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

Jason Gunthorpe
2019-08-15T00:11:41Z

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 <jgg@ziepe.ca>
> Cc: Ralph Campbell <rcampbell@nvidia.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Balbir Singh <bsingharora@gmail.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Cc: linux-mm@kvack.org
> Signed-off-by: Daniel Vetter <daniel.vetter@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