linux-kernel - Re: [PATCH v4 1/4] sysctl: Add register_sysctl

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Date:   Fri, 29 May 2020 15:27:22 +0800
From:   Xiaoming Ni <nixiaoming@...wei.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
CC:     <keescook@...omium.org>, <yzaikin@...gle.com>,
        <adobriyan@...il.com>, <mingo@...nel.org>,
        <gpiccoli@...onical.com>, <rdna@...com>, <patrick.bellasi@....com>,
        <sfr@...b.auug.org.au>, <akpm@...ux-foundation.org>,
        <mhocko@...e.com>, <penguin-kernel@...ove.sakura.ne.jp>,
        <vbabka@...e.cz>, <tglx@...utronix.de>, <peterz@...radead.org>,
        <Jisheng.Zhang@...aptics.com>, <khlebnikov@...dex-team.ru>,
        <bigeasy@...utronix.de>, <pmladek@...e.com>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <wangle6@...wei.com>, <alex.huangjianhui@...wei.com>
Subject: Re: [PATCH v4 1/4] sysctl: Add register_sysctl_init() interface

On 2020/5/29 15:09, Luis Chamberlain wrote:
> On Tue, May 19, 2020 at 11:31:08AM +0800, Xiaoming Ni wrote:
>> --- a/kernel/sysctl.c
>> +++ b/kernel/sysctl.c
>> @@ -3358,6 +3358,25 @@ int __init sysctl_init(void)
>>   	kmemleak_not_leak(hdr);
>>   	return 0;
>>   }
>> +
>> +/*
>> + * The sysctl interface is used to modify the interface value,
>> + * but the feature interface has default values. Even if register_sysctl fails,
>> + * the feature body function can also run. At the same time, malloc small
>> + * fragment of memory during the system initialization phase, almost does
>> + * not fail. Therefore, the function return is designed as void
>> + */
> 
> Let's use kdoc while at it. Can you convert this to proper kdoc?
> 
Sorry, I do n’t know the format requirements of Kdoc, can you give me 
some tips for writing?


>> +void __init register_sysctl_init(const char *path, struct ctl_table *table,
>> +				 const char *table_name)
>> +{
>> +	struct ctl_table_header *hdr = register_sysctl(path, table);
>> +
>> +	if (unlikely(!hdr)) {
>> +		pr_err("failed when register_sysctl %s to %s\n", table_name, path);
>> +		return;
> 
> table_name is only used for this, however we can easily just make
> another _register_sysctl_init() helper first, and then use a macro
> which will concatenate this to something useful if you want to print
> a string. I see no point in the description for this, specially since
> the way it was used was not to be descriptive, but instead just a name
> followed by some underscore and something else.
> 
Good idea, I will fix and send the patch to you as soon as possible

>> +	}
>> +	kmemleak_not_leak(hdr);
> 
> Is it *wrong* to run kmemleak_not_leak() when hdr was not allocated?
> If so, can you fix the sysctl __init call itself?
I don't understand here, do you mean that register_sysctl_init () does 
not need to call kmemleak_not_leak (hdr), or does it mean to add check 
hdr before calling kmemleak_not_leak (hdr) in sysctl_init ()?


> PS. Since you have given me your series, feel free to send me a patch
> as a follow up to this in privae and I can integrate it into my tree.
> 
>    Luis
> 

Thanks
Xiaoming Ni