268 lines
7.7 KiB
C
268 lines
7.7 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.
|
|
*/
|
|
#ifndef _WIN32
|
|
#include "vl.h"
|
|
#include "block_int.h"
|
|
#include <sys/mman.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 {
|
|
int fd;
|
|
uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
|
|
uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
|
|
int cow_bitmap_size;
|
|
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, const char *filename, int flags)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
int fd;
|
|
struct cow_header_v2 cow_header;
|
|
int64_t size;
|
|
|
|
fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
|
|
if (fd < 0) {
|
|
fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
|
|
if (fd < 0)
|
|
return -1;
|
|
}
|
|
s->fd = fd;
|
|
/* see if it is a cow image */
|
|
if (read(fd, &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);
|
|
|
|
/* mmap the bitmap */
|
|
s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
|
|
s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
|
|
s->cow_bitmap_size,
|
|
PROT_READ | PROT_WRITE,
|
|
MAP_SHARED, s->fd, 0);
|
|
if (s->cow_bitmap_addr == MAP_FAILED)
|
|
goto fail;
|
|
s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
|
|
s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
|
|
return 0;
|
|
fail:
|
|
close(fd);
|
|
return -1;
|
|
}
|
|
|
|
static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
|
|
{
|
|
bitmap[bitnum / 8] |= (1 << (bitnum%8));
|
|
}
|
|
|
|
static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
|
|
{
|
|
return !!(bitmap[bitnum / 8] & (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 inline int is_changed(uint8_t *bitmap,
|
|
int64_t sector_num, int nb_sectors,
|
|
int *num_same)
|
|
{
|
|
int changed;
|
|
|
|
if (!bitmap || nb_sectors == 0) {
|
|
*num_same = nb_sectors;
|
|
return 0;
|
|
}
|
|
|
|
changed = is_bit_set(bitmap, sector_num);
|
|
for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
|
|
if (is_bit_set(bitmap, sector_num + *num_same) != changed)
|
|
break;
|
|
}
|
|
|
|
return changed;
|
|
}
|
|
|
|
static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
|
|
int nb_sectors, int *pnum)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
|
|
}
|
|
|
|
static int 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 (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
|
|
lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
|
|
ret = read(s->fd, 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 int cow_write(BlockDriverState *bs, int64_t sector_num,
|
|
const uint8_t *buf, int nb_sectors)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
int ret, i;
|
|
|
|
lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
|
|
ret = write(s->fd, buf, nb_sectors * 512);
|
|
if (ret != nb_sectors * 512)
|
|
return -1;
|
|
for (i = 0; i < nb_sectors; i++)
|
|
cow_set_bit(s->cow_bitmap, sector_num + i);
|
|
return 0;
|
|
}
|
|
|
|
static void cow_close(BlockDriverState *bs)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
|
|
close(s->fd);
|
|
}
|
|
|
|
static int cow_create(const char *filename, int64_t image_sectors,
|
|
const char *image_filename, int flags)
|
|
{
|
|
int fd, cow_fd;
|
|
struct cow_header_v2 cow_header;
|
|
struct stat st;
|
|
|
|
if (flags)
|
|
return -ENOTSUP;
|
|
|
|
cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
|
|
0644);
|
|
if (cow_fd < 0)
|
|
return -1;
|
|
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);
|
|
|
|
fd = open(image_filename, O_RDONLY | O_BINARY);
|
|
if (fd < 0) {
|
|
close(cow_fd);
|
|
goto mtime_fail;
|
|
}
|
|
if (fstat(fd, &st) != 0) {
|
|
close(fd);
|
|
goto mtime_fail;
|
|
}
|
|
close(fd);
|
|
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);
|
|
write(cow_fd, &cow_header, sizeof(cow_header));
|
|
/* resize to include at least all the bitmap */
|
|
ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
|
|
close(cow_fd);
|
|
return 0;
|
|
}
|
|
|
|
static void cow_flush(BlockDriverState *bs)
|
|
{
|
|
BDRVCowState *s = bs->opaque;
|
|
fsync(s->fd);
|
|
}
|
|
|
|
BlockDriver bdrv_cow = {
|
|
"cow",
|
|
sizeof(BDRVCowState),
|
|
cow_probe,
|
|
cow_open,
|
|
cow_read,
|
|
cow_write,
|
|
cow_close,
|
|
cow_create,
|
|
cow_flush,
|
|
cow_is_allocated,
|
|
};
|
|
#endif
|