From ce0ad7f0952581ba75ab6aee55bb1ed9bb22cf4f Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Wed, 30 Jul 2008 15:23:13 +1000 Subject: powerpc/mm: Lockless get_user_pages_fast() for 64-bit (v3) Implement lockless get_user_pages_fast for 64-bit powerpc. Page table existence is guaranteed with RCU, and speculative page references are used to take a reference to the pages without having a prior existence guarantee on them. Signed-off-by: Nick Piggin Signed-off-by: Dave Kleikamp Signed-off-by: Andrew Morton Signed-off-by: Benjamin Herrenschmidt --- include/linux/pagemap.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'include/linux/pagemap.h') diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index a39b38ccdc9..69ed3cb1197 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -143,6 +143,29 @@ static inline int page_cache_get_speculative(struct page *page) return 1; } +/* + * Same as above, but add instead of inc (could just be merged) + */ +static inline int page_cache_add_speculative(struct page *page, int count) +{ + VM_BUG_ON(in_interrupt()); + +#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU) +# ifdef CONFIG_PREEMPT + VM_BUG_ON(!in_atomic()); +# endif + VM_BUG_ON(page_count(page) == 0); + atomic_add(count, &page->_count); + +#else + if (unlikely(!atomic_add_unless(&page->_count, count, 0))) + return 0; +#endif + VM_BUG_ON(PageCompound(page) && page != compound_head(page)); + + return 1; +} + static inline int page_freeze_refs(struct page *page, int count) { return likely(atomic_cmpxchg(&page->_count, count, 0) == count); -- cgit v1.2.3