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qemu/block/qcow2.c
Kevin Wolf 205ef7961f block: Allow bdrv_flush to return errors 
This changes bdrv_flush to return 0 on success and -errno in case of failure.
It's a requirement for implementing proper error handle in users of bdrv_flush.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2010-11-04 12:52:16 +01:00

1307 lines
38 KiB
C
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/*
* 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"
/*
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 QCOW_EXT_MAGIC_END 0
#define QCOW_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
static int qcow_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) == QCOW_VERSION)
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 qcow_read_extensions(BlockDriverState *bs, uint64_t start_offset,
uint64_t end_offset)
{
QCowExtension ext;
uint64_t offset;
#ifdef DEBUG_EXT
printf("qcow_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("qcow_handle_extension: suspicious offset %lu\n", offset);
printf("attemting to read extended header in offset %lu\n", offset);
#endif
if (bdrv_pread(bs->file, offset, &ext, sizeof(ext)) != sizeof(ext)) {
fprintf(stderr, "qcow_handle_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
switch (ext.magic) {
case QCOW_EXT_MAGIC_END:
return 0;
case QCOW_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
offset = ((offset + ext.len + 7) & ~7);
break;
default:
/* unknown magic -- just skip it */
offset = ((offset + ext.len + 7) & ~7);
break;
}
}
return 0;
}
static int qcow_open(BlockDriverState *bs, int flags)
{
BDRVQcowState *s = bs->opaque;
int len, i;
QCowHeader header;
uint64_t ext_end;
if (bdrv_pread(bs->file, 0, &header, sizeof(header)) != sizeof(header))
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 || header.version != QCOW_VERSION)
goto fail;
if (header.cluster_bits < MIN_CLUSTER_BITS ||
header.cluster_bits > MAX_CLUSTER_BITS)
goto fail;
if (header.crypt_method > QCOW_CRYPT_AES)
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)
goto fail;
s->l1_table_offset = header.l1_table_offset;
if (s->l1_size > 0) {
s->l1_table = qemu_mallocz(
align_offset(s->l1_size * sizeof(uint64_t), 512));
if (bdrv_pread(bs->file, s->l1_table_offset, s->l1_table, s->l1_size * sizeof(uint64_t)) !=
s->l1_size * sizeof(uint64_t))
goto fail;
for(i = 0;i < s->l1_size; i++) {
be64_to_cpus(&s->l1_table[i]);
}
}
/* alloc L2 cache */
s->l2_cache = qemu_malloc(s->l2_size * L2_CACHE_SIZE * sizeof(uint64_t));
s->cluster_cache = qemu_malloc(s->cluster_size);
/* one more sector for decompressed data alignment */
s->cluster_data = qemu_malloc(QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size
+ 512);
s->cluster_cache_offset = -1;
if (qcow2_refcount_init(bs) < 0)
goto fail;
QLIST_INIT(&s->cluster_allocs);
/* read qcow2 extensions */
if (header.backing_file_offset)
ext_end = header.backing_file_offset;
else
ext_end = s->cluster_size;
if (qcow_read_extensions(bs, sizeof(header), ext_end))
goto fail;
/* read the backing file name */
if (header.backing_file_offset != 0) {
len = header.backing_file_size;
if (len > 1023)
len = 1023;
if (bdrv_pread(bs->file, header.backing_file_offset, bs->backing_file, len) != len)
goto fail;
bs->backing_file[len] = '\0';
}
if (qcow2_read_snapshots(bs) < 0)
goto fail;
#ifdef DEBUG_ALLOC
qcow2_check_refcounts(bs);
#endif
return 0;
fail:
qcow2_free_snapshots(bs);
qcow2_refcount_close(bs);
qemu_free(s->l1_table);
qemu_free(s->l2_cache);
qemu_free(s->cluster_cache);
qemu_free(s->cluster_data);
return -1;
}
static int qcow_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 qcow_is_allocated(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
uint64_t cluster_offset;
int ret;
*pnum = nb_sectors;
/* FIXME We can get errors here, but the bdrv_is_allocated interface can't
* pass them on today */
ret = qcow2_get_cluster_offset(bs, sector_num << 9, pnum, &cluster_offset);
