diff --git a/Cargo.toml b/Cargo.toml
index d22438a..f71ba8b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,5 +1,7 @@
 [workspace]
 members = [
     "rcore-fs",
+    "rcore-fs-sfs",
+    "rcore-fs-sefs",
     "rcore-fs-fuse"
 ]
\ No newline at end of file
diff --git a/rcore-fs-fuse/Cargo.toml b/rcore-fs-fuse/Cargo.toml
index 23ba98f..870fe3f 100644
--- a/rcore-fs-fuse/Cargo.toml
+++ b/rcore-fs-fuse/Cargo.toml
@@ -12,3 +12,5 @@ fuse = "0.3"
 structopt = "0.2"
 env_logger = "0.3"
 rcore-fs = { path = "../rcore-fs", features = ["std"] }
+rcore-fs-sfs = { path = "../rcore-fs-sfs", features = ["std"] }
+rcore-fs-sefs = { path = "../rcore-fs-sefs", features = ["std"] }
diff --git a/rcore-fs-fuse/src/main.rs b/rcore-fs-fuse/src/main.rs
index 5f373a0..765680f 100644
--- a/rcore-fs-fuse/src/main.rs
+++ b/rcore-fs-fuse/src/main.rs
@@ -9,7 +9,9 @@ use fuse::{FileAttr, Filesystem, FileType, ReplyAttr, ReplyData, ReplyDirectory,
 use structopt::StructOpt;
 use time::Timespec;
 
-use rcore_fs::{sfs, sefs, vfs};
+use rcore_fs::vfs;
+use rcore_fs_sfs as sfs;
+use rcore_fs_sefs as sefs;
 
 const TTL: Timespec = Timespec { sec: 1, nsec: 0 };                     // 1 second
 
