Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v4 1/4] sysctl: Add register_sysctl_init() interface
To:     Luis Chamberlain <mcgrof@kernel.org>
CC:     <keescook@chromium.org>, <yzaikin@google.com>,
        <adobriyan@gmail.com>, <mingo@kernel.org>,
        <gpiccoli@canonical.com>, <rdna@fb.com>, <patrick.bellasi@arm.com>,
        <sfr@canb.auug.org.au>, <akpm@linux-foundation.org>,
        <mhocko@suse.com>, <penguin-kernel@i-love.sakura.ne.jp>,
        <vbabka@suse.cz>, <tglx@linutronix.de>, <peterz@infradead.org>,
        <Jisheng.Zhang@synaptics.com>, <khlebnikov@yandex-team.ru>,
        <bigeasy@linutronix.de>, <pmladek@suse.com>,
        <linux-kernel@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
        <wangle6@huawei.com>, <alex.huangjianhui@huawei.com>
References: <1589859071-25898-1-git-send-email-nixiaoming@huawei.com>
 <1589859071-25898-2-git-send-email-nixiaoming@huawei.com>
 <20200529070903.GV11244@42.do-not-panic.com>
 <3d2d4b2e-db9e-aa91-dd29-e15d24028964@huawei.com>
 <20200529073646.GW11244@42.do-not-panic.com>
From:   Xiaoming Ni <nixiaoming@huawei.com>
Message-ID: <abdab2be-91e2-5f9b-bf49-abc387072a31@huawei.com>
Date:   Fri, 29 May 2020 16:33:01 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101
 Thunderbird/68.1.2
MIME-Version: 1.0
In-Reply-To: <20200529073646.GW11244@42.do-not-panic.com>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2020/5/29 15:36, Luis Chamberlain wrote:
> On Fri, May 29, 2020 at 03:27:22PM +0800, Xiaoming Ni wrote:
>> 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?
> 
> Sure, include/net/mac80211.h is a good example.
> 
>>>> +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
> 
> No rush :)
> 
>>>> +	}
>>>> +	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 ()?
> 
> I'm asking that the way you are adding it, you don't run
> kmemleak_not_leak(hdr) if the hdr allocation filed. If that is
> right then it seems that sysctl_init() might not be doing it
> right.
> 
> Can that code be shared somehow?
> 
>    Luis

void __ref kmemleak_not_leak(const void *ptr)
{
	pr_debug("%s(0x%p)\n", __func__, ptr);

	if (kmemleak_enabled && ptr && !IS_ERR(ptr))
		make_gray_object((unsigned long)ptr);
}
EXPORT_SYMBOL(kmemleak_not_leak);

In the code of kmemleak_not_leak(), it is verified that the pointer is 
valid, so kmemleak_not_leak (NULL) will not be a problem.
At the same time, there is no need to call kmemleak_not_leak() in the 
failed branch of register_sysctl_init().

Thanks
Xiaoming Ni