On Wed, 29 May 2019 00:11:15 +0800 Michal Hocko wrote:
> On Tue 28-05-19 23:38:11, Hillf Danton wrote:
> >
> > In short, I prefer to skip IO mapping since any kind of address range
> > can be expected from userspace, and it may probably cover an IO mapping.
> > And things can get out of control, if we reclaim some IO pages while
> > underlying device is trying to fill data into any of them, for instance.
>
> What do you mean by IO pages why what is the actual problem?
>
Io pages are the backing-store pages of a mapping whose vm_flags has
VM_IO set, and the comment in mm/memory.c says:
/*
* Physically remapped pages are special. Tell the
* rest of the world about it:
* VM_IO tells people not to look at these pages
* (accesses can have side effects).
BR
Hillf
