Re: memory_hotplug: zone_can_shift() returns boolean value

[Yasuaki Ishimatsu]

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