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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@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Miaohe Lin 2021-05-04 18:33:40 -07:00 committed by Linus Torvalds
parent 0edf61e5ee
commit 588d01f918
1 changed files with 6 additions and 7 deletions
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13
mm/khugepaged.c
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@ -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);