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qemu / qemu / e554861766d9ae84dd5720baa4869f4ed711506f / . / block / qcow2.c
blob: ad46c03c2f6daef22f5232d1df9c119c8bfc180d [file] [log] [blame]
/*
* Block driver for the QCOW version 2 format
*
* Copyright (c) 2004-2006 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "block_int.h"
#include "module.h"
#include <zlib.h>
#include "aes.h"
#include "block/qcow2.h"
#include "qemu-error.h"
#include "qerror.h"
#include "trace.h"
/*
Differences with QCOW:
- Support for multiple incremental snapshots.
- Memory management by reference counts.
- Clusters which have a reference count of one have the bit
QCOW_OFLAG_COPIED to optimize write performance.
- Size of compressed clusters is stored in sectors to reduce bit usage
in the cluster offsets.
- Support for storing additional data (such as the VM state) in the
snapshots.
- If a backing store is used, the cluster size is not constrained
(could be backported to QCOW).
- L2 tables have always a size of one cluster.
*/
typedef struct {
uint32_t magic;
uint32_t len;
} QCowExtension;
#define QCOW2_EXT_MAGIC_END 0
#define QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
#define QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857
static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename)
{
const QCowHeader *cow_header = (const void *)buf;
if (buf_size >= sizeof(QCowHeader) &&
be32_to_cpu(cow_header->magic) == QCOW_MAGIC &&
be32_to_cpu(cow_header->version) >= 2)
return 100;
else
return 0;
}
/*
* read qcow2 extension and fill bs
* start reading from start_offset
* finish reading upon magic of value 0 or when end_offset reached
* unknown magic is skipped (future extension this version knows nothing about)
* return 0 upon success, non-0 otherwise
*/
static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
uint64_t end_offset, void **p_feature_table)
{
BDRVQcowState *s = bs->opaque;
QCowExtension ext;
uint64_t offset;
int ret;
#ifdef DEBUG_EXT
printf("qcow2_read_extensions: start=%ld end=%ld\n", start_offset, end_offset);
#endif
offset = start_offset;
while (offset < end_offset) {
#ifdef DEBUG_EXT
/* Sanity check */
if (offset > s->cluster_size)
printf("qcow2_read_extension: suspicious offset %lu\n", offset);
printf("attempting to read extended header in offset %lu\n", offset);
#endif
if (bdrv_pread(bs->file, offset, &ext, sizeof(ext)) != sizeof(ext)) {
fprintf(stderr, "qcow2_read_extension: ERROR: "
"pread fail from offset %" PRIu64 "\n",
offset);
return 1;
}
be32_to_cpus(&ext.magic);
be32_to_cpus(&ext.len);
offset += sizeof(ext);
#ifdef DEBUG_EXT
printf("ext.magic = 0x%x\n", ext.magic);
#endif
if (ext.len > end_offset - offset) {
error_report("Header extension too large");
return -EINVAL;
}
switch (ext.magic) {
case QCOW2_EXT_MAGIC_END:
return 0;
case QCOW2_EXT_MAGIC_BACKING_FORMAT:
if (ext.len >= sizeof(bs->backing_format)) {
fprintf(stderr, "ERROR: ext_backing_format: len=%u too large"
" (>=%zu)\n",
ext.len, sizeof(bs->backing_format));
return 2;
}
if (bdrv_pread(bs->file, offset , bs->backing_format,
ext.len) != ext.len)
return 3;
bs->backing_format[ext.len] = '\0';
#ifdef DEBUG_EXT
printf("Qcow2: Got format extension %s\n", bs->backing_format);
#endif
break;
case QCOW2_EXT_MAGIC_FEATURE_TABLE:
if (p_feature_table != NULL) {
void* feature_table = g_malloc0(ext.len + 2 * sizeof(Qcow2Feature));
ret = bdrv_pread(bs->file, offset , feature_table, ext.len);
if (ret < 0) {
return ret;
}
*p_feature_table = feature_table;
}
break;
default:
/* unknown magic - save it in case we need to rewrite the header */
{
Qcow2UnknownHeaderExtension *uext;
uext = g_malloc0(sizeof(*uext) + ext.len);
uext->magic = ext.magic;
uext->len = ext.len;
QLIST_INSERT_HEAD(&s->unknown_header_ext, uext, next);
ret = bdrv_pread(bs->file, offset , uext->data, uext->len);
if (ret < 0) {
return ret;
}
}
break;
}
offset += ((ext.len + 7) & ~7);
}
return 0;
}
static void cleanup_unknown_header_ext(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
Qcow2UnknownHeaderExtension *uext, *next;
QLIST_FOREACH_SAFE(uext, &s->unknown_header_ext, next, next) {
QLIST_REMOVE(uext, next);
g_free(uext);
}
}
static void report_unsupported(BlockDriverState *bs, const char *fmt, ...)