@@ -230,12 +232,12 @@ fn main() {
 //    let img = OpenOptions::new().read(true).write(true).open(&opt.image)
 //        .expect("failed to open image");
     let sfs = if opt.image.is_dir() {
-        let img = sefs::std_impl::StdStorage::new(&opt.image);
+        let img = sefs::dev::StdStorage::new(&opt.image);
         sefs::SEFS::open(Box::new(img))
             .expect("failed to open sefs")
     } else {
         std::fs::create_dir_all(&opt.image).unwrap();
-        let img = sefs::std_impl::StdStorage::new(&opt.image);
+        let img = sefs::dev::StdStorage::new(&opt.image);
         sefs::SEFS::create(Box::new(img))
             .expect("failed to create sefs")
     };
diff --git a/rcore-fs-sefs/Cargo.toml b/rcore-fs-sefs/Cargo.toml
new file mode 100644
index 0000000..e5d74c8
--- /dev/null
+++ b/rcore-fs-sefs/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+name = "rcore-fs-sefs"
+version = "0.1.0"
+authors = ["WangRunji <wangrunji0408@163.com>"]
+edition = "2018"
+
+[dependencies]
+rcore-fs = { path = "../rcore-fs" }
+static_assertions = "0.3"
+spin = "0.4"
+log = "0.4"
+
+[dependencies.bitvec]
+version = "0.9"
+default-features = false
+features = ["alloc"]
+
+[features]
+std = ["rcore-fs/std"]
diff --git a/rcore-fs-sefs/src/dev/mod.rs b/rcore-fs-sefs/src/dev/mod.rs
new file mode 100644
index 0000000..8cd51e7
--- /dev/null
+++ b/rcore-fs-sefs/src/dev/mod.rs
@@ -0,0 +1,44 @@
+use alloc::boxed::Box;
+
+use rcore_fs::vfs::FsError;
+
+pub use self::std_impl::*;
+
+mod std_impl;
+
+/// A file stores a normal file or directory.
+///
+/// The interface is same as `std::fs::File`.
+pub trait File: Send + Sync {
+    fn read_at(&self, buf: &mut [u8], offset: usize) -> DevResult<usize>;
+    fn write_at(&self, buf: &[u8], offset: usize) -> DevResult<usize>;
+    fn set_len(&self, len: usize) -> DevResult<()>;
+    fn flush(&self) -> DevResult<()>;
+
+    fn read_exact_at(&self, buf: &mut [u8], offset: usize) -> DevResult<()> {
+        let len = self.read_at(buf, offset)?;
+        if len == buf.len() { Ok(()) } else { Err(DeviceError) }
+    }
+    fn write_all_at(&self, buf: &[u8], offset: usize) -> DevResult<()> {
+        let len = self.write_at(buf, offset)?;
+        if len == buf.len() { Ok(()) } else { Err(DeviceError) }
+    }
+}
+
+/// The collection of all files in the FS.
+pub trait Storage: Send + Sync {
+    fn open(&self, file_id: usize) -> DevResult<Box<File>>;
+    fn create(&self, file_id: usize) -> DevResult<Box<File>>;
+    fn remove(&self, file_id: usize) -> DevResult<()>;
+}
+
+#[derive(Debug)]
+pub struct DeviceError;
+
+pub type DevResult<T> = Result<T, DeviceError>;
+
+impl From<DeviceError> for FsError {
+    fn from(_: DeviceError) -> Self {
+        FsError::DeviceError
+    }
+}
diff --git a/rcore-fs/src/sefs/std_impl.rs b/rcore-fs-sefs/src/dev/std_impl.rs
similarity index 100%
rename from rcore-fs/src/sefs/std_impl.rs
rename to rcore-fs-sefs/src/dev/std_impl.rs
diff --git a/rcore-fs/src/sefs/mod.rs b/rcore-fs-sefs/src/lib.rs
similarity index 93%
rename from rcore-fs/src/sefs/mod.rs
rename to rcore-fs-sefs/src/lib.rs
index ef1c09e..74f4f0c 100644
--- a/rcore-fs/src/sefs/mod.rs
+++ b/rcore-fs-sefs/src/lib.rs
@@ -1,56 +1,25 @@
+#![cfg_attr(not(any(test, feature = "std")), no_std)]
+#![feature(alloc)]
+
+extern crate alloc;
+
 use alloc::{boxed::Box, collections::BTreeMap, string::String, sync::{Arc, Weak}, vec::Vec};
 use core::any::Any;
 use core::fmt::{Debug, Error, Formatter};
 use core::mem::uninitialized;
 
 use bitvec::BitVec;
-use log::*;
-use spin::{Mutex, RwLock};
+//use log::*;
+use spin::RwLock;
 
-use crate::dirty::Dirty;
-use crate::vfs::{self, FileSystem, FsError, INode, Timespec};
+use rcore_fs::dirty::Dirty;
+use rcore_fs::vfs::{self, FileSystem, FsError, INode, Timespec};
 
+use self::dev::*;
 use self::structs::*;
 
 mod structs;
-pub mod std_impl;
-
-/// A file stores a normal file or directory.
-///
-/// The interface is same as `std::fs::File`.
-pub trait File: Send + Sync {
-    fn read_at(&self, buf: &mut [u8], offset: usize) -> DevResult<usize>;
-    fn write_at(&self, buf: &[u8], offset: usize) -> DevResult<usize>;
-    fn set_len(&self, len: usize) -> DevResult<()>;
-    fn flush(&self) -> DevResult<()>;
-
-    fn read_exact_at(&self, buf: &mut [u8], offset: usize) -> DevResult<()> {
-        let len = self.read_at(buf, offset)?;
-        if len == buf.len() { Ok(()) } else { Err(DeviceError) }
-    }
-    fn write_all_at(&self, buf: &[u8], offset: usize) -> DevResult<()> {
-        let len = self.write_at(buf, offset)?;
-        if len == buf.len() { Ok(()) } else { Err(DeviceError) }
-    }
-}
-
-/// The collection of all files in the FS.
-pub trait Storage: Send + Sync {
-    fn open(&self, file_id: usize) -> DevResult<Box<File>>;
-    fn create(&self, file_id: usize) -> DevResult<Box<File>>;
-    fn remove(&self, file_id: usize) -> DevResult<()>;
-}
-
-#[derive(Debug)]
-pub struct DeviceError;
-
-pub type DevResult<T> = Result<T, DeviceError>;
-
-impl From<DeviceError> for FsError {
-    fn from(_: DeviceError) -> Self {
-        FsError::DeviceError
-    }
-}
+pub mod dev;
 
