diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mm.h | 56 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 21 |
2 files changed, 39 insertions, 38 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 7438071b44a..c1ce6c0d7de 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -356,36 +356,39 @@ static inline struct page *compound_head(struct page *page) return page; } +/* + * The atomic page->_mapcount, starts from -1: so that transitions + * both from it and to it can be tracked, using atomic_inc_and_test + * and atomic_add_negative(-1). + */ +static inline void reset_page_mapcount(struct page *page) +{ + atomic_set(&(page)->_mapcount, -1); +} + +static inline int page_mapcount(struct page *page) +{ + return atomic_read(&(page)->_mapcount) + 1; +} + static inline int page_count(struct page *page) { return atomic_read(&compound_head(page)->_count); } +extern bool __get_page_tail(struct page *page); + static inline void get_page(struct page *page) { + if (unlikely(PageTail(page))) + if (likely(__get_page_tail(page))) + return; /* * Getting a normal page or the head of a compound page - * requires to already have an elevated page->_count. Only if - * we're getting a tail page, the elevated page->_count is - * required only in the head page, so for tail pages the - * bugcheck only verifies that the page->_count isn't - * negative. + * requires to already have an elevated page->_count. */ - VM_BUG_ON(atomic_read(&page->_count) < !PageTail(page)); + VM_BUG_ON(atomic_read(&page->_count) <= 0); atomic_inc(&page->_count); - /* - * Getting a tail page will elevate both the head and tail - * page->_count(s). - */ - if (unlikely(PageTail(page))) { - /* - * This is safe only because - * __split_huge_page_refcount can't run under - * get_page(). - */ - VM_BUG_ON(atomic_read(&page->first_page->_count) <= 0); - atomic_inc(&page->first_page->_count); - } } static inline struct page *virt_to_head_page(const void *x) @@ -804,21 +807,6 @@ static inline pgoff_t page_index(struct page *page) } /* - * The atomic page->_mapcount, like _count, starts from -1: - * so that transitions both from it and to it can be tracked, - * using atomic_inc_and_test and atomic_add_negative(-1). - */ -static inline void reset_page_mapcount(struct page *page) -{ - atomic_set(&(page)->_mapcount, -1); -} - -static inline int page_mapcount(struct page *page) -{ - return atomic_read(&(page)->_mapcount) + 1; -} - -/* * Return true if this page is mapped into pagetables. */ static inline int page_mapped(struct page *page) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 774b8952deb..10a2f62cd56 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -62,10 +62,23 @@ struct page { struct { union { - atomic_t _mapcount; /* Count of ptes mapped in mms, - * to show when page is mapped - * & limit reverse map searches. - */ + /* + * Count of ptes mapped in + * mms, to show when page is + * mapped & limit reverse map + * searches. + * + * Used also for tail pages + * refcounting instead of + * _count. Tail pages cannot + * be mapped and keeping the + * tail page _count zero at + * all times guarantees + * get_page_unless_zero() will + * never succeed on tail + * pages. + */ + atomic_t _mapcount; struct { unsigned inuse:16; |