{
char msg[64];
va_list ap;
va_start(ap, fmt);
vsnprintf(msg, sizeof(msg), fmt, ap);
va_end(ap);
qerror_report(QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
bs->device_name, "qcow2", msg);
}
static void report_unsupported_feature(BlockDriverState *bs,
Qcow2Feature *table, uint64_t mask)
{
while (table && table->name[0] != '\0') {
if (table->type == QCOW2_FEAT_TYPE_INCOMPATIBLE) {
if (mask & (1 << table->bit)) {
report_unsupported(bs, "%.46s",table->name);
mask &= ~(1 << table->bit);
}
}
table++;
}
if (mask) {
report_unsupported(bs, "Unknown incompatible feature: %" PRIx64, mask);
}
}
static int qcow2_open(BlockDriverState *bs, int flags)
{
BDRVQcowState *s = bs->opaque;
int len, i, ret = 0;
QCowHeader header;
uint64_t ext_end;
bool writethrough;
ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
if (ret < 0) {
goto fail;
}
be32_to_cpus(&header.magic);
be32_to_cpus(&header.version);
be64_to_cpus(&header.backing_file_offset);
be32_to_cpus(&header.backing_file_size);
be64_to_cpus(&header.size);
be32_to_cpus(&header.cluster_bits);
be32_to_cpus(&header.crypt_method);
be64_to_cpus(&header.l1_table_offset);
be32_to_cpus(&header.l1_size);
be64_to_cpus(&header.refcount_table_offset);
be32_to_cpus(&header.refcount_table_clusters);
be64_to_cpus(&header.snapshots_offset);
be32_to_cpus(&header.nb_snapshots);
if (header.magic != QCOW_MAGIC) {
ret = -EINVAL;
goto fail;
}
if (header.version < 2 || header.version > 3) {
report_unsupported(bs, "QCOW version %d", header.version);
ret = -ENOTSUP;
goto fail;
}
s->qcow_version = header.version;
/* Initialise version 3 header fields */
if (header.version == 2) {
header.incompatible_features = 0;
header.compatible_features = 0;
header.autoclear_features = 0;
header.refcount_order = 4;
header.header_length = 72;
} else {
be64_to_cpus(&header.incompatible_features);
be64_to_cpus(&header.compatible_features);
be64_to_cpus(&header.autoclear_features);
be32_to_cpus(&header.refcount_order);
be32_to_cpus(&header.header_length);
}
if (header.header_length > sizeof(header)) {
s->unknown_header_fields_size = header.header_length - sizeof(header);
s->unknown_header_fields = g_malloc(s->unknown_header_fields_size);
ret = bdrv_pread(bs->file, sizeof(header), s->unknown_header_fields,
s->unknown_header_fields_size);
if (ret < 0) {
goto fail;
}
}
if (header.backing_file_offset) {
ext_end = header.backing_file_offset;
} else {
ext_end = 1 << header.cluster_bits;
}
/* Handle feature bits */
s->incompatible_features = header.incompatible_features;
s->compatible_features = header.compatible_features;
s->autoclear_features = header.autoclear_features;
if (s->incompatible_features != 0) {
void *feature_table = NULL;
qcow2_read_extensions(bs, header.header_length, ext_end,
&feature_table);
report_unsupported_feature(bs, feature_table,
s->incompatible_features);
ret = -ENOTSUP;
goto fail;
}
if (!bs->read_only && s->autoclear_features != 0) {
s->autoclear_features = 0;
qcow2_update_header(bs);
}
/* Check support for various header values */
if (header.refcount_order != 4) {
report_unsupported(bs, "%d bit reference counts",
1 << header.refcount_order);
ret = -ENOTSUP;
goto fail;
}
if (header.cluster_bits < MIN_CLUSTER_BITS ||
header.cluster_bits > MAX_CLUSTER_BITS) {
ret = -EINVAL;
goto fail;
}
if (header.crypt_method > QCOW_CRYPT_AES) {
ret = -EINVAL;
goto fail;
}
s->crypt_method_header = header.crypt_method;
if (s->crypt_method_header) {
bs->encrypted = 1;
}
s->cluster_bits = header.cluster_bits;
s->cluster_size = 1 << s->cluster_bits;
s->cluster_sectors = 1 << (s->cluster_bits - 9);
s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */
s->l2_size = 1 << s->l2_bits;
bs->total_sectors = header.size / 512;
s->csize_shift = (62 - (s->cluster_bits - 8));
s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;
s->cluster_offset_mask = (1LL << s->csize_shift) - 1;
s->refcount_table_offset = header.refcount_table_offset;
s->refcount_table_size =
header.refcount_table_clusters << (s->cluster_bits - 3);
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
/* read the level 1 table */
s->l1_size = header.l1_size;
s->l1_vm_state_index = size_to_l1(s, header.size);
/* the L1 table must contain at least enough entries to put
header.size bytes */
if (s->l1_size < s->l1_vm_state_index) {
ret = -EINVAL;
goto fail;
}
s->l1_table_offset = header.l1_table_offset;
if (s->l1_size > 0) {
s->l1_table = g_malloc0(
align_offset(s->l1_size * sizeof(uint64_t), 512));
ret = bdrv_pread(bs->file, s->l1_table_offset, s->l1_table,
s->l1_size * sizeof(uint64_t));
if (ret < 0) {
goto fail;
}
for(i = 0;i < s->l1_size; i++) {
be64_to_cpus(&s->l1_table[i]);
}
}
/* alloc L2 table/refcount block cache */
writethrough = ((flags & BDRV_O_CACHE_WB) == 0);
s->l2_table_cache = qcow2_cache_create(bs, L2_CACHE_SIZE, writethrough);
s->refcount_block_cache = qcow2_cache_create(bs, REFCOUNT_CACHE_SIZE,
writethrough);
s->cluster_cache = g_malloc(s->cluster_size);
/* one more sector for decompressed data alignment */
