linux-kernel - Re: [PATCH v2 4/8] selftests/mm: Fix thuge-gen test bugs

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Message-ID: <e9207c67-40d9-23c9-3c90-677e0a605566@redhat.com>
Date:   Mon, 17 Jul 2023 19:22:12 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Ryan Roberts <ryan.roberts@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        Mark Brown <broonie@...nel.org>,
        John Hubbard <jhubbard@...dia.com>,
        Florent Revest <revest@...omium.org>,
        Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 4/8] selftests/mm: Fix thuge-gen test bugs

On 17.07.23 12:31, Ryan Roberts wrote:
> thuge-gen was previously only munmapping part of the mmapped buffer,
> which caused us to run out of 1G huge pages for a later part of the
> test. Fix this by munmapping the whole buffer. Based on the code, it
> looks like a typo rather than an intention to keep some of the buffer
> mapped.
> 
> thuge-gen was also calling mmap with SHM_HUGETLB flag (bit 11 set),
> which is actually MAP_DENYWRITE in mmap context. The man page says this
> flag is ignored in modern kernels. I'm pretty sure from the context that
> the author intended to pass the MAP_HUGETLB flag so I've fixed that up
> too.

Makes sense to me.

> 
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>   tools/testing/selftests/mm/thuge-gen.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/thuge-gen.c b/tools/testing/selftests/mm/thuge-gen.c
> index 380ab5f0a534..16ed4dfa7359 100644
> --- a/tools/testing/selftests/mm/thuge-gen.c
> +++ b/tools/testing/selftests/mm/thuge-gen.c
> @@ -139,7 +139,7 @@ void test_mmap(unsigned long size, unsigned flags)
>   		before, after, before - after, size);
>   	assert(size == getpagesize() || (before - after) == NUM_PAGES);
>   	show(size);
> -	err = munmap(map, size);
> +	err = munmap(map, size * NUM_PAGES);
>   	assert(!err);
>   }
>   
> @@ -222,7 +222,7 @@ int main(void)
>   		test_mmap(ps, MAP_HUGETLB | arg);
>   	}
>   	printf("Testing default huge mmap\n");
> -	test_mmap(default_hps, SHM_HUGETLB);
> +	test_mmap(default_hps, MAP_HUGETLB);
>   
>   	puts("Testing non-huge shmget");
>   	test_shmget(getpagesize(), 0);

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb