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global s/fflush(logfile)/qemu_log_flush()/ (Eduardo Habkost)
[qemu.git] / block-cow.c
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1/*
2 * Block driver for the COW format
5fafdf24 3 *
ea2384d3 4 * Copyright (c) 2004 Fabrice Bellard
5fafdf24 5 *
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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
faf07963 25#include "qemu-common.h"
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26#include "block_int.h"
27#include <sys/mman.h>
28
29/**************************************************************/
30/* COW block driver using file system holes */
31
32/* user mode linux compatible COW file */
33#define COW_MAGIC 0x4f4f4f4d /* MOOO */
34#define COW_VERSION 2
35
36struct cow_header_v2 {
37 uint32_t magic;
38 uint32_t version;
39 char backing_file[1024];
40 int32_t mtime;
41 uint64_t size;
42 uint32_t sectorsize;
43};
44
45typedef struct BDRVCowState {
46 int fd;
47 uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
48 uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
49 int cow_bitmap_size;
50 int64_t cow_sectors_offset;
51} BDRVCowState;
52
53static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
54{
55 const struct cow_header_v2 *cow_header = (const void *)buf;
56
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57 if (buf_size >= sizeof(struct cow_header_v2) &&
58 be32_to_cpu(cow_header->magic) == COW_MAGIC &&
5fafdf24 59 be32_to_cpu(cow_header->version) == COW_VERSION)
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60 return 100;
61 else
62 return 0;
63}
64
83f64091 65static int cow_open(BlockDriverState *bs, const char *filename, int flags)
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66{
67 BDRVCowState *s = bs->opaque;
68 int fd;
69 struct cow_header_v2 cow_header;
70 int64_t size;
71
72 fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
73 if (fd < 0) {
74 fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
75 if (fd < 0)
76 return -1;
77 }
78 s->fd = fd;
79 /* see if it is a cow image */
80 if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
81 goto fail;
82 }
83
84 if (be32_to_cpu(cow_header.magic) != COW_MAGIC ||
85 be32_to_cpu(cow_header.version) != COW_VERSION) {
86 goto fail;
87 }
3b46e624 88
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89 /* cow image found */
90 size = be64_to_cpu(cow_header.size);
91 bs->total_sectors = size / 512;
92
5fafdf24 93 pstrcpy(bs->backing_file, sizeof(bs->backing_file),
ea2384d3 94 cow_header.backing_file);
3b46e624 95
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96 /* mmap the bitmap */
97 s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
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98 s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
99 s->cow_bitmap_size,
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100 PROT_READ | PROT_WRITE,
101 MAP_SHARED, s->fd, 0);
102 if (s->cow_bitmap_addr == MAP_FAILED)
103 goto fail;
104 s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
105 s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
106 return 0;
107 fail:
108 close(fd);
109 return -1;
110}
111
2b03a7a5 112static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
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113{
114 bitmap[bitnum / 8] |= (1 << (bitnum%8));
115}
116
117static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
118{
119 return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
120}
121
122
123/* Return true if first block has been changed (ie. current version is
124 * in COW file). Set the number of continuous blocks for which that
125 * is true. */
126static inline int is_changed(uint8_t *bitmap,
127 int64_t sector_num, int nb_sectors,
128 int *num_same)
129{
130 int changed;
131
132 if (!bitmap || nb_sectors == 0) {
133 *num_same = nb_sectors;
134 return 0;
135 }
136
137 changed = is_bit_set(bitmap, sector_num);
138 for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
139 if (is_bit_set(bitmap, sector_num + *num_same) != changed)
140 break;
141 }
142
143 return changed;
144}
145
5fafdf24 146static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
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147 int nb_sectors, int *pnum)
148{
149 BDRVCowState *s = bs->opaque;
150 return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
151}
152
5fafdf24 153static int cow_read(BlockDriverState *bs, int64_t sector_num,
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154 uint8_t *buf, int nb_sectors)
155{
156 BDRVCowState *s = bs->opaque;
157 int ret, n;
3b46e624 158
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159 while (nb_sectors > 0) {
160 if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
d5249393 161 lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3 162 ret = read(s->fd, buf, n * 512);
5fafdf24 163 if (ret != n * 512)
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164 return -1;
165 } else {
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166 if (bs->backing_hd) {
167 /* read from the base image */
168 ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
169 if (ret < 0)
170 return -1;
171 } else {
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172 memset(buf, 0, n * 512);
173 }
83f64091 174 }
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175 nb_sectors -= n;
176 sector_num += n;
177 buf += n * 512;
178 }
179 return 0;
180}
181
5fafdf24 182static int cow_write(BlockDriverState *bs, int64_t sector_num,
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183 const uint8_t *buf, int nb_sectors)
184{
185 BDRVCowState *s = bs->opaque;
186 int ret, i;
3b46e624 187
d5249393 188 lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3 189 ret = write(s->fd, buf, nb_sectors * 512);
5fafdf24 190 if (ret != nb_sectors * 512)
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191 return -1;
192 for (i = 0; i < nb_sectors; i++)
2b03a7a5 193 cow_set_bit(s->cow_bitmap, sector_num + i);
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194 return 0;
195}
196
e2731add 197static void cow_close(BlockDriverState *bs)
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198{
199 BDRVCowState *s = bs->opaque;
200 munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
201 close(s->fd);
202}
203
204static int cow_create(const char *filename, int64_t image_sectors,
205 const char *image_filename, int flags)
206{
207 int fd, cow_fd;
208 struct cow_header_v2 cow_header;
209 struct stat st;
210
211 if (flags)
212 return -ENOTSUP;
213
5fafdf24 214 cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
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215 0644);
216 if (cow_fd < 0)
217 return -1;
218 memset(&cow_header, 0, sizeof(cow_header));
219 cow_header.magic = cpu_to_be32(COW_MAGIC);
220 cow_header.version = cpu_to_be32(COW_VERSION);
221 if (image_filename) {
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222 /* Note: if no file, we put a dummy mtime */
223 cow_header.mtime = cpu_to_be32(0);
224
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225 fd = open(image_filename, O_RDONLY | O_BINARY);
226 if (fd < 0) {
227 close(cow_fd);
83f64091 228 goto mtime_fail;
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229 }
230 if (fstat(fd, &st) != 0) {
231 close(fd);
83f64091 232 goto mtime_fail;
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233 }
234 close(fd);
235 cow_header.mtime = cpu_to_be32(st.st_mtime);
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236 mtime_fail:
237 pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
238 image_filename);
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239 }
240 cow_header.sectorsize = cpu_to_be32(512);
241 cow_header.size = cpu_to_be64(image_sectors * 512);
242 write(cow_fd, &cow_header, sizeof(cow_header));
243 /* resize to include at least all the bitmap */
244 ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
245 close(cow_fd);
246 return 0;
247}
248
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249static void cow_flush(BlockDriverState *bs)
250{
251 BDRVCowState *s = bs->opaque;
252 fsync(s->fd);
253}
254
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255BlockDriver bdrv_cow = {
256 "cow",
257 sizeof(BDRVCowState),
258 cow_probe,
259 cow_open,
260 cow_read,
261 cow_write,
262 cow_close,
263 cow_create,
7a6cba61 264 cow_flush,
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265 cow_is_allocated,
266};
267#endif