s->cluster_data = qemu_blockalign(bs, QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size
+ 512);
s->cluster_cache_offset = -1;
s->flags = flags;
ret = qcow2_refcount_init(bs);
if (ret != 0) {
goto fail;
}
QLIST_INIT(&s->cluster_allocs);
/* read qcow2 extensions */
if (qcow2_read_extensions(bs, header.header_length, ext_end, NULL)) {
ret = -EINVAL;
goto fail;
}
/* read the backing file name */
if (header.backing_file_offset != 0) {
len = header.backing_file_size;
if (len > 1023) {
len = 1023;
}
ret = bdrv_pread(bs->file, header.backing_file_offset,
bs->backing_file, len);
if (ret < 0) {
goto fail;
}
bs->backing_file[len] = '\0';
}
ret = qcow2_read_snapshots(bs);
if (ret < 0) {
goto fail;
}
/* Initialise locks */
qemu_co_mutex_init(&s->lock);
#ifdef DEBUG_ALLOC
{
BdrvCheckResult result = {0};
qcow2_check_refcounts(bs, &result);
}
#endif
return ret;
fail:
g_free(s->unknown_header_fields);
cleanup_unknown_header_ext(bs);
qcow2_free_snapshots(bs);
qcow2_refcount_close(bs);
g_free(s->l1_table);
if (s->l2_table_cache) {
qcow2_cache_destroy(bs, s->l2_table_cache);
}
g_free(s->cluster_cache);
qemu_vfree(s->cluster_data);
return ret;
}
static int qcow2_set_key(BlockDriverState *bs, const char *key)
{
BDRVQcowState *s = bs->opaque;
uint8_t keybuf[16];
int len, i;
memset(keybuf, 0, 16);
len = strlen(key);
if (len > 16)
len = 16;
/* XXX: we could compress the chars to 7 bits to increase
entropy */
for(i = 0;i < len;i++) {
keybuf[i] = key[i];
}
s->crypt_method = s->crypt_method_header;
if (AES_set_encrypt_key(keybuf, 128, &s->aes_encrypt_key) != 0)
return -1;
if (AES_set_decrypt_key(keybuf, 128, &s->aes_decrypt_key) != 0)
return -1;
#if 0
/* test */
{
uint8_t in[16];
uint8_t out[16];
uint8_t tmp[16];
for(i=0;i<16;i++)
in[i] = i;
AES_encrypt(in, tmp, &s->aes_encrypt_key);
AES_decrypt(tmp, out, &s->aes_decrypt_key);
for(i = 0; i < 16; i++)
printf(" %02x", tmp[i]);
printf("\n");
for(i = 0; i < 16; i++)
printf(" %02x", out[i]);
printf("\n");
}
#endif
return 0;
}
static int coroutine_fn qcow2_co_is_allocated(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, int *pnum)
{
BDRVQcowState *s = bs->opaque;
uint64_t cluster_offset;
int ret;
*pnum = nb_sectors;
/* FIXME We can get errors here, but the bdrv_co_is_allocated interface
* can't pass them on today */
qemu_co_mutex_lock(&s->lock);
ret = qcow2_get_cluster_offset(bs, sector_num << 9, pnum, &cluster_offset);
qemu_co_mutex_unlock(&s->lock);
if (ret < 0) {
*pnum = 0;
}
return (cluster_offset != 0);
}
/* handle reading after the end of the backing file */
int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t sector_num, int nb_sectors)
{
int n1;
if ((sector_num + nb_sectors) <= bs->total_sectors)
return nb_sectors;
if (sector_num >= bs->total_sectors)
n1 = 0;
else
n1 = bs->total_sectors - sector_num;
qemu_iovec_memset_skip(qiov, 0, 512 * (nb_sectors - n1), 512 * n1);
return n1;
}
static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
int remaining_sectors, QEMUIOVector *qiov)
{
BDRVQcowState *s = bs->opaque;
int index_in_cluster, n1;
int ret;
int cur_nr_sectors; /* number of sectors in current iteration */
uint64_t cluster_offset = 0;
uint64_t bytes_done = 0;
QEMUIOVector hd_qiov;
uint8_t *cluster_data = NULL;
qemu_iovec_init(&hd_qiov, qiov->niov);
qemu_co_mutex_lock(&s->lock);
while (remaining_sectors != 0) {
/* prepare next request */
cur_nr_sectors = remaining_sectors;
if (s->crypt_method) {
cur_nr_sectors = MIN(cur_nr_sectors,
QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);
}
ret = qcow2_get_cluster_offset(bs, sector_num << 9,
&cur_nr_sectors, &cluster_offset);
if (ret < 0) {
goto fail;
}
index_in_cluster = sector_num & (s->cluster_sectors - 1);
qemu_iovec_reset(&hd_qiov);
qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
cur_nr_sectors * 512);
switch (ret) {
case QCOW2_CLUSTER_UNALLOCATED:
if (bs->backing_hd) {
/* read from the base image */
n1 = qcow2_backing_read1(bs->backing_hd, &hd_qiov,
sector_num, cur_nr_sectors);
if (n1 > 0) {
BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);
qemu_co_mutex_unlock(&s->lock);
ret = bdrv_co_readv(bs->backing_hd, sector_num,
n1, &hd_qiov);
qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
goto fail;
}
}
} else {
/* Note: in this case, no need to wait */
qemu_iovec_memset(&hd_qiov, 0, 512 * cur_nr_sectors);
}
break;
case QCOW2_CLUSTER_ZERO:
if (s->qcow_version < 3) {
ret = -EIO;
goto fail;
}
qemu_iovec_memset(&hd_qiov, 0, 512 * cur_nr_sectors);
break;
case QCOW2_CLUSTER_COMPRESSED:
/* add AIO support for compressed blocks ? */
ret = qcow2_decompress_cluster(bs, cluster_offset);
if (ret < 0) {
goto fail;
}
qemu_iovec_from_buffer(&hd_qiov,
s->cluster_cache + index_in_cluster * 512,
512 * cur_nr_sectors);
break;
case QCOW2_CLUSTER_NORMAL:
if ((cluster_offset & 511) != 0) {
ret = -EIO;
goto fail;
}
if (s->crypt_method) {
/*
* For encrypted images, read everything into a temporary
* contiguous buffer on which the AES functions can work.
