[ryao]

Here is your barrier syscall:

https://www.man7.org/linux/man-pages/man2/sync.2.html

[kragen]

That flushes, just like the fsync() system call mentioned in Luu's post.

[ryao]

It actually writes dirty data and then flushes.

That said, IO barriers in storage are typically synonymous with flushes. For example, the ext4 nobarrier mount option disables flushes.