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git.proxmox.com Git - qemu.git/blob - block.c
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
);