xen/blkback: Get the 'requeust_queue' properly.

After the commit 0faa8cca883bbc6a0919e3c89128672659b75820
("    xen/blkback: remove per-queue plugging") we forgot
to retrieve the 'struct request_queue' from the block device.

This puts the functionality back in and fixes a NULL pointer
bug.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index a0d3227955c96c2b8a8b013db98680b4d51cd9eb..3751325bfc32681e399b9d86e17bf83bfd348640 100644 (file)
--- a/drivers/xen/blkback/blkback.c
+++ b/drivers/xen/blkback/blkback.c
@@ -542,6 +542,9 @@ static void dispatch_rw_block_io(struct blkif_st *blkif,
                        goto fail_response;
                }
        }
+       q = bdev_get_queue(preq.bdev);
+       if (!q)
+               goto fail_response;
        /* If we have failed at this point, we need to undo the M2P override,
         * set gnttab_set_unmap_op on all of the grant references and perform
         * the hypercall to unmap the grants - that is all done in