linux-kernel - Re: [PATCH 5/5] mm/hmm: WARN on illegal ->sync_cpu_device

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Message-ID: <20190815071415.GD7444@phenom.ffwll.local>
Date:   Thu, 15 Aug 2019 09:14:15 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Balbir Singh <bsingharora@...il.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 5/5] mm/hmm: WARN on illegal ->sync_cpu_device_pagetables
 errors

On Wed, Aug 14, 2019 at 09:11:37PM -0300, Jason Gunthorpe wrote:
> 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@...pe.ca>
> > Cc: Ralph Campbell <rcampbell@...dia.com>
> > Cc: John Hubbard <jhubbard@...dia.com>
> > Cc: Dan Williams <dan.j.williams@...el.com>
> > Cc: Dan Carpenter <dan.carpenter@...cle.com>
> > Cc: Matthew Wilcox <willy@...radead.org>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Balbir Singh <bsingharora@...il.com>
> > Cc: Ira Weiny <ira.weiny@...el.com>
> > Cc: Souptick Joarder <jrdr.linux@...il.com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: "Jérôme Glisse" <jglisse@...hat.com>
> > Cc: linux-mm@...ck.org
> > Signed-off-by: Daniel Vetter <daniel.vetter@...el.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?

Very much possible, I think I didn't rebase this to linux-next before
resending ... have an

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

in case you need.

Cheers, Daniel

> 
> 	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

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch