storage: exclude erase-install scenarios that renumber partitions

The /storage/v2 API currently does not deal well with partitions renumbering. For logical partitions, renumbering automatically occurs when a partition is removed or added. This leads to inconsistencies and mismatches in the info returned by the /storage/v2 API ; as reported in https://launchpad.net/bugs/2091172 The result of the these inconsistencies gets reflected in the summary of storage changes shown to the user in the UI. Having wrong information there will scare people away. For now, we will avoid producing guided erase and install scenarios if it means renumbering partitions. Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>
canonical · Jan 16, 2025 · 74a781c · 74a781c
1 parent d4fa209
commit 74a781c
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Showing 2 changed files with 16 additions and 3 deletions.
diff --git a/subiquity/server/controllers/filesystem.py b/subiquity/server/controllers/filesystem.py
@@ -1303,6 +1303,17 @@ def available_erase_install_scenarios(
                 if partition.os is None:
                     continue
 
+                if (
+                    partition.is_logical
+                    and disk.partitions_by_number()[-1] != partition
+                ):
+                    # FIXME If we remove this partition, the subsequent logical
+                    # partitions will be renumbered. This will cause various
+                    # mismatches in the info returned by /storage/v2. For now,
+                    # we exclude this scenario.
+                    # See LP: #2091172
+                    continue
+
                 # Make an ephemeral copy of the disk object with the relevant
                 # partition removed. Then it's as if we're installing in the
                 # resulting gap (which will include free space that was

diff --git a/subiquity/server/controllers/tests/test_filesystem.py b/subiquity/server/controllers/tests/test_filesystem.py
@@ -1822,10 +1822,12 @@ async def test_available_erase_install_scenarios__with_logical_partitions(self):
         sorted_scenarios = sorted(
             scenarios, key=lambda sc: (sc.disk_id, sc.partition_number)
         )
+        # Currently we expect only two scenarios because of the workaround for
+        # LP: #2091172. If we drop the workaround, we will have a third
+        # scenario for partition p5.
         self.assertEqual(1, sorted_scenarios[0].partition_number)
-        self.assertEqual(5, sorted_scenarios[1].partition_number)
-        self.assertEqual(6, sorted_scenarios[2].partition_number)
-        self.assertEqual(3, len(sorted_scenarios))
+        self.assertEqual(6, sorted_scenarios[1].partition_number)
+        self.assertEqual(2, len(sorted_scenarios))
 
     async def test_resize_has_enough_room_for_partitions__one_primary(self):
         await self._setup(Bootloader.NONE, "gpt", fix_bios=True)