mm, compaction: rename map_pages to split_map_pages

It's non-obvious that high-order free pages are split into order-0 pages
from the function name.  Fix it.

Link: http://lkml.kernel.org/r/20190118175136.31341-6-mgorman@techsingularity.netSigned-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/compaction.c

@@ -66,7 +66,7 @@ static unsigned long release_freepages(struct list_head *freelist)
 	return high_pfn;
 }
 
-static void map_pages(struct list_head *list)
+static void split_map_pages(struct list_head *list)
 {
 	unsigned int i, order, nr_pages;
 	struct page *page, *next;
@@ -644,7 +644,7 @@ isolate_freepages_range(struct compact_control *cc,
 	}
 
 	/* __isolate_free_page() does not map the pages */
-	map_pages(&freelist);
+	split_map_pages(&freelist);
 
 	if (pfn < end_pfn) {
 		/* Loop terminated early, cleanup. */
@@ -1141,7 +1141,7 @@ static void isolate_freepages(struct compact_control *cc)
 	}
 
 	/* __isolate_free_page() does not map the pages */
-	map_pages(freelist);
+	split_map_pages(freelist);
 
 	/*
 	 * Record where the free scanner will restart next time. Either we