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Subject: Re: [RFC PATCH 1/3] proc/meminfo: introduce extra meminfo
To:     Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc:     adobriyan@gmail.com, akpm@linux-foundation.org, labbott@redhat.com,
        sumit.semwal@linaro.org, minchan@kernel.org, ngupta@vflare.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        jaewon31.kim@gmail.com
From:   Jaewon Kim <jaewon31.kim@samsung.com>
Message-ID: <5E68859A.9050107@samsung.com>
Date:   Wed, 11 Mar 2020 15:30:50 +0900
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On 2020년 03월 11일 15:25, Sergey Senozhatsky wrote:
> On (20/03/11 15:18), Sergey Senozhatsky wrote:
>> On (20/03/11 12:44), Jaewon Kim wrote:
>> [..]
>>> +#define NAME_SIZE      15
>>> +#define NAME_BUF_SIZE  (NAME_SIZE + 2) /* ':' and '\0' */
>>> +
>>> +struct extra_meminfo {
>>> +	struct list_head list;
>>> +	atomic_long_t *val;
>>> +	int shift_for_page;
>>> +	char name[NAME_BUF_SIZE];
>>> +	char name_pad[NAME_BUF_SIZE];
>>> +};
>>> +
>>> +int register_extra_meminfo(atomic_long_t *val, int shift, const char *name)
>>> +{
>>> +	struct extra_meminfo *meminfo, *memtemp;
>>> +	int len;
>>> +	int error = 0;
>>> +
>>> +	meminfo = kzalloc(sizeof(*meminfo), GFP_KERNEL);
>>> +	if (!meminfo) {
>>> +		error = -ENOMEM;
>>> +		goto out;
>>> +	}
>>> +
>>> +	meminfo->val = val;
>>> +	meminfo->shift_for_page = shift;
>>> +	strncpy(meminfo->name, name, NAME_SIZE);
>>> +	len = strlen(meminfo->name);
>>> +	meminfo->name[len] = ':';
>>> +	strncpy(meminfo->name_pad, meminfo->name, NAME_BUF_SIZE);
>> What happens if there is no NULL byte among the first NAME_SIZE bytes
>> of passed `name'?
> Ah. The buffer size is NAME_BUF_SIZE, so should be fine.
>
> 	-ss
Hello yes correct.

For your comment of 'spinlock', it may be changed to other lock like rw semaphore.
I think there are just couple of writers compared to many readers.
Thank you for your comment.
>
>