Merge branch 'v0.21.x'

NEWS

@@ -43,15 +43,24 @@ ver 0.22 (not yet released)
 ver 0.21.25 (not yet released)
 * protocol:
   - fix crash when using "rangeid" while playing
+* database
+  - simple: automatically scan new mounts
+* storage
+  - fix disappearing mounts after mounting twice
+  - udisks: fix reading ".mpdignore"
 * input
   - file: detect premature end of file
   - smbclient: don't send credentials to MPD clients
 * decoder
   - opus: apply pre-skip and end trimming
   - opus: fix memory leak
+  - opus: fix crash bug
+  - vorbis: fix crash bug
 * output
   - osx: improve sample rate selection
   - osx: fix noise while stopping
+* neighbor
+  - upnp: fix crash during shutdown
 * Windows/Android:
   - fix Boost detection after breaking change in Meson 0.54
 

doc/plugins.rst

@@ -60,25 +60,25 @@ The default plugin which gives :program:`MPD` access to local files. It is used
 curl
 ----
 
-A WebDAV client using libcurl. It is used when :code:`music_directory` contains a http:// or https:// URI, for example :samp:`https://the.server/dav/`.
+A WebDAV client using libcurl. It is used when :code:`music_directory`
+contains a ``http://`` or ``https://`` URI, for example
+:samp:`https://the.server/dav/`.
 
 smbclient
 ---------
 
-Load music files from a SMB/CIFS server. It is used when :code:`music_directory` contains a smb:// URI, for example :samp:`smb://myfileserver/Music`.
+Load music files from a SMB/CIFS server. It is used when
+:code:`music_directory` contains a ``smb://`` URI, for example
+:samp:`smb://myfileserver/Music`.
 
 nfs
 ---
 
-Load music files from a NFS server. It is used when :code:`music_directory` contains a nfs:// URI according to RFC2224, for example :samp:`nfs://servername/path`.
+Load music files from a NFS server.  It is used when
+:code:`music_directory` contains a ``nfs://`` URI according to
+RFC2224, for example :samp:`nfs://servername/path`.
 
-This plugin uses libnfs, which supports only NFS version 3. Since :program:`MPD` is not allowed to bind to "privileged ports", the NFS server needs to enable the "insecure" setting; example :file:`/etc/exports`:
-
-.. code-block:: none
-
-    /srv/mp3 192.168.1.55(ro,insecure)
-
-Don't fear: "insecure" does not mean that your NFS server is insecure. A few decades ago, people thought the concept of "privileged ports" would make network services "secure", which was a fallacy. The absence of this obsolete "security" measure means little.
+See :ref:`input_nfs` for more information.
 
 udisks
 ------
@@ -186,7 +186,10 @@ curl
 
 Opens remote files or streams over HTTP using libcurl.
 
-Note that unless overridden by the below settings (e.g. by setting them to a blank value), general curl configuration from environment variables such as http_proxy or specified in :file:`~/.curlrc` will be in effect.
+Note that unless overridden by the below settings (e.g. by setting
+them to a blank value), general curl configuration from environment
+variables such as ``http_proxy`` or specified in :file:`~/.curlrc`
+will be in effect.
 
 .. list-table::
    :widths: 20 80
@@ -206,7 +209,9 @@ Note that unless overridden by the below settings (e.g. by setting them to a bla
 ffmpeg
 ------
 
-Access to various network protocols implemented by the FFmpeg library: gopher://, rtp://, rtsp://, rtmp://, rtmpt://, rtmps://
+Access to various network protocols implemented by the FFmpeg library:
+``gopher://``, ``rtp://``, ``rtsp://``, ``rtmp://``, ``rtmpt://``,
+``rtmps://``
 
 file
 ----
@@ -218,30 +223,51 @@ mms
 
 Plays streams with the MMS protocol using `libmms <https://launchpad.net/libmms>`_.
 
