diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
new file mode 100644
index 0000000..6ab8475
--- /dev/null
+++ b/fs/nilfs2/mdt.c
@@ -0,0 +1,562 @@
+/*
+ * mdt.c - meta data file for NILFS
+ *
+ * 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 Ryusuke Konishi <ryusuke@osrg.net>
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/mpage.h>
+#include <linux/mm.h>
+#include <linux/writeback.h>
+#include <linux/backing-dev.h>
+#include <linux/swap.h>
+#include "nilfs.h"
+#include "segment.h"
+#include "page.h"
+#include "mdt.h"
+
+
+#define NILFS_MDT_MAX_RA_BLOCKS		(16 - 1)
+
+#define INIT_UNUSED_INODE_FIELDS
+
+static int
+nilfs_mdt_insert_new_block(struct inode *inode, unsigned long block,
+			   struct buffer_head *bh,
+			   void (*init_block)(struct inode *,
+					      struct buffer_head *, void *))
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	void *kaddr;
+	int ret;
+
+	/* Caller exclude read accesses using page lock */
+
+	/* set_buffer_new(bh); */
+	bh->b_blocknr = 0;
+
+	ret = nilfs_bmap_insert(ii->i_bmap, block, (unsigned long)bh);
+	if (unlikely(ret))
+		return ret;
+
+	set_buffer_mapped(bh);
+
+	kaddr = kmap_atomic(bh->b_page, KM_USER0);
+	memset(kaddr + bh_offset(bh), 0, 1 << inode->i_blkbits);
+	if (init_block)
+		init_block(inode, bh, kaddr);
+	flush_dcache_page(bh->b_page);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	set_buffer_uptodate(bh);
+	nilfs_mark_buffer_dirty(bh);
+	nilfs_mdt_mark_dirty(inode);
+	return 0;
+}
+
+static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
+				  struct buffer_head **out_bh,
+				  void (*init_block)(struct inode *,
+						     struct buffer_head *,
+						     void *))
+{
+	struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs;
+	struct nilfs_sb_info *writer = NULL;
+	struct super_block *sb = inode->i_sb;
+	struct nilfs_transaction_info ti;
+	struct buffer_head *bh;
+	int err;
+
+	if (!sb) {
+		writer = nilfs_get_writer(nilfs);
+		if (!writer) {
+			err = -EROFS;
+			goto out;
+		}
+		sb = writer->s_super;
+	}
+
+	nilfs_transaction_begin(sb, &ti, 0);
+
+	err = -ENOMEM;
+	bh = nilfs_grab_buffer(inode, inode->i_mapping, block, 0);
+	if (unlikely(!bh))
+		goto failed_unlock;
+
+	err = -EEXIST;
+	if (buffer_uptodate(bh) || buffer_mapped(bh))
+		goto failed_bh;
+#if 0
+	/* The uptodate flag is not protected by the page lock, but
+	   the mapped flag is.  Thus, we don't have to wait the buffer. */
+	wait_on_buffer(bh);
+	if (buffer_uptodate(bh))
+		goto failed_bh;
+#endif
+
+	bh->b_bdev = nilfs->ns_bdev;
+	err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
+	if (likely(!err)) {
+		get_bh(bh);
+		*out_bh = bh;
+	}
+
+ failed_bh:
+	unlock_page(bh->b_page);
+	page_cache_release(bh->b_page);
+	brelse(bh);
+
+ failed_unlock:
+	nilfs_transaction_end(sb, !err);
+	if (writer)
+		nilfs_put_writer(nilfs);
+ out:
+	return err;
+}
+
+static int
+nilfs_mdt_submit_block(struct inode *inode, unsigned long blkoff,
+		       int mode, struct buffer_head **out_bh)
+{
+	struct buffer_head *bh;
+	unsigned long blknum = 0;
+	int ret = -ENOMEM;
+
+	bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
+	if (unlikely(!bh))
+		goto failed;
+
+	ret = -EEXIST; /* internal code */
+	if (buffer_uptodate(bh))
+		goto out;
+
+	if (mode == READA) {
