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

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Message-ID: <a8637239-c292-c6c4-e72b-f7a258d5d8a5@huawei.com>
Date:   Mon, 22 Mar 2021 14:45:33 +0800
From:   "wangyanan (Y)" <wangyanan55@...wei.com>
To:     Andrew Jones <drjones@...hat.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 2021/3/12 19:40, Andrew Jones wrote:
> 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
I will fix it and add your R-b in this patch.

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