diff --git a/fs/nilfs2/segbuf.h b/fs/nilfs2/segbuf.h
new file mode 100644
index 0000000..25f2a5f
--- /dev/null
+++ b/fs/nilfs2/segbuf.h
@@ -0,0 +1,203 @@
+/*
+ * segbuf.h - NILFS Segment buffer prototypes and definitions
+ *
+ * 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>
+ *
+ */
+#ifndef _NILFS_SEGBUF_H
+#define _NILFS_SEGBUF_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/bio.h>
+#include <linux/completion.h>
+#include <linux/backing-dev.h>
+
+/**
+ * struct nilfs_segsum_info - On-memory segment summary
+ * @flags: Flags
+ * @nfinfo: Number of file information structures
+ * @nblocks: Number of blocks included in the partial segment
+ * @nsumblk: Number of summary blocks
+ * @sumbytes: Byte count of segment summary
+ * @nfileblk: Total number of file blocks
+ * @seg_seq: Segment sequence number
+ * @ctime: Creation time
+ * @next: Block number of the next full segment
+ */
+struct nilfs_segsum_info {
+	unsigned int		flags;
+	unsigned long		nfinfo;
+	unsigned long		nblocks;
+	unsigned long		nsumblk;
+	unsigned long		sumbytes;
+	unsigned long		nfileblk;
+	u64			seg_seq;
+	time_t			ctime;
+	sector_t		next;
+};
+
+/* macro for the flags */
+#define NILFS_SEG_HAS_SR(sum)    ((sum)->flags & NILFS_SS_SR)
+#define NILFS_SEG_LOGBGN(sum)    ((sum)->flags & NILFS_SS_LOGBGN)
+#define NILFS_SEG_LOGEND(sum)    ((sum)->flags & NILFS_SS_LOGEND)
+#define NILFS_SEG_DSYNC(sum)     ((sum)->flags & NILFS_SS_SYNDT)
+#define NILFS_SEG_SIMPLEX(sum) \
+	(((sum)->flags & (NILFS_SS_LOGBGN | NILFS_SS_LOGEND)) == \
+	 (NILFS_SS_LOGBGN | NILFS_SS_LOGEND))
+
+#define NILFS_SEG_EMPTY(sum)	((sum)->nblocks == (sum)->nsumblk)
+
+/**
+ * struct nilfs_segment_buffer - Segment buffer
+ * @sb_super: back pointer to a superblock struct
+ * @sb_list: List head to chain this structure
+ * @sb_segent: Pointer for attaching a segment entry
+ * @sb_sum: On-memory segment summary
+ * @sb_segnum: Index number of the full segment
+ * @sb_nextnum: Index number of the next full segment
+ * @sb_fseg_start: Start block number of the full segment
+ * @sb_fseg_end: End block number of the full segment
+ * @sb_pseg_start: Disk block number of partial segment
+ * @sb_rest_blocks: Number of residual blocks in the current segment
+ * @sb_segsum_buffers: List of buffers for segment summaries
+ * @sb_payload_buffers: List of buffers for segment payload
+ * @sb_io_error: I/O error status
+ */
+struct nilfs_segment_buffer {
+	struct super_block     *sb_super;
+	struct list_head	sb_list;
+	struct nilfs_segment_entry *sb_segent;
+
+	/* Segment information */
+	struct nilfs_segsum_info sb_sum;
+	__u64			sb_segnum;
+	__u64			sb_nextnum;
+	sector_t		sb_fseg_start, sb_fseg_end;
+	sector_t		sb_pseg_start;
+	unsigned		sb_rest_blocks;
+
+	/* Buffers */
+	struct list_head	sb_segsum_buffers;
+	struct list_head	sb_payload_buffers; /* including super root */
+
+	/* io status */
+	int			sb_io_error;
+};
+
+#define NILFS_LIST_SEGBUF(head)  \
+	list_entry((head), struct nilfs_segment_buffer, sb_list)
+#define NILFS_NEXT_SEGBUF(segbuf)  NILFS_LIST_SEGBUF((segbuf)->sb_list.next)
+#define NILFS_PREV_SEGBUF(segbuf)  NILFS_LIST_SEGBUF((segbuf)->sb_list.prev)
+#define NILFS_LAST_SEGBUF(head)    NILFS_LIST_SEGBUF((head)->prev)
