Re: memory_hotplug: zone_can_shift() returns boolean value

From: Yasuaki Ishimatsu
Date: Tue Dec 13 2016 - 11:47:58 EST


Hi Reza,

Thank you for your review.

On 12/13/2016 10:54 AM, Reza Arbab wrote:
On Mon, Dec 12, 2016 at 03:29:04PM -0500, Yasuaki Ishimatsu wrote:
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -410,15 +410,13 @@ static ssize_t show_valid_zones(struct device *dev,
sprintf(buf, "%s", zone->name);

/* MMOP_ONLINE_KERNEL */
- zone_shift = zone_can_shift(start_pfn, nr_pages, ZONE_NORMAL);
- if (zone_shift) {
+ if (zone_can_shift(start_pfn, nr_pages, ZONE_NORMAL, &zone_shift)) {
strcat(buf, " ");
strcat(buf, (zone + zone_shift)->name);
}

/* MMOP_ONLINE_MOVABLE */
- zone_shift = zone_can_shift(start_pfn, nr_pages, ZONE_MOVABLE);
- if (zone_shift) {
+ if (zone_can_shift(start_pfn, nr_pages, ZONE_MOVABLE, &zone_shift)) {
strcat(buf, " ");
strcat(buf, (zone + zone_shift)->name);
}

You still need to check zone_shift != 0, otherwise you may get duplicate output:

$ cat /sys/devices/system/node/node1/memory256/valid_zones
Movable Normal Movable
$ cat /sys/devices/system/node/node1/memory257/valid_zones
Movable Movable

I'll update it.


--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1033,8 +1033,8 @@ static void node_states_set_node(int node, struct memory_notify *arg)
node_set_state(node, N_MEMORY);
}

-int zone_can_shift(unsigned long pfn, unsigned long nr_pages,
- enum zone_type target)
+bool zone_can_shift(unsigned long pfn, unsigned long nr_pages,
+ enum zone_type target, int *zone_shift)
{
struct zone *zone = page_zone(pfn_to_page(pfn));
enum zone_type idx = zone_idx(zone);

I think you should initialize zone_shift here. It should be 0 if the function returns false.

*zone_shift = 0;

I'll update it.

Thanks,
Yasuaki Ishimatsu

@@ -1043,26 +1043,27 @@ int zone_can_shift(unsigned long pfn, unsigned long nr_pages,
if (idx < target) {
/* pages must be at end of current zone */
if (pfn + nr_pages != zone_end_pfn(zone))
- return 0;
+ return false;

/* no zones in use between current zone and target */
for (i = idx + 1; i < target; i++)
if (zone_is_initialized(zone - idx + i))
- return 0;
+ return false;
}

if (target < idx) {
/* pages must be at beginning of current zone */
if (pfn != zone->zone_start_pfn)
- return 0;
+ return false;

/* no zones in use between current zone and target */
for (i = target + 1; i < idx; i++)
if (zone_is_initialized(zone - idx + i))
- return 0;
+ return false;
}

- return target - idx;
+ *zone_shift = target - idx;
+ return true;
}

/* Must be protected by mem_hotplug_begin() */
@@ -1089,10 +1090,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
!can_online_high_movable(zone))
return -EINVAL;

- if (online_type == MMOP_ONLINE_KERNEL)
- zone_shift = zone_can_shift(pfn, nr_pages, ZONE_NORMAL);
- else if (online_type == MMOP_ONLINE_MOVABLE)
- zone_shift = zone_can_shift(pfn, nr_pages, ZONE_MOVABLE);
+ if (online_type == MMOP_ONLINE_KERNEL) {
+ if (!zone_can_shift(pfn, nr_pages, ZONE_NORMAL, &zone_shift))
+ return -EINVAL;
+ } else if (online_type == MMOP_ONLINE_MOVABLE) {
+ if (!zone_can_shift(pfn, nr_pages, ZONE_MOVABLE, &zone_shift))
+ return -EINVAL;
+ }

zone = move_pfn_range(zone_shift, pfn, pfn + nr_pages);
if (!zone)
--
1.8.3.1