linux-kernel - Re: [PATCH 16/25] device-dax: use the dev

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Message-ID: <20190628190207.GA9317@lst.de>
Date:   Fri, 28 Jun 2019 21:02:07 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...lanox.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 16/25] device-dax: use the dev_pagemap internal refcount

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.