diff --git a/drivers/md/dm-queue-length.c b/drivers/md/dm-queue-length.c
index 51d8229..aeea3b7 100644
--- a/drivers/md/dm-queue-length.c
+++ b/drivers/md/dm-queue-length.c
@@ -29,6 +29,7 @@
 struct selector {
 	struct list_head	valid_paths;
 	struct list_head	failed_paths;
+	spinlock_t lock;
 };
 
 struct path_info {
@@ -45,6 +46,7 @@
 	if (s) {
 		INIT_LIST_HEAD(&s->valid_paths);
 		INIT_LIST_HEAD(&s->failed_paths);
+		spin_lock_init(&s->lock);
 	}
 
 	return s;
@@ -113,6 +115,7 @@
 	struct path_info *pi;
 	unsigned repeat_count = QL_MIN_IO;
 	char dummy;
+	unsigned long flags;
 
 	/*
 	 * Arguments: [<repeat_count>]
@@ -147,7 +150,9 @@
 
 	path->pscontext = pi;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_add_tail(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
@@ -156,16 +161,22 @@
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = path->pscontext;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move(&pi->list, &s->failed_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static int ql_reinstate_path(struct path_selector *ps, struct dm_path *path)
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = path->pscontext;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move_tail(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
@@ -178,9 +189,12 @@
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = NULL, *best = NULL;
+	struct dm_path *ret = NULL;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	if (list_empty(&s->valid_paths))
-		return NULL;
+		goto out;
 
 	/* Change preferred (first in list) path to evenly balance. */
 	list_move_tail(s->valid_paths.next, &s->valid_paths);
@@ -195,11 +209,14 @@
 	}
 
 	if (!best)
-		return NULL;
+		goto out;
 
 	*repeat_count = best->repeat_count;
 
-	return best->path;
+	ret = best->path;
+out:
+	spin_unlock_irqrestore(&s->lock, flags);
+	return ret;
 }
 
 static int ql_start_io(struct path_selector *ps, struct dm_path *path,