Btrfs: add mkfs.c

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/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)
+{
+	struct ctree_root_info info[2];
+	struct leaf empty_leaf;
+	struct item item;
+	struct extent_item extent_item;
+	int ret;
+
+	memset(info, 0, sizeof(info));
+	info[0].blocknr = 16;
+	info[0].objectid = 1;
+	info[0].tree_root = 17;
+	info[0].alloc_extent.blocknr = 0;
+	info[0].alloc_extent.num_blocks = 20;
+	/* 0-17 are used (inclusive) */
+	info[0].alloc_extent.num_used = 18;
+
+	info[1].blocknr = 16;
+	info[1].objectid = 2;
+	info[1].tree_root = 64;
+	info[1].alloc_extent.blocknr = 64;
+	info[1].alloc_extent.num_blocks = 8;
+	info[1].alloc_extent.num_used = 1;
+	ret = pwrite(fd, info, sizeof(info),
+		     CTREE_SUPER_INFO_OFFSET(CTREE_BLOCKSIZE));
+	if (ret != sizeof(info))
+		return -1;
+	memset(&empty_leaf, 0, sizeof(empty_leaf));
+	empty_leaf.header.parentid = 1;
+	empty_leaf.header.blocknr = 17;
+	ret = pwrite(fd, &empty_leaf, sizeof(empty_leaf), 17 * CTREE_BLOCKSIZE);
+	if (ret != sizeof(empty_leaf))
+		return -1;
+
+	empty_leaf.header.parentid = 2;
+	empty_leaf.header.blocknr = 64;
+	empty_leaf.header.nritems = 2;
+	item.key.objectid = 0;
+	item.key.offset = 64;
+	item.key.flags = 0;
+	item.offset = LEAF_DATA_SIZE - sizeof(struct extent_item);
+	item.size = sizeof(struct extent_item);
+	extent_item.refs = 1;
+	extent_item.owner = 1;
+	memcpy(empty_leaf.items, &item, sizeof(item));
+	memcpy(empty_leaf.data + item.offset, &extent_item, item.size);
+	item.key.objectid = 64;
+	item.key.offset = 64;
+	item.offset = LEAF_DATA_SIZE - sizeof(struct extent_item) * 2;
+	extent_item.owner = 2;
+	memcpy(empty_leaf.items + 1, &item, sizeof(item));
+	memcpy(empty_leaf.data + item.offset, &extent_item, item.size);
+	ret = pwrite(fd, &empty_leaf, sizeof(empty_leaf), 64 * CTREE_BLOCKSIZE);
+	if (ret != sizeof(empty_leaf))
+		return -1;
+	return 0;
+}