[PATCHv3 2/2] powerpc/pseries: update device tree before ejecting hotplug uevents

[Pingfan Liu]

On Wed, Jul 22, 2020 at 12:57 PM Michael Ellerman <mpe at ellerman.id.au> wrote:
>
> Pingfan Liu <kernelfans at gmail.com> writes:
> > A bug is observed on pseries by taking the following steps on rhel:
>                                                                 ^
>                                                                 RHEL
>
> I assume it happens on mainline too?
Yes, it does.
>
[...]
> > diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> > index 1a3ac3b..def8cb3f 100644
> > --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> > +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> > @@ -372,6 +372,7 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
> >       invalidate_lmb_associativity_index(lmb);
> >       lmb_clear_nid(lmb);
> >       lmb->flags &= ~DRCONF_MEM_ASSIGNED;
> > +     drmem_update_dt();
>
> No error checking?
Hmm, here should be a more careful design. Please see the comment at the end.
>
> >       __remove_memory(nid, base_addr, block_sz);
> >
> > @@ -607,6 +608,7 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
> >
> >       lmb_set_nid(lmb);
> >       lmb->flags |= DRCONF_MEM_ASSIGNED;
> > +     drmem_update_dt();
>
> And here ..
> >
> >       block_sz = memory_block_size_bytes();
> >
> > @@ -625,6 +627,7 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
> >               invalidate_lmb_associativity_index(lmb);
> >               lmb_clear_nid(lmb);
> >               lmb->flags &= ~DRCONF_MEM_ASSIGNED;
> > +             drmem_update_dt();
>
>
> And here ..
>
> >               __remove_memory(nid, base_addr, block_sz);
> >       }
> > @@ -877,9 +880,6 @@ int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
> >               break;
> >       }
> >
> > -     if (!rc)
> > -             rc = drmem_update_dt();
> > -
> >       unlock_device_hotplug();
> >       return rc;
>
> Whereas previously we did check it.

drmem_update_dt() fails iff allocating memory fail. And in the failed
case, even the original code does not roll back the effect of
__add_memory()/__remove_memory().

And I plan to do the following in V4: if drmem_update_dt() fails in
dlpar_add_lmb(), then bails out immediately.

Thanks,
Pingfan