*/
if (!cluster_data) {
cluster_data =
qemu_blockalign(bs, QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
}
assert(cur_nr_sectors <=
QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);
qemu_iovec_reset(&hd_qiov);
qemu_iovec_add(&hd_qiov, cluster_data,
512 * cur_nr_sectors);
}
BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
qemu_co_mutex_unlock(&s->lock);
ret = bdrv_co_readv(bs->file,
(cluster_offset >> 9) + index_in_cluster,
cur_nr_sectors, &hd_qiov);
qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
goto fail;
}
if (s->crypt_method) {
qcow2_encrypt_sectors(s, sector_num, cluster_data,
cluster_data, cur_nr_sectors, 0, &s->aes_decrypt_key);
qemu_iovec_reset(&hd_qiov);
qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
cur_nr_sectors * 512);
qemu_iovec_from_buffer(&hd_qiov, cluster_data,
512 * cur_nr_sectors);
}
break;
default:
g_assert_not_reached();
ret = -EIO;
goto fail;
}
remaining_sectors -= cur_nr_sectors;
sector_num += cur_nr_sectors;
bytes_done += cur_nr_sectors * 512;
}
ret = 0;
fail:
qemu_co_mutex_unlock(&s->lock);
qemu_iovec_destroy(&hd_qiov);
qemu_vfree(cluster_data);
return ret;
}
static void run_dependent_requests(BDRVQcowState *s, QCowL2Meta *m)
{
/* Take the request off the list of running requests */
if (m->nb_clusters != 0) {
QLIST_REMOVE(m, next_in_flight);
}
/* Restart all dependent requests */
if (!qemu_co_queue_empty(&m->dependent_requests)) {
qemu_co_mutex_unlock(&s->lock);
qemu_co_queue_restart_all(&m->dependent_requests);
qemu_co_mutex_lock(&s->lock);
}
}
static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
int64_t sector_num,
int remaining_sectors,
QEMUIOVector *qiov)
{
BDRVQcowState *s = bs->opaque;
int index_in_cluster;
int n_end;
int ret;
int cur_nr_sectors; /* number of sectors in current iteration */
uint64_t cluster_offset;
QEMUIOVector hd_qiov;
uint64_t bytes_done = 0;
uint8_t *cluster_data = NULL;
QCowL2Meta l2meta = {
.nb_clusters = 0,
};
trace_qcow2_writev_start_req(qemu_coroutine_self(), sector_num,
remaining_sectors);
qemu_co_queue_init(&l2meta.dependent_requests);
qemu_iovec_init(&hd_qiov, qiov->niov);
s->cluster_cache_offset = -1; /* disable compressed cache */
qemu_co_mutex_lock(&s->lock);
while (remaining_sectors != 0) {
trace_qcow2_writev_start_part(qemu_coroutine_self());
index_in_cluster = sector_num & (s->cluster_sectors - 1);
n_end = index_in_cluster + remaining_sectors;
if (s->crypt_method &&
n_end > QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors) {
n_end = QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors;
}
ret = qcow2_alloc_cluster_offset(bs, sector_num << 9,
index_in_cluster, n_end, &cur_nr_sectors, &l2meta);
if (ret < 0) {
goto fail;
}
cluster_offset = l2meta.cluster_offset;
assert((cluster_offset & 511) == 0);
qemu_iovec_reset(&hd_qiov);
qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
cur_nr_sectors * 512);
if (s->crypt_method) {
if (!cluster_data) {
cluster_data = qemu_blockalign(bs, QCOW_MAX_CRYPT_CLUSTERS *
s->cluster_size);
}
assert(hd_qiov.size <=
QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
qemu_iovec_to_buffer(&hd_qiov, cluster_data);
qcow2_encrypt_sectors(s, sector_num, cluster_data,
cluster_data, cur_nr_sectors, 1, &s->aes_encrypt_key);
qemu_iovec_reset(&hd_qiov);
qemu_iovec_add(&hd_qiov, cluster_data,
cur_nr_sectors * 512);
}
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
qemu_co_mutex_unlock(&s->lock);
trace_qcow2_writev_data(qemu_coroutine_self(),
(cluster_offset >> 9) + index_in_cluster);
ret = bdrv_co_writev(bs->file,
(cluster_offset >> 9) + index_in_cluster,
cur_nr_sectors, &hd_qiov);
qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
goto fail;
}
ret = qcow2_alloc_cluster_link_l2(bs, &l2meta);
if (ret < 0) {
goto fail;
}
run_dependent_requests(s, &l2meta);
remaining_sectors -= cur_nr_sectors;
sector_num += cur_nr_sectors;
bytes_done += cur_nr_sectors * 512;
trace_qcow2_writev_done_part(qemu_coroutine_self(), cur_nr_sectors);
}
ret = 0;
fail:
run_dependent_requests(s, &l2meta);
qemu_co_mutex_unlock(&s->lock);
qemu_iovec_destroy(&hd_qiov);
qemu_vfree(cluster_data);
trace_qcow2_writev_done_req(qemu_coroutine_self(), ret);
return ret;
}
static void qcow2_close(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
g_free(s->l1_table);
qcow2_cache_flush(bs, s->l2_table_cache);
qcow2_cache_flush(bs, s->refcount_block_cache);
qcow2_cache_destroy(bs, s->l2_table_cache);
qcow2_cache_destroy(bs, s->refcount_block_cache);
g_free(s->unknown_header_fields);
cleanup_unknown_header_ext(bs);
g_free(s->cluster_cache);
qemu_vfree(s->cluster_data);
qcow2_refcount_close(bs);
qcow2_free_snapshots(bs);
}
static void qcow2_invalidate_cache(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int flags = s->flags;
AES_KEY aes_encrypt_key;
AES_KEY aes_decrypt_key;
uint32_t crypt_method = 0;
/*
* Backing files are read-only which makes all of their metadata immutable,
* that means we don't have to worry about reopening them here.
