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From:   Joonsoo Kim <js1304@gmail.com>
Date:   Fri, 22 May 2020 16:42:54 +0900
Message-ID: <CAAmzW4Pf72YyA-w3BA-Kamf2h82rtinatUvTZwdcMvhCmc1tgQ@mail.gmail.com>
Subject: Re: [PATCH 06/11] mm/hugetlb: do not modify user provided gfp_mask
To:     Mike Kravetz <mike.kravetz@oracle.com>
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,
        Vlastimil Babka <vbabka@suse.cz>,
        Christoph Hellwig <hch@infradead.org>,
        Roman Gushchin <guro@fb.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Michal Hocko <mhocko@suse.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
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2020=EB=85=84 5=EC=9B=94 22=EC=9D=BC (=EA=B8=88) =EC=98=A4=EC=A0=84 7:19, M=
ike Kravetz <mike.kravetz@oracle.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> On 5/17/20 6:20 PM, js1304@gmail.com wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >
> > It's not good practice to modify user input. Instead of using it to
> > build correct gfp_mask for APIs, this patch introduces another gfp_mask
> > field, __gfp_mask, for internal usage.
>
> Modifying the flags as is done in the existing code does not bother me
> too much, but that is just my opinion.  Adding __gfp_mask for modificatio=
ns
> is fine with me if others think it is a good thing.

With the following patches, in some cases, ac->gfp_mask is set up once and
used many times. If we modify ac->gfp_mask in place, there would be side-ef=
fect.

> Does dequeue_huge_page_vma() need to be modified so that it will set
> ac.__gfp_mask before calling dequeue_huge_page_nodemask()?

Good catch! Will change!

Thanks.