diff --git a/.travis.yml b/.travis.yml
index 613564f..0f33674 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1 +1,3 @@
-language: rust
\ No newline at end of file
+language: rust
+rust:
+  - nightly
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index bb5692b..d76f4dd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,5 @@
 #![feature(alloc)]
+#![feature(const_fn)]
 #![no_std]
 
 #[cfg(test)]
diff --git a/src/sfs.rs b/src/sfs.rs
index 14c2e9e..6029e8b 100644
--- a/src/sfs.rs
+++ b/src/sfs.rs
@@ -17,14 +17,14 @@ pub trait Device {
 
     // Helper functions
 
-    fn read_block(&mut self, id: BlockId, offset: usize, buf: &mut [u8]) -> Result<(), ()> {
+    fn read_block(&mut self, id: BlockId, offset: usize, buf: &mut [u8]) -> vfs::Result<()> {
         debug_assert!(offset + buf.len() <= BLKSIZE);
         match self.read_at(id * BLKSIZE + offset, buf) {
             Some(len) if len == buf.len() => Ok(()),
             _ => Err(()),
         }
     }
-    fn write_block(&mut self, id: BlockId, offset: usize, buf: &[u8]) -> Result<(), ()> {
+    fn write_block(&mut self, id: BlockId, offset: usize, buf: &[u8]) -> vfs::Result<()> {
         debug_assert!(offset + buf.len() <= BLKSIZE);
         match self.write_at(id * BLKSIZE + offset, buf) {
             Some(len) if len == buf.len() => Ok(()),
@@ -33,13 +33,15 @@ pub trait Device {
     }
 }
 
-/// Load struct `T` from given block in device
-///     Workaround: It should be inside the trait `Device`. But that would cause compile error.
-fn load_struct<T: AsBuf>(device: &mut Device, id: BlockId) -> T {
-    let mut s: T = unsafe { uninitialized() };
-    device.read_block(id, 0, s.as_buf_mut()).unwrap();
-    s
+trait DeviceExt: Device {
+    /// Load struct `T` from given block in device
+    fn load_struct<T: AsBuf>(&mut self, id: BlockId) -> T {
+        let mut s: T = unsafe { uninitialized() };
+        self.read_block(id, 0, s.as_buf_mut()).unwrap();
+        s
+    }
 }
+impl DeviceExt for Device {}
 
 type Ptr<T> = Rc<RefCell<T>>;
 type WeakPtr<T> = Weak<RefCell<T>>;
@@ -81,7 +83,7 @@ impl INode {
             id => unimplemented!("double indirect blocks is not supported"),
         }
     }
-    fn set_disk_block_id(&mut self, file_block_id: BlockId, disk_block_id: BlockId) -> Result<(),()> {
+    fn set_disk_block_id(&mut self, file_block_id: BlockId, disk_block_id: BlockId) -> vfs::Result<()> {
         match file_block_id {
             id if id >= self.disk_inode.blocks as BlockId =>
                 Err(()),
@@ -102,17 +104,56 @@ impl INode {
             id => unimplemented!("double indirect blocks is not supported"),
         }
     }
+    /// Only for Dir
+    fn get_file_inode_id(&mut self, name: &'static str) -> Option<INodeId> {
+        (0 .. self.disk_inode.blocks)
+            .map(|i| {
+                use vfs::INode;
+                let mut entry: DiskEntry = unsafe {uninitialized()};
+                self.read_at(i as usize * BLKSIZE, entry.as_buf_mut()).unwrap();
+                entry
+            })
+            .find(|entry| entry.name.as_ref() == name)
+            .map(|entry| entry.id as INodeId)
+    }
+    /// Init dir content. Insert 2 init entries.
+    fn init_dir(&mut self, parent: INodeId) -> vfs::Result<()> {
+        use vfs::INode;
+        // Insert entries: '.' '..'
+        self.resize(BLKSIZE * 2).unwrap();
+        self.write_at(0, DiskEntry {
+            id: parent as u32,
+            name: Str256::from(".."),
+        }.as_buf()).unwrap();
+        let id = self.id as u32;
+        self.write_at(0, DiskEntry {
+            id,
+            name: Str256::from("."),
+        }.as_buf()).unwrap();
+        Ok(())
+    }
+    fn clean_at(&mut self, begin: usize, end: usize) -> vfs::Result<()> {
+        let fs = self.fs.upgrade().unwrap();
+
+        let iter = BlockIter { begin, end };
+        for BlockRange { block, begin, end } in iter {
+            static ZEROS: [u8; BLKSIZE] = [0; BLKSIZE];
+            let disk_block_id = self.get_disk_block_id(block).unwrap();
+            fs.borrow_mut().device.write_block(disk_block_id, begin, &ZEROS[begin..end]).unwrap();
+        }
+        Ok(())
+    }
 }
 
