Re: [PATCHv4 2/2] powerpc/pseries: update device tree before ejecting hotplug uevents

[Pingfan Liu <kernelfans@gmail.com>]

On Tue, Aug 4, 2020 at 12:29 AM Laurent Dufour <ldufour@linux.ibm.com> wrote:
>
[...]
> >       lmb_set_nid(lmb);
> >       lmb->flags |= DRCONF_MEM_ASSIGNED;
> > +     if (dt_update) {
> > +             ret = drmem_update_dt();
> > +             if (ret)
> > +                     pr_warn("%s fail to update dt, but continue\n", __func__);
> > +     }
> >
> >       block_sz = memory_block_size_bytes();
>
> In the case the call to __add_memory is failing, the flag DRCONF_MEM_ASSIGNED
> should be cleared as I mentioned in your previous patch. In addition to this,
Yes.
> the DT should be updated, or the caller should manage that but that will be hard
> since it doesn't know where the error happened in this function.
Yeah, it is hard to manage it by caller, so just updating dt  is a
easier method.
>
> >
> > @@ -625,7 +653,11 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
> >               invalidate_lmb_associativity_index(lmb);
> >               lmb_clear_nid(lmb);
> >               lmb->flags &= ~DRCONF_MEM_ASSIGNED;
> > -
> > +             if (dt_update) {
> > +                     ret = drmem_update_dt();
> > +                     if (ret)
> > +                             pr_warn("%s fail to update dt during rollback, but continue\n", __func__);
> > +             }
> >               __remove_memory(nid, base_addr, block_sz);
> >       }
> >
> > @@ -638,6 +670,7 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
> >       int lmbs_available = 0;
> >       int lmbs_added = 0;
> >       int rc;
> > +     bool dt_update = false;
> >
> >       pr_info("Attempting to hot-add %d LMB(s)\n", lmbs_to_add);
> >
> > @@ -664,7 +697,7 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
> >               if (rc)
> >                       continue;
> >
> > -             rc = dlpar_add_lmb(lmb);
> > +             rc = dlpar_add_lmb(lmb, dt_update);
> >               if (rc) {
> >                       dlpar_release_drc(lmb->drc_index);
> >                       continue;
> > @@ -678,16 +711,23 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
> >               lmbs_added++;
> >               if (lmbs_added == lmbs_to_add)
> >                       break;
> > +             else if (lmbs_added == lmbs_to_add - 1)
> > +                     dt_update = true;
>
> In the case the number of LMB to add is 1, dt_update is never set to true, and
> the device tree is never updated. You need to set dt_update to true earlier in
> the loop block.
Oh, I will fix it in V5
>
> >       }
> >
> >       if (lmbs_added != lmbs_to_add) {
> > +             bool rollback_dt_update = false;
> > +
> >               pr_err("Memory hot-add failed, removing any added LMBs\n");
> >
> >               for_each_drmem_lmb(lmb) {
> >                       if (!drmem_lmb_reserved(lmb))
> >                               continue;
> >
> > -                     rc = dlpar_remove_lmb(lmb);
> > +                     if (--lmbs_added == 0 && dt_update)
> > +                             rollback_dt_update = true;
>
> That test may have to be review to deal with error during the last LMB addition,
> the DT may have been updated before __add_memory() is failing in
> dlpar_add_lmb(). In that case, lmbs_added == 0 and that branch is not covered.
> That's not an issue if dlpar_add_lmb() is handling that case (see my comment above).
I will fix it in next version.

Thanks for your review.

Regards,
Pingfan