percpu: refactor the code in pcpu_[de]populate_chunk()

Using break statement at the end of a for loop is confusing,
refactor it by replacing the for loop.
Signed-off-by: NWANG Cong <amwang@redhat.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

mm/percpu.c

@@ -886,11 +886,10 @@ static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
 	int rs, re;
 
 	/* quick path, check whether it's empty already */
-	pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
-		if (rs == page_start && re == page_end)
-			return;
-		break;
-	}
+	rs = page_start;
+	pcpu_next_unpop(chunk, &rs, &re, page_end);
+	if (rs == page_start && re == page_end)
+		return;
 
 	/* immutable chunks can't be depopulated */
 	WARN_ON(chunk->immutable);
@@ -941,11 +940,10 @@ static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
 	int rs, re, rc;
 
 	/* quick path, check whether all pages are already there */
-	pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end) {
-		if (rs == page_start && re == page_end)
-			goto clear;
-		break;
-	}
+	rs = page_start;
+	pcpu_next_pop(chunk, &rs, &re, page_end);
+	if (rs == page_start && re == page_end)
+		goto clear;
 
 	/* need to allocate and map pages, this chunk can't be immutable */
 	WARN_ON(chunk->immutable);