include/linux/page-flags.h - kernel/msm-4.19 - Gitiles

 /*
  * Macros for manipulating and testing page->flags
  */

 #ifndef PAGE_FLAGS_H
 #define PAGE_FLAGS_H

 #include <linux/types.h>
 #include <linux/mm_types.h>

 /*
  * Various page->flags bits:
  *
  * PG_reserved is set for special pages, which can never be swapped out. Some
  * of them might not even exist (eg empty_bad_page)...
  *
  * The PG_private bitflag is set on pagecache pages if they contain filesystem
  * specific data (which is normally at page->private). It can be used by
  * private allocations for its own usage.
  *
  * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
  * and cleared when writeback _starts_ or when read _completes_. PG_writeback
  * is set before writeback starts and cleared when it finishes.
  *
  * PG_locked also pins a page in pagecache, and blocks truncation of the file
  * while it is held.
  *
  * page_waitqueue(page) is a wait queue of all tasks waiting for the page
  * to become unlocked.
  *
  * PG_uptodate tells whether the page's contents is valid.  When a read
  * completes, the page becomes uptodate, unless a disk I/O error happened.
  *
  * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
  * file-backed pagecache (see mm/vmscan.c).
  *
  * PG_error is set to indicate that an I/O error occurred on this page.
  *
  * PG_arch_1 is an architecture specific page state bit.  The generic code
  * guarantees that this bit is cleared for a page when it first is entered into
  * the page cache.
  *
  * PG_highmem pages are not permanently mapped into the kernel virtual address
  * space, they need to be kmapped separately for doing IO on the pages.  The
  * struct page (these bits with information) are always mapped into kernel
  * address space...
  *
  * PG_buddy is set to indicate that the page is free and in the buddy system
  * (see mm/page_alloc.c).
  *
  */

 /*
  * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
  * locked- and dirty-page accounting.
  *
  * The page flags field is split into two parts, the main flags area
  * which extends from the low bits upwards, and the fields area which
  * extends from the high bits downwards.
  *
  *  | FIELD | ... | FLAGS |
  *  N-1     ^             0
  *          (N-FLAGS_RESERVED)
  *
  * The fields area is reserved for fields mapping zone, node and SPARSEMEM
  * section.  The boundry between these two areas is defined by
  * FLAGS_RESERVED which defines the width of the fields section
  * (see linux/mmzone.h).  New flags must _not_ overlap with this area.
  */
 #define PG_locked	 	 0	/* Page is locked. Don't touch. */
 #define PG_error		 1
 #define PG_referenced		 2
 #define PG_uptodate		 3

 #define PG_dirty	 	 4
 #define PG_lru			 5
 #define PG_active		 6
 #define PG_slab			 7	/* slab debug (Suparna wants this) */

 #define PG_owner_priv_1		 8	/* Owner use. If pagecache, fs may use*/
 #define PG_arch_1		 9
 #define PG_reserved		10
 #define PG_private		11	/* If pagecache, has fs-private data */

 #define PG_writeback		12	/* Page is under writeback */
 #define PG_compound		14	/* Part of a compound page */
 #define PG_swapcache		15	/* Swap page: swp_entry_t in private */

 #define PG_mappedtodisk		16	/* Has blocks allocated on-disk */
 #define PG_reclaim		17	/* To be reclaimed asap */
 #define PG_buddy		19	/* Page is free, on buddy lists */

 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
 #define PG_readahead		PG_reclaim /* Reminder to do async read-ahead */

 /* PG_owner_priv_1 users should have descriptive aliases */
 #define PG_checked		PG_owner_priv_1 /* Used by some filesystems */
 #define PG_pinned		PG_owner_priv_1	/* Xen pinned pagetable */

 #if (BITS_PER_LONG > 32)
 /*
  * 64-bit-only flags build down from bit 31
  *
  * 32 bit  -------------------------------| FIELDS |       FLAGS         |
  * 64 bit  |           FIELDS             | ??????         FLAGS         |
  *         63                            32                              0
  */
 #define PG_uncached		31	/* Page has been mapped as uncached */
 #endif

