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Commit 632c0a1a authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
Browse files

mm: clean up non-standard page->_mapcount users 

 - Add a proper comment to page->_mapcount.

 - Introduce a macro for generating helper functions.

 - Place all special page->_mapcount values next to each other so that
   readers can see all possible values and so we don't get duplicates.

Link: http://lkml.kernel.org/r/502f49000e0b63e6c62e338fac6b420bf34fb526.1464079537.git.vdavydov@virtuozzo.com


Signed-off-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 99691add

include/linux/mm_types.h

+5 −0
Original line number Diff line number Diff line
@@ -85,6 +85,11 @@ struct page { 
				/*

				 * Count of ptes mapped in mms, to show when

				 * page is mapped & limit reverse map searches.

				 *

				 * Extra information about page type may be

				 * stored here for pages that are never mapped,

				 * in which case the value MUST BE <= -2.

				 * See page-flags.h for more details.

				 */

				atomic_t _mapcount;

include/linux/page-flags.h

+32 −41
Original line number Diff line number Diff line
@@ -603,54 +603,45 @@ TESTPAGEFLAG_FALSE(DoubleMap) 
	TESTCLEARFLAG_FALSE(DoubleMap)

#endif



/*

 * For pages that are never mapped to userspace, page->mapcount may be

 * used for storing extra information about page type. Any value used

 * for this purpose must be <= -2, but it's better start not too close

 * to -2 so that an underflow of the page_mapcount() won't be mistaken

 * for a special page.

 */

#define PAGE_MAPCOUNT_OPS(uname, lname)					\

static __always_inline int Page##uname(struct page *page)		\

{									\

	return atomic_read(&page->_mapcount) ==				\

				PAGE_##lname##_MAPCOUNT_VALUE;		\

}									\

static __always_inline void __SetPage##uname(struct page *page)		\

{									\

	VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);	\

	atomic_set(&page->_mapcount, PAGE_##lname##_MAPCOUNT_VALUE);	\

}									\

static __always_inline void __ClearPage##uname(struct page *page)	\

{									\

	VM_BUG_ON_PAGE(!Page##uname(page), page);			\

	atomic_set(&page->_mapcount, -1);				\

}



/*

 * PageBuddy() indicate that the page is free and in the buddy system

 * (see mm/page_alloc.c).

 *

 * PAGE_BUDDY_MAPCOUNT_VALUE must be <= -2 but better not too close to

 * -2 so that an underflow of the page_mapcount() won't be mistaken

 * for a genuine PAGE_BUDDY_MAPCOUNT_VALUE. -128 can be created very

 * efficiently by most CPU architectures.

 */

#define PAGE_BUDDY_MAPCOUNT_VALUE		(-128)

PAGE_MAPCOUNT_OPS(Buddy, BUDDY)



static inline int PageBuddy(struct page *page)

{

	return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE;

}



static inline void __SetPageBuddy(struct page *page)

{

	VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);

	atomic_set(&page->_mapcount, PAGE_BUDDY_MAPCOUNT_VALUE);

}



static inline void __ClearPageBuddy(struct page *page)

{

	VM_BUG_ON_PAGE(!PageBuddy(page), page);

	atomic_set(&page->_mapcount, -1);

}



extern bool is_free_buddy_page(struct page *page);



/*

 * PageBalloon() is set on pages that are on the balloon page list

 * (see mm/balloon_compaction.c).

 */

#define PAGE_BALLOON_MAPCOUNT_VALUE		(-256)

PAGE_MAPCOUNT_OPS(Balloon, BALLOON)



static inline int PageBalloon(struct page *page)

{

	return atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE;

}



static inline void __SetPageBalloon(struct page *page)

{

	VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);

	atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);

}



static inline void __ClearPageBalloon(struct page *page)

{

	VM_BUG_ON_PAGE(!PageBalloon(page), page);

	atomic_set(&page->_mapcount, -1);

}

extern bool is_free_buddy_page(struct page *page);



__PAGEFLAG(Isolated, isolated, PF_ANY);

scripts/tags.sh

+3 −0
Original line number Diff line number Diff line
@@ -185,6 +185,9 @@ regex_c=( 
	'/\<CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/ClearPage\1/'

	'/\<__CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/__ClearPage\1/'

	'/\<TESTCLEARFLAG_FALSE(\([[:alnum:]_]*\).*/TestClearPage\1/'

	'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/Page\1/'

	'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__SetPage\1/'

	'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__ClearPage\1/'

	'/^TASK_PFA_TEST([^,]*, *\([[:alnum:]_]*\))/task_\1/'

	'/^TASK_PFA_SET([^,]*, *\([[:alnum:]_]*\))/task_set_\1/'

	'/^TASK_PFA_CLEAR([^,]*, *\([[:alnum:]_]*\))/task_clear_\1/'