libblkid/src/cache.c

   1 /*
   2  * cache.c - allocation/initialization/free routines for cache
   3  *
   4  * Copyright (C) 2001 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 #ifdef HAVE_UNISTD_H
  14 #include <unistd.h>
  15 #endif
  16 #ifdef HAVE_ERRNO_H
  17 #include <errno.h>
  18 #endif
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #ifdef HAVE_SYS_STAT_H
  22 #include <sys/stat.h>
  23 #endif
  24 #include "blkidP.h"
  25 #include "env.h"
  26
  27 int blkid_debug_mask = 0;
  28
  29 /**
  30  * SECTION:cache
  31  * @title: Cache
  32  * @short_description: basic routines to work with libblkid cache
  33  *
  34  * Block device information is normally kept in a cache file blkid.tab and is
  35  * verified to still be valid before being returned to the user (if the user has
  36  * read permission on the raw block device, otherwise not).  The cache file also
  37  * allows unprivileged users (normally anyone other than root, or those not in the
  38  * "disk" group) to locate devices by label/id.  The standard location of the
  39  * cache file can be overridden by the environment variable BLKID_FILE.
  40  *
  41  * In situations where one is getting information about a single known device, it
  42  * does not impact performance whether the cache is used or not (unless you are
  43  * not able to read the block device directly).  If you are dealing with multiple
  44  * devices, use of the cache is highly recommended (even if empty) as devices will
  45  * be scanned at most one time and the on-disk cache will be updated if possible.
  46  * There is rarely a reason not to use the cache.
  47  *
  48  * In some cases (modular kernels), block devices are not even visible until after
  49  * they are accessed the first time, so it is critical that there is some way to
  50  * locate these devices without enumerating only visible devices, so the use of
  51  * the cache file is required in this situation.
  52  */
  53
  54 #if 0 /* ifdef CONFIG_BLKID_DEBUG */
  55 static blkid_debug_dump_cache(int mask, blkid_cache cache)
  56 {
  57         struct list_head *p;
  58
  59         if (!cache) {
  60                 printf("cache: NULL\n");
  61                 return;
  62         }
  63
  64         printf("cache: time = %lu\n", cache->bic_time);
  65         printf("cache: flags = 0x%08X\n", cache->bic_flags);
  66
  67         list_for_each(p, &cache->bic_devs) {
  68                 blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
  69                 blkid_debug_dump_dev(dev);
  70         }
  71 }
  72 #endif
  73
  74 #ifdef CONFIG_BLKID_DEBUG
  75 void blkid_init_debug(int mask)
  76 {
  77         if (blkid_debug_mask & DEBUG_INIT)
  78                 return;
  79
  80         if (!mask)
  81         {
  82                 char *dstr = getenv("LIBBLKID_DEBUG");
  83
  84                 if (!dstr)
  85                         dstr = getenv("BLKID_DEBUG");   /* for backward compatibility */
  86                 if (dstr)
  87                         blkid_debug_mask = strtoul(dstr, 0, 0);
  88         } else
  89                 blkid_debug_mask = mask;
  90
  91         if (blkid_debug_mask)
  92                 printf("libblkid: debug mask set to 0x%04x.\n", blkid_debug_mask);
  93
  94         blkid_debug_mask |= DEBUG_INIT;
  95 }
  96 #endif
  97
  98 static const char *get_default_cache_filename(void)
  99 {
 100         struct stat st;
 101
 102         if (stat(BLKID_RUNTIME_TOPDIR, &st) == 0 && S_ISDIR(st.st_mode))
 103                 return BLKID_CACHE_FILE;        /* cache in /run */
 104
 105         return BLKID_CACHE_FILE_OLD;    /* cache in /etc */
 106 }
 107
 108 /* returns allocated path to cache */
 109 char *blkid_get_cache_filename(struct blkid_config *conf)
 110 {
 111         char *filename;
 112
 113         filename = safe_getenv("BLKID_FILE");
 114         if (filename)
 115                 filename = blkid_strdup(filename);
 116         else if (conf)
 117                 filename = blkid_strdup(conf->cachefile);
 118         else {
 119                 struct blkid_config *c = blkid_read_config(NULL);
 120                 if (!c)
 121                         filename = blkid_strdup(get_default_cache_filename());
 122                 else {
 123                         filename = c->cachefile;  /* already allocated */
 124                         c->cachefile = NULL;
 125                         blkid_free_config(c);
 126                 }
 127         }
 128         return filename;
 129 }
 130
 131 /**
 132  * blkid_get_cache:
 133  * @cache: pointer to return cache handler
 134  * @filename: path to the cache file or NULL for the default path
 135  *
 136  * Allocates and initialize librray cache handler.
 137  *
 138  * Returns: 0 on success or number less than zero in case of error.
