linux-kernel - Re: [PATCH v4 3/3] configfs: Add unit tests

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Date:   Mon, 9 Aug 2021 11:31:23 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Christoph Hellwig <hch@....de>
Cc:     Joel Becker <jlbec@...lplan.org>, linux-kernel@...r.kernel.org,
        Bodo Stroesser <bostroesser@...il.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Yanko Kaneti <yaneti@...lera.com>
Subject: Re: [PATCH v4 3/3] configfs: Add unit tests

On 8/9/21 7:59 AM, Christoph Hellwig wrote:
>> text and binary attribute support. This is how I run these tests:
>>
>> set -e
>> if [ -e .config ]; then
>>     make ARCH=um mrproper
>> fi
>> if [ ! -e .kunit/.kunitconfig ]; then
>>     cat <<EOF >.kunit/.kunitconfig
>> CONFIG_CONFIGFS_FS=y
>> CONFIG_CONFIGFS_KUNIT_TEST=y
>> CONFIG_KUNIT=y
>> CONFIG_PROVE_LOCKING=y
>> CONFIG_SYSFS=y
>> CONFIG_UBSAN=y
>> EOF
>>     cp .kunit/.kunitconfig .kunit/.config
>> fi
>> ./tools/testing/kunit/kunit.py run
> 
> This is very useful documentation, but shouldn't it go into a README.kunit
> or similar instead of a commit message?

I can store this documentation in a new README, but isn't this something
that has already been explained in
Documentation/dev-tools/kunit/kunit-tool.rst?

>> +config CONFIGFS_KUNIT_TEST
>> +	bool "Configfs Kunit test" if !KUNIT_ALL_TESTS
>> +	depends on CONFIGFS_FS && KUNIT=y
>> +	default KUNIT_ALL_TESTS
> 
> Why does it depend on KUNIT=y?  What is the issue with a modular KUNIT
> build?

The unit tests calls do_mount(). do_mount() has not been exported and
hence is not available to kernel modules. Hence the exclusion of KUNIT=m.

>> +static int mkdir(const char *name, umode_t mode)
>> +{
>> +	struct dentry *dentry;
>> +	struct path path;
>> +	int err;
>> +
>> +	err = get_file_mode(name);
>> +	if (err >= 0 && S_ISDIR(err))
>> +		return 0;
>> +
>> +	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
>> +	if (IS_ERR(dentry))
>> +		return PTR_ERR(dentry);
>> +
>> +	err = vfs_mkdir(&init_user_ns, d_inode(path.dentry), dentry, mode);
>> +	done_path_create(&path, dentry);
> 
> To me this sounds like userspace would be a better place for these
> kinds of tests.

Splitting the code that can only be run from inside the kernel (creation
of configfs attributes) and the code that can be run from user space and
making sure that the two run in a coordinated fashion would involve a
significant amount of work. I prefer to keep the current approach.

Thanks,

Bart.