[PATCH] ARM: Fix delayed dcache flush for ARMv6 non-aliasing caches

flush_dcache_page() did nothing for these caches, but since they
suffer from I/D cache coherency issues, we need to ensure that data
is written back to RAM.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/fault-armv.c

@@ -77,9 +77,8 @@ static int adjust_pte(struct vm_area_struct *vma, unsigned long address)
 }
 
 static void
-make_coherent(struct vm_area_struct *vma, unsigned long addr, struct page *page, int dirty)
+make_coherent(struct address_space *mapping, struct vm_area_struct *vma, unsigned long addr, unsigned long pfn)
 {
-	struct address_space *mapping = page_mapping(page);
 	struct mm_struct *mm = vma->vm_mm;
 	struct vm_area_struct *mpnt;
 	struct prio_tree_iter iter;
@@ -87,9 +86,6 @@ make_coherent(struct vm_area_struct *vma, unsigned long addr, struct page *page,
 	pgoff_t pgoff;
 	int aliases = 0;
 
-	if (!mapping)
-		return;
-
 	pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
 
 	/*
@@ -115,9 +111,11 @@ make_coherent(struct vm_area_struct *vma, unsigned long addr, struct page *page,
 	if (aliases)
 		adjust_pte(vma, addr);
 	else
-		flush_cache_page(vma, addr, page_to_pfn(page));
+		flush_cache_page(vma, addr, pfn);
 }
 
+void __flush_dcache_page(struct address_space *mapping, struct page *page);
+
 /*
  * Take care of architecture specific things when placing a new PTE into
  * a page table, or changing an existing PTE.  Basically, there are two
@@ -134,29 +132,22 @@ make_coherent(struct vm_area_struct *vma, unsigned long addr, struct page *page,
 void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
 {
 	unsigned long pfn = pte_pfn(pte);
+	struct address_space *mapping;
 	struct page *page;
 
 	if (!pfn_valid(pfn))
 		return;
+
 	page = pfn_to_page(pfn);
-	if (page_mapping(page)) {
+	mapping = page_mapping(page);
+	if (mapping) {
 		int dirty = test_and_clear_bit(PG_dcache_dirty, &page->flags);
 
-		if (dirty) {
-			/*
-			 * This is our first userspace mapping of this page.
-			 * Ensure that the physical page is coherent with
-			 * the kernel mapping.
-			 *
-			 * FIXME: only need to do this on VIVT and aliasing
-			 *        VIPT cache architectures.  We can do that
-			 *	  by choosing whether to set this bit...
-			 */
-			__cpuc_flush_dcache_page(page_address(page));
-		}
+		if (dirty)
+			__flush_dcache_page(mapping, page);
 
 		if (cache_is_vivt())
-			make_coherent(vma, addr, page, dirty);
+			make_coherent(mapping, vma, addr, pfn);
 	}
 }
 

arch/arm/mm/flush.c

@@ -37,13 +37,8 @@ static void flush_pfn_alias(unsigned long pfn, unsigned long vaddr)
 #define flush_pfn_alias(pfn,vaddr)	do { } while (0)
 #endif
 
-static void __flush_dcache_page(struct address_space *mapping, struct page *page)
+void __flush_dcache_page(struct address_space *mapping, struct page *page)
 {
-	struct mm_struct *mm = current->active_mm;
-	struct vm_area_struct *mpnt;
-	struct prio_tree_iter iter;
-	pgoff_t pgoff;
-
 	/*
 	 * Writeback any data associated with the kernel mapping of this
 	 * page.  This ensures that data in the physical page is mutually
@@ -52,24 +47,21 @@ static void __flush_dcache_page(struct address_space *mapping, struct page *page
 	__cpuc_flush_dcache_page(page_address(page));
 
 	/*
-	 * If there's no mapping pointer here, then this page isn't
-	 * visible to userspace yet, so there are no cache lines
-	 * associated with any other aliases.
-	 */
-	if (!mapping)
-		return;
-
-	/*
-	 * This is a page cache page.  If we have a VIPT cache, we
-	 * only need to do one flush - which would be at the relevant
+	 * If this is a page cache page, and we have an aliasing VIPT cache,
+	 * we only need to do one flush - which would be at the relevant
 	 * userspace colour, which is congruent with page->index.
 	 */
-	if (cache_is_vipt()) {
-		if (cache_is_vipt_aliasing())
-			flush_pfn_alias(page_to_pfn(page),
-					page->index << PAGE_CACHE_SHIFT);
-		return;
-	}
+	if (mapping && cache_is_vipt_aliasing())
+		flush_pfn_alias(page_to_pfn(page),
+				page->index << PAGE_CACHE_SHIFT);
+}
+
+static void __flush_dcache_aliases(struct address_space *mapping, struct page *page)
+{
+	struct mm_struct *mm = current->active_mm;
+	struct vm_area_struct *mpnt;
+	struct prio_tree_iter iter;
+	pgoff_t pgoff;
 
 	/*
 	 * There are possible user space mappings of this page:
@@ -116,12 +108,12 @@ void flush_dcache_page(struct page *page)
 {
 	struct address_space *mapping = page_mapping(page);
 
-	if (cache_is_vipt_nonaliasing())
-		return;
-
 	if (mapping && !mapping_mapped(mapping))
 		set_bit(PG_dcache_dirty, &page->flags);
-	else
+	else {
 		__flush_dcache_page(mapping, page);
+		if (mapping && cache_is_vivt())
+			__flush_dcache_aliases(mapping, page);
+	}
 }
 EXPORT_SYMBOL(flush_dcache_page);