linux-kernel - Re: [PATCH] mm: page_alloc: Use KERN

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Date:   Wed, 12 Oct 2016 11:10:13 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Joe Perches <joe@...ches.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: page_alloc: Use KERN_CONT where appropriate

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@aaronlu.sh.intel.com
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@...ches.com>

Acked-by: Michal Hocko <mhocko@...e.com>

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