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(qiov, 0, 512 * (nb_sectors - n1));
return n1;
}
typedef struct QCowAIOCB {
BlockDriverAIOCB common;
int64_t sector_num;
QEMUIOVector *qiov;
int remaining_sectors;
int cur_nr_sectors; /* number of sectors in current iteration */
uint64_t bytes_done;
uint64_t cluster_offset;
uint8_t *cluster_data;
BlockDriverAIOCB *hd_aiocb;
QEMUIOVector hd_qiov;
QEMUBH *bh;
QCowL2Meta l2meta;
QLIST_ENTRY(QCowAIOCB) next_depend;
} QCowAIOCB;
static void qcow_aio_cancel(BlockDriverAIOCB *blockacb)
{
QCowAIOCB *acb = container_of(blockacb, QCowAIOCB, common);
if (acb->hd_aiocb)
bdrv_aio_cancel(acb->hd_aiocb);
qemu_aio_release(acb);
}
static AIOPool qcow_aio_pool = {
.aiocb_size = sizeof(QCowAIOCB),
.cancel = qcow_aio_cancel,
};
static void qcow_aio_read_cb(void *opaque, int ret);
static void qcow_aio_read_bh(void *opaque)
{
QCowAIOCB *acb = opaque;
qemu_bh_delete(acb->bh);
acb->bh = NULL;
qcow_aio_read_cb(opaque, 0);
}
static int qcow_schedule_bh(QEMUBHFunc *cb, QCowAIOCB *acb)
{
if (acb->bh)
return -EIO;
acb->bh = qemu_bh_new(cb, acb);
if (!acb->bh)
return -EIO;
qemu_bh_schedule(acb->bh);
return 0;
}
static void qcow_aio_read_cb(void *opaque, int ret)
{
QCowAIOCB *acb = opaque;
BlockDriverState *bs = acb->common.bs;
BDRVQcowState *s = bs->opaque;
int index_in_cluster, n1;
acb->hd_aiocb = NULL;
if (ret < 0)
goto done;
/* post process the read buffer */
if (!acb->cluster_offset) {
/* nothing to do */
} else if (acb->cluster_offset & QCOW_OFLAG_COMPRESSED) {
/* nothing to do */
} else {
if (s->crypt_method) {
qcow2_encrypt_sectors(s, acb->sector_num, acb->cluster_data,
acb->cluster_data, acb->cur_nr_sectors, 0, &s->aes_decrypt_key);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_copy(&acb->hd_qiov, acb->qiov, acb->bytes_done,
acb->cur_nr_sectors * 512);
qemu_iovec_from_buffer(&acb->hd_qiov, acb->cluster_data,
512 * acb->cur_nr_sectors);
}
}
acb->remaining_sectors -= acb->cur_nr_sectors;
acb->sector_num += acb->cur_nr_sectors;
acb->bytes_done += acb->cur_nr_sectors * 512;
if (acb->remaining_sectors == 0) {
/* request completed */
ret = 0;
goto done;
}
/* prepare next AIO request */
acb->cur_nr_sectors = acb->remaining_sectors;
if (s->crypt_method) {
acb->cur_nr_sectors = MIN(acb->cur_nr_sectors,
QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);
}
ret = qcow2_get_cluster_offset(bs, acb->sector_num << 9,
&acb->cur_nr_sectors, &acb->cluster_offset);
if (ret < 0) {
goto done;
}
index_in_cluster = acb->sector_num & (s->cluster_sectors - 1);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_copy(&acb->hd_qiov, acb->qiov, acb->bytes_done,
acb->cur_nr_sectors * 512);
if (!acb->cluster_offset) {
if (bs->backing_hd) {
/* read from the base image */
n1 = qcow2_backing_read1(bs->backing_hd, &acb->hd_qiov,
acb->sector_num, acb->cur_nr_sectors);
if (n1 > 0) {
BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);
acb->hd_aiocb = bdrv_aio_readv(bs->backing_hd, acb->sector_num,
&acb->hd_qiov, acb->cur_nr_sectors,
qcow_aio_read_cb, acb);
if (acb->hd_aiocb == NULL)
goto done;
} else {
ret = qcow_schedule_bh(qcow_aio_read_bh, acb);
if (ret < 0)
goto done;
}
} else {
/* Note: in this case, no need to wait */
qemu_iovec_memset(&acb->hd_qiov, 0, 512 * acb->cur_nr_sectors);
ret = qcow_schedule_bh(qcow_aio_read_bh, acb);
if (ret < 0)
goto done;
}
} else if (acb->cluster_offset & QCOW_OFLAG_COMPRESSED) {
/* add AIO support for compressed blocks ? */
if (qcow2_decompress_cluster(bs, acb->cluster_offset) < 0)
goto done;
qemu_iovec_from_buffer(&acb->hd_qiov,
s->cluster_cache + index_in_cluster * 512,
512 * acb->cur_nr_sectors);
ret = qcow_schedule_bh(qcow_aio_read_bh, acb);
if (ret < 0)
goto done;
} else {
if ((acb->cluster_offset & 511) != 0) {
ret = -EIO;
goto done;
}
if (s->crypt_method) {
/*
* For encrypted images, read everything into a temporary
* contiguous buffer on which the AES functions can work.
