tape restore: split restore_chunk_archive

Split out a separate function scan_chunk_archive() for catalog restores.

Note: Required, because we need to optimize restore_chunk_archive() to
write datastore in separate threads (else thape drive will stop during restore)

src/api2/tape/restore.rs

@@ -150,12 +150,12 @@ impl DataStoreMap {
         set
     }
 
-    fn get_datastore(&self, source: &str) -> Option<&DataStore> {
+    fn get_datastore(&self, source: &str) -> Option<Arc<DataStore>> {
         if let Some(store) = self.map.get(source) {
-            return Some(&store);
+            return Some(Arc::clone(store));
         }
         if let Some(ref store) = self.default {
-            return Some(&store);
+            return Some(Arc::clone(store));
         }
 
         return None;
@@ -575,10 +575,16 @@ fn restore_archive<'a>(
 
             if datastore.is_some() || target.is_none() {
                 let checked_chunks = checked_chunks_map
-                    .entry(datastore.map(|d| d.name()).unwrap_or("_unused_").to_string())
+                    .entry(datastore.as_ref().map(|d| d.name()).unwrap_or("_unused_").to_string())
                     .or_insert(HashSet::new());
 
-                if let Some(chunks) = restore_chunk_archive(worker, reader, datastore, checked_chunks, verbose)? {
+                let chunks = if let Some(datastore) = datastore {
+                    restore_chunk_archive(worker, reader, datastore, checked_chunks, verbose)?
+                } else {
+                    scan_chunk_archive(worker, reader, verbose)?
+                };
+
+                if let Some(chunks) = chunks {
                     catalog.start_chunk_archive(
                         Uuid::from(header.uuid),
                         current_file_number,
@@ -616,10 +622,56 @@ fn restore_archive<'a>(
     Ok(())
 }
 
+// Read chunk archive without restoring data - just record contained chunks
+fn scan_chunk_archive<'a>(
+    worker: &WorkerTask,
+    reader: Box<dyn 'a + TapeRead>,
+    verbose: bool,
+) -> Result<Option<Vec<[u8;32]>>, Error> {
+
+    let mut chunks = Vec::new();
+
+    let mut decoder = ChunkArchiveDecoder::new(reader);
+
+    loop {
+        let digest = match decoder.next_chunk() {
+            Ok(Some((digest, _blob))) => digest,
+            Ok(None) => break,
+            Err(err) => {
+                let reader = decoder.reader();
+
+                // check if this stream is marked incomplete
+                if let Ok(true) = reader.is_incomplete() {
+                    return Ok(Some(chunks));
+                }
+
+                // check if this is an aborted stream without end marker
+                if let Ok(false) = reader.has_end_marker() {
+                    worker.log("missing stream end marker".to_string());
+                    return Ok(None);
+                }
+
+                // else the archive is corrupt
+                return Err(err);
+            }
+        };
+
+        worker.check_abort()?;
+
+        if verbose {
+            task_log!(worker, "Found chunk: {}", proxmox::tools::digest_to_hex(&digest));
+        }
+
+        chunks.push(digest);
+    }
+
+    Ok(Some(chunks))
+}
+
 fn restore_chunk_archive<'a>(
     worker: &WorkerTask,
     reader: Box<dyn 'a + TapeRead>,
-    datastore: Option<&DataStore>,
+    datastore: Arc<DataStore>,
     checked_chunks: &mut HashSet<[u8;32]>,
     verbose: bool,
 ) -> Result<Option<Vec<[u8;32]>>, Error> {
@@ -653,7 +705,6 @@ fn restore_chunk_archive<'a>(
 
         worker.check_abort()?;
 
-        if let Some(datastore) = datastore {
         let chunk_exists = datastore.cond_touch_chunk(&digest, false)?;
         if !chunk_exists {
             blob.verify_crc()?;
@@ -669,9 +720,6 @@ fn restore_chunk_archive<'a>(
             task_log!(worker, "Found existing chunk: {}", proxmox::tools::digest_to_hex(&digest));
         }
         checked_chunks.insert(digest.clone());
-        } else if verbose {
-            task_log!(worker, "Found chunk: {}", proxmox::tools::digest_to_hex(&digest));
-        }
         chunks.push(digest);
     }