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 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 */ 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 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