+		if (!trylock_buffer(bh)) {
+			ret = -EBUSY;
+			goto failed_bh;
+		}
+	} else {
+		BUG_ON(mode != READ);
+		lock_buffer(bh);
+	}
+
+	if (buffer_uptodate(bh)) {
+		unlock_buffer(bh);
+		goto out;
+	}
+	if (!buffer_mapped(bh)) { /* unused buffer */
+		ret = nilfs_bmap_lookup(NILFS_I(inode)->i_bmap, blkoff,
+					&blknum);
+		if (unlikely(ret)) {
+			unlock_buffer(bh);
+			goto failed_bh;
+		}
+		bh->b_bdev = NILFS_MDT(inode)->mi_nilfs->ns_bdev;
+		bh->b_blocknr = blknum;
+		set_buffer_mapped(bh);
+	}
+
+	bh->b_end_io = end_buffer_read_sync;
+	get_bh(bh);
+	submit_bh(mode, bh);
+	ret = 0;
+ out:
+	get_bh(bh);
+	*out_bh = bh;
+
+ failed_bh:
+	unlock_page(bh->b_page);
+	page_cache_release(bh->b_page);
+	brelse(bh);
+ failed:
+	return ret;
+}
+
+static int nilfs_mdt_read_block(struct inode *inode, unsigned long block,
+				struct buffer_head **out_bh)
+{
+	struct buffer_head *first_bh, *bh;
+	unsigned long blkoff;
+	int i, nr_ra_blocks = NILFS_MDT_MAX_RA_BLOCKS;
+	int err;
+
+	err = nilfs_mdt_submit_block(inode, block, READ, &first_bh);
+	if (err == -EEXIST) /* internal code */
+		goto out;
+
+	if (unlikely(err))
+		goto failed;
+
+	blkoff = block + 1;
+	for (i = 0; i < nr_ra_blocks; i++, blkoff++) {
+		err = nilfs_mdt_submit_block(inode, blkoff, READA, &bh);
+		if (likely(!err || err == -EEXIST))
+			brelse(bh);
+		else if (err != -EBUSY)
+			break; /* abort readahead if bmap lookup failed */
+
+		if (!buffer_locked(first_bh))
+			goto out_no_wait;
+	}
+
+	wait_on_buffer(first_bh);
+
+ out_no_wait:
+	err = -EIO;
+	if (!buffer_uptodate(first_bh))
+		goto failed_bh;
+ out:
+	*out_bh = first_bh;
+	return 0;
+
+ failed_bh:
+	brelse(first_bh);
+ failed:
+	return err;
+}
+
+/**
+ * nilfs_mdt_get_block - read or create a buffer on meta data file.
+ * @inode: inode of the meta data file
+ * @blkoff: block offset
+ * @create: create flag
+ * @init_block: initializer used for newly allocated block
+ * @out_bh: output of a pointer to the buffer_head
+ *
+ * nilfs_mdt_get_block() looks up the specified buffer and tries to create
+ * a new buffer if @create is not zero.  On success, the returned buffer is
+ * assured to be either existing or formatted using a buffer lock on success.
+ * @out_bh is substituted only when zero is returned.
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - the specified block does not exist (hole block)
+ *
+ * %-EINVAL - bmap is broken. (the caller should call nilfs_error())
+ *
+ * %-EROFS - Read only filesystem (for create mode)
+ */
+int nilfs_mdt_get_block(struct inode *inode, unsigned long blkoff, int create,
+			void (*init_block)(struct inode *,
+					   struct buffer_head *, void *),
+			struct buffer_head **out_bh)
+{
+	int ret;
+
+	/* Should be rewritten with merging nilfs_mdt_read_block() */
+ retry:
+	ret = nilfs_mdt_read_block(inode, blkoff, out_bh);
+	if (!create || ret != -ENOENT)
+		return ret;
+
+	ret = nilfs_mdt_create_block(inode, blkoff, out_bh, init_block);
+	if (unlikely(ret == -EEXIST)) {
+		/* create = 0; */  /* limit read-create loop retries */
+		goto retry;
+	}
+	return ret;
+}
+
+/**
+ * nilfs_mdt_delete_block - make a hole on the meta data file.
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * Return Value: On success, zero is returned.
