mm: when migrate_pages returns 0, all pages must have been released

In some cases migrate_pages could return zero while still leaving a few
pages in the pagelist (and some caller wouldn't notice it has to call
putback_lru_pages after commit cf608ac19c ("mm: compaction: fix
COMPACTPAGEFAILED counting")).

Add one missing putback_lru_pages not added by commit cf608ac19c ("mm:
compaction: fix COMPACTPAGEFAILED counting").

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -1419,6 +1419,7 @@ int soft_offline_page(struct page *page, int flags)
 		ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
 								0, true);
 		if (ret) {
+			putback_lru_pages(&pagelist);
 			pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
 				pfn, ret, page->flags);
 			if (ret > 0)

mm/migrate.c

@@ -772,6 +772,7 @@ uncharge:
 unlock:
 	unlock_page(page);
 
+move_newpage:
 	if (rc != -EAGAIN) {
  		/*
  		 * A page that has been migrated has all references
@@ -785,8 +786,6 @@ unlock:
 		putback_lru_page(page);
 	}
 
-move_newpage:
-
 	/*
 	 * Move the new page to the LRU. If migration was not successful
 	 * then this will free the page.