change tape drive lock path

New kernel has stricter checks on tmpfs with stick-bit on directories, so some
commands (i.e. proxmox-tape changer status) fails when executed as root, because
permission checks fails when locking the drive.

This patch move the drive locks to /run/proxmox-backup/drive-lock.

Note: This is incompatible to old locking mechmanism, so users may not
run tape backups during update (or running backup can fail).

src/tape/mod.rs

@@ -48,6 +48,9 @@ pub use pool_writer::*;
 /// Directory path where we store all tape status information
 pub const TAPE_STATUS_DIR: &str = "/var/lib/proxmox-backup/tape";
 
+/// Directory path where we store drive lock file
+pub const DRIVE_LOCK_DIR: &str = concat!(PROXMOX_BACKUP_RUN_DIR_M!(), "/drive-lock");
+
 /// Directory path where we store temporary drive state
 pub const DRIVE_STATE_DIR: &str = concat!(PROXMOX_BACKUP_RUN_DIR_M!(), "/drive-state");
 
@@ -78,6 +81,21 @@ pub fn create_tape_status_dir() -> Result<(), Error> {
     Ok(())
 }
 
+/// Create drive lock dir with correct permission
+pub fn create_drive_lock_dir() -> Result<(), Error> {
+    let backup_user = crate::backup::backup_user()?;
+    let mode = nix::sys::stat::Mode::from_bits_truncate(0o0750);
+    let options = CreateOptions::new()
+        .perm(mode)
+        .owner(backup_user.uid)
+        .group(backup_user.gid);
+
+    create_path(DRIVE_LOCK_DIR, None, Some(options))
+        .map_err(|err: Error| format_err!("unable to create drive state dir - {}", err))?;
+
+    Ok(())
+}
+
 /// Create drive state dir with correct permission
 pub fn create_drive_state_dir() -> Result<(), Error> {
     let backup_user = crate::backup::backup_user()?;