mirror of
https://github.com/qemu/qemu.git
synced 2024-11-25 11:53:39 +08:00
349 lines
9.3 KiB
C
349 lines
9.3 KiB
C
/*
|
|
* Block driver for the COW format
|
|
*
|
|
* Copyright (c) 2004 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"
|
|
|
|
/**************************************************************/
|
|
/* COW block driver using file system holes */
|
|
|
|
/* user mode linux compatible COW file */
|
|
#define COW_MAGIC 0x4f4f4f4d /* MOOO */
|
|
#define COW_VERSION 2
|
|
|
|
struct cow_header_v2 {
|
|
uint32_t magic;
|
|
uint32_t version;
|
|
char backing_file[1024];
|
|
int32_t mtime;
|
|
uint64_t size;
|
|
uint32_t sectorsize;
|
|
};
|
|
|
|
typedef struct BDRVCowState {
|
|
CoMutex lock;
|
|
int64_t cow_sectors_offset;
|
|
} BDRVCowState;
|
|
|
|
static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
|
|
{
|
|
const struct cow_header_v2 *cow_header = (const void *)buf;
|
|
|
|
if (buf_size >= sizeof(struct cow_header_v2) &&
|
|
be32_to_cpu(cow_header->magic) == COW_MAGIC &&
|
|
be32_to_cpu(cow_header->version) == COW_VERSION)
|
|
return 100;
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
static int cow_open(BlockDriverState *bs, int flags)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
struct cow_header_v2 cow_header;
|
|
int bitmap_size;
|
|
int64_t size;
|
|
|
|
/* see if it is a cow image */
|
|
if (bdrv_pread(bs->file, 0, &cow_header, sizeof(cow_header)) !=
|
|
sizeof(cow_header)) {
|
|
goto fail;
|
|
}
|
|
|
|
if (be32_to_cpu(cow_header.magic) != COW_MAGIC ||
|
|
be32_to_cpu(cow_header.version) != COW_VERSION) {
|
|
goto fail;
|
|
}
|
|
|
|
/* cow image found */
|
|
size = be64_to_cpu(cow_header.size);
|
|
bs->total_sectors = size / 512;
|
|
|
|
pstrcpy(bs->backing_file, sizeof(bs->backing_file),
|
|
cow_header.backing_file);
|
|
|
|
bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
|
|
s->cow_sectors_offset = (bitmap_size + 511) & ~511;
|
|
qemu_co_mutex_init(&s->lock);
|
|
return 0;
|
|
fail:
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* XXX(hch): right now these functions are extremely ineffcient.
|
|
* We should just read the whole bitmap we'll need in one go instead.
|
|
*/
|
|
static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
|
|
{
|
|
uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
|
|
uint8_t bitmap;
|
|
int ret;
|
|
|
|
ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
|
|
if (ret < 0) {
|
|
return ret;
|
|
}
|
|
|
|
bitmap |= (1 << (bitnum % 8));
|
|
|
|
ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap));
|
|
if (ret < 0) {
|
|
return ret;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)
|
|
{
|
|
uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
|
|
uint8_t bitmap;
|
|
int ret;
|
|
|
|
ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
|
|
if (ret < 0) {
|
|
return ret;
|
|
}
|
|
|
|
return !!(bitmap & (1 << (bitnum % 8)));
|
|
}
|
|
|
|
/* Return true if first block has been changed (ie. current version is
|
|
* in COW file). Set the number of continuous blocks for which that
|
|
* is true. */
|
|
static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs,
|
|
int64_t sector_num, int nb_sectors, int *num_same)
|
|
{
|
|
int changed;
|
|
|
|
if (nb_sectors == 0) {
|
|
*num_same = nb_sectors;
|
|
return 0;
|
|
}
|
|
|
|
changed = is_bit_set(bs, sector_num);
|
|
if (changed < 0) {
|
|
return 0; /* XXX: how to return I/O errors? */
|
|
}
|
|
|
|
for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
|
|
if (is_bit_set(bs, sector_num + *num_same) != changed)
|
|
break;
|
|
}
|
|
|
|
return changed;
|
|
}
|
|
|
|
static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
|
|
int nb_sectors)
|
|
{
|
|
int error = 0;
|
|
int i;
|
|
|
|
for (i = 0; i < nb_sectors; i++) {
|
|
error = cow_set_bit(bs, sector_num + i);
|
|
if (error) {
|
|
break;
|
|
}
|
|
}
|
|
|
|
return error;
|
|
}
|
|
|
|
static int coroutine_fn cow_read(BlockDriverState *bs, int64_t sector_num,
|
|
uint8_t *buf, int nb_sectors)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
int ret, n;
|
|
|
|
while (nb_sectors > 0) {
|
|
