Re: [PATCH 10/11] libmpathpersist: add linker version script

[Benjamin Marzinski <bmarzins@redhat.com>]

On Sat, Sep 26, 2020 at 01:07:34AM +0200, Martin Wilck wrote:
> On Fri, 2020-09-25 at 17:32 -0500, Benjamin Marzinski wrote:
> > On Fri, Sep 25, 2020 at 05:10:22PM -0500, Benjamin Marzinski wrote:
> > > On Fri, Sep 25, 2020 at 09:52:51PM +0200, Martin Wilck wrote:
> > > > On Thu, 2020-09-24 at 23:00 -0500, Benjamin Marzinski wrote:
> > > > > On Thu, Sep 24, 2020 at 03:36:43PM +0200, mwilck@suse.com
> > > > > wrote:
> > > > > > --- /dev/null
> > > > > > +++ b/libmpathpersist/libmpathpersist.version
> > > > > > @@ -0,0 +1,20 @@
> > > > > > +LIBMPATHPERSIST_0.8.4.0 {
> > > > > 
> > > > > I have a question about this version. Do you plan on bumping
> > > > > this
> > > > > each
> > > > > time a new release is tagged? It seems like we only ever want
> > > > > to
> > > > > change
> > > > > the version if we actually change the ABI. Or is 0.8.4 just
> > > > > because
> > > > > that's the relesae where we started this?
> > > > 
> > > > That was the idea, yes. And the last digit is because we'll have
> > > > to
> > > > bump it between releases from Christophe. It makes sense for
> > > > libmultipath's rapidly changing ABI; much less so for libmpathcmd
> > > > and
> > > > libmpathpersist, which are meant to be stable. I am open for
> > > > discussing
> > > > these numbers; if you prefer, we might as well use
> > > > LIBMPATHPERSIST_1.0.
> > > > 
> > > > I admit I haven't thought about what would happen once Christophe
> > > > makes
> > > > a new release. Probably, nothing - afaics it's impossible to add
> > > > a new
> > > > version without any new symbols, and *renaming* an existing
> > > > version is
> > > > bad; it would introduce artificial incompatibility. 
> > > > 
> > > > So libmultipath from multipath-tools 0.8.5 would still have a
> > > > 0.8.4.x
> > > > ABI; only the first change after 0.8.5 would get a 0.8.5.1
> > > > number. Hm.
> > > > 
> > > > Again, I'm open for discussion here. We might as well choose to
> > > > not tie
> > > > the ABI version to the libmultipath version at all, and simply
> > > > start at
> > > > 0.1 or whatevever for libmultipath. After all, looking up the ABI
> > > > version in the commit history will be simple enough.
> > > 
> > > Since the ABI version isn't always going to match the release
> > > version, I
> > > think it makes more sense to decouple them, so it's not sometimes
> > > matching and sometimes not. We could go with a MAJOR.MINOR
> > > versioning
> > > scheme, where we bump MINOR whenever we change the interface in a
> > > backwards compatible way (like by adding a new symbol), and bump
> > > the
> > > MAJOR and reset the MINOR whenever we change the interface in a
> > > non-backwards compatible way (like by changing the parameters an
> > > interface function takes, or removing a symbol).
> > 
> > Perhaps we might even want MAJOR.MINOR.RELEASE, where for upstream,
> > RELEASE is always 0. Distros can increment it if they need to
> > backport
> > changes, so that they don't conflict with existing upstream versions.
> 
> Sounds good. What MAJOR.MINOR version should we start with? 0.1 ? 1.0?

I realize that multipath-tools doesn't actually have a 1.0 release, but
1.0+ releases tradiontially mean that you believe that it's stable and
ready for use. Setting the libraries to 0.1 says to me that they aren't
meant for serious use, so I would vote for 1.0.

cc-ing dm-devel, because apparently I forgot to on my last email.

-Ben
 
> Martin
>