1 files changed, 9 insertions, 5 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index f9797b244eb3..87ea95d1f533 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -504,8 +504,9 @@ static const char *blkg_dev_name(struct blkcg_gq *blkg)
  *
  * This function invokes @prfill on each blkg of @blkcg if pd for the
  * policy specified by @pol exists.  @prfill is invoked with @sf, the
- * policy data and @data.  If @show_total is %true, the sum of the return
- * values from @prfill is printed with "Total" label at the end.
+ * policy data and @data and the matching queue lock held.  If @show_total
+ * is %true, the sum of the return values from @prfill is printed with
+ * "Total" label at the end.
  *
  * This is to be used to construct print functions for
  * cftype->read_seq_string method.
@@ -520,11 +521,14 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
         struct hlist_node *n;
         u64 total = 0;
 
-        spin_lock_irq(&blkcg->lock);
-        hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
+                spin_lock_irq(blkg->q->queue_lock);
                 if (blkcg_policy_enabled(blkg->q, pol))
                         total += prfill(sf, blkg->pd[pol->plid], data);
-        spin_unlock_irq(&blkcg->lock);
+                spin_unlock_irq(blkg->q->queue_lock);
+        }
+        rcu_read_unlock();
 
         if (show_total)
                 seq_printf(sf, "Total %llu\n", (unsigned long long)total);