linux-kernel - Re: [patch 2/2] mm, selftests: test return value of munmap for MAP

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Date:	Fri, 27 Mar 2015 10:52:16 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Davide Libenzi <davidel@...ilserver.org>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Shuah Khan <shuahkh@....samsung.com>,
	Hugh Dickins <hughd@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Joern Engel <joern@...fs.org>,
	Jianguo Wu <wujianguo@...wei.com>,
	Eric B Munson <emunson@...mai.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [patch 2/2] mm, selftests: test return value of munmap for
 MAP_HUGETLB memory

On Thu, 2015-03-26 at 16:23 -0700, David Rientjes wrote:
> When MAP_HUGETLB memory is unmapped, the length must be hugepage aligned,
> otherwise it fails with -EINVAL.
> 
> All tests currently behave correctly, but it's better to explcitly test
> the return value for completeness and document the requirement,
> especially if users copy map_hugetlb.c as a sample implementation.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>  tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c | 8 ++++++--
> 
> diff --git a/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c b/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c
> --- a/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c
> +++ b/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c
> @@ -21,9 +21,13 @@ static int test_body(void)
>  		 * Typically the mmap will fail because no huge pages are
>  		 * allocated on the system. But if there are huge pages
>  		 * allocated the mmap will succeed. That's fine too, we just
> -		 * munmap here before continuing.
> +		 * munmap here before continuing.  munmap() length of
> +		 * MAP_HUGETLB memory must be hugepage aligned.
>  		 */
> -		munmap(addr, SIZE);
> +		if (munmap(addr, SIZE)) {
> +			perror("munmap");
> +			return 1;
> +		}
>  	}
>  
>  	p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,

Acked-by: Michael Ellerman <mpe@...erman.id.au>

cheers


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