diff --git a/easy-fs-fuse/src/main.rs b/easy-fs-fuse/src/main.rs
index cf07b618..09e93456 100644
--- a/easy-fs-fuse/src/main.rs
+++ b/easy-fs-fuse/src/main.rs
@@ -61,7 +61,7 @@ fn easy_fs_pack() -> std::io::Result<()> {
     })));
     // 16MiB, at most 4095 files
     let efs = EasyFileSystem::create(
-        block_file.clone(),
+        block_file,
         16 * 2048,
         1,
     );
diff --git a/easy-fs/src/bitmap.rs b/easy-fs/src/bitmap.rs
index 4feaa9cf..5474e749 100644
--- a/easy-fs/src/bitmap.rs
+++ b/easy-fs/src/bitmap.rs
@@ -17,7 +17,7 @@ pub struct Bitmap {
 /// Return (block_pos, bits64_pos, inner_pos)
 fn decomposition(mut bit: usize) -> (usize, usize, usize) {
     let block_pos = bit / BLOCK_BITS;
-    bit = bit % BLOCK_BITS;
+    bit %= BLOCK_BITS;
     (block_pos, bit / 64, bit % 64)
 }
 
@@ -70,4 +70,4 @@ impl Bitmap {
     pub fn maximum(&self) -> usize {
         self.blocks * BLOCK_BITS
     }
-}
\ No newline at end of file
+}
diff --git a/easy-fs/src/layout.rs b/easy-fs/src/layout.rs
index c6f7b315..b5295de1 100644
--- a/easy-fs/src/layout.rs
+++ b/easy-fs/src/layout.rs
@@ -289,35 +289,26 @@ impl DiskInode {
         .lock()
         .modify(0, |indirect2: &mut IndirectBlock| {
             // full indirect1 blocks
-            for i in 0..a1 {
-                v.push(indirect2[i]);
-                get_block_cache(
-                    indirect2[i] as usize,
-                    Arc::clone(block_device),
-                )
-                .lock()
-                .modify(0, |indirect1: &mut IndirectBlock| {
-                    for j in 0..INODE_INDIRECT1_COUNT {
-                        v.push(indirect1[j]);
-                        //indirect1[j] = 0;
-                    }
-                });
-                //indirect2[i] = 0;
+            for entry in indirect2.iter_mut().take(a1) {
+                v.push(*entry);
+                get_block_cache(*entry as usize, Arc::clone(block_device))
+                    .lock()
+                    .modify(0, |indirect1: &mut IndirectBlock| {
+                        for entry in indirect1.iter() {
+                            v.push(*entry);
+                        }
+                    });
             }
             // last indirect1 block
             if b1 > 0 {
                 v.push(indirect2[a1]);
-                get_block_cache(
-                    indirect2[a1] as usize,
-                    Arc::clone(block_device),
-                )
-                .lock()
-                .modify(0, |indirect1: &mut IndirectBlock| {
-                    for j in 0..b1 {
-                        v.push(indirect1[j]);
-                        //indirect1[j] = 0;
-                    }
-                });
+                get_block_cache(indirect2[a1] as usize, Arc::clone(block_device))
+                    .lock()
+                    .modify(0, |indirect1: &mut IndirectBlock| {
+                        for entry in indirect1.iter().take(b1) {
+                            v.push(*entry);
+                        }
+                    });
                 //indirect2[a1] = 0;
             }
         });
@@ -445,4 +436,4 @@ impl DirEntry {
     pub fn inode_number(&self) -> u32 {
         self.inode_number
     }
-}
\ No newline at end of file
+}
diff --git a/easy-fs/src/vfs.rs b/easy-fs/src/vfs.rs
index 9534c39a..4dfd31b0 100644
--- a/easy-fs/src/vfs.rs
+++ b/easy-fs/src/vfs.rs
@@ -110,12 +110,13 @@ impl Inode {
 
