1 files changed, 9 insertions, 0 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index eefbde835308..557f69360b6a 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -310,6 +310,15 @@ int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
         if (!q)
                 return -ENXIO;
 
+        /*
+         * some block devices may not have their queue correctly set up here
+         * (e.g. loop device without a backing file) and so issuing a flush
+         * here will panic. Ensure there is a request function before issuing
+         * the barrier.
+         */
+        if (!q->make_request_fn)
+                return -ENXIO;
+
         bio = bio_alloc(gfp_mask, 0);
         bio->bi_end_io = bio_end_empty_barrier;
         bio->bi_bdev = bdev;