diff --git a/fs/nilfs2/dat.c b/fs/nilfs2/dat.c
new file mode 100644
index 000000000000..9360920f7d38
--- /dev/null
+++ b/fs/nilfs2/dat.c
@@ -0,0 +1,429 @@
+/*
+ * dat.c - NILFS disk address translation.
+ *
+ * Copyright (C) 2006-2008 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>.
+ */
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include "nilfs.h"
+#include "mdt.h"
+#include "alloc.h"
+#include "dat.h"
+
+
+#define NILFS_CNO_MIN	((__u64)1)
+#define NILFS_CNO_MAX	(~(__u64)0)
+
+static int nilfs_dat_prepare_entry(struct inode *dat,
+				   struct nilfs_palloc_req *req, int create)
+{
+	return nilfs_palloc_get_entry_block(dat, req->pr_entry_nr,
+					    create, &req->pr_entry_bh);
+}
+
+static void nilfs_dat_commit_entry(struct inode *dat,
+				   struct nilfs_palloc_req *req)
+{
+	nilfs_mdt_mark_buffer_dirty(req->pr_entry_bh);
+	nilfs_mdt_mark_dirty(dat);
+	brelse(req->pr_entry_bh);
+}
+
+static void nilfs_dat_abort_entry(struct inode *dat,
+				  struct nilfs_palloc_req *req)
+{
+	brelse(req->pr_entry_bh);
+}
+
+int nilfs_dat_prepare_alloc(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	int ret;
+
+	ret = nilfs_palloc_prepare_alloc_entry(dat, req);
+	if (ret < 0)
+		return ret;
+
+	ret = nilfs_dat_prepare_entry(dat, req, 1);
+	if (ret < 0)
+		nilfs_palloc_abort_alloc_entry(dat, req);
+
+	return ret;
+}
+
+void nilfs_dat_commit_alloc(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
+	entry->de_end = cpu_to_le64(NILFS_CNO_MAX);
+	entry->de_blocknr = cpu_to_le64(0);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	nilfs_palloc_commit_alloc_entry(dat, req);
+	nilfs_dat_commit_entry(dat, req);
+}
+
+void nilfs_dat_abort_alloc(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	nilfs_dat_abort_entry(dat, req);
+	nilfs_palloc_abort_alloc_entry(dat, req);
+}
+
+int nilfs_dat_prepare_free(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	int ret;
+
+	ret = nilfs_palloc_prepare_free_entry(dat, req);
+	if (ret < 0)
+		return ret;
+	ret = nilfs_dat_prepare_entry(dat, req, 0);
+	if (ret < 0) {
+		nilfs_palloc_abort_free_entry(dat, req);
+		return ret;
+	}
+	return 0;
+}
+
+void nilfs_dat_commit_free(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
+	entry->de_end = cpu_to_le64(NILFS_CNO_MIN);
+	entry->de_blocknr = cpu_to_le64(0);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	nilfs_dat_commit_entry(dat, req);
+	nilfs_palloc_commit_free_entry(dat, req);
+}
+
+void nilfs_dat_abort_free(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	nilfs_dat_abort_entry(dat, req);
+	nilfs_palloc_abort_free_entry(dat, req);
+}
+
+int nilfs_dat_prepare_start(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	int ret;
+
+	ret = nilfs_dat_prepare_entry(dat, req, 0);
+	BUG_ON(ret == -ENOENT);
+	return ret;
+}
+
+void nilfs_dat_commit_start(struct inode *dat, struct nilfs_palloc_req *req,
+			    sector_t blocknr)
+{
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	entry->de_start = cpu_to_le64(nilfs_mdt_cno(dat));
+	if (entry->de_blocknr != cpu_to_le64(0) ||
+	    entry->de_end != cpu_to_le64(NILFS_CNO_MAX)) {
+		printk(KERN_CRIT
+		       "%s: vbn = %llu, start = %llu, end = %llu, pbn = %llu\n",
+		       __func__, (unsigned long long)req->pr_entry_nr,
+		       (unsigned long long)le64_to_cpu(entry->de_start),
+		       (unsigned long long)le64_to_cpu(entry->de_end),
+		       (unsigned long long)le64_to_cpu(entry->de_blocknr));
+		BUG();
+	}
+	entry->de_blocknr = cpu_to_le64(blocknr);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	nilfs_dat_commit_entry(dat, req);
+}
+
+void nilfs_dat_abort_start(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	nilfs_dat_abort_entry(dat, req);
+}
+
+int nilfs_dat_prepare_end(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	__u64 start;
+	sector_t blocknr;
