shlibs/blkid/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_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_init_debug(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