block: prepare bdrv_reopen_multiple to release AioContext

After the next patch bdrv_drain_all will have to be called without holding any
AioContext.  Prepare to do this by adding an AioContext argument to
bdrv_reopen_multiple.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1477565348-5458-15-git-send-email-pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
diff --git a/block.c b/block.c
index 7f3e7bc..fbe485c 100644
--- a/block.c
+++ b/block.c
@@ -2082,7 +2082,7 @@
  * to all devices.
  *
  */
-int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
+int bdrv_reopen_multiple(AioContext *ctx, BlockReopenQueue *bs_queue, Error **errp)
 {
     int ret = -1;
     BlockReopenQueueEntry *bs_entry, *next;
@@ -2131,7 +2131,7 @@
     Error *local_err = NULL;
     BlockReopenQueue *queue = bdrv_reopen_queue(NULL, bs, NULL, bdrv_flags);
 
-    ret = bdrv_reopen_multiple(queue, &local_err);
+    ret = bdrv_reopen_multiple(bdrv_get_aio_context(bs), queue, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
     }