btrfs-progs/btrfs-find-root.c

/*
 * Copyright (C) 2011 Red Hat.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#define _XOPEN_SOURCE 500
#define _GNU_SOURCE 1
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <zlib.h>
#include "kerncompat.h"
#include "ctree.h"
#include "disk-io.h"
#include "print-tree.h"
#include "transaction.h"
#include "list.h"
#include "version.h"
#include "volumes.h"
#include "utils.h"
#include "crc32c.h"

static u16 csum_size = 0;
static u64 search_objectid = BTRFS_ROOT_TREE_OBJECTID;

static void usage()
{
	fprintf(stderr, "Usage: find-roots [-o search_objectid] <device>\n");
}

int csum_block(void *buf, u32 len)
{
	char *result;
	u32 crc = ~(u32)0;
	int ret = 0;

	result = malloc(csum_size * sizeof(char));
	if (!result) {
		fprintf(stderr, "No memory\n");
		return 1;
	}

	len -= BTRFS_CSUM_SIZE;
	crc = crc32c(crc, buf + BTRFS_CSUM_SIZE, len);
	btrfs_csum_final(crc, result);

	if (memcmp(buf, result, csum_size))
		ret = 1;
	free(result);
	return ret;
}

static struct btrfs_root *open_ctree_broken(int fd, const char *device)
{
	struct btrfs_fs_info *fs_info;
	struct btrfs_super_block *disk_super;
	struct btrfs_fs_devices *fs_devices = NULL;
	struct extent_buffer *eb;
	int ret;

	fs_info = btrfs_new_fs_info(0, BTRFS_SUPER_INFO_OFFSET);
	if (!fs_info) {
		fprintf(stderr, "Failed to allocate memory for fs_info\n");
		return NULL;
	}

	ret = btrfs_scan_fs_devices(fd, device, &fs_devices);
	if (ret)
		goto out;

	fs_info->fs_devices = fs_devices;

	ret = btrfs_open_devices(fs_devices, O_RDONLY);
	if (ret)
		goto out_devices;

	disk_super = fs_info->super_copy;
	ret = btrfs_read_dev_super(fs_devices->latest_bdev,
				   disk_super, fs_info->super_bytenr);
	if (ret) {
		printk("No valid btrfs found\n");
		goto out_devices;
	}

	memcpy(fs_info->fsid, &disk_super->fsid, BTRFS_FSID_SIZE);

	ret = btrfs_check_fs_compatibility(disk_super, 0);
	if (ret)
		goto out_devices;

	ret = btrfs_setup_chunk_tree_and_device_map(fs_info);
	if (ret)
		goto out_chunk;

	eb = fs_info->chunk_root->node;
	read_extent_buffer(eb, fs_info->chunk_tree_uuid,
			   (unsigned long)btrfs_header_chunk_tree_uuid(eb),
			   BTRFS_UUID_SIZE);

	return fs_info->chunk_root;
out_chunk:
	free_extent_buffer(fs_info->chunk_root->node);
	btrfs_cleanup_all_caches(fs_info);
out_devices:
	btrfs_close_devices(fs_info->fs_devices);
out:
	btrfs_free_fs_info(fs_info);
	return NULL;
}

static int search_iobuf(struct btrfs_root *root, void *iobuf,
			size_t iobuf_size, off_t offset)
{
	u64 gen = btrfs_super_generation(root->fs_info->super_copy);
	u64 objectid = search_objectid;
	u32 size = btrfs_super_nodesize(root->fs_info->super_copy);
	u8 level = root->fs_info->super_copy->root_level;
	size_t block_off = 0;

	while (block_off < iobuf_size) {
		void *block = iobuf + block_off;
		struct btrfs_header *header = block;
		u64 h_byte, h_level, h_gen, h_owner;

