Re: [PATCH] mm: drop VM_BUG_ON from __get_free_pages

[Michal Hocko]

On Wed 27-06-18 09:50:01, Vlastimil Babka wrote:
> On 06/27/2018 09:34 AM, Michal Hocko wrote:
> > On Tue 26-06-18 10:04:16, Andrew Morton wrote:
> > 
> > And as I've argued before the code would be wrong regardless. We would
> > leak the memory or worse touch somebody's else kmap without knowing
> > that.  So we have a choice between a mem leak, data corruption k or a
> > silent fixup. I would prefer the last option. And blowing up on a BUG
> > is not much better on something that is easily fixable. I am not really
> > convinced that & ~__GFP_HIGHMEM is something to lose sleep over.
> 
> Maybe put the fixup into a "#ifdef CONFIG_HIGHMEM" block and then modern
> systems won't care? In that case it could even be if (WARN_ON_ONCE(...))
> so future cases with wrong expectations would become known.

Yes that could be done as well. Or maybe we can make __GFP_HIGHMEM 0 for
!HIGHMEM systems. Does something really rely on it being non-zero?

-- 
Michal Hocko
SUSE Labs