[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, 37 insertions, 24 deletions

diff --git a/arch/arm/mm/copypage-v6.c b/arch/arm/mm/copypage-v6.c
index 0e21c0767580..2ea75d0f5048 100644
--- a/arch/arm/mm/copypage-v6.c
+++ b/arch/arm/mm/copypage-v6.c
@@ -10,8 +10,8 @@
 #include <linux/init.h>
 #include <linux/spinlock.h>
 #include <linux/mm.h>
+#include <linux/highmem.h>
 
-#include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/shmparam.h>
 #include <asm/tlbflush.h>
@@ -33,9 +33,16 @@ static DEFINE_SPINLOCK(v6_lock);
  * Copy the user page.  No aliasing to deal with so we can just
  * attack the kernel's existing mapping of these pages.
  */
-static void v6_copy_user_page_nonaliasing(void *kto, const void *kfrom, unsigned long vaddr)
+static void v6_copy_user_highpage_nonaliasing(struct page *to,
+	struct page *from, unsigned long vaddr)
 {
+	void *kto, *kfrom;
+
+	kfrom = kmap_atomic(from, KM_USER0);
+	kto = kmap_atomic(to, KM_USER1);
 	copy_page(kto, kfrom);
+	kunmap_atomic(kto, KM_USER1);
+	kunmap_atomic(kfrom, KM_USER0);
 }
 
 /*
@@ -48,26 +55,32 @@ static void v6_clear_user_page_nonaliasing(void *kaddr, unsigned long vaddr)
 }
 
 /*
- * Copy the page, taking account of the cache colour.
+ * Discard data in the kernel mapping for the new page.
+ * FIXME: needs this MCRR to be supported.
  */
-static void v6_copy_user_page_aliasing(void *kto, const void *kfrom, unsigned long vaddr)
+static void discard_old_kernel_data(void *kto)
 {
-	unsigned int offset = CACHE_COLOUR(vaddr);
-	unsigned long from, to;
-	struct page *page = virt_to_page(kfrom);
-
-	if (test_and_clear_bit(PG_dcache_dirty, &page->flags))
-		__flush_dcache_page(page_mapping(page), page);
-
-	/*
-	 * Discard data in the kernel mapping for the new page.
-	 * FIXME: needs this MCRR to be supported.
-	 */
 	__asm__("mcrr	p15, 0, %1, %0, c6	@ 0xec401f06"
 	   :
 	   : "r" (kto),
 	     "r" ((unsigned long)kto + PAGE_SIZE - L1_CACHE_BYTES)
 	   : "cc");
+}
+
+/*
+ * Copy the page, taking account of the cache colour.
+ */
+static void v6_copy_user_highpage_aliasing(struct page *to,
+	struct page *from, unsigned long vaddr)
+{
+	unsigned int offset = CACHE_COLOUR(vaddr);
+	unsigned long kfrom, kto;
+
+	if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
+		__flush_dcache_page(page_mapping(from), from);
+
+	/* FIXME: not highmem safe */
+	discard_old_kernel_data(page_address(to));
 
 	/*
 	 * Now copy the page using the same cache colour as the
@@ -75,16 +88,16 @@ static void v6_copy_user_page_aliasing(void *kto, const void *kfrom, unsigned lo
 	 */
 	spin_lock(&v6_lock);
 
-	set_pte_ext(TOP_PTE(from_address) + offset, pfn_pte(__pa(kfrom) >> PAGE_SHIFT, PAGE_KERNEL), 0);
-	set_pte_ext(TOP_PTE(to_address) + offset, pfn_pte(__pa(kto) >> PAGE_SHIFT, PAGE_KERNEL), 0);
+	set_pte_ext(TOP_PTE(from_address) + offset, pfn_pte(page_to_pfn(from), PAGE_KERNEL), 0);
+	set_pte_ext(TOP_PTE(to_address) + offset, pfn_pte(page_to_pfn(to), PAGE_KERNEL), 0);
 
-	from = from_address + (offset << PAGE_SHIFT);
-	to   = to_address + (offset << PAGE_SHIFT);
+	kfrom = from_address + (offset << PAGE_SHIFT);
+	kto   = to_address + (offset << PAGE_SHIFT);
 
-	flush_tlb_kernel_page(from);
-	flush_tlb_kernel_page(to);
+	flush_tlb_kernel_page(kfrom);
+	flush_tlb_kernel_page(kto);
 
-	copy_page((void *)to, (void *)from);
+	copy_page((void *)kto, (void *)kfrom);
 
 	spin_unlock(&v6_lock);
 }
@@ -124,14 +137,14 @@ static void v6_clear_user_page_aliasing(void *kaddr, unsigned long vaddr)
 
 struct cpu_user_fns v6_user_fns __initdata = {
 	.cpu_clear_user_page	= v6_clear_user_page_nonaliasing,
-	.cpu_copy_user_page	= v6_copy_user_page_nonaliasing,
+	.cpu_copy_user_highpage	= v6_copy_user_highpage_nonaliasing,
 };
 
 static int __init v6_userpage_init(void)
 {
 	if (cache_is_vipt_aliasing()) {
 		cpu_user.cpu_clear_user_page = v6_clear_user_page_aliasing;
-		cpu_user.cpu_copy_user_page = v6_copy_user_page_aliasing;
+		cpu_user.cpu_copy_user_highpage = v6_copy_user_highpage_aliasing;
 	}
 
 	return 0;