Propose allowing unlink for LocalUnopened files

Files created but never opened (LocalUnopened) have no S3 state and can
be unlinked. This prevents files from getting stuck in a state
where they cannot be deleted.

Signed-off-by: Maksim Beiner <maksim-beiner@idexx.com>

Author: Maxbey

mountpoint-s3-fs/src/superblock.rs

@@ -614,11 +614,21 @@ impl<OC: ObjectClient + Send + Sync + Clone> Metablock for Superblock<OC> {
         };
 
         match write_status {
-            WriteStatus::LocalUnopened | WriteStatus::LocalOpen | WriteStatus::PendingRename => {
+            // Safe to delete - no upload has started yet.
+            WriteStatus::LocalUnopened => {
+                debug!(
+                    parent = parent_ino,
+                    ?name,
+                    "unlink on LocalUnopened file, no s3 cleanup needed",
+                );
+            }
+            WriteStatus::LocalOpen | WriteStatus::PendingRename => {
+                // Active upload in progress - cannot safely delete without cancellation logic.
                 // In the future, we may permit `unlink` and cancel any in-flight uploads.
                 warn!(
                     parent = parent_ino,
                     ?name,
+                    ?write_status,
                     "unlink on local file not allowed until write is complete",
                 );
                 return Err(InodeError::UnlinkNotPermittedWhileWriting(inode.err()));
@@ -652,13 +662,19 @@ impl<OC: ObjectClient + Send + Sync + Clone> Metablock for Superblock<OC> {
                 debug_assert!(false, "inodes never change kind");
                 return Err(InodeError::NotADirectory(parent.err()));
             }
-            InodeKindData::Directory { children, .. } => {
+            InodeKindData::Directory {
+                children,
+                writing_children,
+                ..
+            } => {
                 // We want to remove the original child.
                 // If there is a mismatch in inode number between the existing inode and the deleted inode, we invalidate the existing inode's stat.
                 // If for some reason the child with the specified name was already removed, we do nothing as this is the desired state.
                 if let Some(existing_inode) = children.get(inode.name()) {
                     if existing_inode.ino() == inode.ino() {
                         children.remove(inode.name());
+                        // Also clean up writing_children for local files in LocalUnopened state
+                        writing_children.remove(&inode.ino());
                     } else {
                         // Mismatch in inode number, thus the existing inode might not be the same one we deleted
                         let mut state = existing_inode.get_mut_inode_state_no_check();