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? > > [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 -- Michal Hocko SUSE Labs
