Re: [PATCH 5/5] mm/hmm: WARN on illegal ->sync_cpu_device_pagetables errors

[Jason Gunthorpe]

On Wed, Aug 14, 2019 at 10:20:27PM +0200, Daniel Vetter wrote:
> Similar to the warning in the mmu notifer, warning if an hmm mirror
> callback gets it's blocking vs. nonblocking handling wrong, or if it
> fails with anything else than -EAGAIN.
> 
> Cc: Jason Gunthorpe <j...@ziepe.ca>
> Cc: Ralph Campbell <rcampb...@nvidia.com>
> Cc: John Hubbard <jhubb...@nvidia.com>
> Cc: Dan Williams <dan.j.willi...@intel.com>
> Cc: Dan Carpenter <dan.carpen...@oracle.com>
> Cc: Matthew Wilcox <wi...@infradead.org>
> Cc: Arnd Bergmann <a...@arndb.de>
> Cc: Balbir Singh <bsinghar...@gmail.com>
> Cc: Ira Weiny <ira.we...@intel.com>
> Cc: Souptick Joarder <jrdr.li...@gmail.com>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: "Jérôme Glisse" <jgli...@redhat.com>
> Cc: linux...@kvack.org
> Signed-off-by: Daniel Vetter <daniel.vet...@intel.com>
>  mm/hmm.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 16b6731a34db..52ac59384268 100644
> +++ b/mm/hmm.c
> @@ -205,6 +205,9 @@ static int hmm_invalidate_range_start(struct mmu_notifier 
> *mn,
>                       ret = -EAGAIN;
>                       break;
>               }
> +             WARN(ret, "%pS callback failed with %d in %sblockable 
> context\n",
> +                  mirror->ops->sync_cpu_device_pagetables, ret,
> +                  update.blockable ? "" : "non-");
>       }
>       up_read(&hmm->mirrors_sem);

Didn't I beat you to this?

        list_for_each_entry(mirror, &hmm->mirrors, list) {
                int rc;

                rc = mirror->ops->sync_cpu_device_pagetables(mirror, &update);
                if (rc) {
                        if (WARN_ON(update.blockable || rc != -EAGAIN))
                                continue;
                        ret = -EAGAIN;
                        break;
                }
        }

Thanks,
Jason