*/
if (!acb->cluster_data) {
acb->cluster_data =
qemu_mallocz(QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
}
assert(acb->cur_nr_sectors <=
QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_add(&acb->hd_qiov, acb->cluster_data,
512 * acb->cur_nr_sectors);
}
BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
acb->hd_aiocb = bdrv_aio_readv(bs->file,
(acb->cluster_offset >> 9) + index_in_cluster,
&acb->hd_qiov, acb->cur_nr_sectors,
qcow_aio_read_cb, acb);
if (acb->hd_aiocb == NULL) {
ret = -EIO;
goto done;
}
}
return;
done:
acb->common.cb(acb->common.opaque, ret);
qemu_iovec_destroy(&acb->hd_qiov);
qemu_aio_release(acb);
}
static QCowAIOCB *qcow_aio_setup(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb, void *opaque, int is_write)
{
QCowAIOCB *acb;
acb = qemu_aio_get(&qcow_aio_pool, bs, cb, opaque);
if (!acb)
return NULL;
acb->hd_aiocb = NULL;
acb->sector_num = sector_num;
acb->qiov = qiov;
qemu_iovec_init(&acb->hd_qiov, qiov->niov);
acb->bytes_done = 0;
acb->remaining_sectors = nb_sectors;
acb->cur_nr_sectors = 0;
acb->cluster_offset = 0;
acb->l2meta.nb_clusters = 0;
QLIST_INIT(&acb->l2meta.dependent_requests);
return acb;
}
static BlockDriverAIOCB *qcow_aio_readv(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb, void *opaque)
{
QCowAIOCB *acb;
acb = qcow_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 0);
if (!acb)
return NULL;
qcow_aio_read_cb(acb, 0);
return &acb->common;
}
static void qcow_aio_write_cb(void *opaque, int ret);
static void run_dependent_requests(QCowL2Meta *m)
{
QCowAIOCB *req;
QCowAIOCB *next;
/* Take the request off the list of running requests */
if (m->nb_clusters != 0) {
QLIST_REMOVE(m, next_in_flight);
}
/* Restart all dependent requests */
QLIST_FOREACH_SAFE(req, &m->dependent_requests, next_depend, next) {
qcow_aio_write_cb(req, 0);
}
/* Empty the list for the next part of the request */
QLIST_INIT(&m->dependent_requests);
}
static void qcow_aio_write_cb(void *opaque, int ret)
{
QCowAIOCB *acb = opaque;
BlockDriverState *bs = acb->common.bs;
BDRVQcowState *s = bs->opaque;
int index_in_cluster;
int n_end;
acb->hd_aiocb = NULL;
if (ret >= 0) {
ret = qcow2_alloc_cluster_link_l2(bs, &acb->l2meta);
}
run_dependent_requests(&acb->l2meta);
if (ret < 0)
goto done;
acb->remaining_sectors -= acb->cur_nr_sectors;
acb->sector_num += acb->cur_nr_sectors;
acb->bytes_done += acb->cur_nr_sectors * 512;
if (acb->remaining_sectors == 0) {
/* request completed */
ret = 0;
goto done;
}
index_in_cluster = acb->sector_num & (s->cluster_sectors - 1);
n_end = index_in_cluster + acb->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, acb->sector_num << 9,
index_in_cluster, n_end, &acb->cur_nr_sectors, &acb->l2meta);
if (ret < 0) {
goto done;
}
acb->cluster_offset = acb->l2meta.cluster_offset;
/* Need to wait for another request? If so, we are done for now. */
if (acb->l2meta.nb_clusters == 0 && acb->l2meta.depends_on != NULL) {
QLIST_INSERT_HEAD(&acb->l2meta.depends_on->dependent_requests,
acb, next_depend);
return;
}
assert((acb->cluster_offset & 511) == 0);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_copy(&acb->hd_qiov, acb->qiov, acb->bytes_done,
acb->cur_nr_sectors * 512);
if (s->crypt_method) {
if (!acb->cluster_data) {
acb->cluster_data = qemu_mallocz(QCOW_MAX_CRYPT_CLUSTERS *
s->cluster_size);
}
assert(acb->hd_qiov.size <= QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
qemu_iovec_to_buffer(&acb->hd_qiov, acb->cluster_data);
qcow2_encrypt_sectors(s, acb->sector_num, acb->cluster_data,
acb->cluster_data, acb->cur_nr_sectors, 1, &s->aes_encrypt_key);
qemu_iovec_reset(&acb->hd_qiov);
qemu_iovec_add(&acb->hd_qiov, acb->cluster_data,
acb->cur_nr_sectors * 512);
}
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
acb->hd_aiocb = bdrv_aio_writev(bs->file,
