From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Subject: 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@xxxxxxxxxxxxx Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm_types.h | 5 ++ include/linux/page-flags.h | 73 +++++++++++++++-------------------- scripts/tags.sh | 3 + 3 files changed, 40 insertions(+), 41 deletions(-) diff -puN include/linux/mm_types.h~mm-clean-up-non-standard-page-_mapcount-users include/linux/mm_types.h --- a/include/linux/mm_types.h~mm-clean-up-non-standard-page-_mapcount-users +++ a/include/linux/mm_types.h @@ -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; diff -puN include/linux/page-flags.h~mm-clean-up-non-standard-page-_mapcount-users include/linux/page-flags.h --- a/include/linux/page-flags.h~mm-clean-up-non-standard-page-_mapcount-users +++ a/include/linux/page-flags.h @@ -604,54 +604,45 @@ TESTPAGEFLAG_FALSE(DoubleMap) #endif /* - * 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. + * 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_BUDDY_MAPCOUNT_VALUE (-128) - -static inline int PageBuddy(struct page *page) -{ - return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE; +#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); \ } -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); -} +/* + * PageBuddy() indicate that the page is free and in the buddy system + * (see mm/page_alloc.c). + */ +#define PAGE_BUDDY_MAPCOUNT_VALUE (-128) +PAGE_MAPCOUNT_OPS(Buddy, BUDDY) -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); /* diff -puN scripts/tags.sh~mm-clean-up-non-standard-page-_mapcount-users scripts/tags.sh --- a/scripts/tags.sh~mm-clean-up-non-standard-page-_mapcount-users +++ a/scripts/tags.sh @@ -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/' _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
