diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
new file mode 100644
index 0000000..4cc07b2
--- /dev/null
+++ b/fs/nilfs2/btnode.c
@@ -0,0 +1,316 @@
+/*
+ * btnode.c - NILFS B-tree node cache
+ *
+ * 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
+ *
+ * This file was originally written by Seiji Kihara <kihara@osrg.net>
+ * and fully revised by Ryusuke Konishi <ryusuke@osrg.net> for
+ * stabilization and simplification.
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/mm.h>
+#include <linux/backing-dev.h>
+#include "nilfs.h"
+#include "mdt.h"
+#include "dat.h"
+#include "page.h"
+#include "btnode.h"
+
+
+void nilfs_btnode_cache_init_once(struct address_space *btnc)
+{
+	INIT_RADIX_TREE(&btnc->page_tree, GFP_ATOMIC);
+	spin_lock_init(&btnc->tree_lock);
+	INIT_LIST_HEAD(&btnc->private_list);
+	spin_lock_init(&btnc->private_lock);
+
+	spin_lock_init(&btnc->i_mmap_lock);
+	INIT_RAW_PRIO_TREE_ROOT(&btnc->i_mmap);
+	INIT_LIST_HEAD(&btnc->i_mmap_nonlinear);
+}
+
+static struct address_space_operations def_btnode_aops;
+
+void nilfs_btnode_cache_init(struct address_space *btnc)
+{
+	btnc->host = NULL;  /* can safely set to host inode ? */
+	btnc->flags = 0;
+	mapping_set_gfp_mask(btnc, GFP_NOFS);
+	btnc->assoc_mapping = NULL;
+	btnc->backing_dev_info = &default_backing_dev_info;
+	btnc->a_ops = &def_btnode_aops;
+}
+
+void nilfs_btnode_cache_clear(struct address_space *btnc)
+{
+	invalidate_mapping_pages(btnc, 0, -1);
+	truncate_inode_pages(btnc, 0);
+}
+
+int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
+			      sector_t pblocknr, struct buffer_head **pbh,
+			      int newblk)
+{
+	struct buffer_head *bh;
+	struct inode *inode = NILFS_BTNC_I(btnc);
+	int err;
+
+	bh = nilfs_grab_buffer(inode, btnc, blocknr, 1 << BH_NILFS_Node);
+	if (unlikely(!bh))
+		return -ENOMEM;
+
+	err = -EEXIST; /* internal code */
+	if (newblk) {
+		if (unlikely(buffer_mapped(bh) || buffer_uptodate(bh) ||
+			     buffer_dirty(bh))) {
+			brelse(bh);
+			BUG();
+		}
+		bh->b_bdev = NILFS_I_NILFS(inode)->ns_bdev;
+		bh->b_blocknr = blocknr;
+		set_buffer_mapped(bh);
+		set_buffer_uptodate(bh);
+		goto found;
+	}
+
+	if (buffer_uptodate(bh) || buffer_dirty(bh))
+		goto found;
+
+	if (pblocknr == 0) {
+		pblocknr = blocknr;
+		if (inode->i_ino != NILFS_DAT_INO) {
+			struct inode *dat =
+				nilfs_dat_inode(NILFS_I_NILFS(inode));
+
+			/* blocknr is a virtual block number */
+			err = nilfs_dat_translate(dat, blocknr, &pblocknr);
+			if (unlikely(err)) {
+				brelse(bh);
+				goto out_locked;
+			}
+		}
+	}
+	lock_buffer(bh);
+	if (buffer_uptodate(bh)) {
+		unlock_buffer(bh);
+		err = -EEXIST; /* internal code */
+		goto found;
+	}
+	set_buffer_mapped(bh);
+	bh->b_bdev = NILFS_I_NILFS(inode)->ns_bdev;
+	bh->b_blocknr = pblocknr; /* set block address for read */
+	bh->b_end_io = end_buffer_read_sync;
+	get_bh(bh);
+	submit_bh(READ, bh);
+	bh->b_blocknr = blocknr; /* set back to the given block address */
+	err = 0;
+found:
+	*pbh = bh;
+
+out_locked:
+	unlock_page(bh->b_page);
+	page_cache_release(bh->b_page);
+	return err;
+}
+
+int nilfs_btnode_get(struct address_space *btnc, __u64 blocknr,
+		     sector_t pblocknr, struct buffer_head **pbh, int newblk)
+{
+	struct buffer_head *bh;
+	int err;
+
+	err = nilfs_btnode_submit_block(btnc, blocknr, pblocknr, pbh, newblk);
+	if (err == -EEXIST) /* internal code (cache hit) */
+		return 0;
+	if (unlikely(err))
+		return err;
+
+	bh = *pbh;
+	wait_on_buffer(bh);
+	if (!buffer_uptodate(bh)) {
+		brelse(bh);
+		return -EIO;
+	}
+	return 0;
+}
+
+/**
+ * nilfs_btnode_delete - delete B-tree node buffer
+ * @bh: buffer to be deleted
+ *
+ * nilfs_btnode_delete() invalidates the specified buffer and delete the page
+ * including the buffer if the page gets unbusy.
