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ea2384d3
FB
1/*
2 * Block driver for the COW format
5fafdf24 3 *
ea2384d3 4 * Copyright (c) 2004 Fabrice Bellard
5fafdf24 5 *
ea2384d3
FB
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:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
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
22 * THE SOFTWARE.
23 */
faf07963 24#include "qemu-common.h"
737e150e 25#include "block/block_int.h"
1de7afc9 26#include "qemu/module.h"
ea2384d3
FB
27
28/**************************************************************/
29/* COW block driver using file system holes */
30
31/* user mode linux compatible COW file */
32#define COW_MAGIC 0x4f4f4f4d /* MOOO */
33#define COW_VERSION 2
34
35struct cow_header_v2 {
36 uint32_t magic;
37 uint32_t version;
38 char backing_file[1024];
39 int32_t mtime;
40 uint64_t size;
41 uint32_t sectorsize;
42};
43
44typedef struct BDRVCowState {
848c66e8 45 CoMutex lock;
ea2384d3
FB
46 int64_t cow_sectors_offset;
47} BDRVCowState;
48
49static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
50{
51 const struct cow_header_v2 *cow_header = (const void *)buf;
52
712e7874
FB
53 if (buf_size >= sizeof(struct cow_header_v2) &&
54 be32_to_cpu(cow_header->magic) == COW_MAGIC &&
5fafdf24 55 be32_to_cpu(cow_header->version) == COW_VERSION)
ea2384d3
FB
56 return 100;
57 else
58 return 0;
59}
60
1a86938f 61static int cow_open(BlockDriverState *bs, QDict *options, int flags)
ea2384d3
FB
62{
63 BDRVCowState *s = bs->opaque;
ea2384d3 64 struct cow_header_v2 cow_header;
893a9cb4 65 int bitmap_size;
ea2384d3 66 int64_t size;
16d2fc00 67 int ret;
ea2384d3 68
ea2384d3 69 /* see if it is a cow image */
16d2fc00
LZH
70 ret = bdrv_pread(bs->file, 0, &cow_header, sizeof(cow_header));
71 if (ret < 0) {
72 goto fail;
73 }
74
75 if (be32_to_cpu(cow_header.magic) != COW_MAGIC) {
15bac0d5 76 ret = -EMEDIUMTYPE;
ea2384d3
FB
77 goto fail;
78 }
79
16d2fc00
LZH
80 if (be32_to_cpu(cow_header.version) != COW_VERSION) {
81 char version[64];
82 snprintf(version, sizeof(version),
83 "COW version %d", cow_header.version);
84 qerror_report(QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
85 bs->device_name, "cow", version);
86 ret = -ENOTSUP;
ea2384d3
FB
87 goto fail;
88 }
3b46e624 89
ea2384d3
FB
90 /* cow image found */
91 size = be64_to_cpu(cow_header.size);
92 bs->total_sectors = size / 512;
93
5fafdf24 94 pstrcpy(bs->backing_file, sizeof(bs->backing_file),
ea2384d3 95 cow_header.backing_file);
3b46e624 96
893a9cb4
CH
97 bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
98 s->cow_sectors_offset = (bitmap_size + 511) & ~511;
848c66e8 99 qemu_co_mutex_init(&s->lock);
ea2384d3
FB
100 return 0;
101 fail:
16d2fc00 102 return ret;
ea2384d3
FB
103}
104
893a9cb4 105/*
4e35b92a 106 * XXX(hch): right now these functions are extremely inefficient.
893a9cb4
CH
107 * We should just read the whole bitmap we'll need in one go instead.
