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

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- 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: Vladimir 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vladimir Davydov 2016-07-26 15:24:18 -07:00 committed by Linus Torvalds
parent 99691addb4
commit 632c0a1aff
3 changed files with 40 additions and 41 deletions
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5
include/linux/mm_types.h
View File

@ -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;

73
include/linux/page-flags.h
View File

@ -603,55 +603,46 @@ 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)
#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);
}
/*
* 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)
extern bool is_free_buddy_page(struct page *page);
#define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
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);
}
__PAGEFLAG(Isolated, isolated, PF_ANY);
/*

3
scripts/tags.sh
View File

@ -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/'