ceph-volume: allow symlinks as devices

This MR creates ability to use symlinks as devices for ceph-volume.
One example of use will include usage of custom udev rules to map disk slots in enclosures to block device labels like:

/dev/data1 -> /dev/sda
/dev/data2 -> /dev/sdb

Fixes: https://tracker.ceph.com/issues/49103

Signed-off-by: Jan Sobczak <jsobczak@cloudferro.com>
Co-authored-by: Guillaume Abrioux <gabrioux@redhat.com>

src/ceph-volume/ceph_volume/tests/util/test_device.py

@@ -230,7 +230,39 @@ def test_reject_not_acceptable_device(self, fake_call, device_info):
         disk = device.Device("/dev/dm-0")
         assert not disk.available
 
-    def test_reject_readonly_device(self, fake_call, device_info):
+    @patch('ceph_volume.util.device.os.readlink')
+    @patch('ceph_volume.util.device.os.path.islink')
+    def test_accept_symlink_to_device(self,
+                                      m_os_path_islink,
+                                      m_os_readlink,
+                                      device_info,
+                                      fake_call):
+        m_os_path_islink.return_value = True
+        m_os_readlink.return_value = '/dev/sdb'
+        data = {"/dev/sdb": {"ro": 0, "size": 5368709120}}
+        lsblk = {"TYPE": "disk"}
+        device_info(devices=data,lsblk=lsblk)
+        disk = device.Device("/dev/test_symlink")
+        print(disk)
+        print(disk.sys_api)
+        assert disk.available
+
+    @patch('ceph_volume.util.device.os.readlink')
+    @patch('ceph_volume.util.device.os.path.islink')
+    def test_reject_symlink_to_device_mapper(self,
+                                             m_os_path_islink,
+                                             m_os_readlink,
+                                             device_info,
+                                             fake_call):
+        m_os_path_islink.return_value = True
+        m_os_readlink.return_value = '/dev/dm-0'
+        data = {"/dev/mapper/mpatha": {"ro": 0, "size": 5368709120}}
+        lsblk = {"TYPE": "disk"}
+        device_info(devices=data,lsblk=lsblk)
+        disk = device.Device("/dev/mapper/mpatha")
+        assert disk.available
+
+    def test_reject_readonly_device(self, device_info, fake_call):
         data = {"/dev/cdrom": {"ro": 1}}
         lsblk = {"TYPE": "disk"}
         device_info(devices=data,lsblk=lsblk)

src/ceph-volume/ceph_volume/util/device.py

@@ -151,6 +151,13 @@ def __hash__(self):
     def _parse(self):
         if not sys_info.devices:
             sys_info.devices = disk.get_devices()
+        # check if we are a symlink
+        if os.path.islink(self.abspath):
+            temp_path = os.path.join(os.path.dirname(self.abspath),
+                                            os.readlink(self.abspath))
+            # check if we are not a device mapper
+            if "dm-" not in temp_path:
+                self.abspath = temp_path
         self.sys_api = sys_info.devices.get(self.abspath, {})
         if not self.sys_api:
             # if no device was found check if we are a partition
@@ -160,7 +167,6 @@ def _parse(self):
                 if part:
                     self.sys_api = part
                     break
-
         # if the path is not absolute, we have 'vg/lv', let's use LV name
         # to get the LV.
         if self.path[0] == '/':