*/
if (s->crypt_method) {
crypt_method = s->crypt_method;
memcpy(&aes_encrypt_key, &s->aes_encrypt_key, sizeof(aes_encrypt_key));
memcpy(&aes_decrypt_key, &s->aes_decrypt_key, sizeof(aes_decrypt_key));
}
qcow2_close(bs);
memset(s, 0, sizeof(BDRVQcowState));
qcow2_open(bs, flags);
if (crypt_method) {
s->crypt_method = crypt_method;
memcpy(&s->aes_encrypt_key, &aes_encrypt_key, sizeof(aes_encrypt_key));
memcpy(&s->aes_decrypt_key, &aes_decrypt_key, sizeof(aes_decrypt_key));
}
}
static size_t header_ext_add(char *buf, uint32_t magic, const void *s,
size_t len, size_t buflen)
{
QCowExtension *ext_backing_fmt = (QCowExtension*) buf;
size_t ext_len = sizeof(QCowExtension) + ((len + 7) & ~7);
if (buflen < ext_len) {
return -ENOSPC;
}
*ext_backing_fmt = (QCowExtension) {
.magic = cpu_to_be32(magic),
.len = cpu_to_be32(len),
};
memcpy(buf + sizeof(QCowExtension), s, len);
return ext_len;
}
/*
* Updates the qcow2 header, including the variable length parts of it, i.e.
* the backing file name and all extensions. qcow2 was not designed to allow
* such changes, so if we run out of space (we can only use the first cluster)
* this function may fail.
*
* Returns 0 on success, -errno in error cases.
*/
int qcow2_update_header(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
QCowHeader *header;
char *buf;
size_t buflen = s->cluster_size;
int ret;
uint64_t total_size;
uint32_t refcount_table_clusters;
size_t header_length;
Qcow2UnknownHeaderExtension *uext;
buf = qemu_blockalign(bs, buflen);
/* Header structure */
header = (QCowHeader*) buf;
if (buflen < sizeof(*header)) {
ret = -ENOSPC;
goto fail;
}
header_length = sizeof(*header) + s->unknown_header_fields_size;
total_size = bs->total_sectors * BDRV_SECTOR_SIZE;
refcount_table_clusters = s->refcount_table_size >> (s->cluster_bits - 3);
*header = (QCowHeader) {
/* Version 2 fields */
.magic = cpu_to_be32(QCOW_MAGIC),
.version = cpu_to_be32(s->qcow_version),
.backing_file_offset = 0,
.backing_file_size = 0,
.cluster_bits = cpu_to_be32(s->cluster_bits),
.size = cpu_to_be64(total_size),
.crypt_method = cpu_to_be32(s->crypt_method_header),
.l1_size = cpu_to_be32(s->l1_size),
.l1_table_offset = cpu_to_be64(s->l1_table_offset),
.refcount_table_offset = cpu_to_be64(s->refcount_table_offset),
.refcount_table_clusters = cpu_to_be32(refcount_table_clusters),
.nb_snapshots = cpu_to_be32(s->nb_snapshots),
.snapshots_offset = cpu_to_be64(s->snapshots_offset),
/* Version 3 fields */
.incompatible_features = cpu_to_be64(s->incompatible_features),
.compatible_features = cpu_to_be64(s->compatible_features),
.autoclear_features = cpu_to_be64(s->autoclear_features),
.refcount_order = cpu_to_be32(3 + REFCOUNT_SHIFT),
.header_length = cpu_to_be32(header_length),
};
/* For older versions, write a shorter header */
switch (s->qcow_version) {
case 2:
ret = offsetof(QCowHeader, incompatible_features);
break;
case 3:
ret = sizeof(*header);
break;
default:
return -EINVAL;
}
buf += ret;
buflen -= ret;
memset(buf, 0, buflen);
/* Preserve any unknown field in the header */
if (s->unknown_header_fields_size) {
if (buflen < s->unknown_header_fields_size) {
ret = -ENOSPC;
goto fail;
}
memcpy(buf, s->unknown_header_fields, s->unknown_header_fields_size);
buf += s->unknown_header_fields_size;
buflen -= s->unknown_header_fields_size;
}
/* Backing file format header extension */
if (*bs->backing_format) {
ret = header_ext_add(buf, QCOW2_EXT_MAGIC_BACKING_FORMAT,
bs->backing_format, strlen(bs->backing_format),
buflen);
if (ret < 0) {
goto fail;
}
buf += ret;
buflen -= ret;
}
/* Feature table */
Qcow2Feature features[] = {
/* no feature defined yet */
};
ret = header_ext_add(buf, QCOW2_EXT_MAGIC_FEATURE_TABLE,
features, sizeof(features), buflen);
if (ret < 0) {
goto fail;
}
buf += ret;
buflen -= ret;
/* Keep unknown header extensions */
QLIST_FOREACH(uext, &s->unknown_header_ext, next) {
ret = header_ext_add(buf, uext->magic, uext->data, uext->len, buflen);
if (ret < 0) {
goto fail;
}
buf += ret;
buflen -= ret;
}
/* End of header extensions */
ret = header_ext_add(buf, QCOW2_EXT_MAGIC_END, NULL, 0, buflen);
if (ret < 0) {
goto fail;
}
buf += ret;
buflen -= ret;
/* Backing file name */
if (*bs->backing_file) {
size_t backing_file_len = strlen(bs->backing_file);
if (buflen < backing_file_len) {
ret = -ENOSPC;
goto fail;
}
strncpy(buf, bs->backing_file, buflen);
header->backing_file_offset = cpu_to_be64(buf - ((char*) header));
header->backing_file_size = cpu_to_be32(backing_file_len);
}
/* Write the new header */
ret = bdrv_pwrite(bs->file, 0, header, s->cluster_size);
if (ret < 0) {
goto fail;
}
ret = 0;
fail:
qemu_vfree(header);
return ret;
}
static int qcow2_change_backing_file(BlockDriverState *bs,
const char *backing_file, const char *backing_fmt)
{
/* Backing file format doesn't make sense without a backing file */
if (backing_fmt && !backing_file) {
return -EINVAL;
}
pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: "");
pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: "");
return qcow2_update_header(bs);
}
static int preallocate(BlockDriverState *bs)
{
uint64_t nb_sectors;
uint64_t offset;
int num;
int ret;
QCowL2Meta meta;
nb_sectors = bdrv_getlength(bs) >> 9;
offset = 0;
qemu_co_queue_init(&meta.dependent_requests);
meta.cluster_offset = 0;
while (nb_sectors) {
num = MIN(nb_sectors, INT_MAX >> 9);
ret = qcow2_alloc_cluster_offset(bs, offset, 0, num, &num, &meta);
if (ret < 0) {
return ret;
}
ret = qcow2_alloc_cluster_link_l2(bs, &meta);
if (ret < 0) {
qcow2_free_any_clusters(bs, meta.cluster_offset, meta.nb_clusters);
return ret;
}
/* There are no dependent requests, but we need to remove our request
* from the list of in-flight requests */
run_dependent_requests(bs->opaque, &meta);
/* TODO Preallocate data if requested */
nb_sectors -= num;
offset += num << 9;
}
/*
* It is expected that the image file is large enough to actually contain
* all of the allocated clusters (otherwise we get failing reads after
* EOF). Extend the image to the last allocated sector.
