Re: Properly stop kernel threads on aic7xxx

Andrew Morton
2004-04-02T01:01:58Z

Andrea Arcangeli <andrea@suse.de> wrote:
>
> I'm also unsure why _all_ multipage allocations really need this
> compound thing setup and why can't the owner of the page take care of
> the refcounting itself by always using the head page. I may actually
> add a GFP bitflag asking for a multipage but w/o a compound setup. There
> are million ways to fix this, none of which is obvious.

For direct-io into higher-order pages. When doing direct-io into a hugetlb
page we need to make sure that get_user_pages() pins the correct pageframe.

Possibly we need to turn it on regardless of CONFIG_HUGETLBPAGE for people
who want to do direct-io or PEEKTEXT/POKETEXT into mmapped soundcard
buffers, for example. Perhaps there's a race which could permit direct-io
to write to a freed page via this route..

Davem had some reason why he might want to turn on the compound logic
permanently - related to TCP access to/from higher-order pages, I think.