devices/lvm2.lv: add support for lvm devices files

LVM2 introduced system.devices as an alternative way to filter
devices. Since we create devices in a stage the devices won't be
added to the /etc/lvm/devices/system.devices file since /etc/ is
inside the container. As a result the we can't see these devices
and will fail with "Could not find parent device".
Therefore we add support for managing our own per-service devices
file, iff a `system.devices` is present.

devices/org.osbuild.lvm2.lv

@@ -58,13 +58,45 @@ class LVService(devices.DeviceService):
         super().__init__(args)
         self.fullname = None
         self.target = None
+        self.devices_file = None
 
-    @staticmethod
-    def lv_set_active(fullname: str, status: bool):
+    def manage_devices_file(self, device: str):
+        # if LVM2 uses system.devices file, the LVM2 physical device we created
+        # inside the stage won't be seen since it wont be added to `system.devices`
+        # so we need to manage our own devices file
+
+        if not os.path.exists("/etc/lvm/devices/system.devices"):
+            return
+
+        self.devices_file = f"osbuild-{os.getpid()}.devices"
+        print(f"adding device to '{self.devices_file}'")
+
+        cmd = [
+            "lvmdevices",
+            "--adddev", device,
+            "--devicesfile", self.devices_file
+        ]
+
+        res = subprocess.run(cmd,
+                             check=False,
+                             stdout=subprocess.DEVNULL,
+                             stderr=subprocess.PIPE,
+                             encoding="UTF-8")
+
+        if res.returncode != 0:
+            data = res.stderr.strip()
+            msg = f"Failed to add '{device}' to '{self.devices_file}': {data}"
+            raise RuntimeError(msg)
+
+    def lv_set_active(self, fullname: str, status: bool):
         mode = "y" if status else "n"
         cmd = [
             "lvchange", "--activate", mode, fullname
         ]
+
+        if self.devices_file:
+            cmd += ["--devicesfile", self.devices_file]
+
         res = subprocess.run(cmd,
                              check=False,
                              stdout=subprocess.DEVNULL,
@@ -76,8 +108,7 @@ class LVService(devices.DeviceService):
             msg = f"Failed to set LV device ({fullname}) status: {data}"
             raise RuntimeError(msg)
 
-    @staticmethod
-    def volume_group_for_device(device: str) -> str:
+    def volume_group_for_device(self, device: str) -> str:
         # Find the volume group that belongs to the device specified via `parent`
         vg_name = None
         count = 0
@@ -86,6 +117,9 @@ class LVService(devices.DeviceService):
             "pvdisplay", "-C", "--noheadings", "-o", "vg_name", device
         ]
 
+        if self.devices_file:
+            cmd += ["--devicesfile", self.devices_file]
+
         while True:
             res = subprocess.run(cmd,
                                  check=False,
@@ -110,8 +144,7 @@ class LVService(devices.DeviceService):
 
         return vg_name
 
-    @staticmethod
-    def device_for_logical_volume(vg_name: str, volume: str) -> Tuple[int, int]:
+    def device_for_logical_volume(self, vg_name: str, volume: str) -> Tuple[int, int]:
         # Now that we have the volume group, find the specified logical volume and its device path
 
         cmd = [
@@ -122,6 +155,9 @@ class LVService(devices.DeviceService):
             vg_name
         ]
 
+        if self.devices_file:
+            cmd += ["--devicesfile", self.devices_file]
+
         res = subprocess.run(cmd,
                              check=False,
                              stdout=subprocess.PIPE,
@@ -144,6 +180,9 @@ class LVService(devices.DeviceService):
         assert not parent.startswith("/")
         parent_path = os.path.join("/dev", parent)
 
+        # Add the device to a lvm devices file on supported systems
+        self.manage_devices_file(parent_path)
+
         # Find the volume group that belongs to the device specified
         # via `parent`
         vg = self.volume_group_for_device(parent_path)
@@ -181,6 +220,10 @@ class LVService(devices.DeviceService):
             self.lv_set_active(self.fullname, False)
             self.fullname = None
 
+        if self.devices_file:
+            os.unlink(os.path.join("/etc/lvm/devices", self.devices_file))
+            self.devices_file = None
+
 
 def main():
     service = LVService.from_args(sys.argv[1:])