linux-kernel - Re: [PATCH] userfaultfd/selftests: use swap() to make code cleaner

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Date:   Mon, 31 Jan 2022 17:06:50 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     cgel.zte@...il.com, akpm@...ux-foundation.org
Cc:     shuah@...nel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Changcheng Deng <deng.changcheng@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH] userfaultfd/selftests: use swap() to make code cleaner

On 1/31/22 15:00, Mike Kravetz wrote:
> On 10/28/21 04:23, cgel.zte@...il.com wrote:
>> From: Changcheng Deng <deng.changcheng@....com.cn>
>>
>> Use swap() in order to make code cleaner. Issue found by coccinelle.
>>
>> Reported-by: Zeal Robot <zealci@....com.cn>
>> Signed-off-by: Changcheng Deng <deng.changcheng@....com.cn>
>> ---
>>  tools/testing/selftests/vm/userfaultfd.c | 10 ++--------
>>  1 file changed, 2 insertions(+), 8 deletions(-)
>>
>> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
>> index 8a09057d2f22..41dfe6f4ebfb 100644
>> --- a/tools/testing/selftests/vm/userfaultfd.c
>> +++ b/tools/testing/selftests/vm/userfaultfd.c
>> @@ -1413,7 +1413,6 @@ static void userfaultfd_pagemap_test(unsigned int test_pgsize)
>>  static int userfaultfd_stress(void)
>>  {
>>  	void *area;
>> -	char *tmp_area;
>>  	unsigned long nr;
>>  	struct uffdio_register uffdio_register;
>>  	struct uffd_stats uffd_stats[nr_cpus];
>> @@ -1524,13 +1523,8 @@ static int userfaultfd_stress(void)
>>  					    count_verify[nr], nr);
>>  
>>  		/* prepare next bounce */
>> -		tmp_area = area_src;
>> -		area_src = area_dst;
>> -		area_dst = tmp_area;
>> -
>> -		tmp_area = area_src_alias;
>> -		area_src_alias = area_dst_alias;
>> -		area_dst_alias = tmp_area;
>> +		swap(area_src, area_dst);
>> +		swap(area_src_alias, area_dst_alias);
>>  
>>  		uffd_stats_report(uffd_stats, nr_cpus);
>>  	}
> 
> Sorry for the late comment/question.
> 
> Where is the test supposed to get the definition of swap()?  When trying to
> build, I get:
> 
> gcc -Wall -I ../../../../usr/include  -no-pie    userfaultfd.c -lrt -lpthread -o /home/mkravetz/tmp/linux-stable/tools/testing/selftests/vm/userfaultfd
> userfaultfd.c: In function ‘userfaultfd_stress’:
> userfaultfd.c:1530:3: warning: implicit declaration of function ‘swap’; did you mean ‘swab’? [-Wimplicit-function-declaration]
>  1530 |   swap(area_src, area_dst);
>       |   ^~~~
>       |   swab
> /usr/bin/ld: /tmp/ccPiwPM0.o: in function `userfaultfd_stress':
> userfaultfd.c:(.text+0x4b6d): undefined reference to `swap'
> /usr/bin/ld: userfaultfd.c:(.text+0x4b8b): undefined reference to `swap'
> collect2: error: ld returned 1 exit status
> make[1]: *** [../lib.mk:146: /home/mkravetz/tmp/linux-stable/tools/testing/selftests/vm/userfaultfd] Error 1
> 
> As far as I can see, swap is only defined in 'include/linux/minmax.h'.
> However, that is not part of the user API and not available to the tests.
> What am I missing?

Please disregard.

It was failing for me on v5.17-rc2, but I see it was fixed in linux-next
with commit "selftests: vm: remove dependecy from internal kernel macros".

Sorry for the noise,
-- 
Mike Kravetz