//		printf("searching %Lu\n", offset + block_off);
		h_byte = le64_to_cpu(header->bytenr);
		h_owner = le64_to_cpu(header->owner);
		h_level = header->level;
		h_gen = le64_to_cpu(header->generation);

		if (h_owner != objectid)
			goto next;
		if (h_byte != (offset + block_off))
			goto next;
		if (h_level != level)
			goto next;
		if (csum_block(block, size)) {
			fprintf(stderr, "Well block %Lu seems good, "
				"but the csum doesn't match\n",
				h_byte);
			goto next;
		}
		if (h_gen != gen) {
			fprintf(stderr, "Well block %Lu seems great, "
				"but generation doesn't match, "
				"have=%Lu, want=%Lu\n", h_byte, h_gen,
				gen);
			goto next;
		}
		printf("Found tree root at %Lu\n", h_byte);
		return 0;
next:
		block_off += size;
	}

	return 1;
}

static int read_physical(struct btrfs_root *root, int fd, u64 offset,
			 u64 bytenr, u64 len)
{
	char *iobuf = malloc(len);
	ssize_t done;
	size_t total_read = 0;
	int ret = 1;

	if (!iobuf) {
		fprintf(stderr, "No memory\n");
		return -1;
	}

	while (total_read < len) {
		done = pread64(fd, iobuf + total_read, len - total_read,
			       bytenr + total_read);
		if (done < 0) {
			fprintf(stderr, "Failed to read: %s\n",
				strerror(errno));
			ret = -1;
			goto out;
		}
		total_read += done;
	}

	ret = search_iobuf(root, iobuf, total_read, offset);
out:
	free(iobuf);
	return ret;
}

static int find_root(struct btrfs_root *root)
{
	struct btrfs_multi_bio *multi = NULL;
	struct btrfs_device *device;
	u64 metadata_offset = 0, metadata_size = 0;
	off_t offset = 0;
	off_t bytenr;
	int fd;
	int err;
	int ret = 1;

	printf("Super think's the tree root is at %Lu, chunk root %Lu\n",
	       btrfs_super_root(root->fs_info->super_copy),
	       btrfs_super_chunk_root(root->fs_info->super_copy));

	err = btrfs_next_metadata(&root->fs_info->mapping_tree,
				  &metadata_offset, &metadata_size);
	if (err)
		return ret;

	offset = metadata_offset;
	while (1) {
		u64 map_length = 4096;
		u64 type;

		if (offset >
		    btrfs_super_total_bytes(root->fs_info->super_copy)) {
			printf("Went past the fs size, exiting");
			break;
		}
		if (offset >= (metadata_offset + metadata_size)) {
			err = btrfs_next_metadata(&root->fs_info->mapping_tree,
						  &metadata_offset,
						  &metadata_size);
			if (err) {
				printf("No more metdata to scan, exiting\n");
				break;
			}
			offset = metadata_offset;
		}
		err = __btrfs_map_block(&root->fs_info->mapping_tree, READ,
				      offset, &map_length, &type,
				      &multi, 0, NULL);
		if (err) {
			offset += map_length;
			continue;
		}

		if (!(type & BTRFS_BLOCK_GROUP_METADATA)) {
			offset += map_length;
			kfree(multi);
			continue;
		}

		device = multi->stripes[0].dev;
		fd = device->fd;
		bytenr = multi->stripes[0].physical;
		kfree(multi);

		err = read_physical(root, fd, offset, bytenr, map_length);
		if (!err) {
			ret = 0;
			break;
		} else if (err < 0) {
			ret = err;
			break;
		}
		offset += map_length;
	}
	return ret;
}

int main(int argc, char **argv)
{
	struct btrfs_root *root;
	int dev_fd;
	int opt;
	int ret;

	while ((opt = getopt(argc, argv, "o:")) != -1) {
		switch(opt) {
			case 'o':
				errno = 0;
				search_objectid = (u64)strtoll(optarg, NULL,
							       10);
				if (errno) {
					fprintf(stderr, "Error parsing "
						"objectid\n");
					exit(1);
				}
				break;
			default:
				usage();
				exit(1);
		}
	}

	if (optind >= argc) {
		usage();
		exit(1);
	}

	dev_fd = open(argv[optind], O_RDONLY);
	if (dev_fd < 0) {
		fprintf(stderr, "Failed to open device %s\n", argv[optind]);
		exit(1);
	}

	root = open_ctree_broken(dev_fd, argv[optind]);
	close(dev_fd);

	if (!root) {
		fprintf(stderr, "Open ctree failed\n");
		exit(1);
	}

	csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
	ret = find_root(root);
	close_ctree(root);
	return ret;
}