diff --git a/.gitignore b/.gitignore
index d3f1b89..a573d69 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,4 @@
 **/*.rs.bk
 Cargo.lock
 .idea
-/sfs.img
+/*.img
diff --git a/src/sfs.rs b/src/sfs.rs
index 3e47564..5982280 100644
--- a/src/sfs.rs
+++ b/src/sfs.rs
@@ -144,7 +144,7 @@ impl INode {
                     self.set_disk_block_id(i as usize, disk_block_id).unwrap();
                 }
                 // clean up
-                let old_size = self.disk_inode.size as usize;
+                let old_size = self._size();
                 self.disk_inode.size = len as u32;
                 self._clean_at(old_size, len).unwrap();
             }
@@ -166,17 +166,22 @@ impl INode {
         self.disk_inode.size = len as u32;
         Ok(())
     }
+    /// Get the actual size of this inode,
+    /// since size in inode for dir is not real size
+    fn _size(&self) -> usize {
+        match self.disk_inode.type_ {
+            FileType::Dir => self.disk_inode.blocks as usize * BLKSIZE,
+            FileType::File => self.disk_inode.size as usize,
+            _ => unimplemented!(),
+        }
+    }
     /// Read/Write content, no matter what type it is
     fn _io_at<F>(&self, begin: usize, end: usize, mut f: F) -> vfs::Result<usize>
         where F: FnMut(RefMut<Box<Device>>, &BlockRange, usize)
     {
         let fs = self.fs.upgrade().unwrap();
 
-        let size = match self.disk_inode.type_ {
-            FileType::Dir => self.disk_inode.blocks as usize * BLKSIZE,
-            FileType::File => self.disk_inode.size as usize,
-            _ => unimplemented!(),
-        };
+        let size = self._size();
         let iter = BlockIter {
             begin: size.min(begin),
             end: size.min(end),
@@ -232,7 +237,7 @@ impl vfs::INode for INode {
     }
     fn info(&self) -> vfs::Result<vfs::FileInfo> {
         Ok(vfs::FileInfo {
-            size: self.disk_inode.size as usize,
+            size: self._size(),
             mode: 0,
             type_: vfs::FileType::from(self.disk_inode.type_.clone()),
             blocks: self.disk_inode.blocks as usize,
diff --git a/src/tests.rs b/src/tests.rs
index ce19b5a..f09e89f 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -1,3 +1,4 @@
+use std::fs;
 use std::fs::{File, OpenOptions};
 use std::io::{Read, Write, Seek, SeekFrom};
 use std::boxed::Box;
@@ -27,8 +28,10 @@ impl Device for File {
 }
 
 fn _open_sample_file() -> Rc<SimpleFileSystem> {
-    let file = File::open("sfs.img")
-        .expect("failed to open sfs.img");
+    fs::copy("sfs.img","test.img").expect("failed to open sfs.img");
+    let file = OpenOptions::new()
+        .read(true).write(true).open("test.img")
+        .expect("failed to open test.img");
     SimpleFileSystem::open(Box::new(file))
         .expect("failed to open SFS")
 }
@@ -149,4 +152,16 @@ fn rc_layout() {
     let start = unsafe{ (ptr as *const usize).offset(-2) };
     let ns = unsafe{ &*(start as *const [usize; 2]) };
     assert_eq!(ns, &[1usize, 1]);
+}
+
+// #[test]
+fn kernel_image_file_create(){
+    let sfs = _open_sample_file();
+    let root = sfs.root_inode();
+    let files_count_before = root.borrow().list().unwrap();
+    root.borrow_mut().create("hello2",FileType::File).unwrap();
+    let files_count_after = root.borrow().list().unwrap();
+    assert_eq!(files_count_before+1, files_count_after)
+
+    sfs.sync().unwrap();
 }
\ No newline at end of file