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    SubjectRe: [PATCH 1/2] mm/page_vma_mapped: use PMD_SIZE instead of calculating it
    On Mon, Dec 02, 2019 at 11:03:15AM +0300, Kirill A. Shutemov wrote:
    >On Thu, Nov 28, 2019 at 09:22:26PM +0000, Wei Yang wrote:
    >> On Thu, Nov 28, 2019 at 11:32:55AM +0300, Kirill A. Shutemov wrote:
    >> >On Thu, Nov 28, 2019 at 09:03:20AM +0800, Wei Yang wrote:
    >> >> At this point, we are sure page is PageTransHuge, which means
    >> >> hpage_nr_pages is HPAGE_PMD_NR.
    >> >>
    >> >> This is safe to use PMD_SIZE instead of calculating it.
    >> >>
    >> >> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
    >> >> ---
    >> >> mm/page_vma_mapped.c | 2 +-
    >> >> 1 file changed, 1 insertion(+), 1 deletion(-)
    >> >>
    >> >> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
    >> >> index eff4b4520c8d..76e03650a3ab 100644
    >> >> --- a/mm/page_vma_mapped.c
    >> >> +++ b/mm/page_vma_mapped.c
    >> >> @@ -223,7 +223,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
    >> >> if (pvmw->address >= pvmw->vma->vm_end ||
    >> >> pvmw->address >=
    >> >> __vma_address(pvmw->page, pvmw->vma) +
    >> >> - hpage_nr_pages(pvmw->page) * PAGE_SIZE)
    >> >> + PMD_SIZE)
    >> >> return not_found(pvmw);
    >> >> /* Did we cross page table boundary? */
    >> >> if (pvmw->address % PMD_SIZE == 0) {
    >> >
    >> >It is dubious cleanup. Maybe page_size(pvmw->page) instead? It will not
    >> >break if we ever get PUD THP pages.
    >> >
    >>
    >> Thanks for your comment.
    >>
    >> I took a look into the code again and found I may miss something.
    >>
    >> I found we support PUD THP pages, whilc hpage_nr_pages() just return
    >> HPAGE_PMD_NR on PageTransHuge. Why this is not possible to return PUD number?
    >
    >We only support PUD THP for DAX. Means, we don't have struct page for it.
    >

    Ok, many background story behind it.

    Thanks :-)

    >--
    > Kirill A. Shutemov

    --
    Wei Yang
    Help you, Help me

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