On Sun 19-06-16 23:35:43, Michal Hocko wrote:
> On Sat 18-06-16 03:09:02, Michael S. Tsirkin wrote:
> > On Fri, Jun 17, 2016 at 11:00:17AM +0200, Michal Hocko wrote:
[...]
> > > /*
> > > + * A safe variant of __get_user for for use_mm() users to have a
> > > + * gurantee that the address space wasn't reaped in the background
> > > + */
> > > +#define __get_user_mm(mm, x, ptr) \
> > > +({ \
> > > + int ___gu_err = __get_user(x, ptr); \
> > > + if (!___gu_err && test_bit(MMF_UNSTABLE, &mm->flags)) \
> >
> > test_bit is somewhat expensive. See my old mail
> > x86/bitops: implement __test_bit
>
> Do you have a msg_id?
Found it
http://lkml.kernel.org/r/1440776707-22016-1-git-send-email-mst@xxxxxxxxxx
--
Michal Hocko
SUSE Labs
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