On 14.08.19 20:32, Michal Hocko wrote: > On Wed 14-08-19 18:09:16, David Hildenbrand wrote: >> On 14.08.19 17:41, David Hildenbrand wrote: >>> Commit a9cd410a3d29 ("mm/page_alloc.c: memory hotplug: free pages as higher >>> order") assumed that any PFN we get via memory resources is aligned to >>> to MAX_ORDER - 1, I am not convinced that is always true. Let's play safe, >>> check the alignment and fallback to single pages. >>> >>> Cc: Arun KS <arunks@xxxxxxxxxxxxxx> >>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >>> Cc: Oscar Salvador <osalvador@xxxxxxx> >>> Cc: Michal Hocko <mhocko@xxxxxxxx> >>> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> >>> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> >>> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> >>> --- >>> mm/memory_hotplug.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 63b1775f7cf8..f245fb50ba7f 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -646,6 +646,9 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages, >>> */ >>> for (pfn = start_pfn; pfn < end_pfn; pfn += 1ul << order) { >>> order = min(MAX_ORDER - 1, get_order(PFN_PHYS(end_pfn - pfn))); >>> + /* __free_pages_core() wants pfns to be aligned to the order */ >>> + if (unlikely(!IS_ALIGNED(pfn, 1ul << order))) >>> + order = 0; >>> (*online_page_callback)(pfn_to_page(pfn), order); >>> } >>> >>> >> >> @Michal, if you insist, we can drop this patch. "break first and fix >> later" is not part of my DNA :) > > I do not insist but have already expressed that I am not a fan of this > change. Also I think that "break first" is quite an over statement here. > Well this version is certainly nicer than the previous one. I'll let Andrew decide if he wants to pick it up or drop it from this series. Thanks! -- Thanks, David / dhildenb