*/
if (meta.cluster_offset != 0) {
uint8_t buf[512];
memset(buf, 0, 512);
ret = bdrv_write(bs->file, (meta.cluster_offset >> 9) + num - 1, buf, 1);
if (ret < 0) {
return ret;
}
}
return 0;
}
static int qcow2_create2(const char *filename, int64_t total_size,
const char *backing_file, const char *backing_format,
int flags, size_t cluster_size, int prealloc,
QEMUOptionParameter *options, int version)
{
/* Calculate cluster_bits */
int cluster_bits;
cluster_bits = ffs(cluster_size) - 1;
if (cluster_bits < MIN_CLUSTER_BITS || cluster_bits > MAX_CLUSTER_BITS ||
(1 << cluster_bits) != cluster_size)
{
error_report(
"Cluster size must be a power of two between %d and %dk",
1 << MIN_CLUSTER_BITS, 1 << (MAX_CLUSTER_BITS - 10));
return -EINVAL;
}
/*
* Open the image file and write a minimal qcow2 header.
*
* We keep things simple and start with a zero-sized image. We also
* do without refcount blocks or a L1 table for now. We'll fix the
* inconsistency later.
*
* We do need a refcount table because growing the refcount table means
* allocating two new refcount blocks - the seconds of which would be at
* 2 GB for 64k clusters, and we don't want to have a 2 GB initial file
* size for any qcow2 image.
*/
BlockDriverState* bs;
QCowHeader header;
uint8_t* refcount_table;
int ret;
ret = bdrv_create_file(filename, options);
if (ret < 0) {
return ret;
}
ret = bdrv_file_open(&bs, filename, BDRV_O_RDWR);
if (ret < 0) {
return ret;
}
/* Write the header */
memset(&header, 0, sizeof(header));
header.magic = cpu_to_be32(QCOW_MAGIC);
header.version = cpu_to_be32(version);
header.cluster_bits = cpu_to_be32(cluster_bits);
header.size = cpu_to_be64(0);
header.l1_table_offset = cpu_to_be64(0);
header.l1_size = cpu_to_be32(0);
header.refcount_table_offset = cpu_to_be64(cluster_size);
header.refcount_table_clusters = cpu_to_be32(1);
header.refcount_order = cpu_to_be32(3 + REFCOUNT_SHIFT);
header.header_length = cpu_to_be32(sizeof(header));
if (flags & BLOCK_FLAG_ENCRYPT) {
header.crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
} else {
header.crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);
}
ret = bdrv_pwrite(bs, 0, &header, sizeof(header));
if (ret < 0) {
goto out;
}
/* Write an empty refcount table */
refcount_table = g_malloc0(cluster_size);
ret = bdrv_pwrite(bs, cluster_size, refcount_table, cluster_size);
g_free(refcount_table);
if (ret < 0) {
goto out;
}
bdrv_close(bs);
/*
* And now open the image and make it consistent first (i.e. increase the
* refcount of the cluster that is occupied by the header and the refcount
* table)
*/
BlockDriver* drv = bdrv_find_format("qcow2");
assert(drv != NULL);
ret = bdrv_open(bs, filename,
BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH, drv);
if (ret < 0) {
goto out;
}
ret = qcow2_alloc_clusters(bs, 2 * cluster_size);
if (ret < 0) {
goto out;
} else if (ret != 0) {
error_report("Huh, first cluster in empty image is already in use?");
abort();
}
/* Okay, now that we have a valid image, let's give it the right size */
ret = bdrv_truncate(bs, total_size * BDRV_SECTOR_SIZE);
if (ret < 0) {
goto out;
}
/* Want a backing file? There you go.*/
if (backing_file) {
ret = bdrv_change_backing_file(bs, backing_file, backing_format);
if (ret < 0) {
goto out;
}
}
/* And if we're supposed to preallocate metadata, do that now */
if (prealloc) {
ret = preallocate(bs);
if (ret < 0) {
goto out;
}
}
ret = 0;
out:
bdrv_delete(bs);
return ret;
}
static int qcow2_create(const char *filename, QEMUOptionParameter *options)
{
const char *backing_file = NULL;
const char *backing_fmt = NULL;
uint64_t sectors = 0;
int flags = 0;
size_t cluster_size = DEFAULT_CLUSTER_SIZE;
int prealloc = 0;
int version = 2;
/* Read out options */
while (options && options->name) {
if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
sectors = options->value.n / 512;
} else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
backing_file = options->value.s;
} else if (!strcmp(options->name, BLOCK_OPT_BACKING_FMT)) {
backing_fmt = options->value.s;
} else if (!strcmp(options->name, BLOCK_OPT_ENCRYPT)) {
flags |= options->value.n ? BLOCK_FLAG_ENCRYPT : 0;
} else if (!strcmp(options->name, BLOCK_OPT_CLUSTER_SIZE)) {
if (options->value.n) {
cluster_size = options->value.n;
}
} else if (!strcmp(options->name, BLOCK_OPT_PREALLOC)) {
