diff --git a/Documentation/cachetlb.txt b/Documentation/cachetlb.txt
index 1f312a9..53245c4 100644
--- a/Documentation/cachetlb.txt
+++ b/Documentation/cachetlb.txt
@@ -371,6 +371,18 @@
 	architectures).  For incoherent architectures, it should flush
 	the cache of the page at vmaddr in the current user process.
 
+  void flush_kernel_dcache_page(struct page *page)
+	When the kernel needs to modify a user page is has obtained
+	with kmap, it calls this function after all modifications are
+	complete (but before kunmapping it) to bring the underlying
+	page up to date.  It is assumed here that the user has no
+	incoherent cached copies (i.e. the original page was obtained
+	from a mechanism like get_user_pages()).  The default
+	implementation is a nop and should remain so on all coherent
+	architectures.  On incoherent architectures, this should flush
+	the kernel cache for page (using page_address(page)).
+
+
   void flush_icache_range(unsigned long start, unsigned long end)
   	When the kernel stores into addresses that it will execute
 	out of (eg when loading modules), this function is called.
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 7bd2593..892c4ea 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -13,6 +13,12 @@
 }
 #endif
 
+#ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
+static inline void flush_kernel_dcache_page(struct page *page)
+{
+}
+#endif
+
 #ifdef CONFIG_HIGHMEM
 
 #include <asm/highmem.h>