btrfs-progs/mkfs.c

#define _XOPEN_SOURCE 500
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include "kerncompat.h"
#include "radix-tree.h"
#include "ctree.h"
#include "disk-io.h"

int mkfs(int fd, u64 num_blocks, u16 blocksize)
{
	struct btrfs_super_block super;
	struct btrfs_leaf empty_leaf;
	struct btrfs_root_item root_item;
	struct btrfs_item item;
	struct btrfs_extent_item extent_item;
	char *block;
	int ret;
	u16 itemoff;

	btrfs_set_super_blocknr(&super, 16);
	btrfs_set_super_root(&super, 17);
	strcpy((char *)(&super.magic), BTRFS_MAGIC);
	btrfs_set_super_blocksize(&super, blocksize);
	btrfs_set_super_total_blocks(&super, num_blocks);
	btrfs_set_super_blocks_used(&super, 0);

	block = malloc(blocksize);
	memset(block, 0, blocksize);
	BUG_ON(sizeof(super) > blocksize);
	memcpy(block, &super, sizeof(super));
	ret = pwrite(fd, block, blocksize, BTRFS_SUPER_INFO_OFFSET(blocksize));
	BUG_ON(ret != blocksize);

	/* create the tree of root objects */
	memset(&empty_leaf, 0, sizeof(empty_leaf));
	btrfs_set_header_parentid(&empty_leaf.header, BTRFS_ROOT_TREE_OBJECTID);
	btrfs_set_header_blocknr(&empty_leaf.header, 17);
	btrfs_set_header_nritems(&empty_leaf.header, 2);

	/* create the items for the root tree */
	btrfs_set_root_blocknr(&root_item, 18);
	btrfs_set_root_refs(&root_item, 1);
	itemoff = LEAF_DATA_SIZE - sizeof(root_item);
	btrfs_set_item_offset(&item, itemoff);
	btrfs_set_item_size(&item, sizeof(root_item));
	btrfs_set_key_objectid(&item.key, BTRFS_EXTENT_TREE_OBJECTID);
	btrfs_set_key_offset(&item.key, 0);
	btrfs_set_key_flags(&item.key, 0);
	memcpy(empty_leaf.items, &item, sizeof(item));
	memcpy(empty_leaf.data + itemoff, &root_item, sizeof(root_item));

	btrfs_set_root_blocknr(&root_item, 19);
	itemoff = itemoff - sizeof(root_item);
	btrfs_set_item_offset(&item, itemoff);
	btrfs_set_key_objectid(&item.key, BTRFS_FS_TREE_OBJECTID);
	memcpy(empty_leaf.items + 1, &item, sizeof(item));
	memcpy(empty_leaf.data + itemoff, &root_item, sizeof(root_item));
	ret = pwrite(fd, &empty_leaf, blocksize, 17 * blocksize);

	/* create the items for the extent tree */
	btrfs_set_header_parentid(&empty_leaf.header,
				  BTRFS_EXTENT_TREE_OBJECTID);
	btrfs_set_header_blocknr(&empty_leaf.header, 18);
	btrfs_set_header_nritems(&empty_leaf.header, 4);

	/* item1, reserve blocks 0-16 */
	btrfs_set_key_objectid(&item.key, 0);
	btrfs_set_key_offset(&item.key, 17);
	btrfs_set_key_flags(&item.key, 0);
	itemoff = LEAF_DATA_SIZE - sizeof(struct btrfs_extent_item);
	btrfs_set_item_offset(&item, itemoff);
	btrfs_set_item_size(&item, sizeof(struct btrfs_extent_item));
	btrfs_set_extent_refs(&extent_item, 1);
	btrfs_set_extent_owner(&extent_item, 0);
	memcpy(empty_leaf.items, &item, sizeof(item));
	memcpy(empty_leaf.data + btrfs_item_offset(&item), &extent_item,
		btrfs_item_size(&item));

	/* item2, give block 17 to the root */
	btrfs_set_key_objectid(&item.key, 17);
	btrfs_set_key_offset(&item.key, 1);
	itemoff = itemoff - sizeof(struct btrfs_extent_item);
	btrfs_set_item_offset(&item, itemoff);
	btrfs_set_extent_owner(&extent_item, BTRFS_ROOT_TREE_OBJECTID);
	memcpy(empty_leaf.items + 1, &item, sizeof(item));
	memcpy(empty_leaf.data + btrfs_item_offset(&item), &extent_item,
		btrfs_item_size(&item));

	/* item3, give block 18 to the extent root */
	btrfs_set_key_objectid(&item.key, 18);
	btrfs_set_key_offset(&item.key, 1);
	itemoff = itemoff - sizeof(struct btrfs_extent_item);
	btrfs_set_item_offset(&item, itemoff);
	btrfs_set_extent_owner(&extent_item, BTRFS_EXTENT_TREE_OBJECTID);
	memcpy(empty_leaf.items + 2, &item, sizeof(item));
	memcpy(empty_leaf.data + btrfs_item_offset(&item), &extent_item,
		btrfs_item_size(&item));

