A hugetlb page will have a mapcount of 1 if mapped by multiple processes via a shared PMD. This is because only the first process increases the map count, and subsequent processes just add the shared PMD page to their page table.
page_mapcount is being used to decide if a hugetlb page is shared or private in /proc/PID/smaps. Pages referenced via a shared PMD were incorrectly being counted as private.
To fix, check for a shared PMD if mapcount is 1. If a shared PMD is found count the hugetlb page as shared. A new helper to check for a shared PMD is added.
Fixes: 25ee01a2fca0 ("mm: hugetlb: proc: add hugetlb-related fields to /proc/PID/smaps") Cc: stable@vger.kernel.org Signed-off-by: Mike Kravetz mike.kravetz@oracle.com --- fs/proc/task_mmu.c | 10 ++++++++-- include/linux/hugetlb.h | 12 ++++++++++++ 2 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index e35a0398db63..cb9539879402 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -749,8 +749,14 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
if (mapcount >= 2) mss->shared_hugetlb += huge_page_size(hstate_vma(vma)); - else - mss->private_hugetlb += huge_page_size(hstate_vma(vma)); + else { + if (hugetlb_pmd_shared(pte)) + mss->shared_hugetlb += + huge_page_size(hstate_vma(vma)); + else + mss->private_hugetlb += + huge_page_size(hstate_vma(vma)); + } } return 0; } diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index e3aa336df900..8e65920e4363 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -1225,6 +1225,18 @@ static inline __init void hugetlb_cma_reserve(int order) } #endif
+#ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE +static inline bool hugetlb_pmd_shared(pte_t *pte) +{ + return page_count(virt_to_page(pte)) > 1; +} +#else +static inline bool hugetlb_pmd_shared(pte_t *pte) +{ + return false; +} +#endif + bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr);
#ifndef __HAVE_ARCH_FLUSH_HUGETLB_TLB_RANGE