blob: 5b59f35dcb8fdd3ef12c4bc4f2cd5f439e63053b [file] [log] [blame]
* Macros for manipulating and testing page->flags
#ifndef PAGE_FLAGS_H
#define PAGE_FLAGS_H
#include <linux/types.h>
#include <linux/mm_types.h>
#include <generated/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).
* PG_hwpoison indicates that a page got corrupted in hardware and contains
* data with incorrect ECC bits that triggered a machine check. Accessing is
* not safe since it may cause another machine check. Don't touch!
* 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
* The fields area is reserved for fields mapping zone, node (for NUMA) and
* SPARSEMEM section (for variants of SPARSEMEM that require section ids like
enum pageflags {
PG_locked, /* Page is locked. Don't touch. */
PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
PG_private, /* If pagecache, has fs-private data */
PG_private_2, /* If pagecache, has fs aux data */
PG_writeback, /* Page is under writeback */
PG_head, /* A head page */
PG_tail, /* A tail page */
PG_compound, /* A compound page */
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 */
PG_swapbacked, /* Page is backed by RAM/swap */
PG_unevictable, /* Page is "unevictable" */
PG_mlocked, /* Page is vma mlocked */
PG_uncached, /* Page has been mapped as uncached */
PG_hwpoison, /* hardware poisoned page. Don't touch */
/* Filesystems */
PG_checked = PG_owner_priv_1,
/* Two page bits are conscripted by FS-Cache to maintain local caching
* state. These bits are set on pages belonging to the netfs's inodes
* when those inodes are being locally cached.
PG_fscache = PG_private_2, /* page backed by cache */
/* XEN */
PG_pinned = PG_owner_priv_1,
PG_savepinned = PG_dirty,
/* SLOB */
PG_slob_free = PG_private,
/* SLUB */
PG_slub_frozen = PG_active,
PG_slub_debug = PG_error,
* 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 __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)
#define SETPAGEFLAG_NOOP(uname) \
static inline void SetPage##uname(struct page *page) { }
#define CLEARPAGEFLAG_NOOP(uname) \
static inline void ClearPage##uname(struct page *page) { }
#define __CLEARPAGEFLAG_NOOP(uname) \
static inline void __ClearPage##uname(struct page *page) { }
#define TESTCLEARFLAG_FALSE(uname) \
static inline int TestClearPage##uname(struct page *page) { return 0; }
#define __TESTCLEARFLAG_FALSE(uname) \
static inline int __TestClearPage##uname(struct page *page) { return 0; }
struct page; /* forward declaration */
TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
PAGEFLAG(Error, error)
PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
TESTCLEARFLAG(Active, active)
__PAGEFLAG(Slab, slab)
PAGEFLAG(Checked, checked) /* Used by some filesystems */
PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */
PAGEFLAG(SavePinned, savepinned); /* Xen */
PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
__PAGEFLAG(SlobFree, slob_free)
__PAGEFLAG(SlubFrozen, slub_frozen)
__PAGEFLAG(SlubDebug, slub_debug)
* Private page markings that may be used by the filesystem that owns the page
* for its own purposes.
* - PG_private and PG_private_2 cause releasepage() and co to be invoked
PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
__CLEARPAGEFLAG(Private, private)
PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
* 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 */
* 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))
PAGEFLAG(SwapCache, swapcache)
PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
TESTCLEARFLAG(Unevictable, unevictable)
PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
PAGEFLAG(Uncached, uncached)
PAGEFLAG(HWPoison, hwpoison)
TESTSCFLAG(HWPoison, hwpoison)
#define __PG_HWPOISON (1UL << PG_hwpoison)
#define __PG_HWPOISON 0
u64 stable_page_flags(struct page *page);
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)
return ret;
static inline void __SetPageUptodate(struct page *page)
__set_bit(PG_uptodate, &(page)->flags);
static inline void SetPageUptodate(struct page *page)
#ifdef CONFIG_S390
if (!test_and_set_bit(PG_uptodate, &page->flags))
* 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.
set_bit(PG_uptodate, &(page)->flags);
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)
* 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));
* 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;
#define __PG_MLOCKED (1 << PG_mlocked)
#define __PG_MLOCKED 0
* Flags checked when a page is freed. Pages being freed should not have
* these flags set. It they are, there is a problem.
(1 << PG_lru | 1 << PG_locked | \
1 << PG_private | 1 << PG_private_2 | \
1 << PG_buddy | 1 << PG_writeback | 1 << PG_reserved | \
1 << PG_slab | 1 << PG_swapcache | 1 << PG_active | \
1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON)
* Flags checked when a page is prepped for return by the page allocator.
* Pages being prepped should not have any flags set. It they are set,
* there has been a kernel bug or struct page corruption.
(1 << PG_private | 1 << PG_private_2)
* page_has_private - Determine if page has private stuff
* @page: The page to be checked
* Determine if a page has private stuff, indicating that release routines
* should be invoked upon it.
static inline int page_has_private(struct page *page)
return !!(page->flags & PAGE_FLAGS_PRIVATE);
#endif /* !__GENERATING_BOUNDS_H */
#endif /* PAGE_FLAGS_H */