[glib/wip/oholy/bind-mounts: 1/2] gio: Add g_unix_mount_get_root_path

[Ondrej Holy <oholy src gnome org>]

commit e1fa5ffb91e74376394fe17612015d44fec82366
Author: Ondrej Holy <oholy redhat com>
Date:   Thu Apr 26 10:37:33 2018 +0200

    gio: Add g_unix_mount_get_root_path
    
    Currently, there isn't API to determine root path for mounts created
    over bind operation (or btrfs subvolumes). This causes issues to our
    volume monitors if there is multiple mounts for one device, which can
    happen with libmount-based implementation currently. Let's propagate
    root path from libmount over g_unix_mount_get_root_path, so we can
    handle this somehow in our volume monitors.
    
    https://gitlab.gnome.org/GNOME/glib/issues/1271

 docs/reference/gio/gio-sections.txt |  1 +
 gio/gunixmounts.c                   | 39 ++++++++++++++++++++++++++++++++++++-
 gio/gunixmounts.h                   |  2 ++
 3 files changed, 41 insertions(+), 1 deletion(-)
---
diff --git a/docs/reference/gio/gio-sections.txt b/docs/reference/gio/gio-sections.txt
index f7efd2bf4..6ba453f28 100644
--- a/docs/reference/gio/gio-sections.txt
+++ b/docs/reference/gio/gio-sections.txt
@@ -1552,6 +1552,7 @@ g_unix_mount_compare
 g_unix_mount_copy
 g_unix_mount_get_mount_path
 g_unix_mount_get_device_path
+g_unix_mount_get_root_path
 g_unix_mount_get_fs_type
 g_unix_mount_get_options
 g_unix_mount_is_readonly
diff --git a/gio/gunixmounts.c b/gio/gunixmounts.c
index 355329c19..f5a8ecf41 100644
--- a/gio/gunixmounts.c
+++ b/gio/gunixmounts.c
@@ -125,6 +125,7 @@ typedef enum {
 struct _GUnixMountEntry {
   char *mount_path;
   char *device_path;
+  char *root_path;
   char *filesystem_type;
   char *options;
   gboolean is_read_only;
@@ -408,6 +409,7 @@ guess_system_internal (const char *mountpoint,
 static GUnixMountEntry *
 create_unix_mount_entry (const char *device_path,
                          const char *mount_path,
+                         const char *root_path,
                          const char *filesystem_type,
                          const char *options,
                          gboolean    is_read_only)
@@ -417,6 +419,7 @@ create_unix_mount_entry (const char *device_path,
   mount_entry = g_new0 (GUnixMountEntry, 1);
   mount_entry->device_path = g_strdup (device_path);
   mount_entry->mount_path = g_strdup (mount_path);
+  mount_entry->root_path = g_strdup (root_path);
   mount_entry->filesystem_type = g_strdup (filesystem_type);
   mount_entry->options = g_strdup (options);
   mount_entry->is_read_only = is_read_only;
@@ -496,6 +499,7 @@ _g_get_unix_mounts (void)
 
       mount_entry = create_unix_mount_entry (device_path,
                                              mnt_fs_get_target (fs),
+                                             mnt_fs_get_root (fs),
                                              mnt_fs_get_fstype (fs),
                                              mnt_fs_get_options (fs),
                                              is_read_only);
@@ -591,6 +595,7 @@ _g_get_unix_mounts (void)
 
       mount_entry = create_unix_mount_entry (device_path,
                                              mntent->mnt_dir,
+                                             NULL,
                                              mntent->mnt_type,
                                              mntent->mnt_opts,
                                              is_read_only);
@@ -705,6 +710,7 @@ _g_get_unix_mounts (void)
 
       mount_entry = create_unix_mount_entry (mntent.mnt_special,
                                              mntent.mnt_mountp,
+                                             NULL,
                                              mntent.mnt_fstype,
                                              mntent.mnt_opts,
                                              is_read_only);
@@ -772,6 +778,7 @@ _g_get_unix_mounts (void)
 
