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/*
* cache.c - allocation/initialization/free routines for cache
*
* Copyright (C) 2001 Andreas Dilger
* Copyright (C) 2003 Theodore Ts'o
*
* %Begin-Header%
* This file may be redistributed under the terms of the
* GNU Lesser General Public License.
* %End-Header%
*/
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#include "blkidP.h"
#include "env.h"
/**
* SECTION:cache
* @title: Cache
* @short_description: basic routines to work with libblkid cache
*
* Block device information is normally kept in a cache file blkid.tab and is
* verified to still be valid before being returned to the user (if the user has
* read permission on the raw block device, otherwise not). The cache file also
* allows unprivileged users (normally anyone other than root, or those not in the
* "disk" group) to locate devices by label/id. The standard location of the
* cache file can be overridden by the environment variable BLKID_FILE.
*
* In situations where one is getting information about a single known device, it
* does not impact performance whether the cache is used or not (unless you are
* not able to read the block device directly). If you are dealing with multiple
* devices, use of the cache is highly recommended (even if empty) as devices will
* be scanned at most one time and the on-disk cache will be updated if possible.
* There is rarely a reason not to use the cache.
*
* In some cases (modular kernels), block devices are not even visible until after
* they are accessed the first time, so it is critical that there is some way to
* locate these devices without enumerating only visible devices, so the use of
* the cache file is required in this situation.
*/
static const char *get_default_cache_filename(void)
{
struct stat st;
if (stat(BLKID_RUNTIME_TOPDIR, &st) == 0 && S_ISDIR(st.st_mode))
return BLKID_CACHE_FILE; /* cache in /run */
return BLKID_CACHE_FILE_OLD; /* cache in /etc */
}
/* returns allocated path to cache */
char *blkid_get_cache_filename(struct blkid_config *conf)
{
char *filename;
filename = safe_getenv("BLKID_FILE");
if (filename)
filename = strdup(filename);
else if (conf)
filename = conf->cachefile ? strdup(conf->cachefile) : NULL;
else {
struct blkid_config *c = blkid_read_config(NULL);
if (!c)
filename = strdup(get_default_cache_filename());
else {
filename = c->cachefile; /* already allocated */
c->cachefile = NULL;
blkid_free_config(c);
}
}
return filename;
}
/**
* blkid_get_cache:
* @cache: pointer to return cache handler
* @filename: path to the cache file or NULL for the default path
*
* Allocates and initialize library cache handler.
*
* Returns: 0 on success or number less than zero in case of error.
*/
int blkid_get_cache(blkid_cache *ret_cache, const char *filename)
{
blkid_cache cache;
if (!ret_cache)
return -BLKID_ERR_PARAM;
blkid_init_debug(0);
if (!(cache = calloc(1, sizeof(struct blkid_struct_cache))))
return -BLKID_ERR_MEM;
DBG(CACHE, ul_debugobj(cache, "alloc (from %s)", filename ? filename : "default cache"));
INIT_LIST_HEAD(&cache->bic_devs);
INIT_LIST_HEAD(&cache->bic_tags);
if (filename && !*filename)
filename = NULL;
if (filename)
cache->bic_filename = strdup(filename);
else
cache->bic_filename = blkid_get_cache_filename(NULL);
blkid_read_cache(cache);
*ret_cache = cache;
return 0;
}
/**
* blkid_put_cache:
* @cache: cache handler
*
* Saves changes to cache file.
*/
void blkid_put_cache(blkid_cache cache)
{
if (!cache)
return;
(void) blkid_flush_cache(cache);
DBG(CACHE, ul_debugobj(cache, "freeing cache struct"));
/* DBG(CACHE, ul_debug_dump_cache(cache)); */
while (!list_empty(&cache->bic_devs)) {
blkid_dev dev = list_entry(cache->bic_devs.next,
struct blkid_struct_dev,
bid_devs);
blkid_free_dev(dev);
}
DBG(CACHE, ul_debugobj(cache, "freeing cache tag heads"));
while (!list_empty(&cache->bic_tags)) {
blkid_tag tag = list_entry(cache->bic_tags.next,
struct blkid_struct_tag,
bit_tags);
while (!list_empty(&tag->bit_names)) {
blkid_tag bad = list_entry(tag->bit_names.next,
struct blkid_struct_tag,
bit_names);
DBG(CACHE, ul_debugobj(cache, "warning: unfreed tag %s=%s",
bad->bit_name, bad->bit_val));
blkid_free_tag(bad);
}
blkid_free_tag(tag);
}
blkid_free_probe(cache->probe);
free(cache->bic_filename);
free(cache);
}
/**
* blkid_gc_cache:
* @cache: cache handler
*
* Removes garbage (non-existing devices) from the cache.
*/
void blkid_gc_cache(blkid_cache cache)
{
struct list_head *p, *pnext;
struct stat st;
if (!cache)
return;
list_for_each_safe(p, pnext, &cache->bic_devs) {
blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
if (stat(dev->bid_name, &st) < 0) {
DBG(CACHE, ul_debugobj(cache, "freeing non-exiting %s", dev->bid_name));
blkid_free_dev(dev);
cache->bic_flags |= BLKID_BIC_FL_CHANGED;
} else {
DBG(CACHE, ul_debug("Device %s exists", dev->bid_name));
}
}
}
#ifdef TEST_PROGRAM
int main(int argc, char** argv)
{
blkid_cache cache = NULL;
int ret;
blkid_init_debug(BLKID_DEBUG_ALL);
if ((argc > 2)) {
fprintf(stderr, "Usage: %s [filename] \n", argv[0]);
exit(1);
}
if ((ret = blkid_get_cache(&cache, argv[1])) < 0) {
fprintf(stderr, "error %d parsing cache file %s\n", ret,
argv[1] ? argv[1] : blkid_get_cache_filename(NULL));
exit(1);
}
if ((ret = blkid_get_cache(&cache, "/dev/null")) != 0) {
fprintf(stderr, "%s: error creating cache (%d)\n",
argv[0], ret);
exit(1);
}
if ((ret = blkid_probe_all(cache)) < 0)
fprintf(stderr, "error probing devices\n");
blkid_put_cache(cache);
return ret;
}
#endif
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