Commit eb03aa00 authored Oct 07, 2016 by Gerald Schaefer Committed by Linus Torvalds Oct 07, 2016

mm/hugetlb: improve locking in dissolve_free_huge_pages()

For every pfn aligned to minimum_order, dissolve_free_huge_pages() will
call dissolve_free_huge_page() which takes the hugetlb spinlock, even if
the page is not huge at all or a hugepage that is in-use.

Improve this by doing the PageHuge() and page_count() checks already in
dissolve_free_huge_pages() before calling dissolve_free_huge_page().  In
dissolve_free_huge_page(), when holding the spinlock, those checks need
to be revalidated.

Link: http://lkml.kernel.org/r/20160926172811.94033-4-gerald.schaefer@de.ibm.com


Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Rui Teng <rui.teng@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 082d5b6b

mm/hugetlb.c

+9 −3

Original line number	Original line	Diff line number	Diff line
	@@ -1476,14 +1476,20 @@ static int dissolve_free_huge_page(struct page *page)
	int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)		int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
	{		{
	unsigned long pfn;		unsigned long pfn;
			struct page *page;
	int rc = 0;		int rc = 0;

	if (!hugepages_supported())		if (!hugepages_supported())
	return rc;		return rc;

	for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order)		for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order) {
	if (rc = dissolve_free_huge_page(pfn_to_page(pfn)))		page = pfn_to_page(pfn);
			if (PageHuge(page) && !page_count(page)) {
			rc = dissolve_free_huge_page(page);
			if (rc)
	break;		break;
			}
			}

	return rc;		return rc;
	}		}