flags中必须access mode：O_RDONLY, O_WRONLY, O_RDWR其中之一；© XXX Page 4 of 23 文件创建标志只影响打开操作, 文件状态标志影响后面的读写操作 file creation flags: O_CLOEXEC, O_CREAT, O_DIRECTORY, O_EXCL, O_NOCTTY, O_NOFOLLOW, O_TMPFILE, and O_TRUNC file XXX Page 6 of 23 Open a file Open flags are available in fi->flags. The following rules apply. Creation (O_CREAT, O_EXCL, O_NOCTTY) flags will be filtered out / handled by the kernel. Access modes (O_RDONLY