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

[Tang Chen <tangchen@cn.fujitsu.com>]

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. :)