 /*
  * Manipulation of page state flags
  */
 #define PageLocked(page)		\
 		test_bit(PG_locked, &(page)->flags)
 #define SetPageLocked(page)		\
 		set_bit(PG_locked, &(page)->flags)
 #define TestSetPageLocked(page)		\
 		test_and_set_bit(PG_locked, &(page)->flags)
 #define ClearPageLocked(page)		\
 		clear_bit(PG_locked, &(page)->flags)
 #define TestClearPageLocked(page)	\
 		test_and_clear_bit(PG_locked, &(page)->flags)

 #define PageError(page)		test_bit(PG_error, &(page)->flags)
 #define SetPageError(page)	set_bit(PG_error, &(page)->flags)
 #define ClearPageError(page)	clear_bit(PG_error, &(page)->flags)

 #define PageReferenced(page)	test_bit(PG_referenced, &(page)->flags)
 #define SetPageReferenced(page)	set_bit(PG_referenced, &(page)->flags)
 #define ClearPageReferenced(page)	clear_bit(PG_referenced, &(page)->flags)
 #define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)

 #define PageUptodate(page)	test_bit(PG_uptodate, &(page)->flags)
 #ifdef CONFIG_S390
 static inline void SetPageUptodate(struct page *page)
 {
 	if (!test_and_set_bit(PG_uptodate, &page->flags))
 		page_clear_dirty(page);
 }
 #else
 #define SetPageUptodate(page)	set_bit(PG_uptodate, &(page)->flags)
 #endif
 #define ClearPageUptodate(page)	clear_bit(PG_uptodate, &(page)->flags)

 #define PageDirty(page)		test_bit(PG_dirty, &(page)->flags)
 #define SetPageDirty(page)	set_bit(PG_dirty, &(page)->flags)
 #define TestSetPageDirty(page)	test_and_set_bit(PG_dirty, &(page)->flags)
 #define ClearPageDirty(page)	clear_bit(PG_dirty, &(page)->flags)
 #define __ClearPageDirty(page)	__clear_bit(PG_dirty, &(page)->flags)
 #define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)

 #define PageLRU(page)		test_bit(PG_lru, &(page)->flags)
 #define SetPageLRU(page)	set_bit(PG_lru, &(page)->flags)
 #define ClearPageLRU(page)	clear_bit(PG_lru, &(page)->flags)
 #define __ClearPageLRU(page)	__clear_bit(PG_lru, &(page)->flags)

 #define PageActive(page)	test_bit(PG_active, &(page)->flags)
 #define SetPageActive(page)	set_bit(PG_active, &(page)->flags)
 #define ClearPageActive(page)	clear_bit(PG_active, &(page)->flags)
 #define __ClearPageActive(page)	__clear_bit(PG_active, &(page)->flags)

 #define PageSlab(page)		test_bit(PG_slab, &(page)->flags)
 #define __SetPageSlab(page)	__set_bit(PG_slab, &(page)->flags)
 #define __ClearPageSlab(page)	__clear_bit(PG_slab, &(page)->flags)

 #ifdef CONFIG_HIGHMEM
 #define PageHighMem(page)	is_highmem(page_zone(page))
 #else
 #define PageHighMem(page)	0 /* needed to optimize away at compile time */
 #endif

 #define PageChecked(page)	test_bit(PG_checked, &(page)->flags)
 #define SetPageChecked(page)	set_bit(PG_checked, &(page)->flags)
 #define ClearPageChecked(page)	clear_bit(PG_checked, &(page)->flags)

 #define PagePinned(page)	test_bit(PG_pinned, &(page)->flags)
 #define SetPagePinned(page)	set_bit(PG_pinned, &(page)->flags)
 #define ClearPagePinned(page)	clear_bit(PG_pinned, &(page)->flags)

 #define PageReserved(page)	test_bit(PG_reserved, &(page)->flags)
 #define SetPageReserved(page)	set_bit(PG_reserved, &(page)->flags)
 #define ClearPageReserved(page)	clear_bit(PG_reserved, &(page)->flags)
 #define __ClearPageReserved(page)	__clear_bit(PG_reserved, &(page)->flags)

