Re: [Qemu-block] [PATCH v3] block/gluster: Handle changed glfs_ftruncate signature

[Jeff Cody]

On Mon, Jul 30, 2018 at 10:07:27AM -0500, Eric Blake wrote:
> On 07/28/2018 02:50 AM, Niels de Vos wrote:
> >>
> >>Part of me wishes that libgfapi had just created a new function
> >>'glfs_ftruncate2', so that existing users don't need to handle the api
> >>change.  But I guess in the grand scheme, not a huge deal either way.
> >
> >Gluster uses versioned symbols, so older binaries will keep working with
> >new libraries. It is (hopefully) rare that existing symbols get updated.
> >We try to send patches for these kind of changes to the projects we know
> >well in advance, reducing the number of surprises.
> 
> >>I can go ahead and add that to the comment in my branch after applying, if
> >>Niels can let me know what that version is/will be (if known).
> >
> >The new glfs_ftruncate() will be part of glusterfs-5 (planned for
> >October). We're changing the numbering scheme, it was expected to come
> >in glusterfs-4.2, but that is a version that never will be released.
> >
> 
> Wait - so you're saying gluster has not yet released the incompatible
> change? Now would be the right time to get rid of the API breakage, before
> you bake it in, rather than relying solely on the versioned symbols to avoid
> an ABI breakage but forcing all clients to compensate to the API breakage.
> 

If this is not yet in a released version of Gluster, I'm not real eager to
pollute the QEMU driver codebase with #ifdef's, especially if there is a
possibility the API change may not actually materialize.

Is there any reason that this change is being approached in a way that
breaks API usage, and is it too late in the Gluster development pipeline to
change that?