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

[Christoph Hellwig]

On Fri, Jun 28, 2019 at 11:59:19AM -0700, Dan Williams wrote:
> It's a bug that the call to put_devmap_managed_page() was gated by
> MEMORY_DEVICE_PUBLIC in release_pages(). That path is also applicable
> to MEMORY_DEVICE_FSDAX because it needs to trigger the ->page_free()
> callback to wake up wait_on_var() via fsdax_pagefree().
> 
> So I guess you could argue that the MEMORY_DEVICE_PUBLIC removal patch
> left the original bug in place. In that sense we're no worse off, but
> since we know about the bug, the fix and the patches have not been
> applied yet, why not fix it now?

The fix it now would simply be to apply Ira original patch now, but
given that we are at -rc6 is this really a good time?  And if we don't
apply it now based on the quilt based -mm worflow it just seems a lot
easier to apply it after my series.  Unless we want to include it in
the series, in which case I can do a quick rebase, we'd just need to
make sure Andrew pulls it from -mm.