Re: [PATCH] [SCSI] FlashPoint: optimize string comparison

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Le 07/07/2015 19:04, Khalid Aziz a écrit :
On 07/07/2015 02:45 AM, Frans Klaver wrote:
On Tue, Jul 7, 2015 at 7:39 AM, Christophe JAILLET
<christophe.jaillet@xxxxxxxxxx> wrote:
Stop comparing the strings as soon as we know that they don't match.

Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
  drivers/scsi/FlashPoint.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/FlashPoint.c b/drivers/scsi/FlashPoint.c
index 5c74e4c..24a4d1a 100644
--- a/drivers/scsi/FlashPoint.c
+++ b/drivers/scsi/FlashPoint.c
@@ -6280,8 +6280,10 @@ static unsigned char FPT_scmachid(unsigned char p_card,
                 match = 1;

                 for (k = 0; k < ID_STRING_LENGTH; k++) {
- if (p_id_string[k] != FPT_scamInfo[i].id_string[k]) + if (p_id_string[k] != FPT_scamInfo[i].id_string[k]) {
                                 match = 0;
+                               break;
+                       }
                 }

                 if (match) {

Why doesn't this use strncmp?

Thanks,
Frans


I suspect that is how this code came from Mylex many years ago. Using strncmp would indeed be a better way to clean this up. Also, further down in the same routine:

                if (FPT_scamInfo[match].state == ID_UNUSED) {
                        for (k = 0; k < ID_STRING_LENGTH; k++) {
                                FPT_scamInfo[match].id_string[k] =
                                    p_id_string[k];
                        }


This should use strncpy instead. There is another similar spot further down.

Christophe, if you can send a new patch with these clean-ups, that would be great.

Thanks,
Khalid

Hi,

I'm sorry but I won't propose a new patch for that.

I had the same reaction at first (why not use strncmp?) but it seems to be the way this driver is coded. Should we want to introduce strncmp here, then, as you have noticed, strcpy should be used to. memset could be also used in many places. Then looking elsewhere in the code, many things should, IMHO, also be fixed. (use consistently empty lines before/after code ; use consistently { }...)

Another concern to me is "the use of carriage return". In the following examples, things could be much more readable if not limited to 50 chars per line, or so.

1357  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L1357>                                  FPT_sccbMgrTbl  <http://lxr.free-electrons.com/ident?i=FPT_sccbMgrTbl>[thisCard][id  <http://lxr.free-electrons.com/ident?i=id>  * 2 +
1358  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L1358>                                                           i  <http://lxr.free-electrons.com/ident?i=i>].TarStatus |=
1359  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L1359>                                      SYNC_SUPPORTED  <http://lxr.free-electrons.com/ident?i=SYNC_SUPPORTED>;

or

4850  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4850>                                                  FPT_sccbMgrTbl  <http://lxr.free-electrons.com/ident?i=FPT_sccbMgrTbl>[p_card]
4851  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4851>                                                      [currSCCB->TargID].
4852  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4852>                                                      TarLUNBusy[0] = 1;
4853  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4853>                                                  if (currSCCB->Sccb_tag) {
4854  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4854>                                                          if (FPT_BL_Card  <http://lxr.free-electrons.com/ident?i=FPT_BL_Card>[p_card].
4855  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4855>                                                              discQCount != 0)
4856  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4856>                                                                  FPT_BL_Card  <http://lxr.free-electrons.com/ident?i=FPT_BL_Card>
4857  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4857>                                                                      [p_card].
4858  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4858>                                                                      discQCount--;
4859  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4859>                                                          FPT_BL_Card  <http://lxr.free-electrons.com/ident?i=FPT_BL_Card>[p_card].
4860  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4860>                                                              discQ_Tbl[currSCCB->
4861  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4861>                                                                        Sccb_tag]
4862  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4862>                                                              =NULL  <http://lxr.free-electrons.com/ident?i=NULL>;
4863  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4863>                                                  } else {
4864  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4864>                                                          if (FPT_BL_Card  <http://lxr.free-electrons.com/ident?i=FPT_BL_Card>[p_card].
4865  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4865>                                                              discQCount != 0)
4866  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4866>                                                                  FPT_BL_Card  <http://lxr.free-electrons.com/ident?i=FPT_BL_Card>
4867  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4867>                                                                      [p_card].
4868  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4868>                                                                      discQCount--;
4869  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4869>                                                          FPT_BL_Card  <http://lxr.free-electrons.com/ident?i=FPT_BL_Card>[p_card].
4870  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4870>                                                              discQ_Tbl
4871  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4871>                                                              [FPT_sccbMgrTbl  <http://lxr.free-electrons.com/ident?i=FPT_sccbMgrTbl>
4872  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4872>                                                               [p_card][currSCCB->
4873  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4873>                                                                        TargID].
4874  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4874>                                                               LunDiscQ_Idx[0]] =
4875  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4875>                                                              NULL  <http://lxr.free-electrons.com/ident?i=NULL>;
4876  <http://lxr.free-electrons.com/source/drivers/scsi/FlashPoint.c#L4876>                                                  }


I only reported an easy fix based on a semi-automatic detection of code that could be improved. I don't want to make some much more heavy changes that could break the code.

Best regards,
CJ
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