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authorNick Piggin <npiggin@suse.de>2008-07-30 15:23:13 +1000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2008-07-30 15:26:54 +1000
commitce0ad7f0952581ba75ab6aee55bb1ed9bb22cf4f (patch)
treebf2a8845a031cb685219db2ddcb3d296b4a9ffab /include/linux
parent7d2a175b9bf6e9422bebe95130a3c79a25ff4602 (diff)
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>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/pagemap.h23
1 files changed, 23 insertions, 0 deletions
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);