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From:   Joonsoo Kim <js1304@gmail.com>
Date:   Fri, 17 Jul 2020 16:29:17 +0900
Message-ID: <CAAmzW4MLc8bmkYW1q1fL_WRFQHksX-oy9tS-s9Kb-A=ZEeGETQ@mail.gmail.com>
Subject: Re: [PATCH 1/4] mm/page_alloc: fix non cma alloc context
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, kernel-team@lge.com,
        Christoph Hellwig <hch@infradead.org>,
        Roman Gushchin <guro@fb.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Michal Hocko <mhocko@suse.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, stable@vger.kernel.org
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2020=EB=85=84 7=EC=9B=94 16=EC=9D=BC (=EB=AA=A9) =EC=98=A4=ED=9B=84 4:45, V=
lastimil Babka <vbabka@suse.cz>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> On 7/16/20 9:27 AM, Joonsoo Kim wrote:
> > 2020=EB=85=84 7=EC=9B=94 15=EC=9D=BC (=EC=88=98) =EC=98=A4=ED=9B=84 5:2=
4, Vlastimil Babka <vbabka@suse.cz>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
> >> >  /*
> >> >   * get_page_from_freelist goes through the zonelist trying to alloc=
ate
> >> >   * a page.
> >> > @@ -3706,6 +3714,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigne=
d int order, int alloc_flags,
> >> >       struct pglist_data *last_pgdat_dirty_limit =3D 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 th=
e
> >> 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 slowpa=
th, 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 d=
eal
> with alloc_flags setup, as it is now.

I agree that anyone looking alloc flags will miss that function easily. Oka=
y.
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.