[Qemu-block] bdrv_replace_child crashes

[Vladimir Sementsov-Ogievskiy]

Hi Kevin!

In commit 33a610c3986 "block: Involve block drivers in permission 
granting" you write:
     if (old_bs) {
         /* Update permissions for old node. This is guaranteed to succeed
          * because we're just taking a parent away, so we're loosening
          * restrictions. */
         bdrv_get_cumulative_perm(old_bs, &perm, &shared_perm);
         bdrv_check_perm(old_bs, NULL, perm, shared_perm, NULL, 
&error_abort);
         bdrv_set_perm(old_bs, perm, shared_perm);
     }

we have some crashes on this error_abort, because F_SETLK or F_OFD_SETLK 
return an error on NFS (for example when remote server not responding).

What to do with this? Is it safe just to ignore the error here, at least 
in case of bdrv_detach_child?

-- 
Best regards,
Vladimir