     pub fn create(&self, name: &str) -> Option<Arc<Inode>> {
         let mut fs = self.fs.lock();
-        if self.modify_disk_inode(|root_inode| {
+        let op = |root_inode: &mut DiskInode| {
             // assert it is a directory
             assert!(root_inode.is_dir());
             // has the file been created?
             self.find_inode_id(name, root_inode)
-        }).is_some() {
+        };
+        if self.modify_disk_inode(op).is_some() {
             return None;
         }
         // create a new file
diff --git a/os/src/fs/pipe.rs b/os/src/fs/pipe.rs
index ed2dde15..08d51daf 100644
--- a/os/src/fs/pipe.rs
+++ b/os/src/fs/pipe.rs
@@ -78,12 +78,10 @@ impl PipeRingBuffer {
     pub fn available_read(&self) -> usize {
         if self.status == RingBufferStatus::EMPTY {
             0
+        } else if self.tail > self.head {
+            self.tail - self.head
         } else {
-            if self.tail > self.head {
-                self.tail - self.head
-            } else {
-                self.tail + RING_BUFFER_SIZE - self.head
-            }
+            self.tail + RING_BUFFER_SIZE - self.head
         }
     }
     pub fn available_write(&self) -> usize {
@@ -165,4 +163,4 @@ impl File for Pipe {
             }
         }
     }
-}
\ No newline at end of file
+}
diff --git a/os/src/mm/frame_allocator.rs b/os/src/mm/frame_allocator.rs
index 357db707..3afe336b 100644
--- a/os/src/mm/frame_allocator.rs
+++ b/os/src/mm/frame_allocator.rs
@@ -62,13 +62,11 @@ impl FrameAllocator for StackFrameAllocator {
     fn alloc(&mut self) -> Option<PhysPageNum> {
         if let Some(ppn) = self.recycled.pop() {
             Some(ppn.into())
+        } else if self.current == self.end {
+            None
         } else {
-            if self.current == self.end {
-                None
-            } else {
-                self.current += 1;
-                Some((self.current - 1).into())
-            }
+            self.current += 1;
+            Some((self.current - 1).into())
         }
     }
     fn dealloc(&mut self, ppn: PhysPageNum) {
@@ -131,4 +129,4 @@ pub fn frame_allocator_test() {
     }
     drop(v);
     println!("frame_allocator_test passed!");
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/cmdline_args.rs b/user/src/bin/cmdline_args.rs
index b49ec332..9a227456 100644
--- a/user/src/bin/cmdline_args.rs
+++ b/user/src/bin/cmdline_args.rs
@@ -9,8 +9,8 @@ extern crate user_lib;
 #[no_mangle]
 pub fn main(argc: usize, argv: &[&str]) -> i32 {
     println!("argc = {}", argc);
-    for i in 0..argc {
-        println!("argv[{}] = {}", i, argv[i]);
+    for (i, arg) in argv.iter().enumerate() {
+        println!("argv[{}] = {}", i, arg);
     }
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/huge_write.rs b/user/src/bin/huge_write.rs
index b00ca17b..4b0daaf8 100644
--- a/user/src/bin/huge_write.rs
+++ b/user/src/bin/huge_write.rs
@@ -15,8 +15,8 @@ use user_lib::{
 #[no_mangle]
 pub fn main() -> i32 {
     let mut buffer = [0u8; 1024]; // 1KiB
-    for i in 0..buffer.len() {
-        buffer[i] = i as u8;
+    for (i, ch) in buffer.iter_mut().enumerate() {
+        *ch = i as u8;
     }
     let f = open("testf\0", OpenFlags::CREATE | OpenFlags::WRONLY);
     if f < 0 {
diff --git a/user/src/bin/initproc.rs b/user/src/bin/initproc.rs
index a9b8048a..fba348cb 100644
--- a/user/src/bin/initproc.rs
+++ b/user/src/bin/initproc.rs
@@ -1,7 +1,6 @@
 #![no_std]
 #![no_main]
 
