MIPS: Fix get_user_page_fast() for mips with cache alias

get_user_pages_fast() is missing cache flushes for MIPS platforms with
cache aliases.  Filesystem failures observed with DirectIO operations due
to missing flush_anon_page() that use page coloring logic to work with
cache aliases. This fix falls through to take slow_irqon path that calls
get_user_pages() that has required logic for platforms where
cpu_has_dc_aliases is true.

[ralf@linux-mips.org: Explicity include <asm/cpu-features.h>.]

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/5469/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
(cherry picked from commit 66827eb0c0738e50b7cd76815f23e41b1cd4bd8b)
diff --git a/arch/mips/mm/gup.c b/arch/mips/mm/gup.c
index dcfd573..0c832ea 100644
--- a/arch/mips/mm/gup.c
+++ b/arch/mips/mm/gup.c
@@ -12,6 +12,7 @@
 #include <linux/swap.h>
 #include <linux/hugetlb.h>
 
+#include <asm/cpu-features.h>
 #include <asm/pgtable.h>
 
 static inline pte_t gup_get_pte(pte_t *ptep)
@@ -273,7 +274,7 @@
 	len = (unsigned long) nr_pages << PAGE_SHIFT;
 
 	end = start + len;
-	if (end < start)
+	if (end < start || cpu_has_dc_aliases)
 		goto slow_irqon;
 
 	/* XXX: batch / limit 'nr' */