[064/131] khugepaged: drain LRU add pagevec after swapin

Commit Message

Andrew Morton June 3, 2020, 11 p.m. UTC

From: "Kirill A. Shutemov" <[e-mail]>
Subject: khugepaged: drain LRU add pagevec after swapin

collapse_huge_page() tries to swap in pages that are part of the PMD
range.  Just swapped in page goes though LRU add cache.  The cache gets
extra reference on the page.

The extra reference can lead to the collapse fail: the following
__collapse_huge_page_isolate() would check refcount and abort collapse
seeing unexpected refcount.

The fix is to drain local LRU add cache in
__collapse_huge_page_swapin() if we successfully swapped in any pages.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kirill A. Shutemov <[e-mail]>
Reviewed-by: William Kucharski <[e-mail]>
Reviewed-by: Zi Yan <[e-mail]>
Tested-by: Zi Yan <[e-mail]>
Acked-by: Yang Shi <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: John Hubbard <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Ralph Campbell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/khugepaged.c |    5 +++++
 1 file changed, 5 insertions(+)

Patch

--- a/mm/khugepaged.c~khugepaged-drain-lru-add-pagevec-after-swapin
+++ a/mm/khugepaged.c
@@ -931,6 +931,11 @@  static bool __collapse_huge_page_swapin(
 	}
 	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;
 }