tape: silence some warnings

Nightly rustc now warns about unused private fields in the case of a
non-pub newtype struct, so use an underscore-prefixed dummy field name
to get rid of the warning.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

pbs-config/src/lib.rs

@@ -44,12 +44,14 @@ pub fn backup_group() -> Result<nix::unistd::Group, Error> {
     }
 }
 
-pub struct BackupLockGuard(Option<std::fs::File>);
+pub struct BackupLockGuard {
+    _file: Option<std::fs::File>,
+}
 
 #[doc(hidden)]
 /// Note: do not use for production code, this is only intended for tests
 pub unsafe fn create_mocked_lock() -> BackupLockGuard {
-    BackupLockGuard(None)
+    BackupLockGuard { _file: None }
 }
 
 /// Open or create a lock file owned by user "backup" and lock it.
@@ -73,7 +75,7 @@ pub fn open_backup_lockfile<P: AsRef<std::path::Path>>(
     let timeout = timeout.unwrap_or(std::time::Duration::new(10, 0));
 
     let file = proxmox_sys::fs::open_file_locked(&path, timeout, exclusive, options)?;
-    Ok(BackupLockGuard(Some(file)))
+    Ok(BackupLockGuard { _file: Some(file) })
 }
 
 /// Atomically write data to file owned by "root:backup" with permission "0640"

src/tape/drive/mod.rs

@@ -592,7 +592,9 @@ fn tape_device_path(config: &SectionConfigData, drive: &str) -> Result<String, E
     }
 }
 
-pub struct DeviceLockGuard(std::fs::File);
+pub struct DeviceLockGuard {
+    _file: std::fs::File,
+}
 
 // Uses systemd escape_unit to compute a file name from `device_path`, the try
 // to lock `/var/lock/<name>`.
@@ -630,7 +632,7 @@ fn lock_device_path(device_path: &str) -> Result<DeviceLockGuard, TapeLockError>
         }
     }
 
-    Ok(DeviceLockGuard(file))
+    Ok(DeviceLockGuard { _file: file })
 }
 
 // Same logic as lock_device_path, but uses a timeout of 0, making it