Re: [PATCH] mm/page_alloc: do bulk array bounds check after checking populated elements

Mel Gorman
2021-06-28T15:29:09Z

On Mon, Jun 28, 2021 at 10:48:05AM -0400, Dave Jones wrote:
> On Mon, Jun 28, 2021 at 12:53:23PM +0100, Mel Gorman wrote:
>
> > > This made it into 5.13 final, and completely breaks NFSD for me (Serving tcp v3 mounts).
> > > Existing mounts on clients hang, as do new mounts from new clients.
> > > Rebooting the server back to rc7 everything recovers. Bisect lands on
> > > this commit.
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index ef2265f86b91..04220581579c 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -5058,7 +5058,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
> >
> > /* Already populated array? */
> > if (unlikely(page_array && nr_pages - nr_populated == 0))
> > - return 0;
> > + return nr_populated;
>
> Yep, this works.
>

Thanks Dave, it passed a dbench test over NFS locally as well so I sent
a proper version of the patch. Hopefully it'll be picked up relatively
quickly and appear in a 5.13.1 release.

--
Mel Gorman
SUSE Labs