1 /*
2 * save.c - write the cache struct to disk
3 *
4 * Copyright (C) 2001 by Andreas Dilger
5 * Copyright (C) 2003 Theodore Ts'o
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the
9 * GNU Lesser General Public License.
10 * %End-Header%
11 */
12
13 #include <stdio.h>
14 #include <string.h>
15 #include <stdlib.h>
16 #include <unistd.h>
17 #include <sys/types.h>
18 #ifdef HAVE_SYS_STAT_H
19 #include <sys/stat.h>
20 #endif
21 #ifdef HAVE_SYS_MKDEV_H
22 #include <sys/mkdev.h>
23 #endif
24 #ifdef HAVE_ERRNO_H
25 #include <errno.h>
26 #endif
27 #include "blkidP.h"
28
save_dev(blkid_dev dev,FILE * file)29 static int save_dev(blkid_dev dev, FILE *file)
30 {
31 struct list_head *p;
32
33 if (!dev || dev->bid_name[0] != '/')
34 return 0;
35
36 DBG(DEBUG_SAVE,
37 printf("device %s, type %s\n", dev->bid_name, dev->bid_type));
38
39 fprintf(file,
40 "<device DEVNO=\"0x%04lx\" TIME=\"%ld\"",
41 (unsigned long) dev->bid_devno, (long) dev->bid_time);
42 if (dev->bid_pri)
43 fprintf(file, " PRI=\"%d\"", dev->bid_pri);
44 list_for_each(p, &dev->bid_tags) {
45 blkid_tag tag = list_entry(p, struct blkid_struct_tag, bit_tags);
46 fprintf(file, " %s=\"%s\"", tag->bit_name,tag->bit_val);
47 }
48 fprintf(file, ">%s</device>\n", dev->bid_name);
49
50 return 0;
51 }
52
53 /*
54 * Write out the cache struct to the cache file on disk.
55 */
blkid_flush_cache(blkid_cache cache)56 int blkid_flush_cache(blkid_cache cache)
57 {
58 struct list_head *p;
59 char *tmp = NULL;
60 const char *opened = NULL;
61 const char *filename;
62 FILE *file = NULL;
63 int fd, ret = 0;
64 struct stat st;
65
66 if (!cache)
67 return -BLKID_ERR_PARAM;
68
69 if (list_empty(&cache->bic_devs) ||
70 !(cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
71 DBG(DEBUG_SAVE, printf("skipping cache file write\n"));
72 return 0;
73 }
74
75 filename = cache->bic_filename ? cache->bic_filename: BLKID_CACHE_FILE;
76
77 /* If we can't write to the cache file, then don't even try */
78 if (((ret = stat(filename, &st)) < 0 && errno != ENOENT) ||
79 (ret == 0 && access(filename, W_OK) < 0)) {
80 DBG(DEBUG_SAVE,
81 printf("can't write to cache file %s\n", filename));
82 return 0;
83 }
84
85 /*
86 * Try and create a temporary file in the same directory so
87 * that in case of error we don't overwrite the cache file.
88 * If the cache file doesn't yet exist, it isn't a regular
89 * file (e.g. /dev/null or a socket), or we couldn't create
90 * a temporary file then we open it directly.
91 */
92 if (ret == 0 && S_ISREG(st.st_mode)) {
93 tmp = malloc(strlen(filename) + 8);
94 if (tmp) {
95 sprintf(tmp, "%s-XXXXXX", filename);
96 fd = mkstemp(tmp);
97 if (fd >= 0) {
98 file = fdopen(fd, "w");
99 opened = tmp;
100 }
101 fchmod(fd, 0644);
102 }
103 }
104
105 if (!file) {
106 file = fopen(filename, "w");
107 opened = filename;
108 }
109
110 DBG(DEBUG_SAVE,
111 printf("writing cache file %s (really %s)\n",
112 filename, opened));
113
114 if (!file) {
115 ret = errno;
116 goto errout;
117 }
118
119 list_for_each(p, &cache->bic_devs) {
120 blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
121 if (!dev->bid_type)
122 continue;
123 if ((ret = save_dev(dev, file)) < 0)
124 break;
125 }
126
127 if (ret >= 0) {
128 cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
129 ret = 1;
130 }
131
132 fclose(file);
133 if (opened != filename) {
134 if (ret < 0) {
135 unlink(opened);
136 DBG(DEBUG_SAVE,
137 printf("unlinked temp cache %s\n", opened));
138 } else {
139 char *backup;
140
141 backup = malloc(strlen(filename) + 5);
142 if (backup) {
143 sprintf(backup, "%s.old", filename);
144 unlink(backup);
145 link(filename, backup);
146 free(backup);
147 }
148 rename(opened, filename);
149 DBG(DEBUG_SAVE,
150 printf("moved temp cache %s\n", opened));
151 }
152 }
153
154 errout:
155 if (tmp)
156 free(tmp);
157 return ret;
158 }
159
160 #ifdef TEST_PROGRAM
main(int argc,char ** argv)161 int main(int argc, char **argv)
162 {
163 blkid_cache cache = NULL;
164 int ret;
165
166 blkid_debug_mask = DEBUG_ALL;
167 if (argc > 2) {
168 fprintf(stderr, "Usage: %s [filename]\n"
169 "Test loading/saving a cache (filename)\n", argv[0]);
170 exit(1);
171 }
172
173 if ((ret = blkid_get_cache(&cache, "/dev/null")) != 0) {
174 fprintf(stderr, "%s: error creating cache (%d)\n",
175 argv[0], ret);
176 exit(1);
177 }
178 if ((ret = blkid_probe_all(cache)) < 0) {
179 fprintf(stderr, "error (%d) probing devices\n", ret);
180 exit(1);
181 }
182 cache->bic_filename = blkid_strdup(argv[1]);
183
184 if ((ret = blkid_flush_cache(cache)) < 0) {
185 fprintf(stderr, "error (%d) saving cache\n", ret);
186 exit(1);
187 }
188
189 blkid_put_cache(cache);
190
191 return ret;
192 }
193 #endif
194