(acb->cluster_offset >> 9) + index_in_cluster,
&acb->hd_qiov, acb->cur_nr_sectors,
qcow_aio_write_cb, acb);
if (acb->hd_aiocb == NULL) {
ret = -EIO;
goto fail;
}
return;
fail:
if (acb->l2meta.nb_clusters != 0) {
QLIST_REMOVE(&acb->l2meta, next_in_flight);
}
done:
acb->common.cb(acb->common.opaque, ret);
qemu_iovec_destroy(&acb->hd_qiov);
qemu_aio_release(acb);
}
static BlockDriverAIOCB *qcow_aio_writev(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb, void *opaque)
{
BDRVQcowState *s = bs->opaque;
QCowAIOCB *acb;
s->cluster_cache_offset = -1; /* disable compressed cache */
acb = qcow_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 1);
if (!acb)
return NULL;
qcow_aio_write_cb(acb, 0);
return &acb->common;
}
static void qcow_close(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
qemu_free(s->l1_table);
qemu_free(s->l2_cache);
qemu_free(s->cluster_cache);
qemu_free(s->cluster_data);
qcow2_refcount_close(bs);
}
/*
* Updates the variable length parts of the qcow2 header, 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.
*/
static int qcow2_update_ext_header(BlockDriverState *bs,
const char *backing_file, const char *backing_fmt)
{
size_t backing_file_len = 0;
size_t backing_fmt_len = 0;
BDRVQcowState *s = bs->opaque;
QCowExtension ext_backing_fmt = {0, 0};
int ret;
/* Backing file format doesn't make sense without a backing file */
if (backing_fmt && !backing_file) {
return -EINVAL;
}
/* Prepare the backing file format extension if needed */
if (backing_fmt) {
ext_backing_fmt.len = cpu_to_be32(strlen(backing_fmt));
ext_backing_fmt.magic = cpu_to_be32(QCOW_EXT_MAGIC_BACKING_FORMAT);
backing_fmt_len = ((sizeof(ext_backing_fmt)
+ strlen(backing_fmt) + 7) & ~7);
}
/* Check if we can fit the new header into the first cluster */
if (backing_file) {
backing_file_len = strlen(backing_file);
}
size_t header_size = sizeof(QCowHeader) + backing_file_len
+ backing_fmt_len;
if (header_size > s->cluster_size) {
return -ENOSPC;
}
/* Rewrite backing file name and qcow2 extensions */
size_t ext_size = header_size - sizeof(QCowHeader);
uint8_t buf[ext_size];
size_t offset = 0;
size_t backing_file_offset = 0;
if (backing_file) {
if (backing_fmt) {
int padding = backing_fmt_len -
(sizeof(ext_backing_fmt) + strlen(backing_fmt));
memcpy(buf + offset, &ext_backing_fmt, sizeof(ext_backing_fmt));
offset += sizeof(ext_backing_fmt);
memcpy(buf + offset, backing_fmt, strlen(backing_fmt));
offset += strlen(backing_fmt);
memset(buf + offset, 0, padding);
offset += padding;
}
memcpy(buf + offset, backing_file, backing_file_len);
backing_file_offset = sizeof(QCowHeader) + offset;
}
ret = bdrv_pwrite_sync(bs->file, sizeof(QCowHeader), buf, ext_size);
if (ret < 0) {
goto fail;
}
/* Update header fields */
uint64_t be_backing_file_offset = cpu_to_be64(backing_file_offset);
uint32_t be_backing_file_size = cpu_to_be32(backing_file_len);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, backing_file_offset),
&be_backing_file_offset, sizeof(uint64_t));
if (ret < 0) {
goto fail;
}
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, backing_file_size),
&be_backing_file_size, sizeof(uint32_t));
if (ret < 0) {
goto fail;
}
ret = 0;
fail:
return ret;
}
static int qcow2_change_backing_file(BlockDriverState *bs,
const char *backing_file, const char *backing_fmt)
{
return qcow2_update_ext_header(bs, backing_file, backing_fmt);
}
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;
QLIST_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(&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 qcow_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)
{
/* Calulate 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\n",
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(QCOW_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);
