The patch titled
page_alloc: Oops when setting percpu_pagelist_fraction
has been added to the -mm tree. Its filename is
page_alloc-oops-when-setting-percpu_pagelist_fraction.patch
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------------------------------------------------------
Subject: page_alloc: Oops when setting percpu_pagelist_fraction
From: Dimitri Sivanich <sivanich@xxxxxxx>
After downing/upping a cpu, an attempt to set
/proc/sys/vm/percpu_pagelist_fraction results in an oops in
percpu_pagelist_fraction_sysctl_handler().
To reproduce this:
localhost:/sys/devices/system/cpu/cpu6 # echo 0 >online
localhost:/sys/devices/system/cpu/cpu6 # echo 1 >online
localhost:/sys/devices/system/cpu/cpu6 # cd /proc/sys/vm
localhost:/proc/sys/vm # echo 100000 >percpu_pagelist_fraction
BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
IP: [<ffffffff80286946>] percpu_pagelist_fraction_sysctl_handler+0x4a/0x96
This is because the zone->pageset[cpu] value has not been set when the cpu
has been brought back up for unpopulated zones (the "Movable" zone in the
case I'm running into). Prior to downing/upping the cpu it had been set
to &boot_pageset[cpu].
There are two possible fixes that come to mind. One is to check for an
unpopulated zone or NULL zone pageset for that cpu in
percpu_pagelist_fraction_sysctl_handler(), and simply not set a pagelist
highmark for that zone/cpu combination.
The other, and the one I'm proposing here, is to set the zone's pageset
back to the boot_pageset when the cpu is brought back up if the zone is
unpopulated.
Signed-off-by: Dimitri Sivanich <sivanich@xxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff -puN mm/page_alloc.c~page_alloc-oops-when-setting-percpu_pagelist_fraction mm/page_alloc.c
--- a/mm/page_alloc.c~page_alloc-oops-when-setting-percpu_pagelist_fraction
+++ a/mm/page_alloc.c
@@ -2806,7 +2806,11 @@ static int __cpuinit process_zones(int c
node_set_state(node, N_CPU); /* this node has a cpu */
- for_each_populated_zone(zone) {
+ for_each_zone(zone) {
+ if (!populated_zone(zone)) {
+ zone_pcp(zone, cpu) = &boot_pageset[cpu];
+ continue;
+ }
zone_pcp(zone, cpu) = kmalloc_node(sizeof(struct per_cpu_pageset),
GFP_KERNEL, node);
if (!zone_pcp(zone, cpu))
_
Patches currently in -mm which might be from sivanich@xxxxxxx are
page_alloc-oops-when-setting-percpu_pagelist_fraction.patch
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