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qcow2: Simplify image creation

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Instead of doing lots of magic for setting up initial refcount blocks and stuff
create a minimal (inconsistent) image, open it and initialize the rest with
regular qcow2 functions.

This is a complete rewrite of the image creation function. The old
implementating is #ifdef'd out and will be removed by the next patch (removing
it here would have made the diff unreadable because diff tries to find
similarities when it's really a rewrite)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2010-06-11 21:37:37 +02:00
parent 72893756e0
commit a9420734b6
1 changed files with 132 additions and 1 deletions
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133
block/qcow2.c
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@ -27,6 +27,7 @@
#include <zlib.h>
#include "aes.h"
#include "block/qcow2.h"
#include "qemu-error.h"
/*
Differences with QCOW:
@ -794,6 +795,7 @@ static int qcow2_change_backing_file(BlockDriverState *bs,
return qcow2_update_ext_header(bs, backing_file, backing_fmt);
}
#if 0
static int get_bits_from_size(size_t size)
{
int res = 0;
@ -814,6 +816,7 @@ static int get_bits_from_size(size_t size)
return res;
}
#endif
static int preallocate(BlockDriverState *bs)
@ -869,6 +872,7 @@ static int preallocate(BlockDriverState *bs)
return 0;
}
#if 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)
@ -1066,6 +1070,133 @@ exit:
return ret;
}
#else
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;
}
#endif
static int qcow_create(const char *filename, QEMUOptionParameter *options)
{
@ -1111,7 +1242,7 @@ static int qcow_create(const char *filename, QEMUOptionParameter *options)
}
return qcow_create2(filename, sectors, backing_file, backing_fmt, flags,
cluster_size, prealloc);
cluster_size, prealloc, options);
}
static int qcow_make_empty(BlockDriverState *bs)