[mirror_ubuntu-artful-kernel.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>
#ifndef __GENERATING_BOUNDS_H
#include <linux/mm_types.h>
#include <linux/bounds.h>
#endif /* !__GENERATING_BOUNDS_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
 *               (NR_PAGEFLAGS)
 *
 * The fields area is reserved for fields mapping zone, node (for NUMA) and
 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
 */
enum pageflags {
	PG_locked,		/* Page is locked. Don't touch. */
	PG_error,
	PG_referenced,
	PG_uptodate,
	PG_dirty,
	PG_lru,
	PG_active,
	PG_slab,
	PG_owner_priv_1,	/* Owner use. If pagecache, fs may use*/
	PG_arch_1,
	PG_reserved,
	PG_private,		/* If pagecache, has fs-private data */
	PG_writeback,		/* Page is under writeback */
#ifdef CONFIG_PAGEFLAGS_EXTENDED
	PG_head,		/* A head page */
	PG_tail,		/* A tail page */
#else
	PG_compound,		/* A compound page */
#endif
	PG_swapcache,		/* Swap page: swp_entry_t in private */
	PG_mappedtodisk,	/* Has blocks allocated on-disk */
	PG_reclaim,		/* To be reclaimed asap */
	PG_buddy,		/* Page is free, on buddy lists */
#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
	PG_uncached,		/* Page has been mapped as uncached */
#endif
	__NR_PAGEFLAGS
};

#ifndef __GENERATING_BOUNDS_H

/*
 * Macros to create function definitions for page flags
 */
#define TESTPAGEFLAG(uname, lname)					\
static inline int Page##uname(struct page *page) 			\
			{ return test_bit(PG_##lname, &page->flags); }

#define SETPAGEFLAG(uname, lname)					\
static inline void SetPage##uname(struct page *page)			\
			{ set_bit(PG_##lname, &page->flags); }

#define CLEARPAGEFLAG(uname, lname)					\
static inline void ClearPage##uname(struct page *page)			\
			{ clear_bit(PG_##lname, &page->flags); }

#define __SETPAGEFLAG(uname, lname)					\
static inline void __SetPage##uname(struct page *page)			\
			{ __set_bit(PG_##lname, &page->flags); }

#define __CLEARPAGEFLAG(uname, lname)					\
static inline void __ClearPage##uname(struct page *page)		\
			{ __clear_bit(PG_##lname, &page->flags); }

#define TESTSETFLAG(uname, lname)					\
static inline int TestSetPage##uname(struct page *page)			\
		{ return test_and_set_bit(PG_##lname, &page->flags); }

#define TESTCLEARFLAG(uname, lname)					\
static inline int TestClearPage##uname(struct page *page)		\
		{ return test_and_clear_bit(PG_##lname, &page->flags); }


#define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)		\
	SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)

#define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)		\
	__SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)

#define PAGEFLAG_FALSE(uname) 						\
static inline int Page##uname(struct page *page) 			\
			{ return 0; }

#define TESTSCFLAG(uname, lname)					\
	TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)

struct page;	/* forward declaration */

PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked)
PAGEFLAG(Error, error)
PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
__PAGEFLAG(Slab, slab)
PAGEFLAG(Checked, owner_priv_1)		/* Used by some filesystems */
PAGEFLAG(Pinned, owner_priv_1) TESTSCFLAG(Pinned, owner_priv_1) /* Xen */
PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
	__SETPAGEFLAG(Private, private)

/*
 * Only test-and-set exist for PG_writeback.  The unconditional operators are
 * risky: they bypass page accounting.
 */
TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
__PAGEFLAG(Buddy, buddy)
PAGEFLAG(MappedToDisk, mappedtodisk)

/* PG_readahead is only used for file reads; PG_reclaim is only for writes */
PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
PAGEFLAG(Readahead, reclaim)		/* Reminder to do async read-ahead */

#ifdef CONFIG_HIGHMEM
/*
 * Must use a macro here due to header dependency issues. page_zone() is not
 * available at this point.
 */
#define PageHighMem(__p) is_highmem(page_zone(__p))
#else
PAGEFLAG_FALSE(HighMem)
#endif

#ifdef CONFIG_SWAP
PAGEFLAG(SwapCache, swapcache)
#else
PAGEFLAG_FALSE(SwapCache)
#endif

