Date:	Fri, 23 Nov 2012 11:35:36 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Shan Wei <shanwei88@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
CC:	netdev <netdev@...r.kernel.org>
Subject: Fwd: Re: [PATCH] net: ipv6: change %8s to %s for rt->dst.dev->name
 in seq_printf of rt6_info_route


1) about the proof:
 currently, sorry for I can not find the device which name length is more than 8.
 maybe they (Asianux user) use system call in user mode to assign the new name to device.
   please reference: dev_ioctl -> dev_ifsioc -> dev_change_name  in net/core/dev.c.
   I do not know why they want to change the net device name (but they surely can do).

2) about %*s:
 since kernel is an open system, IFNAMSIZ is belong to OS API level for outside
   it has effect both on individual kernel modules and user mode system call
   we need obey this rule, and %8s is not match this rule.
   so %8s is not suitable. (and now we have to choose %16s or %s).

 for the format of information which seq_printf output:
   it is not belong to OS API level for outside (at least, for current case, it is true). 
   so we need not keep 'compatible' of it, so %16s is not necessary.

 for keeping source code simple and clearly:
   %s is better than %16s.

 so for result, we should choose %s only (neither %16s nor %8s).

3) about my original mail:
 why did my original mail (first mail relative with this patch) say %16s ?
 my goals are:
   i)   to confirm whether suitable to communicate about RHEL* in *@...r.kernel.org.
   ii)  to confirm whether *@...r.kernel.org welcome such a minor patch (at least, it is not a spam).
   iii) to confirm whether *@...r.kernel.org are focused on coding. 
        (so I intended to use %16s and 'beautiful')
        (I have seen too many another various organizations to not be focused on coding)
 after get feed back from Eric Dumazet.
   i)   it is not suitable to communicate about RHEL* in *@...r.kernel.org.
   ii)  *@...r.kernel.org welcome such a minor patch.
   iii) *@...r.kernel.org are focused on coding.
        (so I am sure that can use "coding review" to provide contributes to *@...r.kernel.org)


 Regards

gchen.

-------- 原始消息 --------
主题: Re: [PATCH] net: ipv6: change %8s to %s for rt->dst.dev->name in seq_printf of rt6_info_route
日期: Thu, 22 Nov 2012 16:37:27 +0800
发件人: Chen Gang <gang.chen@...anux.com>
收件人: Shan Wei <shanwei88@...il.com>
抄送: Eric Dumazet <eric.dumazet@...il.com>,  David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>

于 2012年11月22日 13:28, Shan Wei 写道:
> Hi chen gang:
> 
> For length of device name which less than 8 char，
> your patch changes them to be print from align right 
> to align left. But at least since 2005(git age-time),
> we keep this style so far.
> Maybe, since birth of this code, just align right. :-)
> 

  originally, it is a solid output length, the length is "#define
RT6_INFO_LEN (32 + 4 + 32 + 4 + 32 + 40 + 5 + 1)"
  and RHEL5 (kernel-2.6.18-308.20.el5) still use it.
  it assume that the length of rt->rt6i_dev->name (in RHEL5) is 8.

> Why we *should* change this style?
> just keep be consistent with the case which length of device
> name greater than 8 char?
> 

  as a solid length, 8 is not suitable, firstly I suggest to '%16s' (I
call it 'beautiful',  but for RHEL5, it is a correctness issue)
  and Eric Dumazet suggest use '%s' is better, since it is not solid
length any more (have already let seq_printf instead of arg->buffer)
  and I think: as a result, what he said is reasonable

> Not only old name rule i.e. eth0,eth1, but also new name rule
> base on pci address ,i.e. em1,p3p1. most of them are less than 8 char.
> Should not we take more attention on the case less than 8 char?
> 

  I have ever seen such a device name is more than 8 characters.
  I am not quite sure: maybe they are eth-route* or eth-usb* ...
  I will check it in these days, please wait for some days.


> By addition, if we want to add new field in the future,
> align right is a better choice.
> 

  maybe what you said is better (still keep it 'beautiful', but need use
'%16s' instead of '%8s')

  for this, Eric Dumazet maybe have his opinions.


 Regards

gchen.

> 
> Chen Gang said, at 2012/11/22 10:52:
>> Hi Shan Wei, Eric Dumazet
>>
>>   is this patch integrated into main branch ?
>>   if need me for additional completion (such as: merge another 2 trivial patches into this patch, too)
>>   please tell me, I will do. 
>>
>>   I understand you are working overtime, maybe no time for any minor and trivial patches.
>>   if surely it is, I think:
>>     you can modify these code manually, and obsolete these minor and trivial patches which I provided.
>>     I do not mind whether mention me in another new patches (you can mention me or not mention me, both are OK).
>>     since our goal is to provide contributes to outside, efficiently.
>>
>>  regards
>>
>> gchen
>>
>>
>> 于 2012年11月05日 11:02, Chen Gang 写道:
>>>
>>> 1. not to send same patch triple times. 
>>
>>   thanks, I shall notice, next time.
>>   (I shall 'believe' another members).
>>
>>> 2. config your email client,because tab is changed to space.
>>>    you can read Documentation/email-clients.txt.
>>
>>   1) thanks. I shall notice, next time.
>>   2) now, I get gvim as extention editor for thounderbird
>>   3) the patch is generated by `git format-patch -s --summary --stat`
>>      it use "' '\t" as head, I do not touch it, maybe it is correct.
>>
>> welcome any members to giving additional suggestions and completions.
>>
>> thanks
>>
>> the modified contents are below,
>> -----------------------------------------------------------------------------------
>>
>>   the length of rt->dst.dev->name is 16 (IFNAMSIZ)
>>   in seq_printf, it is not suitable to use %8s for rt->dst.dev->name.
>>   so change it to %s, since each line has not been solid any more.
>>
>>   additional information:
>>
>>     %8s  limit the width, not for the original string output length
>>          if name length is more than 8, it still can be fully displayed.
>>          if name length is less than 8, the ' ' will be filled before name.
>>
>>     %.8s truly limit the original string output length (precision)
>>
>> Signed-off-by: Chen Gang <gang.chen@...anux.com>
>> ---
>>  net/ipv6/route.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index c42650c..b60bc52 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -2835,7 +2835,7 @@ static int rt6_info_route(struct rt6_info *rt, void *p_arg)
>>  	} else {
>>  		seq_puts(m, "00000000000000000000000000000000");
>>  	}
>> -	seq_printf(m, " %08x %08x %08x %08x %8s\n",
>> +	seq_printf(m, " %08x %08x %08x %08x %s\n",
>>  		   rt->rt6i_metric, atomic_read(&rt->dst.__refcnt),
>>  		   rt->dst.__use, rt->rt6i_flags,
>>  		   rt->dst.dev ? rt->dst.dev->name : "");
>>
>>
>>
> 
> 
> 


-- 
Chen Gang

Asianux Corporation


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