mm/zsmalloc.c: convert to use kmem_cache_zalloc in cache_alloc_zspage()

We always memset the zspage allocated via cache_alloc_zspage.  So it's
more convenient to use kmem_cache_zalloc in cache_alloc_zspage than caller
do it manually.

Link: https://lkml.kernel.org/r/20210114120032.25885-1-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/zsmalloc.c

@@ -357,7 +357,7 @@ static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
 
 static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
 {
-	return kmem_cache_alloc(pool->zspage_cachep,
+	return kmem_cache_zalloc(pool->zspage_cachep,
 			flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
 }
 
@@ -1064,7 +1064,6 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
 	if (!zspage)
 		return NULL;
 
-	memset(zspage, 0, sizeof(struct zspage));
 	zspage->magic = ZSPAGE_MAGIC;
 	migrate_lock_init(zspage);