| From | Mina Almasry <> | Date | Tue, 28 Jun 2022 14:58:32 -0700 | Subject | Re: [RFC PATCH 10/26] hugetlb: add for_each_hgm_shift |
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On Fri, Jun 24, 2022 at 10:37 AM James Houghton <jthoughton@google.com> wrote: > > This is a helper macro to loop through all the usable page sizes for a > high-granularity-enabled HugeTLB VMA. Given the VMA's hstate, it will > loop, in descending order, through the page sizes that HugeTLB supports > for this architecture; it always includes PAGE_SIZE. > > Signed-off-by: James Houghton <jthoughton@google.com> > --- > mm/hugetlb.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 8b10b941458d..557b0afdb503 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6989,6 +6989,16 @@ bool hugetlb_hgm_enabled(struct vm_area_struct *vma) > /* All shared VMAs have HGM enabled. */ > return vma->vm_flags & VM_SHARED; > } > +static unsigned int __shift_for_hstate(struct hstate *h) > +{ > + if (h >= &hstates[hugetlb_max_hstate]) > + return PAGE_SHIFT;
h > &hstates[hugetlb_max_hstate] means that h is out of bounds, no? am I missing something here?
So is this intending to do:
if (h == hstates[hugetlb_max_hstate] return PAGE_SHIFT;
? If so, could we write it as so?
I'm also wondering why __shift_for_hstate(hstate[hugetlb_max_hstate]) == PAGE_SHIFT? Isn't the last hstate the smallest hstate which should be 2MB on x86? Shouldn't this return PMD_SHIFT in that case?
> + return huge_page_shift(h); > +} > +#define for_each_hgm_shift(hstate, tmp_h, shift) \ > + for ((tmp_h) = hstate; (shift) = __shift_for_hstate(tmp_h), \ > + (tmp_h) <= &hstates[hugetlb_max_hstate]; \ > + (tmp_h)++) > #endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */ > > /* > -- > 2.37.0.rc0.161.g10f37bed90-goog >
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