linux-kernel - Re: [PATCH 1/3] userfaultfd: selftest: Fix checking of userfaultfd

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Message-Id: <8736w0b7r9.fsf@morokweng.localdomain>
Date:   Mon, 30 Jul 2018 20:53:30 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc:     linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Prakash Sangappa <prakash.sangappa@...cle.com>
Subject: Re: [PATCH 1/3] userfaultfd: selftest: Fix checking of userfaultfd_open() result


Hello Mike,

Thanks for promptly reviewing the patches.

Mike Rapoport <rppt@...ux.vnet.ibm.com> writes:

> Hi,
>
> On Tue, Jul 24, 2018 at 11:42:07PM -0300, Thiago Jung Bauermann wrote:
>> If the userfaultfd test is run on a kernel with CONFIG_USERFAULTFD=n, it
>> will report that the system call is not available yet go ahead and continue
>> anyway:
>>
>>   # ./userfaultfd anon 30 1
>>   nr_pages: 480, nr_pages_per_cpu: 120
>>   userfaultfd syscall not available in this kernel
>>   bounces: 0, mode:, register failure
>>
>> This is because userfaultfd_open() returns 0 on success and 1 on error but
>> all callers assume that it returns < 0 on error.
>>
>> Since the convention of the test as a whole is the one used by
>> userfault_open(), fix its callers instead. Now the test behaves correctly:
>>
>>   # ./userfaultfd anon 30 1
>>   nr_pages: 480, nr_pages_per_cpu: 120
>>   userfaultfd syscall not available in this kernel
>>
>> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
>
> It seems that this patch is superseded by the second patch in this series.

Yes, but since this is a simple bugfix while the other patch is a
proposed improvement which can be debated, I think it's worthwhile to
keep them separate.

--
Thiago Jung Bauermann
IBM Linux Technology Center