linux-kernel - Re: [PATCH] vmstat: don't auto expand the sysfs files

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Message-ID: <ZXdAOroKNce1r+TZ@casper.infradead.org>
Date:   Mon, 11 Dec 2023 17:00:42 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Pasha Tatashin <pasha.tatashin@...een.com>
Cc:     gregkh@...uxfoundation.org, rafael@...nel.org,
        akpm@...ux-foundation.org, surenb@...gle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        souravpanda@...gle.com
Subject: Re: [PATCH] vmstat: don't auto expand the sysfs files

On Mon, Dec 11, 2023 at 03:46:44PM +0000, Pasha Tatashin wrote:
> +++ b/drivers/base/node.c
> @@ -520,26 +520,34 @@ static ssize_t node_read_vmstat(struct device *dev,
>  	int i;
>  	int len = 0;
>  
> -	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
> -		len += sysfs_emit_at(buf, len, "%s %lu\n",
> -				     zone_stat_name(i),
> -				     sum_zone_node_page_state(nid, i));
> +	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
> +		if (vmstat_text[ZONE_STAT_NAME_IDX(i)].flags & VMSTAT_SHOW_SYSFS) {
> +			len += sysfs_emit_at(buf, len, "%s %lu\n",
> +					     zone_stat_name(i),
> +					     sum_zone_node_page_state(nid, i));
> +		}
> +	}

This seems overly complicated.  Why not do:

	for (i = 0; i < NR_VM_ZONE_STAT_SYSFS_ITEMS; i++)

and have assertions that this number doesn't change (and require people
to add to the list after that point)?