powerpc/mm/hash: Do a local flush if possible when no batch is active

Currently in hpte_need_flush() if there is no batch pending we always do a
global TLB flush, which is inefficient if the mm has never run on another
thread.

Instead do the same check that __flush_tlb_pending() does and check if a local
flush is sufficient when batch->active is false. Instead of open-coding it we
use mm_is_thread_local().
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
[mpe: Don't use a local, just inline mm_is_thread_local()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/tlb_hash64.c

@@ -93,12 +93,10 @@ void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
 
 	/*
 	 * Check if we have an active batch on this CPU. If not, just
-	 * flush now and return. For now, we don global invalidates
-	 * in that case, might be worth testing the mm cpu mask though
-	 * and decide to use local invalidates instead...
+	 * flush now and return.
 	 */
 	if (!batch->active) {
-		flush_hash_page(vpn, rpte, psize, ssize, 0);
+		flush_hash_page(vpn, rpte, psize, ssize, mm_is_thread_local(mm));
 		put_cpu_var(ppc64_tlb_batch);
 		return;
 	}