Use any disk for /boot regardless of its size

Apparently, the disks which're bigger than 2T were excluded from list
of bootable disks if possible. Just because in the past, those disks
were unrecognized by BIOS (or UEFI under CSM).

In fact, it was just misconfiguration of RAID controller or BIOS
itself.

GRUB uses BIOS INT13h in order to find all available disks.
Therefore, unless particular disk is not configured as 'bootable',
there's no change for GRUB to find it.

One should configure hardware in the following way assuming that
the first disk (hd0) is bootable and is used for operating system
purposes.
In case of hardware RAID, FC multipath or any other HBA, the disk
(or lun, or whatever) which was configured as 'bootable' will be
reported as hd0 via INT13h. So, GRUB will be able to boot from it.

DocImpact
Closes-Bug: #1588260

Change-Id: I7bc729ffafa3b9d6bfe8521fa38599d36d02f7e1
(cherry picked from commit e2a20044b2)

fuel_agent/drivers/nailgun.py

@@ -147,11 +147,7 @@ class Nailgun(BaseDataDriver):
         # by fuel-agent (it always installs BIOS variant of
         # grub)
         # * grub bug (http://savannah.gnu.org/bugs/?41883)
-        # NOTE(kozhukalov): On some hardware GRUB is not able
+        disks = self.ks_disks
-        # to see disks larger than 2T due to firmware bugs,
-        # so we'd better avoid placing /boot on such
-        # huge disks if it is possible.
-        disks = self.small_ks_disks or self.ks_disks
         suitable_disks = [
             disk for disk in disks
             if ('nvme' not in disk['name'] and self._is_boot_disk(disk))
@@ -205,11 +201,6 @@ class Nailgun(BaseDataDriver):
         return [d for d in self.ks_disks
                 if d['name'].startswith('md') and self._is_os_disk(d)]
 
-    @property
-    def small_ks_disks(self):
-        """Get those disks which are smaller than 2T"""
-        return [d for d in self.ks_disks if d['size'] <= 2097152]
-
     @property
     def ks_vgs(self):
         return filter(

fuel_agent/tests/test_nailgun.py

@@ -1461,13 +1461,6 @@ class TestNailgunBootDisks(unittest2.TestCase):
         self._check_boot_disks(ks_disks_return_value, not_expected_disk,
                                expected_disks)
 
-    def test_only_small_boot_disks(self):
-        ks_disks_return_value = self.disks + [self.big_disk]
-        not_expected_disk = self.big_disk
-        expected_disks = self.disks
-        self._check_boot_disks(ks_disks_return_value, not_expected_disk,
-                               expected_disks)
-
     def test_boot_disks_no_nvme(self):
         ks_disks_return_value = self.disks + [self.nvme_disk]
         not_expected_disk = self.nvme_disk
@@ -1823,13 +1816,14 @@ class TestNailgunMockedMeta(unittest2.TestCase):
 
     def test_boot_partition_ok_first_disk_huge(self, mock_lbd,
                                                mock_image_meta):
+        # /boot should be on first disk even if it's huge
         data = copy.deepcopy(PROVISION_SAMPLE_DATA)
         data['ks_meta']['pm_data']['ks_spaces'] = FIRST_DISK_HUGE_KS_SPACES
         mock_lbd.return_value = LIST_BLOCK_DEVICES_SAMPLE
         drv = nailgun.Nailgun(data)
         self.assertEqual(
             drv.partition_scheme.fs_by_mount('/boot').device,
-            '/dev/sdb3')
+            '/dev/sda3')
 
     def test_boot_partition_ok_many_huge_disks(self, mock_lbd,
                                                mock_image_meta):