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… new device appears Replace bare [0] indexing on the lun diff list with an explicit assertion that the new device set is non-empty, providing a clear error message about max_data_disk_count mismatch instead of an opaque IndexError.
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Pull request overview
Fixes a crash in the Storage test suite hot-add helper by replacing an unsafe empty-list index with an assertion and a safer retrieval approach when no new Linux block device is detected after attaching a disk.
Changes:
- Add an explicit non-empty assertion for newly discovered device keys when comparing
Disk.get_luns()before/after hot-add. - Replace direct
[0]indexing withnext(iter(...))after validating the set difference is non-empty. - Improve failure diagnostics by including LUN and before/after device mappings in the assertion message.
❌ AI Test Selection — FAILED74 test case(s) selected (view run) Marketplace image: canonical 0001-com-ubuntu-server-jammy 22_04-lts-gen2 latest
Test case details
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LiliDeng
approved these changes
Apr 25, 2026
LiliDeng
deleted the
bugfix/hot-add-disk-serial-index-error_240426_101331
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Summary
Fix an
IndexError: list index out of rangecrash in_hot_add_disk_serial()when a hot-added data disk does not appear as a new Linux block device after attachment.Root Cause
The method computed the set difference of device keys before vs. after hot-add, then immediately indexed
[0]on the resulting list without checking whether it was empty. If the disk was not yet visible (timing race) or failed to appear, the empty-list access raisedIndexError.Fix
[0]indexing with an explicitassert_that(...).is_not_empty()assertion that produces a clear diagnostic message including the expected LUN number.next(iter(...))to retrieve the first element safely after the assertion guarantees non-emptiness.Validation
Tested on 3 distro families with
verify_hot_add_disk_serial_premium_ssd:All lint checks pass (black, flake8, mypy).