x86: Move do_page_fault()'s error path under unlikely()

Ingo suggested SIGKILL check should be moved into slowpath
function. This will reduce the page fault fastpath impact
of this recent commit:

37b23e0525d3: x86,mm: make pagefault killable

Suggested-by: Ingo Molnar <[e-mail]>
Signed-off-by: KOSAKI Motohiro <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: Andrew Morton <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/mm/fault.c

···
 	force_sig_info_fault(SIGBUS, code, address, tsk, fault);
 }
 
-static noinline void
+static noinline int
 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 	       unsigned long address, unsigned int fault)
 {
+	/*
+	 * Pagefault was interrupted by SIGKILL. We have no reason to
+	 * continue pagefault.
+	 */
+	if (fatal_signal_pending(current)) {
+		if (!(fault & VM_FAULT_RETRY))
+			up_read(&current->mm->mmap_sem);
+		if (!(error_code & PF_USER))
+			no_context(regs, error_code, address);
+		return 1;
+	}
+	if (!(fault & VM_FAULT_ERROR))
+		return 0;
+
 	if (fault & VM_FAULT_OOM) {
 		/* Kernel mode? Handle exceptions or die: */
 		if (!(error_code & PF_USER)) {
 			up_read(&current->mm->mmap_sem);
 			no_context(regs, error_code, address);
-			return;
+			return 1;
 		}
 
 		out_of_memory(regs, error_code, address);
···
 		else
 			BUG();
 	}
+	return 1;
 }
 
 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
···
 	 */
 	fault = handle_mm_fault(mm, vma, address, flags);
 
-	if (unlikely(fault & VM_FAULT_ERROR)) {
-		mm_fault_error(regs, error_code, address, fault);
-		return;
-	}
-
-	/*
-	 * Pagefault was interrupted by SIGKILL. We have no reason to
-	 * continue pagefault.
-	 */
-	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
-		if (!(error_code & PF_USER))
-			no_context(regs, error_code, address);
-		return;
+	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
+		if (mm_fault_error(regs, error_code, address, fault))
+			return;
 	}
 
 	/*