remove mmu notifier calls in apply_to_page_range

It is not appropriate for apply_to_page_range() to directly call any mmu notifiers, because it is a general purpose function whose effect depends on what context it is called in and what the callback function does.

In particular, if it is being used as part of an mmu notifier implementation, the recursive calls can be particularly problematic.

It is up to apply_to_page_range's caller to do any notifier calls if necessary. It does not affect any in-tree users because they all operate on init_mm, and mmu notifiers only pertain to usermode mappings.

index 6ab19dd..d6b89eb 100644
@@ -1890,7 +1890,6 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
 	int err;
 
 	BUG_ON(addr >= end);
-	mmu_notifier_invalidate_range_start(mm, start, end);
 	pgd = pgd_offset(mm, addr);
 	do {
 		next = pgd_addr_end(addr, end);

@@ -1898,7 +1897,7 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
 		if (err)
 			break;
 	} while (pgd++, addr = next, addr != end);
-	mmu_notifier_invalidate_range_end(mm, start, end);
+
 	return err;
 }
 EXPORT_SYMBOL_GPL(apply_to_page_range);