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-rw-r--r--block/blk-cgroup.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b9f4cc4..28d227c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -872,6 +872,13 @@ void blkcg_drain_queue(struct request_queue *q)
{
lockdep_assert_held(q->queue_lock);
+ /*
+ * @q could be exiting and already have destroyed all blkgs as
+ * indicated by NULL root_blkg. If so, don't confuse policies.
+ */
+ if (!q->root_blkg)
+ return;
+
blk_throtl_drain(q);
}
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