diff --git a/linux-5.14-rc5/include/linux/hermit_types.h b/linux-5.14-rc5/include/linux/hermit_types.h
index 832f8012d..63d864011 100644
--- a/linux-5.14-rc5/include/linux/hermit_types.h
+++ b/linux-5.14-rc5/include/linux/hermit_types.h
@@ -21,6 +21,8 @@ struct hmt_work_struct {
  * swap stats to control async swap out
  */
 struct hmt_swap_ctrl {
+	// `lock` must be the first field in the struct to avoid breaking
+	// `hmt_clear_locked_swap_ctrl()`.
 	spinlock_t lock;
 	atomic_t sthd_cnt;
 	atomic_t active_sthd_cnt;
diff --git a/linux-5.14-rc5/mm/hermit_utils.c b/linux-5.14-rc5/mm/hermit_utils.c
index aaf5a0b1f..02e82f008 100644
--- a/linux-5.14-rc5/mm/hermit_utils.c
+++ b/linux-5.14-rc5/mm/hermit_utils.c
@@ -179,13 +179,20 @@ static inline void hmt_update_low_watermark(struct mem_cgroup *memcg,
 	}
 }
 
+// Resets a locked `hmt_swap_ctrl` without dropping the lock.
+// We assume `offsetof(hmt_swap_ctrl, lock) = 0`.
+static void hmt_clear_locked_swap_ctrl(struct hmt_swap_ctrl *sc)
+{
+	memset(sc + sizeof(sc->lock), 0, sizeof(*sc) - sizeof(sc->lock));
+}
+
 // must hold sc->lock
 inline void hmt_update_swap_ctrl(struct mem_cgroup *memcg,
 				 struct hmt_swap_ctrl *sc)
 {
 	const int UPD_PERIOD = 1000; // update swap-in tput per UPD_PERIOD us
 	if (sc->swin_ts[0] == 0) {
-		memset(sc, 0, sizeof(struct hmt_swap_ctrl));
+		hmt_clear_locked_swap_ctrl(sc);
 		sc->swin_ts[0] = get_cycles_light();
 		sc->nr_pg_charged[0] = atomic64_read(&memcg->total_pg_charge);
 		return;
@@ -311,7 +318,7 @@ void hermit_init_memcg(struct mem_cgroup *memcg)
 		return;
 
 	memset(&memcg->hmt_sc, 0, sizeof(struct hmt_swap_ctrl));
-	memcg->hmt_sc.lock = __SPIN_LOCK_UNLOCKED(memcg->hmt_sc.lock);
+	spin_lock_init(&memcg->hmt_sc.lock);
 	for (i = 0; i < HMT_MAX_NR_STHDS; i++) {
 		INIT_WORK(&memcg->sthds[i].work, hermit_high_work_func);
 		memcg->sthds[i].id = i;