btrfs-progs/libbtrfsutil/subvolume.c

/*
 * Copyright (C) 2018 Facebook
 *
 * This file is part of libbtrfsutil.
 *
 * libbtrfsutil is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * libbtrfsutil is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/vfs.h>
#include <linux/magic.h>

#include "btrfsutil_internal.h"

/*
 * This intentionally duplicates btrfs_util_is_subvolume_fd() instead of opening
 * a file descriptor and calling it, because fstat() and fstatfs() don't accept
 * file descriptors opened with O_PATH on old kernels (before v3.6 and before
 * v3.12, respectively), but stat() and statfs() can be called on a path that
 * the user doesn't have read or write permissions to.
 */
PUBLIC enum btrfs_util_error btrfs_util_is_subvolume(const char *path)
{
	struct statfs sfs;
	struct stat st;
	int ret;

	ret = statfs(path, &sfs);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_STATFS_FAILED;

	if (sfs.f_type != BTRFS_SUPER_MAGIC) {
		errno = EINVAL;
		return BTRFS_UTIL_ERROR_NOT_BTRFS;
	}

	ret = stat(path, &st);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_STAT_FAILED;

	if (st.st_ino != BTRFS_FIRST_FREE_OBJECTID || !S_ISDIR(st.st_mode)) {
		errno = EINVAL;
		return BTRFS_UTIL_ERROR_NOT_SUBVOLUME;
	}

	return BTRFS_UTIL_OK;
}

PUBLIC enum btrfs_util_error btrfs_util_is_subvolume_fd(int fd)
{
	struct statfs sfs;
	struct stat st;
	int ret;

	ret = fstatfs(fd, &sfs);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_STATFS_FAILED;

	if (sfs.f_type != BTRFS_SUPER_MAGIC) {
		errno = EINVAL;
		return BTRFS_UTIL_ERROR_NOT_BTRFS;
	}

	ret = fstat(fd, &st);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_STAT_FAILED;

	if (st.st_ino != BTRFS_FIRST_FREE_OBJECTID || !S_ISDIR(st.st_mode)) {
		errno = EINVAL;
		return BTRFS_UTIL_ERROR_NOT_SUBVOLUME;
	}

	return BTRFS_UTIL_OK;
}

PUBLIC enum btrfs_util_error btrfs_util_subvolume_id(const char *path,
						     uint64_t *id_ret)
{
	enum btrfs_util_error err;
	int fd;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return BTRFS_UTIL_ERROR_OPEN_FAILED;

	err = btrfs_util_subvolume_id_fd(fd, id_ret);
	SAVE_ERRNO_AND_CLOSE(fd);
	return err;
}

PUBLIC enum btrfs_util_error btrfs_util_subvolume_id_fd(int fd,
							uint64_t *id_ret)
{
	struct btrfs_ioctl_ino_lookup_args args = {
		.treeid = 0,
		.objectid = BTRFS_FIRST_FREE_OBJECTID,
	};
	int ret;

	ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP, &args);
	if (ret == -1) {
		close(fd);
		return BTRFS_UTIL_ERROR_INO_LOOKUP_FAILED;
	}

	*id_ret = args.treeid;

	return BTRFS_UTIL_OK;
}

PUBLIC enum btrfs_util_error btrfs_util_subvolume_path(const char *path,
						       uint64_t id,
						       char **path_ret)
{
	enum btrfs_util_error err;
	int fd;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return BTRFS_UTIL_ERROR_OPEN_FAILED;

	err = btrfs_util_subvolume_path_fd(fd, id, path_ret);
	SAVE_ERRNO_AND_CLOSE(fd);
	return err;
}

PUBLIC enum btrfs_util_error btrfs_util_subvolume_path_fd(int fd, uint64_t id,
							  char **path_ret)
{
	char *path, *p;
	size_t capacity = 4096;

	if (id == 0) {
		enum btrfs_util_error err;

		err = btrfs_util_is_subvolume_fd(fd);
		if (err)
			return err;

		err = btrfs_util_subvolume_id_fd(fd, &id);
		if (err)
			return err;
	}

	path = malloc(capacity);
	if (!path)
		return BTRFS_UTIL_ERROR_NO_MEMORY;
	p = path + capacity - 1;
	p[0] = '\0';

