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 "config.h"
14 #include <stdio.h>
15 #include <string.h>
16 #include <stdlib.h>
17 #include <unistd.h>
18 #include <sys/types.h>
19 #ifdef HAVE_SYS_STAT_H
20 #include <sys/stat.h>
21 #endif
22 #ifdef HAVE_SYS_MKDEV_H
23 #include <sys/mkdev.h>
24 #endif
25 #ifdef HAVE_ERRNO_H
26 #include <errno.h>
27 #endif
28 #include "blkidP.h"
29
save_dev(blkid_dev dev,FILE * file)30 static int save_dev(blkid_dev dev, FILE *file)
31 {
32 struct list_head *p;
33
34 if (!dev || dev->bid_name[0] != '/')
35 return 0;
36
37 DBG(DEBUG_SAVE,
38 printf("device %s, type %s\n", dev->bid_name, dev->bid_type ?
39 dev->bid_type : "(null)"));
40
41 fprintf(file,
42 "<device DEVNO=\"0x%04lx\" TIME=\"%ld\"",
43 (unsigned long) dev->bid_devno, (long) dev->bid_time);
44 if (dev->bid_pri)
45 fprintf(file, " PRI=\"%d\"", dev->bid_pri);
46 list_for_each(p, &dev->bid_tags) {
47 blkid_tag tag = list_entry(p, struct blkid_struct_tag, bit_tags);
48 fprintf(file, " %s=\"%s\"", tag->bit_name,tag->bit_val);
49 }
50 fprintf(file, ">%s</device>\n", dev->bid_name);
51
52 return 0;
53 }
54
55 /*
56 * Write out the cache struct to the cache file on disk.
57 */
blkid_flush_cache(blkid_cache cache)58 int blkid_flush_cache(blkid_cache cache)
59 {
60 struct list_head *p;
61 char *tmp = NULL;
62 const char *opened = NULL;
63 const char *filename;
64 FILE *file = NULL;
65 int fd, ret = 0;
66 struct stat st;
67
68 if (!cache)
69 return -BLKID_ERR_PARAM;
70
71 if (list_empty(&cache->bic_devs) ||
72 !(cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
73 DBG(DEBUG_SAVE, printf("skipping cache file write\n"));
74 return 0;
75 }
76
77 filename = cache->bic_filename ? cache->bic_filename: BLKID_CACHE_FILE;
78
79 /* If we can't write to the cache file, then don't even try */
80 if (((ret = stat(filename, &st)) < 0 && errno != ENOENT) ||
81 (ret == 0 && access(filename, W_OK) < 0)) {
82 DBG(DEBUG_SAVE,
83 printf("can't write to cache file %s\n", filename));
84 return 0;
85 }
86
87 /*
88 * Try and create a temporary file in the same directory so
89 * that in case of error we don't overwrite the cache file.
90 * If the cache file doesn't yet exist, it isn't a regular
91 * file (e.g. /dev/null or a socket), or we couldn't create
92 * a temporary file then we open it directly.
93 */
94 if (ret == 0 && S_ISREG(st.st_mode)) {
95 tmp = malloc(strlen(filename) + 8);
96 if (tmp) {
97 mode_t save_umask = umask(022);
98 sprintf(tmp, "%s-XXXXXX", filename);
99 fd = mkstemp(tmp);
100 umask(save_umask);
101 if (fd >= 0) {
102 file = fdopen(fd, "w");
103 opened = tmp;
104 }
105 fchmod(fd, 0644);
106 }
107 }
108
109 if (!file) {
110 file = fopen(filename, "w");
111 opened = filename;
112 }
113
114 DBG(DEBUG_SAVE,
115 printf("writing cache file %s (really %s)\n",
116 filename, opened));
117
118 if (!file) {
119 ret = errno;
120 goto errout;
121 }
122
123 list_for_each(p, &cache->bic_devs) {
124 blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
125 if (!dev->bid_type)
126 continue;
127 if ((ret = save_dev(dev, file)) < 0)
128 break;
129 }
130
131 if (ret >= 0) {
132 cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
133 ret = 1;
134 }
135
136 fclose(file);
137 if (opened != filename) {
138 if (ret < 0) {
139 (void) unlink(opened);
140 DBG(DEBUG_SAVE,
141 printf("unlinked temp cache %s\n", opened));
142 } else {
143 char *backup;
144
145 backup = malloc(strlen(filename) + 5);
146 if (backup) {
147 sprintf(backup, "%s.old", filename);
148 unlink(backup);
149 (void) link(filename, backup);
150 free(backup);
151 }
152 if (rename(opened, filename) < 0)
153 (void) unlink(opened);
154 DBG(DEBUG_SAVE,
155 printf("moved temp cache %s\n", opened));
156 }
157 }
158
159 errout:
160 free(tmp);
161 return ret;
162 }
163
164 #ifdef TEST_PROGRAM
main(int argc,char ** argv)165 int main(int argc, char **argv)
166 {
167 blkid_cache cache = NULL;
168 int ret;
169
170 blkid_debug_mask = DEBUG_ALL;
171 if (argc > 2) {
172 fprintf(stderr, "Usage: %s [filename]\n"
173 "Test loading/saving a cache (filename)\n", argv[0]);
174 exit(1);
175 }
176
177 if ((ret = blkid_get_cache(&cache, "/dev/null")) != 0) {
178 fprintf(stderr, "%s: error creating cache (%d)\n",
179 argv[0], ret);
180 exit(1);
181 }
182 if ((ret = blkid_probe_all(cache)) < 0) {
183 fprintf(stderr, "error (%d) probing devices\n", ret);
184 exit(1);
185 }
186 cache->bic_filename = blkid_strdup(argv[1]);
187
188 if ((ret = blkid_flush_cache(cache)) < 0) {
189 fprintf(stderr, "error (%d) saving cache\n", ret);
190 exit(1);
191 }
192
193 blkid_put_cache(cache);
194
195 return ret;
196 }
197 #endif
198