if (!options->value.s || !strcmp(options->value.s, "off")) {
prealloc = 0;
} else if (!strcmp(options->value.s, "metadata")) {
prealloc = 1;
} else {
fprintf(stderr, "Invalid preallocation mode: '%s'\n",
options->value.s);
return -EINVAL;
}
} else if (!strcmp(options->name, BLOCK_OPT_COMPAT_LEVEL)) {
if (!options->value.s || !strcmp(options->value.s, "0.10")) {
version = 2;
} else if (!strcmp(options->value.s, "1.1")) {
version = 3;
} else {
fprintf(stderr, "Invalid compatibility level: '%s'\n",
options->value.s);
return -EINVAL;
}
}
options++;
}
if (backing_file && prealloc) {
fprintf(stderr, "Backing file and preallocation cannot be used at "
"the same time\n");
return -EINVAL;
}
return qcow2_create2(filename, sectors, backing_file, backing_fmt, flags,
cluster_size, prealloc, options, version);
}
static int qcow2_make_empty(BlockDriverState *bs)
{
#if 0
/* XXX: not correct */
BDRVQcowState *s = bs->opaque;
uint32_t l1_length = s->l1_size * sizeof(uint64_t);
int ret;
memset(s->l1_table, 0, l1_length);
if (bdrv_pwrite(bs->file, s->l1_table_offset, s->l1_table, l1_length) < 0)
return -1;
ret = bdrv_truncate(bs->file, s->l1_table_offset + l1_length);
if (ret < 0)
return ret;
l2_cache_reset(bs);
#endif
return 0;
}
static coroutine_fn int qcow2_co_write_zeroes(BlockDriverState *bs,
int64_t sector_num, int nb_sectors)
{
int ret;
BDRVQcowState *s = bs->opaque;
/* Emulate misaligned zero writes */
if (sector_num % s->cluster_sectors || nb_sectors % s->cluster_sectors) {
return -ENOTSUP;
}
/* Whatever is left can use real zero clusters */
qemu_co_mutex_lock(&s->lock);
ret = qcow2_zero_clusters(bs, sector_num << BDRV_SECTOR_BITS,
nb_sectors);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
static coroutine_fn int qcow2_co_discard(BlockDriverState *bs,
int64_t sector_num, int nb_sectors)
{
int ret;
BDRVQcowState *s = bs->opaque;
qemu_co_mutex_lock(&s->lock);
ret = qcow2_discard_clusters(bs, sector_num << BDRV_SECTOR_BITS,
nb_sectors);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
static int qcow2_truncate(BlockDriverState *bs, int64_t offset)
{
BDRVQcowState *s = bs->opaque;
int ret, new_l1_size;
if (offset & 511) {
error_report("The new size must be a multiple of 512");
return -EINVAL;
}
/* cannot proceed if image has snapshots */
if (s->nb_snapshots) {
error_report("Can't resize an image which has snapshots");
return -ENOTSUP;
}
/* shrinking is currently not supported */
if (offset < bs->total_sectors * 512) {
error_report("qcow2 doesn't support shrinking images yet");
return -ENOTSUP;
}
new_l1_size = size_to_l1(s, offset);
ret = qcow2_grow_l1_table(bs, new_l1_size, true);
if (ret < 0) {
return ret;
}
/* write updated header.size */
offset = cpu_to_be64(offset);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, size),
&offset, sizeof(uint64_t));
if (ret < 0) {
return ret;
}
s->l1_vm_state_index = new_l1_size;
return 0;
}
/* XXX: put compressed sectors first, then all the cluster aligned
tables to avoid losing bytes in alignment */
static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
BDRVQcowState *s = bs->opaque;
z_stream strm;
int ret, out_len;
uint8_t *out_buf;
uint64_t cluster_offset;
if (nb_sectors == 0) {
/* align end of file to a sector boundary to ease reading with
sector based I/Os */
cluster_offset = bdrv_getlength(bs->file);
cluster_offset = (cluster_offset + 511) & ~511;
bdrv_truncate(bs->file, cluster_offset);
return 0;
}
if (nb_sectors != s->cluster_sectors)
return -EINVAL;
out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128);
/* best compression, small window, no zlib header */
memset(&strm, 0, sizeof(strm));
ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION,
Z_DEFLATED, -12,
9, Z_DEFAULT_STRATEGY);
if (ret != 0) {
ret = -EINVAL;
goto fail;
}
strm.avail_in = s->cluster_size;
strm.next_in = (uint8_t *)buf;
strm.avail_out = s->cluster_size;
strm.next_out = out_buf;
ret = deflate(&strm, Z_FINISH);
if (ret != Z_STREAM_END && ret != Z_OK) {
deflateEnd(&strm);
ret = -EINVAL;
goto fail;
}
out_len = strm.next_out - out_buf;
deflateEnd(&strm);
if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
/* could not compress: write normal cluster */
ret = bdrv_write(bs, sector_num, buf, s->cluster_sectors);
if (ret < 0) {
goto fail;
}
} else {
