gio: Add API for identifying system FS types and device paths

This is needed by gnome-control-center and gnome-settings-daemon; it
makes existing checks from gunixmounts.c public.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=788927

docs/reference/gio/gio-sections.txt

@@ -1571,6 +1571,8 @@ g_unix_mount_monitor_get
 g_unix_mount_monitor_new
 g_unix_mount_monitor_set_rate_limit
 g_unix_is_mount_path_system_internal
+g_unix_is_system_fs_type
+g_unix_is_system_device_path
 <SUBSECTION Standard>
 GUnixMountMonitorClass
 G_UNIX_MOUNT_MONITOR

gio/gunixmounts.c

@@ -281,10 +281,23 @@ g_unix_is_mount_path_system_internal (const char *mount_path)
   return FALSE;
 }
 
-static gboolean
-guess_system_internal (const char *mountpoint,
-		       const char *fs,
-		       const char *device)
+/**
+ * g_unix_is_system_fs_type:
+ * @fs_type: a file system type, e.g. `procfs` or `tmpfs`
+ *
+ * Determines if @fs_type is considered a type of file system which is only
+ * used in implementation of the OS. This is primarily used for hiding
+ * mounted volumes that are intended as APIs for programs to read, and system
+ * administrators at a shell; rather than something that should, for example,
+ * appear in a GUI. For example, the Linux `/proc` filesystem.
+ *
+ * The list of file system types considered ‘system’ ones may change over time.
+ *
+ * Returns: %TRUE if @fs_type is considered an implementation detail of the OS.
+ * Since: 2.56
+ */
+gboolean
+g_unix_is_system_fs_type (const char *fs_type)
 {
   const char *ignore_fs[] = {
     "adfs",
@@ -336,6 +349,31 @@ guess_system_internal (const char *mountpoint,
     "zfs",
     NULL
   };
+
+  g_return_val_if_fail (fs_type != NULL && *fs_type != '\0', FALSE);
+
+  return is_in (fs_type, ignore_fs);
+}
+
+/**
+ * g_unix_is_system_device_path:
+ * @fs_type: a device path, e.g. `/dev/loop0` or `nfsd`
+ *
+ * Determines if @device_path is considered a block device path which is only
+ * used in implementation of the OS. This is primarily used for hiding
+ * mounted volumes that are intended as APIs for programs to read, and system
+ * administrators at a shell; rather than something that should, for example,
+ * appear in a GUI. For example, the Linux `/proc` filesystem.
+ *
+ * The list of device paths considered ‘system’ ones may change over time.
+ *
+ * Returns: %TRUE if @device_path is considered an implementation detail of
+ *    the OS.
+ * Since: 2.56
+ */
+gboolean
+g_unix_is_system_device_path (const char *device_path)
+{
   const char *ignore_devices[] = {
     "none",
     "sunrpc",
@@ -346,10 +384,20 @@ guess_system_internal (const char *mountpoint,
     NULL
   };
 
-  if (is_in (fs, ignore_fs))
+  g_return_val_if_fail (device_path != NULL && *device_path != '\0', FALSE);
+
+  return is_in (device_path, ignore_devices);
+}
+
+static gboolean
+guess_system_internal (const char *mountpoint,
+		       const char *fs,
+		       const char *device)
+{
+  if (g_unix_is_system_fs_type (fs))
     return TRUE;
   
-  if (is_in (device, ignore_devices))
+  if (g_unix_is_system_device_path (device))
     return TRUE;
 
   if (g_unix_is_mount_path_system_internal (mountpoint))
@@ -2106,7 +2154,12 @@ g_unix_mount_is_readonly (GUnixMountEntry *mount_entry)
  * g_unix_mount_is_system_internal:
  * @mount_entry: a #GUnixMount.
  *
- * Checks if a unix mount is a system path.
+ * Checks if a Unix mount is a system mount. This is the Boolean OR of
+ * g_unix_is_system_fs_type(), g_unix_is_system_device_path() and
+ * g_unix_is_mount_path_system_internal() on @mount_entry’s properties.
+ * 
+ * The definition of what a ‘system’ mount entry is may change over time as new
+ * file system types and device paths are ignored.
  *
  * Returns: %TRUE if the unix mount is for a system path.
  */

gio/gunixmounts.h

@@ -151,6 +151,10 @@ void               g_unix_mount_monitor_set_rate_limit (GUnixMountMonitor *mount
 
 GLIB_AVAILABLE_IN_ALL
 gboolean g_unix_is_mount_path_system_internal (const char *mount_path);
+GLIB_AVAILABLE_IN_2_56
+gboolean g_unix_is_system_fs_type             (const char *fs_type);
+GLIB_AVAILABLE_IN_2_56
+gboolean g_unix_is_system_device_path         (const char *device_path);
 
 G_END_DECLS
 

gio/tests/Makefile.am

@@ -266,6 +266,7 @@ test_programs += \
 	socket-address				\
 	stream-rw_all				\
 	unix-fd					\
+	unix-mounts				\
 	unix-streams				\
 	g-file-info-filesystem-readonly		\
 	$(NULL)

gio/tests/meson.build

@@ -113,6 +113,7 @@ if host_machine.system() != 'windows'
     'socket-address',
     'stream-rw_all',
     'unix-fd',
+    'unix-mounts',
     'unix-streams',
     'g-file-info-filesystem-readonly',
     'gschema-compile',

gio/tests/unix-mounts.c

@@ -0,0 +1,57 @@
+/* GLib testing framework examples and tests
+ *
+ * Copyright © 2017 Endless Mobile, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <glib.h>
+
+#ifndef G_OS_UNIX
+#error This is a Unix-specific test
+#endif
+
+#include <errno.h>
+#include <locale.h>
+#include <glib/gstdio.h>
+#include <gio/gio.h>
+#include <gio/gunixmounts.h>
+
+static void
+test_is_system_fs_type (void)
+{
+  g_assert_true (g_unix_is_system_fs_type ("tmpfs"));
+  g_assert_false (g_unix_is_system_fs_type ("ext4"));
+}
+
+static void
+test_is_system_device_path (void)
+{
+  g_assert_true (g_unix_is_system_device_path ("devpts"));
+  g_assert_false (g_unix_is_system_device_path ("/"));
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  setlocale (LC_ALL, "");
+
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/unix-mounts/is-system-fs-type", test_is_system_fs_type);
+  g_test_add_func ("/unix-mounts/is-system-device-path", test_is_system_device_path);
+
+  return g_test_run ();
+}