Messages in this thread | | | From | Coiby Xu <> | Date | Tue, 29 Jun 2021 21:35:41 +0800 | Subject | Re: [RFC 16/19] staging: qlge: remove deadcode in qlge_build_rx_skb |
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On Mon, Jun 28, 2021 at 09:46:45AM +0300, Dan Carpenter wrote: >On Sun, Jun 27, 2021 at 06:53:49PM +0800, Coiby Xu wrote: >> On Thu, Jun 24, 2021 at 03:49:26PM +0300, Dan Carpenter wrote: >> > On Thu, Jun 24, 2021 at 07:25:00PM +0800, Coiby Xu wrote: >> > > On Tue, Jun 22, 2021 at 10:29:39AM +0300, Dan Carpenter wrote: >> > > > On Mon, Jun 21, 2021 at 09:48:59PM +0800, Coiby Xu wrote: >> > > > > This part of code is for the case that "the headers and data are in >> > > > > a single large buffer". However, qlge_process_mac_split_rx_intr is for >> > > > > handling packets that packets underwent head splitting. In reality, with >> > > > > jumbo frame enabled, the part of code couldn't be reached regardless of >> > > > > the packet size when ping the NIC. >> > > > > >> > > > >> > > > This commit message is a bit confusing. We're just deleting the else >> > > > statement. Once I knew that then it was easy enough to review >> > > > qlge_process_mac_rx_intr() and see that if if >> > > > ib_mac_rsp->flags3 & IB_MAC_IOCB_RSP_DL is set then >> > > > ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HV must be set. >> > > >> > > Do you suggest moving to upper if, i.e. >> > > >> > > } else if (ib_mac_rsp->flags3 & IB_MAC_IOCB_RSP_DL && ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HS) { >> > > >> > > and then deleting the else statement? >> > > >> > >> > I have a rule that when people whinge about commit messages they should >> > write a better one themselves, but I have violated my own rule. Sorry. >> > Here is my suggestion: >> > >> > If the "ib_mac_rsp->flags3 & IB_MAC_IOCB_RSP_DL" condition is true >> > then we know that "ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HS" must be >> > true as well. Thus, we can remove that condition and delete the >> > else statement which is dead code. >> > >> > (Originally this code was for the case that "the headers and data are >> > in a single large buffer". However, qlge_process_mac_split_rx_intr >> > is for handling packets that packets underwent head splitting). >> >> Thanks for sharing your commit message! Now I see what you mean. But I'm >> not sure if "ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HS" is true when >> "ib_mac_rsp->flags3 & IB_MAC_IOCB_RSP_DL" is true. > >Well... It is true. qlge_process_mac_split_rx_intr() is only called >when "->flags4 & IB_MAC_IOCB_RSP_HS" is true or when >"->flags3 & IB_MAC_IOCB_RSP_DL" is false.
Actually qlge_process_mac_rx_intr calls qlge_process_mac_split_rx_intr when "ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HV" is true or in the last else,
/* Process an inbound completion from an rx ring. */ static unsigned long qlge_process_mac_rx_intr(struct qlge_adapter *qdev, struct rx_ring *rx_ring, struct qlge_ib_mac_iocb_rsp *ib_mac_rsp) { ... if (ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HV) { /* The data and headers are split into * separate buffers. */ qlge_process_mac_split_rx_intr(qdev, rx_ring, ib_mac_rsp, vlan_id); } else if (ib_mac_rsp->flags3 & IB_MAC_IOCB_RSP_DS) { ... } else { /* Non-TCP/UDP large frames that span multiple buffers * can be processed corrrectly by the split frame logic. */ qlge_process_mac_split_rx_intr(qdev, rx_ring, ib_mac_rsp, vlan_id); }
So I think we can't say that if "ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HV" is true, then "ib_mac_rsp->flags4 & IB_MAC_IOCB_RSP_HS" must be true. And I don't know how to reach the conclusion that the last else means "->flags3 & IB_MAC_IOCB_RSP_DL" is false.
> >To me the fact that it's clearly dead code, helps me to verify that the >patch doesn't change behavior. Anyway, "this part of code" was a bit >vague and it took me a while to figure out the patch deletes the else >statement. > >regards, >dan carpenter >
-- Best regards, Coiby
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