+	void *kaddr;
+	int ret;
+
+	ret = nilfs_dat_prepare_entry(dat, req, 0);
+	if (ret < 0) {
+		BUG_ON(ret == -ENOENT);
+		return ret;
+	}
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	start = le64_to_cpu(entry->de_start);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	if (blocknr == 0) {
+		ret = nilfs_palloc_prepare_free_entry(dat, req);
+		if (ret < 0) {
+			nilfs_dat_abort_entry(dat, req);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+void nilfs_dat_commit_end(struct inode *dat, struct nilfs_palloc_req *req,
+			  int dead)
+{
+	struct nilfs_dat_entry *entry;
+	__u64 start, end;
+	sector_t blocknr;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	end = start = le64_to_cpu(entry->de_start);
+	if (!dead) {
+		end = nilfs_mdt_cno(dat);
+		BUG_ON(start > end);
+	}
+	entry->de_end = cpu_to_le64(end);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	if (blocknr == 0)
+		nilfs_dat_commit_free(dat, req);
+	else
+		nilfs_dat_commit_entry(dat, req);
+}
+
+void nilfs_dat_abort_end(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	__u64 start;
+	sector_t blocknr;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	start = le64_to_cpu(entry->de_start);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	if (start == nilfs_mdt_cno(dat) && blocknr == 0)
+		nilfs_palloc_abort_free_entry(dat, req);
+	nilfs_dat_abort_entry(dat, req);
+}
+
+/**
+ * nilfs_dat_mark_dirty -
+ * @dat: DAT file inode
+ * @vblocknr: virtual block number
+ *
+ * Description:
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_dat_mark_dirty(struct inode *dat, __u64 vblocknr)
+{
+	struct nilfs_palloc_req req;
+	int ret;
+
+	req.pr_entry_nr = vblocknr;
+	ret = nilfs_dat_prepare_entry(dat, &req, 0);
+	if (ret == 0)
+		nilfs_dat_commit_entry(dat, &req);
+	return ret;
+}
+
+/**
+ * nilfs_dat_freev - free virtual block numbers
+ * @dat: DAT file inode
+ * @vblocknrs: array of virtual block numbers
+ * @nitems: number of virtual block numbers
+ *
+ * Description: nilfs_dat_freev() frees the virtual block numbers specified by
+ * @vblocknrs and @nitems.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * nagative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - The virtual block number have not been allocated.
+ */
+int nilfs_dat_freev(struct inode *dat, __u64 *vblocknrs, size_t nitems)
+{
+	return nilfs_palloc_freev(dat, vblocknrs, nitems);
+}
+
+/**
+ * nilfs_dat_move - change a block number
+ * @dat: DAT file inode
+ * @vblocknr: virtual block number
+ * @blocknr: block number
+ *
+ * Description: nilfs_dat_move() changes the block number associated with
+ * @vblocknr to @blocknr.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_dat_move(struct inode *dat, __u64 vblocknr, sector_t blocknr)
+{
+	struct buffer_head *entry_bh;
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+	int ret;
+
+	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
+	if (ret < 0)
+		return ret;
+	kaddr = kmap_atomic(entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
+	if (entry->de_blocknr == cpu_to_le64(0)) {
+		printk(KERN_CRIT "%s: vbn = %llu, [%llu, %llu)\n", __func__,
+		       (unsigned long long)vblocknr,
+		       (unsigned long long)le64_to_cpu(entry->de_start),
+		       (unsigned long long)le64_to_cpu(entry->de_end));
+		BUG();
+	}
+	BUG_ON(blocknr == 0);
+	entry->de_blocknr = cpu_to_le64(blocknr);
+	kunmap_atomic(kaddr, KM_USER0);
+
+	nilfs_mdt_mark_buffer_dirty(entry_bh);
+	nilfs_mdt_mark_dirty(dat);
+
+	brelse(entry_bh);
+
+	return 0;
+}
+
+/**
+ * nilfs_dat_translate - translate a virtual block number to a block number
+ * @dat: DAT file inode
+ * @vblocknr: virtual block number
+ * @blocknrp: pointer to a block number
+ *
+ * Description: nilfs_dat_translate() maps the virtual block number @vblocknr
+ * to the corresponding block number.
