tape: format_media - implement special case for WORM media

src/tape/drive/lto/sg_tape.rs

@@ -201,11 +201,23 @@ impl SgTape {
     /// Format media, single partition
     pub fn format_media(&mut self, fast: bool) -> Result<(), Error> {
 
-        self.rewind()?;
-
         // get info about loaded media first
         let (head, _, _) = self.read_compression_page()?;
 
+        if MediumType::is_worm(head.medium_type) {
+            // We cannot FORMAT WORM media! Instead we check if its empty.
+
+            self.move_to_eom(false)?;
+            let pos = self.position()?;
+            if pos.logical_object_number != 0 {
+                bail!("format failed - detected WORM media with data.");
+            }
+
+            Ok(())
+        } else {
+
+            self.rewind()?;
+
             let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
             sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
             let mut cmd = Vec::new();
@@ -223,6 +235,7 @@ impl SgTape {
 
             Ok(())
         }
+    }
 
     /// Lock/Unlock drive door
     pub fn set_medium_removal(&mut self, allow: bool) -> Result<(), ScsiError> {