The patch titled
Subject: khugepaged: reuse the smp_wmb() inside __SetPageUptodate()
has been added to the -mm tree. Its filename is
khugepaged-reuse-the-smp_wmb-inside-__setpageuptodate.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/khugepaged-reuse-the-smp_wmb-inside-__setpageuptodate.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/khugepaged-reuse-the-smp_wmb-inside-__setpageuptodate.patch
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------------------------------------------------------
From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: khugepaged: reuse the smp_wmb() inside __SetPageUptodate()
smp_wmb() is needed to avoid the copy_huge_page writes to become visible
after the set_pmd_at() write here. But we can reuse the smp_wmb() inside
__SetPageUptodate() to remove this redundant one.
Link: https://lkml.kernel.org/r/20210306032947.35921-3-linmiaohe@xxxxxxxxxx
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
--- a/mm/khugepaged.c~khugepaged-reuse-the-smp_wmb-inside-__setpageuptodate
+++ a/mm/khugepaged.c
@@ -1183,19 +1183,18 @@ static void collapse_huge_page(struct mm
__collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl,
&compound_pagelist);
pte_unmap(pte);
+ /*
+ * spin_lock() below is not the equivalent of smp_wmb(), but
+ * the smp_wmb() inside __SetPageUptodate() can be reused to
+ * avoid the copy_huge_page writes to become visible after
+ * the set_pmd_at() write.
+ */
__SetPageUptodate(new_page);
pgtable = pmd_pgtable(_pmd);
_pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
- /*
- * spin_lock() below is not the equivalent of smp_wmb(), so
- * this is needed to avoid the copy_huge_page writes to become
- * visible after the set_pmd_at() write.
- */
- smp_wmb();
-
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
page_add_new_anon_rmap(new_page, vma, address, true);
_
Patches currently in -mm which might be from linmiaohe@xxxxxxxxxx are
hugetlb_cgroup-fix-imbalanced-css_get-and-css_put-pair-for-shared-mappings.patch
mm-hugetlb-remove-redundant-reservation-check-condition-in-alloc_huge_page.patch
mm-hugetlb-use-some-helper-functions-to-cleanup-code.patch
mm-hugetlb-optimize-the-surplus-state-transfer-code-in-move_hugetlb_state.patch
hugetlb_cgroup-remove-unnecessary-vm_bug_on_page-in-hugetlb_cgroup_migrate.patch
mm-hugetlb-simplify-the-code-when-alloc_huge_page-failed-in-hugetlb_no_page.patch
mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch
khugepaged-remove-unneeded-return-value-of-khugepaged_collapse_pte_mapped_thps.patch
khugepaged-reuse-the-smp_wmb-inside-__setpageuptodate.patch
khugepaged-use-helper-khugepaged_test_exit-in-__khugepaged_enter.patch
khugepaged-fix-wrong-result-value-for-trace_mm_collapse_huge_page_isolate.patch
