Do not send zero-byte reads to the underlying device

src/main.rs

@@ -36,6 +36,9 @@ impl file_rpc::Server for Serv {
     fn read(&self, fd: u64, pos: u64, len: usize) -> Result<Vec<u8>, ()> {
         let (mount_id, file_offset, size) = self.files.read()[fd as usize];
         let read_len = usize::min(len, size - (pos as usize));
+        if read_len == 0 {
+            return Ok(Vec::new());
+        };
         let mounts = self.mounts.read();
         let mount = &mounts[mount_id as usize];
         (&mount.0).seek(std::io::SeekFrom::Start(file_offset + pos)).unwrap();