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

From: Michal Hocko
Date: Wed Oct 12 2016 - 05:10:34 EST


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?
---
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++) {
--
Michal Hocko
SUSE Labs