Re: [PATCH 2/2] mm: Extract memcg maxable seq_file logic to seq_show_memcg_tunable

[Michal Hocko]

On Thu 24-01-19 14:41:00, Chris Down wrote:
> memcg has a significant number of files exposed to kernfs where their
> value is either exposed directly or is "max" in the case of
> PAGE_COUNTER_MAX.
> 
> This patch makes this generic by providing a single function to do this
> work. In combination with the previous patch adding mem_cgroup_from_seq,
> this makes all of the seq_show feeder functions significantly more
> simple.

Yeah this is what I've had in mind when mentioning a helper in the
previous version of the patch. I like this more even though the
resulting savings are not that large.

> Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Roman Gushchin <guro@xxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: cgroups@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: kernel-team@xxxxxx

Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  mm/memcontrol.c | 64 +++++++++++++++----------------------------------
>  1 file changed, 19 insertions(+), 45 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 98aad31f5226..81b6f752471a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5375,6 +5375,16 @@ static void mem_cgroup_bind(struct cgroup_subsys_state *root_css)
>  		root_mem_cgroup->use_hierarchy = false;
>  }
>  
> +static int seq_puts_memcg_tunable(struct seq_file *m, unsigned long value)
> +{
> +	if (value == PAGE_COUNTER_MAX)
> +		seq_puts(m, "max\n");
> +	else
> +		seq_printf(m, "%llu\n", (u64)value * PAGE_SIZE);
> +
> +	return 0;
> +}
> +
>  static u64 memory_current_read(struct cgroup_subsys_state *css,
>  			       struct cftype *cft)
>  {
> @@ -5385,15 +5395,8 @@ static u64 memory_current_read(struct cgroup_subsys_state *css,
>  
>  static int memory_min_show(struct seq_file *m, void *v)
>  {
> -	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
> -	unsigned long min = READ_ONCE(memcg->memory.min);
> -
> -	if (min == PAGE_COUNTER_MAX)
> -		seq_puts(m, "max\n");
> -	else
> -		seq_printf(m, "%llu\n", (u64)min * PAGE_SIZE);
> -
> -	return 0;
> +	return seq_puts_memcg_tunable(m,
> +		READ_ONCE(mem_cgroup_from_seq(m)->memory.min));
>  }
>  
>  static ssize_t memory_min_write(struct kernfs_open_file *of,
> @@ -5415,15 +5418,8 @@ static ssize_t memory_min_write(struct kernfs_open_file *of,
>  
>  static int memory_low_show(struct seq_file *m, void *v)
>  {
> -	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
> -	unsigned long low = READ_ONCE(memcg->memory.low);
> -
> -	if (low == PAGE_COUNTER_MAX)
> -		seq_puts(m, "max\n");
> -	else
> -		seq_printf(m, "%llu\n", (u64)low * PAGE_SIZE);
> -
> -	return 0;
> +	return seq_puts_memcg_tunable(m,
> +		READ_ONCE(mem_cgroup_from_seq(m)->memory.low));
>  }
>  
>  static ssize_t memory_low_write(struct kernfs_open_file *of,
> @@ -5445,15 +5441,7 @@ static ssize_t memory_low_write(struct kernfs_open_file *of,
>  
>  static int memory_high_show(struct seq_file *m, void *v)
>  {
> -	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
> -	unsigned long high = READ_ONCE(memcg->high);
> -
> -	if (high == PAGE_COUNTER_MAX)
> -		seq_puts(m, "max\n");
> -	else
> -		seq_printf(m, "%llu\n", (u64)high * PAGE_SIZE);
> -
> -	return 0;
> +	return seq_puts_memcg_tunable(m, READ_ONCE(mem_cgroup_from_seq(m)->high));
>  }
>  
>  static ssize_t memory_high_write(struct kernfs_open_file *of,
> @@ -5482,15 +5470,8 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
>  
>  static int memory_max_show(struct seq_file *m, void *v)
>  {
> -	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
> -	unsigned long max = READ_ONCE(memcg->memory.max);
> -
> -	if (max == PAGE_COUNTER_MAX)
> -		seq_puts(m, "max\n");
> -	else
> -		seq_printf(m, "%llu\n", (u64)max * PAGE_SIZE);
> -
> -	return 0;
> +	return seq_puts_memcg_tunable(m,
> +		READ_ONCE(mem_cgroup_from_seq(m)->memory.max));
>  }
>  
>  static ssize_t memory_max_write(struct kernfs_open_file *of,
> @@ -6622,15 +6603,8 @@ static u64 swap_current_read(struct cgroup_subsys_state *css,
>  
>  static int swap_max_show(struct seq_file *m, void *v)
>  {
> -	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
> -	unsigned long max = READ_ONCE(memcg->swap.max);
> -
> -	if (max == PAGE_COUNTER_MAX)
> -		seq_puts(m, "max\n");
> -	else
> -		seq_printf(m, "%llu\n", (u64)max * PAGE_SIZE);
> -
> -	return 0;
> +	return seq_puts_memcg_tunable(m,
> +		READ_ONCE(mem_cgroup_from_seq(m)->swap.max));
>  }
>  
>  static ssize_t swap_max_write(struct kernfs_open_file *of,
> -- 
> 2.20.1

-- 
Michal Hocko
SUSE Labs