[ARM] copypage: provide our own copy_user_highpage()

We used to override the copy_user_page() function.  However, this
is not only inefficient, it also causes additional complexity for
highmem support, since we convert from a struct page to a kernel
direct mapped address and back to a struct page again.

Moreover, with highmem support, we end up pointlessly setting up
kmap entries for pages which we're going to remap.  So, push the
kmapping down into the copypage implementation files where it's
required.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 17 insertions, 6 deletions

diff --git a/arch/arm/mm/copypage-feroceon.c b/arch/arm/mm/copypage-feroceon.c
index c834767..edd7168 100644
--- a/arch/arm/mm/copypage-feroceon.c
+++ b/arch/arm/mm/copypage-feroceon.c
@@ -7,15 +7,14 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
- * This handles copy_user_page and clear_user_page on Feroceon
+ * This handles copy_user_highpage and clear_user_page on Feroceon
  * more optimally than the generic implementations.
  */
 #include <linux/init.h>
+#include <linux/highmem.h>
 
-#include <asm/page.h>
-
-void __attribute__((naked))
-feroceon_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
+static void __attribute__((naked))
+feroceon_copy_user_page(void *kto, const void *kfrom)
 {
 	asm("\
 	stmfd	sp!, {r4-r9, lr}		\n\
@@ -68,6 +67,18 @@ feroceon_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
 	: "I" (PAGE_SIZE));
 }
 
+void feroceon_copy_user_highpage(struct page *to, struct page *from,
+	unsigned long vaddr)
+{
+	void *kto, *kfrom;
+
+	kto = kmap_atomic(to, KM_USER0);
+	kfrom = kmap_atomic(from, KM_USER1);
+	feroceon_copy_user_page(kto, kfrom);
+	kunmap_atomic(kfrom, KM_USER1);
+	kunmap_atomic(kto, KM_USER0);
+}
+
 void __attribute__((naked))
 feroceon_clear_user_page(void *kaddr, unsigned long vaddr)
 {
@@ -95,6 +106,6 @@ feroceon_clear_user_page(void *kaddr, unsigned long vaddr)
 
 struct cpu_user_fns feroceon_user_fns __initdata = {
 	.cpu_clear_user_page	= feroceon_clear_user_page,
-	.cpu_copy_user_page	= feroceon_copy_user_page,
+	.cpu_copy_user_highpage	= feroceon_copy_user_highpage,
 };