fix detection of mounted partitions

Even if we are going to ignore a mountpoint, we still need to process
its children...

Add machine config where the installer is running from a partition of a
disk you might want to install to, and an api test.

subiquity/models/filesystem.py

@@ -1292,15 +1292,19 @@ class FilesystemModel(object):
                 continue
             majmin_to_dev[f'{major}:{minor}'] = obj
 
+        log.debug("majmin_to_dev %s", majmin_to_dev)
+
         mounts = list(self._probe_data.get('mount', []))
         while mounts:
             mount = mounts.pop(0)
+            mounts.extend(mount.get('children', []))
             if mount['target'].startswith(self.target):
                 # Completely ignore mounts under /target, they are probably
                 # leftovers from a previous install attempt.
                 continue
             if 'maj:min' not in mount:
                 continue
+            log.debug("considering mount of %s", mount['maj:min'])
             obj = majmin_to_dev.get(mount['maj:min'])
             if obj is None:
                 continue
@@ -1312,7 +1316,6 @@ class FilesystemModel(object):
                 if isinstance(o, Disk):
                     o._has_in_use_partition = True
                 work.extend(dependencies(o))
-            mounts.extend(mount.get('children', []))
 
         # This is a special hack for the install media. When written to a USB
         # stick or similar, both the block device for the whole drive and for

subiquity/tests/api/test_api.py

@@ -2075,3 +2075,17 @@ class TestActiveDirectory(TestAPI):
         # manager will fail to POST /shutdown.
         except aiohttp.client_exceptions.ClientOSError:
             pass
+
+
+class TestMountDetection(TestAPI):
+    @timeout()
+    async def test_mount_detection(self):
+        # Test that the partition the installer is running from is
+        # correctly identified as mounted.
+        cfg = 'examples/machines/booted-from-rp.json'
+        async with start_server(cfg) as instance:
+            result = await instance.get('/storage/v2')
+            [disk1] = result['disks']
+            self.assertTrue(disk1['has_in_use_partition'])
+            disk1p2 = disk1['partitions'][1]
+            self.assertTrue(disk1p2['is_in_use'])