Re: [PATCH 16/25] device-dax: use the dev_pagemap internal refcount

[Dan Williams]

On Fri, Jun 28, 2019 at 11:29 AM Jason Gunthorpe <jgg@xxxxxxxxxxxx> wrote:
>
> On Fri, Jun 28, 2019 at 10:10:12AM -0700, Dan Williams wrote:
> > On Fri, Jun 28, 2019 at 10:08 AM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> > >
> > > On Fri, Jun 28, 2019 at 10:02 AM Jason Gunthorpe <jgg@xxxxxxxxxxxx> wrote:
> > > >
> > > > On Fri, Jun 28, 2019 at 09:27:44AM -0700, Dan Williams wrote:
> > > > > On Fri, Jun 28, 2019 at 8:39 AM Jason Gunthorpe <jgg@xxxxxxxxxxxx> wrote:
> > > > > >
> > > > > > On Wed, Jun 26, 2019 at 02:27:15PM +0200, Christoph Hellwig wrote:
> > > > > > > The functionality is identical to the one currently open coded in
> > > > > > > device-dax.
> > > > > > >
> > > > > > > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > > > > > > Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> > > > > > >  drivers/dax/dax-private.h |  4 ----
> > > > > > >  drivers/dax/device.c      | 43 ---------------------------------------
> > > > > > >  2 files changed, 47 deletions(-)
> > > > > >
> > > > > > DanW: I think this series has reached enough review, did you want
> > > > > > to ack/test any further?
> > > > > >
> > > > > > This needs to land in hmm.git soon to make the merge window.
> > > > >
> > > > > I was awaiting a decision about resolving the collision with Ira's
> > > > > patch before testing the final result again [1]. You can go ahead and
> > > > > add my reviewed-by for the series, but my tested-by should be on the
> > > > > final state of the series.
> > > >
> > > > The conflict looks OK to me, I think we can let Andrew and Linus
> > > > resolve it.
> > >
> > > Andrew's tree effectively always rebases since it's a quilt series.
> > > I'd recommend pulling Ira's patch out of -mm and applying it with the
> > > rest of hmm reworks. Any other git tree I'd agree with just doing the
> > > late conflict resolution, but I'm not clear on what's the best
> > > practice when conflicting with -mm.
>
> What happens depends on timing as things arrive to Linus. I promised
> to send hmm.git early, so I understand that Andrew will quilt rebase
> his tree to Linus's and fix the conflict in Ira's patch before he
> sends it.
>
> > Regardless the patch is buggy. If you want to do the conflict
> > resolution it should be because the DEVICE_PUBLIC removal effectively
> > does the same fix otherwise we're knowingly leaving a broken point in
> > the history.
>
> I'm not sure I understand your concern, is there something wrong with
> CH's series as it stands? hmm is a non-rebasing git tree, so as long
> as the series is correct *when I apply it* there is no broken history.
>
> I assumed the conflict resolution for Ira's patch was to simply take
> the deletion of the if block from CH's series - right?
>
> If we do need to take Ira's patch into hmm.git it will go after CH's
> series (and Ira will have to rebase/repost it), so I think there is
> nothing to do at this moment - unless you are saying there is a
> problem with the series in CH's git tree?

There is a problem with the series in CH's tree. It removes the
->page_free() callback from the release_pages() path because it goes
too far and removes the put_devmap_managed_page() call.