Re: [PATCH 1/4] mm/page_alloc: fix non cma alloc context

[Joonsoo Kim <js1304@gmail.com>]

2020년 7월 16일 (목) 오후 4:45, Vlastimil Babka <vbabka@suse.cz>님이 작성:
>
> On 7/16/20 9:27 AM, Joonsoo Kim wrote:
> > 2020년 7월 15일 (수) 오후 5:24, Vlastimil Babka <vbabka@suse.cz>님이 작성:
> >> >  /*
> >> >   * get_page_from_freelist goes through the zonelist trying to allocate
> >> >   * a page.
> >> > @@ -3706,6 +3714,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
> >> >       struct pglist_data *last_pgdat_dirty_limit = NULL;
> >> >       bool no_fallback;
> >> >
> >> > +     current_alloc_flags(gfp_mask, &alloc_flags);
> >>
> >> I don't see why to move the test here? It will still be executed in the
> >> fastpath, if that's what you wanted to avoid.
> >
> > I want to execute it on the fastpath, too. Reason that I moved it here
> > is that alloc_flags could be reset on slowpath. See the code where
> > __gfp_pfmemalloc_flags() is on. This is the only place that I can apply
> > this option to all the allocation paths at once.
>
> But get_page_from_freelist() might be called multiple times in the slowpath, and
> also anyone looking for gfp and alloc flags setup will likely not examine this
> function. I don't see a problem in having it in two places that already deal
> with alloc_flags setup, as it is now.

I agree that anyone looking alloc flags will miss that function easily. Okay.
I will place it on its original place, although we now need to add one
more place.
*Three places* are gfp_to_alloc_flags(), prepare_alloc_pages() and
__gfp_pfmemalloc_flags().

Thanks.