nilfs2: B-tree based block mapping

This adds declarations and functions of NILFS2 B-tree.

Two variants are integrated in the NILFS2 B-tree.  The B-tree for the most
files points to the child nodes or data blocks with virtual block
addresses, whereas the B-tree of the DAT uses actual block addresses.
Signed-off-by: Koji Sato <sato.koji@lab.ntt.co.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/btree.h

+/*
+ * btree.h - NILFS B-tree.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * Written by Koji Sato <koji@osrg.net>.
+ */
+
+#ifndef _NILFS_BTREE_H
+#define _NILFS_BTREE_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/list.h>
+#include <linux/nilfs2_fs.h>
+#include "btnode.h"
+#include "bmap.h"
+
+struct nilfs_btree;
+struct nilfs_btree_path;
+
+/**
+ * struct nilfs_btree_operations - B-tree operation table
+ */
+struct nilfs_btree_operations {
+	__u64 (*btop_find_target)(const struct nilfs_btree *,
+				  const struct nilfs_btree_path *, __u64);
+	void (*btop_set_target)(struct nilfs_btree *, __u64, __u64);
+
+	struct the_nilfs *(*btop_get_nilfs)(struct nilfs_btree *);
+
+	int (*btop_propagate)(struct nilfs_btree *,
+			      struct nilfs_btree_path *,
+			      int,
+			      struct buffer_head *);
+	int (*btop_assign)(struct nilfs_btree *,
+			   struct nilfs_btree_path *,
+			   int,
+			   struct buffer_head **,
+			   sector_t,
+			   union nilfs_binfo *);
+};
+
+/**
+ * struct nilfs_btree_node - B-tree node
+ * @bn_flags: flags
+ * @bn_level: level
+ * @bn_nchildren: number of children
+ * @bn_pad: padding
+ */
+struct nilfs_btree_node {
+	__u8 bn_flags;
+	__u8 bn_level;
+	__le16 bn_nchildren;
+	__le32 bn_pad;
+};
+
+/* flags */
+#define NILFS_BTREE_NODE_ROOT	0x01
+
+/* level */
+#define NILFS_BTREE_LEVEL_DATA		0
+#define NILFS_BTREE_LEVEL_NODE_MIN	(NILFS_BTREE_LEVEL_DATA + 1)
+#define NILFS_BTREE_LEVEL_MAX		14
+
+/**
+ * struct nilfs_btree - B-tree structure
+ * @bt_bmap: bmap base structure
+ * @bt_ops: B-tree operation table
+ */
+struct nilfs_btree {
+	struct nilfs_bmap bt_bmap;
+
+	/* B-tree-specific members */
+	const struct nilfs_btree_operations *bt_ops;
+};
+
+
+#define NILFS_BTREE_ROOT_SIZE		NILFS_BMAP_SIZE
+#define NILFS_BTREE_ROOT_NCHILDREN_MAX					\
+	((NILFS_BTREE_ROOT_SIZE - sizeof(struct nilfs_btree_node)) /	\
+	 (sizeof(__le64 /* dkey */) + sizeof(__le64 /* dptr */)))
+#define NILFS_BTREE_ROOT_NCHILDREN_MIN	0
+#define NILFS_BTREE_NODE_EXTRA_PAD_SIZE	(sizeof(__le64))
+#define NILFS_BTREE_NODE_NCHILDREN_MAX(nodesize)			\
+	(((nodesize) - sizeof(struct nilfs_btree_node) -		\
+		NILFS_BTREE_NODE_EXTRA_PAD_SIZE) /			\
+	 (sizeof(__le64 /* dkey */) + sizeof(__le64 /* dptr */)))
+#define NILFS_BTREE_NODE_NCHILDREN_MIN(nodesize)			\
+	((NILFS_BTREE_NODE_NCHILDREN_MAX(nodesize) - 1) / 2 + 1)
+#define NILFS_BTREE_KEY_MIN	((__u64)0)
+#define NILFS_BTREE_KEY_MAX	(~(__u64)0)
+
+
+int nilfs_btree_path_cache_init(void);
+void nilfs_btree_path_cache_destroy(void);
+int nilfs_btree_init(struct nilfs_bmap *, __u64, __u64);
+int nilfs_btree_convert_and_insert(struct nilfs_bmap *, __u64, __u64,
+				   const __u64 *, const __u64 *,
+				   int, __u64, __u64);
+void nilfs_btree_init_gc(struct nilfs_bmap *);
+
+#endif	/* _NILFS_BTREE_H */