On Sun, 30 Jun 2019 20:23:48 +0300
Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> wrote:
> +static int cpsw_ndev_create_xdp_rxq(struct cpsw_priv *priv, int ch)
> +{
> + struct cpsw_common *cpsw = priv->cpsw;
> + int ret, new_pool = false;
> + struct xdp_rxq_info *rxq;
> +
> + rxq = &priv->xdp_rxq[ch];
> +
> + ret = xdp_rxq_info_reg(rxq, priv->ndev, ch);
> + if (ret)
> + return ret;
> +
> + if (!cpsw->page_pool[ch]) {
> + ret = cpsw_create_rx_pool(cpsw, ch);
> + if (ret)
> + goto err_rxq;
> +
> + new_pool = true;
> + }
> +
> + ret = xdp_rxq_info_reg_mem_model(rxq, MEM_TYPE_PAGE_POOL,
> + cpsw->page_pool[ch]);
> + if (!ret)
> + return 0;
> +
> + if (new_pool) {
> + page_pool_free(cpsw->page_pool[ch]);
> + cpsw->page_pool[ch] = NULL;
> + }
> +
> +err_rxq:
> + xdp_rxq_info_unreg(rxq);
> + return ret;
> +}
Looking at this, and Ilias'es XDP-netsec error handling path, it might
be a mistake that I removed page_pool_destroy() and instead put the
responsibility on xdp_rxq_info_unreg().
As here, we have to detect if page_pool_create() was a success, and then
if xdp_rxq_info_reg_mem_model() was a failure, explicitly call
page_pool_free() because the xdp_rxq_info_unreg() call cannot "free"
the page_pool object given it was not registered.
Ivan's patch in[1], might be a better approach, which forced all
drivers to explicitly call page_pool_free(), even-though it just
dec-refcnt and the real call to page_pool_free() happened via
xdp_rxq_info_unreg().
To better handle error path, I would re-introduce page_pool_destroy(),
as a driver API, that would gracefully handle NULL-pointer case, and
then call page_pool_free() with the atomic_dec_and_test(). (It should
hopefully simplify the error handling code a bit)
[1] https://lore.kernel.org/netdev/20190625175948.24771-2-ivan.khoronzhuk@xxxxxxxxxx/
> +void cpsw_ndev_destroy_xdp_rxqs(struct cpsw_priv *priv)
> +{
> + struct cpsw_common *cpsw = priv->cpsw;
> + struct xdp_rxq_info *rxq;
> + int i;
> +
> + for (i = 0; i < cpsw->rx_ch_num; i++) {
> + rxq = &priv->xdp_rxq[i];
> + if (xdp_rxq_info_is_reg(rxq))
> + xdp_rxq_info_unreg(rxq);
> + }
> +}
Are you sure you need to test xdp_rxq_info_is_reg() here?
You should just call xdp_rxq_info_unreg(rxq), if you know that this rxq
should be registered. If your assumption failed, you will get a
WARNing, and discover your driver level bug. This is one of the ways
the API is designed to "detect" misuse of the API. (I found this
rather useful, when I converted the approx 12 drivers using this
xdp_rxq_info API).
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
