【openEuler-1.0-LTS】pipe "packet" mode行为和主线不一致

对于如下程序，4.19和主线行为不一样：

```
unsigned pipe_size;

static void prepare_pipe(int p[2])
{
	if (pipe2(p, O_DIRECT)) abort();

pipe_size = fcntl(p[1], F_GETPIPE_SZ);
	static char buffer[4096];

/* fill the pipe completely; each pipe_buffer will now have
	   the PIPE_BUF_FLAG_PACKET flag */
	for (unsigned r = pipe_size; r > 0;) {
		unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
		write(p[1], buffer, n);
		r -= n;
	}

for (unsigned r = pipe_size; r > 0;) {
		unsigned n = r > sizeof(buffer) ? sizeof(buffer) : r;
		read(p[0], buffer, n);
		r -= n;
	}
}

int main(int argc, char **argv) {
	char *data_b = malloc(pipe_size);
	int fd, i;
	char ret[5];
	loff_t offs = 0;
	int p[2];

if (!data_b)
		return -ENOMEM;

prepare_pipe(p);
	fd = open("file", O_RDWR | O_TRUNC);
	if (fd < 0) {
		perror("open fail");
		return 0;
	}
	for (i = 0; i < pipe_size; ++i) {
		data_b[i] = i;
	}
	if (write(fd, data_b, pipe_size) != pipe_size) {
		perror("write fail");
		return 0;
	}
	fsync(fd);

/* clear PIPE_BUF_FLAG_PACKET flags */
	splice(fd, &offs, p[1], NULL, pipe_size, 0);

read(p[0], ret, 5);
	printf("%d %d %d %d %d\n", ret[0], ret[1], ret[2], ret[3], ret[4], ret[5]);
	read(p[0], ret, 5);
	printf("%d %d %d %d %d\n", ret[0], ret[1], ret[2], ret[3], ret[4], ret[5]);

close(fd);
	return EXIT_SUCCESS;
}
```

主线运行返回
![输入图片说明](https://images.gitee.com/uploads/images/2022/0309/150703_ab6b1628_8908684.png "屏幕截图.png")
4.19运行返回
![输入图片说明](https://images.gitee.com/uploads/images/2022/0309/150720_7478aea6_8908684.png "屏幕截图.png")

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