[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, 7 deletions

diff --git a/arch/arm/mm/copypage-xsc3.c b/arch/arm/mm/copypage-xsc3.c
index 51ed502e577..caa697ccd8d 100644
--- a/arch/arm/mm/copypage-xsc3.c
+++ b/arch/arm/mm/copypage-xsc3.c
@@ -11,8 +11,7 @@
  * Author: Matt Gilbert (matthew.m.gilbert@intel.com)
  */
 #include <linux/init.h>
-
-#include <asm/page.h>
+#include <linux/highmem.h>
 
 /*
  * General note:
@@ -21,18 +20,17 @@
  */
 
 /*
- * XSC3 optimised copy_user_page
+ * XSC3 optimised copy_user_highpage
  *  r0 = destination
  *  r1 = source
- *  r2 = virtual user address of ultimate destination page
  *
  * The source page may have some clean entries in the cache already, but we
  * can safely ignore them - break_cow() will flush them out of the cache
  * if we eventually end up using our copied page.
  *
  */
-void __attribute__((naked))
-xsc3_mc_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
+static void __attribute__((naked))
+xsc3_mc_copy_user_page(void *kto, const void *kfrom)
 {
 	asm("\
 	stmfd	sp!, {r4, r5, lr}		\n\
@@ -72,6 +70,18 @@ xsc3_mc_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
 	: "I" (PAGE_SIZE / 64 - 1));
 }
 
+void xsc3_mc_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);
+	xsc3_mc_copy_user_page(kto, kfrom);
+	kunmap_atomic(kfrom, KM_USER1);
+	kunmap_atomic(kto, KM_USER0);
+}
+
 /*
  * XScale optimised clear_user_page
  *  r0 = destination
@@ -98,5 +108,5 @@ xsc3_mc_clear_user_page(void *kaddr, unsigned long vaddr)
 
 struct cpu_user_fns xsc3_mc_user_fns __initdata = {
 	.cpu_clear_user_page	= xsc3_mc_clear_user_page,
-	.cpu_copy_user_page	= xsc3_mc_copy_user_page,
+	.cpu_copy_user_highpage	= xsc3_mc_copy_user_highpage,
 };