[IA64] page_not_present fault in region 5 is normal

When copying data from user-space to kernel-space by __copy_user(),
a page_not_present fault sometimes occurs at vmalloced kernel address
because of VHPT pre-fetching.

Ignore the page_not_present fault in ia64_do_page_fault() before
jumping into exception handlers.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/mm/fault.c

@@ -229,9 +229,6 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 		return;
 	}
 
-	if (ia64_done_with_exception(regs))
-		return;
-
 	/*
 	 * Since we have no vma's for region 5, we might get here even if the address is
 	 * valid, due to the VHPT walker inserting a non present translation that becomes
@@ -242,6 +239,9 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 	if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 		return;
 
+	if (ia64_done_with_exception(regs))
+		return;
+
 	/*
 	 * Oops. The kernel tried to access some bad page. We'll have to terminate things
 	 * with extreme prejudice.