108 */
109static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
ea2384d3 110{
893a9cb4
CH
111 uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
112 uint8_t bitmap;
b0ad5a45 113 int ret;
893a9cb4 114
b0ad5a45
KW
115 ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
116 if (ret < 0) {
117 return ret;
893a9cb4
CH
118 }
119
120 bitmap |= (1 << (bitnum % 8));
121
b0ad5a45
KW
122 ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap));
123 if (ret < 0) {
124 return ret;
893a9cb4
CH
125 }
126 return 0;
ea2384d3
FB
127}
128
893a9cb4 129static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)
ea2384d3 130{
893a9cb4
CH
131 uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
132 uint8_t bitmap;
b0ad5a45 133 int ret;
ea2384d3 134
b0ad5a45
KW
135 ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
136 if (ret < 0) {
137 return ret;
893a9cb4
CH
138 }
139
140 return !!(bitmap & (1 << (bitnum % 8)));
141}
ea2384d3
FB
142
143/* Return true if first block has been changed (ie. current version is
144 * in COW file). Set the number of continuous blocks for which that
145 * is true. */
81145834
SH
146static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs,
147 int64_t sector_num, int nb_sectors, int *num_same)
ea2384d3
FB
148{
149 int changed;
150
893a9cb4 151 if (nb_sectors == 0) {
ea2384d3
FB
152 *num_same = nb_sectors;
153 return 0;
154 }
155
893a9cb4
CH
156 changed = is_bit_set(bs, sector_num);
157 if (changed < 0) {
158 return 0; /* XXX: how to return I/O errors? */
159 }
160
ea2384d3 161 for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
893a9cb4 162 if (is_bit_set(bs, sector_num + *num_same) != changed)
ea2384d3
FB
163 break;
164 }
165
166 return changed;
167}
168
893a9cb4
CH
169static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
170 int nb_sectors)
ea2384d3 171{
893a9cb4
CH
172 int error = 0;
173 int i;
174
175 for (i = 0; i < nb_sectors; i++) {
176 error = cow_set_bit(bs, sector_num + i);
177 if (error) {
178 break;
179 }
180 }
181
182 return error;
ea2384d3
FB
183}
184
e94d1387
SH
185static int coroutine_fn cow_read(BlockDriverState *bs, int64_t sector_num,
186 uint8_t *buf, int nb_sectors)
ea2384d3
FB
187{
188 BDRVCowState *s = bs->opaque;
189 int ret, n;
3b46e624 190
ea2384d3 191 while (nb_sectors > 0) {
e94d1387 192 if (bdrv_co_is_allocated(bs, sector_num, nb_sectors, &n)) {
2063392a
CH
193 ret = bdrv_pread(bs->file,
194 s->cow_sectors_offset + sector_num * 512,
195 buf, n * 512);
16d2fc00
LZH
196 if (ret < 0) {
197 return ret;
198 }
ea2384d3 199 } else {
83f64091
FB
200 if (bs->backing_hd) {
201 /* read from the base image */
202 ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
16d2fc00
LZH
203 if (ret < 0) {
204 return ret;
205 }
83f64091 206 } else {
16d2fc00
LZH
207 memset(buf, 0, n * 512);
208 }
83f64091 209 }
ea2384d3
FB
210 nb_sectors -= n;
211 sector_num += n;
212 buf += n * 512;
213 }
214 return 0;
215}
216
2914caa0
PB
217static coroutine_fn int cow_co_read(BlockDriverState *bs, int64_t sector_num,
218 uint8_t *buf, int nb_sectors)
219{
220 int ret;
221 BDRVCowState *s = bs->opaque;
222 qemu_co_mutex_lock(&s->lock);
223 ret = cow_read(bs, sector_num, buf, nb_sectors);
224 qemu_co_mutex_unlock(&s->lock);
225 return ret;
226}
227
5fafdf24 228static int cow_write(BlockDriverState *bs, int64_t sector_num,
ea2384d3
FB
229 const uint8_t *buf, int nb_sectors)
230{
231 BDRVCowState *s = bs->opaque;
893a9cb4 232 int ret;
3b46e624 233
2063392a
CH
234 ret = bdrv_pwrite(bs->file, s->cow_sectors_offset + sector_num * 512,
