Commit 588d01f9 authored by Miaohe Lin's avatar Miaohe Lin Committed by Linus Torvalds
Browse files

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: default avatarMiaohe Lin <linmiaohe@huawei.com>
Acked-by: default avatarKirill 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0edf61e5

mm/khugepaged.c

+6 −7
Original line number Diff line number Diff line
@@ -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);