diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 301db0f..69a2d51 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1180,6 +1180,7 @@
 static void process_discard(struct thin_c *tc, struct bio *bio)
 {
 	int r;
+	unsigned long flags;
 	struct pool *pool = tc->pool;
 	struct cell *cell, *cell2;
 	struct cell_key key, key2;
@@ -1221,7 +1222,9 @@
 			m->bio = bio;
 
 			if (!ds_add_work(&pool->all_io_ds, &m->list)) {
+				spin_lock_irqsave(&pool->lock, flags);
 				list_add(&m->list, &pool->prepared_discards);
+				spin_unlock_irqrestore(&pool->lock, flags);
 				wake_worker(pool);
 			}
 		} else {
@@ -2629,8 +2632,10 @@
 	if (h->all_io_entry) {
 		INIT_LIST_HEAD(&work);
 		ds_dec(h->all_io_entry, &work);
+		spin_lock_irqsave(&pool->lock, flags);
 		list_for_each_entry_safe(m, tmp, &work, list)
 			list_add(&m->list, &pool->prepared_discards);
+		spin_unlock_irqrestore(&pool->lock, flags);
 	}
 
 	mempool_free(h, pool->endio_hook_pool);