arc/mm: use helper fault_signal_pending()

Let ARC to use the new helper fault_signal_pending() by moving the signal
check out of the retry logic as standalone.  This should also helps to
simplify the code a bit.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Brian Geffon <bgeffon@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Link: http://lkml.kernel.org/r/20200220155843.9172-1-peterx@redhat.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arc/mm/fault.c

@@ -133,30 +133,22 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 
 	fault = handle_mm_fault(vma, address, flags);
 
-	/*
-	 * Fault retry nuances
-	 */
-	if (unlikely(fault & VM_FAULT_RETRY)) {
-
-		/*
-		 * If fault needs to be retried, handle any pending signals
-		 * first (by returning to user mode).
-		 * mmap_sem already relinquished by core mm for RETRY case
-		 */
-		if (fatal_signal_pending(current)) {
+	/* Quick path to respond to signals */
+	if (fault_signal_pending(fault, regs)) {
 		if (!user_mode(regs))
 			goto no_context;
 		return;
 	}
+
 	/*
-		 * retry state machine
+	 * Fault retry nuances, mmap_sem already relinquished by core mm
 	 */
-		if (flags & FAULT_FLAG_ALLOW_RETRY) {
+	if (unlikely((fault & VM_FAULT_RETRY) &&
+		     (flags & FAULT_FLAG_ALLOW_RETRY))) {
 		flags &= ~FAULT_FLAG_ALLOW_RETRY;
 		flags |= FAULT_FLAG_TRIED;
 		goto retry;
 	}
-	}
 
 bad_area:
 	up_read(&mm->mmap_sem);