[deliverable/linux.git] / include / linux / 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_owner_priv_1 users should have descriptive aliases */
#define PG_checked		PG_owner_priv_1 /* Used by some filesystems */

#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 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 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 */
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Macros for manipulating and testing page->flags
	3	*/
	4
	5	#ifndef PAGE_FLAGS_H
	6	#define PAGE_FLAGS_H
	7
f886ed44	8	#include <linux/types.h>
6d777953	9	#include <linux/mm_types.h>
f886ed44	10
1da177e4 LT	11	/*
	12	* Various page->flags bits:
	13	*
	14	* PG_reserved is set for special pages, which can never be swapped out. Some
	15	* of them might not even exist (eg empty_bad_page)...
	16	*
da6052f7 NP	17	* The PG_private bitflag is set on pagecache pages if they contain filesystem
	18	* specific data (which is normally at page->private). It can be used by
	19	* private allocations for its own usage.
1da177e4	20	*
da6052f7 NP	21	* During initiation of disk I/O, PG_locked is set. This bit is set before I/O
	22	* and cleared when writeback _starts_ or when read _completes_. PG_writeback
	23	* is set before writeback starts and cleared when it finishes.
	24	*
	25	* PG_locked also pins a page in pagecache, and blocks truncation of the file
	26	* while it is held.
	27	*
	28	* page_waitqueue(page) is a wait queue of all tasks waiting for the page
	29	* to become unlocked.
1da177e4 LT	30	*
	31	* PG_uptodate tells whether the page's contents is valid. When a read
	32	* completes, the page becomes uptodate, unless a disk I/O error happened.
	33	*
da6052f7 NP	34	* PG_referenced, PG_reclaim are used for page reclaim for anonymous and
da6052f7 NP	35	* file-backed pagecache (see mm/vmscan.c).
1da177e4 LT	36	*
	37	* PG_error is set to indicate that an I/O error occurred on this page.
	38	*
	39	* PG_arch_1 is an architecture specific page state bit. The generic code
	40	* guarantees that this bit is cleared for a page when it first is entered into
	41	* the page cache.
	42	*
	43	* PG_highmem pages are not permanently mapped into the kernel virtual address
	44	* space, they need to be kmapped separately for doing IO on the pages. The
	45	* struct page (these bits with information) are always mapped into kernel
	46	* address space...
da6052f7 NP	47	*
	48	* PG_buddy is set to indicate that the page is free and in the buddy system
	49	* (see mm/page_alloc.c).
	50	*
1da177e4 LT	51	*/
	52
	53	/*
	54	* Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
91fc8ab3 AW	55	* locked- and dirty-page accounting.
	56	*
	57	* The page flags field is split into two parts, the main flags area
	58	* which extends from the low bits upwards, and the fields area which
	59	* extends from the high bits downwards.
	60	*
	61	* \| FIELD \| ... \| FLAGS \|
	62	* N-1 ^ 0
	63	* (N-FLAGS_RESERVED)
	64	*
	65	* The fields area is reserved for fields mapping zone, node and SPARSEMEM
	66	* section. The boundry between these two areas is defined by
	67	* FLAGS_RESERVED which defines the width of the fields section
	68	* (see linux/mmzone.h). New flags must _not_ overlap with this area.
1da177e4 LT	69	*/
	70	#define PG_locked 0 /* Page is locked. Don't touch. */
	71	#define PG_error 1
	72	#define PG_referenced 2
	73	#define PG_uptodate 3
	74
	75	#define PG_dirty 4
	76	#define PG_lru 5
	77	#define PG_active 6
	78	#define PG_slab 7 /* slab debug (Suparna wants this) */
	79
5409bae0	80	#define PG_owner_priv_1 8 /* Owner use. If pagecache, fs may use*/
cbe37d09 BP	81	#define PG_arch_1 9
cbe37d09 BP	82	#define PG_reserved 10
da6052f7	83	#define PG_private 11 /* If pagecache, has fs-private data */
cbe37d09 BP	84
cbe37d09 BP	85	#define PG_writeback 12 /* Page is under writeback */
cbe37d09 BP	86	#define PG_compound 14 /* Part of a compound page */
	87	#define PG_swapcache 15 /* Swap page: swp_entry_t in private */
	88
	89	#define PG_mappedtodisk 16 /* Has blocks allocated on-disk */
	90	#define PG_reclaim 17 /* To be reclaimed asap */
676165a8 NP	91	#define PG_buddy 19 /* Page is free, on buddy lists */
676165a8 NP	92
5409bae0 NP	93	/* PG_owner_priv_1 users should have descriptive aliases */
5409bae0 NP	94	#define PG_checked PG_owner_priv_1 /* Used by some filesystems */
f886ed44 AM	95
	96	#if (BITS_PER_LONG > 32)
	97	/*
	98	* 64-bit-only flags build down from bit 31
	99	*
	100	* 32 bit -------------------------------\| FIELDS \| FLAGS \|
	101	* 64 bit \| FIELDS \| ?????? FLAGS \|
	102	* 63 32 0
	103	*/
	104	#define PG_uncached 31 /* Page has been mapped as uncached */
	105	#endif
1da177e4	106
1da177e4 LT	107	/*
	108	* Manipulation of page state flags
	109	*/
	110	#define PageLocked(page) \
	111	test_bit(PG_locked, &(page)->flags)
	112	#define SetPageLocked(page) \
	113	set_bit(PG_locked, &(page)->flags)
	114	#define TestSetPageLocked(page) \
	115	test_and_set_bit(PG_locked, &(page)->flags)
	116	#define ClearPageLocked(page) \
	117	clear_bit(PG_locked, &(page)->flags)
	118	#define TestClearPageLocked(page) \
	119	test_and_clear_bit(PG_locked, &(page)->flags)
	120
	121	#define PageError(page) test_bit(PG_error, &(page)->flags)
	122	#define SetPageError(page) set_bit(PG_error, &(page)->flags)
	123	#define ClearPageError(page) clear_bit(PG_error, &(page)->flags)
	124
	125	#define PageReferenced(page) test_bit(PG_referenced, &(page)->flags)
	126	#define SetPageReferenced(page) set_bit(PG_referenced, &(page)->flags)
	127	#define ClearPageReferenced(page) clear_bit(PG_referenced, &(page)->flags)
	128	#define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)
	129
	130	#define PageUptodate(page) test_bit(PG_uptodate, &(page)->flags)
f6ac2354	131	#ifdef CONFIG_S390
2dcea57a HC	132	static inline void SetPageUptodate(struct page *page)
	133	{
	134	if (!test_and_set_bit(PG_uptodate, &page->flags))
6c210482	135	page_clear_dirty(page);
2dcea57a	136	}
f6ac2354	137	#else
1da177e4 LT	138	#define SetPageUptodate(page) set_bit(PG_uptodate, &(page)->flags)
	139	#endif
	140	#define ClearPageUptodate(page) clear_bit(PG_uptodate, &(page)->flags)
	141
	142	#define PageDirty(page) test_bit(PG_dirty, &(page)->flags)
	143	#define SetPageDirty(page) set_bit(PG_dirty, &(page)->flags)
	144	#define TestSetPageDirty(page) test_and_set_bit(PG_dirty, &(page)->flags)
	145	#define ClearPageDirty(page) clear_bit(PG_dirty, &(page)->flags)
242e5468	146	#define __ClearPageDirty(page) __clear_bit(PG_dirty, &(page)->flags)
1da177e4 LT	147	#define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)
1da177e4 LT	148
1da177e4	149	#define PageLRU(page) test_bit(PG_lru, &(page)->flags)
8d438f96 NP	150	#define SetPageLRU(page) set_bit(PG_lru, &(page)->flags)
8d438f96 NP	151	#define ClearPageLRU(page) clear_bit(PG_lru, &(page)->flags)
67453911	152	#define __ClearPageLRU(page) __clear_bit(PG_lru, &(page)->flags)
1da177e4 LT	153
	154	#define PageActive(page) test_bit(PG_active, &(page)->flags)
	155	#define SetPageActive(page) set_bit(PG_active, &(page)->flags)
	156	#define ClearPageActive(page) clear_bit(PG_active, &(page)->flags)
67453911	157	#define __ClearPageActive(page) __clear_bit(PG_active, &(page)->flags)
1da177e4 LT	158
1da177e4 LT	159	#define PageSlab(page) test_bit(PG_slab, &(page)->flags)
f205b2fe NP	160	#define __SetPageSlab(page) __set_bit(PG_slab, &(page)->flags)
f205b2fe NP	161	#define __ClearPageSlab(page) __clear_bit(PG_slab, &(page)->flags)
1da177e4 LT	162
1da177e4 LT	163	#ifdef CONFIG_HIGHMEM
cbe37d09	164	#define PageHighMem(page) is_highmem(page_zone(page))
1da177e4 LT	165	#else
	166	#define PageHighMem(page) 0 /* needed to optimize away at compile time */
	167	#endif
	168
	169	#define PageChecked(page) test_bit(PG_checked, &(page)->flags)
	170	#define SetPageChecked(page) set_bit(PG_checked, &(page)->flags)
	171	#define ClearPageChecked(page) clear_bit(PG_checked, &(page)->flags)
	172
	173	#define PageReserved(page) test_bit(PG_reserved, &(page)->flags)
	174	#define SetPageReserved(page) set_bit(PG_reserved, &(page)->flags)
	175	#define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
	176	#define __ClearPageReserved(page) __clear_bit(PG_reserved, &(page)->flags)
	177
	178	#define SetPagePrivate(page) set_bit(PG_private, &(page)->flags)
