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 "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
  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  */
  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                         sprintf(tmp, "%s-XXXXXX", filename);
  98                         fd = mkstemp(tmp);
  99                         if (fd >= 0) {
 100                                 file = fdopen(fd, "w");
 101                                 opened = tmp;
 102                         }
 103                         fchmod(fd, 0644);
 104                 }
 105         }
 106
 107         if (!file) {
 108                 file = fopen(filename, "w");
 109                 opened = filename;
 110         }
 111
 112         DBG(DEBUG_SAVE,
 113             printf("writing cache file %s (really %s)\n",
 114                    filename, opened));
 115
 116         if (!file) {
 117                 ret = errno;
 118                 goto errout;
 119         }
 120
 121         list_for_each(p, &cache->bic_devs) {
 122                 blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
 123                 if (!dev->bid_type)
 124                         continue;
 125                 if ((ret = save_dev(dev, file)) < 0)
 126                         break;
 127         }
 128
 129         if (ret >= 0) {
 130                 cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
 131                 ret = 1;
 132         }
 133
 134         fclose(file);
 135         if (opened != filename) {
 136                 if (ret < 0) {
 137                         unlink(opened);
 138                         DBG(DEBUG_SAVE,
 139                             printf("unlinked temp cache %s\n", opened));
 140                 } else {
 141                         char *backup;
 142
 143                         backup = malloc(strlen(filename) + 5);
 144                         if (backup) {
 145                                 sprintf(backup, "%s.old", filename);
 146                                 unlink(backup);
 147                                 link(filename, backup);
 148                                 free(backup);
 149                         }
 150                         rename(opened, filename);
 151                         DBG(DEBUG_SAVE,
 152                             printf("moved temp cache %s\n", opened));
 153                 }
 154         }
 155
 156 errout:
 157         free(tmp);
 158         return ret;
 159 }
 160
 161 #ifdef TEST_PROGRAM
 162 int main(int argc, char **argv)
 163 {
 164         blkid_cache cache = NULL;
 165         int ret;
 166
 167         blkid_debug_mask = DEBUG_ALL;
 168         if (argc > 2) {
 169                 fprintf(stderr, "Usage: %s [filename]\n"
 170                         "Test loading/saving a cache (filename)\n", argv[0]);
 171                 exit(1);
 172         }
 173
 174         if ((ret = blkid_get_cache(&cache, "/dev/null")) != 0) {
 175                 fprintf(stderr, "%s: error creating cache (%d)\n",
 176                         argv[0], ret);
 177                 exit(1);
 178         }
 179         if ((ret = blkid_probe_all(cache)) < 0) {
 180                 fprintf(stderr, "error (%d) probing devices\n", ret);
 181                 exit(1);
 182         }
 183         cache->bic_filename = blkid_strdup(argv[1]);
 184
 185         if ((ret = blkid_flush_cache(cache)) < 0) {
 186                 fprintf(stderr, "error (%d) saving cache\n", ret);
 187                 exit(1);
 188         }
 189
 190         blkid_put_cache(cache);
 191
 192         return ret;
 193 }
 194 #endif