parallels: wrong call to bdrv_truncate

Parallels driver should not call bdrv_truncate if the image was opened
in the read-only mode. Without the patch
    qemu-img check harddisk.hds
asserts with
    bdrv_truncate: Assertion `child->perm & BLK_PERM_RESIZE' failed.

Parameters used on the write path are not needed if the image is opened
in the read-only mode.
Signed-off-by: NDenis V. Lunev <den@openvz.org>
Reported-by: NEdgar Kaziahmedov <edos@virtuozzo.mipt.ru>
Message-id: 1490625488-7980-1-git-send-email-den@openvz.org
CC: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/parallels.c

@@ -687,7 +687,8 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
     if (local_err != NULL) {
         goto fail_options;
     }
-    if (!bdrv_has_zero_init(bs->file->bs) ||
+
+    if (!(flags & BDRV_O_RESIZE) || !bdrv_has_zero_init(bs->file->bs) ||
             bdrv_truncate(bs->file, bdrv_getlength(bs->file->bs)) != 0) {
         s->prealloc_mode = PRL_PREALLOC_MODE_FALLOCATE;
     }