 /// Helper methods for `File`
 impl File {
@@ -413,7 +382,7 @@ impl Drop for INodeImpl {
         if self.disk_inode.read().nlinks <= 0 {
             self.disk_inode.write().sync();
             self.fs.free_block(self.id);
-            self.fs.device.remove(self.id);
+            self.fs.device.remove(self.id).unwrap();
         }
     }
 }
diff --git a/rcore-fs/src/sefs/structs.rs b/rcore-fs-sefs/src/structs.rs
similarity index 100%
rename from rcore-fs/src/sefs/structs.rs
rename to rcore-fs-sefs/src/structs.rs
diff --git a/rcore-fs-sfs/Cargo.toml b/rcore-fs-sfs/Cargo.toml
new file mode 100644
index 0000000..eefe8bf
--- /dev/null
+++ b/rcore-fs-sfs/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "rcore-fs-sfs"
+version = "0.1.0"
+authors = ["WangRunji <wangrunji0408@163.com>"]
+edition = "2018"
+
+[[bin]]
+name = "mksfs"
+path = "src/bin/mksfs.rs"
+required-features = ["std"]
+
+[dependencies]
+rcore-fs = { path = "../rcore-fs" }
+static_assertions = "0.3"
+spin = "0.4"
+log = "0.4"
+
+[dependencies.bitvec]
+version = "0.9"
+default-features = false
+features = ["alloc"]
+
+[features]
+std = ["rcore-fs/std"]
diff --git a/rcore-fs/src/bin/mksfs.rs b/rcore-fs-sfs/src/bin/mksfs.rs
similarity index 95%
rename from rcore-fs/src/bin/mksfs.rs
rename to rcore-fs-sfs/src/bin/mksfs.rs
index ec8910e..60f7bd5 100644
--- a/rcore-fs/src/bin/mksfs.rs
+++ b/rcore-fs-sfs/src/bin/mksfs.rs
@@ -3,8 +3,10 @@ use std::fs;
 use std::io::{Read, Write, Result};
 use std::path::Path;
 use std::mem::uninitialized;
-use std::sync::Arc;
-use rcore_fs::{sfs::SimpleFileSystem, vfs::*};
+use std::sync::{Arc, Mutex};
+
+use rcore_fs::vfs::*;
+use rcore_fs_sfs::SimpleFileSystem;
 
 fn main() -> Result<()> {
     let args: Vec<_> = env::args().collect();
@@ -23,6 +25,7 @@ fn main() -> Result<()> {
 
 fn zip(path: &Path, img_path: &Path) -> Result<()> {
     let img = fs::OpenOptions::new().read(true).write(true).create(true).open(img_path)?;
+    let img = Mutex::new(img);
     let sfs = SimpleFileSystem::create(Box::new(img), 0x1000000);
     let inode = sfs.root_inode();
     zip_dir(path, inode)?;
@@ -59,6 +62,7 @@ fn zip_dir(path: &Path, inode: Arc<INode>) -> Result<()> {
 
