f2fs: cache NULL when both default_acl and acl are NULL

default_acl and acl of newly created inode will be initiated
as ACL_NOT_CACHED in vfs function inode_init_always() and later
will be updated by calling xxx_init_acl() in specific filesystems.
Howerver, when default_acl and acl are NULL then they keep the value
of ACL_NOT_CACHED, this patch tries to cache NULL for acl/default_acl
in this case.
Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Acked-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/acl.c

@@ -397,12 +397,16 @@ int f2fs_init_acl(struct inode *inode, struct inode *dir, struct page *ipage,
 		error = __f2fs_set_acl(inode, ACL_TYPE_DEFAULT, default_acl,
 				       ipage);
 		posix_acl_release(default_acl);
+	} else {
+		inode->i_default_acl = NULL;
 	}
 	if (acl) {
 		if (!error)
 			error = __f2fs_set_acl(inode, ACL_TYPE_ACCESS, acl,
 					       ipage);
 		posix_acl_release(acl);
+	} else {
+		inode->i_acl = NULL;
 	}
 
 	return error;