	179	#define ClearPagePrivate(page) clear_bit(PG_private, &(page)->flags)
	180	#define PagePrivate(page) test_bit(PG_private, &(page)->flags)
	181	#define __SetPagePrivate(page) __set_bit(PG_private, &(page)->flags)
	182	#define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
	183
	184	#define PageWriteback(page) test_bit(PG_writeback, &(page)->flags)
	185	#define SetPageWriteback(page) \
	186	do { \
	187	if (!test_and_set_bit(PG_writeback, \
	188	&(page)->flags)) \
ce866b34	189	inc_zone_page_state(page, NR_WRITEBACK); \
1da177e4 LT	190	} while (0)
	191	#define TestSetPageWriteback(page) \
	192	({ \
	193	int ret; \
	194	ret = test_and_set_bit(PG_writeback, \
	195	&(page)->flags); \
	196	if (!ret) \
ce866b34	197	inc_zone_page_state(page, NR_WRITEBACK); \
1da177e4 LT	198	ret; \
	199	})
	200	#define ClearPageWriteback(page) \
	201	do { \
	202	if (test_and_clear_bit(PG_writeback, \
	203	&(page)->flags)) \
ce866b34	204	dec_zone_page_state(page, NR_WRITEBACK); \
1da177e4 LT	205	} while (0)
	206	#define TestClearPageWriteback(page) \
	207	({ \
	208	int ret; \
	209	ret = test_and_clear_bit(PG_writeback, \
	210	&(page)->flags); \
	211	if (ret) \
ce866b34	212	dec_zone_page_state(page, NR_WRITEBACK); \
1da177e4 LT	213	ret; \
	214	})
	215
676165a8 NP	216	#define PageBuddy(page) test_bit(PG_buddy, &(page)->flags)
	217	#define __SetPageBuddy(page) __set_bit(PG_buddy, &(page)->flags)
	218	#define __ClearPageBuddy(page) __clear_bit(PG_buddy, &(page)->flags)
	219
1da177e4 LT	220	#define PageMappedToDisk(page) test_bit(PG_mappedtodisk, &(page)->flags)
	221	#define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
	222	#define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)
	223
	224	#define PageReclaim(page) test_bit(PG_reclaim, &(page)->flags)
	225	#define SetPageReclaim(page) set_bit(PG_reclaim, &(page)->flags)
	226	#define ClearPageReclaim(page) clear_bit(PG_reclaim, &(page)->flags)
	227	#define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)
	228
1da177e4	229	#define PageCompound(page) test_bit(PG_compound, &(page)->flags)
5e9dace8 NP	230	#define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
5e9dace8 NP	231	#define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)
1da177e4	232
d85f3385	233	/*
6d777953 CL	234	* PG_reclaim is used in combination with PG_compound to mark the
	235	* head and tail of a compound page
	236	*
	237	* PG_compound & PG_reclaim => Tail page
	238	* PG_compound & ~PG_reclaim => Head page
d85f3385	239	*/
6d777953 CL	240
	241	#define PG_head_tail_mask ((1L << PG_compound) \| (1L << PG_reclaim))
	242
	243	#define PageTail(page) ((page->flags & PG_head_tail_mask) \
	244	== PG_head_tail_mask)
	245
	246	static inline void __SetPageTail(struct page *page)
	247	{
	248	page->flags \|= PG_head_tail_mask;
	249	}
	250
	251	static inline void __ClearPageTail(struct page *page)
	252	{
	253	page->flags &= ~PG_head_tail_mask;
	254	}
	255
	256	#define PageHead(page) ((page->flags & PG_head_tail_mask) \
	257	== (1L << PG_compound))
	258	#define __SetPageHead(page) __SetPageCompound(page)
	259	#define __ClearPageHead(page) __ClearPageCompound(page)
d85f3385	260
1da177e4 LT	261	#ifdef CONFIG_SWAP
	262	#define PageSwapCache(page) test_bit(PG_swapcache, &(page)->flags)
	263	#define SetPageSwapCache(page) set_bit(PG_swapcache, &(page)->flags)
	264	#define ClearPageSwapCache(page) clear_bit(PG_swapcache, &(page)->flags)
	265	#else
	266	#define PageSwapCache(page) 0
	267	#endif
	268
	269	#define PageUncached(page) test_bit(PG_uncached, &(page)->flags)
	270	#define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags)
	271	#define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
	272
	273	struct page; /* forward declaration */
	274
fba2591b LT	275	extern void cancel_dirty_page(struct page *page, unsigned int account_size);
fba2591b LT	276
1da177e4 LT	277	int test_clear_page_writeback(struct page *page);
	278	int test_set_page_writeback(struct page *page);
	279
1da177e4 LT	280	static inline void set_page_writeback(struct page *page)
	281	{
	282	test_set_page_writeback(page);
	283	}
	284
	285	#endif /* PAGE_FLAGS_H */