Re: [PATCH] hibernate / memory hotplug: always use for_each_populated_zone()

[Nigel Cunningham <ncunningham@crca.org.au>]

Hi.

Gerald Schaefer wrote:
> From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> 
> Use for_each_populated_zone() instead of for_each_zone() in hibernation
> code. This fixes a bug on s390, where we allow both config options
> HIBERNATION and MEMORY_HOTPLUG, so that we also have a ZONE_MOVABLE
> here. We only allow hibernation if no memory hotplug operation was
> performed, so in fact both features can only be used exclusively, but
> this way we don't need 2 differently configured (distribution) kernels.
> 
> If we have an unpopulated ZONE_MOVABLE, we allow hibernation but run
> into a BUG_ON() in memory_bm_test/set/clear_bit() because hibernation
> code iterates through all zones, not only the populated zones, in
> several places. For example, swsusp_free() does for_each_zone() and
> then checks for pfn_valid(), which is true even if the zone is not
> populated, resulting in a BUG_ON() later because the pfn cannot be
> found in the memory bitmap.

I agree with your logic and patch, but doesn't this also imply that the
s390 implementation pfn_valid should be changed to return false for
those pages?

Regards,

Nigel