To restate my previous NAK:

A low-level protocol detail like RWF_ZONE_APPEND has absolutely no
business being exposed in the Linux file system interface.

And as mentioned before I think the idea of returning the actual
position written for O_APPEND writes totally makes sense, and actually
is generalizable to all files.  Together with zonefs that gives you a
perfect interface for zone append.

On Thu, Jun 25, 2020 at 10:45:48PM +0530, Kanchan Joshi wrote:

Introduce RWF_ZONE_APPEND flag to represent zone-append.

And no one but us select few even know what zone append is, nevermind
what the detailed semantics are.  If you add a userspace API you need
to very clearly document the semantics inluding errors and corner cases.