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1.1 root 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: #ifndef _WIN32
25: #include "qemu-common.h"
26: #include "block_int.h"
27: #include "module.h"
28: #include <sys/mman.h>
29:
30: /**************************************************************/
31: /* COW block driver using file system holes */
32:
33: /* user mode linux compatible COW file */
34: #define COW_MAGIC 0x4f4f4f4d /* MOOO */
35: #define COW_VERSION 2
36:
37: struct cow_header_v2 {
38: uint32_t magic;
39: uint32_t version;
40: char backing_file[1024];
41: int32_t mtime;
42: uint64_t size;
43: uint32_t sectorsize;
44: };
45:
46: typedef struct BDRVCowState {
47: int fd;
48: uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
49: uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
50: int cow_bitmap_size;
51: int64_t cow_sectors_offset;
52: } BDRVCowState;
53:
54: static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
55: {
56: const struct cow_header_v2 *cow_header = (const void *)buf;
57:
58: if (buf_size >= sizeof(struct cow_header_v2) &&
59: be32_to_cpu(cow_header->magic) == COW_MAGIC &&
60: be32_to_cpu(cow_header->version) == COW_VERSION)
61: return 100;
62: else
63: return 0;
64: }
65:
66: static int cow_open(BlockDriverState *bs, const char *filename, int flags)
67: {
68: BDRVCowState *s = bs->opaque;
69: int fd;
70: struct cow_header_v2 cow_header;
71: int64_t size;
72:
73: fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
74: if (fd < 0) {
75: fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
76: if (fd < 0)
77: return -1;
78: }
79: s->fd = fd;
80: /* see if it is a cow image */
81: if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
82: goto fail;
83: }
84:
85: if (be32_to_cpu(cow_header.magic) != COW_MAGIC ||
86: be32_to_cpu(cow_header.version) != COW_VERSION) {
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: /* mmap the bitmap */
98: s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
99: s->cow_bitmap_addr = (void *)mmap(get_mmap_addr(s->cow_bitmap_size),
100: s->cow_bitmap_size,
101: PROT_READ | PROT_WRITE,
102: MAP_SHARED, s->fd, 0);
103: if (s->cow_bitmap_addr == MAP_FAILED)
104: goto fail;
105: s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
106: s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
107: return 0;
108: fail:
109: close(fd);
110: return -1;
111: }
112:
113: static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
114: {
115: bitmap[bitnum / 8] |= (1 << (bitnum%8));
116: }
117:
118: static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
119: {
120: return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
121: }
122:
123:
124: /* Return true if first block has been changed (ie. current version is
125: * in COW file). Set the number of continuous blocks for which that
126: * is true. */
127: static inline int is_changed(uint8_t *bitmap,
128: int64_t sector_num, int nb_sectors,
129: int *num_same)
130: {
131: int changed;
132:
133: if (!bitmap || nb_sectors == 0) {
134: *num_same = nb_sectors;
135: return 0;
136: }
137:
138: changed = is_bit_set(bitmap, sector_num);
139: for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
140: if (is_bit_set(bitmap, sector_num + *num_same) != changed)
141: break;
142: }
143:
144: return changed;
145: }
146:
147: static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
148: int nb_sectors, int *pnum)
149: {
150: BDRVCowState *s = bs->opaque;
151: return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
152: }
153:
154: static int cow_read(BlockDriverState *bs, int64_t sector_num,
155: uint8_t *buf, int nb_sectors)
156: {
157: BDRVCowState *s = bs->opaque;
158: int ret, n;
159:
160: while (nb_sectors > 0) {
161: if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
