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Subject: Re: [PATCH v6 02/13] mm: remove extra ZONE_DEVICE struct page
 refcount
To:     John Hubbard <jhubbard@nvidia.com>, Christoph Hellwig <hch@lst.de>,
        Alex Sierra <alex.sierra@amd.com>
Cc:     akpm@linux-foundation.org, linux-mm@kvack.org,
        rcampbell@nvidia.com, linux-ext4@vger.kernel.org,
        linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org,
        dri-devel@lists.freedesktop.org, jgg@nvidia.com, jglisse@redhat.com
References: <20210813063150.2938-1-alex.sierra@amd.com>
 <20210813063150.2938-3-alex.sierra@amd.com> <20210815153713.GA32384@lst.de>
 <387d5f85-3d15-9a9e-2382-6ce3c14bc6d5@nvidia.com>
From:   Felix Kuehling <felix.kuehling@amd.com>
Message-ID: <94dbd8f2-6c7e-cddc-6792-00f12942937c@amd.com>
Date:   Mon, 16 Aug 2021 14:56:40 -0400
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Am 2021-08-15 um 4:40 p.m. schrieb John Hubbard:
> On 8/15/21 8:37 AM, Christoph Hellwig wrote:
>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>> index 8ae31622deef..d48a1f0889d1 100644
>>> --- a/include/linux/mm.h
>>> +++ b/include/linux/mm.h
>>> @@ -1218,7 +1218,7 @@ __maybe_unused struct page
>>> *try_grab_compound_head(struct page *page, int refs,
>>>   static inline __must_check bool try_get_page(struct page *page)
>>>   {
>>>       page = compound_head(page);
>>> -    if (WARN_ON_ONCE(page_ref_count(page) <= 0))
>>> +    if (WARN_ON_ONCE(page_ref_count(page) <
>>> (int)!is_zone_device_page(page)))
>>
>> Please avoid the overly long line.  In fact I'd be tempted to just not
>> bother here and keep the old, more lose check.  Especially given that
>> John has a patch ready that removes try_get_page entirely.
>>
>
> Yes. Andrew has accepted it into mmotm.
>
> Ralph's patch here was written well before my cleanup that removed
> try_grab_page() [1]. But now that we're here, if you drop this hunk then
> it will make merging easier, I think.
>
>
> [1]
> https://lore.kernel.org/r/20210813044133.1536842-4-jhubbard@nvidia.com

Hi John,

Thanks for the pointer. We'll drop this hunk and add a statement to our
patch description to highlight the dependency on your patch.

Regards,
  Felix


>
> thanks,
> -- 
> John Hubbard
> NVIDIA
>