 impl vfs::INode for INode {
-    fn open(&mut self, flags: u32) -> Result<(), ()> {
+    fn open(&mut self, flags: u32) -> vfs::Result<()> {
         // Do nothing
         Ok(())
     }
-    fn close(&mut self) -> Result<(), ()> {
+    fn close(&mut self) -> vfs::Result<()> {
         self.sync()
     }
-    fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> Option<usize> {
+    fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> vfs::Result<usize> {
         let fs = self.fs.upgrade().unwrap();
 
         let iter = BlockIter {
@@ -123,18 +164,14 @@ impl vfs::INode for INode {
         // Read for each block
         let mut buf_offset = 0usize;
         for BlockRange { block, begin, end } in iter {
-            if let Some(disk_block_id) = self.get_disk_block_id(block) {
-                let len = end - begin;
-                fs.borrow_mut().device.read_block(disk_block_id, begin, &mut buf[buf_offset..buf_offset + len]).unwrap();
-                buf_offset += len;
-            } else {
-                // Failed this time
-                break;
-            }
+            let disk_block_id = self.get_disk_block_id(block).unwrap();
+            let len = end - begin;
+            fs.borrow_mut().device.read_block(disk_block_id, begin, &mut buf[buf_offset..buf_offset + len]).unwrap();
+            buf_offset += len;
         }
-        Some(buf_offset)
+        Ok(buf_offset)
     }
-    fn write_at(&mut self, offset: usize, buf: &[u8]) -> Option<usize> {
+    fn write_at(&mut self, offset: usize, buf: &[u8]) -> vfs::Result<usize> {
         let fs = self.fs.upgrade().unwrap();
 
         let iter = BlockIter {
@@ -142,43 +179,33 @@ impl vfs::INode for INode {
             end: offset + buf.len(),
         };
 