	while (id != BTRFS_FS_TREE_OBJECTID) {
		struct btrfs_ioctl_search_args search = {
			.key = {
				.tree_id = BTRFS_ROOT_TREE_OBJECTID,
				.min_objectid = id,
				.max_objectid = id,
				.min_type = BTRFS_ROOT_BACKREF_KEY,
				.max_type = BTRFS_ROOT_BACKREF_KEY,
				.min_offset = 0,
				.max_offset = UINT64_MAX,
				.min_transid = 0,
				.max_transid = UINT64_MAX,
				.nr_items = 1,
			},
		};
		struct btrfs_ioctl_ino_lookup_args lookup;
		const struct btrfs_ioctl_search_header *header;
		const struct btrfs_root_ref *ref;
		const char *name;
		uint16_t name_len;
		size_t lookup_len;
		size_t total_len;
		int ret;

		ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &search);
		if (ret == -1) {
			free(path);
			return BTRFS_UTIL_ERROR_SEARCH_FAILED;
		}

		if (search.key.nr_items == 0) {
			free(path);
			errno = ENOENT;
			return BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND;
		}

		header = (struct btrfs_ioctl_search_header *)search.buf;
		ref = (struct btrfs_root_ref *)(header + 1);
		name = (char *)(ref + 1);
		name_len = le16_to_cpu(ref->name_len);

		id = header->offset;

		lookup.treeid = id;
		lookup.objectid = le64_to_cpu(ref->dirid);
		ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP, &lookup);
		if (ret == -1) {
			free(path);
			return BTRFS_UTIL_ERROR_SEARCH_FAILED;
		}
		lookup_len = strlen(lookup.name);

		total_len = name_len + lookup_len + (id != BTRFS_FS_TREE_OBJECTID);
		if (p - total_len < path) {
			char *new_path, *new_p;
			size_t new_capacity = capacity * 2;

			new_path = malloc(new_capacity);
			if (!new_path) {
				free(path);
				return BTRFS_UTIL_ERROR_NO_MEMORY;
			}
			new_p = new_path + new_capacity - (path + capacity - p);
			memcpy(new_p, p, path + capacity - p);
			free(path);
			path = new_path;
			p = new_p;
			capacity = new_capacity;
		}
		p -= name_len;
		memcpy(p, name, name_len);
		p -= lookup_len;
		memcpy(p, lookup.name, lookup_len);
		if (id != BTRFS_FS_TREE_OBJECTID)
			*--p = '/';
	}

	if (p != path)
		memmove(path, p, path + capacity - p);

	*path_ret = path;

	return BTRFS_UTIL_OK;
}

static void copy_timespec(struct timespec *timespec,
			  const struct btrfs_timespec *btrfs_timespec)
{
	timespec->tv_sec = le64_to_cpu(btrfs_timespec->sec);
	timespec->tv_nsec = le32_to_cpu(btrfs_timespec->nsec);
}

static void copy_root_item(struct btrfs_util_subvolume_info *subvol,
			   const struct btrfs_root_item *root)
{
	subvol->flags = le64_to_cpu(root->flags);
	memcpy(subvol->uuid, root->uuid, sizeof(subvol->uuid));
	memcpy(subvol->parent_uuid, root->parent_uuid,
	       sizeof(subvol->parent_uuid));
	memcpy(subvol->received_uuid, root->received_uuid,
	       sizeof(subvol->received_uuid));
	subvol->generation = le64_to_cpu(root->generation);
	subvol->ctransid = le64_to_cpu(root->ctransid);
	subvol->otransid = le64_to_cpu(root->otransid);
	subvol->stransid = le64_to_cpu(root->stransid);
	subvol->rtransid = le64_to_cpu(root->rtransid);
	copy_timespec(&subvol->ctime, &root->ctime);
	copy_timespec(&subvol->otime, &root->otime);
	copy_timespec(&subvol->stime, &root->stime);
	copy_timespec(&subvol->rtime, &root->rtime);
}

PUBLIC enum btrfs_util_error btrfs_util_subvolume_info(const char *path,
						       uint64_t id,
						       struct btrfs_util_subvolume_info *subvol)
{
	enum btrfs_util_error err;
	int fd;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return BTRFS_UTIL_ERROR_OPEN_FAILED;

	err = btrfs_util_subvolume_info_fd(fd, id, subvol);
	SAVE_ERRNO_AND_CLOSE(fd);
	return err;
}

