[PATCH] Give all architectures a hugetlb_nopage().

If someone maps a hugetlbfs file, then truncates it, then references the part
of the mapping outside the truncation point, they take a pagefault and we end
up hitting hugetlb_nopage().

We want to prevent this from ever happening.  This patch just makes sure that
all architectures have a goes-BUG hugetlb_nopage() to trap it.

arch/i386/mm/hugetlbpage.c

@@ -26,7 +26,6 @@ static long    htlbpagemem;
 int     htlbpage_max;
 static long    htlbzone_pages;
 
-struct vm_operations_struct hugetlb_vm_ops;
 static LIST_HEAD(htlbpage_freelist);
 static spinlock_t htlbpage_lock = SPIN_LOCK_UNLOCKED;
 
@@ -472,7 +471,14 @@ int is_hugepage_mem_enough(size_t size)
 	return 1;
 }
 
-static struct page *hugetlb_nopage(struct vm_area_struct * area, unsigned long address, int unused)
+/*
+ * We cannot handle pagefaults against hugetlb pages at all.  They cause
+ * handle_mm_fault() to try to instantiate regular-sized pages in the
+ * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
+ * this far.
+ */
+static struct page *
+hugetlb_nopage(struct vm_area_struct *vma, unsigned long address, int unused)
 {
 	BUG();
 	return NULL;

arch/ia64/mm/hugetlbpage.c

@@ -18,7 +18,6 @@
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 
-static struct vm_operations_struct hugetlb_vm_ops;
 struct list_head htlbpage_freelist;
 spinlock_t htlbpage_lock = SPIN_LOCK_UNLOCKED;
 extern long htlbpagemem;
@@ -333,6 +332,14 @@ set_hugetlb_mem_size (int count)
 	return (int) htlbzone_pages;
 }
 
+static struct page *
+hugetlb_nopage(struct vm_area_struct *vma, unsigned long address, int unused)
+{
+	BUG();
+	return NULL;
+}
+
 static struct vm_operations_struct hugetlb_vm_ops = {
-	.close =	zap_hugetlb_resources
+	.nopage =	hugetlb_nopage,
+	.close =	zap_hugetlb_resources,
 };

arch/sparc64/mm/hugetlbpage.c

@@ -619,6 +619,14 @@ int set_hugetlb_mem_size(int count)
 	return (int) htlbzone_pages;
 }
 
+static struct page *
+hugetlb_nopage(struct vm_area_struct *vma, unsigned long address, int unused)
+{
+	BUG();
+	return NULL;
+}
+
 static struct vm_operations_struct hugetlb_vm_ops = {
+	.nopage = hugetlb_nopage,
 	.close	= zap_hugetlb_resources,
 };

arch/x86_64/mm/hugetlbpage.c

@@ -25,7 +25,6 @@ static long    htlbpagemem;
 int     htlbpage_max;
 static long    htlbzone_pages;
 
-struct vm_operations_struct hugetlb_vm_ops;
 static LIST_HEAD(htlbpage_freelist);
 static spinlock_t htlbpage_lock = SPIN_LOCK_UNLOCKED;
 
@@ -349,7 +348,8 @@ int hugetlb_report_meminfo(char *buf)
 			HPAGE_SIZE/1024);
 }
 
-static struct page * hugetlb_nopage(struct vm_area_struct * area, unsigned long address, int unused)
+static struct page *
+hugetlb_nopage(struct vm_area_struct *vma, unsigned long address, int unused)
 {
 	BUG();
 	return NULL;