Re: [PATCH 2/2] mm: set PG_dma_pinned on get_user_pages*()

Jan Kara
2018-06-27T12:43:01Z

On Wed 27-06-18 13:59:27, Michal Hocko wrote:
> On Wed 27-06-18 13:53:49, Jan Kara wrote:
> > On Wed 27-06-18 13:32:21, Michal Hocko wrote:
> [...]
> > > Appart from that, do we really care about 32b here? Big DIO, IB users
> > > seem to be 64b only AFAIU.
> >
> > IMO it is a bad habit to leave unpriviledged-user-triggerable oops in the
> > kernel even for uncommon platforms...
>
> Absolutely agreed! I didn't mean to keep the blow up for 32b. I just
> wanted to say that we can stay with a simple solution for 32b. I thought
> the g-u-p-longterm has plugged the most obvious breakage already. But
> maybe I just misunderstood.

Most yes, but if you try hard enough, you can still trigger the oops e.g.
with appropriately set up direct IO when racing with writeback / reclaim.

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR