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Commit 79f4b7bf authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

badpage: simplify page_alloc flag check+clear 



Simplify the PAGE_FLAGS checking and clearing when freeing and allocating
a page: check the same flags as before when freeing, clear ALL the flags
(unless PageReserved) when freeing, check ALL flags off when allocating.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0f64415d

include/linux/page-flags.h

+8 −17
Original line number Diff line number Diff line
@@ -373,31 +373,22 @@ static inline void __ClearPageTail(struct page *page) 
#define __PG_MLOCKED		0

#endif



#define PAGE_FLAGS	(1 << PG_lru   | 1 << PG_private   | 1 << PG_locked | \

			 1 << PG_buddy | 1 << PG_writeback | \

			 1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active | \

			 __PG_UNEVICTABLE | __PG_MLOCKED)



/*

 * Flags checked in bad_page().  Pages on the free list should not have

 * these flags set.  It they are, there is a problem.

 */

#define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | \

		1 << PG_reclaim | 1 << PG_dirty | 1 << PG_swapbacked)



/*

 * Flags checked when a page is freed.  Pages being freed should not have

 * these flags set.  It they are, there is a problem.

 */

#define PAGE_FLAGS_CHECK_AT_FREE (PAGE_FLAGS | 1 << PG_reserved)

#define PAGE_FLAGS_CHECK_AT_FREE \

	(1 << PG_lru   | 1 << PG_private   | 1 << PG_locked | \

	 1 << PG_buddy | 1 << PG_writeback | 1 << PG_reserved | \

	 1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active | \

	 __PG_UNEVICTABLE | __PG_MLOCKED)



/*

 * Flags checked when a page is prepped for return by the page allocator.

 * Pages being prepped should not have these flags set.  It they are, there

 * is a problem.

 * Pages being prepped should not have any flags set.  It they are set,

 * there has been a kernel bug or struct page corruption.

 */

#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | \

		1 << PG_reserved | 1 << PG_dirty | 1 << PG_swapbacked)

#define PAGE_FLAGS_CHECK_AT_PREP	((1 << NR_PAGEFLAGS) - 1)



#endif /* !__GENERATING_BOUNDS_H */

#endif	/* PAGE_FLAGS_H */

mm/page_alloc.c

+6 −13
Original line number Diff line number Diff line
@@ -231,7 +231,6 @@ static void bad_page(struct page *page) 
	printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n"

		KERN_EMERG "Backtrace:\n");

	dump_stack();

	page->flags &= ~PAGE_FLAGS_CLEAR_WHEN_BAD;

	set_page_count(page, 0);

	reset_page_mapcount(page);

	page->mapping = NULL;
@@ -468,16 +467,16 @@ static inline int free_pages_check(struct page *page) 
		(page_count(page) != 0)  |

		(page->flags & PAGE_FLAGS_CHECK_AT_FREE)))

		bad_page(page);

	if (PageDirty(page))

		__ClearPageDirty(page);

	if (PageSwapBacked(page))

		__ClearPageSwapBacked(page);

	/*

	 * For now, we report if PG_reserved was found set, but do not

	 * clear it, and do not free the page.  But we shall soon need

	 * to do more, for when the ZERO_PAGE count wraps negative.

	 */

	return PageReserved(page);

	if (PageReserved(page))

		return 1;

	if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)

		page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;

	return 0;

}



/*
@@ -621,13 +620,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags) 
	if (PageReserved(page))

		return 1;



	page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |

			1 << PG_referenced | 1 << PG_arch_1 |

			1 << PG_owner_priv_1 | 1 << PG_mappedtodisk

#ifdef CONFIG_UNEVICTABLE_LRU

			| 1 << PG_mlocked

#endif

			);

	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;

	set_page_private(page, 0);

	set_page_refcounted(page);