+++ /dev/null
-/*
- * 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 "qemu-common.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 = (void *)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((void *)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 = {
- .format_name = "cow",
- .instance_size = sizeof(BDRVCowState),
- .bdrv_probe = cow_probe,
- .bdrv_open = cow_open,
- .bdrv_read = cow_read,
- .bdrv_write = cow_write,
- .bdrv_close = cow_close,
- .bdrv_create = cow_create,
- .bdrv_flush = cow_flush,
- .bdrv_is_allocated = cow_is_allocated,
-};
-#endif
projects / qemu / blobdiff