       mount_entry = create_unix_mount_entry (vmt2dataptr (vmount_info, VMT_OBJECT),
                                              vmt2dataptr (vmount_info, VMT_STUB),
+                                             NULL,
                                              fs_info == NULL ? "unknown" : fs_info->vfsent_name,
                                              NULL,
                                              is_read_only);
@@ -848,6 +855,7 @@ _g_get_unix_mounts (void)
 
       mount_entry = create_unix_mount_entry (mntent[i].f_mntfromname,
                                              mntent[i].f_mntonname,
+                                             NULL,
                                              mntent[i].f_fstypename,
                                              NULL,
                                              is_read_only);
@@ -1992,6 +2000,7 @@ g_unix_mount_free (GUnixMountEntry *mount_entry)
 
   g_free (mount_entry->mount_path);
   g_free (mount_entry->device_path);
+  g_free (mount_entry->root_path);
   g_free (mount_entry->filesystem_type);
   g_free (mount_entry->options);
   g_free (mount_entry);
@@ -2017,6 +2026,7 @@ g_unix_mount_copy (GUnixMountEntry *mount_entry)
   copy = g_new0 (GUnixMountEntry, 1);
   copy->mount_path = g_strdup (mount_entry->mount_path);
   copy->device_path = g_strdup (mount_entry->device_path);
+  copy->root_path = g_strdup (mount_entry->root_path);
   copy->filesystem_type = g_strdup (mount_entry->filesystem_type);
   copy->options = g_strdup (mount_entry->options);
   copy->is_read_only = mount_entry->is_read_only;
@@ -2097,7 +2107,11 @@ g_unix_mount_compare (GUnixMountEntry *mount1,
   res = g_strcmp0 (mount1->device_path, mount2->device_path);
   if (res != 0)
     return res;
-       
+
+  res = g_strcmp0 (mount1->root_path, mount2->root_path);
+  if (res != 0)
+    return res;
+
   res = g_strcmp0 (mount1->filesystem_type, mount2->filesystem_type);
   if (res != 0)
     return res;
@@ -2145,6 +2159,29 @@ g_unix_mount_get_device_path (GUnixMountEntry *mount_entry)
   return mount_entry->device_path;
 }
 
+/**
+ * g_unix_mount_get_root_path:
+ * @mount_entry: a #GUnixMountEntry.
+ * 
+ * Gets the root of the mount within the filesystem. This is useful e.g. for
+ * mounts created by bind operation, or btrfs subvolumes.
+ * 
+ * For example, the root path is equal to "/" for mount created by
+ * "mount /dev/sda1 /mnt/foo" and "/bar" for
+ * "mount --bind /mnt/foo/bar /mnt/bar".
+ *
+ * Returns: (nullable): a string containing the root, or %NULL if not supported.
+ *
+ * Since: 2.60
+ */
+const gchar *
+g_unix_mount_get_root_path (GUnixMountEntry *mount_entry)
+{
+  g_return_val_if_fail (mount_entry != NULL, NULL);
+
+  return mount_entry->root_path;
+}
+
 /**
  * g_unix_mount_get_fs_type:
  * @mount_entry: a #GUnixMount.
diff --git a/gio/gunixmounts.h b/gio/gunixmounts.h
index a392d497f..fe8e24160 100644
--- a/gio/gunixmounts.h
+++ b/gio/gunixmounts.h
@@ -79,6 +79,8 @@ GLIB_AVAILABLE_IN_ALL
 const char *   g_unix_mount_get_mount_path          (GUnixMountEntry    *mount_entry);
 GLIB_AVAILABLE_IN_ALL
 const char *   g_unix_mount_get_device_path         (GUnixMountEntry    *mount_entry);
+GLIB_AVAILABLE_IN_2_60
+const char *   g_unix_mount_get_root_path           (GUnixMountEntry    *mount_entry);
 GLIB_AVAILABLE_IN_ALL
 const char *   g_unix_mount_get_fs_type             (GUnixMountEntry    *mount_entry);
 GLIB_AVAILABLE_IN_2_58