Re: [PATCH] mm: pagealloc: fix continued prints in show_free_areas

From: Vlastimil Babka
Date: Tue Oct 18 2016 - 09:00:48 EST


On 10/18/2016 01:34 PM, Mark Rutland wrote:
Recently, printk was reworked in commit:

4bcc595ccd80decb ("printk: reinstate KERN_CONT for printing continuation
lines")

As of this commit, printk calls missing KERN_CONT will have a linebreak
inserted implicitly.

In show_free_areas, we miss KERN_CONT in a few cases, and as a result
prints are unexpectedly split over a number of lines, making them
difficult to read (in v4.9-rc1).

This patch uses pr_cont (with uits implicit KERN_CONT) to mark all
continued prints that occur withing a show_free_areas() call. Note that
show_migration_types() is only called by show_free_areas().
Depending on CONFIG_NUMA a printk after show_node() may or may not be a
continuation, but follows an explicit newline if not (and thus marking
it as a continuation should not be harmful).

I think this was already fixed:

http://marc.info/?l=linux-mm&m=147623910031630&w=2

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/page_alloc.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2b3bf67..833f271 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4224,7 +4224,7 @@ static void show_migration_types(unsigned char type)
}

*p = '\0';
- printk("(%s) ", tmp);
+ pr_cont("(%s) ", tmp);
}

/*
@@ -4335,7 +4335,7 @@ void show_free_areas(unsigned int filter)
free_pcp += per_cpu_ptr(zone->pageset, cpu)->pcp.count;

show_node(zone);
- printk("%s"
+ pr_cont("%s"
" free:%lukB"
" min:%lukB"
" low:%lukB"
@@ -4382,8 +4382,8 @@ void show_free_areas(unsigned int filter)
K(zone_page_state(zone, NR_FREE_CMA_PAGES)));
printk("lowmem_reserve[]:");
for (i = 0; i < MAX_NR_ZONES; i++)
- printk(" %ld", zone->lowmem_reserve[i]);
- printk("\n");
+ pr_cont(" %ld", zone->lowmem_reserve[i]);
+ pr_cont("\n");
}

for_each_populated_zone(zone) {
@@ -4394,7 +4394,7 @@ void show_free_areas(unsigned int filter)
if (skip_free_areas_node(filter, zone_to_nid(zone)))
continue;
show_node(zone);
- printk("%s: ", zone->name);
+ pr_cont("%s: ", zone->name);

spin_lock_irqsave(&zone->lock, flags);
for (order = 0; order < MAX_ORDER; order++) {
@@ -4412,11 +4412,11 @@ void show_free_areas(unsigned int filter)
}
spin_unlock_irqrestore(&zone->lock, flags);
for (order = 0; order < MAX_ORDER; order++) {
- printk("%lu*%lukB ", nr[order], K(1UL) << order);
+ pr_cont("%lu*%lukB ", nr[order], K(1UL) << order);
if (nr[order])
show_migration_types(types[order]);
}
- printk("= %lukB\n", K(total));
+ pr_cont("= %lukB\n", K(total));
}

hugetlb_show_meminfo();