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-rw-r--r--block/blk-barrier.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index eefbde83530..557f69360b6 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;