Re: [PATCH 3/3] fstests: btrfs: testcase for sysfs policy syntax verification

[Anand Jain <anand.jain@oracle.com>]

>> +set_sysfs_policy_must_fail()
>> +{
>> +	local attr=$1
>> +	shift
>> +	local policy=$@
>> +
>> +	_set_fs_sysfs_attr $SCRATCH_DEV $attr ${policy} | _filter_sysfs_error \
>> +			| _expect_error_invalid_argument | tee -a $seqres.full
> 
> This "catch an exact error or output a different error then use
> golden image match failure on secondary error to mark the test as
> failed" semantic is .... overly complex.
> 
> The output on failure of _filter_sysfs_error will be "Invalid
> input". If there's some other failure or it succeeds, the output
> will indicate the failure that occurred (i.e. missing line means no
> error, different error will output directly by the filter). The
> golden image matching will still fail the test.
> 
> IOWs, _expect_error_invalid_argument and the output to seqres.full
> can go away if the test.out file has a matching error for each
> call to set_sysfs_policy_must_fail(). i.e it looks like:
> 
> QA output created by 329
> Invalid input
> Invalid input
> Invalid input
> Invalid input
> Invalid input
> Invalid input
> .....
> Invalid input

Thanks for the review.

This test case verifies the sysfs interface syntax in general.
Relying on golden output can cause false negatives on older
kernels lacking support for newer sysfs policies.
Creating individual test cases for each sysfs interface is
unnecessary overhead.

With this approach, when needed, we use:

if _has_fs_sysfs_attr $dev <sysfs-interface>; then
     verify_sysfs_syntax <sysfs-interface> <value>
fi

- Anand