+ *
+ * Return Value: On success, 0 is returned and the block number associated
+ * with @vblocknr is stored in the place pointed by @blocknrp. On error, one
+ * of the following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - A block number associated with @vblocknr does not exist.
+ */
+int nilfs_dat_translate(struct inode *dat, __u64 vblocknr, sector_t *blocknrp)
+{
+	struct buffer_head *entry_bh;
+	struct nilfs_dat_entry *entry;
+	sector_t blocknr;
+	void *kaddr;
+	int ret;
+
+	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
+	if (ret < 0)
+		return ret;
+
+	kaddr = kmap_atomic(entry_bh->b_page, KM_USER0);
+	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	if (blocknr == 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+	if (blocknrp != NULL)
+		*blocknrp = blocknr;
+
+ out:
+	kunmap_atomic(kaddr, KM_USER0);
+	brelse(entry_bh);
+	return ret;
+}
+
+ssize_t nilfs_dat_get_vinfo(struct inode *dat, struct nilfs_vinfo *vinfo,
+			    size_t nvi)
+{
+	struct buffer_head *entry_bh;
+	struct nilfs_dat_entry *entry;
+	__u64 first, last;
+	void *kaddr;
+	unsigned long entries_per_block = NILFS_MDT(dat)->mi_entries_per_block;
+	int i, j, n, ret;
+
+	for (i = 0; i < nvi; i += n) {
+		ret = nilfs_palloc_get_entry_block(dat, vinfo[i].vi_vblocknr,
+						   0, &entry_bh);
+		if (ret < 0)
+			return ret;
+		kaddr = kmap_atomic(entry_bh->b_page, KM_USER0);
+		/* last virtual block number in this block */
+		first = vinfo[i].vi_vblocknr;
+		do_div(first, entries_per_block);
+		first *= entries_per_block;
+		last = first + entries_per_block - 1;
+		for (j = i, n = 0;
+		     j < nvi && vinfo[j].vi_vblocknr >= first &&
+			     vinfo[j].vi_vblocknr <= last;
+		     j++, n++) {
+			entry = nilfs_palloc_block_get_entry(
+				dat, vinfo[j].vi_vblocknr, entry_bh, kaddr);
+			vinfo[j].vi_start = le64_to_cpu(entry->de_start);
+			vinfo[j].vi_end = le64_to_cpu(entry->de_end);
+			vinfo[j].vi_blocknr = le64_to_cpu(entry->de_blocknr);
+		}
+		kunmap_atomic(kaddr, KM_USER0);
+		brelse(entry_bh);
+	}
+
+	return nvi;
+}
diff --git a/fs/nilfs2/dat.h b/fs/nilfs2/dat.h
new file mode 100644
index 000000000000..d9560654a4b7
--- /dev/null
+++ b/fs/nilfs2/dat.h
@@ -0,0 +1,52 @@
+/*
+ * dat.h - NILFS disk address translation.
+ *
+ * Copyright (C) 2006-2008 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_DAT_H
+#define _NILFS_DAT_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+
+#define NILFS_DAT_GFP	NILFS_MDT_GFP
+
+struct nilfs_palloc_req;
+
+int nilfs_dat_translate(struct inode *, __u64, sector_t *);
+
+int nilfs_dat_prepare_alloc(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_commit_alloc(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_abort_alloc(struct inode *, struct nilfs_palloc_req *);
+int nilfs_dat_prepare_start(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_commit_start(struct inode *, struct nilfs_palloc_req *,
+			    sector_t);
+void nilfs_dat_abort_start(struct inode *, struct nilfs_palloc_req *);
+int nilfs_dat_prepare_end(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_commit_end(struct inode *, struct nilfs_palloc_req *, int);
+void nilfs_dat_abort_end(struct inode *, struct nilfs_palloc_req *);
+
+int nilfs_dat_mark_dirty(struct inode *, __u64);
+int nilfs_dat_freev(struct inode *, __u64 *, size_t);
+int nilfs_dat_move(struct inode *, __u64, sector_t);
+ssize_t nilfs_dat_get_vinfo(struct inode *, struct nilfs_vinfo *, size_t);
+
+#endif	/* _NILFS_DAT_H */