On 10.12.2018 19:19, Michal Hocko wrote: > On Mon 10-12-18 16:45:37, Zaslonko Mikhail wrote: >> Hello, >> >> On 10.12.2018 14:24, Michal Hocko wrote: > [...] >>> Why do we need to restrict this to the highest zone? In other words, why >>> cannot we do what I was suggesting earlier [1]. What does prevent other >>> zones to have an incomplete section boundary? >> >> Well, as you were also suggesting earlier: 'If we do not have a zone which >> spans the rest of the section'. I'm not sure how else we should verify that. > > I am not sure I follow here. Why cannot we simply drop end_pfn check and > keep the rest? > >> Moreover, I was able to recreate the problem only with the highest zone >> (memory end is not on the section boundary). > > What exactly prevents exactmap memmap to generate these unfinished zones? Probably you're right. I'm re-sending the patch V2. > >>> [1] http://lkml.kernel.org/r/20181105183533.GQ4361@xxxxxxxxxxxxxx >>> >>>> Signed-off-by: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx> >>>> Reviewed-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx> >>>> Cc: <stable@xxxxxxxxxxxxxxx> >>>> --- >>>> mm/page_alloc.c | 15 +++++++++++++++ >>>> 1 file changed, 15 insertions(+) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index 2ec9cc407216..41ef5508e5f1 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -5542,6 +5542,21 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, >>>> cond_resched(); >>>> } >>>> } >>>> +#ifdef CONFIG_SPARSEMEM >>>> + /* >>>> + * If there is no zone spanning the rest of the section >>>> + * then we should at least initialize those pages. Otherwise we >>>> + * could blow up on a poisoned page in some paths which depend >>>> + * on full sections being initialized (e.g. memory hotplug). >>>> + */ >>>> + if (end_pfn == max_pfn) { >>>> + while (end_pfn % PAGES_PER_SECTION) { >>>> + __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, >>>> + nid); >>>> + end_pfn++; >>>> + } >>>> + } >>>> +#endif >>>> } >>>> >>>> #ifdef CONFIG_ZONE_DEVICE >>>> -- >>>> 2.16.4 >>> >> >> Thanks, >> Mikhail Zaslonko >