PUBLIC enum btrfs_util_error btrfs_util_subvolume_info_fd(int fd, uint64_t id,
							  struct btrfs_util_subvolume_info *subvol)
{
	struct btrfs_ioctl_search_args search = {
		.key = {
			.tree_id = BTRFS_ROOT_TREE_OBJECTID,
			.min_type = BTRFS_ROOT_ITEM_KEY,
			.max_type = BTRFS_ROOT_BACKREF_KEY,
			.min_offset = 0,
			.max_offset = UINT64_MAX,
			.min_transid = 0,
			.max_transid = UINT64_MAX,
			.nr_items = 0,
		},
	};
	enum btrfs_util_error err;
	size_t items_pos = 0, buf_off = 0;
	bool need_root_item = true, need_root_backref = true;
	int ret;

	if (id == 0) {
		err = btrfs_util_is_subvolume_fd(fd);
		if (err)
			return err;

		err = btrfs_util_subvolume_id_fd(fd, &id);
		if (err)
			return err;
	}

	if ((id < BTRFS_FIRST_FREE_OBJECTID && id != BTRFS_FS_TREE_OBJECTID) ||
	    id > BTRFS_LAST_FREE_OBJECTID) {
		errno = ENOENT;
		return BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND;
	}

	search.key.min_objectid = search.key.max_objectid = id;

	if (subvol) {
		subvol->id = id;
		subvol->parent_id = 0;
		subvol->dir_id = 0;
		if (id == BTRFS_FS_TREE_OBJECTID)
			need_root_backref = false;
	} else {
		/*
		 * We only need the backref for filling in the subvolume info.
		 */
		need_root_backref = false;
	}

	/* Don't bother searching for the backref if we don't need it. */
	if (!need_root_backref)
		search.key.max_type = BTRFS_ROOT_ITEM_KEY;

	while (need_root_item || need_root_backref) {
		const struct btrfs_ioctl_search_header *header;

		if (items_pos >= search.key.nr_items) {
			search.key.nr_items = 4096;
			ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &search);
			if (ret == -1)
				return BTRFS_UTIL_ERROR_SEARCH_FAILED;
			items_pos = 0;
			buf_off = 0;

			if (search.key.nr_items == 0) {
				if (need_root_item) {
					errno = ENOENT;
					return BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND;
				} else {
					break;
				}
			}
		}

		header = (struct btrfs_ioctl_search_header *)(search.buf + buf_off);
		if (header->type == BTRFS_ROOT_ITEM_KEY) {
			if (subvol) {
				const struct btrfs_root_item *root;

				root = (const struct btrfs_root_item *)(header + 1);
				copy_root_item(subvol, root);
			}
			need_root_item = false;
			search.key.min_type = BTRFS_ROOT_BACKREF_KEY;
		} else if (header->type == BTRFS_ROOT_BACKREF_KEY) {
			if (subvol) {
				const struct btrfs_root_ref *ref;

				ref = (const struct btrfs_root_ref *)(header + 1);
				subvol->parent_id = header->offset;
				subvol->dir_id = le64_to_cpu(ref->dirid);
			}
			need_root_backref = false;
			search.key.min_type = UINT32_MAX;
		}

		items_pos++;
		buf_off += sizeof(*header) + header->len;
	}

	return BTRFS_UTIL_OK;
}

PUBLIC enum btrfs_util_error btrfs_util_get_subvolume_read_only_fd(int fd,
								   bool *read_only_ret)
{
	uint64_t flags;
	int ret;

	ret = ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_SUBVOL_GETFLAGS_FAILED;

	*read_only_ret = flags & BTRFS_SUBVOL_RDONLY;
	return BTRFS_UTIL_OK;
}

PUBLIC enum btrfs_util_error btrfs_util_get_subvolume_read_only(const char *path,
								bool *ret)
{
	enum btrfs_util_error err;
	int fd;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return BTRFS_UTIL_ERROR_OPEN_FAILED;

	err = btrfs_util_get_subvolume_read_only_fd(fd, ret);
	SAVE_ERRNO_AND_CLOSE(fd);
	return err;
}

PUBLIC enum btrfs_util_error btrfs_util_set_subvolume_read_only(const char *path,
								bool read_only)
{
	enum btrfs_util_error err;
	int fd;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return BTRFS_UTIL_ERROR_OPEN_FAILED;

	err = btrfs_util_set_subvolume_read_only_fd(fd, read_only);
	SAVE_ERRNO_AND_CLOSE(fd);
	return err;
}