#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
PAGEFLAG(Uncached, uncached)
#else
PAGEFLAG_FALSE(Uncached)
#endif

static inline int PageUptodate(struct page *page)
{
	int ret = test_bit(PG_uptodate, &(page)->flags);

	/*
	 * Must ensure that the data we read out of the page is loaded
	 * _after_ we've loaded page->flags to check for PageUptodate.
	 * We can skip the barrier if the page is not uptodate, because
	 * we wouldn't be reading anything from it.
	 *
	 * See SetPageUptodate() for the other side of the story.
	 */
	if (ret)
		smp_rmb();

	return ret;
}

static inline void __SetPageUptodate(struct page *page)
{
	smp_wmb();
	__set_bit(PG_uptodate, &(page)->flags);
#ifdef CONFIG_S390
	page_clear_dirty(page);
#endif
}

static inline void SetPageUptodate(struct page *page)
{
#ifdef CONFIG_S390
	if (!test_and_set_bit(PG_uptodate, &page->flags))
		page_clear_dirty(page);
#else
	/*
	 * Memory barrier must be issued before setting the PG_uptodate bit,
	 * so that all previous stores issued in order to bring the page
	 * uptodate are actually visible before PageUptodate becomes true.
	 *
	 * s390 doesn't need an explicit smp_wmb here because the test and
	 * set bit already provides full barriers.
	 */
	smp_wmb();
	set_bit(PG_uptodate, &(page)->flags);
#endif
}

CLEARPAGEFLAG(Uptodate, uptodate)

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);
}

#ifdef CONFIG_PAGEFLAGS_EXTENDED
/*
 * System with lots of page flags available. This allows separate
 * flags for PageHead() and PageTail() checks of compound pages so that bit
 * tests can be used in performance sensitive paths. PageCompound is
 * generally not used in hot code paths.
 */
__PAGEFLAG(Head, head)
__PAGEFLAG(Tail, tail)

static inline int PageCompound(struct page *page)
{
	return page->flags & ((1L << PG_head) | (1L << PG_tail));

}
#else
/*
 * Reduce page flag use as much as possible by overlapping
 * compound page flags with the flags used for page cache pages. Possible
 * because PageCompound is always set for compound pages and not for
 * pages on the LRU and/or pagecache.
 */
TESTPAGEFLAG(Compound, compound)
__PAGEFLAG(Head, compound)

/*
 * PG_reclaim is used in combination with PG_compound to mark the
 * head and tail of a compound page. This saves one page flag
 * but makes it impossible to use compound pages for the page cache.
 * The PG_reclaim bit would have to be used for reclaim or readahead
 * if compound pages enter the page cache.
 *
 * PG_compound & PG_reclaim	=> Tail page
 * PG_compound & ~PG_reclaim	=> Head page
 */
#define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))

static inline int PageTail(struct page *page)
{
	return ((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;
}

#endif /* !PAGEFLAGS_EXTENDED */

#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)

/*
 * 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)

/*
 * 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)

/*
 * 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.
 */
#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | 1 << PG_reserved | 1 << PG_dirty)