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 = qemu_mallocz(cluster_size);
ret = bdrv_pwrite(bs, cluster_size, refcount_table, cluster_size);
qemu_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_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 qcow_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 = 65536;
int prealloc = 0;
/* 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;
}
}
options++;
}
if (backing_file && prealloc) {
fprintf(stderr, "Backing file and preallocation cannot be used at "
"the same time\n");
return -EINVAL;
}
return qcow_create2(filename, sectors, backing_file, backing_fmt, flags,
cluster_size, prealloc, options);
}
static int qcow_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 int qcow2_truncate(BlockDriverState *bs, int64_t offset)
{
BDRVQcowState *s = bs->opaque;
int ret, new_l1_size;
if (offset & 511) {
return -EINVAL;
}
/* cannot proceed if image has snapshots */
if (s->nb_snapshots) {
return -ENOTSUP;
}
/* shrinking is currently not supported */
if (offset < bs->total_sectors * 512) {
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 qcow_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 = qemu_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) {
qemu_free(out_buf);
return -1;
}
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) {
qemu_free(out_buf);
deflateEnd(&strm);
return -1;
}
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 */
bdrv_write(bs, sector_num, buf, s->cluster_sectors);
} else {
cluster_offset = qcow2_alloc_compressed_cluster_offset(bs,
sector_num << 9, out_len);
if (!cluster_offset)
return -1;
cluster_offset &= s->cluster_offset_mask;
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_COMPRESSED);
if (bdrv_pwrite(bs->file, cluster_offset, out_buf, out_len) != out_len) {
qemu_free(out_buf);
return -1;
}
}
qemu_free(out_buf);
return 0;
}
static int qcow_flush(BlockDriverState *bs)
{
return bdrv_flush(bs->file);
}
static BlockDriverAIOCB *qcow_aio_flush(BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque)
{
return bdrv_aio_flush(bs->file, cb, opaque);
}
static int64_t qcow_vm_state_offset(BDRVQcowState *s)
{
return (int64_t)s->l1_vm_state_index << (s->cluster_bits + s->l2_bits);
}
static int qcow_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
BDRVQcowState *s = bs->opaque;
bdi->cluster_size = s->cluster_size;
bdi->vm_state_offset = qcow_vm_state_offset(s);
return 0;
}
static int qcow_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 qcow_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, qcow_vm_state_offset(s) + pos, buf, size);
bs->growable = growable;
return ret;
}
static int qcow_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, qcow_vm_state_offset(s) + pos, buf, size);
bs->growable = growable;
return ret;
}
static QEMUOptionParameter qcow_create_options[] = {
{
.name = BLOCK_OPT_SIZE,
.type = OPT_SIZE,
.help = "Virtual disk size"
},
{
.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"
},
{
.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 = qcow_probe,
.bdrv_open = qcow_open,
.bdrv_close = qcow_close,
.bdrv_create = qcow_create,
.bdrv_flush = qcow_flush,
.bdrv_is_allocated = qcow_is_allocated,
.bdrv_set_key = qcow_set_key,
.bdrv_make_empty = qcow_make_empty,
.bdrv_aio_readv = qcow_aio_readv,
.bdrv_aio_writev = qcow_aio_writev,
.bdrv_aio_flush = qcow_aio_flush,
.bdrv_truncate = qcow2_truncate,
.bdrv_write_compressed = qcow_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 = qcow_get_info,
.bdrv_save_vmstate = qcow_save_vmstate,
.bdrv_load_vmstate = qcow_load_vmstate,
.bdrv_change_backing_file = qcow2_change_backing_file,
.create_options = qcow_create_options,
.bdrv_check = qcow_check,
};
static void bdrv_qcow2_init(void)
{
bdrv_register(&bdrv_qcow2);
}
block_init(bdrv_qcow2_init);
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