linux-kernel - Re: [PATCH] mm/vmstat: do not use size of vmstat

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Date:   Sat, 19 Oct 2019 19:07:17 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmstat: do not use size of vmstat_text as count of
 /proc/vmstat items

On 10/19/19 2:45 PM, Konstantin Khlebnikov wrote:
> Strings from vmstat_text[] will be used for printing memory cgroup
> statistics which exists even if CONFIG_VM_EVENT_COUNTERS=n.
> 
> This should be applied before patch "mm/memcontrol: use vmstat names
> for printing statistics".
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> Link: https://lore.kernel.org/linux-mm/cd1c42ae-281f-c8a8-70ac-1d01d417b2e1@infradead.org/T/#u

Reported-by: Randy Dunlap <rdunlap@...radead.org>
Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested

Thanks.

> ---
>  mm/vmstat.c |   26 ++++++++++++--------------
>  1 file changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 590aeca27cab..13e36da70f3c 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1638,25 +1638,23 @@ static const struct seq_operations zoneinfo_op = {
>  	.show	= zoneinfo_show,
>  };
>  
> +#define NR_VMSTAT_ITEMS (NR_VM_ZONE_STAT_ITEMS + \
> +			 NR_VM_NUMA_STAT_ITEMS + \
> +			 NR_VM_NODE_STAT_ITEMS + \
> +			 NR_VM_WRITEBACK_STAT_ITEMS + \
> +			 (IS_ENABLED(CONFIG_VM_EVENT_COUNTERS) ? \
> +			  NR_VM_EVENT_ITEMS : 0))
> +
>  static void *vmstat_start(struct seq_file *m, loff_t *pos)
>  {
>  	unsigned long *v;
> -	int i, stat_items_size;
> +	int i;
>  
> -	if (*pos >= ARRAY_SIZE(vmstat_text))
> +	if (*pos >= NR_VMSTAT_ITEMS)
>  		return NULL;
> -	stat_items_size = NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long) +
> -			  NR_VM_NUMA_STAT_ITEMS * sizeof(unsigned long) +
> -			  NR_VM_NODE_STAT_ITEMS * sizeof(unsigned long) +
> -			  NR_VM_WRITEBACK_STAT_ITEMS * sizeof(unsigned long);
> -
> -#ifdef CONFIG_VM_EVENT_COUNTERS
> -	stat_items_size += sizeof(struct vm_event_state);
> -#endif
>  
> -	BUILD_BUG_ON(stat_items_size !=
> -		     ARRAY_SIZE(vmstat_text) * sizeof(unsigned long));
> -	v = kmalloc(stat_items_size, GFP_KERNEL);
> +	BUILD_BUG_ON(ARRAY_SIZE(vmstat_text) < NR_VMSTAT_ITEMS);
> +	v = kmalloc_array(NR_VMSTAT_ITEMS, sizeof(unsigned long), GFP_KERNEL);
>  	m->private = v;
>  	if (!v)
>  		return ERR_PTR(-ENOMEM);
> @@ -1689,7 +1687,7 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
>  static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
>  {
>  	(*pos)++;
> -	if (*pos >= ARRAY_SIZE(vmstat_text))
> +	if (*pos >= NR_VMSTAT_ITEMS)
>  		return NULL;
>  	return (unsigned long *)m->private + *pos;
>  }
> 


-- 
~Randy