Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux…

…/kernel/git/tip/tip into next

Pull x86 mm update from Ingo Molnar:

 - speed up 256 GB PCI BAR ioremap()s

 - speed up PTE swapout page reclaim case

* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, ioremap: Speed up check for RAM pages
  x86/mm: In the PTE swapout page reclaim case clear the accessed bit instead of flushing the TLB

arch/x86/mm/ioremap.c

@@ -50,6 +50,21 @@ int ioremap_change_attr(unsigned long vaddr, unsigned long size,
 	return err;
 }
 
+static int __ioremap_check_ram(unsigned long start_pfn, unsigned long nr_pages,
+			       void *arg)
+{
+	unsigned long i;
+
+	for (i = 0; i < nr_pages; ++i)
+		if (pfn_valid(start_pfn + i) &&
+		    !PageReserved(pfn_to_page(start_pfn + i)))
+			return 1;
+
+	WARN_ONCE(1, "ioremap on RAM pfn 0x%lx\n", start_pfn);
+
+	return 0;
+}
+
 /*
  * Remap an arbitrary physical address space into the kernel virtual
  * address space. Needed when the kernel wants to access high addresses
@@ -93,14 +108,11 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 	/*
 	 * Don't allow anybody to remap normal RAM that we're using..
 	 */
+	pfn      = phys_addr >> PAGE_SHIFT;
 	last_pfn = last_addr >> PAGE_SHIFT;
-	for (pfn = phys_addr >> PAGE_SHIFT; pfn <= last_pfn; pfn++) {
-		int is_ram = page_is_ram(pfn);
-
-		if (is_ram && pfn_valid(pfn) && !PageReserved(pfn_to_page(pfn)))
-			return NULL;
-		WARN_ON_ONCE(is_ram);
-	}
+	if (walk_system_ram_range(pfn, last_pfn - pfn + 1, NULL,
+				  __ioremap_check_ram) == 1)
+		return NULL;
 
 	/*
 	 * Mappings have to be page-aligned

arch/x86/mm/pgtable.c

@@ -399,13 +399,20 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 int ptep_clear_flush_young(struct vm_area_struct *vma,
 			   unsigned long address, pte_t *ptep)
 {
-	int young;
-
-	young = ptep_test_and_clear_young(vma, address, ptep);
-	if (young)
-		flush_tlb_page(vma, address);
-
-	return young;
+	/*
+	 * On x86 CPUs, clearing the accessed bit without a TLB flush
+	 * doesn't cause data corruption. [ It could cause incorrect
+	 * page aging and the (mistaken) reclaim of hot pages, but the
+	 * chance of that should be relatively low. ]
+	 *
+	 * So as a performance optimization don't flush the TLB when
+	 * clearing the accessed bit, it will eventually be flushed by
+	 * a context switch or a VM operation anyway. [ In the rare
+	 * event of it not getting flushed for a long time the delay
+	 * shouldn't really matter because there's no real memory
+	 * pressure for swapout to react to. ]
+	 */
+	return ptep_test_and_clear_young(vma, address, ptep);
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE