usb-bsd: convert to QOM
[qemu.git] / block / cow.c
1 /*
2 * Block driver for the COW format
3 *
4 * Copyright (c) 2004 Fabrice Bellard
5 *
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 */
24 #include "qemu-common.h"
25 #include "block_int.h"
26 #include "module.h"
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
35 struct 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
44 typedef struct BDRVCowState {
45 CoMutex lock;
46 int64_t cow_sectors_offset;
47 } BDRVCowState;
48
49 static 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
53 if (buf_size >= sizeof(struct cow_header_v2) &&
54 be32_to_cpu(cow_header->magic) == COW_MAGIC &&
55 be32_to_cpu(cow_header->version) == COW_VERSION)
56 return 100;
57 else
58 return 0;
59 }
60
61 static int cow_open(BlockDriverState *bs, int flags)
62 {
63 BDRVCowState *s = bs->opaque;
64 struct cow_header_v2 cow_header;
65 int bitmap_size;
66 int64_t size;
67 int ret;
68
69 /* see if it is a cow image */
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) {
76 ret = -EINVAL;
77 goto fail;
78 }
79
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;
87 goto fail;
88 }
89
90 /* cow image found */
91 size = be64_to_cpu(cow_header.size);
92 bs->total_sectors = size / 512;
93
94 pstrcpy(bs->backing_file, sizeof(bs->backing_file),
95 cow_header.backing_file);
96
97 bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
98 s->cow_sectors_offset = (bitmap_size + 511) & ~511;
99 qemu_co_mutex_init(&s->lock);
100 return 0;
101 fail:
102 return ret;
103 }
104
105 /*
106 * XXX(hch): right now these functions are extremely ineffcient.
107 * We should just read the whole bitmap we'll need in one go instead.
108 */
109 static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
110 {
111 uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
112 uint8_t bitmap;
113 int ret;
114
115 ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
116 if (ret < 0) {
117 return ret;
118 }
119
120 bitmap |= (1 << (bitnum % 8));
121
122 ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap));
123 if (ret < 0) {
124 return ret;
125 }
126 return 0;
127 }
128
129 static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)
130 {
131 uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
132 uint8_t bitmap;
133 int ret;
134
135 ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
136 if (ret < 0) {
137 return ret;
138 }
139
140 return !!(bitmap & (1 << (bitnum % 8)));
141 }
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. */
146 static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs,
147 int64_t sector_num, int nb_sectors, int *num_same)
148 {
149 int changed;
150
151 if (nb_sectors == 0) {
152 *num_same = nb_sectors;
153 return 0;
154 }
155
156 changed = is_bit_set(bs, sector_num);
157 if (changed < 0) {
158 return 0; /* XXX: how to return I/O errors? */
159 }
160
161 for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
162 if (is_bit_set(bs, sector_num + *num_same) != changed)
163 break;
164 }
165
166 return changed;
167 }
168
169 static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
170 int nb_sectors)
171 {
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;
183 }
184
185 static int coroutine_fn cow_read(BlockDriverState *bs, int64_t sector_num,
186 uint8_t *buf, int nb_sectors)
187 {
188 BDRVCowState *s = bs->opaque;
189 int ret, n;
190
191 while (nb_sectors > 0) {
192 if (bdrv_co_is_allocated(bs, sector_num, nb_sectors, &n)) {
193 ret = bdrv_pread(bs->file,
194 s->cow_sectors_offset + sector_num * 512,
195 buf, n * 512);
196 if (ret < 0) {
197 return ret;
198 }
199 } else {
200 if (bs->backing_hd) {
201 /* read from the base image */
202 ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
203 if (ret < 0) {
204 return ret;
205 }
206 } else {
207 memset(buf, 0, n * 512);
208 }
209 }
210 nb_sectors -= n;
211 sector_num += n;
212 buf += n * 512;
213 }
214 return 0;
215 }
216
217 static 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
228 static int cow_write(BlockDriverState *bs, int64_t sector_num,
229 const uint8_t *buf, int nb_sectors)
230 {
231 BDRVCowState *s = bs->opaque;
232 int ret;
233
234 ret = bdrv_pwrite(bs->file, s->cow_sectors_offset + sector_num * 512,
235 buf, nb_sectors * 512);
236 if (ret < 0) {
237 return ret;
238 }
239
240 return cow_update_bitmap(bs, sector_num, nb_sectors);
241 }
242
243 static 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
254 static void cow_close(BlockDriverState *bs)
255 {
256 }
257
258 static int cow_create(const char *filename, QEMUOptionParameter *options)
259 {
260 struct cow_header_v2 cow_header;
261 struct stat st;
262 int64_t image_sectors = 0;
263 const char *image_filename = NULL;
264 int ret;
265 BlockDriverState *cow_bs;
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 }
276
277 ret = bdrv_create_file(filename, options);
278 if (ret < 0) {
279 return ret;
280 }
281
282 ret = bdrv_file_open(&cow_bs, filename, BDRV_O_RDWR);
283 if (ret < 0) {
284 return ret;
285 }
286
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) {
291 /* Note: if no file, we put a dummy mtime */
292 cow_header.mtime = cpu_to_be32(0);
293
294 if (stat(image_filename, &st) != 0) {
295 goto mtime_fail;
296 }
297 cow_header.mtime = cpu_to_be32(st.st_mtime);
298 mtime_fail:
299 pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
300 image_filename);
301 }
302 cow_header.sectorsize = cpu_to_be32(512);
303 cow_header.size = cpu_to_be64(image_sectors * 512);
304 ret = bdrv_pwrite(cow_bs, 0, &cow_header, sizeof(cow_header));
305 if (ret < 0) {
306 goto exit;
307 }
308
309 /* resize to include at least all the bitmap */
310 ret = bdrv_truncate(cow_bs,
311 sizeof(cow_header) + ((image_sectors + 7) >> 3));
312 if (ret < 0) {
313 goto exit;
314 }
315
316 exit:
317 bdrv_delete(cow_bs);
318 return ret;
319 }
320
321 static coroutine_fn int cow_co_flush(BlockDriverState *bs)
322 {
323 return bdrv_co_flush(bs->file);
324 }
325
326 static QEMUOptionParameter cow_create_options[] = {
327 {
328 .name = BLOCK_OPT_SIZE,
329 .type = OPT_SIZE,
330 .help = "Virtual disk size"
331 },
332 {
333 .name = BLOCK_OPT_BACKING_FILE,
334 .type = OPT_STRING,
335 .help = "File name of a base image"
336 },
337 { NULL }
338 };
339
340 static BlockDriver bdrv_cow = {
341 .format_name = "cow",
342 .instance_size = sizeof(BDRVCowState),
343
344 .bdrv_probe = cow_probe,
345 .bdrv_open = cow_open,
346 .bdrv_close = cow_close,
347 .bdrv_create = cow_create,
348
349 .bdrv_read = cow_co_read,
350 .bdrv_write = cow_co_write,
351 .bdrv_co_flush_to_disk = cow_co_flush,
352 .bdrv_co_is_allocated = cow_co_is_allocated,
353
354 .create_options = cow_create_options,
355 };
356
357 static void bdrv_cow_init(void)
358 {
359 bdrv_register(&bdrv_cow);
360 }
361
362 block_init(bdrv_cow_init);