zsmalloc: remove unnecessary insertion/removal of zspage in compaction

In putback_zspage, we don't need to insert a zspage into list of zspage
in size_class again to just fix fullness group. We could do directly
without reinsertion so we could save some instuctions.
Reported-by: NHeesub Shin <heesub.shin@samsung.com>
Signed-off-by: NMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Juneho Choi <juno.choi@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/zsmalloc.c

@@ -1678,14 +1678,14 @@ static struct page *alloc_target_page(struct size_class *class)
 static void putback_zspage(struct zs_pool *pool, struct size_class *class,
 				struct page *first_page)
 {
-	int class_idx;
 	enum fullness_group fullness;
 
 	BUG_ON(!is_first_page(first_page));
 
-	get_zspage_mapping(first_page, &class_idx, &fullness);
+	fullness = get_fullness_group(first_page);
 	insert_zspage(first_page, class, fullness);
-	fullness = fix_fullness_group(class, first_page);
+	set_zspage_mapping(first_page, class->index, fullness);
+
 	if (fullness == ZS_EMPTY) {
 		zs_stat_dec(class, OBJ_ALLOCATED, get_maxobj_per_zspage(
 			class->size, class->pages_per_zspage));