mm: vmscan: check if we isolated a compound page during lumpy scan

Properly take into account if we isolated a compound page during the lumpy
scan in reclaim and skip over the tail pages when encountered.  This
corrects the values given to the tracepoint for number of lumpy pages
isolated and will avoid breaking the loop early if compound pages smaller
than the requested allocation size are requested.

[[email protected]: Updated changelog]
Signed-off-by: Andrea Arcangeli <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Reviewed-by: Rik van Riel <[email protected]>
Cc: Dave Jones <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Andy Isaacson <[email protected]>
Cc: Nai Xia <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/vmscan.c

@@ -1196,13 +1196,17 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 				break;
 
 			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
+				unsigned int isolated_pages;
+
 				mem_cgroup_lru_del(cursor_page);
 				list_move(&cursor_page->lru, dst);
-				nr_taken += hpage_nr_pages(cursor_page);
-				nr_lumpy_taken++;
+				isolated_pages = hpage_nr_pages(cursor_page);
+				nr_taken += isolated_pages;
+				nr_lumpy_taken += isolated_pages;
 				if (PageDirty(cursor_page))
-					nr_lumpy_dirty++;
+					nr_lumpy_dirty += isolated_pages;
 				scan++;
+				pfn += isolated_pages - 1;
 			} else {
 				/*
 				 * Check if the page is freed already.