On Wed, 2022-02-09 at 19:26 +0800, Xiongfeng Wang wrote:
> Hi,
>
> On 2022/2/9 17:45, Nicolas Saenz Julienne wrote:
> > Hi Xiongfeng, thanks for taking the time to look at this.
> >
> > On Wed, 2022-02-09 at 16:55 +0800, Xiongfeng Wang wrote:
> > > Hi Nicolas，
> > >
> > > When I applied the patchset on the following commit and tested on QEMU, I came
> > > accross the following CallTrace.
> > > commit dd81e1c7d5fb126e5fbc5c9e334d7b3ec29a16a0
> > >
> > > I wrote a userspace application to consume the memory. When the memory is used
> > > out, the OOM killer is triggered and the following Calltrace is printed. I am
> > > not sure if it is related to this patchset. But when I reverted this patchset,
> > > the 'NULL pointer' Calltrace didn't show.
> >
> > It's a silly mistake on my part, while cleaning up the code I messed up one of
> > the 'struct per_cpu_pages' accessors. This should fix it:
> >
> > ------------------------->8-------------------------
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 0caa7155ca34..e65b991c3dc8 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -3279,7 +3279,7 @@ static void __drain_all_pages(struct zone *zone, bool force_all_cpus)
> > has_pcps = true;
> > } else {
> > for_each_populated_zone(z) {
> > - pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);
> > + pcp = per_cpu_ptr(z->per_cpu_pageset, cpu);
> > lp = rcu_dereference_protected(pcp->lp,
> > mutex_is_locked(&pcpu_drain_mutex));
> > if (lp->count) {
>
> I have tested it. It works well. No more 'NULL pointer' Calltrace.
Thanks!
--
Nicolás Sáenz
