vfs: export vfs_dedupe_file_range_one() to modules

This is needed by the stacked dedupe implementation in overlayfs.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/read_write.c

@@ -1964,9 +1964,8 @@ int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
 }
 EXPORT_SYMBOL(vfs_dedupe_file_range_compare);
 
-static int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
-				     struct file *dst_file, loff_t dst_pos,
-				     u64 len)
+int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
+			      struct file *dst_file, loff_t dst_pos, u64 len)
 {
 	s64 ret;
 
@@ -2001,6 +2000,7 @@ static int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
 
 	return ret;
 }
+EXPORT_SYMBOL(vfs_dedupe_file_range_one);
 
 int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
 {

include/linux/fs.h

@@ -1829,6 +1829,10 @@ extern int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
 					 loff_t len, bool *is_same);
 extern int vfs_dedupe_file_range(struct file *file,
 				 struct file_dedupe_range *same);
+extern int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
+				     struct file *dst_file, loff_t dst_pos,
+				     u64 len);
+
 
 struct super_operations {
    	struct inode *(*alloc_inode)(struct super_block *sb);