-        // Read for each block
+        // Write for each block
         let mut buf_offset = 0usize;
         for BlockRange { block, begin, end } in iter {
-            if let Some(disk_block_id) = self.get_disk_block_id(block) {
-                let len = end - begin;
-                fs.borrow_mut().device.write_block(disk_block_id, begin, &buf[buf_offset..buf_offset + len]).unwrap();
-                buf_offset += len;
-            } else {
-                // Failed this time
-                break;
-            }
+            let disk_block_id = self.get_disk_block_id(block).unwrap();
+            let len = end - begin;
+            fs.borrow_mut().device.write_block(disk_block_id, begin, &buf[buf_offset..buf_offset + len]).unwrap();
+            buf_offset += len;
         }
-        Some(buf_offset)
+        Ok(buf_offset)
     }
-    fn info(&mut self) -> Result<vfs::FileInfo, ()> {
-        if self.disk_inode.type_ != FileType::File {
-            return Err(());
-        }
+    fn info(&mut self) -> vfs::Result<vfs::FileInfo> {
         Ok(vfs::FileInfo {
             size: self.disk_inode.size as usize,
             mode: 0,
+            type_: vfs::FileType::from(self.disk_inode.type_.clone()),
         })
     }
-    fn sync(&mut self) -> Result<(), ()> {
+    fn sync(&mut self) -> vfs::Result<()> {
         if self.disk_inode.dirty() {
-            let fs0 = self.fs.upgrade().unwrap();
-            let mut fs = fs0.borrow_mut();
-            fs.device.write_block(self.id, 0, self.disk_inode.as_buf())?;
+            let fs = self.fs.upgrade().unwrap();
+            fs.borrow_mut().device.write_block(self.id, 0, self.disk_inode.as_buf()).unwrap();
             self.disk_inode.sync();
         }
         Ok(())
     }
-    fn type_(&self) -> Result<u32, ()> {
-        Ok(self.disk_inode.type_.clone() as u32)
-    }
-    fn resize(&mut self, len: usize) -> Result<(), ()> {
-        if self.disk_inode.type_ != FileType::File || len > MAX_FILE_SIZE {
+    fn resize(&mut self, len: usize) -> vfs::Result<()> {
+        if len > MAX_FILE_SIZE {
             return Err(());
         }
         let blocks = ((len + BLKSIZE - 1) / BLKSIZE) as u32;
@@ -189,11 +216,18 @@ impl vfs::INode for INode {
                 let fs = self.fs.upgrade().unwrap();
                 let old_blocks = self.disk_inode.blocks;
                 self.disk_inode.blocks = blocks;
+                // allocate indirect block if need
+                if old_blocks < NDIRECT as u32 && blocks >= NDIRECT as u32 {
+                    self.disk_inode.indirect = fs.borrow_mut().alloc_block().unwrap() as u32;
+                }
                 // allocate extra blocks
                 for i in old_blocks .. blocks {
                     let disk_block_id = fs.borrow_mut().alloc_block().expect("no more space");
                     self.set_disk_block_id(i as usize, disk_block_id).unwrap();
                 }
+                // clean up
+                let old_size = self.disk_inode.size as usize;
+                self.clean_at(old_size, len).unwrap();
             },
             Ordering::Less => {
                 let fs = self.fs.upgrade().unwrap();
@@ -202,12 +236,70 @@ impl vfs::INode for INode {
                     let disk_block_id = self.get_disk_block_id(i as usize).unwrap();
                     fs.borrow_mut().free_block(disk_block_id);
                 }
+                // free indirect block if need
+                if blocks < NDIRECT as u32 && self.disk_inode.blocks >= NDIRECT as u32 {
+                    fs.borrow_mut().free_block(self.disk_inode.indirect as usize);
+                    self.disk_inode.indirect = 0;
+                }
                 self.disk_inode.blocks = blocks;
             },
         }
         self.disk_inode.size = len as u32;
         Ok(())
     }
+    fn create(&mut self, name: &'static str) -> vfs::Result<Ptr<vfs::INode>> {
+        let fs = self.fs.upgrade().unwrap();
+        let info = self.info().unwrap();
+        assert_eq!(info.type_, vfs::FileType::Dir);
+        assert_eq!(info.size % BLKSIZE, 0);
+
+        // Ensure the name is not exist
+        assert!(self.get_file_inode_id(name).is_none(), "file name exist");
+
+        // Create new INode
+        let inode = fs.borrow_mut().new_inode_file().unwrap();
+
+        // Write new entry
+        let entry = DiskEntry {
+            id: inode.borrow().id as u32,
+            name: Str256::from(name),
+        };
+        self.resize(info.size + BLKSIZE).unwrap();
+        self.write_at(info.size, entry.as_buf()).unwrap();
+
+        Ok(inode)
+    }
+    fn loopup(&mut self, path: &'static str) -> vfs::Result<Ptr<vfs::INode>> {
+        let fs = self.fs.upgrade().unwrap();
+        let info = self.info().unwrap();
+        assert_eq!(info.type_, vfs::FileType::Dir);
+        assert_eq!(info.size % BLKSIZE, 0);
+
+        let (name, rest_path) = match path.find('/') {
+            None => (path, ""),
+            Some(pos) => (&path[0..pos], &path[pos+1..]),
+        };
+        let inode_id = self.get_file_inode_id(name);
+        if inode_id.is_none() {
+            return Err(());
+        }
+        let inode = fs.borrow_mut().get_inode(inode_id.unwrap());
+
+        let type_ = inode.borrow().disk_inode.type_;
+        match type_ {
+            FileType::File => if rest_path == "" {Ok(inode)} else {Err(())},
+            FileType::Dir => inode.borrow_mut().loopup(rest_path),
+            _ => unimplemented!(),
+        }
+    }
+}
+
+impl Drop for INode {
+    /// Auto sync when drop
+    fn drop(&mut self) {
+        use vfs::INode;
+        self.sync().expect("failed to sync");
+    }
 }
 
