实现fat文件系统的truncate方法 (#428)

kernel/src/filesystem/fat/fs.rs

@@ -1511,6 +1511,17 @@ impl IndexNode for LockedFATInode {
         }
     }
 
+    fn truncate(&self, len: usize) -> Result<(), SystemError> {
+        let guard: SpinLockGuard<FATInode> = self.0.lock();
+        let old_size = guard.metadata.size as usize;
+        if len < old_size {
+            drop(guard);
+            self.resize(len)
+        } else {
+            Ok(())
+        }
+    }
+
     fn list(&self) -> Result<Vec<String>, SystemError> {
         let mut guard: SpinLockGuard<FATInode> = self.0.lock();
         let fatent: &FATDirEntry = &guard.inode_type;

kernel/src/syscall/mod.rs

@@ -357,6 +357,8 @@ pub const SYS_IOCTL: usize = 16;
 #[allow(dead_code)]
 pub const SYS_WRITEV: usize = 20;
 
+pub const SYS_MADVISE: usize = 28;
+
 pub const SYS_DUP: usize = 32;
 pub const SYS_DUP2: usize = 33;
 
@@ -1128,6 +1130,11 @@ impl Syscall {
                 Ok(0)
             }
 
+            SYS_MADVISE => {
+                kwarn!("SYS_MADVISE has not yet been implemented");
+                Ok(0)
+            }
+
             _ => panic!("Unsupported syscall ID: {}", syscall_num),
         };
         return r;