 139  */
 140 int blkid_get_cache(blkid_cache *ret_cache, const char *filename)
 141 {
 142         blkid_cache cache;
 143
 144         blkid_init_debug(0);
 145
 146         DBG(DEBUG_CACHE, printf("creating blkid cache (using %s)\n",
 147                                 filename ? filename : "default cache"));
 148
 149         if (!(cache = (blkid_cache) calloc(1, sizeof(struct blkid_struct_cache))))
 150                 return -BLKID_ERR_MEM;
 151
 152         INIT_LIST_HEAD(&cache->bic_devs);
 153         INIT_LIST_HEAD(&cache->bic_tags);
 154
 155         if (filename && !*filename)
 156                 filename = NULL;
 157         if (filename)
 158                 cache->bic_filename = blkid_strdup(filename);
 159         else
 160                 cache->bic_filename = blkid_get_cache_filename(NULL);
 161
 162         blkid_read_cache(cache);
 163         *ret_cache = cache;
 164         return 0;
 165 }
 166
 167 /**
 168  * blkid_put_cache:
 169  * @cache: cache handler
 170  *
 171  * Saves changes to cache file.
 172  */
 173 void blkid_put_cache(blkid_cache cache)
 174 {
 175         if (!cache)
 176                 return;
 177
 178         (void) blkid_flush_cache(cache);
 179
 180         DBG(DEBUG_CACHE, printf("freeing cache struct\n"));
 181
 182         /* DBG(DEBUG_CACHE, blkid_debug_dump_cache(cache)); */
 183
 184         while (!list_empty(&cache->bic_devs)) {
 185                 blkid_dev dev = list_entry(cache->bic_devs.next,
 186                                            struct blkid_struct_dev,
 187                                             bid_devs);
 188                 blkid_free_dev(dev);
 189         }
 190
 191         while (!list_empty(&cache->bic_tags)) {
 192                 blkid_tag tag = list_entry(cache->bic_tags.next,
 193                                            struct blkid_struct_tag,
 194                                            bit_tags);
 195
 196                 while (!list_empty(&tag->bit_names)) {
 197                         blkid_tag bad = list_entry(tag->bit_names.next,
 198                                                    struct blkid_struct_tag,
 199                                                    bit_names);
 200
 201                         DBG(DEBUG_CACHE, printf("warning: unfreed tag %s=%s\n",
 202                                                 bad->bit_name, bad->bit_val));
 203                         blkid_free_tag(bad);
 204                 }
 205                 blkid_free_tag(tag);
 206         }
 207
 208         blkid_free_probe(cache->probe);
 209
 210         free(cache->bic_filename);
 211         free(cache);
 212 }
 213
 214 /**
 215  * blkid_gc_cache:
 216  * @cache: cache handler
 217  *
 218  * Removes garbage (non-existing devices) from the cache.
 219  */
 220 void blkid_gc_cache(blkid_cache cache)
 221 {
 222         struct list_head *p, *pnext;
 223         struct stat st;
 224
 225         if (!cache)
 226                 return;
 227
 228         list_for_each_safe(p, pnext, &cache->bic_devs) {
 229                 blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
 230                 if (stat(dev->bid_name, &st) < 0) {
 231                         DBG(DEBUG_CACHE,
 232                             printf("freeing %s\n", dev->bid_name));
 233                         blkid_free_dev(dev);
 234                         cache->bic_flags |= BLKID_BIC_FL_CHANGED;
 235                 } else {
 236                         DBG(DEBUG_CACHE,
 237                             printf("Device %s exists\n", dev->bid_name));
 238                 }
 239         }
 240 }
 241
 242 #ifdef TEST_PROGRAM
 243 int main(int argc, char** argv)
 244 {
 245         blkid_cache cache = NULL;
 246         int ret;
 247
 248         blkid_init_debug(DEBUG_ALL);
 249
 250         if ((argc > 2)) {
 251                 fprintf(stderr, "Usage: %s [filename] \n", argv[0]);
 252                 exit(1);
 253         }
 254
 255         if ((ret = blkid_get_cache(&cache, argv[1])) < 0) {
 256                 fprintf(stderr, "error %d parsing cache file %s\n", ret,
 257                         argv[1] ? argv[1] : blkid_get_cache_filename(NULL));
 258                 exit(1);
 259         }
 260         if ((ret = blkid_get_cache(&cache, "/dev/null")) != 0) {
 261                 fprintf(stderr, "%s: error creating cache (%d)\n",
 262                         argv[0], ret);
 263                 exit(1);
 264         }
 265         if ((ret = blkid_probe_all(cache)) < 0)
 266                 fprintf(stderr, "error probing devices\n");
 267
 268         blkid_put_cache(cache);
 269
 270         return ret;
 271 }
 272 #endif