Commit ae2c5d80 authored Jun 03, 2020 by Kirill A. Shutemov Committed by Linus Torvalds Jun 03, 2020

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.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Link: http://lkml.kernel.org/r/20200416160026.16538-5-kirill.shutemov@linux.intel.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a980df33

mm/khugepaged.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -931,6 +931,11 @@ 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;
		}

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