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kernel-ark/include/linux/page-flags.h
Linus Torvalds fba2591bf4 VM: Remove "clear_page_dirty()" and "test_clear_page_dirty()" functions 
They were horribly easy to mis-use because of their tempting naming, and
they also did way more than any users of them generally wanted them to
do.

A dirty page can become clean under two circumstances:

 (a) when we write it out.  We have "clear_page_dirty_for_io()" for
     this, and that function remains unchanged.

     In the "for IO" case it is not sufficient to just clear the dirty
     bit, you also have to mark the page as being under writeback etc.

 (b) when we actually remove a page due to it becoming inaccessible to
     users, notably because it was truncate()'d away or the file (or
     metadata) no longer exists, and we thus want to cancel any
     outstanding dirty state.

For the (b) case, we now introduce "cancel_dirty_page()", which only
touches the page state itself, and verifies that the page is not mapped
(since cancelling writes on a mapped page would be actively wrong as it
is still accessible to users).

Some filesystems need to be fixed up for this: CIFS, FUSE, JFS,
ReiserFS, XFS all use the old confusing functions, and will be fixed
separately in subsequent commits (with some of them just removing the
offending logic, and others using clear_page_dirty_for_io()).

This was confirmed by Martin Michlmayr to fix the apt database
corruption on ARM.

Cc: Martin Michlmayr <tbm@cyrius.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Andrei Popa <andrei.popa@i-neo.ro>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Gordon Farquharson <gordonfarquharson@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-21 09:19:57 -08:00

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/*
* Macros for manipulating and testing page->flags
*/
#ifndef PAGE_FLAGS_H
#define PAGE_FLAGS_H
#include <linux/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_checked 8 /* kill me in 2.5.<early>. */
#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_nosave 13 /* Used for system suspend/resume */
#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_nosave_free 18 /* Used for system suspend/resume */
#define PG_buddy 19 /* Page is free, on buddy lists */
#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_test_and_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 PageNosave(page) test_bit(PG_nosave, &(page)->flags)
#define SetPageNosave(page) set_bit(PG_nosave, &(page)->flags)
#define TestSetPageNosave(page) test_and_set_bit(PG_nosave, &(page)->flags)
#define ClearPageNosave(page) clear_bit(PG_nosave, &(page)->flags)
#define TestClearPageNosave(page) test_and_clear_bit(PG_nosave, &(page)->flags)
#define PageNosaveFree(page) test_bit(PG_nosave_free, &(page)->flags)
#define SetPageNosaveFree(page) set_bit(PG_nosave_free, &(page)->flags)
#define ClearPageNosaveFree(page) clear_bit(PG_nosave_free, &(page)->flags)
#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)
#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 */
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