added comments

Author: pranav-bhatt

src/safeposix/syscalls/fs_calls.rs

@@ -1486,32 +1486,41 @@ impl Cage {
         // otherwise, file descriptor table entry is stored in 'checkedfd'
         let checkedfd = self.get_filedescriptor(fd).unwrap();
         let unlocked_fd = checkedfd.read();
+
         if let Some(filedesc_enum) = &*unlocked_fd {
             //populate the dev id field -- can be done outside of the helper
             databuf.f_fsid = FS_METADATA.dev_id;
 
             match filedesc_enum {
+                // if the fd points to a normal file descriptor
                 File(normalfile_filedesc_obj) => {
+                    // won't panic since we have already checked that the entries exist
+                    // in the FS_METADATA inode table
                     let _inodeobj = FS_METADATA
                         .inodetable
                         .get(&normalfile_filedesc_obj.inode)
                         .unwrap();
 
                     return Self::_istatfs_helper(self, databuf);
                 }
+
+                // if the fd points to a socket, pipe, stream, or epoll file descriptor
                 Socket(_) | Pipe(_) | Stream(_) | Epoll(_) => {
                     return syscall_error(
                         Errno::EBADF,
                         "fstatfs",
-                        "can't fstatfs on socket, stream, pipe, or epollfd",
+                        "can't fstatfs on sockets, streams, pipes, or epoll fds",
                     );
                 }
             }
+        } else {
+            return syscall_error(Errno::EBADF, "statfs", "invalid file descriptor");
         }
-        return syscall_error(Errno::EBADF, "statfs", "invalid file descriptor");
     }
 
-    // Not sure why these values are hardcoded despite having the formulae commented
+    // These values have (probably) been picked up from the previously used
+    // environment, and have been working fine till now for our purposes
+    // TODO: Figure out how to populate the databuf values properly
     pub fn _istatfs_helper(&self, databuf: &mut FSData) -> i32 {
         databuf.f_type = 0xBEEFC0DE; //unassigned
         databuf.f_bsize = 4096;