235 buf, nb_sectors * 512);
16d2fc00
LZH
236 if (ret < 0) {
237 return ret;
238 }
893a9cb4
CH
239
240 return cow_update_bitmap(bs, sector_num, nb_sectors);
ea2384d3
FB
241}
242
e183ef75
PB
243static coroutine_fn int cow_co_write(BlockDriverState *bs, int64_t sector_num,
244 const uint8_t *buf, int nb_sectors)
245{
246 int ret;
247 BDRVCowState *s = bs->opaque;
248 qemu_co_mutex_lock(&s->lock);
249 ret = cow_write(bs, sector_num, buf, nb_sectors);
250 qemu_co_mutex_unlock(&s->lock);
251 return ret;
252}
253
e2731add 254static void cow_close(BlockDriverState *bs)
ea2384d3 255{
ea2384d3
FB
256}
257
0e7e1989 258static int cow_create(const char *filename, QEMUOptionParameter *options)
ea2384d3 259{
ea2384d3
FB
260 struct cow_header_v2 cow_header;
261 struct stat st;
0e7e1989
KW
262 int64_t image_sectors = 0;
263 const char *image_filename = NULL;
31f38120 264 int ret;
3535a9c6 265 BlockDriverState *cow_bs;
0e7e1989
KW
266
267 /* Read out options */
268 while (options && options->name) {
269 if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
270 image_sectors = options->value.n / 512;
271 } else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
272 image_filename = options->value.s;
273 }
274 options++;
275 }
ea2384d3 276
3535a9c6
LZH
277 ret = bdrv_create_file(filename, options);
278 if (ret < 0) {
279 return ret;
280 }
281
787e4a85 282 ret = bdrv_file_open(&cow_bs, filename, NULL, BDRV_O_RDWR);
3535a9c6
LZH
283 if (ret < 0) {
284 return ret;
285 }
286
ea2384d3
FB
287 memset(&cow_header, 0, sizeof(cow_header));
288 cow_header.magic = cpu_to_be32(COW_MAGIC);
289 cow_header.version = cpu_to_be32(COW_VERSION);
290 if (image_filename) {
83f64091
FB
291 /* Note: if no file, we put a dummy mtime */
292 cow_header.mtime = cpu_to_be32(0);
293
3535a9c6 294 if (stat(image_filename, &st) != 0) {
83f64091 295 goto mtime_fail;
ea2384d3 296 }
ea2384d3 297 cow_header.mtime = cpu_to_be32(st.st_mtime);
83f64091
FB
298 mtime_fail:
299 pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
300 image_filename);
ea2384d3
FB
301 }
302 cow_header.sectorsize = cpu_to_be32(512);
303 cow_header.size = cpu_to_be64(image_sectors * 512);
3535a9c6 304 ret = bdrv_pwrite(cow_bs, 0, &cow_header, sizeof(cow_header));
16d2fc00 305 if (ret < 0) {
31f38120
KS
306 goto exit;
307 }
308
ea2384d3 309 /* resize to include at least all the bitmap */
3535a9c6
LZH
310 ret = bdrv_truncate(cow_bs,
311 sizeof(cow_header) + ((image_sectors + 7) >> 3));
16d2fc00 312 if (ret < 0) {
31f38120
KS
313 goto exit;
314 }
315
31f38120 316exit:
3535a9c6 317 bdrv_delete(cow_bs);
31f38120 318 return ret;
ea2384d3
FB
319}
320
0e7e1989 321static QEMUOptionParameter cow_create_options[] = {
db08adf5
KW
322 {
323 .name = BLOCK_OPT_SIZE,
324 .type = OPT_SIZE,
325 .help = "Virtual disk size"
326 },
327 {
328 .name = BLOCK_OPT_BACKING_FILE,
329 .type = OPT_STRING,
330 .help = "File name of a base image"
331 },
0e7e1989
KW
332 { NULL }
333};
334
5efa9d5a 335static BlockDriver bdrv_cow = {
c68b89ac
KW
336 .format_name = "cow",
337 .instance_size = sizeof(BDRVCowState),
338
339 .bdrv_probe = cow_probe,
340 .bdrv_open = cow_open,
341 .bdrv_close = cow_close,
342 .bdrv_create = cow_create,
343
344 .bdrv_read = cow_co_read,
345 .bdrv_write = cow_co_write,
81145834 346 .bdrv_co_is_allocated = cow_co_is_allocated,
0e7e1989
KW
347
348 .create_options = cow_create_options,
ea2384d3 349};
5efa9d5a
AL
350
351static void bdrv_cow_init(void)
352{
353 bdrv_register(&bdrv_cow);
354}
355
356block_init(bdrv_cow_init);