filesystem: allow zpool to satisfy mount

subiquity/models/filesystem.py

@@ -1788,7 +1788,13 @@ class FilesystemModel(object):
                 "unknown bootloader type {}".format(self.bootloader))
 
     def _mount_for_path(self, path):
-        return self._one(type='mount', path=path)
+        mount = self._one(type='mount', path=path)
+        if mount is not None:
+            return mount
+        zpool = self._one(type='zpool', mountpoint=path)
+        if zpool is not None:
+            return zpool
+        return None
 
     def is_root_mounted(self):
         return self._mount_for_path('/') is not None

subiquity/models/tests/test_filesystem.py

@@ -1290,3 +1290,15 @@ class TestZPool(SubiTestCase):
         self.assertEqual('zfs-1', zfs.id)
         self.assertEqual(zpool, zfs.pool)
         self.assertEqual('/ROOT', zfs.volume)
+
+
+class TestRootfs(SubiTestCase):
+    def test_zpool_may_provide_rootfs(self):
+        m = make_model()
+        make_zpool(model=m, mountpoint='/')
+        self.assertTrue(m.is_root_mounted())
+
+    def test_zpool_nonrootfs_mountpoint(self):
+        m = make_model()
+        make_zpool(model=m, mountpoint='/srv')
+        self.assertFalse(m.is_root_mounted())