netdev - Re: [PATCH v11 04/25] mm: devmap: refactor 1-based refcounting for ZONE

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Message-ID: <d0a99e75-0175-0f31-f176-8c37c18a4108@nvidia.com>
Date:   Wed, 18 Dec 2019 21:48:57 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alex Williamson <alex.williamson@...hat.com>,
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Subject: Re: [PATCH v11 04/25] mm: devmap: refactor 1-based refcounting for
 ZONE_DEVICE pages

On 12/18/19 9:27 PM, Dan Williams wrote:
...
>> @@ -461,5 +449,5 @@ void __put_devmap_managed_page(struct page *page)
>>          page->mapping = NULL;
>>          page->pgmap->ops->page_free(page);
>>   }
>> -EXPORT_SYMBOL(__put_devmap_managed_page);
>> +EXPORT_SYMBOL(free_devmap_managed_page);
> 
> This patch does not have a module consumer for
> free_devmap_managed_page(), so the export should move to the patch
> that needs the new export.

Hi Dan,

OK, I know that's a policy--although it seems quite pointless here given
that this is definitely going to need an EXPORT.

At the moment, the series doesn't use it in any module at all, so I'll just
delete the EXPORT for now.

> 
> Also the only reason that put_devmap_managed_page() is EXPORT_SYMBOL
> instead of EXPORT_SYMBOL_GPL is that there was no practical way to
> hide the devmap details from evey module in the kernel that did
> put_page(). I would expect free_devmap_managed_page() to
> EXPORT_SYMBOL_GPL if it is not inlined into an existing exported
> static inline api.
> 

Sure, I'll change it to EXPORT_SYMBOL_GPL when the time comes. We do have
to be careful that we don't shut out normal put_page() types of callers,
but...glancing through the current callers, that doesn't look to be a problem.
Good. So it should be OK to do EXPORT_SYMBOL_GPL here.

Are you *sure* you don't want to just pre-emptively EXPORT now, and save
looking at it again?

thanks,
-- 
John Hubbard
NVIDIA