Daan De MeyerandLuca Boccassi 3978b076af loop-util: shortcut block device fd when it carries no partition table
663f0bf5cb stopped reusing the original block device fd whenever
partition scanning was requested (LO_FLAGS_PARTSCAN) but couldn't be
enabled on the device, so that nested partition tables on devices the
kernel won't scan (e.g. the pmOS/android case) get exposed via a real
loop device.

However that also forced a pointless loop device for any partition that
carries a file system directly, e.g. a btrfs subvolume mounted via
MountImages=. For multi-device btrfs this is fatal: the kernel rejects
seeing the same member via both the original partition and the loop
device, and the mount fails.

A loop device is only ever needed here to expose a nested partition
table. So only refuse the shortcut when the device actually carries one,
probed via gpt_probe(), instead of whenever partition scanning is
disabled. Devices carrying a file system directly (or nothing) take the
shortcut as before.

Add an integration test to cover the failure scenario of the original
issue.

Fixes: https://github.com/systemd/systemd/issues/42520
Replaces: https://github.com/systemd/systemd/pull/42576
Follow-up for 663f0bf5cb79ecaf6dd71441ecdc9dc401e7eae6

Co-Authored-By: Luca Boccassi <luca.boccassi@gmail.com>
Co-developed-by: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-16 00:16:05 +01:00
2022-04-26 09:13:57 +00:00
2026-06-04 18:08:38 +01:00
2025-03-07 17:27:20 +01:00
2026-04-18 14:24:47 +01:00
2025-06-05 14:39:20 +02:00
2026-03-06 08:55:55 +01:00
2025-10-07 13:00:12 +01:00
2026-06-04 11:26:27 +01:00
2026-06-04 11:26:26 +01:00
2026-06-14 07:13:10 +02:00

Systemd

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