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

From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: akpm@linux-foundation.org, Andrea Arcangeli <aarcange@redhat.com>
Cc: Zi Yan <ziy@nvidia.com>, Yang Shi <yang.shi@linux.alibaba.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCHv2 4/8] khugepaged: Drain LRU add pagevec after swapin
Date: Fri,  3 Apr 2020 14:29:24 +0300	[thread overview]
Message-ID: <20200403112928.19742-5-kirill.shutemov@linux.intel.com> (raw)
In-Reply-To: <20200403112928.19742-1-kirill.shutemov@linux.intel.com>

__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@linux.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