 fn unzip(path: &Path, img_path: &Path) -> Result<()> {
     let img = fs::File::open(img_path)?;
+    let img = Mutex::new(img);
     let sfs = SimpleFileSystem::open(Box::new(img)).expect("Failed to open sfs");
     let inode = sfs.root_inode();
     fs::create_dir(&path)?;
diff --git a/rcore-fs/src/sfs/mod.rs b/rcore-fs-sfs/src/lib.rs
similarity index 94%
rename from rcore-fs/src/sfs/mod.rs
rename to rcore-fs-sfs/src/lib.rs
index 511f787..4ebef13 100644
--- a/rcore-fs/src/sfs/mod.rs
+++ b/rcore-fs-sfs/src/lib.rs
@@ -1,3 +1,9 @@
+#![cfg_attr(not(any(test, feature = "std")), no_std)]
+#![feature(alloc)]
+#![feature(const_str_len)]
+
+extern crate alloc;
+
 use alloc::{boxed::Box, collections::BTreeMap, string::String, sync::{Arc, Weak}, vec::Vec};
 use core::any::Any;
 use core::fmt::{Debug, Error, Formatter};
@@ -5,34 +11,26 @@ use core::mem::uninitialized;
 
 use bitvec::BitVec;
 use log::*;
-use spin::{Mutex, RwLock};
+use spin::RwLock;
 
-use crate::dirty::Dirty;
-use crate::util::*;
-use crate::vfs::{self, FileSystem, FsError, INode, Timespec};
+use rcore_fs::dev::Device;
+use rcore_fs::dirty::Dirty;
+use rcore_fs::util::*;
+use rcore_fs::vfs::{self, FileSystem, FsError, INode, Timespec};
 
 use self::structs::*;
 
 mod structs;
-mod std_impl;
-mod blocked_device;
-
-/// Interface for FS to read & write
-///     TODO: use std::io::{Read, Write}
-pub trait Device: Send {
-    fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> Option<usize>;
-    fn write_at(&mut self, offset: usize, buf: &[u8]) -> Option<usize>;
-}
 
-impl Device {
-    fn read_block(&mut self, id: BlockId, offset: usize, buf: &mut [u8]) -> vfs::Result<()> {
+trait DeviceExt: Device {
+    fn read_block(&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(()),
             _ => panic!(),
         }
     }
-    fn write_block(&mut self, id: BlockId, offset: usize, buf: &[u8]) -> vfs::Result<()> {
+    fn write_block(&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(()),
@@ -40,12 +38,14 @@ impl Device {
         }
     }
     /// Load struct `T` from given block in device
-    fn load_struct<T: AsBuf>(&mut self, id: BlockId) -> vfs::Result<T> {
+    fn load_struct<T: AsBuf>(&self, id: BlockId) -> vfs::Result<T> {
         let mut s: T = unsafe { uninitialized() };
         self.read_block(id, 0, s.as_buf_mut()).map(|_|{s})
     }
 }
 
+impl DeviceExt for Device {}
+
 /// inode for sfs
 pub struct INodeImpl {
     /// inode number
@@ -73,7 +73,7 @@ impl INodeImpl {
                 Ok(disk_inode.direct[id] as BlockId),
             id if id < NDIRECT + BLK_NENTRY => {
                 let mut disk_block_id: u32 = 0;
-                self.fs.device.lock().read_block(
+                self.fs.device.read_block(
                     disk_inode.indirect as usize,
                     ENTRY_SIZE * (id - NDIRECT),
                     disk_block_id.as_buf_mut(),
@@ -93,7 +93,7 @@ impl INodeImpl {
             }
             id if id < NDIRECT + BLK_NENTRY => {
                 let disk_block_id = disk_block_id as u32;
-                self.fs.device.lock().write_block(
+                self.fs.device.write_block(
                     self.disk_inode.read().indirect as usize,
                     ENTRY_SIZE * (id - NDIRECT),
                     disk_block_id.as_buf(),
@@ -215,7 +215,7 @@ impl INodeImpl {
     // Note: the _\w*_at method always return begin>size?0:begin<end?0:(min(size,end)-begin) when success
     /// 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(&mut Box<Device>, &BlockRange, usize) -> vfs::Result<()>
+        where F: FnMut(&Box<Device>, &BlockRange, usize) -> vfs::Result<()>
     {
         let size = self._size();
         let iter = BlockIter {
@@ -228,7 +228,7 @@ impl INodeImpl {
         let mut buf_offset = 0usize;
         for mut range in iter {
             range.block = self.get_disk_block_id(range.block)?;
-            f(&mut *self.fs.device.lock(), &range, buf_offset)?;
+            f(&self.fs.device, &range, buf_offset)?;
             buf_offset += range.len();
         }
         Ok(buf_offset)
@@ -299,7 +299,7 @@ impl vfs::INode for INodeImpl {
     fn sync(&self) -> vfs::Result<()> {
         let mut disk_inode = self.disk_inode.write();
         if disk_inode.dirty() {
-            self.fs.device.lock().write_block(self.id, 0, disk_inode.as_buf())?;
+            self.fs.device.write_block(self.id, 0, disk_inode.as_buf())?;
             disk_inode.sync();
         }
         Ok(())
@@ -543,14 +543,14 @@ pub struct SimpleFileSystem {
     /// inode list
     inodes: RwLock<BTreeMap<INodeId, Weak<INodeImpl>>>,
     /// device
-    device: Mutex<Box<Device>>,
+    device: Box<Device>,
     /// Pointer to self, used by INodes
     self_ptr: Weak<SimpleFileSystem>,
 }
 
