2 files changed, 18 insertions, 0 deletions

diff --git a/Documentation/cachetlb.txt b/Documentation/cachetlb.txt
index 1f312a9893d9..53245c429f7d 100644
--- a/Documentation/cachetlb.txt
+++ b/Documentation/cachetlb.txt
@@ -371,6 +371,18 @@ maps this page at its virtual address.
         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 7bd2593dbef9..892c4ea1b425 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -13,6 +13,12 @@ static inline void flush_anon_page(struct page *page, unsigned long vmaddr)
 }
 #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>