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SubjectRe: memory_hotplug: zone_can_shift() returns boolean value
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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
>>
>

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