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@xxxxxxxxxxxxxxx
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
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
--
2.39.1