+.. _input_nfs:
+
 nfs
 ---
 
-Allows :program:`MPD` to access files on NFSv3 servers without actually mounting them (i.e. in userspace, without help from the kernel's VFS layer). All URIs with the nfs:// scheme are used according to RFC2224. Example:
+Allows :program:`MPD` to access files on NFS servers without actually
+mounting them (i.e. with :program:`libnfs` in userspace, without help
+from the kernel's VFS layer). All URIs with the ``nfs://`` scheme are
+used according to RFC2224. Example:
 
 .. code-block:: none
 
      mpc add nfs://servername/path/filename.ogg
 
-Note that this usually requires enabling the "insecure" flag in the server's /etc/exports file, because :program:`MPD` cannot bind to so-called "privileged" ports. Don't fear: this will not make your file server insecure; the flag was named in a time long ago when privileged ports were thought to be meaningful for security. By today's standards, NFSv3 is not secure at all, and if you believe it is, you're already doomed.
+This plugin uses :program:`libnfs`, which supports only NFS version 3.
+Since :program:`MPD` is not allowed to bind to so-called "privileged
+ports", the NFS server needs to enable the ``insecure`` setting;
+example :file:`/etc/exports`:
+
+.. code-block:: none
+
+    /srv/mp3 192.168.1.55(ro,insecure)
+
+Don't fear: this will not make your file server insecure; the flag was
+named a time long ago when privileged ports were thought to be
+meaningful for security. By today's standards, NFSv3 is not secure at
+all, and if you believe it is, you're already doomed.
 
 smbclient
 ---------
 
-Allows :program:`MPD` to access files on SMB/CIFS servers (e.g. Samba or Microsoft Windows). All URIs with the smb:// scheme are used. Example:
+Allows :program:`MPD` to access files on SMB/CIFS servers (e.g. Samba
+or Microsoft Windows). All URIs with the ``smb://`` scheme are
+used.  Example:
 
 .. code-block:: none
 
     mpc add smb://servername/sharename/filename.ogg
+    mpc add smb://username:password@servername/sharename/filename.ogg
 
 qobuz
 -----
 
-Play songs from the commercial streaming service Qobuz. It plays URLs in the form qobuz://track/ID, e.g.:
+Play songs from the commercial streaming service Qobuz. It plays URLs
+in the form ``qobuz://track/ID``, e.g.:
 
 .. code-block:: none
 
@@ -267,7 +293,9 @@ Play songs from the commercial streaming service Qobuz. It plays URLs in the for
 tidal
 -----
 
-Play songs from the commercial streaming service `Tidal <http://tidal.com/>`_. It plays URLs in the form tidal://track/ID, e.g.:
+Play songs from the commercial streaming service `Tidal
+<http://tidal.com/>`_. It plays URLs in the form ``tidal://track/ID``,
+e.g.:
 
 .. warning::
 

src/PluginUnavailable.hxx

@@ -29,9 +29,7 @@
  */
 class PluginUnavailable : public std::runtime_error {
 public:
-	template<typename M>
-	explicit PluginUnavailable(M &&msg) noexcept
-		:std::runtime_error(std::forward<M>(msg)) {}
+	using std::runtime_error::runtime_error;
 };
 
 /**
@@ -42,9 +40,7 @@ public:
  */
 class PluginUnconfigured : public PluginUnavailable {
 public:
-	template<typename M>
-	explicit PluginUnconfigured(M &&msg) noexcept
-		:PluginUnavailable(std::forward<M>(msg)) {}
+	using PluginUnavailable::PluginUnavailable;
 };
 
 #endif

src/SongUpdate.cxx

@@ -69,6 +69,7 @@ Song::UpdateFile(Storage &storage)
 	TagBuilder tag_builder;
 	auto new_audio_format = AudioFormat::Undefined();
 
