diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c5f40dc..2132fa5 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1860,6 +1860,9 @@ struct btrfs_fs_info {
 	struct list_head pinned_chunks;
 
 	int creating_free_space_tree;
+
+	/* reference to inband de-duplication info */
+	struct btrfs_dedup_info *dedup_info;
 };
 
 struct btrfs_subvolume_writers {
diff --git a/fs/btrfs/dedup.h b/fs/btrfs/dedup.h
new file mode 100644
index 0000000..f0edc76
--- /dev/null
+++ b/fs/btrfs/dedup.h
@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2015 Fujitsu.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * 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., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __BTRFS_DEDUP__
+#define __BTRFS_DEDUP__
+
+#include <linux/btrfs.h>
+#include <crypto/hash.h>
+
+/*
+ * Dedup storage backend
+ * On disk is persist storage but overhead is large
+ * In memory is fast but will lose all its hash on umount
+ */
+#define BTRFS_DEDUP_BACKEND_INMEMORY		0
+#define BTRFS_DEDUP_BACKEND_ONDISK		1
+#define BTRFS_DEDUP_BACKEND_LAST		2
+
+/* Dedup block size limit and default value */
+#define BTRFS_DEDUP_BLOCKSIZE_MAX	(8 * 1024 * 1024)
+#define BTRFS_DEDUP_BLOCKSIZE_MIN	(16 * 1024)
+#define BTRFS_DEDUP_BLOCKSIZE_DEFAULT	(32 * 1024)
+
+/* Hash algorithm, only support SHA256 yet */
+#define BTRFS_DEDUP_HASH_SHA256		0
+
+static int btrfs_dedup_sizes[] = { 32 };
+
+/*
+ * For caller outside of dedup.c
+ *
+ * Different dedup backends should have their own hash structure
+ */
+struct btrfs_dedup_hash {
+	u64 bytenr;
+	u32 num_bytes;
+
+	/* last field is a variable length array of dedup hash */
+	u8 hash[];
+};
+
+struct btrfs_dedup_info {
+	/* dedup blocksize */
+	u64 blocksize;
+	u16 backend;
+	u16 hash_type;
+
+	struct crypto_shash *dedup_driver;
+	struct mutex lock;
+
+	/* following members are only used in in-memory dedup mode */
+	struct rb_root hash_root;
+	struct rb_root bytenr_root;
+	struct list_head lru_list;
+	u64 limit_nr;
+	u64 current_nr;
+};
+
+struct btrfs_trans_handle;
+
+int btrfs_dedup_hash_size(u16 type);
+struct btrfs_dedup_hash *btrfs_dedup_alloc_hash(u16 type);
+
+/*
+ * Initial inband dedup info
+ * Called at dedup enable time.
+ */
+int btrfs_dedup_enable(struct btrfs_fs_info *fs_info, u16 type, u16 backend,
+		       u64 blocksize, u64 limit);
+
+/*
+ * Disable dedup and invalidate all its dedup data.
+ * Called at dedup disable time.
+ */
+int btrfs_dedup_disable(struct btrfs_fs_info *fs_info);
+
+/*
+ * Calculate hash for dedup.
+ * Caller must ensure [start, start + dedup_bs) has valid data.
+ */
+int btrfs_dedup_calc_hash(struct btrfs_root *root, struct inode *inode,
+			  u64 start, struct btrfs_dedup_hash *hash);
+
+/*
+ * Search for duplicated extents by calculated hash
+ * Caller must call btrfs_dedup_calc_hash() first to get the hash.
+ *
+ * @inode: the inode for we are writing
+ * @file_pos: offset inside the inode
+ * As we will increase extent ref immediately after a hash match,
+ * we need @file_pos and @inode in this case.
+ *
+ * Return > 0 for a hash match, and the extent ref will be
+ * *INCREASED*, and hash->bytenr/num_bytes will record the existing
+ * extent data.
+ * Return 0 for a hash miss. Nothing is done
+ */
+int btrfs_dedup_search(struct inode *inode, u64 file_pos,
+		       struct btrfs_dedup_hash *hash);
+
+/* Add a dedup hash into dedup info */
+int btrfs_dedup_add(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+		    struct btrfs_dedup_hash *hash);
+
+/* Remove a dedup hash from dedup info */
+int btrfs_dedup_del(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+		    u64 bytenr);
+#endif
