blkdev: check for valid request queue before issuing flush

[pandora-kernel.git] / block / blk-barrier.c

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index eefbde8..557f693 100644 (file)
--- 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;