allocated if
1271 * the new allocation can match the specified host offset.
1273 * Note that guest_offset may not be cluster aligned. In this case, the
1274 * returned *host_offset points to exact byte referenced by guest_offset and
1275 * therefore isn't cluster aligned as well.
1278 * 0: if no clusters could be allocated. *bytes is set to 0,
1279 * *host_offset is left unchanged.
1281 * 1: if new clusters were allocated. *bytes may be decreased if the
1282 * new allocation doesn't cover all of the requested area.
1283 * *host_offset is updated to contain the host offset of the first
1284 * newly allocated cluster.
1286 * -errno: in error cases
1288 static int handle_alloc(BlockDriverState
*bs
, uint64_t guest_offset
,
1289 uint64_t *host_offset
, uint64_t *bytes
, QCowL2Meta
**m
)
1291 BDRVQcow2State
*s
= bs
->opaque
;
1295 uint64_t nb_clusters
;
1297 bool keep_old_clusters
= false;
1299 uint64_t alloc_cluster_offset
= 0;
1301 trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset
, *host_offset
,
1306 * Calculate the number of clusters to look for. We stop at L2 slice
1307 * boundaries to keep things simple.
1310 size_to_clusters(s
, offset_into_cluster(s
, guest_offset
) + *bytes
);
1312 l2_index
= offset_to_l2_slice_index(s
, guest_offset
);
1313 nb_clusters
= MIN(nb_clusters
, s
->l2_slice_size
- l2_index
);
1314 assert(nb_clusters
<= INT_MAX
);
1316 /* Find L2 entry for the first involved cluster */
1317 ret
= get_cluster_table(bs
, guest_offset
, &l2_slice
, &l2_index
);
1322 entry
= be64_to_cpu(l2_slice
[l2_index
]);
1324 /* For the moment, overwrite compressed clusters one by one */
1325 if (entry
& QCOW_OFLAG_COMPRESSED
) {
1328 nb_clusters
= count_cow_clusters(bs
, nb_clusters
, l2_slice
, l2_index
);
1331 /* This function is only called when there were no non-COW clusters, so if
1332 * we can't find any unallocated or COW clusters either, something is
1333 * wrong with our code. */
1334 assert(nb_clusters
> 0);
1336 if (qcow2_get_cluster_type(bs
, entry
) == QCOW2_CLUSTER_ZERO_ALLOC
&&
1337 (entry
& QCOW_OFLAG_COPIED
) &&
1339 start_of_cluster(s
, *host_offset
) == (entry
& L2E_OFFSET_MASK
)))
1341 int preallocated_nb_clusters
;
1343 if (offset_into_cluster(s
, entry
& L2E_OFFSET_MASK
)) {
1344 qcow2_signal_corruption(bs
, true, -1, -1, "Preallocated zero "
1345 "cluster offset %#llx unaligned (guest "
1346 "offset: %#" PRIx64
")",
1347 entry
& L2E_OFFSET_MASK
, guest_offset
);
1352 /* Try to reuse preallocated zero clusters; contiguous normal clusters
1353 * would be fine, too, but count_cow_clusters() above has limited
1354 * nb_clusters already to a range of COW clusters */
1355 preallocated_nb_clusters
=
1356 count_contiguous_clusters(bs
, nb_clusters
, s
->cluster_size
,
1357 &l2_slice
[l2_index
], QCOW_OFLAG_COPIED
);
1358 assert(preallocated_nb_clusters
> 0);
1360 nb_clusters
= preallocated_nb_clusters
;
1361 alloc_cluster_offset
= entry
& L2E_OFFSET_MASK
;
1363 /* We want to reuse these clusters, so qcow2_alloc_cluster_link_l2()
1364 * should not free them. */
1365 keep_old_clusters
= true;
1368 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
1370 if (!alloc_cluster_offset
) {
1371 /* Allocate, if necessary at a given offset in the image file */
1372 alloc_cluster_offset
= start_of_cluster(s
, *host_offset
);
1373 ret
= do_alloc_cluster_offset(bs
, guest_offset
, &alloc_cluster_offset
,
1379 /* Can't extend contiguous allocation */
1380 if (nb_clusters
== 0) {
1385 /* !*host_offset would overwrite the image header and is reserved for
1386 * "no host offset preferred". If 0 was a valid host offset, it'd
1387 * trigger the following overlap check; do that now to avoid having an
1388 * invalid value in *host_offset. */
1389 if (!alloc_cluster_offset
) {
1390 ret
= qcow2_pre_write_overlap_check(bs
, 0, alloc_cluster_offset
,
1391 nb_clusters
* s
->cluster_size
);
1398 * Save info needed for meta data update.
