The patch titled
Subject: mm: hugetlb: proc: check for hugetlb shared PMD in /proc/PID/smaps
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-hugetlb-proc-check-for-hugetlb-shared-pmd-in-proc-pid-smaps.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-proc-check-for-hugetlb-shared-pmd-in-proc-pid-smaps.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: mm: hugetlb: proc: check for hugetlb shared PMD in /proc/PID/smaps
Date: Thu, 26 Jan 2023 14:27:20 -0800
Patch series "Fixes for hugetlb mapcount at most 1 for shared PMDs".
This issue of mapcount in hugetlb pages referenced by shared PMDs was
discussed in [1]. The following two patches address user visible behavior
caused by this issue.
[1] https://lore.kernel.org/linux-mm/Y9BF+OCdWnCSilEu@monkey/
This patch (of 2):
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.
Link: https://lkml.kernel.org/r/20230126222721.222195-2-mike.kravetz@xxxxxxxxxx
Fixes: 25ee01a2fca0 ("mm: hugetlb: proc: add hugetlb-related fields to /proc/PID/smaps")
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: James Houghton <jthoughton@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 10 ++++++++--
include/linux/hugetlb.h | 12 ++++++++++++
2 files changed, 20 insertions(+), 2 deletions(-)
--- a/fs/proc/task_mmu.c~mm-hugetlb-proc-check-for-hugetlb-shared-pmd-in-proc-pid-smaps
+++ a/fs/proc/task_mmu.c
@@ -749,8 +749,14 @@ static int smaps_hugetlb_range(pte_t *pt
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;
}
--- a/include/linux/hugetlb.h~mm-hugetlb-proc-check-for-hugetlb-shared-pmd-in-proc-pid-smaps
+++ a/include/linux/hugetlb.h
@@ -1187,6 +1187,18 @@ static inline __init void hugetlb_cma_re
}
#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
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
mm-hugetlb-proc-check-for-hugetlb-shared-pmd-in-proc-pid-smaps.patch
migrate-hugetlb-check-for-hugetlb-shared-pmd-in-node-migration.patch
