linux-kernel - Re: [RFC PATCH 1/3] proc/meminfo: introduce extra meminfo

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Message-ID: <20200311061836.GA83589@google.com>
Date:   Wed, 11 Mar 2020 15:18:36 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Jaewon Kim <jaewon31.kim@...sung.com>
Cc:     adobriyan@...il.com, akpm@...ux-foundation.org, labbott@...hat.com,
        sumit.semwal@...aro.org, minchan@...nel.org, ngupta@...are.org,
        sergey.senozhatsky.work@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, jaewon31.kim@...il.com
Subject: Re: [RFC PATCH 1/3] proc/meminfo: introduce extra meminfo

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'?

[..]

> +	spin_lock(&meminfo_lock);

Does this need to be a spinlock?

	-ss