+#define NILFS_FIRST_SEGBUF(head)   NILFS_LIST_SEGBUF((head)->next)
+#define NILFS_SEGBUF_IS_LAST(segbuf, head)  ((segbuf)->sb_list.next == (head))
+
+#define nilfs_for_each_segbuf_before(s, t, h) \
+	for ((s) = NILFS_FIRST_SEGBUF(h); (s) != (t); \
+	     (s) = NILFS_NEXT_SEGBUF(s))
+
+#define NILFS_SEGBUF_FIRST_BH(head)  \
+	(list_entry((head)->next, struct buffer_head, b_assoc_buffers))
+#define NILFS_SEGBUF_NEXT_BH(bh)  \
+	(list_entry((bh)->b_assoc_buffers.next, struct buffer_head, \
+		    b_assoc_buffers))
+#define NILFS_SEGBUF_BH_IS_LAST(bh, head)  ((bh)->b_assoc_buffers.next == head)
+
+
+int __init nilfs_init_segbuf_cache(void);
+void nilfs_destroy_segbuf_cache(void);
+struct nilfs_segment_buffer *nilfs_segbuf_new(struct super_block *);
+void nilfs_segbuf_free(struct nilfs_segment_buffer *);
+int nilfs_segbuf_map(struct nilfs_segment_buffer *, __u64, unsigned long,
+		     struct the_nilfs *);
+void nilfs_segbuf_set_next_segnum(struct nilfs_segment_buffer *, __u64,
+				  struct the_nilfs *);
+int nilfs_segbuf_reset(struct nilfs_segment_buffer *, unsigned, time_t);
+int nilfs_segbuf_extend_segsum(struct nilfs_segment_buffer *);
+int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *,
+				struct buffer_head **);
+void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *);
+void nilfs_segbuf_fill_in_segsum_crc(struct nilfs_segment_buffer *, u32);
+void nilfs_segbuf_fill_in_data_crc(struct nilfs_segment_buffer *, u32);
+
+static inline void
+nilfs_segbuf_add_segsum_buffer(struct nilfs_segment_buffer *segbuf,
+			       struct buffer_head *bh)
+{
+	list_add_tail(&bh->b_assoc_buffers, &segbuf->sb_segsum_buffers);
+	segbuf->sb_sum.nblocks++;
+	segbuf->sb_sum.nsumblk++;
+}
+
+static inline void
+nilfs_segbuf_add_payload_buffer(struct nilfs_segment_buffer *segbuf,
+				struct buffer_head *bh)
+{
+	list_add_tail(&bh->b_assoc_buffers, &segbuf->sb_payload_buffers);
+	segbuf->sb_sum.nblocks++;
+}
+
+static inline void
+nilfs_segbuf_add_file_buffer(struct nilfs_segment_buffer *segbuf,
+			     struct buffer_head *bh)
+{
+	get_bh(bh);
+	nilfs_segbuf_add_payload_buffer(segbuf, bh);
+	segbuf->sb_sum.nfileblk++;
+}
+
+void nilfs_release_buffers(struct list_head *);
+
+static inline void nilfs_segbuf_clear(struct nilfs_segment_buffer *segbuf)
+{
+	nilfs_release_buffers(&segbuf->sb_segsum_buffers);
+	nilfs_release_buffers(&segbuf->sb_payload_buffers);
+}
+
+struct nilfs_write_info {
+	struct bio	       *bio;
+	int 			start, end; /* The region to be submitted */
+	int			rest_blocks;
+	int			max_pages;
+	int			nr_vecs;
+	sector_t		blocknr;
+
+	int			nbio;
+	atomic_t		err;
+	struct completion	bio_event;
+				/* completion event of segment write */
+
+	/*
+	 * The following fields must be set explicitly
+	 */
+	struct super_block     *sb;
+	struct backing_dev_info *bdi; /* backing dev info */
+	struct buffer_head     *bh_sr;
+};
+
+
+void nilfs_segbuf_prepare_write(struct nilfs_segment_buffer *,
+				struct nilfs_write_info *);
+int nilfs_segbuf_write(struct nilfs_segment_buffer *,
+		       struct nilfs_write_info *);
+int nilfs_segbuf_wait(struct nilfs_segment_buffer *,
+		      struct nilfs_write_info *);
+
+#endif /* _NILFS_SEGBUF_H */