fix storage datasets creation

internal/httpapp/api_handlers.go

@@ -281,13 +281,50 @@ func (a *App) handleCreateDataset(w http.ResponseWriter, r *http.Request) {
 		req.Options = make(map[string]string)
 	}
 
-	if err := a.zfs.CreateDataset(req.Name, req.Options); err != nil {
-		log.Printf("create dataset error: %v", err)
-		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+	err := a.zfs.CreateDataset(req.Name, req.Options)
+
+	// CRITICAL: Always check if dataset exists, regardless of reported error
+	// ZFS often reports mountpoint errors but dataset is still created
+	// The CreateDataset function already does retries, but we double-check here
+	// Wait a brief moment for dataset to be fully registered
+	time.Sleep(300 * time.Millisecond)
+
+	datasets, getErr := a.zfs.ListDatasets("")
+	var datasetExists bool
+	if getErr == nil {
+		for _, ds := range datasets {
+			if ds.Name == req.Name {
+				datasetExists = true
+				break
+			}
+		}
+	}
+
+	if datasetExists {
+		// Dataset exists - this is success!
+		if err != nil {
+			log.Printf("info: dataset %s created successfully despite CreateDataset reporting error: %v", req.Name, err)
+		} else {
+			log.Printf("info: dataset %s created successfully", req.Name)
+		}
+		// Set cache-control headers
+		w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
+		w.Header().Set("Pragma", "no-cache")
+		w.Header().Set("Expires", "0")
+		writeJSON(w, http.StatusCreated, map[string]string{"message": "dataset created", "name": req.Name})
 		return
 	}
 
-	writeJSON(w, http.StatusCreated, map[string]string{"message": "dataset created", "name": req.Name})
+	// Dataset doesn't exist - return the error with detailed context
+	if err != nil {
+		log.Printf("error: dataset %s creation failed - CreateDataset error: %v, ListDatasets error: %v", req.Name, err, getErr)
+		writeError(w, errors.ErrInternal("failed to create dataset").WithDetails(err.Error()))
+		return
+	}
+
+	// No error but dataset doesn't exist (shouldn't happen, but handle it)
+	log.Printf("warning: dataset %s creation reported no error but dataset was not found", req.Name)
+	writeError(w, errors.ErrInternal(fmt.Sprintf("Dataset '%s' creation reported success but dataset was not found", req.Name)))
 }
 
 func (a *App) handleGetDataset(w http.ResponseWriter, r *http.Request) {