On Tue, 25 Aug 2009, Lee Schermerhorn wrote:
> > > Index: linux-2.6.31-rc6-mmotm-090820-1918/mm/hugetlb.c
> > > ===================================================================
> > > --- linux-2.6.31-rc6-mmotm-090820-1918.orig/mm/hugetlb.c 2009-08-24 12:12:50.000000000 -0400
> > > +++ linux-2.6.31-rc6-mmotm-090820-1918/mm/hugetlb.c 2009-08-24 12:12:53.000000000 -0400
> > > @@ -1257,10 +1257,13 @@ static int adjust_pool_surplus(struct hs
> > > static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count)
> > > {
> > > unsigned long min_count, ret;
> > > + nodemask_t *nodes_allowed;
> > >
> > > if (h->order >= MAX_ORDER)
> > > return h->max_huge_pages;
> > >
> >
> > Why can't you simply do this?
> >
> > struct mempolicy *pol = NULL;
> > nodemask_t *nodes_allowed = &node_online_map;
> >
> > local_irq_disable();
> > pol = current->mempolicy;
> > mpol_get(pol);
> > local_irq_enable();
> > if (pol) {
> > switch (pol->mode) {
> > case MPOL_BIND:
> > case MPOL_INTERLEAVE:
> > nodes_allowed = pol->v.nodes;
> > break;
> > case MPOL_PREFERRED:
> > ... use NODEMASK_SCRATCH() ...
> > default:
> > BUG();
> > }
> > }
> > mpol_put(pol);
> >
> > and then use nodes_allowed throughout set_max_huge_pages()?
>
>
> Well, I do use nodes_allowed [pointer] throughout set_max_huge_pages().
Yeah, the above code would all be in set_max_huge_pages() and
huge_mpol_nodes_allowed() would be removed.
> NODEMASK_SCRATCH() didn't exist when I wrote this, and I can't be sure
> it will return a kmalloc()'d nodemask, which I need because a NULL
> nodemask pointer means "all online nodes" [really all nodes with memory,
> I suppose] and I need a pointer to kmalloc()'d nodemask to return from
> huge_mpol_nodes_allowed(). I want to keep the access to the internals
> of mempolicy in mempolicy.[ch], thus the call out to
> huge_mpol_nodes_allowed(), instead of open coding it.
Ok, so you could add a mempolicy.c helper function that returns
nodemask_t * and either points to mpol->v.nodes for most cases after
getting a reference on mpol with mpol_get() or points to a dynamically
allocated NODEMASK_ALLOC() on a nodemask created for MPOL_PREFERRED.
This works nicely because either way you still have a reference to mpol,
so you'll need to call into a mpol_nodemask_free() function which can use
the same switch statement:
void mpol_nodemask_free(struct mempolicy *mpol,
struct nodemask_t *nodes_allowed)
{
switch (mpol->mode) {
case MPOL_PREFERRED:
kfree(nodes_allowed);
break;
default:
break;
}
mpol_put(mpol);
}
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