cluster_offset = qcow2_alloc_compressed_cluster_offset(bs,
sector_num << 9, out_len);
if (!cluster_offset) {
ret = -EIO;
goto fail;
}
cluster_offset &= s->cluster_offset_mask;
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_COMPRESSED);
ret = bdrv_pwrite(bs->file, cluster_offset, out_buf, out_len);
if (ret < 0) {
goto fail;
}
}
ret = 0;
fail:
g_free(out_buf);
return ret;
}
static coroutine_fn int qcow2_co_flush_to_os(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int ret;
qemu_co_mutex_lock(&s->lock);
ret = qcow2_cache_flush(bs, s->l2_table_cache);
if (ret < 0) {
qemu_co_mutex_unlock(&s->lock);
return ret;
}
ret = qcow2_cache_flush(bs, s->refcount_block_cache);
if (ret < 0) {
qemu_co_mutex_unlock(&s->lock);
return ret;
}
qemu_co_mutex_unlock(&s->lock);
return 0;
}
static int64_t qcow2_vm_state_offset(BDRVQcowState *s)
{
return (int64_t)s->l1_vm_state_index << (s->cluster_bits + s->l2_bits);
}
static int qcow2_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
BDRVQcowState *s = bs->opaque;
bdi->cluster_size = s->cluster_size;
bdi->vm_state_offset = qcow2_vm_state_offset(s);
return 0;
}
static int qcow2_check(BlockDriverState *bs, BdrvCheckResult *result)
{
return qcow2_check_refcounts(bs, result);
}
#if 0
static void dump_refcounts(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
int64_t nb_clusters, k, k1, size;
int refcount;
size = bdrv_getlength(bs->file);
nb_clusters = size_to_clusters(s, size);
for(k = 0; k < nb_clusters;) {
k1 = k;
refcount = get_refcount(bs, k);
k++;
while (k < nb_clusters && get_refcount(bs, k) == refcount)
k++;
printf("%" PRId64 ": refcount=%d nb=%" PRId64 "\n", k, refcount,
k - k1);
}
}
#endif
static int qcow2_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
int64_t pos, int size)
{
BDRVQcowState *s = bs->opaque;
int growable = bs->growable;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
bs->growable = 1;
ret = bdrv_pwrite(bs, qcow2_vm_state_offset(s) + pos, buf, size);
bs->growable = growable;
return ret;
}
static int qcow2_load_vmstate(BlockDriverState *bs, uint8_t *buf,
int64_t pos, int size)
{
BDRVQcowState *s = bs->opaque;
int growable = bs->growable;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
bs->growable = 1;
ret = bdrv_pread(bs, qcow2_vm_state_offset(s) + pos, buf, size);
bs->growable = growable;
return ret;
}
static QEMUOptionParameter qcow2_create_options[] = {
{
.name = BLOCK_OPT_SIZE,
.type = OPT_SIZE,
.help = "Virtual disk size"
},
{
.name = BLOCK_OPT_COMPAT_LEVEL,
.type = OPT_STRING,
.help = "Compatibility level (0.10 or 1.1)"
},
{
.name = BLOCK_OPT_BACKING_FILE,
.type = OPT_STRING,
.help = "File name of a base image"
},
{
.name = BLOCK_OPT_BACKING_FMT,
.type = OPT_STRING,
.help = "Image format of the base image"
},
{
.name = BLOCK_OPT_ENCRYPT,
.type = OPT_FLAG,
.help = "Encrypt the image"
},
{
.name = BLOCK_OPT_CLUSTER_SIZE,
.type = OPT_SIZE,
.help = "qcow2 cluster size",
.value = { .n = DEFAULT_CLUSTER_SIZE },
},
{
.name = BLOCK_OPT_PREALLOC,
.type = OPT_STRING,
.help = "Preallocation mode (allowed values: off, metadata)"
},
{ NULL }
};
static BlockDriver bdrv_qcow2 = {
.format_name = "qcow2",
.instance_size = sizeof(BDRVQcowState),
.bdrv_probe = qcow2_probe,
.bdrv_open = qcow2_open,
.bdrv_close = qcow2_close,
.bdrv_create = qcow2_create,
.bdrv_co_is_allocated = qcow2_co_is_allocated,
.bdrv_set_key = qcow2_set_key,
.bdrv_make_empty = qcow2_make_empty,
.bdrv_co_readv = qcow2_co_readv,
.bdrv_co_writev = qcow2_co_writev,
.bdrv_co_flush_to_os = qcow2_co_flush_to_os,
.bdrv_co_write_zeroes = qcow2_co_write_zeroes,
.bdrv_co_discard = qcow2_co_discard,
.bdrv_truncate = qcow2_truncate,
.bdrv_write_compressed = qcow2_write_compressed,
.bdrv_snapshot_create = qcow2_snapshot_create,
.bdrv_snapshot_goto = qcow2_snapshot_goto,
.bdrv_snapshot_delete = qcow2_snapshot_delete,
.bdrv_snapshot_list = qcow2_snapshot_list,
.bdrv_snapshot_load_tmp = qcow2_snapshot_load_tmp,
.bdrv_get_info = qcow2_get_info,
.bdrv_save_vmstate = qcow2_save_vmstate,
.bdrv_load_vmstate = qcow2_load_vmstate,
.bdrv_change_backing_file = qcow2_change_backing_file,
.bdrv_invalidate_cache = qcow2_invalidate_cache,
.create_options = qcow2_create_options,
.bdrv_check = qcow2_check,
};
static void bdrv_qcow2_init(void)
{
bdrv_register(&bdrv_qcow2);
}
block_init(bdrv_qcow2_init);