 /// Given a range and iterate sub-range for each block
@@ -256,11 +348,11 @@ pub struct SimpleFileSystem {
 impl SimpleFileSystem {
     /// Load SFS from device
     pub fn open(mut device: Box<Device>) -> Option<Ptr<Self>> {
-        let super_block = load_struct::<SuperBlock>(device.as_mut(), BLKN_SUPER);
+        let super_block = device.load_struct::<SuperBlock>(BLKN_SUPER);
         if super_block.check() == false {
             return None;
         }
-        let free_map = load_struct::<[u8; BLKSIZE]>(device.as_mut(), BLKN_FREEMAP);
+        let free_map = device.load_struct::<[u8; BLKSIZE]>(BLKN_FREEMAP);
 
         Some(SimpleFileSystem {
             super_block: Dirty::new(super_block),
@@ -279,19 +371,38 @@ impl SimpleFileSystem {
             magic: MAGIC,
             blocks: blocks as u32,
             unused_blocks: blocks as u32 - 3,
-            info: Str32::from_slice(b"simple file system"),
+            info: Str32::from("simple file system"),
         };
-        let mut free_map = BitSet::with_capacity(BLKBITS);
-        for i in 3 .. blocks {
-            free_map.insert(i);
-        }
-        SimpleFileSystem {
+        let free_map = {
+            let mut bitset = BitSet::with_capacity(BLKBITS);
+            for i in 3 .. blocks {
+                bitset.insert(i);
+            }
+            bitset
+        };
+
+        let sfs = SimpleFileSystem {
             super_block: Dirty::new_dirty(super_block),
             free_map: Dirty::new_dirty(free_map),
             inodes: BTreeMap::<INodeId, Ptr<INode>>::new(),
             device,
             self_ptr: Weak::default(),
-        }.wrap()
+        }.wrap();
+
+        // Init root INode
+        let inode = Rc::new(RefCell::new(INode {
+            disk_inode: Dirty::new_dirty(DiskINode::new_dir()),
+            id: BLKN_ROOT,
+            fs: Rc::downgrade(&sfs),
+        }));
+        inode.borrow_mut().init_dir(BLKN_ROOT).unwrap();
+        {
+            use vfs::INode;
+            inode.borrow_mut().sync().unwrap();
+        }
+        sfs.borrow_mut().inodes.insert(BLKN_ROOT, inode);
+
+        sfs
     }
     /// Wrap pure SimpleFileSystem with Rc<RefCell<...>>
     /// Used in constructors
@@ -322,7 +433,7 @@ impl SimpleFileSystem {
 
         // Load if not in memory.
         if !self.inodes.contains_key(&id) {
-            let disk_inode = load_struct::<DiskINode>(self.device.as_mut(), id);
+            let disk_inode = self.device.load_struct::<DiskINode>(id);
             let inode = Rc::new(RefCell::new(INode {
                 disk_inode: Dirty::new(disk_inode),
                 id,
@@ -334,17 +445,39 @@ impl SimpleFileSystem {
             self.inodes.get(&id).unwrap().clone()
         }
     }
+    /// Create a new INode file
+    fn new_inode_file(&mut self) -> vfs::Result<Ptr<INode>> {
+        let id = self.alloc_block().unwrap();
+        Ok(Rc::new(RefCell::new(INode {
+            disk_inode: Dirty::new_dirty(DiskINode::new_file()),
+            id,
+            fs: self.self_ptr.clone(),
+        })))
+    }
+    /// Create a new INode dir
+    fn new_inode_dir(&mut self, parent: INodeId) -> vfs::Result<Ptr<INode>> {
+        let id = self.alloc_block().unwrap();
+        let mut inode = INode {
+            disk_inode: Dirty::new_dirty(DiskINode::new_dir()),
+            id,
+            fs: self.self_ptr.clone(),
+        };
+        inode.init_dir(parent).unwrap();
+
+        Ok(Rc::new(RefCell::new(inode)))
+    }
 }
 
 impl vfs::FileSystem for SimpleFileSystem {
     type INode = INode;
 
     /// Write back super block if dirty
-    fn sync(&mut self) -> Result<(), ()> {
+    fn sync(&mut self) -> vfs::Result<()> {
         let SimpleFileSystem {
             ref mut super_block,
             ref mut device,
             ref mut free_map,
+            ref mut inodes,
             ..
         } = self;
 
@@ -356,6 +489,10 @@ impl vfs::FileSystem for SimpleFileSystem {
             device.write_at(BLKSIZE * BLKN_FREEMAP, free_map.as_buf()).unwrap();
             free_map.sync();
         }
+        for inode in inodes.values() {
+            use vfs::INode;
+            inode.borrow_mut().sync().unwrap();
+        }
         Ok(())
     }
 