 impl SimpleFileSystem {
     /// Load SFS from device
-    pub fn open(mut device: Box<Device>) -> vfs::Result<Arc<Self>> {
+    pub fn open(device: Box<Device>) -> vfs::Result<Arc<Self>> {
         let super_block = device.load_struct::<SuperBlock>(BLKN_SUPER).unwrap();
         if !super_block.check() {
             return Err(FsError::WrongFs);
@@ -561,7 +561,7 @@ impl SimpleFileSystem {
             super_block: RwLock::new(Dirty::new(super_block)),
             free_map: RwLock::new(Dirty::new(BitVec::from(free_map.as_ref()))),
             inodes: RwLock::new(BTreeMap::new()),
-            device: Mutex::new(device),
+            device,
             self_ptr: Weak::default(),
         }.wrap())
     }
@@ -589,7 +589,7 @@ impl SimpleFileSystem {
             super_block: RwLock::new(Dirty::new_dirty(super_block)),
             free_map: RwLock::new(Dirty::new_dirty(free_map)),
             inodes: RwLock::new(BTreeMap::new()),
-            device: Mutex::new(device),
+            device,
             self_ptr: Weak::default(),
         }.wrap();
 
@@ -661,7 +661,7 @@ impl SimpleFileSystem {
             }
         }
         // Load if not in set, or is weak ref.
-        let disk_inode = Dirty::new(self.device.lock().load_struct::<DiskINode>(id).unwrap());
+        let disk_inode = Dirty::new(self.device.load_struct::<DiskINode>(id).unwrap());
         self._new_inode(id, disk_inode)
     }
     /// Create a new INode file
@@ -694,12 +694,12 @@ impl vfs::FileSystem for SimpleFileSystem {
     fn sync(&self) -> vfs::Result<()> {
         let mut super_block = self.super_block.write();
         if super_block.dirty() {
-            self.device.lock().write_at(BLKSIZE * BLKN_SUPER, super_block.as_buf()).unwrap();
+            self.device.write_at(BLKSIZE * BLKN_SUPER, super_block.as_buf()).unwrap();
             super_block.sync();
         }
         let mut free_map = self.free_map.write();
         if free_map.dirty() {
-            self.device.lock().write_at(BLKSIZE * BLKN_FREEMAP, free_map.as_buf()).unwrap();
+            self.device.write_at(BLKSIZE * BLKN_FREEMAP, free_map.as_buf()).unwrap();
             free_map.sync();
         }
         self.flush_weak_inodes();
diff --git a/rcore-fs/src/sfs/structs.rs b/rcore-fs-sfs/src/structs.rs
similarity index 100%
rename from rcore-fs/src/sfs/structs.rs
rename to rcore-fs-sfs/src/structs.rs
diff --git a/rcore-fs/Cargo.toml b/rcore-fs/Cargo.toml
index 63b98a7..1b47bb5 100644
--- a/rcore-fs/Cargo.toml
+++ b/rcore-fs/Cargo.toml
@@ -4,21 +4,6 @@ version = "0.1.0"
 authors = ["WangRunji <wangrunji0408@163.com>", "Ben Pig Chu <benpichu@gmail.com>"]
 edition = "2018"
 
