mirror: block all operations on the target image during the job

There's nothing preventing the target image from being used by other
operations during the 'drive-mirror' job, so we should block them all
until the job is done.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 82b88fd04cde918a08a6f9a4ab85626d7fd7b502.1446475331.git.berto@igalia.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block/mirror.c b/block/mirror.c
index b1252a1..60f1cb5 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -384,6 +384,7 @@
         aio_context_release(replace_aio_context);
     }
     g_free(s->replaces);
+    bdrv_op_unblock_all(s->target, s->common.blocker);
     bdrv_unref(s->target);
     block_job_completed(&s->common, data->ret);
     g_free(data);
@@ -744,6 +745,9 @@
         block_job_release(bs);
         return;
     }
+
+    bdrv_op_block_all(s->target, s->common.blocker);
+
     bdrv_set_enable_write_cache(s->target, true);
     if (s->target->blk) {
         blk_set_on_error(s->target->blk, on_target_error, on_target_error);