+	try {
 		const auto path_fs = storage.MapFS(relative_uri.c_str());
 		if (path_fs.IsNull()) {
 			const auto absolute_uri =
@@ -81,6 +82,10 @@ Song::UpdateFile(Storage &storage)
 						     &new_audio_format))
 				return false;
 		}
+	} catch (...) {
+		// TODO: log or propagate I/O errors?
+		return false;
+	}
 
 	mtime = info.mtime;
 	audio_format = new_audio_format;
@@ -139,8 +144,14 @@ DetachedSong::LoadFile(Path path)
 		return false;
 
 	TagBuilder tag_builder;
+
+	try {
 		if (!ScanFileTagsWithGeneric(path, tag_builder))
 			return false;
+	} catch (...) {
+		// TODO: log or propagate I/O errors?
+		return false;
+	}
 
 	mtime = fi.GetModificationTime();
 	tag_builder.Commit(tag);
@@ -157,8 +168,14 @@ DetachedSong::Update()
 		return LoadFile(path_fs);
 	} else if (IsRemote()) {
 		TagBuilder tag_builder;
+
+		try {
 			if (!tag_stream_scan(uri.c_str(), tag_builder))
 				return false;
+		} catch (...) {
+			// TODO: log or propagate I/O errors?
+			return false;
+		}
 
 		mtime = std::chrono::system_clock::time_point::min();
 		tag_builder.Commit(tag);

src/TagStream.cxx

@@ -43,7 +43,7 @@ CheckDecoderPlugin(const DecoderPlugin &plugin,
 }
 
 bool
-tag_stream_scan(InputStream &is, TagHandler &handler) noexcept
+tag_stream_scan(InputStream &is, TagHandler &handler)
 {
 	assert(is.IsReady());
 
@@ -81,7 +81,7 @@ tag_stream_scan(const char *uri, TagHandler &handler)
 
 bool
 tag_stream_scan(InputStream &is, TagBuilder &builder,
-		AudioFormat *audio_format) noexcept
+		AudioFormat *audio_format)
 {
 	assert(is.IsReady());
 

src/TagStream.hxx

@@ -29,14 +29,16 @@ class TagBuilder;
  * Scan the tags of an #InputStream.  Invokes matching decoder
  * plugins, but does not invoke the special "APE" and "ID3" scanners.
  *
+ * Throws on I/O error.
+ *
  * @return true if the file was recognized (even if no metadata was
  * found)
  */
 bool
-tag_stream_scan(InputStream &is, TagHandler &handler) noexcept;
+tag_stream_scan(InputStream &is, TagHandler &handler);
 
 /**
- * Throws on error.
+ * Throws on I/O error.
  */
 bool
 tag_stream_scan(const char *uri, TagHandler &handler);
@@ -46,15 +48,17 @@ tag_stream_scan(const char *uri, TagHandler &handler);
  * plugins, and falls back to generic scanners (APE and ID3) if no
  * tags were found (but the file was recognized).
  *
+ * Throws on I/O error.
+ *
  * @return true if the file was recognized (even if no metadata was
  * found)
  */
 bool
 tag_stream_scan(InputStream &is, TagBuilder &builder,
-		AudioFormat *audio_format=nullptr) noexcept;
+		AudioFormat *audio_format=nullptr);
 
 /**
- * Throws on error.
+ * Throws on I/O error.
  */
 bool
 tag_stream_scan(const char *uri, TagBuilder &builder,

src/command/StorageCommands.cxx

@@ -195,6 +195,16 @@ handle_mount(Client &client, Request args, Response &r)
 		return CommandResult::ERROR;
 	}
 
+	if (composite.IsMountPoint(local_uri)) {
+		r.Error(ACK_ERROR_ARG, "Mount point busy");
+		return CommandResult::ERROR;
+	}
+
+	if (composite.IsMounted(remote_uri)) {
+		r.Error(ACK_ERROR_ARG, "This storage is already mounted");
+		return CommandResult::ERROR;
+	}
+
 	auto &event_loop = instance.io_thread.GetEventLoop();
 	auto storage = CreateStorageURI(event_loop, remote_uri);
 	if (storage == nullptr) {
@@ -207,8 +217,10 @@ handle_mount(Client &client, Request args, Response &r)
 
