Re: [PATCH v2 2/3] selftests/mm: emit TAP header and use TAP skip in mremap_test

Hi, Usama

在 2026/8/17 23:44, Usama Anjum 写道:
> On 15/08/2026 9:07 am, Song Hu wrote:
>> mremap_test calls ksft_set_plan() without ksft_print_header(), and its
>> get_mmap_min_addr() skip path uses a bare exit(KSFT_SKIP) that prints no
>> TAP line, so its output is not valid KTAP.  Add the header and switch
>> the skip to ksft_exit_skip().
>>
>> Also fix two more KTAP compliance issues spotted in review:
>>
>> - get_mmap_min_addr() calls strerror(errno) after fclose(), which may
>>   clobber errno; save errno before fclose() instead.
>>
>> - Some ksft_*() messages embed "\n\t", so the text after each embedded
>>   newline is printed without the "# " prefix.  Split those into separate
>>   messages.
>>
>> Acked-by: Mike Rapoport (Microsoft) <[email protected]>
>> Reviewed-by: Sarthak Sharma <[email protected]>
>> Signed-off-by: Song Hu <[email protected]>
>> ---
>>  tools/testing/selftests/mm/mremap_test.c | 41 +++++++++++++-----------
>>  1 file changed, 23 insertions(+), 18 deletions(-)
>>
>> diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
>> index 131d9d6db867..28f151daabe4 100644
>> --- a/tools/testing/selftests/mm/mremap_test.c
>> +++ b/tools/testing/selftests/mm/mremap_test.c
>> @@ -111,18 +111,17 @@ static unsigned long long get_mmap_min_addr(void)
>>  		return addr;
>>  
>>  	fp = fopen("/proc/sys/vm/mmap_min_addr", "r");
>> -	if (fp == NULL) {
>> -		ksft_print_msg("Failed to open /proc/sys/vm/mmap_min_addr: %s\n",
>> -			strerror(errno));
>> -		exit(KSFT_SKIP);
>> -	}
>> +	if (!fp)
>> +		ksft_exit_skip("Failed to open /proc/sys/vm/mmap_min_addr: %s\n",
>> +			       strerror(errno));
> 
> The skip conditions are usually at the start of the test before we set
> the total number planned tests. If skip like this happens later, it
> still counts as failure. I found the following corresponding output
> with this patch:
> 
> TAP version 13
> # Test configs:
> # threshold_mb=4
> # pattern_seed=1786980558
> 1..26
> ok 1 # SKIP Failed to read /proc/sys/vm/mmap_min_addr: Success
> # 1 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
> # Planned tests != run tests (26 != 1)
> # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
> MREMAP_FORCED_SKIP_RC=4
> ### MREMAP FORCED READ-SKIP END
> 

Right, get_mmap_min_addr() is first reached from deep inside
run_mremap_test_case(), long after the plan is set.  v3 caches
mmap_min_addr in main(), right after ksft_print_header() and before
ksft_set_plan(), so the skip paths now run before the plan.  Reproducing
your scenario by injecting a read failure on the sysctl (LD_PRELOAD
fopen shim handing the test /dev/null for it):

	TAP version 13
	1..0 # SKIP Failed to read /proc/sys/vm/mmap_min_addr: Success

Thanks,
Song

>>  
>>  	n_matched = fscanf(fp, "%llu", &addr);
>>  	if (n_matched != 1) {
>> -		ksft_print_msg("Failed to read /proc/sys/vm/mmap_min_addr: %s\n",
>> -			strerror(errno));
>> +		int err = errno;
>> +
>>  		fclose(fp);
>> -		exit(KSFT_SKIP);
>> +		ksft_exit_skip("Failed to read /proc/sys/vm/mmap_min_addr: %s\n",
>> +			       strerror(err));
>>  	}
>>  
>>  	fclose(fp);
>> @@ -1164,10 +1163,11 @@ static void run_mremap_test_case(struct test test_case, int *failures,
>>  					    rand_addr);
>>  
>>  	if (remap_time < 0) {
>> -		if (test_case.expect_failure)
>> -			ksft_test_result_xfail("%s\n\tExpected mremap failure\n",
>> -					      test_case.name);
>> -		else {
>> +		if (test_case.expect_failure) {
>> +			ksft_print_msg("%s: expected mremap failure\n",
>> +				       test_case.name);
>> +			ksft_test_result_xfail("%s\n", test_case.name);
>> +		} else {
>>  			ksft_test_result_fail("%s\n", test_case.name);
>>  			*failures += 1;
>>  		}
>> @@ -1177,11 +1177,13 @@ static void run_mremap_test_case(struct test test_case, int *failures,
>>  		 * was faulted in.
>>  		 */
>>  		if (threshold_mb == VALIDATION_NO_THRESHOLD ||
>> -		    test_case.config.region_size <= threshold_mb * _1MB)
>> -			ksft_test_result_pass("%s\n\tmremap time: %12lldns\n",
>> -					      test_case.name, remap_time);
>> -		else
>> +		    test_case.config.region_size <= threshold_mb * _1MB) {
>> +			ksft_print_msg("%s: mremap time: %12lldns\n",
>> +				       test_case.name, remap_time);
>>  			ksft_test_result_pass("%s\n", test_case.name);
>> +		} else {
>> +			ksft_test_result_pass("%s\n", test_case.name);
>> +		}
>>  	}
>>  }
>>  
>> @@ -1250,13 +1252,16 @@ int main(int argc, char **argv)
>>  	time_t t;
>>  	FILE *maps_fp;
>>  
>> +	ksft_print_header();
>> +
>>  	pattern_seed = (unsigned int) time(&t);
>>  
>>  	if (parse_args(argc, argv, &threshold_mb, &pattern_seed) < 0)
>>  		exit(EXIT_FAILURE);
>>  
>> -	ksft_print_msg("Test configs:\n\tthreshold_mb=%u\n\tpattern_seed=%u\n\n",
>> -		       threshold_mb, pattern_seed);
>> +	ksft_print_msg("Test configs:\n");
>> +	ksft_print_msg("threshold_mb=%u\n", threshold_mb);
>> +	ksft_print_msg("pattern_seed=%u\n", pattern_seed);
>>  
>>  	/*
>>  	 * set preallocated random array according to test configs; see the
> 
> Thanks,
> Usama