if (bdrv_co_is_allocated(bs, sector_num, nb_sectors, &n)) {
|
|
ret = bdrv_pread(bs->file,
|
|
s->cow_sectors_offset + sector_num * 512,
|
|
buf, n * 512);
|
|
if (ret != n * 512)
|
|
return -1;
|
|
} else {
|
|
if (bs->backing_hd) {
|
|
/* read from the base image */
|
|
ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
|
|
if (ret < 0)
|
|
return -1;
|
|
} else {
|
|
memset(buf, 0, n * 512);
|
|
}
|
|
}
|
|
nb_sectors -= n;
|
|
sector_num += n;
|
|
buf += n * 512;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static coroutine_fn int cow_co_read(BlockDriverState *bs, int64_t sector_num,
|
|
uint8_t *buf, int nb_sectors)
|
|
{
|
|
int ret;
|
|
BDRVCowState *s = bs->opaque;
|
|
qemu_co_mutex_lock(&s->lock);
|
|
ret = cow_read(bs, sector_num, buf, nb_sectors);
|
|
qemu_co_mutex_unlock(&s->lock);
|
|
return ret;
|
|
}
|
|
|
|
static int cow_write(BlockDriverState *bs, int64_t sector_num,
|
|
const uint8_t *buf, int nb_sectors)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
int ret;
|
|
|
|
ret = bdrv_pwrite(bs->file, s->cow_sectors_offset + sector_num * 512,
|
|
buf, nb_sectors * 512);
|
|
if (ret != nb_sectors * 512)
|
|
return -1;
|
|
|
|
return cow_update_bitmap(bs, sector_num, nb_sectors);
|
|
}
|
|
|
|
static coroutine_fn int cow_co_write(BlockDriverState *bs, int64_t sector_num,
|
|
const uint8_t *buf, int nb_sectors)
|
|
{
|
|
int ret;
|
|
BDRVCowState *s = bs->opaque;
|
|
qemu_co_mutex_lock(&s->lock);
|
|
ret = cow_write(bs, sector_num, buf, nb_sectors);
|
|
qemu_co_mutex_unlock(&s->lock);
|
|
return ret;
|
|
}
|
|
|
|
static void cow_close(BlockDriverState *bs)
|
|
{
|
|
}
|
|
|
|
static int cow_create(const char *filename, QEMUOptionParameter *options)
|
|
{
|
|
struct cow_header_v2 cow_header;
|
|
struct stat st;
|
|
int64_t image_sectors = 0;
|
|
const char *image_filename = NULL;
|
|
int ret;
|
|
BlockDriverState *cow_bs;
|
|
|
|
/* Read out options */
|
|
while (options && options->name) {
|
|
if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
|
|
image_sectors = options->value.n / 512;
|
|
} else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
|
|
image_filename = options->value.s;
|
|
}
|
|
options++;
|
|
}
|
|
|
|
ret = bdrv_create_file(filename, options);
|
|
if (ret < 0) {
|
|
return ret;
|
|
}
|
|
|
|
ret = bdrv_file_open(&cow_bs, filename, BDRV_O_RDWR);
|
|
if (ret < 0) {
|
|
return ret;
|
|
}
|
|
|
|
memset(&cow_header, 0, sizeof(cow_header));
|
|
cow_header.magic = cpu_to_be32(COW_MAGIC);
|
|
cow_header.version = cpu_to_be32(COW_VERSION);
|
|
if (image_filename) {
|
|
/* Note: if no file, we put a dummy mtime */
|
|
cow_header.mtime = cpu_to_be32(0);
|
|
|
|
if (stat(image_filename, &st) != 0) {
|
|
goto mtime_fail;
|
|
}
|
|
cow_header.mtime = cpu_to_be32(st.st_mtime);
|
|
mtime_fail:
|
|
pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
|
|
image_filename);
|
|
}
|
|
cow_header.sectorsize = cpu_to_be32(512);
|
|
cow_header.size = cpu_to_be64(image_sectors * 512);
|
|
ret = bdrv_pwrite(cow_bs, 0, &cow_header, sizeof(cow_header));
|
|
if (ret != sizeof(cow_header)) {
|
|
goto exit;
|
|
}
|
|
|
|
/* resize to include at least all the bitmap */
|
|
ret = bdrv_truncate(cow_bs,
|
|
sizeof(cow_header) + ((image_sectors + 7) >> 3));
|
|
if (ret) {
|
|
goto exit;
|
|
}
|
|
|
|
exit:
|
|
bdrv_delete(cow_bs);
|
|
return ret;
|
|
}
|
|
|
|
static coroutine_fn int cow_co_flush(BlockDriverState *bs)
|
|
{
|
|
return bdrv_co_flush(bs->file);
|
|
}
|
|
|
|
static QEMUOptionParameter cow_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"
|
|
},
|
|
{ NULL }
|
|
};
|
|
|
|
static BlockDriver bdrv_cow = {
|
|
.format_name = "cow",
|
|
.instance_size = sizeof(BDRVCowState),
|
|
|
|
.bdrv_probe = cow_probe,
|
|
.bdrv_open = cow_open,
|
|
.bdrv_close = cow_close,
|
|
.bdrv_create = cow_create,
|
|
|
|
.bdrv_read = cow_co_read,
|
|
.bdrv_write = cow_co_write,
|
|
.bdrv_co_flush_to_disk = cow_co_flush,
|
|
.bdrv_co_is_allocated = cow_co_is_allocated,
|
|
|
|
.create_options = cow_create_options,
|
|
};
|
|
|
|
static void bdrv_cow_init(void)
|
|
{
|
|
bdrv_register(&bdrv_cow);
|
|
}
|
|
|
|
block_init(bdrv_cow_init);
|