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dmarc=pass (p=quarantine dis=none) header.from=huawei.com Subject: Re: [Intel-wired-lan] [PATCH net] igc: Fix passing 0 to ERR_PTR in igc_xdp_run_prog() X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" On 2024/10/17 7:12, Jacob Keller wrote: > > > On 10/16/2024 4:06 PM, Jacob Keller wrote: >> >> >> On 10/16/2024 11:53 AM, Simon Horman wrote: >>> On Wed, Oct 16, 2024 at 06:53:10PM +0800, Yue Haibing wrote: >>>> Return NULL instead of passing to ERR_PTR while res is IGC_XDP_PASS, >>>> which is zero, this fix smatch warnings: >>>> drivers/net/ethernet/intel/igc/igc_main.c:2533 >>>> igc_xdp_run_prog() warn: passing zero to 'ERR_PTR' >>>> >>>> Fixes: 26575105d6ed ("igc: Add initial XDP support") >>>> Signed-off-by: Yue Haibing >>>> --- >>>> drivers/net/ethernet/intel/igc/igc_main.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c >>>> index 6e70bca15db1..c3d6e20c0be0 100644 >>>> --- a/drivers/net/ethernet/intel/igc/igc_main.c >>>> +++ b/drivers/net/ethernet/intel/igc/igc_main.c >>>> @@ -2530,7 +2530,7 @@ static struct sk_buff *igc_xdp_run_prog(struct igc_adapter *adapter, >>>> res = __igc_xdp_run_prog(adapter, prog, xdp); >>>> >>>> out: >>>> - return ERR_PTR(-res); >>>> + return res ? ERR_PTR(-res) : NULL; >>> >>> I think this is what PTR_ERR_OR_ZERO() is for. >> >> Not quite. PTR_ERR_OR_ZERO is intended for the case where you are >> extracting an error from a pointer. This is converting an error into a >> pointer. >> >> I am not sure what is really expected here. If res is zero, shouldn't we >> be returning an skb pointer and not NULL? >> >> Why does igc_xdp_run_prog even return a sk_buff pointer at all? It never >> actually returns an skb... >> >> This feels like the wrong fix entirely. >> >> __igc_xdp_run_prog returns a custom value for the action, between >> IGC_XDP_PASS, IGC_XDP_TX, IGC_XDP_REDIRECT, or IGC_XDP_CONSUMED. >> >> This function is called by igc_xdp_run_prog which converts this to a >> negative error code with the sk_buff pointer type. >> >> All so that we can assign a value to the skb pointer in >> ice_clean_rx_irq, and check it with IS_ERR >> >> I don't like this fix, I think we could drop the igc_xdp_run_prog >> wrapper, call __igc_xdp_run_prog directly and check its return value >> instead of this method of using an error pointer. > > Indeed, this SKB error stuff was added by 26575105d6ed ("igc: Add > initial XDP support") which claims to be aligning with other Intel drivers. > > But the other Intel drivers just have a function that returns the xdp > result and checks it directly. >Thanks for review，maybe can fix this as commit 12738ac4754e ("i40e: Fix sparse errors in i40e_txrx.c")? > Perhaps this is due to the way that the igc driver shares rings between > XDP and the regular path? > > Its not clear to me, but I think this fix is not what I would do. > > .