lib/blkid/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_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=\"%lu\"",
  41                 (unsigned long) dev->bid_devno, 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