On Mon, 26 Aug 2019 06:18:58 -0700 Matthew Wilcox <[email protected]> wrote:
> Why did you not cc Gerald who wrote the patch? You can't just > run get_maintainers.pl and call it good. > > On Sun, Aug 25, 2019 at 02:06:21PM -0600, Yu Zhao wrote: > > For hugely mapped thp, we use is_huge_zero_pmd() to check if it's > > zero page or not. > > > > We do fill ptes with my_zero_pfn() when we split zero thp pmd, but > > this is not what we have in vm_normal_page_pmd(). > > pmd_trans_huge_lock() makes sure of it. > > > > This is a trivial fix for /proc/pid/numa_maps, and AFAIK nobody > > complains about it. > > > > Signed-off-by: Yu Zhao <[email protected]> > > --- > > mm/memory.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/memory.c b/mm/memory.c > > index e2bb51b6242e..ea3c74855b23 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -654,7 +654,7 @@ struct page *vm_normal_page_pmd(struct vm_area_struct > > *vma, unsigned long addr, > > > > if (pmd_devmap(pmd)) > > return NULL; > > - if (is_zero_pfn(pfn)) > > + if (is_huge_zero_pmd(pmd)) > > return NULL; > > if (unlikely(pfn > highest_memmap_pfn)) > > return NULL; > > -- > > 2.23.0.187.g17f5b7556c-goog > > Looks good to me. The "_pmd" versions for can_gather_numa_stats() and vm_normal_page() were introduced to avoid using pte_present/dirty() on pmds, which is not affected by this patch. In fact, for vm_normal_page_pmd() I basically copied most of the code from vm_normal_page(), including the is_zero_pfn(pfn) check, which does look wrong to me now. Using is_huge_zero_pmd() should be correct. Maybe the description could also mention the symptom of this bug? I would assume that it affects anon/dirty accounting in gather_pte_stats(), for huge mappings, if zero page mappings are not correctly recognized. Regards, Gerald