1400 * requested_bytes: Number of bytes from the start of the first
1401 * newly allocated cluster to the end of the (possibly shortened
1402 * before) write request.
1404 * avail_bytes: Number of bytes from the start of the first
1405 * newly allocated to the end of the last newly allocated cluster.
1407 * nb_bytes: The number of bytes from the start of the first
1408 * newly allocated cluster to the end of the area that the write
1409 * request actually writes to (excluding COW at the end)
1411 uint64_t requested_bytes
= *bytes
+ offset_into_cluster(s
, guest_offset
);
1412 int avail_bytes
= MIN(INT_MAX
, nb_clusters
<< s
->cluster_bits
);
1413 int nb_bytes
= MIN(requested_bytes
, avail_bytes
);
1414 QCowL2Meta
*old_m
= *m
;
1416 *m
= g_malloc0(sizeof(**m
));
1418 **m
= (QCowL2Meta
) {
1421 .alloc_offset
= alloc_cluster_offset
,
1422 .offset
= start_of_cluster(s
, guest_offset
),
1423 .nb_clusters
= nb_clusters
,
1425 .keep_old_clusters
= keep_old_clusters
,
1429 .nb_bytes
= offset_into_cluster(s
, guest_offset
),
1433 .nb_bytes
= avail_bytes
- nb_bytes
,
1436 qemu_co_queue_init(&(*m
)->dependent_requests
);
1437 QLIST_INSERT_HEAD(&s
->cluster_allocs
, *m
, next_in_flight
);
1439 *host_offset
= alloc_cluster_offset
+ offset_into_cluster(s
, guest_offset
);
1440 *bytes
= MIN(*bytes
, nb_bytes
- offset_into_cluster(s
, guest_offset
));
1441 assert(*bytes
!= 0);
1446 if (*m
&& (*m
)->nb_clusters
> 0) {
1447 QLIST_REMOVE(*m
, next_in_flight
);
1453 * alloc_cluster_offset
1455 * For a given offset on the virtual disk, find the cluster offset in qcow2
1456 * file. If the offset is not found, allocate a new cluster.
1458 * If the cluster was already allocated, m->nb_clusters is set to 0 and
1459 * other fields in m are meaningless.
1461 * If the cluster is newly allocated, m->nb_clusters is set to the number of
1462 * contiguous clusters that have been allocated. In this case, the other
1463 * fields of m are valid and contain information about the first allocated
1466 * If the request conflicts with another write request in flight, the coroutine
1467 * is queued and will be reentered when the dependency has completed.
1469 * Return 0 on success and -errno in error cases
1471 int qcow2_alloc_cluster_offset(BlockDriverState
*bs
, uint64_t offset
,
1472 unsigned int *bytes
, uint64_t *host_offset
,
1475 BDRVQcow2State
*s
= bs
->opaque
;
1476 uint64_t start
, remaining
;
1477 uint64_t cluster_offset
;
1481 trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset
, *bytes
);
1493 if (!*host_offset
) {
1494 *host_offset
= start_of_cluster(s
, cluster_offset
);
1497 assert(remaining
>= cur_bytes
);
1500 remaining
-= cur_bytes
;
1501 cluster_offset
+= cur_bytes
;
1503 if (remaining
== 0) {
1507 cur_bytes
= remaining
;
1510 * Now start gathering as many contiguous clusters as possible:
1512 * 1. Check for overlaps with in-flight allocations
1514 * a) Overlap not in the first cluster -> shorten this request and
1515 * let the caller handle the rest in its next loop iteration.
