In free_hot_cold_page(), we rely on pcp->batch remaining stable.
Updating it without being on the cpu owning the percpu pageset
potentially destroys this stability.

Change for_each_cpu() to on_each_cpu() to fix.

Signed-off-by: Cody P Schafer <c...@linux.vnet.ibm.com>
---
 mm/page_alloc.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 48f2faa..507db31 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5475,30 +5475,31 @@ int lowmem_reserve_ratio_sysctl_handler(ctl_table 
*table, int write,
        return 0;
 }
 
+static void _zone_set_pageset_highmark(void *data)
+{
+       struct zone *zone = data;
+       unsigned long  high;
+       high = zone->managed_pages / percpu_pagelist_fraction;
+       setup_pagelist_highmark(
+                       per_cpu_ptr(zone->pageset, smp_processor_id()), high);
+}
+
 /*
  * percpu_pagelist_fraction - changes the pcp->high for each zone on each
  * cpu.  It is the fraction of total pages in each zone that a hot per cpu 
pagelist
  * can have before it gets flushed back to buddy allocator.
  */
-
 int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
        void __user *buffer, size_t *length, loff_t *ppos)
 {
        struct zone *zone;
-       unsigned int cpu;
        int ret;
 
        ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
        if (!write || (ret < 0))
                return ret;
-       for_each_populated_zone(zone) {
-               for_each_possible_cpu(cpu) {
-                       unsigned long  high;
-                       high = zone->managed_pages / percpu_pagelist_fraction;
-                       setup_pagelist_highmark(
-                               per_cpu_ptr(zone->pageset, cpu), high);
-               }
-       }
+       for_each_populated_zone(zone)
+               on_each_cpu(_zone_set_pageset_highmark, zone, true);
        return 0;
 }
 
-- 
1.8.2

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