tests: detect loop devices with deleted files as an invariant

When a loop device is created with a given backing file, the file itself may be deleted. The kernel keeps the reference to the file alive but it also adjusts the name of the file to have the suffix " (deleted)". We should not have loop devices with this property across tests. They might indicate that a mount sticks around and leaks through a reference somehow, or that the low-level loop-back utilities are buggy. Signed-off-by: Zygmunt Krynicki <[email protected]>
canonical · Oct 2, 2024 · 346c55e · 346c55e
1 parent 0d7c868
commit 346c55e
Showing 1 changed file with 16 additions and 1 deletion.
diff --git a/tests/lib/tools/tests.invariant b/tests/lib/tools/tests.invariant
@@ -11,6 +11,7 @@ show_help() {
 	echo "    leftover-defer-sh: defer.sh must not be left over by tests"
 	echo "    broken-snaps: snaps must not be left around that are in a broken state"
 	echo "    segmentation-violations: snapd must not have segmentation-violation errors in journal logs"
+	echo "    deleted-loop-devices: no loop devices associated with deleted files must exist"
 }
 
 if [ $# -eq 0 ]; then
@@ -207,6 +208,17 @@ check_fakestore_cleaned() {
     fi
 }
 
+check_deleted_loop_devices() {
+	n="$1" # invariant name
+
+	losetup -l | grep -F ' (deleted)' > "$TESTSTMP/tests.invariant.$n"
+	if [ -s "$TESTSTMP/tests.invariant.$n" ]; then
+		echo "tests.invariant: detected loopback devices associated with deleted files" >&2
+		cat "$TESTSTMP/tests.invariant.$n" >&2
+		return 1
+	fi
+}
+
 check_invariant() {
 	case "$1" in
 		root-files-in-home)
@@ -236,6 +248,9 @@ check_invariant() {
 		check-fakestore-cleaned)
 			check_fakestore_cleaned
 			;;
+		deleted-loop-devices)
+			check_deleted_loop_devices "$1"
+			;;
 		*)
 			echo "tests.invariant: unknown invariant $1" >&2
 			exit 1
@@ -244,7 +259,7 @@ check_invariant() {
 }
 
 main() {
-	ALL_INVARIANTS="root-files-in-home crashed-snap-confine lxcfs-mounted stray-dbus-daemon leftover-defer-sh broken-snaps cgroup-scopes segmentation-violations check-fakestore-cleaned"
+	ALL_INVARIANTS="root-files-in-home crashed-snap-confine lxcfs-mounted stray-dbus-daemon leftover-defer-sh broken-snaps cgroup-scopes segmentation-violations check-fakestore-cleaned deleted-loop-devices"
 
 	case "$action" in
 		check)