 #define SetPagePrivate(page)	set_bit(PG_private, &(page)->flags)
 #define ClearPagePrivate(page)	clear_bit(PG_private, &(page)->flags)
 #define PagePrivate(page)	test_bit(PG_private, &(page)->flags)
 #define __SetPagePrivate(page)  __set_bit(PG_private, &(page)->flags)
 #define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)

 #define PageWriteback(page)	test_bit(PG_writeback, &(page)->flags)
 #define SetPageWriteback(page)						\
 	do {								\
 		if (!test_and_set_bit(PG_writeback,			\
 				&(page)->flags))			\
 			inc_zone_page_state(page, NR_WRITEBACK);	\
 	} while (0)
 #define TestSetPageWriteback(page)					\
 	({								\
 		int ret;						\
 		ret = test_and_set_bit(PG_writeback,			\
 					&(page)->flags);		\
 		if (!ret)						\
 			inc_zone_page_state(page, NR_WRITEBACK);	\
 		ret;							\
 	})
 #define ClearPageWriteback(page)					\
 	do {								\
 		if (test_and_clear_bit(PG_writeback,			\
 				&(page)->flags))			\
 			dec_zone_page_state(page, NR_WRITEBACK);	\
 	} while (0)
 #define TestClearPageWriteback(page)					\
 	({								\
 		int ret;						\
 		ret = test_and_clear_bit(PG_writeback,			\
 				&(page)->flags);			\
 		if (ret)						\
 			dec_zone_page_state(page, NR_WRITEBACK);	\
 		ret;							\
 	})

 #define PageBuddy(page)		test_bit(PG_buddy, &(page)->flags)
 #define __SetPageBuddy(page)	__set_bit(PG_buddy, &(page)->flags)
 #define __ClearPageBuddy(page)	__clear_bit(PG_buddy, &(page)->flags)

 #define PageMappedToDisk(page)	test_bit(PG_mappedtodisk, &(page)->flags)
 #define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
 #define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)

 #define PageReadahead(page)	test_bit(PG_readahead, &(page)->flags)
 #define SetPageReadahead(page)	set_bit(PG_readahead, &(page)->flags)
 #define ClearPageReadahead(page) clear_bit(PG_readahead, &(page)->flags)

 #define PageReclaim(page)	test_bit(PG_reclaim, &(page)->flags)
 #define SetPageReclaim(page)	set_bit(PG_reclaim, &(page)->flags)
 #define ClearPageReclaim(page)	clear_bit(PG_reclaim, &(page)->flags)
 #define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)

 #define PageCompound(page)	test_bit(PG_compound, &(page)->flags)
 #define __SetPageCompound(page)	__set_bit(PG_compound, &(page)->flags)
 #define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)

 /*
  * PG_reclaim is used in combination with PG_compound to mark the
  * head and tail of a compound page
  *
  * PG_compound & PG_reclaim	=> Tail page
  * PG_compound & ~PG_reclaim	=> Head page
  */

 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))

 #define PageTail(page)	((page->flags & PG_head_tail_mask) \
 				== PG_head_tail_mask)

 static inline void __SetPageTail(struct page *page)
 {
 	page->flags |= PG_head_tail_mask;
 }

 static inline void __ClearPageTail(struct page *page)
 {
 	page->flags &= ~PG_head_tail_mask;
 }

 #define PageHead(page)	((page->flags & PG_head_tail_mask) \
 				== (1L << PG_compound))
 #define __SetPageHead(page)	__SetPageCompound(page)
 #define __ClearPageHead(page)	__ClearPageCompound(page)

 #ifdef CONFIG_SWAP
 #define PageSwapCache(page)	test_bit(PG_swapcache, &(page)->flags)
 #define SetPageSwapCache(page)	set_bit(PG_swapcache, &(page)->flags)
 #define ClearPageSwapCache(page) clear_bit(PG_swapcache, &(page)->flags)
 #else
 #define PageSwapCache(page)	0
 #endif

 #define PageUncached(page)	test_bit(PG_uncached, &(page)->flags)
 #define SetPageUncached(page)	set_bit(PG_uncached, &(page)->flags)
 #define ClearPageUncached(page)	clear_bit(PG_uncached, &(page)->flags)

 struct page;	/* forward declaration */

 extern void cancel_dirty_page(struct page *page, unsigned int account_size);

 int test_clear_page_writeback(struct page *page);
 int test_set_page_writeback(struct page *page);

 static inline void set_page_writeback(struct page *page)
 {
 	test_set_page_writeback(page);
 }