-[[bin]]
-name = "mksfs"
-path = "src/bin/mksfs.rs"
-required-features = ["std"]
-
-[dependencies]
-static_assertions = "0.3"
-spin = "0.4"
-log = "0.4"
-
-[dependencies.bitvec]
-version = "0.9"
-default-features = false
-features = ["alloc"]
-
 [dev-dependencies]
 tempfile = "3"
 
diff --git a/rcore-fs/src/sfs/blocked_device.rs b/rcore-fs/src/dev/mod.rs
similarity index 62%
rename from rcore-fs/src/sfs/blocked_device.rs
rename to rcore-fs/src/dev/mod.rs
index 472b326..a871423 100644
--- a/rcore-fs/src/sfs/blocked_device.rs
+++ b/rcore-fs/src/dev/mod.rs
@@ -1,11 +1,19 @@
 use crate::util::*;
-use super::Device;
+
+mod std_impl;
+
+/// Interface for FS to read & write
+///     TODO: use std::io::{Read, Write}
+pub trait Device: Send + Sync {
+    fn read_at(&self, offset: usize, buf: &mut [u8]) -> Option<usize>;
+    fn write_at(&self, offset: usize, buf: &[u8]) -> Option<usize>;
+}
 
 /// Device which can only R/W in blocks
-pub trait BlockedDevice: Send {
+pub trait BlockDevice: Send + Sync {
     const BLOCK_SIZE_LOG2: u8;
-    fn read_at(&mut self, block_id: usize, buf: &mut [u8]) -> bool;
-    fn write_at(&mut self, block_id: usize, buf: &[u8]) -> bool;
+    fn read_at(&self, block_id: usize, buf: &mut [u8]) -> bool;
+    fn write_at(&self, block_id: usize, buf: &[u8]) -> bool;
 }
 
 macro_rules! try0 {
@@ -14,9 +22,9 @@ macro_rules! try0 {
     };
 }
 
-/// Helper functions to R/W BlockedDevice in bytes
-impl<T: BlockedDevice> Device for T {
-    fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> Option<usize> {
+/// Helper functions to R/W BlockDevice in bytes
+impl<T: BlockDevice> Device for T {
+    fn read_at(&self, offset: usize, buf: &mut [u8]) -> Option<usize> {
         let iter = BlockIter {
             begin: offset,
             end: offset + buf.len(),
@@ -29,13 +37,13 @@ impl<T: BlockedDevice> Device for T {
             let buf = &mut buf[range.origin_begin() - offset..range.origin_end() - offset];
             if range.is_full() {
                 // Read to target buf directly
-                try0!(len, BlockedDevice::read_at(self, range.block, buf));
+                try0!(len, BlockDevice::read_at(self, range.block, buf));
             } else {
                 use core::mem::uninitialized;
                 let mut block_buf: [u8; 4096] = unsafe { uninitialized() };
                 assert!(Self::BLOCK_SIZE_LOG2 <= 12);
                 // Read to local buf first
-                try0!(len, BlockedDevice::read_at(self, range.block, &mut block_buf));
+                try0!(len, BlockDevice::read_at(self, range.block, &mut block_buf));
                 // Copy to target buf then
                 buf.copy_from_slice(&mut block_buf[range.begin..range.end]);
             }
@@ -43,7 +51,7 @@ impl<T: BlockedDevice> Device for T {
         Some(buf.len())
     }
 
