Merge pull request redpanda-data#22676 from WillemKauf/topic_mount_mi…

…nor_fixes

`cloud_storage`: minor fixes in `topic_mount_handler`

src/v/cloud_storage/tests/topic_mount_handler_test.cc

@@ -43,6 +43,15 @@ static const model::topic_namespace test_tp_ns_override{
 static ss::abort_source never_abort;
 static constexpr model::cloud_credentials_source config_file{
   model::cloud_credentials_source::config_file};
+
+static cluster::topic_configuration
+get_topic_configuration(cluster::topic_properties topic_props) {
+    auto topic_cfg = cluster::topic_configuration(
+      test_tp_ns.ns, test_tp_ns.tp, 1, 1);
+    topic_cfg.properties = std::move(topic_props);
+    return topic_cfg;
+}
+
 } // namespace
 
 struct TopicMountHandlerFixture
@@ -64,14 +73,6 @@ struct TopicMountHandlerFixture
         pool.stop().get();
     }
 
-    cluster::topic_configuration
-    get_topic_configuration(cluster::topic_properties topic_props) const {
-        auto topic_cfg = cluster::topic_configuration(
-          test_tp_ns.ns, test_tp_ns.tp, 1, 1);
-        topic_cfg.properties = std::move(topic_props);
-        return topic_cfg;
-    }
-
     ss::sharded<cloud_storage_clients::client_pool> pool;
     ss::sharded<remote> remote;
 };

src/v/cloud_storage/topic_mount_handler.cc

@@ -57,6 +57,10 @@ ss::future<topic_mount_result> topic_mount_handler::check_mount(
       _bucket, manifest_path, parent, existence_check_type::manifest);
 
     // If the manifest exists, it is possible to mount the topic.
+    // If the result is anything but download_result::success, it is
+    // assumed that the mount manifest does not exist, or is unreachable for
+    // whatever reason. In that case, it is simple enough for the user to
+    // reissue a request to `mount_topic()`.
     co_return (exists_result == download_result::success)
       ? topic_mount_result::success
       : topic_mount_result::mount_manifest_does_not_exist;
@@ -72,6 +76,8 @@ ss::future<topic_mount_result> topic_mount_handler::commit_mount(
     const auto delete_result = co_await _remote.delete_object(
       _bucket, manifest_path, parent);
 
+    // If the upload_result is anything but upload_result::success,
+    // the mount manifest was not deleted, and we cannot mount the topic.
     co_return (delete_result == upload_result::success)
       ? topic_mount_result::success
       : topic_mount_result::mount_manifest_not_deleted;

src/v/cloud_storage/topic_mount_handler.h

@@ -44,7 +44,7 @@ class topic_mount_handler {
     ss::future<topic_mount_result> mount_topic(
       const cluster::topic_configuration& topic_cfg, retry_chain_node& parent);
 
-    // Perform the mounting process by deleting the topic mount manifest.
+    // Perform the unmounting process by uploading the topic mount manifest.
     // topic_cfg should be the recovered topic configuration from a topic
     // manifest in cloud storage. If it has a value, the remote_label stored in
     // the topic properties is used as the "source" label. Otherwise, the