ch6: fix fd in fork

Author: lythesia

os/src/fs/inode.rs

@@ -62,7 +62,17 @@ impl OSInode {
     }
 
     pub fn copy(&self) -> Self {
-        Self::new(self.readable, self.writable, self.clone_inner_inode())
+        let inner = self.inner.exclusive_access();
+        Self {
+            readable: self.readable,
+            writable: self.writable,
+            inner: unsafe {
+                UPSafeCell::new(OSInodeInner {
+                    offset: inner.offset,
+                    inode: inner.inode.clone(),
+                })
+            },
+        }
     }
 }
 

user/src/bin/filetest.rs

@@ -0,0 +1,54 @@
+#![no_std]
+#![no_main]
+
+use user_lib::{close, exit, fork, open, read, waitpid, write, OpenFlags};
+
+#[macro_use]
+extern crate user_lib;
+
+#[no_mangle]
+pub fn main() -> i32 {
+    let test_str = b"Hello, world!";
+    let fname = "fname\0";
+    let fd = open(fname, OpenFlags::CREATE | OpenFlags::WRONLY);
+    assert!(fd > 0);
+    let fd = fd as usize;
+    write(fd, &test_str[..]);
+    close(fd);
+
+    let fd = open(fname, OpenFlags::RDONLY);
+    assert!(fd > 0);
+    let fd = fd as usize;
+    let mut buffer = [0u8; 4];
+    let read_len = read(fd, &mut buffer) as usize;
+    println!(
+        "main 1st read: {}",
+        core::str::from_utf8(&buffer[..read_len]).unwrap()
+    ); // should be "Hell"
+    assert_eq!(&buffer[..read_len], &test_str[..read_len]);
+
+    let pid = fork();
+    if pid == 0 {
+        buffer.fill(0);
+        let n = read(fd, &mut buffer) as usize;
+        println!(
+            "child read: {}",
+            core::str::from_utf8(&buffer[..n]).unwrap()
+        ); // should be "o, w", coz inherit file cursor(offset)
+        assert_eq!(&buffer[..n], &test_str[read_len..read_len + n]);
+        close(fd);
+        exit(0);
+    } else {
+        let mut exit_code = 0;
+        waitpid(pid as usize, &mut exit_code);
+
+        buffer.fill(0);
+        let n = read(fd, &mut buffer) as usize;
+        println!(
+            "main 2nd read: {}",
+            core::str::from_utf8(&buffer[..n]).unwrap()
+        ); // should be also "o, w", coz file cursor(offset) independent
+        assert_eq!(&buffer[..n], &test_str[read_len..read_len + n]);
+    }
+    0
+}