-    fn write_at(&mut self, offset: usize, buf: &[u8]) -> Option<usize> {
+    fn write_at(&self, offset: usize, buf: &[u8]) -> Option<usize> {
         let iter = BlockIter {
             begin: offset,
             end: offset + buf.len(),
@@ -56,17 +64,17 @@ impl<T: BlockedDevice> Device for T {
             let buf = &buf[range.origin_begin() - offset..range.origin_end() - offset];
             if range.is_full() {
                 // Write to target buf directly
-                try0!(len, BlockedDevice::write_at(self, range.block, buf));
+                try0!(len, BlockDevice::write_at(self, range.block, buf));
             } else {
                 use core::mem::uninitialized;
                 let mut block_buf: [u8; 4096] = unsafe { uninitialized() };
                 assert!(Self::BLOCK_SIZE_LOG2 <= 12);
                 // Read to local buf first
-                try0!(len, BlockedDevice::read_at(self, range.block, &mut block_buf));
+                try0!(len, BlockDevice::read_at(self, range.block, &mut block_buf));
                 // Write to local buf
                 block_buf[range.begin..range.end].copy_from_slice(buf);
                 // Write back to target buf
-                try0!(len, BlockedDevice::write_at(self, range.block, &block_buf));
+                try0!(len, BlockDevice::write_at(self, range.block, &block_buf));
             }
         }
         Some(buf.len())
@@ -76,65 +84,66 @@ impl<T: BlockedDevice> Device for T {
 #[cfg(test)]
 mod test {
     use super::*;
+    use std::sync::Mutex;
 
-    impl BlockedDevice for [u8; 16] {
+    impl BlockDevice for Mutex<[u8; 16]> {
         const BLOCK_SIZE_LOG2: u8 = 2;
-        fn read_at(&mut self, block_id: usize, buf: &mut [u8]) -> bool {
+        fn read_at(&self, block_id: usize, buf: &mut [u8]) -> bool {
             if block_id >= 4 {
                 return false;
             }
             let begin = block_id << 2;
-            buf[..4].copy_from_slice(&mut self[begin..begin + 4]);
+            buf[..4].copy_from_slice(&mut self.lock()[begin..begin + 4]);
             true
         }
-        fn write_at(&mut self, block_id: usize, buf: &[u8]) -> bool {
+        fn write_at(&self, block_id: usize, buf: &[u8]) -> bool {
             if block_id >= 4 {
                 return false;
             }
             let begin = block_id << 2;
-            self[begin..begin + 4].copy_from_slice(&buf[..4]);
+            self.lock()[begin..begin + 4].copy_from_slice(&buf[..4]);
             true
         }
     }
 
     #[test]
     fn read() {
-        let mut buf: [u8; 16] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
+        let buf: Mutex<[u8; 16]> = Mutex::new([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);
         let mut res: [u8; 6] = [0; 6];
 
         // all inside
-        let ret = Device::read_at(&mut buf, 3, &mut res);
+        let ret = Device::read_at(&buf, 3, &mut res);
         assert_eq!(ret, Some(6));
         assert_eq!(res, [3, 4, 5, 6, 7, 8]);
 
         // partly inside
-        let ret = Device::read_at(&mut buf, 11, &mut res);
+        let ret = Device::read_at(&buf, 11, &mut res);
         assert_eq!(ret, Some(5));
         assert_eq!(res, [11, 12, 13, 14, 15, 8]);
 
         // all outside
-        let ret = Device::read_at(&mut buf, 16, &mut res);
+        let ret = Device::read_at(&buf, 16, &mut res);
         assert_eq!(ret, Some(0));
         assert_eq!(res, [11, 12, 13, 14, 15, 8]);
     }
 
     #[test]
     fn write() {
-        let mut buf: [u8; 16] = [0; 16];
+        let buf: Mutex<[u8; 16]> = Mutex::new([0; 16]);
         let res: [u8; 6] = [3, 4, 5, 6, 7, 8];
 
