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 dev->bid_type : "(null)"));
39
40 fprintf(file,
41 "<device DEVNO=\"0x%04lx\" TIME=\"%ld\"",
42 (unsigned long) dev->bid_devno, (long) dev->bid_time);
43 if (dev->bid_pri)
44 fprintf(file, " PRI=\"%d\"", dev->bid_pri);
45 list_for_each(p, &dev->bid_tags) {
46 blkid_tag tag = list_entry(p, struct blkid_struct_tag, bit_tags);
47 fprintf(file, " %s=\"%s\"", tag->bit_name,tag->bit_val);
48 }
49 fprintf(file, ">%s</device>\n", dev->bid_name);
50
51 return 0;
52 }
53
54 /*
55 * Write out the cache struct to the cache file on disk.
56 */
blkid_flush_cache(blkid_cache cache)57 int blkid_flush_cache(blkid_cache cache)
58 {
59 struct list_head *p;
60 char *tmp = NULL;
61 const char *opened = NULL;
62 const char *filename;
63 FILE *file = NULL;
64 int fd, ret = 0;
65 struct stat st;
66
67 if (!cache)
68 return -BLKID_ERR_PARAM;
69
70 if (list_empty(&cache->bic_devs) ||
71 !(cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
72 DBG(DEBUG_SAVE, printf("skipping cache file write\n"));
73 return 0;
74 }
75
76 filename = cache->bic_filename ? cache->bic_filename: BLKID_CACHE_FILE;
77
78 /* If we can't write to the cache file, then don't even try */
79 if (((ret = stat(filename, &st)) < 0 && errno != ENOENT) ||
80 (ret == 0 && access(filename, W_OK) < 0)) {
81 DBG(DEBUG_SAVE,
82 printf("can't write to cache file %s\n", filename));
83 return 0;
84 }
85
86 /*
87 * Try and create a temporary file in the same directory so
88 * that in case of error we don't overwrite the cache file.
89 * If the cache file doesn't yet exist, it isn't a regular
90 * file (e.g. /dev/null or a socket), or we couldn't create
91 * a temporary file then we open it directly.
92 */
93 if (ret == 0 && S_ISREG(st.st_mode)) {
94 tmp = malloc(strlen(filename) + 8);
95 if (tmp) {
96 sprintf(tmp, "%s-XXXXXX", filename);
97 fd = mkstemp(tmp);
98 if (fd >= 0) {
99 file = fdopen(fd, "w");
100 opened = tmp;
101 }
102 fchmod(fd, 0644);
103 }
104 }
105
106 if (!file) {
107 file = fopen(filename, "w");
108 opened = filename;
109 }
110
111 DBG(DEBUG_SAVE,
112 printf("writing cache file %s (really %s)\n",
113 filename, opened));
114
115 if (!file) {
116 ret = errno;
117 goto errout;
118 }
119
120 list_for_each(p, &cache->bic_devs) {
121 blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
122 if (!dev->bid_type)
123 continue;
124 if ((ret = save_dev(dev, file)) < 0)
125 break;
126 }
127
128 if (ret >= 0) {
129 cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
130 ret = 1;
131 }
132
133 fclose(file);
134 if (opened != filename) {
135 if (ret < 0) {
136 unlink(opened);
137 DBG(DEBUG_SAVE,
138 printf("unlinked temp cache %s\n", opened));
139 } else {
140 char *backup;
141
142 backup = malloc(strlen(filename) + 5);
143 if (backup) {
144 sprintf(backup, "%s.old", filename);
145 unlink(backup);
146 link(filename, backup);
147 free(backup);
148 }
149 rename(opened, filename);
150 DBG(DEBUG_SAVE,
151 printf("moved temp cache %s\n", opened));
152 }
153 }
154
155 errout:
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