 #endif	/* PAGE_FLAGS_H */
	/*
	* Macros for manipulating and testing page->flags
	*/

	#ifndef PAGE_FLAGS_H
	#define PAGE_FLAGS_H

	#include <linux/types.h>
	#include <linux/mm_types.h>

	/*
	* Various page->flags bits:
	*
	* PG_reserved is set for special pages, which can never be swapped out. Some
	* of them might not even exist (eg empty_bad_page)...
	*
	* The PG_private bitflag is set on pagecache pages if they contain filesystem
	* specific data (which is normally at page->private). It can be used by
	* private allocations for its own usage.
	*
	* During initiation of disk I/O, PG_locked is set. This bit is set before I/O
	* and cleared when writeback _starts_ or when read _completes_. PG_writeback
	* is set before writeback starts and cleared when it finishes.
	*
	* PG_locked also pins a page in pagecache, and blocks truncation of the file
	* while it is held.
	*
	* page_waitqueue(page) is a wait queue of all tasks waiting for the page
	* to become unlocked.
	*
	* PG_uptodate tells whether the page's contents is valid. When a read
	* completes, the page becomes uptodate, unless a disk I/O error happened.
	*
	* PG_referenced, PG_reclaim are used for page reclaim for anonymous and
	* file-backed pagecache (see mm/vmscan.c).
	*
	* PG_error is set to indicate that an I/O error occurred on this page.
	*
	* PG_arch_1 is an architecture specific page state bit. The generic code
	* guarantees that this bit is cleared for a page when it first is entered into
	* the page cache.
	*
	* PG_highmem pages are not permanently mapped into the kernel virtual address
	* space, they need to be kmapped separately for doing IO on the pages. The
	* struct page (these bits with information) are always mapped into kernel
	* address space...
	*
	* PG_buddy is set to indicate that the page is free and in the buddy system
	* (see mm/page_alloc.c).
	*
	*/

	/*
	* Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
	* locked- and dirty-page accounting.
	*
	* The page flags field is split into two parts, the main flags area
	* which extends from the low bits upwards, and the fields area which
	* extends from the high bits downwards.
	*
	* \| FIELD \| ... \| FLAGS \|
	* N-1 ^ 0
	* (N-FLAGS_RESERVED)
	*
	* The fields area is reserved for fields mapping zone, node and SPARSEMEM
	* section. The boundry between these two areas is defined by
	* FLAGS_RESERVED which defines the width of the fields section
	* (see linux/mmzone.h). New flags must _not_ overlap with this area.
	*/
	#define PG_locked 0 /* Page is locked. Don't touch. */
	#define PG_error 1
	#define PG_referenced 2
	#define PG_uptodate 3

	#define PG_dirty 4
	#define PG_lru 5
	#define PG_active 6
	#define PG_slab 7 /* slab debug (Suparna wants this) */

	#define PG_owner_priv_1 8 /* Owner use. If pagecache, fs may use*/
	#define PG_arch_1 9
	#define PG_reserved 10
	#define PG_private 11 /* If pagecache, has fs-private data */

	#define PG_writeback 12 /* Page is under writeback */
	#define PG_compound 14 /* Part of a compound page */
	#define PG_swapcache 15 /* Swap page: swp_entry_t in private */

	#define PG_mappedtodisk 16 /* Has blocks allocated on-disk */
	#define PG_reclaim 17 /* To be reclaimed asap */
	#define PG_buddy 19 /* Page is free, on buddy lists */

	/* PG_readahead is only used for file reads; PG_reclaim is only for writes */
	#define PG_readahead PG_reclaim /* Reminder to do async read-ahead */

	/* PG_owner_priv_1 users should have descriptive aliases */
	#define PG_checked PG_owner_priv_1 /* Used by some filesystems */
	#define PG_pinned PG_owner_priv_1 /* Xen pinned pagetable */

