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From Operating System Concepts

Another issue that can affect the performance of I/O is whether writes
to the file system occur synchronously or asynchronously.

Synchronous
writes occur in the order in which the disk subsystem receives them,
and the writes are not buffered. Thus, the calling routine must wait
for the data to reach the disk drive before it can proceed.

In an
asynchronous write, the data are stored in the cache, and control
returns to the caller.

Most writes are asynchronous. However, metadata
writes, among others, can be synchronous. Operating systems frequently
include a flag in the open system call to allow a process to request
that writes be performed synchronously. For example, databases use
this feature for atomic transactions, to assure that data reach stable
storage in the required order.

Is it correct that write() is blocking, and returns when finish writing to the buffer cache, not necessarily to the file?

So is write() asynchronous write by the definition in the quote?

"Operating systems frequently include a flag in the open system call to allow a process to request that writes be performed synchronously." By calling what functions can you achieve synchronous write, and how do you call them?

Thanks.