btrfs: use KMEM_CACHE() to create btrfs_ordered_extent cache

Use the KMEM_CACHE() macro instead of kmem_cache_create() to simplify
the creation of SLAB caches when the default values are used.

Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: KunWuChan

fs/btrfs/ordered-data.c

@@ -1235,10 +1235,7 @@ struct btrfs_ordered_extent *btrfs_split_ordered_extent(
 
 int __init ordered_data_init(void)
 {
-	btrfs_ordered_extent_cache = kmem_cache_create("btrfs_ordered_extent",
-				     sizeof(struct btrfs_ordered_extent), 0,
-				     SLAB_MEM_SPREAD,
-				     NULL);
+	btrfs_ordered_extent_cache = KMEM_CACHE(btrfs_ordered_extent, SLAB_MEM_SPREAD);
 	if (!btrfs_ordered_extent_cache)
 		return -ENOMEM;