linux-ext4 - Re: [PATCH v6 02/13] mm: remove extra ZONE

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Date:   Sun, 15 Aug 2021 13:40:29 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Christoph Hellwig <hch@....de>, Alex Sierra <alex.sierra@....com>
CC:     <akpm@...ux-foundation.org>, <Felix.Kuehling@....com>,
        <linux-mm@...ck.org>, <rcampbell@...dia.com>,
        <linux-ext4@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
        <amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
        <jgg@...dia.com>, <jglisse@...hat.com>
Subject: Re: [PATCH v6 02/13] mm: remove extra ZONE_DEVICE struct page
 refcount

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

thanks,
--
John Hubbard
NVIDIA