test: add test cases for journal corruption on btrfs

For issue #24150 and #31222.

test/test-functions

@@ -2103,7 +2103,7 @@ install_testuser() {
     # create unprivileged user for user manager tests
     mkdir -p "${initdir:?}/etc/sysusers.d"
     cat >"$initdir/etc/sysusers.d/testuser.conf" <<EOF
-u testuser    4711     "Test User" /home/testuser
+u testuser    4711     "Test User" /home/testuser /bin/bash
 EOF
 
     mkdir -p "$initdir/home/testuser"

test/units/testsuite-04.journal-corrupt.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -eux
+set -o pipefail
+
+journalctl --rotate --vacuum-files=1
+# Nuke all archived journals, so we start with a clean slate
+rm -f "/var/log/journal/$(</etc/machine-id)"/system@*.journal
+rm -f "/var/log/journal/$(</etc/machine-id)"/user-*@*.journal
+journalctl --header | grep path
+
+# Make sure the user instance is active when we rotate journals
+systemd-run --unit user-sleep.service --user -M testuser@ sleep infinity
+
+for _ in {0..9}; do
+    journalctl --rotate
+    journalctl --sync
+    SYSTEMD_LOG_LEVEL=debug journalctl -n1 -q
+    (! journalctl -n0 -q |& grep corrupted)
+done
+
+systemctl stop --user -M testuser@ user-sleep.service
+
+journalctl --sync
+journalctl --rotate --vacuum-files=1
+# Nuke all archived journals, so we start with a clean slate
+rm -f "/var/log/journal/$(</etc/machine-id)"/system@*.journal
+rm -f "/var/log/journal/$(</etc/machine-id)/"user-*@*.journal
+journalctl --header | grep path
+
+for _ in {0..9}; do
+    journalctl --rotate --vacuum-files=1
+    journalctl --sync
+    SYSTEMD_LOG_LEVEL=debug journalctl -n1 -q
+    (! journalctl -n0 -q |& grep corrupted)
+done