@@ -363,7 +500,7 @@ impl vfs::FileSystem for SimpleFileSystem {
         self.get_inode(BLKN_ROOT)
     }
 
-    fn unmount(&mut self) -> Result<(), ()> {
+    fn unmount(&mut self) -> vfs::Result<()> {
         unimplemented!()
     }
 
@@ -408,6 +545,16 @@ impl AsBuf for BitSet {
 
 impl AsBuf for [u8; BLKSIZE] {}
 
+impl From<FileType> for vfs::FileType {
+    fn from(t: FileType) -> Self {
+        match t {
+            FileType::File => vfs::FileType::File,
+            FileType::Dir => vfs::FileType::Dir,
+            _ => panic!("unknown file type"),
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
diff --git a/src/structs.rs b/src/structs.rs
index 11df346..16f65ca 100644
--- a/src/structs.rs
+++ b/src/structs.rs
@@ -3,6 +3,7 @@
 use core::slice;
 use core::mem::size_of_val;
 use core::fmt::{Debug, Formatter, Error};
+use alloc::str;
 
 /// On-disk superblock
 #[repr(C, packed)]
@@ -58,24 +59,39 @@ pub struct Str256(pub [u8; 256]);
 #[repr(C)]
 pub struct Str32(pub [u8; 32]);
 
+impl AsRef<str> for Str256 {
+    fn as_ref(&self) -> &str {
+        let len = self.0.iter().enumerate().find(|(_, &b)| b == 0).unwrap().0;
+        str::from_utf8(&self.0[0..len]).unwrap()
+    }
+}
+impl AsRef<str> for Str32 {
+    fn as_ref(&self) -> &str {
+        let len = self.0.iter().enumerate().find(|(_, &b)| b == 0).unwrap().0;
+        str::from_utf8(&self.0[0..len]).unwrap()
+    }
+}
 impl Debug for Str256 {
     fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
-        use alloc::String;
-        let len = self.0.iter().enumerate().find(|(i, &b)| b == 0).unwrap().0;
-        write!(f, "{}", String::from_utf8_lossy(&self.0[0 .. len]))
+        write!(f, "{}", self.as_ref())
     }
 }
 impl Debug for Str32 {
     fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
-        use alloc::String;
-        let len = self.0.iter().enumerate().find(|(i, &b)| b == 0).unwrap().0;
-        write!(f, "{}", String::from_utf8_lossy(&self.0[0 .. len]))
+        write!(f, "{}", self.as_ref())
+    }
+}
+impl From<&'static str> for Str256 {
+    fn from(s: &'static str) -> Self {
+        let mut ret = [0u8; 256];
+        ret[0..s.len()].copy_from_slice(s.as_ref());
+        Str256(ret)
     }
 }
-impl Str32 {
-    pub fn from_slice(s: &[u8]) -> Self {
+impl From<&'static str> for Str32 {
+    fn from(s: &'static str) -> Self {
         let mut ret = [0u8; 32];
-        ret[0..s.len()].copy_from_slice(s);
+        ret[0..s.len()].copy_from_slice(s.as_ref());
         Str32(ret)
     }
 }
@@ -86,6 +102,31 @@ impl SuperBlock {
     }
 }
 
+impl DiskINode {
+    pub const fn new_file() -> Self {
+        DiskINode {
+            size: 0,
+            type_: FileType::File,
+            nlinks: 0,
+            blocks: 0,
+            direct: [0; NDIRECT],
+            indirect: 0,
+            db_indirect: 0,
+        }
+    }
+    pub const fn new_dir() -> Self {
+        DiskINode {
+            size: 0,
+            type_: FileType::Dir,
+            nlinks: 0,
+            blocks: 0,
+            direct: [0; NDIRECT],
+            indirect: 0,
+            db_indirect: 0,
+        }
+    }
+}
+
 /// Convert structs to [u8] slice
 pub trait AsBuf {
     fn as_buf(&self) -> &[u8] {
diff --git a/src/tests.rs b/src/tests.rs
index 3c04e49..f6a5cb4 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -3,6 +3,7 @@ use std::io::{Read, Write, Seek, SeekFrom};
 use std::boxed::Box;
 use super::sfs::*;
 use super::vfs::*;
+use super::vfs::INode;
 