#endif /* !__GENERATING_BOUNDS_H */
#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>
9223b419	9	#ifndef __GENERATING_BOUNDS_H
6d777953	10	#include <linux/mm_types.h>
9223b419 CL	11	#include <linux/bounds.h>
9223b419 CL	12	#endif /* !__GENERATING_BOUNDS_H */
f886ed44	13
1da177e4 LT	14	/*
	15	* Various page->flags bits:
	16	*
	17	* PG_reserved is set for special pages, which can never be swapped out. Some
	18	* of them might not even exist (eg empty_bad_page)...
	19	*
da6052f7 NP	20	* The PG_private bitflag is set on pagecache pages if they contain filesystem
	21	* specific data (which is normally at page->private). It can be used by
	22	* private allocations for its own usage.
1da177e4	23	*
da6052f7 NP	24	* During initiation of disk I/O, PG_locked is set. This bit is set before I/O
	25	* and cleared when writeback _starts_ or when read _completes_. PG_writeback
	26	* is set before writeback starts and cleared when it finishes.
	27	*
	28	* PG_locked also pins a page in pagecache, and blocks truncation of the file
	29	* while it is held.
	30	*
	31	* page_waitqueue(page) is a wait queue of all tasks waiting for the page
	32	* to become unlocked.
1da177e4 LT	33	*
	34	* PG_uptodate tells whether the page's contents is valid. When a read
	35	* completes, the page becomes uptodate, unless a disk I/O error happened.
	36	*
da6052f7 NP	37	* PG_referenced, PG_reclaim are used for page reclaim for anonymous and
da6052f7 NP	38	* file-backed pagecache (see mm/vmscan.c).
1da177e4 LT	39	*
	40	* PG_error is set to indicate that an I/O error occurred on this page.
	41	*
	42	* PG_arch_1 is an architecture specific page state bit. The generic code
	43	* guarantees that this bit is cleared for a page when it first is entered into
	44	* the page cache.
	45	*
	46	* PG_highmem pages are not permanently mapped into the kernel virtual address
	47	* space, they need to be kmapped separately for doing IO on the pages. The
	48	* struct page (these bits with information) are always mapped into kernel
	49	* address space...
da6052f7 NP	50	*
	51	* PG_buddy is set to indicate that the page is free and in the buddy system
	52	* (see mm/page_alloc.c).
	53	*
1da177e4 LT	54	*/
	55
	56	/*
	57	* Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
91fc8ab3 AW	58	* locked- and dirty-page accounting.
	59	*
	60	* The page flags field is split into two parts, the main flags area
	61	* which extends from the low bits upwards, and the fields area which
	62	* extends from the high bits downwards.
	63	*
	64	* \| FIELD \| ... \| FLAGS \|
9223b419 CL	65	* N-1 ^ 0
9223b419 CL	66	* (NR_PAGEFLAGS)
91fc8ab3	67	*
9223b419 CL	68	* The fields area is reserved for fields mapping zone, node (for NUMA) and
	69	* SPARSEMEM section (for variants of SPARSEMEM that require section ids like
	70	* SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
1da177e4	71	*/
e2683181 CL	72	enum pageflags {
	73	PG_locked, /* Page is locked. Don't touch. */
	74	PG_error,
	75	PG_referenced,
	76	PG_uptodate,
	77	PG_dirty,
	78	PG_lru,
	79	PG_active,
	80	PG_slab,
	81	PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
e2683181 CL	82	PG_arch_1,
	83	PG_reserved,
	84	PG_private, /* If pagecache, has fs-private data */
	85	PG_writeback, /* Page is under writeback */
e20b8cca CL	86	#ifdef CONFIG_PAGEFLAGS_EXTENDED
	87	PG_head, /* A head page */
	88	PG_tail, /* A tail page */
	89	#else
e2683181	90	PG_compound, /* A compound page */
e20b8cca	91	#endif
e2683181 CL	92	PG_swapcache, /* Swap page: swp_entry_t in private */
	93	PG_mappedtodisk, /* Has blocks allocated on-disk */
	94	PG_reclaim, /* To be reclaimed asap */
e2683181	95	PG_buddy, /* Page is free, on buddy lists */
602c4d11 CL	96	#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
602c4d11 CL	97	PG_uncached, /* Page has been mapped as uncached */
f886ed44	98	#endif
9223b419	99	__NR_PAGEFLAGS
e2683181	100	};
1da177e4	101
9223b419 CL	102	#ifndef __GENERATING_BOUNDS_H
9223b419 CL	103
f94a62e9 CL	104	/*
	105	* Macros to create function definitions for page flags
	106	*/
	107	#define TESTPAGEFLAG(uname, lname) \
	108	static inline int Page##uname(struct page *page) \
	109	{ return test_bit(PG_##lname, &page->flags); }
	110
