#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;
+ 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)
+BlockDriverState *bdrv_open(const char *filename, int snapshot)
{
BlockDriverState *bs;
- int fd;
+ 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;
- fd = open(filename, O_RDWR);
+ 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) {
- fd = open(filename, O_RDONLY);
+ /* read only image on disk */
+ fd = open(filename, O_RDONLY | O_LARGEFILE);
if (fd < 0) {
- close(fd);
- free(bs);
- return NULL;
+ perror(filename);
+ goto fail;
}
- bs->read_only = 1;
+ if (!snapshot)
+ bs->read_only = 1;
}
- size = lseek64(fd, 0, SEEK_END);
- bs->total_sectors = size / 512;
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)
{
- close(bs->fd);
+ /* 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;
+ 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;
+ }
- lseek64(bs->fd, sector_num * 512, SEEK_SET);
- ret = read(bs->fd, buf, nb_sectors * 512);
- if (ret != nb_sectors * 512)
- return -1;
- else
- return 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;
+ int ret, fd, i;
+ int64_t offset, retl;
if (bs->read_only)
return -1;
- lseek64(bs->fd, sector_num * 512, SEEK_SET);
- ret = write(bs->fd, buf, nb_sectors * 512);
- if (ret != nb_sectors * 512)
+ 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;
- else
- return 0;
+ }
+ 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)
projects / qemu / blobdiff