linux-kernel - Re: [RFC PATCH v4 6/9] KVM: selftests: Add a helper to get system default hugetlb page size

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Date:   Fri, 12 Mar 2021 12:40:29 +0100
From:   Andrew Jones <drjones@...hat.com>
To:     Yanan Wang <wangyanan55@...wei.com>
Cc:     kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Ben Gardon <bgardon@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Peter Xu <peterx@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        wanghaibin.wang@...wei.com, yezengruan@...wei.com,
        yuzenghui@...wei.com
Subject: Re: [RFC PATCH v4 6/9] KVM: selftests: Add a helper to get system
 default hugetlb page size

On Tue, Mar 02, 2021 at 08:57:48PM +0800, Yanan Wang wrote:
> If HUGETLB is configured in the host kernel, then we can know the system
> default hugetlb page size through *cat /proc/meminfo*. Otherwise, we will
> not see the information of hugetlb pages in file /proc/meminfo if it's not
> configured. So add a helper to determine whether HUGETLB is configured and
> then get the default page size by reading /proc/meminfo.
> 
> This helper can be useful when a program wants to use the default hugetlb
> pages of the system and doesn't know the default page size.
> 
> Signed-off-by: Yanan Wang <wangyanan55@...wei.com>
> ---
>  .../testing/selftests/kvm/include/test_util.h |  1 +
>  tools/testing/selftests/kvm/lib/test_util.c   | 27 +++++++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
> index ef24c76ba89a..e087174eefe5 100644
> --- a/tools/testing/selftests/kvm/include/test_util.h
> +++ b/tools/testing/selftests/kvm/include/test_util.h
> @@ -80,6 +80,7 @@ struct vm_mem_backing_src_alias {
>  
>  bool thp_configured(void);
>  size_t get_trans_hugepagesz(void);
> +size_t get_def_hugetlb_pagesz(void);
>  void backing_src_help(void);
>  enum vm_mem_backing_src_type parse_backing_src_type(const char *type_name);
>  
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index f2d133f76c67..80d68dbd72d2 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -153,6 +153,33 @@ size_t get_trans_hugepagesz(void)
>  	return size;
>  }
>  
> +size_t get_def_hugetlb_pagesz(void)
> +{
> +	char buf[64];
> +	const char *tag = "Hugepagesize:";
> +	FILE *f;
> +
> +	f = fopen("/proc/meminfo", "r");
> +	TEST_ASSERT(f != NULL, "Error in opening /proc/meminfo: %d", errno);
> +
> +	while (fgets(buf, sizeof(buf), f) != NULL) {
> +		if (strstr(buf, tag) == buf) {
> +			fclose(f);
> +			return strtoull(buf + strlen(tag), NULL, 10) << 10;
> +		}
> +	}
> +
> +	if (feof(f)) {
> +		fclose(f);
> +		TEST_FAIL("HUGETLB is not configured in host kernel");
> +	} else {
> +		fclose(f);
> +		TEST_FAIL("Error in reading /proc/meminfo: %d", errno);
> +	}

fclose() can be factored out.

> +
> +	return 0;
> +}
> +
>  void backing_src_help(void)
>  {
>  	int i;
> -- 
> 2.23.0
>

Besides the fclose comment and the same errno comment as the previous
patch

Reviewed-by: Andrew Jones <drjones@...hat.com>