On Mon, 2022-03-21 at 19:28 -0500, Benjamin Marzinski wrote:
> On Fri, Mar 18, 2022 at 5:33 PM <mwilck@xxxxxxxx> wrote:
> >
> > From: Martin Wilck <mwilck@xxxxxxxx>
> >
> > This callback is be used by multipathd to unblock pending
> > reconfigure requests if a map is removed that multipathd is
> > currently
> > waiting for.
> >
> > Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
> > ---
> > libmultipath/libmultipath.version | 3 ++-
> > libmultipath/structs_vec.c | 6 ++++++
> > 2 files changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/libmultipath/libmultipath.version
> > b/libmultipath/libmultipath.version
> > index 216f0ee..8132df7 100644
> > --- a/libmultipath/libmultipath.version
> > +++ b/libmultipath/libmultipath.version
> > @@ -31,7 +31,7 @@
> > * The new version inherits the previous ones.
> > */
> >
> > -LIBMULTIPATH_14.0.0 {
> > +LIBMULTIPATH_14.1.0 {
> > global:
> > /* symbols referenced by multipath and multipathd */
> > add_foreign;
> > @@ -164,6 +164,7 @@ global:
> > remember_wwid;
> > remove_map;
> > remove_map_by_alias;
> > + remove_map_callback;
> > remove_maps;
> > remove_wwid;
> > replace_wwids;
> > diff --git a/libmultipath/structs_vec.c
> > b/libmultipath/structs_vec.c
> > index 6c23df8..a69f064 100644
> > --- a/libmultipath/structs_vec.c
> > +++ b/libmultipath/structs_vec.c
> > @@ -336,11 +336,17 @@ void set_path_removed(struct path *pp)
> > pp->initialized = INIT_REMOVED;
> > }
> >
> > +void remove_map_callback(struct multipath *mpp
> > __attribute__((unused)))
> > +{
> > +}
> > +
>
> Does this work? I thought that unless you specifically declared the
> symbol weak, the call in remove_map() would have already gotten
> resolved to point to the existing remove_map_callback() when the
> shared library was getting created. Is it because the function is
> empty? Am I just misunderstanding something?
This works because I added the symbol to libmultipath.version,
assigning it "global" visibility. To be consistent, we could do the
same thing with get_multipath_config() et al., but I didn't want to
change that just now.
We (or actually, users and distro integrators) have to be somewhat
careful with adding linker flags. As discussed e.g. in
https://github.com/opensvc/multipath-tools/issues/26
flags like "-Bsymbolic-functions" would mess this up, because this flag
overrides the settings from our linker script. But declaring the symbol
"weak" wouldn't protect against -Bsymbolic mess-up, either.
I had a long discussion with our toolchain experts about this, which
lead to the conclusion above. I am pretty positive about it.
Feel free to ask the RH experts, too ;-)
Regards
Martin
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