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Subject: Re: [PATCH 1/2] tomoyo: Convert get_user_pages*() to
 pin_user_pages*()
From:   John Hubbard <jhubbard@nvidia.com>
To:     Souptick Joarder <jrdr.linux@gmail.com>, <takedakn@nttdata.co.jp>,
        <penguin-kernel@I-love.SAKURA.ne.jp>, <jmorris@namei.org>,
        <serge@hallyn.com>
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        <linux-kernel@vger.kernel.org>, Jan Kara <jack@suse.cz>,
        Matthew Wilcox <willy@infradead.org>
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 <e5401549-8c31-2c6d-58dd-864232de17af@nvidia.com>
Message-ID: <e6859981-bc3c-9513-99e5-a99849786156@nvidia.com>
Date:   Sat, 7 Nov 2020 11:17:52 -0800
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On 11/7/20 1:04 AM, John Hubbard wrote:
> On 11/7/20 12:24 AM, Souptick Joarder wrote:
>> In 2019, we introduced pin_user_pages*() and now we are converting
>> get_user_pages*() to the new API as appropriate. [1] & [2] could
>> be referred for more information. This is case 5 as per document [1].
> 
> It turns out that Case 5 can be implemented via a better pattern, as long
> as we're just dealing with a page at a time, briefly:
> 
> lock_page()
> write to page's data
> unlock_page()
> 
> ...which neatly synchronizes with writeback and other fs activities.

Ahem, I left out a key step: set_page_dirty()!

lock_page()
write to page's data
set_page_dirty()
unlock_page()


thanks,
-- 
John Hubbard
NVIDIA