	111	#define SETPAGEFLAG(uname, lname) \
	112	static inline void SetPage##uname(struct page *page) \
	113	{ set_bit(PG_##lname, &page->flags); }
	114
	115	#define CLEARPAGEFLAG(uname, lname) \
	116	static inline void ClearPage##uname(struct page *page) \
	117	{ clear_bit(PG_##lname, &page->flags); }
	118
	119	#define __SETPAGEFLAG(uname, lname) \
	120	static inline void __SetPage##uname(struct page *page) \
	121	{ __set_bit(PG_##lname, &page->flags); }
	122
	123	#define __CLEARPAGEFLAG(uname, lname) \
	124	static inline void __ClearPage##uname(struct page *page) \
	125	{ __clear_bit(PG_##lname, &page->flags); }
	126
	127	#define TESTSETFLAG(uname, lname) \
	128	static inline int TestSetPage##uname(struct page *page) \
	129	{ return test_and_set_bit(PG_##lname, &page->flags); }
	130
	131	#define TESTCLEARFLAG(uname, lname) \
	132	static inline int TestClearPage##uname(struct page *page) \
	133	{ return test_and_clear_bit(PG_##lname, &page->flags); }
	134
	135
	136	#define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
	137	SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
	138
	139	#define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
	140	__SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
	141
ec7cade8 CL	142	#define PAGEFLAG_FALSE(uname) \
	143	static inline int Page##uname(struct page *page) \
	144	{ return 0; }
	145
f94a62e9 CL	146	#define TESTSCFLAG(uname, lname) \
	147	TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
	148
6a1e7f77 CL	149	struct page; /* forward declaration */
	150
	151	PAGEFLAG(Locked, locked) TESTSCFLAG(Locked, locked)
	152	PAGEFLAG(Error, error)
	153	PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
	154	PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
	155	PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
	156	PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
	157	__PAGEFLAG(Slab, slab)
0a128b2b CL	158	PAGEFLAG(Checked, owner_priv_1) /* Used by some filesystems */
0a128b2b CL	159	PAGEFLAG(Pinned, owner_priv_1) TESTSCFLAG(Pinned, owner_priv_1) /* Xen */
6a1e7f77 CL	160	PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
	161	PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
	162	__SETPAGEFLAG(Private, private)
	163
	164	/*
	165	* Only test-and-set exist for PG_writeback. The unconditional operators are
	166	* risky: they bypass page accounting.
	167	*/
	168	TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
	169	__PAGEFLAG(Buddy, buddy)
	170	PAGEFLAG(MappedToDisk, mappedtodisk)
	171
	172	/* PG_readahead is only used for file reads; PG_reclaim is only for writes */
	173	PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
0a128b2b	174	PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */
6a1e7f77 CL	175
6a1e7f77 CL	176	#ifdef CONFIG_HIGHMEM
1da177e4	177	/*
6a1e7f77 CL	178	* Must use a macro here due to header dependency issues. page_zone() is not
6a1e7f77 CL	179	* available at this point.
1da177e4	180	*/
0a128b2b	181	#define PageHighMem(__p) is_highmem(page_zone(__p))
6a1e7f77	182	#else
ec7cade8	183	PAGEFLAG_FALSE(HighMem)
6a1e7f77 CL	184	#endif
	185
	186	#ifdef CONFIG_SWAP
	187	PAGEFLAG(SwapCache, swapcache)
	188	#else
ec7cade8	189	PAGEFLAG_FALSE(SwapCache)
6a1e7f77 CL	190	#endif
6a1e7f77 CL	191
602c4d11	192	#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
6a1e7f77	193	PAGEFLAG(Uncached, uncached)
602c4d11	194	#else
ec7cade8	195	PAGEFLAG_FALSE(Uncached)
6a1e7f77	196	#endif
1da177e4	197
0ed361de NP	198	static inline int PageUptodate(struct page *page)
	199	{
	200	int ret = test_bit(PG_uptodate, &(page)->flags);
	201
	202	/*
	203	* Must ensure that the data we read out of the page is loaded
	204	* _after_ we've loaded page->flags to check for PageUptodate.
	205	* We can skip the barrier if the page is not uptodate, because
	206	* we wouldn't be reading anything from it.
	207	*
	208	* See SetPageUptodate() for the other side of the story.
	209	*/
	210	if (ret)
	211	smp_rmb();
	212
	213	return ret;
	214	}
	215
	216	static inline void __SetPageUptodate(struct page *page)
	217	{
	218	smp_wmb();
	219	__set_bit(PG_uptodate, &(page)->flags);
f6ac2354	220	#ifdef CONFIG_S390
0ed361de NP	221	page_clear_dirty(page);
	222	#endif
	223	}
