Re: [PATCH] mm: page_alloc: Use KERN_CONT where appropriate

From: Joe Perches
Date: Wed Oct 12 2016 - 06:37:31 EST


(resending as lkml bounced)

On Wed, 2016-10-12 at 11:10 +0200, Michal Hocko wrote:
> On Tue 11-10-16 19:24:55, Joe Perches wrote:
> > Recent changes to printk require KERN_CONT uses to continue logging
> > messages. So add KERN_CONT where necessary.
>
>
>
> I was really wondering what happened when Aaron reported an allocation
> failure http://lkml.kernel.org/r/20161012065423.GA16092@xxxxxxxxxxxxxxxxxxxx
> See the attached log got the current Linus' tree
>
> Fixes: 4bcc595ccd80 ("printk: reinstate KERN_CONT for printing continuation lines")
> > Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
>
>
>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
>
> I believe we can simplify the code a bit as well. What do you think
> about the following on top?


Hi Michal

I think the show_node to show_zone_node renaming is superfluous,
but if it makes you happy, it doesn't bother me.

This recent change to printk logging making KERN_CONT necessary to
continue a line might be reverted when it's better known just how
many instances in the kernel tree will need to be changed.

For now, I'd rather keep the KERN_CONT "\n" and trailing "\n" as
there are _very_ few missing newlines in logging messages today
and removing them now might be a bit early process-wise.

Dunno.

> ---
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6f8c356140a0..7e1b74ee79cb 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4078,10 +4078,12 @@ unsigned long nr_free_pagecache_pages(void)
> return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
> }
>
> -static inline void show_node(struct zone *zone)
> +static inline void show_zone_node(struct zone *zone)
> {
> if (IS_ENABLED(CONFIG_NUMA))
> - printk("Node %d ", zone_to_nid(zone));
> + printk("Node %d %s", zone_to_nid(zone), zone->name);
> + else
> + printk("%s: ", zone->name);
> }
>
> long si_mem_available(void)
> @@ -4329,9 +4331,8 @@ void show_free_areas(unsigned int filter)
> for_each_online_cpu(cpu)
> free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count;
>
> - show_node(zone);
> + show_zone_node(zone);
> printk(KERN_CONT
> - "%s"
> " free:%lukB"
> " min:%lukB"
> " low:%lukB"
> @@ -4354,7 +4355,6 @@ void show_free_areas(unsigned int filter)
> " local_pcp:%ukB"
> " free_cma:%lukB"
> "\n",
> - zone->name,
> K(zone_page_state(zone, NR_FREE_PAGES)),
> K(min_wmark_pages(zone)),
> K(low_wmark_pages(zone)),
> @@ -4379,7 +4379,6 @@ void show_free_areas(unsigned int filter)
> printk("lowmem_reserve[]:");
> for (i = 0; i < MAX_NR_ZONES; i++)
> printk(KERN_CONT " %ld", zone->lowmem_reserve[i]);
> - printk(KERN_CONT "\n");
> }
>
> for_each_populated_zone(zone) {
> @@ -4389,8 +4388,7 @@ void show_free_areas(unsigned int filter)
>
> if (skip_free_areas_node(filter, zone_to_nid(zone)))
> continue;
> - show_node(zone);
> - printk(KERN_CONT "%s: ", zone->name);
> + show_zone_node(zone);
>
> spin_lock_irqsave(&zone->lock, flags);
> for (order = 0; order < MAX_ORDER; order++) {