This commit tries to use kmem_cache_zalloc instead of kmem_cache_alloc/
memset when a new journal head is alloctated.
Signed-off-by: NZheng Liu <wenqing.lz@taobao.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: NJan Kara <jack@suse.cz>