         // all inside
-        let ret = Device::write_at(&mut buf, 3, &res);
+        let ret = Device::write_at(&buf, 3, &res);
         assert_eq!(ret, Some(6));
         assert_eq!(buf, [0, 0, 0, 3, 4, 5, 6, 7, 8, 0, 0, 0, 0, 0, 0, 0]);
 
         // partly inside
-        let ret = Device::write_at(&mut buf, 11, &res);
+        let ret = Device::write_at(&buf, 11, &res);
         assert_eq!(ret, Some(5));
         assert_eq!(buf, [0, 0, 0, 3, 4, 5, 6, 7, 8, 0, 0, 3, 4, 5, 6, 7]);
 
         // all outside
-        let ret = Device::write_at(&mut buf, 16, &res);
+        let ret = Device::write_at(&buf, 16, &res);
         assert_eq!(ret, Some(0));
         assert_eq!(buf, [0, 0, 0, 3, 4, 5, 6, 7, 8, 0, 0, 3, 4, 5, 6, 7]);
     }
diff --git a/rcore-fs/src/dev/std_impl.rs b/rcore-fs/src/dev/std_impl.rs
new file mode 100644
index 0000000..d58e628
--- /dev/null
+++ b/rcore-fs/src/dev/std_impl.rs
@@ -0,0 +1,27 @@
+#![cfg(any(test, feature = "std"))]
+
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom, Write};
+use std::sync::Mutex;
+
+use super::Device;
+
+impl Device for Mutex<File> {
+    fn read_at(&self, offset: usize, buf: &mut [u8]) -> Option<usize> {
+        let offset = offset as u64;
+        let mut file = self.lock().unwrap();
+        match file.seek(SeekFrom::Start(offset)) {
+            Ok(real_offset) if real_offset == offset => file.read(buf).ok(),
+            _ => None,
+        }
+    }
+
+    fn write_at(&self, offset: usize, buf: &[u8]) -> Option<usize> {
+        let offset = offset as u64;
+        let mut file = self.lock().unwrap();
+        match file.seek(SeekFrom::Start(offset)) {
+            Ok(real_offset) if real_offset == offset => file.write(buf).ok(),
+            _ => None,
+        }
+    }
+}
\ No newline at end of file
diff --git a/rcore-fs/src/lib.rs b/rcore-fs/src/lib.rs
index e8938fc..1da365c 100644
--- a/rcore-fs/src/lib.rs
+++ b/rcore-fs/src/lib.rs
@@ -4,11 +4,10 @@
 
 extern crate alloc;
 
-mod dirty;
-mod util;
+pub mod dirty;
+pub mod util;
 pub mod vfs;
-pub mod sfs;
-pub mod sefs;
+pub mod dev;
 pub mod file;
 #[cfg(test)]
 mod tests;
diff --git a/rcore-fs/src/sfs/std_impl.rs b/rcore-fs/src/sfs/std_impl.rs
deleted file mode 100644
index 0025ff9..0000000
--- a/rcore-fs/src/sfs/std_impl.rs
+++ /dev/null
@@ -1,23 +0,0 @@
-#![cfg(any(test, feature = "std"))]
-
-use std::fs::File;
-use std::io::{Read, Write, Seek, SeekFrom};
-use super::Device;
-
-impl Device for File {
-    fn read_at(&mut self, offset: usize, buf: &mut [u8]) -> Option<usize> {
-        let offset = offset as u64;
-        match self.seek(SeekFrom::Start(offset)) {
-            Ok(real_offset) if real_offset == offset => self.read(buf).ok(),
-            _ => None,
-        }
-    }
-
-    fn write_at(&mut self, offset: usize, buf: &[u8]) -> Option<usize> {
-        let offset = offset as u64;
-        match self.seek(SeekFrom::Start(offset)) {
-            Ok(real_offset) if real_offset == offset => self.write(buf).ok(),
-            _ => None,
-        }
-    }
-}
\ No newline at end of file