Re: [patch 2/5] mm: writeback: make determine_dirtyable_memory static again

[Michal Hocko <mhocko@suse.cz>]

On Mon 25-07-11 22:19:16, Johannes Weiner wrote:
> From: Johannes Weiner <hannes@cmpxchg.org>
> 
> The tracing ring-buffer used this function briefly, but not anymore.
> Make it local to the writeback code again.
> 
> Also, move the function so that no forward declaration needs to be
> reintroduced.

git grep says that the only reference is from the page-writeback.c and
the symbol is not exported to modules so this looks correct.
Moving it up in the file certainly makes sense.

> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
>  include/linux/writeback.h |    2 -
>  mm/page-writeback.c       |   85 ++++++++++++++++++++++-----------------------
>  2 files changed, 42 insertions(+), 45 deletions(-)
> 
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index 17e7ccc..8c63f3a 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -105,8 +105,6 @@ extern int vm_highmem_is_dirtyable;
>  extern int block_dump;
>  extern int laptop_mode;
>  
> -extern unsigned long determine_dirtyable_memory(void);
> -
>  extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
>  		void __user *buffer, size_t *lenp,
>  		loff_t *ppos);
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 31f6988..a4de005 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -111,6 +111,48 @@ EXPORT_SYMBOL(laptop_mode);
>  
>  /* End of sysctl-exported parameters */
>  
> +static unsigned long highmem_dirtyable_memory(unsigned long total)
> +{
> +#ifdef CONFIG_HIGHMEM
> +	int node;
> +	unsigned long x = 0;
> +
> +	for_each_node_state(node, N_HIGH_MEMORY) {
> +		struct zone *z =
> +			&NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
> +
> +		x += zone_page_state(z, NR_FREE_PAGES) +
> +		     zone_reclaimable_pages(z);
> +	}
> +	/*
> +	 * Make sure that the number of highmem pages is never larger
> +	 * than the number of the total dirtyable memory. This can only
> +	 * occur in very strange VM situations but we want to make sure
> +	 * that this does not occur.
> +	 */
> +	return min(x, total);
> +#else
> +	return 0;
> +#endif
> +}
> +
> +/**
> + * determine_dirtyable_memory - amount of memory that may be used
> + *
> + * Returns the numebr of pages that can currently be freed and used
> + * by the kernel for direct mappings.
> + */
> +static unsigned long determine_dirtyable_memory(void)
> +{
> +	unsigned long x;
> +
> +	x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
> +
> +	if (!vm_highmem_is_dirtyable)
> +		x -= highmem_dirtyable_memory(x);
> +
> +	return x + 1;	/* Ensure that we never return 0 */
> +}
>  
>  /*
>   * Scale the writeback cache size proportional to the relative writeout speeds.
> @@ -354,49 +396,6 @@ EXPORT_SYMBOL(bdi_set_max_ratio);
>   * clamping level.
>   */
>  
> -static unsigned long highmem_dirtyable_memory(unsigned long total)
> -{
> -#ifdef CONFIG_HIGHMEM
> -	int node;
> -	unsigned long x = 0;
> -
> -	for_each_node_state(node, N_HIGH_MEMORY) {
> -		struct zone *z =
> -			&NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
> -
> -		x += zone_page_state(z, NR_FREE_PAGES) +
> -		     zone_reclaimable_pages(z);
> -	}
> -	/*
> -	 * Make sure that the number of highmem pages is never larger
> -	 * than the number of the total dirtyable memory. This can only
> -	 * occur in very strange VM situations but we want to make sure
> -	 * that this does not occur.
> -	 */
> -	return min(x, total);
> -#else
> -	return 0;
> -#endif
> -}
> -
> -/**
> - * determine_dirtyable_memory - amount of memory that may be used
> - *
> - * Returns the numebr of pages that can currently be freed and used
> - * by the kernel for direct mappings.
> - */
> -unsigned long determine_dirtyable_memory(void)
> -{
> -	unsigned long x;
> -
> -	x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
> -
> -	if (!vm_highmem_is_dirtyable)
> -		x -= highmem_dirtyable_memory(x);
> -
> -	return x + 1;	/* Ensure that we never return 0 */
> -}
> -
>  /*
>   * global_dirty_limits - background-writeback and dirty-throttling thresholds
>   *
> -- 
> 1.7.6
> 
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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