162: lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
163: ret = read(s->fd, buf, n * 512);
164: if (ret != n * 512)
165: return -1;
166: } else {
167: if (bs->backing_hd) {
168: /* read from the base image */
169: ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
170: if (ret < 0)
171: return -1;
172: } else {
173: memset(buf, 0, n * 512);
174: }
175: }
176: nb_sectors -= n;
177: sector_num += n;
178: buf += n * 512;
179: }
180: return 0;
181: }
182:
183: static int cow_write(BlockDriverState *bs, int64_t sector_num,
184: const uint8_t *buf, int nb_sectors)
185: {
186: BDRVCowState *s = bs->opaque;
187: int ret, i;
188:
189: lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
190: ret = write(s->fd, buf, nb_sectors * 512);
191: if (ret != nb_sectors * 512)
192: return -1;
193: for (i = 0; i < nb_sectors; i++)
194: cow_set_bit(s->cow_bitmap, sector_num + i);
195: return 0;
196: }
197:
198: static void cow_close(BlockDriverState *bs)
199: {
200: BDRVCowState *s = bs->opaque;
201: munmap((void *)s->cow_bitmap_addr, s->cow_bitmap_size);
202: close(s->fd);
203: }
204:
205: static int cow_create(const char *filename, QEMUOptionParameter *options)
206: {
207: int fd, cow_fd;
208: struct cow_header_v2 cow_header;
209: struct stat st;
210: int64_t image_sectors = 0;
211: const char *image_filename = NULL;
212:
213: /* Read out options */
214: while (options && options->name) {
215: if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
216: image_sectors = options->value.n / 512;
217: } else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
218: image_filename = options->value.s;
219: }
220: options++;
221: }
222:
223: cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
224: 0644);
225: if (cow_fd < 0)
226: return -1;
227: memset(&cow_header, 0, sizeof(cow_header));
228: cow_header.magic = cpu_to_be32(COW_MAGIC);
229: cow_header.version = cpu_to_be32(COW_VERSION);
230: if (image_filename) {
231: /* Note: if no file, we put a dummy mtime */
232: cow_header.mtime = cpu_to_be32(0);
233:
234: fd = open(image_filename, O_RDONLY | O_BINARY);
235: if (fd < 0) {
236: close(cow_fd);
237: goto mtime_fail;
238: }
239: if (fstat(fd, &st) != 0) {
240: close(fd);
241: goto mtime_fail;
242: }
243: close(fd);
244: cow_header.mtime = cpu_to_be32(st.st_mtime);
245: mtime_fail:
246: pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
247: image_filename);
248: }
249: cow_header.sectorsize = cpu_to_be32(512);
250: cow_header.size = cpu_to_be64(image_sectors * 512);
251: write(cow_fd, &cow_header, sizeof(cow_header));
252: /* resize to include at least all the bitmap */
253: ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
254: close(cow_fd);
255: return 0;
256: }
257:
258: static void cow_flush(BlockDriverState *bs)
259: {
260: BDRVCowState *s = bs->opaque;
1.1.1.2 ! root 261: qemu_fdatasync(s->fd);
1.1 root 262: }
263:
264: static QEMUOptionParameter cow_create_options[] = {
265: {
266: .name = BLOCK_OPT_SIZE,
267: .type = OPT_SIZE,
268: .help = "Virtual disk size"
269: },
270: {
271: .name = BLOCK_OPT_BACKING_FILE,
272: .type = OPT_STRING,
273: .help = "File name of a base image"
274: },
275: { NULL }
276: };
277:
278: static BlockDriver bdrv_cow = {
279: .format_name = "cow",
280: .instance_size = sizeof(BDRVCowState),
281: .bdrv_probe = cow_probe,
282: .bdrv_open = cow_open,
283: .bdrv_read = cow_read,
284: .bdrv_write = cow_write,
285: .bdrv_close = cow_close,
286: .bdrv_create = cow_create,
287: .bdrv_flush = cow_flush,
288: .bdrv_is_allocated = cow_is_allocated,
289:
290: .create_options = cow_create_options,
291: };
292:
293: static void bdrv_cow_init(void)
294: {
295: bdrv_register(&bdrv_cow);
296: }
297:
298: block_init(bdrv_cow_init);
299: #endif
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