linux-kernel - Re: [PATCH 1/1] mm/gup_benchmark: fix MAP

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Message-ID: <8892a2be-029b-f8c5-d984-8ff3b5c490ed@nvidia.com>
Date:   Tue, 22 Oct 2019 12:39:53 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Jerome Glisse <jglisse@...hat.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Keith Busch <keith.busch@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 1/1] mm/gup_benchmark: fix MAP_HUGETLB case

On 10/22/19 11:57 AM, Jerome Glisse wrote:
> On Tue, Oct 22, 2019 at 11:41:57AM -0700, John Hubbard wrote:
>> On 10/22/19 10:14 AM, Jerome Glisse wrote:
>>> On Mon, Oct 21, 2019 at 02:24:35PM -0700, John Hubbard wrote:
>>>> The MAP_HUGETLB ("-H" option) of gup_benchmark fails:
>> ...
> So i was misslead by the file descriptor, passing a file descriptor and
> asking for anonymous always bugs me. But yeah the _linux_ kernel is happy
> to ignore the file argument if you set the anonymous flag. I guess the
> rules of passing -1 for fd when anonymous is just engrave in my brain.
> 

Yeah, I definitely get that. In fact, I initially considered further changing 
the test code so as to pass -1 for fd in this case, but because it's pure 
Linux-only test code, it didn't really seem worth the (small) additional
change.

> Also i thought that the file was an argument of the test and thus that
> for huge you needed to pass a hugetlbfs' file.
> 
> Anyway my mistake, you are right, you can pass a file and ask for anonymous
> and hugetlb at the same time.
> 
> Reviewed-by: Jérôme Glisse <jglisse@...hat.com>
> 

Thanks for the review! 

Admin note: this already went into mmotm, so I'm hoping Andrew will notice this
email and add the Reviewed-by tag, please?

thanks,

John Hubbard
NVIDIA