 #ifdef ENABLE_DATABASE
 	if (auto *db = dynamic_cast<SimpleDatabase *>(instance.GetDatabase())) {
+		bool need_update;
+
 		try {
-			db->Mount(local_uri, remote_uri);
+			need_update = !db->Mount(local_uri, remote_uri);
 		} catch (...) {
 			composite.Unmount(local_uri);
 			throw;
@@ -217,6 +229,12 @@ handle_mount(Client &client, Request args, Response &r)
 		// TODO: call Instance::OnDatabaseModified()?
 		// TODO: trigger database update?
 		instance.EmitIdle(IDLE_DATABASE);
+
+		if (need_update) {
+			UpdateService *update = client.GetInstance().update;
+			if (update != nullptr)
+				update->Enqueue(local_uri, false);
+		}
 	}
 #endif
 

src/db/plugins/simple/SimpleDatabasePlugin.cxx

@@ -427,7 +427,7 @@ IsUnsafeChar(char ch)
 	return !IsSafeChar(ch);
 }
 
-void
+bool
 SimpleDatabase::Mount(const char *local_uri, const char *storage_uri)
 {
 	if (cache_path.IsNull())
@@ -446,9 +446,11 @@ SimpleDatabase::Mount(const char *local_uri, const char *storage_uri)
 						   compress);
 	db->Open();
 
-	// TODO: update the new database instance?
+	bool exists = db->FileExists();
 
 	Mount(local_uri, std::move(db));
+
+	return exists;
 }
 
 inline DatabasePtr

src/db/plugins/simple/SimpleDatabasePlugin.hxx

@@ -103,9 +103,11 @@ public:
 
 	/**
 	 * Throws #std::runtime_error on error.
+	 *
+	 * @return false if the mounted database needs to be updated
 	 */
 	gcc_nonnull_all
-	void Mount(const char *local_uri, const char *storage_uri);
+	bool Mount(const char *local_uri, const char *storage_uri);
 
 	gcc_nonnull_all
 	bool Unmount(const char *uri) noexcept;

src/db/update/Walk.cxx

@@ -322,8 +322,8 @@ UpdateWalk::UpdateDirectory(Directory &directory,
 
 	try {
 		Mutex mutex;
-		auto is = InputStream::OpenReady(PathTraitsUTF8::Build(storage.MapUTF8(directory.GetPath()),
-								       ".mpdignore").c_str(),
+		auto is = InputStream::OpenReady(storage.MapUTF8(PathTraitsUTF8::Build(directory.GetPath(),
+										       ".mpdignore")).c_str(),
 						 mutex);
 		child_exclude_list.Load(std::move(is));
 	} catch (...) {

src/decoder/DecoderPlugin.hxx

@@ -69,16 +69,20 @@ struct DecoderPlugin {
 	/**
          * Scan metadata of a file.
          *
-	 * @return false if the operation has failed
+	 * Throws on I/O error.
+	 *
+	 * @return false if the file was not recognized
 	 */
-	bool (*scan_file)(Path path_fs, TagHandler &handler) noexcept = nullptr;
+	bool (*scan_file)(Path path_fs, TagHandler &handler) = nullptr;
 
 	/**
-	 * Scan metadata of a file.
+	 * Scan metadata of a stream.
          *
-	 * @return false if the operation has failed
+	 * Throws on I/O error.
+	 *
+	 * @return false if the stream was not recognized
 	 */
-	bool (*scan_stream)(InputStream &is, TagHandler &handler) noexcept = nullptr;
+	bool (*scan_stream)(InputStream &is, TagHandler &handler) = nullptr;
 