1517 * b) Real overlaps of two requests. Yield and restart the search
1518 * for contiguous clusters (the situation could have changed
1519 * while we were sleeping)
1521 * c) TODO: Request starts in the same cluster as the in-flight
1522 * allocation ends. Shorten the COW of the in-fight allocation,
1523 * set cluster_offset to write to the same cluster and set up
1524 * the right synchronisation between the in-flight request and
1527 ret
= handle_dependencies(bs
, start
, &cur_bytes
, m
);
1528 if (ret
== -EAGAIN
) {
1529 /* Currently handle_dependencies() doesn't yield if we already had
1530 * an allocation. If it did, we would have to clean up the L2Meta
1531 * structs before starting over. */
1534 } else if (ret
< 0) {
1536 } else if (cur_bytes
== 0) {
1539 /* handle_dependencies() may have decreased cur_bytes (shortened
1540 * the allocations below) so that the next dependency is processed
1541 * correctly during the next loop iteration. */
1545 * 2. Count contiguous COPIED clusters.
1547 ret
= handle_copied(bs
, start
, &cluster_offset
, &cur_bytes
, m
);
1552 } else if (cur_bytes
== 0) {
1557 * 3. If the request still hasn't completed, allocate new clusters,
1558 * considering any cluster_offset of steps 1c or 2.
1560 ret
= handle_alloc(bs
, start
, &cluster_offset
, &cur_bytes
, m
);
1566 assert(cur_bytes
== 0);
1571 *bytes
-= remaining
;
1573 assert(*host_offset
!= 0);
1579 * This discards as many clusters of nb_clusters as possible at once (i.e.
1580 * all clusters in the same L2 slice) and returns the number of discarded
1583 static int discard_in_l2_slice(BlockDriverState
*bs
, uint64_t offset
,
1584 uint64_t nb_clusters
,
1585 enum qcow2_discard_type type
, bool full_discard
)
1587 BDRVQcow2State
*s
= bs
->opaque
;
1593 ret
= get_cluster_table(bs
, offset
, &l2_slice
, &l2_index
);
1598 /* Limit nb_clusters to one L2 slice */
1599 nb_clusters
= MIN(nb_clusters
, s
->l2_slice_size
- l2_index
);
1600 assert(nb_clusters
<= INT_MAX
);
1602 for (i
= 0; i
< nb_clusters
; i
++) {
1603 uint64_t old_l2_entry
;
1605 old_l2_entry
= be64_to_cpu(l2_slice
[l2_index
+ i
]);
1608 * If full_discard is false, make sure that a discarded area reads back
1609 * as zeroes for v3 images (we cannot do it for v2 without actually
1610 * writing a zero-filled buffer). We can skip the operation if the
1611 * cluster is already marked as zero, or if it's unallocated and we
1612 * don't have a backing file.
1614 * TODO We might want to use bdrv_block_status(bs) here, but we're
1615 * holding s->lock, so that doesn't work today.
1617 * If full_discard is true, the sector should not read back as zeroes,
1618 * but rather fall through to the backing file.
1620 switch (qcow2_get_cluster_type(bs
, old_l2_entry
)) {
1621 case QCOW2_CLUSTER_UNALLOCATED
:
1622 if (full_discard
|| !bs
->backing
) {
1627 case QCOW2_CLUSTER_ZERO_PLAIN
:
1628 if (!full_discard
) {
1633 case QCOW2_CLUSTER_ZERO_ALLOC
:
1634 case QCOW2_CLUSTER_NORMAL
:
1635 case QCOW2_CLUSTER_COMPRESSED
:
1642 /* First remove L2 entries */
1643 qcow2_cache_entry_mark_dirty(s
->l2_table_cache
, l2_slice
);
1644 if (!full_discard
&& s
->qcow_version
>= 3) {
1645 l2_slice
[l2_index
+ i
] = cpu_to_be64(QCOW_OFLAG_ZERO
);
1647 l2_slice
[l2_index
+ i
] = cpu_to_be64(0);
1650 /* Then decrease the refcount */
1651 qcow2_free_any_clusters(bs
, old_l2_entry
, 1, type
);
1654 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
1659 int qcow2_cluster_discard(BlockDriverState
*bs
, uint64_t offset
,
1660 uint64_t bytes
, enum qcow2_discard_type type
,
1663 BDRVQcow2State
*s
= bs
->opaque
;
1664 uint64_t end_offset
= offset
+ bytes
;
1665 uint64_t nb_clusters
;
1669 /* Caller must pass aligned values, except at image end */
1670 assert(QEMU_IS_ALIGNED(offset
, s
->cluster_size
));
1671 assert(QEMU_IS_ALIGNED(end_offset
, s
->cluster_size
) ||
1672 end_offset
== bs
->total_sectors
<< BDRV_SECTOR_BITS
);
1674 nb_clusters
= size_to_clusters(s
, bytes
);
1676 s
->cache_discards
= true;
1678 /* Each L2 slice is handled by its own loop iteration */
1679 while (nb_clusters
> 0) {
1680 cleared
= discard_in_l2_slice(bs
, offset
, nb_clusters
, type
,
1687 nb_clusters
-= cleared
;
1688 offset
+= (cleared
* s
->cluster_size
);
1693 s
->cache_discards
= false;
1694 qcow2_process_discards(bs
, ret
);
1700 * This zeroes as many clusters of nb_clusters as possible at once (i.e.
