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
50 struct BlockDriverState {
51 int fd; /* if -1, only COW mappings */
52 int64_t total_sectors;
55 uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
56 uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
59 int64_t cow_sectors_offset;
60 int boot_sector_enabled;
61 uint8_t boot_sector_data[512];
66 BlockDriverState *bdrv_open(const char *filename, int snapshot)
71 char template[] = "/tmp/vl.XXXXXX";
72 struct cow_header_v2 cow_header;
75 bs = malloc(sizeof(BlockDriverState));
81 bs->cow_bitmap = NULL;
82 strcpy(bs->filename, filename);
84 /* open standard HD image */
85 fd = open(filename, O_RDWR | O_LARGEFILE);
87 /* read only image on disk */
88 fd = open(filename, O_RDONLY | O_LARGEFILE);
98 /* see if it is a cow image */
99 if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
100 fprintf(stderr, "%s: could not read header\n", filename);
103 if (cow_header.magic == htonl(COW_MAGIC) &&
104 cow_header.version == htonl(COW_VERSION)) {
105 /* cow image found */
106 size = cow_header.size;
107 #ifndef WORDS_BIGENDIAN
108 size = bswap64(size);
110 bs->total_sectors = size / 512;
114 if (cow_header.backing_file[0] != '\0') {
115 if (stat(cow_header.backing_file, &st) != 0) {
116 fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
119 if (st.st_mtime != htonl(cow_header.mtime)) {
120 fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
123 fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
128 /* mmap the bitmap */
129 bs->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
130 bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
132 PROT_READ | PROT_WRITE,
133 MAP_SHARED, bs->cow_fd, 0);
134 if (bs->cow_bitmap_addr == MAP_FAILED)
136 bs->cow_bitmap = bs->cow_bitmap_addr + sizeof(cow_header);
137 bs->cow_sectors_offset = (bs->cow_bitmap_size + 511) & ~511;
140 /* standard raw image */
141 size = lseek64(fd, 0, SEEK_END);
142 bs->total_sectors = size / 512;
147 /* create a temporary COW file */
148 cow_fd = mkstemp(template);
154 /* just need to allocate bitmap */
155 bs->cow_bitmap_size = (bs->total_sectors + 7) >> 3;
156 bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size),
158 PROT_READ | PROT_WRITE,
159 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
160 if (bs->cow_bitmap_addr == MAP_FAILED)
162 bs->cow_bitmap = bs->cow_bitmap_addr;
163 bs->cow_sectors_offset = 0;
172 void bdrv_close(BlockDriverState *bs)
174 /* we unmap the mapping so that it is written to the COW file */
175 if (bs->cow_bitmap_addr)
176 munmap(bs->cow_bitmap_addr, bs->cow_bitmap_size);
184 static inline void set_bit(uint8_t *bitmap, int64_t bitnum)
186 bitmap[bitnum / 8] |= (1 << (bitnum%8));
189 static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
191 return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
195 /* Return true if first block has been changed (ie. current version is
196 * in COW file). Set the number of continuous blocks for which that
198 static int is_changed(uint8_t *bitmap,
199 int64_t sector_num, int nb_sectors,
204 if (!bitmap || nb_sectors == 0) {
205 *num_same = nb_sectors;
209 changed = is_bit_set(bitmap, sector_num);
210 for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
211 if (is_bit_set(bitmap, sector_num + *num_same) != changed)
218 /* commit COW file into the raw image */
219 int bdrv_commit(BlockDriverState *bs)
224 if (!bs->cow_bitmap) {
225 fprintf(stderr, "Already committed to %s\n", bs->filename);
230 fprintf(stderr, "Can't commit to %s: read-only\n", bs->filename);
234 cow_bitmap = bs->cow_bitmap;
235 for (i = 0; i < bs->total_sectors; i++) {
236 if (is_bit_set(cow_bitmap, i)) {
237 unsigned char sector[512];
238 if (bdrv_read(bs, i, sector, 1) != 0) {
239 fprintf(stderr, "Error reading sector %lli: aborting commit\n",
244 /* Make bdrv_write write to real file for a moment. */
245 bs->cow_bitmap = NULL;
246 if (bdrv_write(bs, i, sector, 1) != 0) {
247 fprintf(stderr, "Error writing sector %lli: aborting commit\n",
249 bs->cow_bitmap = cow_bitmap;
252 bs->cow_bitmap = cow_bitmap;
255 fprintf(stderr, "Committed snapshot to %s\n", bs->filename);
259 /* return -1 if error */
260 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
261 uint8_t *buf, int nb_sectors)
266 while (nb_sectors > 0) {
267 if (is_changed(bs->cow_bitmap, sector_num, nb_sectors, &n)) {
269 offset = bs->cow_sectors_offset;
270 } else if (sector_num == 0 && bs->boot_sector_enabled) {
271 memcpy(buf, bs->boot_sector_data, 512);
280 /* no file, just return empty sectors */
281 memset(buf, 0, n * 512);
283 offset += sector_num * 512;
284 lseek64(fd, offset, SEEK_SET);
285 ret = read(fd, buf, n * 512);
286 if (ret != n * 512) {
298 /* return -1 if error */
299 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
300 const uint8_t *buf, int nb_sectors)
303 int64_t offset, retl;
308 if (bs->cow_bitmap) {
310 offset = bs->cow_sectors_offset;
316 offset += sector_num * 512;
317 retl = lseek64(fd, offset, SEEK_SET);
321 ret = write(fd, buf, nb_sectors * 512);
322 if (ret != nb_sectors * 512) {
326 if (bs->cow_bitmap) {
327 for (i = 0; i < nb_sectors; i++)
328 set_bit(bs->cow_bitmap, sector_num + i);
333 void bdrv_get_geometry(BlockDriverState *bs, int64_t *nb_sectors_ptr)
335 *nb_sectors_ptr = bs->total_sectors;
338 /* force a given boot sector. */
339 void bdrv_set_boot_sector(BlockDriverState *bs, const uint8_t *data, int size)
341 bs->boot_sector_enabled = 1;
344 memcpy(bs->boot_sector_data, data, size);
345 memset(bs->boot_sector_data + size, 0, 512 - size);