libblkid/src/save.c

   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_ERRNO_H
  22 #include <errno.h>
  23 #endif
  24 #include "blkidP.h"
  25
  26 static int save_dev(blkid_dev dev, FILE *file)
  27 {
  28         struct list_head *p;
  29
  30         if (!dev || dev->bid_name[0] != '/')
  31                 return 0;
  32
  33         DBG(DEBUG_SAVE,
  34             printf("device %s, type %s\n", dev->bid_name, dev->bid_type ?
  35                    dev->bid_type : "(null)"));
  36
  37         fprintf(file, "<device DEVNO=\"0x%04lx\" TIME=\"%ld.%ld\"",
  38                         (unsigned long) dev->bid_devno,
  39                         (long) dev->bid_time,
  40                         (long) dev->bid_utime);
  41
  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         char *opened = NULL;
  61         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 :
  76                                          blkid_get_cache_filename(NULL);
  77         if (!filename)
  78                 return -BLKID_ERR_PARAM;
  79
  80         if (strncmp(filename,
  81             BLKID_RUNTIME_DIR "/", sizeof(BLKID_RUNTIME_DIR)) == 0) {
  82
  83                 /* default destination, create the directory if necessary */
  84                 if (stat(BLKID_RUNTIME_DIR, &st) && errno == ENOENT) {
  85
  86                         mkdir(BLKID_RUNTIME_DIR, S_IWUSR|
  87                                                  S_IRUSR|S_IRGRP|S_IROTH|
  88                                                  S_IXUSR|S_IXGRP|S_IXOTH);
  89                 }
  90         }
  91
  92         /* If we can't write to the cache file, then don't even try */
  93         if (((ret = stat(filename, &st)) < 0 && errno != ENOENT) ||
  94             (ret == 0 && access(filename, W_OK) < 0)) {
  95                 DBG(DEBUG_SAVE,
  96                     printf("can't write to cache file %s\n", filename));
  97                 return 0;
  98         }
  99
 100         /*
 101          * Try and create a temporary file in the same directory so
 102          * that in case of error we don't overwrite the cache file.
 103          * If the cache file doesn't yet exist, it isn't a regular
 104          * file (e.g. /dev/null or a socket), or we couldn't create
 105          * a temporary file then we open it directly.
 106          */
 107         if (ret == 0 && S_ISREG(st.st_mode)) {
 108                 tmp = malloc(strlen(filename) + 8);
 109                 if (tmp) {
 110                         sprintf(tmp, "%s-XXXXXX", filename);
 111                         fd = mkstemp(tmp);
 112                         if (fd >= 0) {
 113                                 if (fchmod(fd, 0644) != 0)
 114                                         DBG(DEBUG_SAVE, printf("%s: fchmod failed\n", filename));
 115                                 else if ((file = fdopen(fd, "w")))
 116                                         opened = tmp;
 117                                 if (!file)
 118                                         close(fd);
 119                         }
 120                 }
 121         }
 122
 123         if (!file) {
 124                 file = fopen(filename, "w");
 125                 opened = filename;
 126         }
 127
 128         DBG(DEBUG_SAVE,
 129             printf("writing cache file %s (really %s)\n",
 130                    filename, opened));
 131
 132         if (!file) {
 133                 ret = errno;
 134                 goto errout;
 135         }
 136
 137         list_for_each(p, &cache->bic_devs) {
 138                 blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
 139                 if (!dev->bid_type || (dev->bid_flags & BLKID_BID_FL_REMOVABLE))
 140                         continue;
 141                 if ((ret = save_dev(dev, file)) < 0)
 142                         break;
 143         }
 144
 145         if (ret >= 0) {
 146                 cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
 147                 ret = 1;
 148         }
 149
 150         fclose(file);
 151         if (opened != filename) {
 152                 if (ret < 0) {
 153                         unlink(opened);
 154                         DBG(DEBUG_SAVE,
 155                             printf("unlinked temp cache %s\n", opened));
 156                 } else {
 157                         char *backup;
 158
 159                         backup = malloc(strlen(filename) + 5);
 160                         if (backup) {
 161                                 sprintf(backup, "%s.old", filename);
 162                                 unlink(backup);
 163                                 if (link(filename, backup)) {
 164                                         DBG(DEBUG_SAVE,
 165                                                 printf("can't link %s to %s\n",
 166                                                         filename, backup));
 167                                 }
 168                                 free(backup);
 169                         }
 170                         if (rename(opened, filename)) {
 171                                 ret = errno;
 172                                 DBG(DEBUG_SAVE,
 173                                         printf("can't rename %s to %s\n",
 174                                                 opened, filename));
 175                         } else {
 176                                 DBG(DEBUG_SAVE,
 177                                     printf("moved temp cache %s\n", opened));
 178                         }
 179                 }
 180         }
 181
 182 errout:
 183         free(tmp);
 184         if (filename != cache->bic_filename)
 185                 free(filename);
 186         return ret;
 187 }
 188
 189 #ifdef TEST_PROGRAM
 190 int main(int argc, char **argv)
 191 {
 192         blkid_cache cache = NULL;
 193         int ret;
 194
 195         blkid_init_debug(DEBUG_ALL);
 196         if (argc > 2) {
 197                 fprintf(stderr, "Usage: %s [filename]\n"
 198                         "Test loading/saving a cache (filename)\n", argv[0]);
 199                 exit(1);
 200         }
 201
 202         if ((ret = blkid_get_cache(&cache, "/dev/null")) != 0) {
 203                 fprintf(stderr, "%s: error creating cache (%d)\n",
 204                         argv[0], ret);
 205                 exit(1);
 206         }
 207         if ((ret = blkid_probe_all(cache)) < 0) {
 208                 fprintf(stderr, "error (%d) probing devices\n", ret);
 209                 exit(1);
 210         }
 211         cache->bic_filename = strdup(argv[1]);
 212
 213         if ((ret = blkid_flush_cache(cache)) < 0) {
 214                 fprintf(stderr, "error (%d) saving cache\n", ret);
 215                 exit(1);
 216         }
 217
 218         blkid_put_cache(cache);
 219
 220         return ret;
 221 }
 222 #endif