ublk: prepare basic smoke tests to complement exisiting tests in blktests and kselftests

[schlad]

The idea is simple - prepare basic smoke-like tests for ublk.
There is existing test coverage in blktests and most notably in kselftests, however the tests in kselftests are very detailed.
The missing part is to have basic test coverage for ublk which could be easily run as some sort of system regression test.

The task which I will work on is to exactly introduce such test.

Assignee: @schlad

[schlad]

FYI: this looks good in fact: https://github.com/linux-blktests/blktests/tree/master/tests/ublk

[schlad]

sorry then for the noise then. After all I think it does not make sense to add ublk smoke tests to the LTP give the coverage in blktests.
I would be replicating what blktests does on such some-type level.
And if we ever want detailed tests - kselftests is the way to go.

[schlad]

I'm inclined to close it as duplicate (in blktests).

[metan-ucw]

I looked at the coverage and I think that we can still write meaningful test in LTP. If we use our .all_filesystems flag for a simple test that formats an ublk device with a filesystem we will test it with filesystems that are not tested in other testsuites (as far as I can tell) including FUSE based ones, which is interesting corner case.