Re: [PATCH v3 3/3] mm/kmemleak: stop the per-cpu and struct page scans early too

[Oleg Nesterov <oleg@redhat.com>]

On 06/15, Breno Leitao wrote:
>
>  #ifdef CONFIG_SMP
>  	/* per-cpu sections scanning */
> -	for_each_possible_cpu(i)
> -		scan_large_block(__per_cpu_start + per_cpu_offset(i),
> -				 __per_cpu_end + per_cpu_offset(i));
> +	for_each_possible_cpu(i) {
> +		if (scan_large_block(__per_cpu_start + per_cpu_offset(i),
> +				     __per_cpu_end + per_cpu_offset(i)))
> +			break;
> +	}
>  #endif

The patch looks correct, but...

if scan_large_block() returns true, then

> @@ -1902,6 +1908,7 @@ static void kmemleak_scan(void)
>  		unsigned long start_pfn = zone->zone_start_pfn;
>  		unsigned long end_pfn = zone_end_pfn(zone);
>  		unsigned long pfn;
> +		int stop = 0;
>
>  		for (pfn = start_pfn; pfn < end_pfn; pfn++) {
>  			struct page *page = pfn_to_online_page(pfn);
> @@ -1918,8 +1925,12 @@ static void kmemleak_scan(void)
>  			/* only scan if page is in use */
>  			if (page_count(page) == 0)
>  				continue;
> -			scan_block(page, page + 1, NULL);
> +			stop = scan_block(page, page + 1, NULL);

it is pointless to enter this for_each_populated_zone() loop and call
kmemleak_scan_task_stacks() after that?

Not that I think this is bad, just a question...

Oleg.