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Commit 81422f29 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

mm: more checks on free_pages_prepare() for tail pages 



Although it was not called, destroy_compound_page() did some potentially
useful checks.  Let's re-introduce them in free_pages_prepare(), where
they can be actually triggered when CONFIG_DEBUG_VM=y.

compound_order() assert is already in free_pages_prepare().  We have few
checks for tail pages left.

Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6e9f0d58

mm/page_alloc.c

+23 −4
Original line number Diff line number Diff line
@@ -764,21 +764,40 @@ static void free_one_page(struct zone *zone, 
	spin_unlock(&zone->lock);

}



static int free_tail_pages_check(struct page *head_page, struct page *page)

{

	if (!IS_ENABLED(CONFIG_DEBUG_VM))

		return 0;

	if (unlikely(!PageTail(page))) {

		bad_page(page, "PageTail not set", 0);

		return 1;

	}

	if (unlikely(page->first_page != head_page)) {

		bad_page(page, "first_page not consistent", 0);

		return 1;

	}

	return 0;

}



static bool free_pages_prepare(struct page *page, unsigned int order)

{

	int i;

	int bad = 0;

	bool compound = PageCompound(page);

	int i, bad = 0;



	VM_BUG_ON_PAGE(PageTail(page), page);

	VM_BUG_ON_PAGE(PageHead(page) && compound_order(page) != order, page);

	VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);



	trace_mm_page_free(page, order);

	kmemcheck_free_shadow(page, order);



	if (PageAnon(page))

		page->mapping = NULL;

	for (i = 0; i < (1 << order); i++)

	bad += free_pages_check(page);

	for (i = 1; i < (1 << order); i++) {

		if (compound)

			bad += free_tail_pages_check(page, page + i);

		bad += free_pages_check(page + i);

	}

	if (bad)

		return false;