	/* item4, give block 19 to the FS root */
	btrfs_set_key_objectid(&item.key, 19);
	btrfs_set_key_offset(&item.key, 1);
	itemoff = itemoff - sizeof(struct btrfs_extent_item);
	btrfs_set_item_offset(&item, itemoff);
	btrfs_set_extent_owner(&extent_item, BTRFS_FS_TREE_OBJECTID);
	memcpy(empty_leaf.items + 3, &item, sizeof(item));
	memcpy(empty_leaf.data + btrfs_item_offset(&item), &extent_item,
		btrfs_item_size(&item));
	ret = pwrite(fd, &empty_leaf, blocksize, 18 * blocksize);
	if (ret != sizeof(empty_leaf))
		return -1;

	/* finally create the FS root */
	btrfs_set_header_parentid(&empty_leaf.header, BTRFS_FS_TREE_OBJECTID);
	btrfs_set_header_blocknr(&empty_leaf.header, 19);
	btrfs_set_header_nritems(&empty_leaf.header, 0);
	ret = pwrite(fd, &empty_leaf, blocksize, 19 * blocksize);
	if (ret != sizeof(empty_leaf))
		return -1;
	return 0;
}

#if 0
int mkfs(int fd)
{
	struct btrfs_root_info info[2];
	struct btrfs_leaf empty_leaf;
	struct btrfs_item item;
	struct btrfs_extent_item extent_item;
	int ret;

	/* setup the super block area */
	memset(info, 0, sizeof(info));
	btrfs_set_root_blocknr(info, 16);
	btrfs_set_root_objectid(info, 1);
	btrfs_set_root_tree_root(info, 17);

	btrfs_set_root_blocknr(info + 1, 16);
	btrfs_set_root_objectid(info + 1, 2);
	btrfs_set_root_tree_root(info + 1, 18);

	ret = pwrite(fd, info, sizeof(info),
		     BTRFS_SUPER_INFO_OFFSET(BTRFS_BLOCKSIZE));
	if (ret != sizeof(info))
		return -1;

	/* create leaves for the tree root and extent root */
	memset(&empty_leaf, 0, sizeof(empty_leaf));
	btrfs_set_header_parentid(&empty_leaf.header, 1);
	btrfs_set_header_blocknr(&empty_leaf.header, 17);
	ret = pwrite(fd, &empty_leaf, sizeof(empty_leaf), 17 * BTRFS_BLOCKSIZE);
	if (ret != sizeof(empty_leaf))
		return -1;

	btrfs_set_header_parentid(&empty_leaf.header, 2);
	btrfs_set_header_blocknr(&empty_leaf.header, 18);
	btrfs_set_header_nritems(&empty_leaf.header, 3);

	/* item1, reserve blocks 0-16 */
	btrfs_set_key_objectid(&item.key, 0);
	btrfs_set_key_offset(&item.key, 17);
	btrfs_set_key_flags(&item.key, 0);
	btrfs_set_item_offset(&item, LEAF_DATA_SIZE -
			      sizeof(struct btrfs_extent_item));
	btrfs_set_item_size(&item, sizeof(struct btrfs_extent_item));
	btrfs_set_extent_refs(&extent_item, 1);
	btrfs_set_extent_owner(&extent_item, 0);
	memcpy(empty_leaf.items, &item, sizeof(item));
	memcpy(empty_leaf.data + btrfs_item_offset(&item), &extent_item,
		btrfs_item_size(&item));

	/* item2, give block 17 to the root */
	btrfs_set_key_objectid(&item.key, 17);
	btrfs_set_key_offset(&item.key, 1);
	btrfs_set_item_offset(&item, LEAF_DATA_SIZE -
			      sizeof(struct btrfs_extent_item) * 2);
	btrfs_set_extent_owner(&extent_item, 1);
	memcpy(empty_leaf.items + 1, &item, sizeof(item));
	memcpy(empty_leaf.data + btrfs_item_offset(&item), &extent_item,
		btrfs_item_size(&item));

	/* item3, give block 18 for the extent root */
	btrfs_set_key_objectid(&item.key, 18);
	btrfs_set_key_offset(&item.key, 1);
	btrfs_set_item_offset(&item, LEAF_DATA_SIZE -
			      sizeof(struct btrfs_extent_item) * 3);
	btrfs_set_extent_owner(&extent_item, 2);
	memcpy(empty_leaf.items + 2, &item, sizeof(item));
	memcpy(empty_leaf.data + btrfs_item_offset(&item), &extent_item,
		btrfs_item_size(&item));
	ret = pwrite(fd, &empty_leaf, sizeof(empty_leaf), 18 * BTRFS_BLOCKSIZE);
	if (ret != sizeof(empty_leaf))
		return -1;
	return 0;
}
#endif