+ * On error, one of the following negative error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-EINVAL - bmap is broken. (the caller should call nilfs_error())
+ */
+int nilfs_mdt_delete_block(struct inode *inode, unsigned long block)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	int err;
+
+	err = nilfs_bmap_delete(ii->i_bmap, block);
+	if (likely(!err)) {
+		nilfs_mdt_mark_dirty(inode);
+		nilfs_mdt_forget_block(inode, block);
+	}
+	return err;
+}
+
+/**
+ * nilfs_mdt_forget_block - discard dirty state and try to remove the page
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * nilfs_mdt_forget_block() clears a dirty flag of the specified buffer, and
+ * tries to release the page including the buffer from a page cache.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error code is returned.
+ *
+ * %-EBUSY - page has an active buffer.
+ *
+ * %-ENOENT - page cache has no page addressed by the offset.
+ */
+int nilfs_mdt_forget_block(struct inode *inode, unsigned long block)
+{
+	pgoff_t index = (pgoff_t)block >>
+		(PAGE_CACHE_SHIFT - inode->i_blkbits);
+	struct page *page;
+	unsigned long first_block;
+	int ret = 0;
+	int still_dirty;
+
+	page = find_lock_page(inode->i_mapping, index);
+	if (!page)
+		return -ENOENT;
+
+	wait_on_page_writeback(page);
+
+	first_block = (unsigned long)index <<
+		(PAGE_CACHE_SHIFT - inode->i_blkbits);
+	if (page_has_buffers(page)) {
+		struct buffer_head *bh;
+
+		bh = nilfs_page_get_nth_block(page, block - first_block);
+		nilfs_forget_buffer(bh);
+	}
+	still_dirty = PageDirty(page);
+	unlock_page(page);
+	page_cache_release(page);
+
+	if (still_dirty ||
+	    invalidate_inode_pages2_range(inode->i_mapping, index, index) != 0)
+		ret = -EBUSY;
+	return ret;
+}
+
+/**
+ * nilfs_mdt_mark_block_dirty - mark a block on the meta data file dirty.
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - the specified block does not exist (hole block)
+ *
+ * %-EINVAL - bmap is broken. (the caller should call nilfs_error())
+ */
+int nilfs_mdt_mark_block_dirty(struct inode *inode, unsigned long block)
+{
+	struct buffer_head *bh;
+	int err;
+
+	err = nilfs_mdt_read_block(inode, block, &bh);
+	if (unlikely(err))
+		return err;
+	nilfs_mark_buffer_dirty(bh);
+	nilfs_mdt_mark_dirty(inode);
+	brelse(bh);
+	return 0;
+}
+
+int nilfs_mdt_fetch_dirty(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+
+	if (nilfs_bmap_test_and_clear_dirty(ii->i_bmap)) {
+		set_bit(NILFS_I_DIRTY, &ii->i_state);
+		return 1;
+	}
+	return test_bit(NILFS_I_DIRTY, &ii->i_state);
+}
+
+static int
+nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
+{
+	struct inode *inode = container_of(page->mapping,
+					   struct inode, i_data);
+	struct super_block *sb = inode->i_sb;
+	struct nilfs_sb_info *writer = NULL;
+	int err = 0;
+
+	redirty_page_for_writepage(wbc, page);
+	unlock_page(page);
+
+	if (page->mapping->assoc_mapping)
+		return 0; /* Do not request flush for shadow page cache */
+	if (!sb) {
+		writer = nilfs_get_writer(NILFS_MDT(inode)->mi_nilfs);
+		if (!writer)
+			return -EROFS;
+		sb = writer->s_super;
+	}
+
+	if (wbc->sync_mode == WB_SYNC_ALL)
+		err = nilfs_construct_segment(sb);
+	else if (wbc->for_reclaim)
+		nilfs_flush_segment(sb, inode->i_ino);
+
+	if (writer)
+		nilfs_put_writer(NILFS_MDT(inode)->mi_nilfs);
+	return err;
+}
+
+
+static struct address_space_operations def_mdt_aops = {
+	.writepage		= nilfs_mdt_write_page,
+};
+
+static struct inode_operations def_mdt_iops;
+static struct file_operations def_mdt_fops;
+
+/*
+ * NILFS2 uses pseudo inodes for meta data files such as DAT, cpfile, sufile,
+ * ifile, or gcinodes.  This allows the B-tree code and segment constructor
+ * to treat them like regular files, and this helps to simplify the
+ * implementation.
+ *   On the other hand, some of the pseudo inodes have an irregular point:
+ * They don't have valid inode->i_sb pointer because their lifetimes are
+ * longer than those of the super block structs; they may continue for
+ * several consecutive mounts/umounts.  This would need discussions.
