2 * QEMU System Emulator block driver
4 * Copyright (c) 2003 Fabrice Bellard
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
41 #include <netinet/in.h>
45 #define NO_THUNK_TYPE_SIZE
48 struct BlockDriverState {
49 int fd; /* if -1, only COW mappings */
50 int64_t total_sectors;
53 uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
54 uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
57 int64_t cow_sectors_offset;
58 int boot_sector_enabled;
59 uint8_t boot_sector_data[512];
64 BlockDriverState *bdrv_open(const char *filename, int snapshot)
69 char template[] = "/tmp/vl.XXXXXX";
70 struct cow_header_v2 cow_header;
73 bs = malloc(sizeof(BlockDriverState));
79 bs->cow_bitmap = NULL;
80 strcpy(bs->filename, filename);
82 /* open standard HD image */
83 fd = open(filename, O_RDWR | O_LARGEFILE);
85 /* read only image on disk */
86 fd = open(filename, O_RDONLY | O_LARGEFILE);
96 /* see if it is a cow image */
97 if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
98 fprintf(stderr, "%s: could not read header\n", filename);
101 if (cow_header.magic == htonl(COW_MAGIC) &&
102 cow_header.version == htonl(COW_VERSION)) {
103 /* cow image found */
104 size = cow_header.size;
105 #ifndef WORDS_BIGENDIAN
106 size = bswap64(size);
108 bs->total_sectors = size / 512;
112 if (cow_header.backing_file[0] != '\0') {
113 if (stat(cow_header.backing_file, &st) != 0) {
114 fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
117 if (st.st_mtime != htonl(cow_header.mtime)) {
118 fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
121 fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
126 /* mmap the bitmap */
127 bs->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
128 bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
130 PROT_READ | PROT_WRITE,
131 MAP_SHARED, bs->cow_fd, 0);
132 if (bs->cow_bitmap_addr == MAP_FAILED)
134 bs->cow_bitmap = bs->cow_bitmap_addr + sizeof(cow_header);
135 bs->cow_sectors_offset = (bs->cow_bitmap_size + 511) & ~511;
138 /* standard raw image */
139 size = lseek64(fd, 0, SEEK_END);
140 bs->total_sectors = size / 512;
145 /* create a temporary COW file */
146 cow_fd = mkstemp(template);
152 /* just need to allocate bitmap */
153 bs->cow_bitmap_size = (bs->total_sectors + 7) >> 3;
154 bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
156 PROT_READ | PROT_WRITE,
157 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
158 if (bs->cow_bitmap_addr == MAP_FAILED)
160 bs->cow_bitmap = bs->cow_bitmap_addr;
161 bs->cow_sectors_offset = 0;
170 void bdrv_close(BlockDriverState *bs)
172 /* we unmap the mapping so that it is written to the COW file */
173 if (bs->cow_bitmap_addr)
174 munmap(bs->cow_bitmap_addr, bs->cow_bitmap_size);
182 static inline void set_bit(uint8_t *bitmap, int64_t bitnum)
184 bitmap[bitnum / 8] |= (1 << (bitnum%8));
187 static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
189 return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
193 /* Return true if first block has been changed (ie. current version is
194 * in COW file). Set the number of continuous blocks for which that
196 static int is_changed(uint8_t *bitmap,
197 int64_t sector_num, int nb_sectors,
202 if (!bitmap || nb_sectors == 0) {
203 *num_same = nb_sectors;
207 changed = is_bit_set(bitmap, sector_num);
208 for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
209 if (is_bit_set(bitmap, sector_num + *num_same) != changed)
216 /* commit COW file into the raw image */
217 int bdrv_commit(BlockDriverState *bs)
222 if (!bs->cow_bitmap) {
223 fprintf(stderr, "Already committed to %s\n", bs->filename);
228 fprintf(stderr, "Can't commit to %s: read-only\n", bs->filename);
232 cow_bitmap = bs->cow_bitmap;
233 for (i = 0; i < bs->total_sectors; i++) {
234 if (is_bit_set(cow_bitmap, i)) {
235 unsigned char sector[512];
236 if (bdrv_read(bs, i, sector, 1) != 0) {
237 fprintf(stderr, "Error reading sector %lli: aborting commit\n",
242 /* Make bdrv_write write to real file for a moment. */
243 bs->cow_bitmap = NULL;
244 if (bdrv_write(bs, i, sector, 1) != 0) {
245 fprintf(stderr, "Error writing sector %lli: aborting commit\n",
247 bs->cow_bitmap = cow_bitmap;
250 bs->cow_bitmap = cow_bitmap;
253 fprintf(stderr, "Committed snapshot to %s\n", bs->filename);
257 /* return -1 if error */
258 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
259 uint8_t *buf, int nb_sectors)
264 while (nb_sectors > 0) {
265 if (is_changed(bs->cow_bitmap, sector_num, nb_sectors, &n)) {
267 offset = bs->cow_sectors_offset;
268 } else if (sector_num == 0 && bs->boot_sector_enabled) {
269 memcpy(buf, bs->boot_sector_data, 512);
278 /* no file, just return empty sectors */
279 memset(buf, 0, n * 512);
281 offset += sector_num * 512;
282 lseek64(fd, offset, SEEK_SET);
283 ret = read(fd, buf, n * 512);
284 if (ret != n * 512) {
296 /* return -1 if error */
297 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
298 const uint8_t *buf, int nb_sectors)
301 int64_t offset, retl;
306 if (bs->cow_bitmap) {
308 offset = bs->cow_sectors_offset;
314 offset += sector_num * 512;
315 retl = lseek64(fd, offset, SEEK_SET);
319 ret = write(fd, buf, nb_sectors * 512);
320 if (ret != nb_sectors * 512) {
324 if (bs->cow_bitmap) {
325 for (i = 0; i < nb_sectors; i++)
326 set_bit(bs->cow_bitmap, sector_num + i);
331 void bdrv_get_geometry(BlockDriverState *bs, int64_t *nb_sectors_ptr)
333 *nb_sectors_ptr = bs->total_sectors;
336 /* force a given boot sector. */
337 void bdrv_set_boot_sector(BlockDriverState *bs, const uint8_t *data, int size)
339 bs->boot_sector_enabled = 1;
342 memcpy(bs->boot_sector_data, data, size);
343 memset(bs->boot_sector_data + size, 0, 512 - size);