linux-kernel - Re: [PATCH 2/4] proc/sysctl: add shared variables -1

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Date:   Fri, 15 May 2020 17:06:28 +0800
From:   Xiaoming Ni <nixiaoming@...wei.com>
To:     Kees Cook <keescook@...omium.org>
CC:     <mcgrof@...nel.org>, <yzaikin@...gle.com>, <adobriyan@...il.com>,
        <mingo@...nel.org>, <peterz@...radead.org>,
        <akpm@...ux-foundation.org>, <yamada.masahiro@...ionext.com>,
        <bauerman@...ux.ibm.com>, <gregkh@...uxfoundation.org>,
        <skhan@...uxfoundation.org>, <dvyukov@...gle.com>,
        <svens@...ckframe.org>, <joel@...lfernandes.org>,
        <tglx@...utronix.de>, <Jisheng.Zhang@...aptics.com>,
        <pmladek@...e.com>, <bigeasy@...utronix.de>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <wangle6@...wei.com>
Subject: Re: [PATCH 2/4] proc/sysctl: add shared variables -1

On 2020/5/15 16:06, Kees Cook wrote:
> On Fri, May 15, 2020 at 12:33:42PM +0800, Xiaoming Ni wrote:
>> Add the shared variable SYSCTL_NEG_ONE to replace the variable neg_one
>> used in both sysctl_writes_strict and hung_task_warnings.
>>
>> Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
>> ---
>>   fs/proc/proc_sysctl.c     | 2 +-
>>   include/linux/sysctl.h    | 1 +
>>   kernel/hung_task_sysctl.c | 3 +--
>>   kernel/sysctl.c           | 3 +--
> 
> How about doing this refactoring in advance of the extraction patch?
Before  advance of the extraction patch, neg_one is only used in one 
file, does it seem to have no value for refactoring?


> 
>>   4 files changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
>> index b6f5d45..acae1fa 100644
>> --- a/fs/proc/proc_sysctl.c
>> +++ b/fs/proc/proc_sysctl.c
>> @@ -23,7 +23,7 @@
>>   static const struct inode_operations proc_sys_dir_operations;
>>   
>>   /* shared constants to be used in various sysctls */
>> -const int sysctl_vals[] = { 0, 1, INT_MAX };
>> +const int sysctl_vals[] = { 0, 1, INT_MAX, -1 };
>>   EXPORT_SYMBOL(sysctl_vals);
>>   
>>   /* Support for permanently empty directories */
>> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
>> index 02fa844..6d741d6 100644
>> --- a/include/linux/sysctl.h
>> +++ b/include/linux/sysctl.h
>> @@ -41,6 +41,7 @@
>>   #define SYSCTL_ZERO	((void *)&sysctl_vals[0])
>>   #define SYSCTL_ONE	((void *)&sysctl_vals[1])
>>   #define SYSCTL_INT_MAX	((void *)&sysctl_vals[2])
>> +#define SYSCTL_NEG_ONE	((void *)&sysctl_vals[3])
> 
> Nit: let's keep these value-ordered? i.e. -1, 0, 1, INT_MAX.
Thanks for guidance, your method is better

Thanks.
Xiaoming Ni