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 <npiggin@suse.de>
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a39b38c..69ed3cb 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -143,6 +143,29 @@
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);