	#if (BITS_PER_LONG > 32)
	/*
	* 64-bit-only flags build down from bit 31
	*
	* 32 bit -------------------------------\| FIELDS \| FLAGS \|
	* 64 bit \| FIELDS \| ?????? FLAGS \|
	* 63 32 0
	*/
	#define PG_uncached 31 /* Page has been mapped as uncached */
	#endif

	/*
	* Manipulation of page state flags
	*/
	#define PageLocked(page) \
	test_bit(PG_locked, &(page)->flags)
	#define SetPageLocked(page) \
	set_bit(PG_locked, &(page)->flags)
	#define TestSetPageLocked(page) \
	test_and_set_bit(PG_locked, &(page)->flags)
	#define ClearPageLocked(page) \
	clear_bit(PG_locked, &(page)->flags)
	#define TestClearPageLocked(page) \
	test_and_clear_bit(PG_locked, &(page)->flags)

	#define PageError(page) test_bit(PG_error, &(page)->flags)
	#define SetPageError(page) set_bit(PG_error, &(page)->flags)
	#define ClearPageError(page) clear_bit(PG_error, &(page)->flags)

	#define PageReferenced(page) test_bit(PG_referenced, &(page)->flags)
	#define SetPageReferenced(page) set_bit(PG_referenced, &(page)->flags)
	#define ClearPageReferenced(page) clear_bit(PG_referenced, &(page)->flags)
	#define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)

	#define PageUptodate(page) test_bit(PG_uptodate, &(page)->flags)
	#ifdef CONFIG_S390
	static inline void SetPageUptodate(struct page *page)
	{
	if (!test_and_set_bit(PG_uptodate, &page->flags))
	page_clear_dirty(page);
	}
	#else
	#define SetPageUptodate(page) set_bit(PG_uptodate, &(page)->flags)
	#endif
	#define ClearPageUptodate(page) clear_bit(PG_uptodate, &(page)->flags)

	#define PageDirty(page) test_bit(PG_dirty, &(page)->flags)
	#define SetPageDirty(page) set_bit(PG_dirty, &(page)->flags)
	#define TestSetPageDirty(page) test_and_set_bit(PG_dirty, &(page)->flags)
	#define ClearPageDirty(page) clear_bit(PG_dirty, &(page)->flags)
	#define __ClearPageDirty(page) __clear_bit(PG_dirty, &(page)->flags)
	#define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)

	#define PageLRU(page) test_bit(PG_lru, &(page)->flags)
	#define SetPageLRU(page) set_bit(PG_lru, &(page)->flags)
	#define ClearPageLRU(page) clear_bit(PG_lru, &(page)->flags)
	#define __ClearPageLRU(page) __clear_bit(PG_lru, &(page)->flags)

	#define PageActive(page) test_bit(PG_active, &(page)->flags)
	#define SetPageActive(page) set_bit(PG_active, &(page)->flags)
	#define ClearPageActive(page) clear_bit(PG_active, &(page)->flags)
	#define __ClearPageActive(page) __clear_bit(PG_active, &(page)->flags)

	#define PageSlab(page) test_bit(PG_slab, &(page)->flags)
	#define __SetPageSlab(page) __set_bit(PG_slab, &(page)->flags)
	#define __ClearPageSlab(page) __clear_bit(PG_slab, &(page)->flags)

	#ifdef CONFIG_HIGHMEM
	#define PageHighMem(page) is_highmem(page_zone(page))
	#else
	#define PageHighMem(page) 0 /* needed to optimize away at compile time */
	#endif

	#define PageChecked(page) test_bit(PG_checked, &(page)->flags)
	#define SetPageChecked(page) set_bit(PG_checked, &(page)->flags)
	#define ClearPageChecked(page) clear_bit(PG_checked, &(page)->flags)

	#define PagePinned(page) test_bit(PG_pinned, &(page)->flags)
	#define SetPagePinned(page) set_bit(PG_pinned, &(page)->flags)
	#define ClearPagePinned(page) clear_bit(PG_pinned, &(page)->flags)

	#define PageReserved(page) test_bit(PG_reserved, &(page)->flags)
	#define SetPageReserved(page) set_bit(PG_reserved, &(page)->flags)
	#define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
	#define __ClearPageReserved(page) __clear_bit(PG_reserved, &(page)->flags)

