On 27.10.19 23:27, David Hildenbrand wrote:
We recently started updating the node span based on the zone span to
avoid touching uninitialized memmaps.
Currently, we will always detect the node span to start at 0, meaning a
node can easily span too many pages. pgdat_is_empty() will still work
correctly if all zones span no pages. We should skip over all zones without
spanned pages and properly handle the first detected zone that spans pages.
Unfortunately, in contrast to the zone span (/proc/zoneinfo), the node span
cannot easily be inspected and tested. The node span gives no real
guarantees when an architecture supports memory hotplug, meaning it can
easily contain holes or span pages of different nodes.
The node span is not really used after init on architectures that support
memory hotplug. E.g., we use it in mm/memory_hotplug.c:try_offline_node()
and in mm/kmemleak.c:kmemleak_scan(). These users seem to be fine.
Fixes: 00d6c019b5bc ("mm/memory_hotplug: don't access uninitialized memmaps in shrink_pgdat_span()")
@Andrew, can we also give this a churn, we should try to get this into
5.4 due to
$ git tag --contains 00d6c019b5bc
[...]
v5.4-rc5
Thanks!
--
Thanks,
David / dhildenb