1701 * all clusters in the same L2 slice) and returns the number of zeroed
1704 static int zero_in_l2_slice(BlockDriverState
*bs
, uint64_t offset
,
1705 uint64_t nb_clusters
, int flags
)
1707 BDRVQcow2State
*s
= bs
->opaque
;
1712 bool unmap
= !!(flags
& BDRV_REQ_MAY_UNMAP
);
1714 ret
= get_cluster_table(bs
, offset
, &l2_slice
, &l2_index
);
1719 /* Limit nb_clusters to one L2 slice */
1720 nb_clusters
= MIN(nb_clusters
, s
->l2_slice_size
- l2_index
);
1721 assert(nb_clusters
<= INT_MAX
);
1723 for (i
= 0; i
< nb_clusters
; i
++) {
1724 uint64_t old_offset
;
1725 QCow2ClusterType cluster_type
;
1727 old_offset
= be64_to_cpu(l2_slice
[l2_index
+ i
]);
1730 * Minimize L2 changes if the cluster already reads back as
1731 * zeroes with correct allocation.
1733 cluster_type
= qcow2_get_cluster_type(bs
, old_offset
);
1734 if (cluster_type
== QCOW2_CLUSTER_ZERO_PLAIN
||
1735 (cluster_type
== QCOW2_CLUSTER_ZERO_ALLOC
&& !unmap
)) {
1739 qcow2_cache_entry_mark_dirty(s
->l2_table_cache
, l2_slice
);
1740 if (cluster_type
== QCOW2_CLUSTER_COMPRESSED
|| unmap
) {
1741 l2_slice
[l2_index
+ i
] = cpu_to_be64(QCOW_OFLAG_ZERO
);
1742 qcow2_free_any_clusters(bs
, old_offset
, 1, QCOW2_DISCARD_REQUEST
);
1744 l2_slice
[l2_index
+ i
] |= cpu_to_be64(QCOW_OFLAG_ZERO
);
1748 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
1753 int qcow2_cluster_zeroize(BlockDriverState
*bs
, uint64_t offset
,
1754 uint64_t bytes
, int flags
)
1756 BDRVQcow2State
*s
= bs
->opaque
;
1757 uint64_t end_offset
= offset
+ bytes
;
1758 uint64_t nb_clusters
;
1762 /* Caller must pass aligned values, except at image end */
1763 assert(QEMU_IS_ALIGNED(offset
, s
->cluster_size
));
1764 assert(QEMU_IS_ALIGNED(end_offset
, s
->cluster_size
) ||
1765 end_offset
== bs
->total_sectors
<< BDRV_SECTOR_BITS
);
1767 /* The zero flag is only supported by version 3 and newer */
1768 if (s
->qcow_version
< 3) {
1772 /* Each L2 slice is handled by its own loop iteration */
1773 nb_clusters
= size_to_clusters(s
, bytes
);
1775 s
->cache_discards
= true;
1777 while (nb_clusters
> 0) {
1778 cleared
= zero_in_l2_slice(bs
, offset
, nb_clusters
, flags
);
1784 nb_clusters
-= cleared
;
1785 offset
+= (cleared
* s
->cluster_size
);
1790 s
->cache_discards
= false;
1791 qcow2_process_discards(bs
, ret
);
1797 * Expands all zero clusters in a specific L1 table (or deallocates them, for
1798 * non-backed non-pre-allocated zero clusters).
1800 * l1_entries and *visited_l1_entries are used to keep track of progress for
1801 * status_cb(). l1_entries contains the total number of L1 entries and
1802 * *visited_l1_entries counts all visited L1 entries.
