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From:   "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To:     akpm@linux-foundation.org, Andrea Arcangeli <aarcange@redhat.com>
Cc:     Zi Yan <ziy@nvidia.com>, Yang Shi <yang.shi@linux.alibaba.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        William Kucharski <william.kucharski@oracle.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCHv3, RESEND 4/8] khugepaged: Drain LRU add pagevec after swapin
Date:   Mon, 13 Apr 2020 15:52:16 +0300
Message-Id: <20200413125220.663-5-kirill.shutemov@linux.intel.com>
In-Reply-To: <20200413125220.663-1-kirill.shutemov@linux.intel.com>
References: <20200413125220.663-1-kirill.shutemov@linux.intel.com>
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__collapse_huge_page_isolate() may fail due to extra pin in the LRU add
pagevec. It's pretty common for swapin case: we swap in pages just to
fail due to the extra pin.

Drain LRU add pagevec on successful swapin.

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

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index ee66c140c2d6..e3e41c2768d8 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -934,6 +934,11 @@ 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