Add support for close syscall

src/services/libs/jinux-std/src/fs/file_handle/file.rs

@@ -28,4 +28,8 @@ pub trait File: Send + Sync + Any {
     fn poll(&self) -> IoEvents {
         IoEvents::empty()
     }
+
+    fn flush(&self) -> Result<()> {
+        Ok(())
+    }
 }

src/services/libs/jinux-std/src/fs/file_handle/mod.rs

@@ -6,6 +6,7 @@ mod inode_handle;
 use crate::prelude::*;
 use crate::rights::{ReadOp, WriteOp};
 use alloc::sync::Arc;
+use core::ops::Range;
 
 pub use self::file::File;
 pub use self::inode_handle::InodeHandle;
@@ -65,4 +66,20 @@ impl FileHandle {
             }
         }
     }
+
+    pub fn clean_for_close(&self) -> Result<()> {
+        match &self.inner {
+            Inner::Inode(inode_handle) => {
+                let dentry = inode_handle.dentry();
+                let ref_count = Arc::strong_count(dentry);
+                // The dentry is held by dentry cache and self
+                if ref_count == 2 {
+                    let page_cache_size = dentry.vnode().pages().size();
+                    dentry.vnode().pages().decommit(0..page_cache_size)?;
+                }
+            }
+            Inner::File(file) => file.flush()?,
+        }
+        Ok(())
+    }
 }

src/services/libs/jinux-std/src/fs/file_table.rs

@@ -58,8 +58,8 @@ impl FileTable {
         fd
     }
 
-    pub fn close_file(&mut self, fd: FileDescripter) {
-        self.table.remove(&fd);
+    pub fn close_file(&mut self, fd: FileDescripter) -> Option<FileHandle> {
+        self.table.remove(&fd)
     }
 
     pub fn get_file(&self, fd: FileDescripter) -> Result<&FileHandle> {

src/services/libs/jinux-std/src/syscall/close.rs

@@ -9,6 +9,7 @@ pub fn sys_close(fd: FileDescripter) -> Result<SyscallReturn> {
     let current = current!();
     let mut file_table = current.file_table().lock();
     let _ = file_table.get_file(fd)?;
-    file_table.close_file(fd);
+    let file = file_table.close_file(fd).unwrap();
+    file.clean_for_close()?;
     Ok(SyscallReturn::Return(0))
 }