PUBLIC enum btrfs_util_error btrfs_util_set_subvolume_read_only_fd(int fd,
								   bool read_only)
{
	uint64_t flags;
	int ret;

	ret = ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_SUBVOL_GETFLAGS_FAILED;

	if (read_only)
		flags |= BTRFS_SUBVOL_RDONLY;
	else
		flags &= ~BTRFS_SUBVOL_RDONLY;

	ret = ioctl(fd, BTRFS_IOC_SUBVOL_SETFLAGS, &flags);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_SUBVOL_SETFLAGS_FAILED;

	return BTRFS_UTIL_OK;
}

static enum btrfs_util_error openat_parent_and_name(int dirfd, const char *path,
						    char *name, size_t name_len,
						    int *fd)
{
	char *tmp_path, *slash, *dirname, *basename;
	size_t len;

	/* Ignore trailing slashes. */
	len = strlen(path);
	while (len > 1 && path[len - 1] == '/')
		len--;

	tmp_path = malloc(len + 1);
	if (!tmp_path)
		return BTRFS_UTIL_ERROR_NO_MEMORY;
	memcpy(tmp_path, path, len);
	tmp_path[len] = '\0';

	slash = memrchr(tmp_path, '/', len);
	if (slash == tmp_path) {
		dirname = "/";
		basename = tmp_path + 1;
	} else if (slash) {
		*slash = '\0';
		dirname = tmp_path;
		basename = slash + 1;
	} else {
		dirname = ".";
		basename = tmp_path;
	}

	len = strlen(basename);
	if (len >= name_len) {
		free(tmp_path);
		errno = ENAMETOOLONG;
		return BTRFS_UTIL_ERROR_INVALID_ARGUMENT;
	}
	memcpy(name, basename, len);
	name[len] = '\0';

	*fd = openat(dirfd, dirname, O_RDONLY | O_DIRECTORY);
	if (*fd == -1) {
		free(tmp_path);
		return BTRFS_UTIL_ERROR_OPEN_FAILED;
	}

	free(tmp_path);
	return BTRFS_UTIL_OK;
}

PUBLIC enum btrfs_util_error btrfs_util_create_subvolume(const char *path,
							 int flags,
							 uint64_t *async_transid,
							 struct btrfs_util_qgroup_inherit *qgroup_inherit)
{
	char name[BTRFS_SUBVOL_NAME_MAX + 1];
	enum btrfs_util_error err;
	int parent_fd;

	err = openat_parent_and_name(AT_FDCWD, path, name, sizeof(name),
				     &parent_fd);
	if (err)
		return err;

	err = btrfs_util_create_subvolume_fd(parent_fd, name, flags,
					    async_transid, qgroup_inherit);
	SAVE_ERRNO_AND_CLOSE(parent_fd);
	return err;
}

PUBLIC enum btrfs_util_error btrfs_util_create_subvolume_fd(int parent_fd,
							    const char *name,
							    int flags,
							    uint64_t *async_transid,
							    struct btrfs_util_qgroup_inherit *qgroup_inherit)
{
	struct btrfs_ioctl_vol_args_v2 args = {};
	size_t len;
	int ret;

	if (flags) {
		errno = EINVAL;
		return BTRFS_UTIL_ERROR_INVALID_ARGUMENT;
	}

	if (async_transid)
		args.flags |= BTRFS_SUBVOL_CREATE_ASYNC;
	if (qgroup_inherit) {
		args.flags |= BTRFS_SUBVOL_QGROUP_INHERIT;
		args.qgroup_inherit = (struct btrfs_qgroup_inherit *)qgroup_inherit;
		args.size = (sizeof(*args.qgroup_inherit) +
			     args.qgroup_inherit->num_qgroups *
			     sizeof(args.qgroup_inherit->qgroups[0]));
	}

	len = strlen(name);
	if (len >= sizeof(args.name)) {
		errno = ENAMETOOLONG;
		return BTRFS_UTIL_ERROR_INVALID_ARGUMENT;
	}
	memcpy(args.name, name, len);
	args.name[len] = '\0';

	ret = ioctl(parent_fd, BTRFS_IOC_SUBVOL_CREATE_V2, &args);
	if (ret == -1)
		return BTRFS_UTIL_ERROR_SUBVOL_CREATE_FAILED;

	if (async_transid)
		*async_transid = args.transid;

	return BTRFS_UTIL_OK;
}