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 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 */ 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 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
