Commit 5b8d6e37 authored Jan 30, 2020 by Li Xinhai Committed by Linus Torvalds Jan 31, 2020

mm/page_vma_mapped.c: explicitly compare pfn for normal, hugetlbfs and THP page

When check_pte, pfn of normal, hugetlbfs and THP page need be compared.
The current implementation apply comparison as

- normal 4K page: page_pfn <= pfn < page_pfn + 1
- hugetlbfs page:  page_pfn <= pfn < page_pfn + HPAGE_PMD_NR
- THP page: page_pfn <= pfn < page_pfn + HPAGE_PMD_NR

in pfn_in_hpage.  For hugetlbfs page, it should be page_pfn == pfn

Now, change pfn_in_hpage to pfn_is_match to highlight that comparison is
not only for THP and explicitly compare for these cases.

No impact upon current behavior, just make the code clear.  I think it
is important to make the code clear - comparing hugetlbfs page in range
page_pfn <= pfn < page_pfn + HPAGE_PMD_NR is confusing.

Link: http://lkml.kernel.org/r/1578737885-8890-1-git-send-email-lixinhai.lxh@gmail.com


Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 92855270

mm/page_vma_mapped.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -52,12 +52,16 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw)
		return true;
		}

		static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn)
		static inline bool pfn_is_match(struct page *page, unsigned long pfn)
		{
		unsigned long hpage_pfn = page_to_pfn(hpage);
		unsigned long page_pfn = page_to_pfn(page);

		/* normal page and hugetlbfs page */
		if (!PageTransCompound(page) \|\| PageHuge(page))
		return page_pfn == pfn;

		/* THP can be referenced by any subpage */
		return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage);
		return pfn >= page_pfn && pfn - page_pfn < hpage_nr_pages(page);
		}

		/**
		@@ -108,7 +112,7 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw)
		pfn = pte_pfn(*pvmw->pte);
		}

		return pfn_in_hpage(pvmw->page, pfn);
		return pfn_is_match(pvmw->page, pfn);
		}

		/**

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