+ */
+void nilfs_btnode_delete(struct buffer_head *bh)
+{
+	struct address_space *mapping;
+	struct page *page = bh->b_page;
+	pgoff_t index = page_index(page);
+	int still_dirty;
+
+	page_cache_get(page);
+	lock_page(page);
+	wait_on_page_writeback(page);
+
+	nilfs_forget_buffer(bh);
+	still_dirty = PageDirty(page);
+	mapping = page->mapping;
+	unlock_page(page);
+	page_cache_release(page);
+
+	if (!still_dirty && mapping)
+		invalidate_inode_pages2_range(mapping, index, index);
+}
+
+/**
+ * nilfs_btnode_prepare_change_key
+ *  prepare to move contents of the block for old key to one of new key.
+ *  the old buffer will not be removed, but might be reused for new buffer.
+ *  it might return -ENOMEM because of memory allocation errors,
+ *  and might return -EIO because of disk read errors.
+ */
+int nilfs_btnode_prepare_change_key(struct address_space *btnc,
+				    struct nilfs_btnode_chkey_ctxt *ctxt)
+{
+	struct buffer_head *obh, *nbh;
+	struct inode *inode = NILFS_BTNC_I(btnc);
+	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
+	int err;
+
+	if (oldkey == newkey)
+		return 0;
+
+	obh = ctxt->bh;
+	ctxt->newbh = NULL;
+
+	if (inode->i_blkbits == PAGE_CACHE_SHIFT) {
+		lock_page(obh->b_page);
+		/*
+		 * We cannot call radix_tree_preload for the kernels older
+		 * than 2.6.23, because it is not exported for modules.
+		 */
+		err = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
+		if (err)
+			goto failed_unlock;
+		/* BUG_ON(oldkey != obh->b_page->index); */
+		if (unlikely(oldkey != obh->b_page->index))
+			NILFS_PAGE_BUG(obh->b_page,
+				       "invalid oldkey %lld (newkey=%lld)",
+				       (unsigned long long)oldkey,
+				       (unsigned long long)newkey);
+
+retry:
+		spin_lock_irq(&btnc->tree_lock);
+		err = radix_tree_insert(&btnc->page_tree, newkey, obh->b_page);
+		spin_unlock_irq(&btnc->tree_lock);
+		/*
+		 * Note: page->index will not change to newkey until
+		 * nilfs_btnode_commit_change_key() will be called.
+		 * To protect the page in intermediate state, the page lock
+		 * is held.
+		 */
+		radix_tree_preload_end();
+		if (!err)
+			return 0;
+		else if (err != -EEXIST)
+			goto failed_unlock;
+
+		err = invalidate_inode_pages2_range(btnc, newkey, newkey);
+		if (!err)
+			goto retry;
+		/* fallback to copy mode */
+		unlock_page(obh->b_page);
+	}
+
+	err = nilfs_btnode_get(btnc, newkey, 0, &nbh, 1);
+	if (likely(!err)) {
+		BUG_ON(nbh == obh);
+		ctxt->newbh = nbh;
+	}
+	return err;
+
+ failed_unlock:
+	unlock_page(obh->b_page);
+	return err;
+}
+
+/**
+ * nilfs_btnode_commit_change_key
+ *  commit the change_key operation prepared by prepare_change_key().
+ */
+void nilfs_btnode_commit_change_key(struct address_space *btnc,
+				    struct nilfs_btnode_chkey_ctxt *ctxt)
+{
+	struct buffer_head *obh = ctxt->bh, *nbh = ctxt->newbh;
+	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
+	struct page *opage;
+
+	if (oldkey == newkey)
+		return;
+
+	if (nbh == NULL) {	/* blocksize == pagesize */
+		opage = obh->b_page;
+		if (unlikely(oldkey != opage->index))
+			NILFS_PAGE_BUG(opage,
+				       "invalid oldkey %lld (newkey=%lld)",
+				       (unsigned long long)oldkey,
+				       (unsigned long long)newkey);
+		if (!test_set_buffer_dirty(obh) && TestSetPageDirty(opage))
+			BUG();
+
+		spin_lock_irq(&btnc->tree_lock);
+		radix_tree_delete(&btnc->page_tree, oldkey);
+		radix_tree_tag_set(&btnc->page_tree, newkey,
+				   PAGECACHE_TAG_DIRTY);
+		spin_unlock_irq(&btnc->tree_lock);
+
+		opage->index = obh->b_blocknr = newkey;
+		unlock_page(opage);
+	} else {
+		nilfs_copy_buffer(nbh, obh);
+		nilfs_btnode_mark_dirty(nbh);
+
+		nbh->b_blocknr = newkey;
+		ctxt->bh = nbh;
+		nilfs_btnode_delete(obh); /* will decrement bh->b_count */
+	}
+}
+
+/**
+ * nilfs_btnode_abort_change_key
+ *  abort the change_key operation prepared by prepare_change_key().
+ */
+void nilfs_btnode_abort_change_key(struct address_space *btnc,
+				   struct nilfs_btnode_chkey_ctxt *ctxt)
+{
+	struct buffer_head *nbh = ctxt->newbh;
+	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
+
+	if (oldkey == newkey)
+		return;
+
+	if (nbh == NULL) {	/* blocksize == pagesize */
+		spin_lock_irq(&btnc->tree_lock);
+		radix_tree_delete(&btnc->page_tree, newkey);
+		spin_unlock_irq(&btnc->tree_lock);
+		unlock_page(ctxt->bh->b_page);
+	} else
+		brelse(nbh);
+}