ARM: ZERO_PAGE: Avoid flush_dcache_page() for zero page

[linux-2.6-block.git] / arch / arm / mm / flush.c

diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 43474d8752a6bd4909a0fff9c7a68a656ac5f423..82f4b06bf6b4a39774ba43a3fb183fa5501404d2 100644 (file)
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -189,7 +189,16 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p
  */
 void flush_dcache_page(struct page *page)
 {
-       struct address_space *mapping = page_mapping(page);
+       struct address_space *mapping;
+
+       /*
+        * The zero page is never written to, so never has any dirty
+        * cache lines, and therefore never needs to be flushed.
+        */
+       if (page == ZERO_PAGE(0))
+               return;
+
+       mapping = page_mapping(page);
 
 #ifndef CONFIG_SMP
        if (!PageHighMem(page) && mapping && !mapping_mapped(mapping))