From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH v5 net-next 6/6] net: ethernet: ti: cpsw: add XDP support Date: Mon, 1 Jul 2019 18:19:01 +0200 Message-ID: <20190701181901.150c0b71@carbon> References: <20190630172348.5692-1-ivan.khoronzhuk@linaro.org> <20190630172348.5692-7-ivan.khoronzhuk@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190630172348.5692-7-ivan.khoronzhuk@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: Ivan Khoronzhuk Cc: grygorii.strashko@ti.com, davem@davemloft.net, ast@kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, ilias.apalodimas@linaro.org, netdev@vger.kernel.org, daniel@iogearbox.net, jakub.kicinski@netronome.com, john.fastabend@gmail.com, brouer@redhat.com List-Id: linux-omap@vger.kernel.org On Sun, 30 Jun 2019 20:23:48 +0300 Ivan Khoronzhuk 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@linaro.org/ > +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