[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-v4wt.c b/arch/arm/mm/copypage-v4wt.c
index d8ef39503ff0..86c2cfdbde03 100644
--- a/arch/arm/mm/copypage-v4wt.c
+++ b/arch/arm/mm/copypage-v4wt.c
@@ -11,18 +11,17 @@
  *  the only supported cache operation.
  */
 #include <linux/init.h>
-
-#include <asm/page.h>
+#include <linux/highmem.h>
 
 /*
- * ARMv4 optimised copy_user_page
+ * ARMv4 optimised copy_user_highpage
  *
  * Since we have writethrough caches, we don't have to worry about
  * dirty data in the cache.  However, we do have to ensure that
  * subsequent reads are up to date.
  */
-void __attribute__((naked))
-v4wt_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
+static void __attribute__((naked))
+v4wt_copy_user_page(void *kto, const void *kfrom)
 {
 	asm("\
 	stmfd	sp!, {r4, lr}			@ 2\n\
@@ -44,6 +43,18 @@ v4wt_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
 	: "I" (PAGE_SIZE / 64));
 }
 
+void v4wt_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);
+	v4wt_copy_user_page(kto, kfrom);
+	kunmap_atomic(kfrom, KM_USER1);
+	kunmap_atomic(kto, KM_USER0);
+}
+
 /*
  * ARMv4 optimised clear_user_page
  *
@@ -73,5 +84,5 @@ v4wt_clear_user_page(void *kaddr, unsigned long vaddr)
 
 struct cpu_user_fns v4wt_user_fns __initdata = {
 	.cpu_clear_user_page	= v4wt_clear_user_page,
-	.cpu_copy_user_page	= v4wt_copy_user_page,
+	.cpu_copy_user_highpage	= v4wt_copy_user_highpage,
 };