Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation

Greg KH
2005-04-24T21:27:31Z

On Sun, Apr 24, 2005 at 09:23:48AM -0500, Timur Tabi wrote:
> Andrew Morton wrote:
>
> >If your theory is correct then it should be able to demonstrate this
> >problem without any special hardware at all: pin some user memory, then
> >generate memory pressure then check the contents of those pinned pages.
>
> I tried that, but I couldn't get it to fail. But that was a while ago, and
> I've learned a few things since then, so I'll try again.
>
> >But if, for the DMA transfer, you're using the array of page*'s which were
> >originally obtained from get_user_pages() then it's rather hard to see how
> >the kernel could alter the page's contents.
> >
> >Then again, if mlock() fixes it then something's up. Very odd.
>
> With mlock(), we don't need to use get_user_pages() at all. Arjan tells me
> the only time an mlocked page can move is with hot (un)plug of memory, but
> that isn't supported on the systems that we support.

You don't "support" i386 or ia64 or x86-64 or ppc64 systems? What
hardware do you support? And what about the fact that you are aiming to
get this code into mainline, right? If not, why are you asking here?
:)

thanks,

greg k-h