Re: [PATCH v2 10/10] mm/memory_hotplug: mark pageblocks MIGRATE_ISOLATE while onlining memory

[Oscar Salvador]

On Wed, Aug 19, 2020 at 07:59:57PM +0200, David Hildenbrand wrote:
> Currently, it can happen that pages are allocated (and freed) via the buddy
> before we finished basic memory onlining.
> 
> For example, pages are exposed to the buddy and can be allocated before
> we actually mark the sections online. Allocated pages could suddenly
> fail pfn_to_online_page() checks. We had similar issues with pcp
> handling, when pages are allocated+freed before we reach
> zone_pcp_update() in online_pages() [1].
> 
> Instead, mark all pageblocks MIGRATE_ISOLATE, such that allocations are
> impossible. Once done with the heavy lifting, use
> undo_isolate_page_range() to move the pages to the MIGRATE_MOVABLE
> freelist, marking them ready for allocation. Similar to offline_pages(),
> we have to manually adjust zone->nr_isolate_pageblock.
> 
> [1] https://lkml.kernel.org/r/1597150703-19003-1-git-send-email-charante@xxxxxxxxxxxxxx
> 
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
> Cc: Baoquan He <bhe@xxxxxxxxxx>
> Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Cc: Charan Teja Reddy <charante@xxxxxxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>

-- 
Oscar Salvador
SUSE L3