blockdev: open images with BDRV_O_INCOMING on incoming live migration

Open images with BDRV_O_INCOMING in order to inform block drivers
that an incoming live migration is coming.
Signed-off-by: NBenoit Canet <benoit.canet@gmail.com>
Reviewed-by: NStefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

blockdev.c

@@ -595,6 +595,10 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
         bdrv_flags |= BDRV_O_COPY_ON_READ;
     }
 
+    if (runstate_check(RUN_STATE_INMIGRATE)) {
+        bdrv_flags |= BDRV_O_INCOMING;
+    }
+
     if (media == MEDIA_CDROM) {
         /* CDROM is fine for any interface, don't check.  */
         ro = 1;