The patch titled
Subject: mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry
has been added to the -mm mm-unstable branch. Its filename is
mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Subject: mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry
Date: Thu, 14 Jul 2022 13:24:14 +0900
follow_pud_mask() does not support non-present pud entry now. As long as
I tested on x86_64 server, follow_pud_mask() still simply returns
no_page_table() for non-present_pud_entry() due to pud_bad(), so no severe
user-visible effect should happen. But generally we should call
follow_huge_pud() for non-present pud entry for 1GB hugetlb page.
Update pud_huge() and follow_huge_pud() to handle non-present pud entries.
The changes are similar to previous works for pud entries commit
e66f17ff7177 ("mm/hugetlb: take page table lock in follow_huge_pmd()") and
commit cbef8478bee5 ("mm/hugetlb: pmd_huge() returns true for non-present
hugepage").
Link: https://lkml.kernel.org/r/20220714042420.1847125-3-naoya.horiguchi@xxxxxxxxx
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: kernel test robot <lkp@xxxxxxxxx>
Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/hugetlbpage.c | 8 +++++++-
mm/hugetlb.c | 32 ++++++++++++++++++++++++++++++--
2 files changed, 37 insertions(+), 3 deletions(-)
--- a/arch/x86/mm/hugetlbpage.c~mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry
+++ a/arch/x86/mm/hugetlbpage.c
@@ -30,9 +30,15 @@ int pmd_huge(pmd_t pmd)
(pmd_val(pmd) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;
}
+/*
+ * pud_huge() returns 1 if @pud is hugetlb related entry, that is normal
+ * hugetlb entry or non-present (migration or hwpoisoned) hugetlb entry.
+ * Otherwise, returns 0.
+ */
int pud_huge(pud_t pud)
{
- return !!(pud_val(pud) & _PAGE_PSE);
+ return !pud_none(pud) &&
+ (pud_val(pud) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;
}
#ifdef CONFIG_HUGETLB_PAGE
--- a/mm/hugetlb.c~mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry
+++ a/mm/hugetlb.c
@@ -6979,10 +6979,38 @@ struct page * __weak
follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int flags)
{
- if (flags & (FOLL_GET | FOLL_PIN))
+ struct page *page = NULL;
+ spinlock_t *ptl;
+ pte_t pte;
+
+ if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
- return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
+retry:
+ ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud);
+ if (!pud_huge(*pud))
+ goto out;
+ pte = huge_ptep_get((pte_t *)pud);
+ if (pte_present(pte)) {
+ page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
+ if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
+ page = NULL;
+ goto out;
+ }
+ } else {
+ if (is_hugetlb_entry_migration(pte)) {
+ spin_unlock(ptl);
+ __migration_entry_wait(mm, (pte_t *)pud, ptl);
+ goto retry;
+ }
+ /*
+ * hwpoisoned entry is treated as no_page_table in
+ * follow_page_mask().
+ */
+ }
+out:
+ spin_unlock(ptl);
+ return page;
}
struct page * __weak
_
Patches currently in -mm which might be from naoya.horiguchi@xxxxxxx are
mm-hugetlb-separate-path-for-hwpoison-entry-in-copy_hugetlb_page_range.patch
mm-hugetlb-check-gigantic_page_runtime_supported-in-return_unused_surplus_pages.patch
mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry.patch
mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages.patch
mm-hwpoison-make-unpoison-aware-of-raw-error-info-in-hwpoisoned-hugepage.patch
mm-hwpoison-set-pg_hwpoison-for-busy-hugetlb-pages.patch
mm-hwpoison-make-__page_handle_poison-returns-int.patch
mm-hwpoison-skip-raw-hwpoison-page-in-freeing-1gb-hugepage.patch
mm-hwpoison-enable-memory-error-handling-on-1gb-hugepage.patch