 	/**
 	 * @brief Return a "virtual" filename for subtracks in
@@ -99,14 +103,14 @@ struct DecoderPlugin {
 				void (*_file_decode)(DecoderClient &client,
 						     Path path_fs),
 				bool (*_scan_file)(Path path_fs,
-						   TagHandler &handler) noexcept) noexcept
+						   TagHandler &handler)) noexcept
 		:name(_name),
 		 file_decode(_file_decode), scan_file(_scan_file) {}
 
 	constexpr DecoderPlugin(const char *_name,
 				void (*_stream_decode)(DecoderClient &client,
 						       InputStream &is),
-				bool (*_scan_stream)(InputStream &is, TagHandler &handler) noexcept) noexcept
+				bool (*_scan_stream)(InputStream &is, TagHandler &handler)) noexcept
 		:name(_name),
 		 stream_decode(_stream_decode),
 		 scan_stream(_scan_stream) {}
@@ -114,11 +118,11 @@ struct DecoderPlugin {
 	constexpr DecoderPlugin(const char *_name,
 				void (*_stream_decode)(DecoderClient &client,
 						       InputStream &is),
-				bool (*_scan_stream)(InputStream &is, TagHandler &handler) noexcept,
+				bool (*_scan_stream)(InputStream &is, TagHandler &handler),
 				void (*_file_decode)(DecoderClient &client,
 						     Path path_fs),
 				bool (*_scan_file)(Path path_fs,
-						   TagHandler &handler) noexcept) noexcept
+						   TagHandler &handler)) noexcept
 		:name(_name),
 		 stream_decode(_stream_decode),
 		 file_decode(_file_decode),
@@ -191,7 +195,7 @@ struct DecoderPlugin {
 	 * Read the tag of a file.
 	 */
 	template<typename P>
-	bool ScanFile(P path_fs, TagHandler &handler) const noexcept {
+	bool ScanFile(P path_fs, TagHandler &handler) const {
 		return scan_file != nullptr
 			? scan_file(path_fs, handler)
 			: false;
@@ -200,7 +204,7 @@ struct DecoderPlugin {
 	/**
 	 * Read the tag of a stream.
 	 */
-	bool ScanStream(InputStream &is, TagHandler &handler) const noexcept {
+	bool ScanStream(InputStream &is, TagHandler &handler) const {
 		return scan_stream != nullptr
 			? scan_stream(is, handler)
 			: false;

src/decoder/plugins/AudiofileDecoderPlugin.cxx

@@ -241,7 +241,7 @@ audiofile_stream_decode(DecoderClient &client, InputStream &is)
 }
 
 static bool
-audiofile_scan_stream(InputStream &is, TagHandler &handler) noexcept
+audiofile_scan_stream(InputStream &is, TagHandler &handler)
 {
 	if (!is.IsSeekable() || !is.KnownSize())
 		return false;

src/decoder/plugins/DsdiffDecoderPlugin.cxx

@@ -448,7 +448,7 @@ dsdiff_stream_decode(DecoderClient &client, InputStream &is)
 }
 
 static bool
-dsdiff_scan_stream(InputStream &is, TagHandler &handler) noexcept
+dsdiff_scan_stream(InputStream &is, TagHandler &handler)
 {
 	DsdiffMetaData metadata;
 	DsdiffChunkHeader chunk_header;

src/decoder/plugins/DsfDecoderPlugin.cxx

@@ -325,7 +325,7 @@ dsf_stream_decode(DecoderClient &client, InputStream &is)
 }
 
 static bool
-dsf_scan_stream(InputStream &is, TagHandler &handler) noexcept
+dsf_scan_stream(InputStream &is, TagHandler &handler)
 {
 	/* check DSF metadata */
 	DsfMetaData metadata;

src/decoder/plugins/FaadDecoderPlugin.cxx

@@ -411,7 +411,7 @@ faad_stream_decode(DecoderClient &client, InputStream &is)
 }
 
 static bool
-faad_scan_stream(InputStream &is, TagHandler &handler) noexcept
+faad_scan_stream(InputStream &is, TagHandler &handler)
 {
 	auto result = faad_get_file_time(is);
 	if (!result.first)

