Re: [RESEND PATCH v1] mm/vmalloc: fix page mapping if vm_area_alloc_pages() with high order fallback to order 0

Michal Hocko
2024-08-28T07:14:59Z

On Tue 27-08-24 17:29:34, Uladzislau Rezki wrote:
> On Tue, Aug 27, 2024 at 03:37:38PM +0200, Michal Hocko wrote:
> > On Tue 27-08-24 14:47:30, Uladzislau Rezki wrote:
> > > On Tue, Aug 26, 2024 at 08:49:35AM +0200, Michal Hocko wrote:
> > [...]
> > > > > 2. High-order allocations. Do you think we should not care much about
> > > > > it when __GFP_NOFAIL is set? Same here, there is a fallback for order-0
> > > > > if "high" fails, it is more likely NO_FAIL succeed for order-0. Thus
> > > > > keeping NOFAIL for high-order sounds like not a good approach to me.
> > > >
> > > > We should avoid high order allocations with GFP_NOFAIL at all cost.
> > > >
> > > What do you propose here? Fail such request?
> >
> > We shouldn't have any hard requirements for higher order allocations in the vmalloc
> > right? In other words we can always fallback to base pages.
> >
> We always drop NOFAIL for high-order, if it fails we fall-back to
> order-0. I got the feeling that you wanted just bail-out fully if
> high-order and NOFAIL.

Nope. We should always fall back to order 0 for both NOFAIL and regular
vmalloc allocations.

--
Michal Hocko
SUSE Labs