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* 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
* 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 */
* 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)
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);
#ifdef CONFIG_S390
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);
#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)
#define PageHighMem(page) is_highmem(page_zone(page))
#define PageHighMem(page) 0 /* needed to optimize away at compile time */
#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)
* Only test-and-set exist for PG_writeback. The unconditional operators are
* risky: they bypass page accounting.
#define PageWriteback(page) test_bit(PG_writeback, &(page)->flags)
#define TestSetPageWriteback(page) test_and_set_bit(PG_writeback, \
#define TestClearPageWriteback(page) test_and_clear_bit(PG_writeback, \
#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)
#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)
#define PageSwapCache(page) 0
#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)
#endif /* PAGE_FLAGS_H */