+ */
+struct inode *
+nilfs_mdt_new_common(struct the_nilfs *nilfs, struct super_block *sb,
+		     ino_t ino, gfp_t gfp_mask)
+{
+	struct inode *inode = nilfs_alloc_inode(sb);
+
+	if (!inode)
+		return NULL;
+	else {
+		struct address_space * const mapping = &inode->i_data;
+		struct nilfs_mdt_info *mi = kzalloc(sizeof(*mi), GFP_NOFS);
+
+		if (!mi) {
+			nilfs_destroy_inode(inode);
+			return NULL;
+		}
+		mi->mi_nilfs = nilfs;
+		init_rwsem(&mi->mi_sem);
+
+		inode->i_sb = sb; /* sb may be NULL for some meta data files */
+		inode->i_blkbits = nilfs->ns_blocksize_bits;
+		inode->i_flags = 0;
+		atomic_set(&inode->i_count, 1);
+		inode->i_nlink = 1;
+		inode->i_ino = ino;
+		inode->i_mode = S_IFREG;
+		inode->i_private = mi;
+
+#ifdef INIT_UNUSED_INODE_FIELDS
+		atomic_set(&inode->i_writecount, 0);
+		inode->i_size = 0;
+		inode->i_blocks = 0;
+		inode->i_bytes = 0;
+		inode->i_generation = 0;
+#ifdef CONFIG_QUOTA
+		memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
+#endif
+		inode->i_pipe = NULL;
+		inode->i_bdev = NULL;
+		inode->i_cdev = NULL;
+		inode->i_rdev = 0;
+#ifdef CONFIG_SECURITY
+		inode->i_security = NULL;
+#endif
+		inode->dirtied_when = 0;
+
+		INIT_LIST_HEAD(&inode->i_list);
+		INIT_LIST_HEAD(&inode->i_sb_list);
+		inode->i_state = 0;
+#endif
+
+		spin_lock_init(&inode->i_lock);
+		mutex_init(&inode->i_mutex);
+		init_rwsem(&inode->i_alloc_sem);
+
+		mapping->host = NULL;  /* instead of inode */
+		mapping->flags = 0;
+		mapping_set_gfp_mask(mapping, gfp_mask);
+		mapping->assoc_mapping = NULL;
+		mapping->backing_dev_info = nilfs->ns_bdi;
+
+		inode->i_mapping = mapping;
+	}
+
+	return inode;
+}
+
+struct inode *nilfs_mdt_new(struct the_nilfs *nilfs, struct super_block *sb,
+			    ino_t ino, gfp_t gfp_mask)
+{
+	struct inode *inode = nilfs_mdt_new_common(nilfs, sb, ino, gfp_mask);
+
+	if (!inode)
+		return NULL;
+
+	inode->i_op = &def_mdt_iops;
+	inode->i_fop = &def_mdt_fops;
+	inode->i_mapping->a_ops = &def_mdt_aops;
+	return inode;
+}
+
+void nilfs_mdt_set_entry_size(struct inode *inode, unsigned entry_size,
+			      unsigned header_size)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+
+	mi->mi_entry_size = entry_size;
+	mi->mi_entries_per_block = (1 << inode->i_blkbits) / entry_size;
+	mi->mi_first_entry_offset = DIV_ROUND_UP(header_size, entry_size);
+}
+
+void nilfs_mdt_set_shadow(struct inode *orig, struct inode *shadow)
+{
+	shadow->i_mapping->assoc_mapping = orig->i_mapping;
+	NILFS_I(shadow)->i_btnode_cache.assoc_mapping =
+		&NILFS_I(orig)->i_btnode_cache;
+}
+
+void nilfs_mdt_clear(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+
+	invalidate_mapping_pages(inode->i_mapping, 0, -1);
+	truncate_inode_pages(inode->i_mapping, 0);
+
+	nilfs_bmap_clear(ii->i_bmap);
+	nilfs_btnode_cache_clear(&ii->i_btnode_cache);
+}
+
+void nilfs_mdt_destroy(struct inode *inode)
+{
+	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
+
+	kfree(mdi->mi_bgl); /* kfree(NULL) is safe */
+	kfree(mdi);
+	nilfs_destroy_inode(inode);
+}