Add comments in ch6

os/src/fs/inode.rs

@@ -1,3 +1,9 @@
+//! `Arc<Inode>` -> `OSInodeInner`: In order to open files concurrently 
+//! we need to wrap `Inode` into `Arc`,but `Mutex` in `Inode` prevents 
+//! file systems from being accessed simultaneously 
+//! 
+//! `UPSafeCell<OSInodeInner>` -> `OSInode`: for static `ROOT_INODE`,we 
+//! need to wrap `OSInodeInner` into `UPSafeCell`
 use super::File;
 use crate::drivers::BLOCK_DEVICE;
 use crate::mm::UserBuffer;
@@ -7,19 +13,21 @@ use alloc::vec::Vec;
 use bitflags::*;
 use easy_fs::{EasyFileSystem, Inode};
 use lazy_static::*;
-
+/// A wrapper around a filesystem inode
+/// to implement File trait atop 
 pub struct OSInode {
     readable: bool,
     writable: bool,
     inner: UPSafeCell<OSInodeInner>,
 }
-
+/// The OS inode inner in 'UPSafeCell'
 pub struct OSInodeInner {
     offset: usize,
     inode: Arc<Inode>,
 }
 
 impl OSInode {
+    /// Construct an OS inode from a inode
     pub fn new(readable: bool, writable: bool, inode: Arc<Inode>) -> Self {
         Self {
             readable,
@@ -27,6 +35,7 @@ impl OSInode {
             inner: unsafe { UPSafeCell::new(OSInodeInner { offset: 0, inode }) },
         }
     }
+    /// Read all data inside a inode into vector
     pub fn read_all(&self) -> Vec<u8> {
         let mut inner = self.inner.exclusive_access();
         let mut buffer = [0u8; 512];
@@ -49,7 +58,7 @@ lazy_static! {
         Arc::new(EasyFileSystem::root_inode(&efs))
     };
 }
-
+/// List all files in the filesystems
 pub fn list_apps() {
     println!("/**** APPS ****");
     for app in ROOT_INODE.ls() {
@@ -58,12 +67,18 @@ pub fn list_apps() {
     println!("**************/");
 }
 
-bitflags! {
+bitflags! {    
+    ///Open file flags
     pub struct OpenFlags: u32 {
+        ///Read only
         const RDONLY = 0;
+        ///Write only
         const WRONLY = 1 << 0;
+        ///Read & Write
         const RDWR = 1 << 1;
+        ///Allow create
         const CREATE = 1 << 9;
+        ///Clear file and return an empty one
         const TRUNC = 1 << 10;
     }
 }
@@ -81,7 +96,7 @@ impl OpenFlags {
         }
     }
 }
-
+///Open file with flags
 pub fn open_file(name: &str, flags: OpenFlags) -> Option<Arc<OSInode>> {
     let (readable, writable) = flags.read_write();
     if flags.contains(OpenFlags::CREATE) {