-#[macro_use]
 extern crate user_lib;
 
 use user_lib::{
@@ -14,7 +13,7 @@ use user_lib::{
 #[no_mangle]
 fn main() -> i32 {
     if fork() == 0 {
-        exec("user_shell\0", &[0 as *const u8]);
+        exec("user_shell\0", &[core::ptr::null::<u8>()]);
     } else {
         loop {
             let mut exit_code: i32 = 0;
diff --git a/user/src/bin/matrix.rs b/user/src/bin/matrix.rs
index 8f1357ea..c2461cf2 100644
--- a/user/src/bin/matrix.rs
+++ b/user/src/bin/matrix.rs
@@ -1,5 +1,6 @@
 #![no_std]
 #![no_main]
+#![allow(clippy::needless_range_loop)]
 
 #[macro_use]
 extern crate user_lib;
diff --git a/user/src/bin/pipe_large_test.rs b/user/src/bin/pipe_large_test.rs
index 121987be..6f4f5000 100644
--- a/user/src/bin/pipe_large_test.rs
+++ b/user/src/bin/pipe_large_test.rs
@@ -40,8 +40,8 @@ pub fn main() -> i32 {
         // close write end of up pipe
         close(up_pipe_fd[1]);
         // generate a long random string
-        for i in 0..LENGTH {
-            random_str[i] = get_time() as u8;
+        for ch in random_str.iter_mut() {
+            *ch = get_time() as u8;
         }
         // send it
         assert_eq!(write(down_pipe_fd[1], &random_str) as usize, random_str.len());
@@ -66,4 +66,4 @@ pub fn main() -> i32 {
         println!("pipe_large_test passed!");
         0
     }
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/run_pipe_test.rs b/user/src/bin/run_pipe_test.rs
index 000b82d5..f0f95b03 100644
--- a/user/src/bin/run_pipe_test.rs
+++ b/user/src/bin/run_pipe_test.rs
@@ -10,7 +10,7 @@ use user_lib::{fork, exec, wait};
 pub fn main() -> i32 {
     for i in 0..1000 {
         if fork() == 0 {
-            exec("pipe_large_test\0", &[0 as *const u8]);
+            exec("pipe_large_test\0", &[core::ptr::null::<u8>()]);
         } else {
             let mut _unused: i32 = 0;
             wait(&mut _unused);
@@ -18,4 +18,4 @@ pub fn main() -> i32 {
         }
     }
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/user_shell.rs b/user/src/bin/user_shell.rs
index 09c6ea8b..3514d549 100644
--- a/user/src/bin/user_shell.rs
+++ b/user/src/bin/user_shell.rs
@@ -1,5 +1,6 @@
 #![no_std]
 #![no_main]
+#![allow(clippy::println_empty_string)]
 
 extern crate alloc;
 
@@ -72,7 +73,7 @@ impl ProcessArguments {
             .iter()
             .map(|arg| arg.as_ptr())
             .collect();
-        args_addr.push(0 as *const u8);
+        args_addr.push(core::ptr::null::<u8>());
 
         Self {
             input,
@@ -105,10 +106,8 @@ pub fn main() -> i32 {
                             if !process_args.output.is_empty() { valid = false; }
                         } else if i == process_arguments_list.len() - 1 {
                             if !process_args.input.is_empty() { valid = false; }
-                        } else {
-                            if !process_args.output.is_empty() || !process_args.input.is_empty() {
-                                valid = false;
-                            }
+                        } else if !process_args.output.is_empty() || !process_args.input.is_empty() {
+                            valid = false;
                         }
                     }
                     if process_arguments_list.len() == 1 { valid = true; }
diff --git a/user/src/bin/usertests.rs b/user/src/bin/usertests.rs
index e8be6c45..83da4d59 100644
--- a/user/src/bin/usertests.rs
+++ b/user/src/bin/usertests.rs
@@ -26,7 +26,7 @@ pub fn main() -> i32 {
         println!("Usertests: Running {}", test);
         let pid = fork();
         if pid == 0 {
-            exec(*test, &[0 as *const u8]);
+            exec(*test, &[core::ptr::null::<u8>()]);
             panic!("unreachable!");
         } else {
             let mut exit_code: i32 = Default::default();
@@ -37,4 +37,4 @@ pub fn main() -> i32 {
     }
     println!("Usertests passed!");
     0
-}
\ No newline at end of file
+}