Re: Remap_file_pages, RSS limits, security implications (was: Re: [uml-devel] Re: [RFC] [patch 0/18] remap_file_pages protection support (for UML), try 3)

[Blaisorblade]

On Wednesday 21 September 2005 18:50, Hugh Dickins wrote:
> On Wed, 21 Sep 2005, Blaisorblade wrote:
> > Other pages in the VMA may be unmapped, yes, but not freed. In fact,
> > they're kept in by the pagecache reference; try_to_unmap() (or better its
> > caller, shrink_list) will only actually free the page it asked for.

> Not freed in that pass, yes; but brought closer to being freed soon.

Will a page with mapcount == 0 be put in the inactive list explicitly? At next 
scan PageActive will be clear, sure, and it won't be reactivated while it's 
unmapped.

But references will only cause more hardware faults.
> > The only real "problem" is that we do ptep_clear_flush_young without
> > activating the page. And yes, *this* may penalize who holds a nonlinear
> > VMA. But this is probably fair, given that we're going to have trouble in
> > freeing those pages.

> Good point, I don't remember ever considering that.
> But agree it should work out fairly.

> > > mm/trash.c?  I got quite excited,

> > What would that have meant?

> Trash is rubbish or garbage.  Or if I trash my hotel room (not me!),
> I'd rip the washbasin off the wall, smash the mirror, throw the
> chair through the window, ... hmm, better stop this public fantasy.

Nice... hope this can get to LWN "quotes of the week" page.

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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