Merge branch 'v0.21.x'

src/storage/CompositeStorage.cxx

@@ -211,6 +211,7 @@ CompositeStorage::Mount(const char *uri, std::unique_ptr<Storage> storage)
 	const std::lock_guard<Mutex> protect(mutex);
 
 	Directory &directory = root.Make(uri);
+	assert(!directory.storage);
 	directory.storage = std::move(storage);
 }
 

src/storage/CompositeStorage.hxx

@@ -100,6 +100,15 @@ public:
 	gcc_pure gcc_nonnull_all
 	Storage *GetMount(std::string_view uri) noexcept;
 
+	/**
+         * Is the given URI a mount point, i.e. is something already
+         * mounted on this path?
+	 */
+	gcc_pure gcc_nonnull_all
+	bool IsMountPoint(const char *uri) noexcept {
+		return GetMount(uri) != nullptr;
+	}
+
 	/**
 	 * Call the given function for each mounted storage, including
 	 * the root storage.  Passes mount point URI and the a const
@@ -112,6 +121,15 @@ public:
 		VisitMounts(uri, root, t);
 	}
 
+	/**
+	 * Is a storage with the given URI already mounted?
+	 */
+	gcc_pure gcc_nonnull_all
+	bool IsMounted(const char *storage_uri) const noexcept {
+		const std::lock_guard<Mutex> protect(mutex);
+		return IsMounted(root, storage_uri);
+	}
+
 	void Mount(const char *uri, std::unique_ptr<Storage> storage);
 	bool Unmount(const char *uri);
 
@@ -146,6 +164,22 @@ private:
 		}
 	}
 
+	gcc_pure gcc_nonnull_all
+	static bool IsMounted(const Directory &directory,
+			      const char *storage_uri) noexcept {
+		if (directory.storage) {
+			const auto uri = directory.storage->MapUTF8("");
+			if (uri == storage_uri)
+				return true;
+		}
+
+		for (const auto &i : directory.children)
+			if (IsMounted(i.second, storage_uri))
+				return true;
+
+		return false;
+	}
+
 	/**
 	 * Follow the given URI path, and find the outermost directory
 	 * which is a #Storage mount point.  If there are no mounts,

src/storage/StorageState.cxx

@@ -106,6 +106,17 @@ storage_state_restore(const char *line, TextFile &file, Instance &instance)
 
 	FormatDebug(storage_domain, "Restoring mount %s => %s", uri.c_str(), url.c_str());
 
+	auto &composite_storage = *(CompositeStorage *)instance.storage;
+	if (composite_storage.IsMountPoint(uri.c_str())) {
+		LogError(storage_domain, "Mount point busy");
+		return true;
+	}
+
+	if (composite_storage.IsMounted(url.c_str())) {
+		LogError(storage_domain, "This storage is already mounted");
+		return true;
+	}
+
 	auto &event_loop = instance.io_thread.GetEventLoop();
 	auto storage = CreateStorageURI(event_loop, url.c_str());
 	if (storage == nullptr) {
@@ -124,8 +135,7 @@ storage_state_restore(const char *line, TextFile &file, Instance &instance)
 		}
 	}
 
-	((CompositeStorage*)instance.storage)->Mount(uri.c_str(),
-						     std::move(storage));
+	composite_storage.Mount(uri.c_str(), std::move(storage));
 
 	return true;
 }