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FRET-qemu/block.c
bellard 33e3963e1b added user mode Linux Copy On Write disk image support - added -snapshot support (initial patch by Rusty Russell) 
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@309 c046a42c-6fe2-441c-8c8c-71466251a162
2003-07-06 17:15:21 +00:00

327 lines
9.1 KiB
C
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/*
* QEMU System Emulator block driver
*
* Copyright (c) 2003 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 <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <getopt.h>
#include <inttypes.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
#include <malloc.h>
#include <termios.h>
#include <sys/poll.h>
#include <errno.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include "vl.h"
#define NO_THUNK_TYPE_SIZE
#include "thunk.h"
struct BlockDriverState {
int fd; /* if -1, only COW mappings */
int64_t total_sectors;
int read_only;
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;
int cow_fd;
int64_t cow_sectors_offset;
char filename[1024];
};
BlockDriverState *bdrv_open(const char *filename, int snapshot)
{
BlockDriverState *bs;
int fd, cow_fd;
int64_t size;
char template[] = "/tmp/vl.XXXXXX";
struct cow_header_v2 cow_header;
struct stat st;
bs = malloc(sizeof(BlockDriverState));
if(!bs)
return NULL;
bs->read_only = 0;
bs->fd = -1;
bs->cow_fd = -1;
bs->cow_bitmap = NULL;
strcpy(bs->filename, filename);
/* open standard HD image */
fd = open(filename, O_RDWR | O_LARGEFILE);
if (fd < 0) {
/* read only image on disk */
fd = open(filename, O_RDONLY | O_LARGEFILE);
if (fd < 0) {
perror(filename);
goto fail;
}
if (!snapshot)
bs->read_only = 1;
}
bs->fd = fd;
/* see if it is a cow image */
if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
fprintf(stderr, "%s: could not read header\n", filename);
goto fail;
}
if (cow_header.magic == htonl(COW_MAGIC) &&
cow_header.version == htonl(COW_VERSION)) {
/* cow image found */
size = cow_header.size;
#ifndef WORDS_BIGENDIAN
size = bswap64(size);
#endif
bs->total_sectors = size / 512;
bs->cow_fd = fd;
bs->fd = -1;
if (cow_header.backing_file[0] != '\0') {
if (stat(cow_header.backing_file, &st) != 0) {
fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
goto fail;
}
if (st.st_mtime != htonl(cow_header.mtime)) {
fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
goto fail;
}
fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
if (fd < 0)
goto fail;
bs->fd = fd;
}
/* mmap the bitmap */
bs->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
bs->cow_bitmap_size,
PROT_READ | PROT_WRITE,
MAP_SHARED, bs->cow_fd, 0);
if (bs->cow_bitmap_addr == MAP_FAILED)
goto fail;
bs->cow_bitmap = bs->cow_bitmap_addr + sizeof(cow_header);
bs->cow_sectors_offset = (bs->cow_bitmap_size + 511) & ~511;
snapshot = 0;
} else {
/* standard raw image */
size = lseek64(fd, 0, SEEK_END);
bs->total_sectors = size / 512;
bs->fd = fd;
}
if (snapshot) {
/* create a temporary COW file */
cow_fd = mkstemp(template);
if (cow_fd < 0)
goto fail;
bs->cow_fd = cow_fd;
unlink(template);
/* just need to allocate bitmap */
bs->cow_bitmap_size = (bs->total_sectors + 7) >> 3;
bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
bs->cow_bitmap_size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (bs->cow_bitmap_addr == MAP_FAILED)
goto fail;
bs->cow_bitmap = bs->cow_bitmap_addr;
bs->cow_sectors_offset = 0;
}
return bs;
fail:
bdrv_close(bs);
return NULL;
}
void bdrv_close(BlockDriverState *bs)
{
/* we unmap the mapping so that it is written to the COW file */
if (bs->cow_bitmap_addr)
munmap(bs->cow_bitmap_addr, bs->cow_bitmap_size);
if (bs->cow_fd >= 0)
close(bs->cow_fd);
if (bs->fd >= 0)
close(bs->fd);
free(bs);
}
static inline void 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 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;
}
/* commit COW file into the raw image */
int bdrv_commit(BlockDriverState *bs)
{
int64_t i;
uint8_t *cow_bitmap;
if (!bs->cow_bitmap) {
fprintf(stderr, "Already committed to %s\n", bs->filename);
return 0;
}
if (bs->read_only) {
fprintf(stderr, "Can't commit to %s: read-only\n", bs->filename);
return -1;
}
cow_bitmap = bs->cow_bitmap;
for (i = 0; i < bs->total_sectors; i++) {
if (is_bit_set(cow_bitmap, i)) {
unsigned char sector[512];
if (bdrv_read(bs, i, sector, 1) != 0) {
fprintf(stderr, "Error reading sector %lli: aborting commit\n",
(long long)i);
return -1;
}
/* Make bdrv_write write to real file for a moment. */
bs->cow_bitmap = NULL;
if (bdrv_write(bs, i, sector, 1) != 0) {
fprintf(stderr, "Error writing sector %lli: aborting commit\n",
(long long)i);
bs->cow_bitmap = cow_bitmap;
return -1;
}
bs->cow_bitmap = cow_bitmap;
}
}
fprintf(stderr, "Committed snapshot to %s\n", bs->filename);
return 0;
}
/* return -1 if error */
int bdrv_read(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
int ret, n, fd;
int64_t offset;
while (nb_sectors > 0) {
if (is_changed(bs->cow_bitmap, sector_num, nb_sectors, &n)) {
fd = bs->cow_fd;
offset = bs->cow_sectors_offset;
} else {
fd = bs->fd;
offset = 0;
}
if (fd < 0) {
/* no file, just return empty sectors */
memset(buf, 0, n * 512);
} else {
offset += sector_num * 512;
lseek64(fd, offset, SEEK_SET);
ret = read(fd, buf, n * 512);
if (ret != n * 512) {
return -1;
}
}
nb_sectors -= n;
sector_num += n;
buf += n * 512;
}
return 0;
}
/* return -1 if error */
int bdrv_write(BlockDriverState *bs, int64_t sector_num,
const uint8_t *buf, int nb_sectors)
{
int ret, fd, i;
int64_t offset, retl;
if (bs->read_only)
return -1;
if (bs->cow_bitmap) {
fd = bs->cow_fd;
offset = bs->cow_sectors_offset;
} else {
fd = bs->fd;
offset = 0;
}
offset += sector_num * 512;
retl = lseek64(fd, offset, SEEK_SET);
if (retl == -1) {
return -1;
}
ret = write(fd, buf, nb_sectors * 512);
if (ret != nb_sectors * 512) {
return -1;
}
if (bs->cow_bitmap) {
for (i = 0; i < nb_sectors; i++)
set_bit(bs->cow_bitmap, sector_num + i);
}
return 0;
}
void bdrv_get_geometry(BlockDriverState *bs, int64_t *nb_sectors_ptr)
{
*nb_sectors_ptr = bs->total_sectors;
}
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