From: Miaohe Lin <linmiaohe@huawei.com>
To: <akpm@linux-foundation.org>
Cc: <riel@redhat.com>, <kirill.shutemov@linux.intel.com>,
<ebru.akagunduz@gmail.com>, <dan.carpenter@oracle.com>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<linmiaohe@huawei.com>
Subject: [PATCH 2/5] khugepaged: reuse the smp_wmb() inside __SetPageUptodate()
Date: Thu, 4 Mar 2021 07:30:10 -0500 [thread overview]
Message-ID: <20210304123013.23560-3-linmiaohe@huawei.com> (raw)
In-Reply-To: <20210304123013.23560-1-linmiaohe@huawei.com>
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.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/khugepaged.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index d43812c5ce16..287e7ecf978c 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1183,19 +1183,18 @@ static void collapse_huge_page(struct mm_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);
--
2.19.1
next prev parent reply other threads:[~2021-03-04 12:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-04 12:30 [PATCH 0/5] Cleanup and fixup for khugepaged Miaohe Lin
2021-03-04 12:30 ` [PATCH 1/5] khugepaged: remove unneeded return value of khugepaged_collapse_pte_mapped_thps() Miaohe Lin
2021-03-04 12:30 ` Miaohe Lin [this message]
2021-03-04 12:30 ` [PATCH 3/5] khugepaged: use helper khugepaged_test_exit() in __khugepaged_enter() Miaohe Lin
2021-03-04 12:30 ` [PATCH 4/5] khugepaged: remove unnecessary mem_cgroup_uncharge() in collapse_[file|huge_page] Miaohe Lin
2021-03-05 17:38 ` Kirill A. Shutemov
2021-03-06 3:18 ` Miaohe Lin
2021-03-04 12:30 ` [PATCH 5/5] khugepaged: fix wrong result value for trace_mm_collapse_huge_page_isolate() Miaohe Lin
2021-03-05 17:40 ` [PATCH 0/5] Cleanup and fixup for khugepaged Kirill A. Shutemov
2021-03-06 2:44 ` Miaohe Lin
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