/*
* Copyright (C) 2016 David Sterba <dsterba@suse.cz>
* Copyright (C) 2016 Stanislav Brabec <sbrabec@suse.cz>
*
* This file may be redistributed under the terms of the
* GNU Lesser General Public License.
*/
/*
* SECTION: btrfs
* @title: btrfs
* @short_description: special function for btrfs
*
* btrfs contains function needed for manipulation with btrfs.
*/
#include <dirent.h>
#include <sys/ioctl.h>
#include <linux/magic.h>
#include "btrfs.h"
/*
* btrfs_get_default_subvol_id:
* @path: Path to mounted btrfs volume
*
* Searches for the btrfs default subvolume id.
*
* Returns: default subvolume id or UINT64_MAX (-1) in case of no
* default subvolume or error. In case of error, errno is set
* properly.
*/
uint64_t btrfs_get_default_subvol_id(const char *path)
{
int iocret;
int fd;
DIR *dirstream = NULL;
struct btrfs_ioctl_search_args args;
struct btrfs_ioctl_search_key *sk = &args.key;
struct btrfs_ioctl_search_header *sh;
uint64_t found = UINT64_MAX;
dirstream = opendir(path);
if (!dirstream) {
DBG(BTRFS, ul_debug("opendir() failed for \"%s\" [errno=%d %m]", path, errno));
return UINT64_MAX;
}
fd = dirfd(dirstream);
if (fd < 0) {
DBG(BTRFS, ul_debug("dirfd(opendir()) failed for \"%s\" [errno=%d %m]", path, errno));
goto out;
}
memset(&args, 0, sizeof(args));
sk->tree_id = BTRFS_ROOT_TREE_OBJECTID;
sk->min_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
sk->max_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
sk->min_type = BTRFS_DIR_ITEM_KEY;
sk->max_type = BTRFS_DIR_ITEM_KEY;
sk->max_offset = UINT64_MAX;
sk->max_transid = UINT64_MAX;
sk->nr_items = 1;
iocret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
if (iocret < 0) {
DBG(BTRFS, ul_debug("ioctl() failed for \"%s\" [errno=%d %m]", path, errno));
goto out;
}
/* the ioctl returns the number of items it found in nr_items */
if (sk->nr_items == 0) {
DBG(BTRFS, ul_debug("root tree dir object id not found"));
goto out;
}
DBG(BTRFS, ul_debug("found %d root tree dir object id items", sk->nr_items));
sh = (struct btrfs_ioctl_search_header *)args.buf;
if (sh->type == BTRFS_DIR_ITEM_KEY) {
struct btrfs_dir_item *di;
int name_len;
char *name;
di = (struct btrfs_dir_item *)(sh + 1);
name_len = btrfs_stack_dir_name_len(di);
name = (char *)(di + 1);
if (!strncmp("default", name, name_len)) {
found = btrfs_disk_key_objectid(&di->location);
DBG(BTRFS, ul_debug("\"default\" id is %llu", (unsigned long long)found));
} else {
DBG(BTRFS, ul_debug("\"default\" id not found in tree root"));
goto out;
}
} else {
DBG(BTRFS, ul_debug("unexpected type found: %d", (int)sh->type));
goto out;
}
out:
closedir(dirstream);
return found;
}