 impl Device for File {
     fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> Option<usize> {
@@ -32,11 +33,10 @@ fn test() {
     println!("{:?}", root);
 
     use super::structs::{DiskEntry, AsBuf};
-    use super::vfs::INode;
     use std::mem::uninitialized;
     let mut entry: DiskEntry = unsafe{uninitialized()};
     for i in 0 .. 23 {
-        root.borrow_mut().read_at(i * 4096, entry.as_buf_mut());
+        root.borrow_mut().read_at(i * 4096, entry.as_buf_mut()).unwrap();
         println!("{:?}", entry);
     }
 }
@@ -47,6 +47,7 @@ fn create() {
         .read(true).write(true).create(true).open("test.img")
         .expect("failed to create file");
     let sfs = SimpleFileSystem::create(Box::new(file), 16 * 4096);
-
-
+    let root = sfs.borrow_mut().root_inode();
+    let file1 = root.borrow_mut().create("file1").unwrap();
+    sfs.borrow_mut().sync().unwrap();
 }
\ No newline at end of file
diff --git a/src/vfs.rs b/src/vfs.rs
index 74b91e5..6f83a4f 100644
--- a/src/vfs.rs
+++ b/src/vfs.rs
@@ -1,34 +1,44 @@
 use alloc::rc::{Rc, Weak};
 use core::cell::RefCell;
+use core::mem::size_of;
+use core;
 
 /// Abstract operations on a inode.
 pub trait INode {
-    fn open(&mut self, flags: u32) -> Result<(), ()>;
-    fn close(&mut self) -> Result<(), ()>;
-    fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> Option<usize>;
-    fn write_at(&mut self, offset: usize, buf: &[u8]) -> Option<usize>;
-    fn info(&mut self) -> Result<FileInfo, ()>;
-    fn sync(&mut self) -> Result<(), ()>;
-//    fn name_file(&mut self) -> Result<(), ()>;
-//    fn reclaim(&mut self) -> Result<(), ()>;
-    fn type_(&self) -> Result<u32, ()>;
-//    fn try_seek(&mut self, offset: u64) -> Result<(), ()>;
-    fn resize(&mut self, len: usize) -> Result<(), ()>;
-//    fn create(&mut self, name: &'static str, excl: bool) -> Result<(), ()>;
-//    fn loopup(&mut self, path: &'static str) -> Result<(), ()>;
-//    fn io_ctrl(&mut self, op: u32, data: &[u8]) -> Result<(), ()>;
+    fn open(&mut self, flags: u32) -> Result<()>;
+    fn close(&mut self) -> Result<()>;
+    fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> Result<usize>;
+    fn write_at(&mut self, offset: usize, buf: &[u8]) -> Result<usize>;
+    fn info(&mut self) -> Result<FileInfo>;
+    fn sync(&mut self) -> Result<()>;
+//    fn name_file(&mut self) -> Result<()>;
+//    fn reclaim(&mut self) -> Result<()>;
+//    fn try_seek(&mut self, offset: u64) -> Result<()>;
+    fn resize(&mut self, len: usize) -> Result<()>;
+    fn create(&mut self, name: &'static str) -> Result<Rc<RefCell<INode>>>;
+    fn loopup(&mut self, path: &'static str) -> Result<Rc<RefCell<INode>>>;
+//    fn io_ctrl(&mut self, op: u32, data: &[u8]) -> Result<()>;
 }
 
+#[derive(Debug)]
 pub struct FileInfo {
     pub size: usize,
     pub mode: u32,
+    pub type_: FileType,
 }
 
+#[derive(Debug, Eq, PartialEq)]
+pub enum FileType {
+    File, Dir,
+}
+
+pub type Result<T> = core::result::Result<T, ()>;
+
 /// Abstract filesystem
 pub trait FileSystem {
     type INode: INode;
-    fn sync(&mut self) -> Result<(), ()>;
+    fn sync(&mut self) -> Result<()>;
     fn root_inode(&mut self) -> Rc<RefCell<Self::INode>>;
-    fn unmount(&mut self) -> Result<(), ()>;
+    fn unmount(&mut self) -> Result<()>;
     fn cleanup(&mut self);
 }
\ No newline at end of file