	224
2dcea57a HC	225	static inline void SetPageUptodate(struct page *page)
2dcea57a HC	226	{
0ed361de	227	#ifdef CONFIG_S390
2dcea57a	228	if (!test_and_set_bit(PG_uptodate, &page->flags))
6c210482	229	page_clear_dirty(page);
f6ac2354	230	#else
0ed361de NP	231	/*
	232	* Memory barrier must be issued before setting the PG_uptodate bit,
	233	* so that all previous stores issued in order to bring the page
	234	* uptodate are actually visible before PageUptodate becomes true.
	235	*
	236	* s390 doesn't need an explicit smp_wmb here because the test and
	237	* set bit already provides full barriers.
	238	*/
	239	smp_wmb();
	240	set_bit(PG_uptodate, &(page)->flags);
1da177e4	241	#endif
0ed361de NP	242	}
0ed361de NP	243
6a1e7f77	244	CLEARPAGEFLAG(Uptodate, uptodate)
1da177e4	245
6a1e7f77	246	extern void cancel_dirty_page(struct page *page, unsigned int account_size);
d77c2d7c	247
6a1e7f77 CL	248	int test_clear_page_writeback(struct page *page);
6a1e7f77 CL	249	int test_set_page_writeback(struct page *page);
1da177e4	250
6a1e7f77 CL	251	static inline void set_page_writeback(struct page *page)
	252	{
	253	test_set_page_writeback(page);
	254	}
1da177e4	255
e20b8cca CL	256	#ifdef CONFIG_PAGEFLAGS_EXTENDED
	257	/*
	258	* System with lots of page flags available. This allows separate
	259	* flags for PageHead() and PageTail() checks of compound pages so that bit
	260	* tests can be used in performance sensitive paths. PageCompound is
	261	* generally not used in hot code paths.
	262	*/
	263	__PAGEFLAG(Head, head)
	264	__PAGEFLAG(Tail, tail)
	265
	266	static inline int PageCompound(struct page *page)
	267	{
	268	return page->flags & ((1L << PG_head) \| (1L << PG_tail));
	269
	270	}
	271	#else
	272	/*
	273	* Reduce page flag use as much as possible by overlapping
	274	* compound page flags with the flags used for page cache pages. Possible
	275	* because PageCompound is always set for compound pages and not for
	276	* pages on the LRU and/or pagecache.
	277	*/
6a1e7f77 CL	278	TESTPAGEFLAG(Compound, compound)
6a1e7f77 CL	279	__PAGEFLAG(Head, compound)
1da177e4	280
d85f3385	281	/*
6d777953	282	* PG_reclaim is used in combination with PG_compound to mark the
6a1e7f77 CL	283	* head and tail of a compound page. This saves one page flag
	284	* but makes it impossible to use compound pages for the page cache.
	285	* The PG_reclaim bit would have to be used for reclaim or readahead
	286	* if compound pages enter the page cache.
6d777953 CL	287	*
	288	* PG_compound & PG_reclaim => Tail page
	289	* PG_compound & ~PG_reclaim => Head page
d85f3385	290	*/
6d777953 CL	291	#define PG_head_tail_mask ((1L << PG_compound) \| (1L << PG_reclaim))
6d777953 CL	292
6a1e7f77 CL	293	static inline int PageTail(struct page *page)
	294	{
	295	return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
	296	}
6d777953 CL	297
	298	static inline void __SetPageTail(struct page *page)
	299	{
	300	page->flags \|= PG_head_tail_mask;
	301	}
	302
	303	static inline void __ClearPageTail(struct page *page)
	304	{
	305	page->flags &= ~PG_head_tail_mask;
	306	}
	307
e20b8cca	308	#endif /* !PAGEFLAGS_EXTENDED */
dfa7e20c RA	309
	310	#define PAGE_FLAGS (1 << PG_lru \| 1 << PG_private \| 1 << PG_locked \| \
	311	1 << PG_buddy \| 1 << PG_writeback \| \
	312	1 << PG_slab \| 1 << PG_swapcache \| 1 << PG_active)
	313
	314	/*
	315	* Flags checked in bad_page(). Pages on the free list should not have
	316	* these flags set. It they are, there is a problem.
	317	*/
	318	#define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS \| 1 << PG_reclaim \| 1 << PG_dirty)
	319
	320	/*
	321	* Flags checked when a page is freed. Pages being freed should not have
	322	* these flags set. It they are, there is a problem.
	323	*/
	324	#define PAGE_FLAGS_CHECK_AT_FREE (PAGE_FLAGS \| 1 << PG_reserved)
	325
	326	/*
	327	* Flags checked when a page is prepped for return by the page allocator.
	328	* Pages being prepped should not have these flags set. It they are, there
	329	* is a problem.
	330	*/
	331	#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS \| 1 << PG_reserved \| 1 << PG_dirty)
	332
9223b419	333	#endif /* !__GENERATING_BOUNDS_H */
1da177e4	334	#endif /* PAGE_FLAGS_H */