4 fixes, based on 5092adb2272e1760030a889aa4a3e9cf1d5f74b5: Subject: mm, memory_hotplug: initialize struct pages for the full memory section Subject: mm: thp: fix flags for pmd migration when split Subject: fork,memcg: fix crash in free_thread_stack on memcg charge fail Subject: mm, page_alloc: fix has_unmovable_pages for HugePages
