ia64/xen-unstable

view tools/ioemu/block-cow.c @ 6946:e703abaf6e3d

Add behaviour to the remove methods to remove the transaction's path itself. This allows us to write Remove(path) to remove the specified path rather than having to slice the path ourselves.
author emellor@ewan
date Sun Sep 18 14:42:13 2005 +0100 (2005-09-18)
parents 8e5fc5fe636c
children f7b43e5c42b9
line source
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 "vl.h"
26 #include "block_int.h"
27 #include <sys/mman.h>
29 /**************************************************************/
30 /* COW block driver using file system holes */
32 /* user mode linux compatible COW file */
33 #define COW_MAGIC 0x4f4f4f4d /* MOOO */
34 #define COW_VERSION 2
36 struct 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 };
45 typedef 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;
53 static 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;
57 if (be32_to_cpu(cow_header->magic) == COW_MAGIC &&
58 be32_to_cpu(cow_header->version) == COW_VERSION)
59 return 100;
60 else
61 return 0;
62 }
64 static int cow_open(BlockDriverState *bs, const char *filename)
65 {
66 BDRVCowState *s = bs->opaque;
67 int fd;
68 struct cow_header_v2 cow_header;
69 int64_t size;
71 fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
72 if (fd < 0) {
73 fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
74 if (fd < 0)
75 return -1;
76 }
77 s->fd = fd;
78 /* see if it is a cow image */
79 if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
80 goto fail;
81 }
83 if (be32_to_cpu(cow_header.magic) != COW_MAGIC ||
84 be32_to_cpu(cow_header.version) != COW_VERSION) {
85 goto fail;
86 }
88 /* cow image found */
89 size = be64_to_cpu(cow_header.size);
90 bs->total_sectors = size / 512;
92 pstrcpy(bs->backing_file, sizeof(bs->backing_file),
93 cow_header.backing_file);
95 #if 0
96 if (cow_header.backing_file[0] != '\0') {
97 if (stat(cow_header.backing_file, &st) != 0) {
98 fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
99 goto fail;
100 }
101 if (st.st_mtime != be32_to_cpu(cow_header.mtime)) {
102 fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
103 goto fail;
104 }
105 fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
106 if (fd < 0)
107 goto fail;
108 bs->fd = fd;
109 }
110 #endif
111 /* mmap the bitmap */
112 s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
113 s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
114 s->cow_bitmap_size,
115 PROT_READ | PROT_WRITE,
116 MAP_SHARED, s->fd, 0);
117 if (s->cow_bitmap_addr == MAP_FAILED)
118 goto fail;
119 s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
120 s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
121 return 0;
122 fail:
123 close(fd);
124 return -1;
125 }
127 static inline void set_bit(uint8_t *bitmap, int64_t bitnum)
128 {
129 bitmap[bitnum / 8] |= (1 << (bitnum%8));
130 }
132 static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
133 {
134 return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
135 }
138 /* Return true if first block has been changed (ie. current version is
139 * in COW file). Set the number of continuous blocks for which that
140 * is true. */
141 static inline int is_changed(uint8_t *bitmap,
142 int64_t sector_num, int nb_sectors,
143 int *num_same)
144 {
145 int changed;
147 if (!bitmap || nb_sectors == 0) {
148 *num_same = nb_sectors;
149 return 0;
150 }
152 changed = is_bit_set(bitmap, sector_num);
153 for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
154 if (is_bit_set(bitmap, sector_num + *num_same) != changed)
155 break;
156 }
158 return changed;
159 }
161 static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
162 int nb_sectors, int *pnum)
163 {
164 BDRVCowState *s = bs->opaque;
165 return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
166 }
168 static int cow_read(BlockDriverState *bs, int64_t sector_num,
169 uint8_t *buf, int nb_sectors)
170 {
171 BDRVCowState *s = bs->opaque;
172 int ret, n;
174 while (nb_sectors > 0) {
175 if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
176 lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
177 ret = read(s->fd, buf, n * 512);
178 if (ret != n * 512)
179 return -1;
180 } else {
181 memset(buf, 0, n * 512);
182 }
183 nb_sectors -= n;
184 sector_num += n;
185 buf += n * 512;
186 }
187 return 0;
188 }
190 static int cow_write(BlockDriverState *bs, int64_t sector_num,
191 const uint8_t *buf, int nb_sectors)
192 {
193 BDRVCowState *s = bs->opaque;
194 int ret, i;
196 lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
197 ret = write(s->fd, buf, nb_sectors * 512);
198 if (ret != nb_sectors * 512)
199 return -1;
200 for (i = 0; i < nb_sectors; i++)
201 set_bit(s->cow_bitmap, sector_num + i);
202 return 0;
203 }
205 static void cow_close(BlockDriverState *bs)
206 {
207 BDRVCowState *s = bs->opaque;
208 munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
209 close(s->fd);
210 }
212 static int cow_create(const char *filename, int64_t image_sectors,
213 const char *image_filename, int flags)
214 {
215 int fd, cow_fd;
216 struct cow_header_v2 cow_header;
217 struct stat st;
219 if (flags)
220 return -ENOTSUP;
222 cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
223 0644);
224 if (cow_fd < 0)
225 return -1;
226 memset(&cow_header, 0, sizeof(cow_header));
227 cow_header.magic = cpu_to_be32(COW_MAGIC);
228 cow_header.version = cpu_to_be32(COW_VERSION);
229 if (image_filename) {
230 fd = open(image_filename, O_RDONLY | O_BINARY);
231 if (fd < 0) {
232 close(cow_fd);
233 return -1;
234 }
235 if (fstat(fd, &st) != 0) {
236 close(fd);
237 return -1;
238 }
239 close(fd);
240 cow_header.mtime = cpu_to_be32(st.st_mtime);
241 realpath(image_filename, cow_header.backing_file);
242 }
243 cow_header.sectorsize = cpu_to_be32(512);
244 cow_header.size = cpu_to_be64(image_sectors * 512);
245 write(cow_fd, &cow_header, sizeof(cow_header));
246 /* resize to include at least all the bitmap */
247 ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
248 close(cow_fd);
249 return 0;
250 }
252 BlockDriver bdrv_cow = {
253 "cow",
254 sizeof(BDRVCowState),
255 cow_probe,
256 cow_open,
257 cow_read,
258 cow_write,
259 cow_close,
260 cow_create,
261 cow_is_allocated,
262 };
263 #endif