Re: [PATCH RFC 5/9] x86, mm: Use cache of page tables

Edgecombe, Rick P
2021-05-07T16:27:42Z

On Thu, 2021-05-06 at 11:24 -0700, Shakeel Butt wrote:
> On Tue, May 4, 2021 at 5:36 PM Rick Edgecombe
> <rick.p.edgecombe@intel.com> wrote:
> >
> [...]
> > +#ifdef CONFIG_PKS_PG_TABLES
> > +struct page *alloc_table(gfp_t gfp)
> > +{
> > +       struct page *table;
> > +
> > +       if (!pks_page_en)
> > +               return alloc_page(gfp);
> > +
> > +       table = get_grouped_page(numa_node_id(), &gpc_pks);
> > +       if (!table)
> > +               return NULL;
> > +
> > +       if (gfp & __GFP_ZERO)
> > +               memset(page_address(table), 0, PAGE_SIZE);
> > +
> > +       if (memcg_kmem_enabled() &&
> > +           gfp & __GFP_ACCOUNT &&
> > +           !__memcg_kmem_charge_page(table, gfp, 0)) {
> > +               free_table(table);
> > +               table = NULL;
> > +       }
> > +
> > +       VM_BUG_ON_PAGE(*(unsigned long *)&table->ptl, table);
>
> table can be NULL due to charge failure.

Argh, yes. Thank you. I'll remove the VM_BUG_ON, it was left
accidentally.