Re: [RFC][PATCH] HWPOISON: remove the unsafe __set_page_locked()

Nick Piggin
2009-09-28T02:57:42Z

On Mon, Sep 28, 2009 at 03:19:43AM +0200, Andi Kleen wrote:
> > There is no real rush AFAIKS to fix this one single pagecache site
> > while we have problems with slab allocators and all other unaudited
> > places that nonatomically modify page flags with an elevated
>
> hwpoison ignores slab pages.

"ignores" them *after* it has already written to page flags?
By that time it's too late.

> > page reference ... just mark HWPOISON as broken for the moment, or
> > cut it down to do something much simpler I guess?
>
> Erm no. These cases are *EXTREMLY* unlikely to hit.

Well it's fundamentally badly buggy, rare or not. We could avoid
lots of nasty atomic operations if we just care that it works
most of the time. I guess it's a matter of perspective but I
won't push for one thing or the other in hwpoison code so long
as it stays out of core code for the most part.