linux-kernel - [PATCH 3/4] thp: fix MADV_DONTNEED vs. MADV

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Date:   Thu,  2 Mar 2017 18:10:33 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Minchan Kim <minchan@...nel.org>
Subject: [PATCH 3/4] thp: fix MADV_DONTNEED vs. MADV_FREE race

Basically the same race as with numa balancing in change_huge_pmd(), but
a bit simpler to mitigate: we don't need to preserve dirty/young flags
here due to MADV_FREE functionality.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Minchan Kim <minchan@...nel.org>
---
 mm/huge_memory.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index bb2b3646bd78..324217c31ec9 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1566,8 +1566,6 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		deactivate_page(page);
 
 	if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
-		orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
-			tlb->fullmm);
 		orig_pmd = pmd_mkold(orig_pmd);
 		orig_pmd = pmd_mkclean(orig_pmd);
 
-- 
2.11.0