linux-kernel - [PATCHv2 4/8] khugepaged: Drain LRU add pagevec after swapin

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Date:   Fri,  3 Apr 2020 14:29:24 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     akpm@...ux-foundation.org, Andrea Arcangeli <aarcange@...hat.com>
Cc:     Zi Yan <ziy@...dia.com>, Yang Shi <yang.shi@...ux.alibaba.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv2 4/8] khugepaged: Drain LRU add pagevec after swapin

__collapse_huge_page_isolate() may fail due to extra pin in the LRU add
pagevec. It's petty common for swapin case: we swap in pages just to
fail due to the extra pin.

Drain LRU add pagevec on sucessfull swapin.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/khugepaged.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index fdc10ffde1ca..57ff287caf6b 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -940,6 +940,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
 	}
 	vmf.pte--;
 	pte_unmap(vmf.pte);
+
+	/* Drain LRU add pagevec to remove extra pin on the swapped in pages */
+	if (swapped_in)
+		lru_add_drain();
+
 	trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
 	return true;
 }
-- 
2.26.0