1804 static int expand_zero_clusters_in_l1(BlockDriverState
*bs
, uint64_t *l1_table
,
1805 int l1_size
, int64_t *visited_l1_entries
,
1807 BlockDriverAmendStatusCB
*status_cb
,
1810 BDRVQcow2State
*s
= bs
->opaque
;
1811 bool is_active_l1
= (l1_table
== s
->l1_table
);
1812 uint64_t *l2_slice
= NULL
;
1813 unsigned slice
, slice_size2
, n_slices
;
1817 slice_size2
= s
->l2_slice_size
* sizeof(uint64_t);
1818 n_slices
= s
->cluster_size
/ slice_size2
;
1820 if (!is_active_l1
) {
1821 /* inactive L2 tables require a buffer to be stored in when loading
1823 l2_slice
= qemu_try_blockalign(bs
->file
->bs
, slice_size2
);
1824 if (l2_slice
== NULL
) {
1829 for (i
= 0; i
< l1_size
; i
++) {
1830 uint64_t l2_offset
= l1_table
[i
] & L1E_OFFSET_MASK
;
1831 uint64_t l2_refcount
;
1835 (*visited_l1_entries
)++;
1837 status_cb(bs
, *visited_l1_entries
, l1_entries
, cb_opaque
);
1842 if (offset_into_cluster(s
, l2_offset
)) {
1843 qcow2_signal_corruption(bs
, true, -1, -1, "L2 table offset %#"
1844 PRIx64
" unaligned (L1 index: %#x)",
1850 ret
= qcow2_get_refcount(bs
, l2_offset
>> s
->cluster_bits
,
1856 for (slice
= 0; slice
< n_slices
; slice
++) {
1857 uint64_t slice_offset
= l2_offset
+ slice
* slice_size2
;
1858 bool l2_dirty
= false;
1860 /* get active L2 tables from cache */
1861 ret
= qcow2_cache_get(bs
, s
->l2_table_cache
, slice_offset
,
1862 (void **)&l2_slice
);
1864 /* load inactive L2 tables from disk */
1865 ret
= bdrv_pread(bs
->file
, slice_offset
, l2_slice
, slice_size2
);
1871 for (j
= 0; j
< s
->l2_slice_size
; j
++) {
1872 uint64_t l2_entry
= be64_to_cpu(l2_slice
[j
]);
1873 int64_t offset
= l2_entry
& L2E_OFFSET_MASK
;
1874 QCow2ClusterType cluster_type
=
1875 qcow2_get_cluster_type(bs
, l2_entry
);
1877 if (cluster_type
!= QCOW2_CLUSTER_ZERO_PLAIN
&&
1878 cluster_type
!= QCOW2_CLUSTER_ZERO_ALLOC
) {
1882 if (cluster_type
== QCOW2_CLUSTER_ZERO_PLAIN
) {
1884 /* not backed; therefore we can simply deallocate the
1891 offset
= qcow2_alloc_clusters(bs
, s
->cluster_size
);
1897 if (l2_refcount
> 1) {
1898 /* For shared L2 tables, set the refcount accordingly
1899 * (it is already 1 and needs to be l2_refcount) */
1900 ret
= qcow2_update_cluster_refcount(
1901 bs
, offset
>> s
->cluster_bits
,
1902 refcount_diff(1, l2_refcount
), false,
1903 QCOW2_DISCARD_OTHER
);
1905 qcow2_free_clusters(bs
, offset
, s
->cluster_size
,
1906 QCOW2_DISCARD_OTHER
);
1912 if (offset_into_cluster(s
, offset
)) {
1913 int l2_index
= slice
* s
->l2_slice_size
+ j
;
1914 qcow2_signal_corruption(
1916 "Cluster allocation offset "
1917 "%#" PRIx64
" unaligned (L2 offset: %#"
1918 PRIx64
", L2 index: %#x)", offset
,
1919 l2_offset
, l2_index
);
1920 if (cluster_type
== QCOW2_CLUSTER_ZERO_PLAIN
) {
1921 qcow2_free_clusters(bs
, offset
, s
->cluster_size
,
1922 QCOW2_DISCARD_ALWAYS
);
1928 ret
= qcow2_pre_write_overlap_check(bs
, 0, offset
,
1931 if (cluster_type
== QCOW2_CLUSTER_ZERO_PLAIN
) {
1932 qcow2_free_clusters(bs
, offset
, s
->cluster_size
,
1933 QCOW2_DISCARD_ALWAYS
);
1938 ret
= bdrv_pwrite_zeroes(bs
->file
, offset
, s
->cluster_size
, 0);
