Fs_rom: send signals on file removal

Clients may wish to act on missing files. In any case the fs_rom
needs to reopen a watch handle when a file is deleted, and this
sort of change to the internal state machine is propelled by
client RPC requests.

Fix #2839

repos/os/recipes/pkg/test-fs_report/runtime

@@ -39,6 +39,7 @@
 				</content>
 				<policy label_prefix="fs_report -> " root="/" writeable="yes"/>
 				<policy label_prefix="fs_rom -> "    root="/test-fs_report"/>
+				<policy label_prefix="test-fs_report -> " root="/test-fs_report" writeable="yes"/>
 			</config>
 		</start>
 		<!--
@@ -57,7 +58,7 @@
 		</start>
 		<start name="test-fs_report">
 			<resource name="RAM" quantum="4M"/>
-			<config/>
+			<config> <vfs> <fs/> </vfs> </config>
 			<route>
 				<service name="ROM"    label="devices"> <child name="fs_rom"/> </service>
 				<service name="ROM"    label="focus">   <child name="fs_rom"/> </service>

repos/os/recipes/src/test-fs_report/used_apis

@@ -2,3 +2,4 @@ base
 os
 report_session
 timer_session
+vfs

repos/os/run/fs_report.run

@@ -45,6 +45,7 @@ append config {
 			</content>
 			<policy label_prefix="fs_report -> " root="/" writeable="yes"/>
 			<policy label_prefix="fs_rom -> "    root="/test-fs_report"/>
+			<policy label_prefix="test-fs_report -> " root="/test-fs_report" writeable="yes"/>
 		</config>
 	</start>
 	<!--
@@ -63,7 +64,7 @@ append config {
 	</start>
 	<start name="test-fs_report">
 		<resource name="RAM" quantum="4M"/>
-		<config/>
+		<config> <vfs> <fs/> </vfs> </config>
 		<route>
 			<service name="ROM"    label="devices"> <child name="fs_rom"/> </service>
 			<service name="ROM"    label="focus">   <child name="fs_rom"/> </service>

repos/os/src/server/fs_rom/main.cc

@@ -100,7 +100,7 @@ class Fs_rom::Rom_session_component : public  Rpc_object<Rom_session>
 		 */
 		struct Version { unsigned value; };
 		Version _curr_version       { 0 };
-		Version _handed_out_version { ~0U };
+		Version _handed_out_version { 0 };
 
 		/**
 		 * Track if the session file or a directory is being watched
@@ -257,26 +257,18 @@ class Fs_rom::Rom_session_component : public  Rpc_object<Rom_session>
 			catch (Permission_denied) { error(_file_path, ": permission denied"); }
 			catch (...)               { error(_file_path, ": unhandled error"); };
 
+			if (_file_size > 0) {
+				memset(_file_ds.local_addr<char>(), 0x00, min(_file_size, _file_ds.size()));
+				_file_size = 0;
+			}
+
 			return false;
 		}
 
 		void _notify_client_about_new_version()
 		{
-			using namespace File_system;
-
-			if (_sigh.valid() && _curr_version.value != _handed_out_version.value) {
-
-				/* notify if the file is not empty */
-				try {
-					Node_handle file = _fs.node(_file_path.base());
-					Handle_guard g(_fs, file);
-					_file_size = _fs.status(file).size;
-				}
-				catch (...) { _file_size = 0; }
-
-				if (_file_size > 0)
-					Signal_transmitter(_sigh).submit();
-			}
+			if (_sigh.valid() && _curr_version.value != _handed_out_version.value)
+				Signal_transmitter(_sigh).submit();
 		}
 
 	public:
@@ -364,11 +356,9 @@ class Fs_rom::Rom_session_component : public  Rpc_object<Rom_session>
 					_open_watch_handle();
 				}
 
-				if (_watching_file) {
-					/* notify the client of the change */
-					_curr_version = Version { _curr_version.value + 1 };
-					_notify_client_about_new_version();
-				}
+				/* notify the client of the change */
+				_curr_version = Version { _curr_version.value + 1 };
+				_notify_client_about_new_version();
 				return;
 
 			case File_system::Packet_descriptor::READ: {
@@ -466,7 +456,6 @@ class Fs_rom::Rom_root : public Root_component<Fs_rom::Rom_session_component>
 			Root_component<Rom_session_component>(env.ep(), md_alloc),
 			_env(env)
 		{
-			/* Process CONTENT_CHANGED acknowledgement packets at the entrypoint  */
 			_fs.sigh_ack_avail(_packet_handler);
 
 			env.parent().announce(env.ep().manage(*this));

repos/os/src/test/fs_report/main.cc

@@ -11,6 +11,8 @@
  * under the terms of the GNU Affero General Public License version 3.
  */
 
+#include <vfs/simple_env.h>
+#include <base/heap.h>
 #include <base/log.h>
 #include <base/component.h>
 #include <base/attached_rom_dataspace.h>
@@ -28,8 +30,24 @@ struct Test::Main
 {
 	Env &_env;
 
+	Genode::Heap _heap { _env.pd(), _env.rm() };
+
 	Timer::Connection _timer { _env };
 
+	Genode::Attached_rom_dataspace _config_rom { _env, "config" };
+
+	Genode::Xml_node vfs_config()
+	{
+		try { return _config_rom.xml().sub_node("vfs"); }
+		catch (...) {
+			Genode::error("VFS not configured");
+			_env.parent().exit(~0);
+			throw;
+		}
+	}
+
+	Vfs::Simple_env _vfs_env { _env, _heap, vfs_config() };
+
 	Constructible<Reporter> _devices_reporter { };
 	Constructible<Reporter> _focus_reporter   { };
 
@@ -50,6 +68,9 @@ struct Test::Main
 	Signal_handler<Main> _focus_rom_update_handler {
 		_env.ep(), *this, &Main::_handle_focus_rom_update };
 
+	Signal_handler<Main> _focus_removal_handler {
+		_env.ep(), *this, &Main::_handle_focus_removal };
+
 	Constructible<Timer::One_shot_timeout<Main> > _one_shot_timeout { };
 
 	void _handle_init()
@@ -84,7 +105,7 @@ struct Test::Main
 
 		_devices_rom->update();
 		if (_devices_rom->xml().attribute_value("version", Version()) != "version 2") {
-			error("unexpected content of \"devices\" ROM after update");
+			error("(6) unexpected content of \"devices\" ROM after update");
 			throw Exception();
 		}
 
@@ -111,12 +132,29 @@ struct Test::Main
 		_focus_rom->update();
 
 		if (_focus_rom->xml().attribute_value("version", Version()) != "focus version 1") {
-			error("unexpected content of \"focus\" ROM");
+			error("(9) unexpected content of \"focus\" ROM");
 			throw Exception();
 		}
 
 		log("(9) received expected focus ROM content");
 
+		_focus_rom->sigh(_focus_removal_handler);
+
+		log("(10) remove focus file");
+		_vfs_env.root_dir().unlink("focus");
+	}
+
+	void _handle_focus_removal()
+	{
+		_focus_rom->update();
+
+		if (!_focus_rom->xml().has_type("empty")) {
+			error("(11) unexpected content of \"focus\" ROM");
+			throw Exception();
+		}
+
+		log("(11) received empty focus ROM");
+
 		/* test completed successfully */
 		_env.parent().exit(0);
 	}

repos/os/src/test/fs_report/target.mk

@@ -1,4 +1,4 @@
 TARGET = test-fs_report
 SRC_CC = main.cc
-LIBS   = base
+LIBS   = base vfs