[pbs-devel] [RFC proxmox-backup 3/4] datastore: move snapshots to trash folder on destroy

[Christian Ebner]

Instead of directly deleting the snapshot directory and it's contents
on a prune, move the snapshot directory into the `.trash` subfolder
of the datastore.

This allows to mark chunks which were used by these index files if
the snapshot was pruned during an ongoing garbage collection.
Garbage collection will clean up these files before starting with the
marking phase 1 and read all index files after completing that phase,
touching these chunks as well.

Suggested-by: Thomas Lamprecht <t.lamprecht at proxmox.com>
Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 pbs-datastore/src/backup_info.rs | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/pbs-datastore/src/backup_info.rs b/pbs-datastore/src/backup_info.rs
index d4732fdd9..cd0d521c9 100644
--- a/pbs-datastore/src/backup_info.rs
+++ b/pbs-datastore/src/backup_info.rs
@@ -588,11 +588,19 @@ impl BackupDir {
             bail!("cannot remove protected snapshot"); // use special error type?
         }
 
+        let relative_path = self.relative_path();
+        let mut trash_path = self.store.base_path();
+        trash_path.push(".trash/");
+        trash_path.push(relative_path);
+        if let Some(parent) = trash_path.parent() {
+            std::fs::create_dir_all(&parent)
+                .with_context(|| format!("creating trash folders for {trash_path:?} failed"))?;
+        }
+
         let full_path = self.full_path();
         log::info!("removing backup snapshot {:?}", full_path);
-        std::fs::remove_dir_all(&full_path).map_err(|err| {
-            format_err!("removing backup snapshot {:?} failed - {}", full_path, err,)
-        })?;
+        std::fs::rename(&full_path, trash_path)
+            .with_context(|| format!("moving backup snapshot {full_path:?} to trash failed"))?;
 
         // remove no longer needed lock files
         let _ = std::fs::remove_file(self.manifest_lock_path()); // ignore errors
-- 
2.39.5