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SubjectRe: [BUG] set_mempolicy(MPOL_INTERLEAV) cause kernel panic
On Fri, 24 Jul 2009 15:51:51 -0700 (PDT)
David Rientjes <rientjes@google.com> wrote:

> On Thu, 16 Jul 2009, David Rientjes wrote:
>
> > numactl --interleave=all simply passes a nodemask with all bits set, so if
> > cpuset_current_mems_allowed includes offline nodes from node_possible_map,
> > then mpol_set_nodemask() doesn't mask them off.
> >
> > Seems like we could handle this strictly in mempolicies without worrying
> > about top_cpuset like in the following?
> > ---
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -194,6 +194,7 @@ static int mpol_new_bind(struct mempolicy *pol, const nodemask_t *nodes)
> > static int mpol_set_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
> > {
> > nodemask_t cpuset_context_nmask;
> > + nodemask_t mems_allowed;
> > int ret;
> >
> > /* if mode is MPOL_DEFAULT, pol is NULL. This is right. */
> > @@ -201,20 +202,21 @@ static int mpol_set_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
> > return 0;
> >
> > VM_BUG_ON(!nodes);
> > + nodes_and(mems_allowed, cpuset_current_mems_allowed,
> > + node_states[N_HIGH_MEMORY]);
> > if (pol->mode == MPOL_PREFERRED && nodes_empty(*nodes))
> > nodes = NULL; /* explicit local allocation */
> > else {
> > if (pol->flags & MPOL_F_RELATIVE_NODES)
> > mpol_relative_nodemask(&cpuset_context_nmask, nodes,
> > - &cpuset_current_mems_allowed);
> > + &mems_allowed);
> > else
> > nodes_and(cpuset_context_nmask, *nodes,
> > - cpuset_current_mems_allowed);
> > + mems_allowed);
> > if (mpol_store_user_nodemask(pol))
> > pol->w.user_nodemask = *nodes;
> > else
> > - pol->w.cpuset_mems_allowed =
> > - cpuset_current_mems_allowed;
> > + pol->w.cpuset_mems_allowed = mems_allowed;
> > }
> >
> > ret = mpol_ops[pol->mode].create(pol,
> >
>
> Should this patch be added to 2.6.31-rc4 to prevent the kernel panic while
> hotplug notifiers are being added to mempolicies?

afaik we don't have a final patch for this. I asked Motohiro-san about
this and he's proposing that we revert the offending change (which one
was it?) if nothing gets fixed soon - the original author is on a
lengthy vacation.


If we _do_ have a patch then can we start again? Someone send out the patch
and let's take a look at it.


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