Messages in this thread | | | Date | Thu, 28 Nov 2019 21:22:26 +0000 | From | Wei Yang <> | Subject | Re: [PATCH 1/2] mm/page_vma_mapped: use PMD_SIZE instead of calculating it |
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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?
Search in the kernel tree, one implementation of PUD_SIZE fault is dev_dax_huge_fault. If page fault happens here, would this if break the loop too early?
>-- > Kirill A. Shutemov
-- Wei Yang Help you, Help me
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