On Wed, Jul 22, 2020 at 12:43:21PM +0000, Johannes Thumshirn wrote: > On 21/07/2020 07:54, Christoph Hellwig wrote: > > On Mon, Jul 20, 2020 at 04:48:50PM +0000, Johannes Thumshirn wrote: > >> On 20/07/2020 15:45, Christoph Hellwig wrote: > >>> On Mon, Jul 20, 2020 at 10:21:18PM +0900, Johannes Thumshirn wrote: > >>>> On a successful completion, the position the data is written to is > >>>> returned via AIO's res2 field to the calling application. > >>> > >>> That is a major, and except for this changelog, undocumented ABI > >>> change. We had the whole discussion about reporting append results > >>> in a few threads and the issues with that in io_uring. So let's > >>> have that discussion there and don't mix it up with how zonefs > >>> writes data. Without that a lot of the boilerplate code should > >>> also go away. > >>> > >> > >> OK maybe I didn't remember correctly, but wasn't this all around > >> io_uring and how we'd report the location back for raw block device > >> access? > > > > Report the write offset. The author seems to be hell bent on making > > it block device specific, but that is a horrible idea as it is just > > as useful for normal file systems (or zonefs). > > After having looked into io_uring I don't this there is anything that > prevents io_uring from picking up the write offset from ki_complete's > res2 argument. As of now io_uring ignores the filed but that can be > changed. Sure. Except for the fact that the io_uring CQE doesn't have space for it. See the currently ongoing discussion on that.. > So the only thing that needs to be done from a zonefs perspective is > documenting the use of res2 and CC linux-aio and linux-abi (including > an update of the io_getevents man page). > > Or am I completely off track now? Yes. We should not have a different ABI just for zonefs. We need to support this feature in a generic way and not as a weird one off for one filesystem and only with the legacy AIO interface. Either way please make sure you properly separate the interface ( using Write vs Zone Append in zonefs) from the interface (returning the actually written offset from appending writes), as they are quite separate issues.
