selftests: net: io_uring_zerocopy: enable io_uring for the test

The io_uring_zerocopy.sh kselftest assumes that io_uring support is
enabled on the host system. When io_uring is disabled via the
kernel.io_uring_disabled sysctl, the test fails.

Explicitly enable io_uring for the test by setting
kernel.io_uring_disabled=0.

Save the original value of kernel.io_uring_disabled before changing
it and restore it in cleanup handler to ensure the system state is
restored regardless of test outcome.

Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Link: https://patch.msgid.link/20260321215908.175465-5-aleksey.oladko@virtuozzo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/io_uring_zerocopy_tx.sh

@@ -77,9 +77,13 @@ esac
 
 # Start of state changes: install cleanup handler
 
+old_io_uring_disabled=0
 cleanup() {
 	ip netns del "${NS2}"
 	ip netns del "${NS1}"
+	if [ "$old_io_uring_disabled" -ne 0 ]; then
+		sysctl -w -q kernel.io_uring_disabled="$old_io_uring_disabled" 2>/dev/null || true
+	fi
 }
 
 trap cleanup EXIT
@@ -122,5 +126,10 @@ do_test() {
 	wait
 }
 
+old_io_uring_disabled=$(sysctl -n kernel.io_uring_disabled 2>/dev/null || echo "0")
+if [ "$old_io_uring_disabled" -ne 0 ]; then
+	sysctl -w -q kernel.io_uring_disabled=0
+fi
+
 do_test "${EXTRA_ARGS}"
 echo ok