[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, 18 insertions, 7 deletions

diff --git a/arch/arm/mm/copypage-v4wb.c b/arch/arm/mm/copypage-v4wb.c
index 230210822961..186a68a794a9 100644
--- a/arch/arm/mm/copypage-v4wb.c
+++ b/arch/arm/mm/copypage-v4wb.c
@@ -8,11 +8,10 @@
  * published by the Free Software Foundation.
  */
 #include <linux/init.h>
-
-#include <asm/page.h>
+#include <linux/highmem.h>
 
 /*
- * ARMv4 optimised copy_user_page
+ * ARMv4 optimised copy_user_highpage
  *
  * We flush the destination cache lines just before we write the data into the
  * corresponding address.  Since the Dcache is read-allocate, this removes the
@@ -21,10 +20,10 @@
  *
  * Note: We rely on all ARMv4 processors implementing the "invalidate D line"
  * instruction.  If your processor does not supply this, you have to write your
- * own copy_user_page that does the right thing.
+ * own copy_user_highpage that does the right thing.
  */
-void __attribute__((naked))
-v4wb_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
+static void __attribute__((naked))
+v4wb_copy_user_page(void *kto, const void *kfrom)
 {
         asm("\
         stmfd   sp!, {r4, lr}                   @ 2\n\
@@ -48,6 +47,18 @@ v4wb_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
         : "I" (PAGE_SIZE / 64));
 }
 
+void v4wb_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);
+        v4wb_copy_user_page(kto, kfrom);
+        kunmap_atomic(kfrom, KM_USER1);
+        kunmap_atomic(kto, KM_USER0);
+}
+
 /*
  * ARMv4 optimised clear_user_page
  *
@@ -79,5 +90,5 @@ v4wb_clear_user_page(void *kaddr, unsigned long vaddr)
 
 struct cpu_user_fns v4wb_user_fns __initdata = {
         .cpu_clear_user_page    = v4wb_clear_user_page,
-        .cpu_copy_user_page     = v4wb_copy_user_page,
+        .cpu_copy_user_highpage = v4wb_copy_user_highpage,
 };