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>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index a0d3227955c9..3751325bfc32 100644
--- 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