pNFS: Wait on outstanding layoutreturns to complete in pnfs_roc()

	if (!nfs_have_layout(ino))

		return false;

retry:

	spin_lock(&ino->i_lock);

	lo = nfsi->layout;

	if (!lo || !pnfs_layout_is_valid(lo) ||

	    test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags))

		goto out_noroc;

	if (test_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags)) {

		pnfs_get_layout_hdr(lo);

		spin_unlock(&ino->i_lock);

		wait_on_bit(&lo->plh_flags, NFS_LAYOUT_RETURN,

				TASK_UNINTERRUPTIBLE);

		pnfs_put_layout_hdr(lo);

		goto retry;

	}

	/* no roc if we hold a delegation */

	if (nfs4_check_delegation(ino, FMODE_READ))