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

[Vlastimil Babka]

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.rutl...@arm.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Vlastimil Babka <vba...@suse.cz>
Cc: Mel Gorman <mgor...@techsingularity.net>
Cc: linux...@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 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();