diff options
| -rw-r--r-- | include/linux/mm.h | 11 | ||||
| -rw-r--r-- | include/linux/page-flags.h | 37 | ||||
| -rw-r--r-- | mm/page_alloc.c | 10 |
3 files changed, 32 insertions, 26 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 8c149fa..695b904 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -269,14 +269,7 @@ static inline int get_page_unless_zero(struct page *page) static inline struct page *compound_head(struct page *page) { - /* - * We could avoid the PageCompound(page) check if - * we would not overload PageTail(). - * - * This check has to be done in several performance critical - * paths of the slab etc. IMHO PageTail deserves its own flag. - */ - if (unlikely(PageCompound(page) && PageTail(page))) + if (unlikely(PageTail(page))) return page->first_page; return page; } @@ -327,7 +320,7 @@ static inline compound_page_dtor *get_compound_page_dtor(struct page *page) static inline int compound_order(struct page *page) { - if (!PageCompound(page) || PageTail(page)) + if (!PageHead(page)) return 0; return (unsigned long)page[1].lru.prev; } diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index a1e1436..a3c8b60 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -6,6 +6,7 @@ #define PAGE_FLAGS_H #include <linux/types.h> +#include <linux/mm_types.h> /* * Various page->flags bits: @@ -94,12 +95,6 @@ /* PG_owner_priv_1 users should have descriptive aliases */ #define PG_checked PG_owner_priv_1 /* Used by some filesystems */ -/* - * Marks tail portion of a compound page. We currently do not reclaim - * compound pages so we can reuse a flag only used for reclaim here. - */ -#define PG_tail PG_reclaim - #if (BITS_PER_LONG > 32) /* * 64-bit-only flags build down from bit 31 @@ -248,12 +243,32 @@ static inline void SetPageUptodate(struct page *page) #define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags) /* - * Note: PG_tail is an alias of another page flag. The result of PageTail() - * is only valid if PageCompound(page) is true. + * PG_reclaim is used in combination with PG_compound to mark the + * head and tail of a compound page + * + * PG_compound & PG_reclaim => Tail page + * PG_compound & ~PG_reclaim => Head page */ -#define PageTail(page) test_bit(PG_tail, &(page)->flags) -#define __SetPageTail(page) __set_bit(PG_tail, &(page)->flags) -#define __ClearPageTail(page) __clear_bit(PG_tail, &(page)->flags) + +#define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim)) + +#define PageTail(page) ((page->flags & PG_head_tail_mask) \ + == PG_head_tail_mask) + +static inline void __SetPageTail(struct page *page) +{ + page->flags |= PG_head_tail_mask; +} + +static inline void __ClearPageTail(struct page *page) +{ + page->flags &= ~PG_head_tail_mask; +} + +#define PageHead(page) ((page->flags & PG_head_tail_mask) \ + == (1L << PG_compound)) +#define __SetPageHead(page) __SetPageCompound(page) +#define __ClearPageHead(page) __ClearPageCompound(page) #ifdef CONFIG_SWAP #define PageSwapCache(page) test_bit(PG_swapcache, &(page)->flags) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index fc241fe..36d713e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -235,12 +235,11 @@ static void prep_compound_page(struct page *page, unsigned long order) set_compound_page_dtor(page, free_compound_page); set_compound_order(page, order); - __SetPageCompound(page); + __SetPageHead(page); for (i = 1; i < nr_pages; i++) { struct page *p = page + i; __SetPageTail(p); - __SetPageCompound(p); p->first_page = page; } } @@ -253,17 +252,16 @@ static void destroy_compound_page(struct page *page, unsigned long order) if (unlikely(compound_order(page) != order)) bad_page(page); - if (unlikely(!PageCompound(page))) + if (unlikely(!PageHead(page))) bad_page(page); - __ClearPageCompound(page); + __ClearPageHead(page); for (i = 1; i < nr_pages; i++) { struct page *p = page + i; - if (unlikely(!PageCompound(p) | !PageTail(p) | + if (unlikely(!PageTail(p) | (p->first_page != page))) bad_page(page); __ClearPageTail(p); - __ClearPageCompound(p); } } |
