Why is fsync calling fdsync

[ustulation]

Long story short

The fsync code in AIOFile.fsync ends up calling fdsync :

aiofile/aiofile/aio.py

Line 292 in 647da78

return await self.__context.fdsync(self.fileno())

Is there a particular reason for this? I assume fsync and fdatasync have differences under the hood (at OS level) and fsync is slower but more detailed in what it flushes (eg. in BSD systems). For those who care about these details fsync -> fdsync could be unexpected and misleading.

Expected behavior

fsync should call fsync and a new API should be exposed for fdsync which maps to the underlying context's fdsync.

[mosquito]

This offers speed advantages, and if journaling is enabled on the file system, there is significantly small potential risk of data loss.

[ustulation]

The point is:

1. If you expose a well known API that says/means to do x but ends up doing y, that could be categorised as being misleading (of the API).
2. As a library writer, and IMO, you should just expose the functionality and let the users decide on the "significantly small potential risk of data loss", otherwise you are just assuming that all past, current and future users and systems would be unaffected and/or see things the way you see as opposed to what is otherwise the norm (which I think is a flawed premise). For eg. I do millions upon millions of records and checkpoints on an NFS where multiple systems are reading the data (so multiple OSes involved). This runs for weeks and months. At that scale the "small potential" becomes magnified. There have been occasions where the checkpoint was written before the actual data could be persisted before the writer crashed. So if I want my fsyncs to really mean fsyncs and don't want to work out what systems treat those two differently and what's the difference etc I'm unable to do it here.
3. I don't claim to have read or understood your source code thoroughly but it seems you have an underlying facility in place already: https://github.com/mosquito/caio/blob/c2a39f8e3fdb52068a11d1193ed530cd3588e039/caio/abstract.py#L42. This frontend is simply calling the wrong function. Could it not just have fsync call fsync and fdsync call fdsync?