Actually, these systemcalls or inode operations were introduced in linux-2.6.17.
But I don't think there exists an application issuces such new systemcalls,
and aufs decided not to support them in linux-2.6.17.
In linux-2.6.23, sendfile inode operation was removed and aufs becomes having to
support splice oprations.

In other words, this patch is for linux-2.6.23 and later. Aufs doesn't support
splice related systemcalls before 2.6.23.

Index: include/linux/splice.h
===================================================================
RCS file: /ext1/sysadm/transparent/repository/linux-2.6.23-rc6/include/linux/splice.h,v
retrieving revision 1.1
retrieving revision 1.3
diff -u -p -r1.1 -r1.3
--- include/linux/splice.h	12 Sep 2007 16:27:22 -0000	1.1
+++ include/linux/splice.h	14 Sep 2007 03:42:28 -0000	1.3
@@ -70,4 +70,10 @@ extern ssize_t splice_to_pipe(struct pip
 extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *,
 				      splice_direct_actor *);
 
+extern long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+			   loff_t *ppos, size_t len, unsigned int flags);
+extern long do_splice_to(struct file *in, loff_t *ppos,
+			 struct pipe_inode_info *pipe, size_t len,
+			 unsigned int flags);
+
 #endif
Index: fs/splice.c
===================================================================
RCS file: /ext1/sysadm/transparent/repository/linux-2.6.23-rc6/fs/splice.c,v
retrieving revision 1.1
retrieving revision 1.3
diff -u -p -r1.1 -r1.3
--- fs/splice.c	12 Sep 2007 16:25:07 -0000	1.1
+++ fs/splice.c	14 Sep 2007 03:42:27 -0000	1.3
@@ -943,8 +943,8 @@ EXPORT_SYMBOL(generic_splice_sendpage);
 /*
  * Attempt to initiate a splice from pipe to file.
  */
-static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
-			   loff_t *ppos, size_t len, unsigned int flags)
+long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+		    loff_t *ppos, size_t len, unsigned int flags)
 {
 	int ret;
 
@@ -964,13 +964,14 @@ static long do_splice_from(struct pipe_i
 
 	return out->f_op->splice_write(pipe, out, ppos, len, flags);
 }
+EXPORT_SYMBOL(do_splice_from);
 
 /*
  * Attempt to initiate a splice from a file to a pipe.
  */
-static long do_splice_to(struct file *in, loff_t *ppos,
-			 struct pipe_inode_info *pipe, size_t len,
-			 unsigned int flags)
+long do_splice_to(struct file *in, loff_t *ppos,
+		  struct pipe_inode_info *pipe, size_t len,
+		  unsigned int flags)
 {
 	int ret;
 
@@ -990,6 +991,7 @@ static long do_splice_to(struct file *in
 
 	return in->f_op->splice_read(in, ppos, pipe, len, flags);
 }
+EXPORT_SYMBOL(do_splice_to);
 
 /**
  * splice_direct_to_actor - splices data directly between two non-pipes