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.

[mgorman@suse.de: Updated changelog]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andy Isaacson <adi@hexapodia.org>
Cc: Nai Xia <nai.xia@gmail.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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.