linux-kernel - Re: get_user_pages() on an mmap()ed file allowed? What to do if 0 < get_user_pages(..., nr_pages, ...) < nr

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Message-ID: <c384c5ea0908040259k4295c986wdd45fe9e1e4315b1@mail.gmail.com>
Date:	Tue, 4 Aug 2009 11:59:08 +0200
From:	Leon Woestenberg <leon.woestenberg@...il.com>
To:	Brice Goglin <Brice.Goglin@...ia.fr>
Cc:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: get_user_pages() on an mmap()ed file allowed? What to do if 0 < 
	get_user_pages(..., nr_pages, ...) < nr_pages?

Hello Brice,

On Tue, Aug 4, 2009 at 11:18 AM, Brice Goglin<Brice.Goglin@...ia.fr> wrote:
> Hugh Dickins wrote:
>>> - what should a driver do when get_user_pages() returns less pages
>>> than requested?
>>
>> Probably put_page the pages gotten then report the surprise;
>> perhaps, before putting the pages gotten, try get_user_pages
>> on the next alone, to see what error code is returned for that.
>
> I wonder if we should change get_user_pages to store ERR_PTR(ret)
> in page[i] when it fails to get page #i.
>
Yes, I would see that as an improvement in finding out why rc <
nr_pages, in case rc > 0.

Also I think it does not break existing users.

Regards,

-- 
Leon
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