linux-staging.lists.linux.dev archive mirror
 help / color / mirror / Atom feed
From: Coiby Xu <coiby.xu@gmail.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: linux-staging@lists.linux.dev, netdev@vger.kernel.org,
	Benjamin Poirier <benjamin.poirier@gmail.com>,
	Shung-Hsi Yu <shung-hsi.yu@suse.com>,
	Manish Chopra <manishc@marvell.com>,
	"supporter:QLOGIC QLGE 10Gb ETHERNET DRIVER"
	<GR-Linux-NIC-Dev@marvell.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [RFC 16/19] staging: qlge: remove deadcode in qlge_build_rx_skb
Date: Tue, 29 Jun 2021 21:35:41 +0800	[thread overview]
Message-ID: <20210629133541.2n3rr7vzglcoy56x@Rk> (raw)
In-Reply-To: <20210628064645.GK2040@kadam>

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

  reply	other threads:[~2021-06-29 13:37 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-21 13:48 [RFC 00/19] Improve the qlge driver based on drivers/staging/qlge/TODO Coiby Xu
2021-06-21 13:48 ` [RFC 01/19] staging: qlge: fix incorrect truesize accounting Coiby Xu
2021-06-21 14:10   ` Dan Carpenter
2021-06-22 11:36     ` Coiby Xu
2021-06-23  4:55       ` Benjamin Poirier
2021-06-24 11:47         ` Coiby Xu
2021-06-28  0:14           ` Coiby Xu
2021-06-21 13:48 ` [RFC 02/19] staging: qlge: change LARGE_BUFFER_MAX_SIZE to 4096 Coiby Xu
2021-06-21 13:48 ` [RFC 03/19] staging: qlge: alloc skb with only enough room for header when data is put in the fragments Coiby Xu
2021-06-21 13:48 ` [RFC 04/19] staging: qlge: add qlge_* prefix to avoid namespace clashes Coiby Xu
2021-06-22  7:55   ` Benjamin Poirier
2021-06-24 11:34     ` Coiby Xu
2021-06-21 13:48 ` [RFC 05/19] staging: qlge: rename rx to completion queue and seperate rx_ring from completion queue Coiby Xu
2021-06-21 13:48 ` [RFC 06/19] staging: qlge: disable flow control by default Coiby Xu
2021-06-22  7:49   ` Benjamin Poirier
2021-06-24 11:33     ` Coiby Xu
2021-06-21 13:48 ` [RFC 07/19] staging: qlge: remove the TODO item of unnecessary memset 0 Coiby Xu
2021-06-21 13:48 ` [RFC 08/19] staging: qlge: reorder members of qlge_adapter for optimization Coiby Xu
2021-06-21 13:48 ` [RFC 09/19] staging: qlge: remove the TODO item of reorder struct Coiby Xu
2021-06-21 13:48 ` [RFC 10/19] staging: qlge: remove the TODO item of avoid legacy/deprecated apis Coiby Xu
2021-06-21 13:48 ` [RFC 11/19] staging: qlge: the number of pages to contain a buffer queue is constant Coiby Xu
2021-06-21 13:48 ` [RFC 12/19] staging: qlge: rewrite do while loops as for loops in qlge_start_rx_ring Coiby Xu
2021-06-22  7:45   ` Benjamin Poirier
2021-06-24 11:56     ` Coiby Xu
2021-06-21 13:48 ` [RFC 13/19] staging: qlge: rewrite do while loop as for loop in qlge_sem_spinlock Coiby Xu
2021-06-22  7:20   ` Dan Carpenter
2021-06-24 11:22     ` Coiby Xu
2021-06-30 10:58       ` Joe Perches
2021-06-30 23:33         ` Coiby Xu
2021-07-01  4:35           ` Joe Perches
2021-07-02 23:56             ` Coiby Xu
2021-06-21 13:48 ` [RFC 14/19] staging: qlge: rewrite do while loop as for loop in qlge_refill_bq Coiby Xu
2021-06-21 13:48 ` [RFC 15/19] staging: qlge: remove the TODO item about rewriting while loops as simple for loops Coiby Xu
2021-06-21 13:48 ` [RFC 16/19] staging: qlge: remove deadcode in qlge_build_rx_skb Coiby Xu
2021-06-22  7:29   ` Dan Carpenter
2021-06-24 11:25     ` Coiby Xu
2021-06-24 12:49       ` Dan Carpenter
2021-06-27 10:53         ` Coiby Xu
2021-06-28  6:46           ` Dan Carpenter
2021-06-29 13:35             ` Coiby Xu [this message]
2021-06-29 14:22               ` Dan Carpenter
2021-06-30 23:19                 ` Coiby Xu
2021-06-21 13:49 ` [RFC 17/19] staging: qlge: fix weird line wrapping Coiby Xu
2021-06-22  8:46   ` Dan Carpenter
2021-06-24 11:55     ` Coiby Xu
2021-06-21 13:49 ` [RFC 18/19] staging: qlge: fix two indentation issues Coiby Xu
2021-06-21 13:49 ` [RFC 19/19] staging: qlge: remove TODO item of unnecessary runtime checks Coiby Xu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210629133541.2n3rr7vzglcoy56x@Rk \
    --to=coiby.xu@gmail.com \
    --cc=GR-Linux-NIC-Dev@marvell.com \
    --cc=benjamin.poirier@gmail.com \
    --cc=dan.carpenter@oracle.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-staging@lists.linux.dev \
    --cc=manishc@marvell.com \
    --cc=netdev@vger.kernel.org \
    --cc=shung-hsi.yu@suse.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).