linux-kernel - Re: [PATCH V2 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non

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Message-ID: <5194748A.5070700@cn.fujitsu.com>
Date:	Thu, 16 May 2013 13:54:18 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Mel Gorman <mgorman@...e.de>
CC:	Minchan Kim <minchan@...nel.org>,
	Lin Feng <linfeng@...fujitsu.com>, akpm@...ux-foundation.org,
	bcrl@...ck.org, viro@...iv.linux.org.uk, khlebnikov@...nvz.org,
	walken@...gle.com, kamezawa.hiroyu@...fujitsu.com, riel@...hat.com,
	rientjes@...gle.com, isimatu.yasuaki@...fujitsu.com,
	wency@...fujitsu.com, laijs@...fujitsu.com, jiang.liu@...wei.com,
	zab@...hat.com, jmoyer@...hat.com, linux-mm@...ck.org,
	linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH V2 1/2] mm: hotplug: implement non-movable version of
 get_user_pages() called get_user_pages_non_movable()

Hi Mel,

On 05/15/2013 09:24 PM, Mel Gorman wrote:
> If it is to be an address space operations sturcture then you'll need a
> pseudo mapping structure for anonymous pages that are pinned by aio --
> similar in principal to how swapper_space is used for managing PageSwapCache
> or how anon_vma structures can be associated with a page.
>
> However, I warn you that you may find that the address_space is the
> wrong level to register such callbacks, it just seemed like the obvious
> first choice. A potential alternative implementation is to create a 1:1
> association between pages and a long-lived holder that is stored on a hash
> table (similar style of arrangement as page_waitqueue).  A page is looked up
> in the hash table and if an entry exists, it points to an callback structure
> to the subsystem holding the pin. It's up to the subsystem to register the
> callbacks when it is about to pin a page (get_user_pages_longlived(....,
> &release_ops) and figure out how to release the pin safely.
>

OK, I'll try to figure out a proper place to put the callbacks.
But I think we need to add something new to struct page. I'm just
not sure if it is OK. Maybe we can discuss more about it when I send
a RFC patch.

Thanks for the advices, and I'll try them.

Thanks. :)
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