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -591,8 +591,7 @@ ffmpeg_decode(DecoderClient &client, InputStream &input)
 }
 
 static bool
-FfmpegScanStream(AVFormatContext &format_context,
-		 TagHandler &handler) noexcept
+FfmpegScanStream(AVFormatContext &format_context, TagHandler &handler)
 {
 	const int find_result =
 		avformat_find_stream_info(&format_context, nullptr);
@@ -625,16 +624,14 @@ FfmpegScanStream(AVFormatContext &format_context,
 }
 
 static bool
-ffmpeg_scan_stream(InputStream &is, TagHandler &handler) noexcept
-try {
+ffmpeg_scan_stream(InputStream &is, TagHandler &handler)
+{
 	AvioStream stream(nullptr, is);
 	if (!stream.Open())
 		return false;
 
 	auto f = FfmpegOpenInput(stream.io, is.GetURI(), nullptr);
 	return FfmpegScanStream(*f, handler);
-} catch (...) {
-	return false;
 }
 
 /**

src/decoder/plugins/FlacDecoderPlugin.cxx

@@ -69,7 +69,7 @@ flac_write_cb(const FLAC__StreamDecoder *dec, const FLAC__Frame *frame,
 }
 
 static bool
-flac_scan_file(Path path_fs, TagHandler &handler) noexcept
+flac_scan_file(Path path_fs, TagHandler &handler)
 {
 	FlacMetadataChain chain;
 	if (!chain.Read(NarrowPath(path_fs))) {
@@ -84,7 +84,7 @@ flac_scan_file(Path path_fs, TagHandler &handler) noexcept
 }
 
 static bool
-flac_scan_stream(InputStream &is, TagHandler &handler) noexcept
+flac_scan_stream(InputStream &is, TagHandler &handler)
 {
 	FlacMetadataChain chain;
 	if (!chain.Read(is)) {
@@ -313,7 +313,7 @@ oggflac_init([[maybe_unused]] const ConfigBlock &block)
 }
 
 static bool
-oggflac_scan_file(Path path_fs, TagHandler &handler) noexcept
+oggflac_scan_file(Path path_fs, TagHandler &handler)
 {
 	FlacMetadataChain chain;
 	if (!chain.ReadOgg(NarrowPath(path_fs))) {
@@ -328,7 +328,7 @@ oggflac_scan_file(Path path_fs, TagHandler &handler) noexcept
 }
 
 static bool
-oggflac_scan_stream(InputStream &is, TagHandler &handler) noexcept
+oggflac_scan_stream(InputStream &is, TagHandler &handler)
 {
 	FlacMetadataChain chain;
 	if (!chain.ReadOgg(is)) {

src/decoder/plugins/MadDecoderPlugin.cxx

@@ -1013,7 +1013,7 @@ MadDecoder::RunScan(TagHandler &handler) noexcept
 }
 
 static bool
-mad_decoder_scan_stream(InputStream &is, TagHandler &handler) noexcept
+mad_decoder_scan_stream(InputStream &is, TagHandler &handler)
 {
 	MadDecoder data(nullptr, is);
 	return data.RunScan(handler);

src/decoder/plugins/MpcdecDecoderPlugin.cxx

@@ -273,7 +273,7 @@ mpcdec_get_file_duration(InputStream &is)
 }
 
 static bool
-mpcdec_scan_stream(InputStream &is, TagHandler &handler) noexcept
+mpcdec_scan_stream(InputStream &is, TagHandler &handler)
 {
 	const auto duration = mpcdec_get_file_duration(is);
 	if (duration.IsNegative())

src/decoder/plugins/OpusDecoderPlugin.cxx

@@ -423,8 +423,8 @@ VisitOpusDuration(InputStream &is, OggSyncState &sync, OggStreamState &stream,
 	}
 }
 
