Re: [PATCH 08/28] check-parallel: add logwrite device support

["Nirjhar Roy (IBM)" <nirjhar.roy.lists@gmail.com>]

On 5/21/25 15:37, Dave Chinner wrote:
> On Wed, May 07, 2025 at 01:48:03PM +0530, Nirjhar Roy (IBM) wrote:
>> On Thu, 2025-04-17 at 13:00 +1000, Dave Chinner wrote:
>>> From: Dave Chinner <dchinner@redhat.com>
>>>
>>> Every logwrite test will use the same /dev/mapper/<dev>
>>> name for the logwrites device, so we also need to convert
>>> common/dmlogwrite to use per-test device names as we have done for
>>> other dm devices.
>>>
>>> Then add a per-test-runner LOGWRITES_DEV so that all tests using
>>> dm-logwrites now get run by check-parallel.
>>>
>>> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> .....
>>> diff --git a/common/dmlogwrites b/common/dmlogwrites
>>> index a27e1966a..7c3ad95c9 100644
>>> --- a/common/dmlogwrites
>>> +++ b/common/dmlogwrites
>>> @@ -4,6 +4,9 @@
>>>   #
>>>   # common functions for setting up and tearing down a dm log-writes device
>>>   
>>> +LOGWRITES_NAME=logwrites-$seq
>> if 2 different runners are running tests with the same $seq, won't
>> there be a conflict? For example runner-0 is running xfs/xyz and
>> runner-1 is running generic/xyz ?
> Yes, it could happen, but it won't happen right now as there is no
> overlap in test numbers using dmlogwrites between different test
> directories.
>
> I do need to solve this generically (i.e. for all the dm device
> types) in the near future because I want to be able to run the same
> test N times in parallel. e.g do flakey test profiling really
> quickly over thousands of iterations by running 64 instances of the
> test at the same time.
>
> For this use case, the dm device name cannot rely on the test
> name/sequence number at all, and so I'm going to have to come up
> with a unique ID of some kind for this purpose. It may be as simple
> as encoding the unique runner ID along with the test sequence number
> into the device name - it's not a difficult issue to solve.
>
> Hence I haven't spent much more thought on it than that, because
> I've answered the two main questions that were relevant: "can
> I solve it?" (yes) and "do I need to solve it now?" (no).

Okay. Yes, I just wanted to point this out and confirm if my 
understanding is correct.

--NR

>
> -Dave.

-- 
Nirjhar Roy
Linux Kernel Developer
IBM, Bangalore