1940 if (cluster_type
== QCOW2_CLUSTER_ZERO_PLAIN
) {
1941 qcow2_free_clusters(bs
, offset
, s
->cluster_size
,
1942 QCOW2_DISCARD_ALWAYS
);
1947 if (l2_refcount
== 1) {
1948 l2_slice
[j
] = cpu_to_be64(offset
| QCOW_OFLAG_COPIED
);
1950 l2_slice
[j
] = cpu_to_be64(offset
);
1957 qcow2_cache_entry_mark_dirty(s
->l2_table_cache
, l2_slice
);
1958 qcow2_cache_depends_on_flush(s
->l2_table_cache
);
1960 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
1963 ret
= qcow2_pre_write_overlap_check(
1964 bs
, QCOW2_OL_INACTIVE_L2
| QCOW2_OL_ACTIVE_L2
,
1965 slice_offset
, slice_size2
);
1970 ret
= bdrv_pwrite(bs
->file
, slice_offset
,
1971 l2_slice
, slice_size2
);
1979 (*visited_l1_entries
)++;
1981 status_cb(bs
, *visited_l1_entries
, l1_entries
, cb_opaque
);
1989 if (!is_active_l1
) {
1990 qemu_vfree(l2_slice
);
1992 qcow2_cache_put(s
->l2_table_cache
, (void **) &l2_slice
);
1999 * For backed images, expands all zero clusters on the image. For non-backed
2000 * images, deallocates all non-pre-allocated zero clusters (and claims the
2001 * allocation for pre-allocated ones). This is important for downgrading to a
2002 * qcow2 version which doesn't yet support metadata zero clusters.
2004 int qcow2_expand_zero_clusters(BlockDriverState
*bs
,
2005 BlockDriverAmendStatusCB
*status_cb
,
2008 BDRVQcow2State
*s
= bs
->opaque
;
2009 uint64_t *l1_table
= NULL
;
2010 int64_t l1_entries
= 0, visited_l1_entries
= 0;
2015 l1_entries
= s
->l1_size
;
2016 for (i
= 0; i
< s
->nb_snapshots
; i
++) {
2017 l1_entries
+= s
->snapshots
[i
].l1_size
;
2021 ret
= expand_zero_clusters_in_l1(bs
, s
->l1_table
, s
->l1_size
,
2022 &visited_l1_entries
, l1_entries
,
2023 status_cb
, cb_opaque
);
2028 /* Inactive L1 tables may point to active L2 tables - therefore it is
2029 * necessary to flush the L2 table cache before trying to access the L2
2030 * tables pointed to by inactive L1 entries (else we might try to expand
2031 * zero clusters that have already been expanded); furthermore, it is also
2032 * necessary to empty the L2 table cache, since it may contain tables which
2033 * are now going to be modified directly on disk, bypassing the cache.
2034 * qcow2_cache_empty() does both for us. */
2035 ret
= qcow2_cache_empty(bs
, s
->l2_table_cache
);
2040 for (i
= 0; i
< s
->nb_snapshots
; i
++) {
2042 uint64_t *new_l1_table
;
2043 Error
*local_err
= NULL
;
2045 ret
= qcow2_validate_table(bs
, s
->snapshots
[i
].l1_table_offset
,
2046 s
->snapshots
[i
].l1_size
, sizeof(uint64_t),
2047 QCOW_MAX_L1_SIZE
, "Snapshot L1 table",
2050 error_report_err(local_err
);
2054 l1_size2
= s
->snapshots
[i
].l1_size
* sizeof(uint64_t);
2055 new_l1_table
= g_try_realloc(l1_table
, l1_size2
);
2057 if (!new_l1_table
) {
2062 l1_table
= new_l1_table
;
2064 ret
= bdrv_pread(bs
->file
, s
->snapshots
[i
].l1_table_offset
,
2065 l1_table
, l1_size2
);
2070 for (j
= 0; j
< s
->snapshots
[i
].l1_size
; j
++) {
2071 be64_to_cpus(&l1_table
[j
]);
2074 ret
= expand_zero_clusters_in_l1(bs
, l1_table
, s
->snapshots
[i
].l1_size
,
2075 &visited_l1_entries
, l1_entries
,
2076 status_cb
, cb_opaque
);