-bool
-mpd_opus_scan_stream(InputStream &is, TagHandler &handler) noexcept
+static bool
+mpd_opus_scan_stream(InputStream &is, TagHandler &handler)
 {
 	InputStreamReader reader(is);
 	OggSyncState oy(reader);

src/decoder/plugins/SndfileDecoderPlugin.cxx

@@ -268,7 +268,7 @@ static constexpr struct {
 };
 
 static bool
-sndfile_scan_stream(InputStream &is, TagHandler &handler) noexcept
+sndfile_scan_stream(InputStream &is, TagHandler &handler)
 {
 	SF_INFO info;
 

src/decoder/plugins/VorbisDecoderPlugin.cxx

@@ -370,7 +370,7 @@ VisitVorbisDuration(InputStream &is,
 }
 
 static bool
-vorbis_scan_stream(InputStream &is, TagHandler &handler) noexcept
+vorbis_scan_stream(InputStream &is, TagHandler &handler)
 {
 	/* initialize libogg */
 

src/decoder/plugins/WavpackDecoderPlugin.cxx

@@ -612,7 +612,7 @@ wavpack_scan_file(Path path_fs, TagHandler &handler) noexcept
 }
 
 static bool
-wavpack_scan_stream(InputStream &is, TagHandler &handler) noexcept
+wavpack_scan_stream(InputStream &is, TagHandler &handler)
 {
 	WavpackInput isp(nullptr, is);
 

src/neighbor/plugins/UdisksNeighborPlugin.cxx

@@ -45,6 +45,11 @@ ToNeighborInfo(const UDisks2::Object &o) noexcept
 	return {o.GetUri(), o.path};
 }
 
+static constexpr char udisks_neighbor_match[] =
+	"type='signal',sender='" UDISKS2_INTERFACE "',"
+	"interface='" DBUS_OM_INTERFACE "',"
+	"path='" UDISKS2_PATH "'";
+
 class UdisksNeighborExplorer final
 	: public NeighborExplorer {
 
@@ -106,19 +111,19 @@ UdisksNeighborExplorer::DoOpen()
 
 	auto &connection = GetConnection();
 
+	/* this ugly try/catch cascade is only here because this
+	   method has no RAII for this method - TODO: improve this */
 	try {
 		Error error;
-		dbus_bus_add_match(connection,
-				   "type='signal',sender='" UDISKS2_INTERFACE "',"
-				   "interface='" DBUS_OM_INTERFACE "',"
-				   "path='" UDISKS2_PATH "'",
-				   error);
+		dbus_bus_add_match(connection, udisks_neighbor_match, error);
 		error.CheckThrow("DBus AddMatch error");
 
+		try {
 			dbus_connection_add_filter(connection,
 						   HandleMessage, this,
 						   nullptr);
 
+			try {
 				auto msg = Message::NewMethodCall(UDISKS2_INTERFACE,
 								  UDISKS2_PATH,
 								  DBUS_OM_INTERFACE,
@@ -126,6 +131,17 @@ UdisksNeighborExplorer::DoOpen()
 				list_request.Send(connection, *msg.Get(),
 						  std::bind(&UdisksNeighborExplorer::OnListNotify,
 							    this, std::placeholders::_1));
+			} catch (...) {
+				dbus_connection_remove_filter(connection,
+							      HandleMessage,
+							      this);
+				throw;
+			}
+		} catch (...) {
+			dbus_bus_remove_match(connection,
+					      udisks_neighbor_match, nullptr);
+			throw;
+		}
 	} catch (...) {
 		dbus_glue.Destruct();
 		throw;
@@ -145,8 +161,10 @@ UdisksNeighborExplorer::DoClose() noexcept
 		list_request.Cancel();
 	}
 
-	// TODO: remove_match
-	// TODO: remove_filter
+	auto &connection = GetConnection();
+
+	dbus_connection_remove_filter(connection, HandleMessage, this);
+	dbus_bus_remove_match(connection, udisks_neighbor_match, nullptr);
 
 	dbus_glue.Destruct();
 }

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;
 }