	#define SetPagePrivate(page) set_bit(PG_private, &(page)->flags)
	#define ClearPagePrivate(page) clear_bit(PG_private, &(page)->flags)
	#define PagePrivate(page) test_bit(PG_private, &(page)->flags)
	#define __SetPagePrivate(page) __set_bit(PG_private, &(page)->flags)
	#define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)

	#define PageWriteback(page) test_bit(PG_writeback, &(page)->flags)
	#define SetPageWriteback(page) \
	do { \
	if (!test_and_set_bit(PG_writeback, \
	&(page)->flags)) \
	inc_zone_page_state(page, NR_WRITEBACK); \
	} while (0)
	#define TestSetPageWriteback(page) \
	({ \
	int ret; \
	ret = test_and_set_bit(PG_writeback, \
	&(page)->flags); \
	if (!ret) \
	inc_zone_page_state(page, NR_WRITEBACK); \
	ret; \
	})
	#define ClearPageWriteback(page) \
	do { \
	if (test_and_clear_bit(PG_writeback, \
	&(page)->flags)) \
	dec_zone_page_state(page, NR_WRITEBACK); \
	} while (0)
	#define TestClearPageWriteback(page) \
	({ \
	int ret; \
	ret = test_and_clear_bit(PG_writeback, \
	&(page)->flags); \
	if (ret) \
	dec_zone_page_state(page, NR_WRITEBACK); \
	ret; \
	})

	#define PageBuddy(page) test_bit(PG_buddy, &(page)->flags)
	#define __SetPageBuddy(page) __set_bit(PG_buddy, &(page)->flags)
	#define __ClearPageBuddy(page) __clear_bit(PG_buddy, &(page)->flags)

	#define PageMappedToDisk(page) test_bit(PG_mappedtodisk, &(page)->flags)
	#define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
	#define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)

	#define PageReadahead(page) test_bit(PG_readahead, &(page)->flags)
	#define SetPageReadahead(page) set_bit(PG_readahead, &(page)->flags)
	#define ClearPageReadahead(page) clear_bit(PG_readahead, &(page)->flags)

	#define PageReclaim(page) test_bit(PG_reclaim, &(page)->flags)
	#define SetPageReclaim(page) set_bit(PG_reclaim, &(page)->flags)
	#define ClearPageReclaim(page) clear_bit(PG_reclaim, &(page)->flags)
	#define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)

	#define PageCompound(page) test_bit(PG_compound, &(page)->flags)
	#define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
	#define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)

	/*
	* PG_reclaim is used in combination with PG_compound to mark the
	* head and tail of a compound page
	*
	* PG_compound & PG_reclaim => Tail page
	* PG_compound & ~PG_reclaim => Head page
	*/

	#define PG_head_tail_mask ((1L << PG_compound) \| (1L << PG_reclaim))

	#define PageTail(page) ((page->flags & PG_head_tail_mask) \
	== PG_head_tail_mask)

	static inline void __SetPageTail(struct page *page)
	{
	page->flags \|= PG_head_tail_mask;
	}

	static inline void __ClearPageTail(struct page *page)
	{
	page->flags &= ~PG_head_tail_mask;
	}

	#define PageHead(page) ((page->flags & PG_head_tail_mask) \
	== (1L << PG_compound))
	#define __SetPageHead(page) __SetPageCompound(page)
	#define __ClearPageHead(page) __ClearPageCompound(page)

	#ifdef CONFIG_SWAP
	#define PageSwapCache(page) test_bit(PG_swapcache, &(page)->flags)
	#define SetPageSwapCache(page) set_bit(PG_swapcache, &(page)->flags)
	#define ClearPageSwapCache(page) clear_bit(PG_swapcache, &(page)->flags)
	#else
	#define PageSwapCache(page) 0
	#endif

	#define PageUncached(page) test_bit(PG_uncached, &(page)->flags)
	#define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags)
	#define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)

	struct page; /* forward declaration */

	extern void cancel_dirty_page(struct page *page, unsigned int account_size);

	int test_clear_page_writeback(struct page *page);
	int test_set_page_writeback(struct page *page);

	static inline void set_page_writeback(struct page *page)
	{
	test_set_page_writeback(page);
	}

	#endif /* PAGE_FLAGS_H */