netdev - Re: [PATCH net-next v2 1/2] selftests: net-drv: exercise queue stats when the device is down

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Message-ID: <87cymt7pmu.fsf@nvidia.com>
Date: Wed, 31 Jul 2024 13:34:58 +0200
From: Petr Machata <petrm@...dia.com>
To: Stanislav Fomichev <sdf@...ichev.me>
CC: <netdev@...r.kernel.org>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>, "Joe
 Damato" <jdamato@...tly.com>, Petr Machata <petrm@...dia.com>,
	<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH net-next v2 1/2] selftests: net-drv: exercise queue
 stats when the device is down


Stanislav Fomichev <sdf@...ichev.me> writes:

> Verify that total device stats don't decrease after it has been turned down.
> Also make sure the device doesn't crash when we access per-queue stats
> when it's down (in case it tries to access some pointers that are NULL).
>
>   KTAP version 1
>   1..5
>   ok 1 stats.check_pause
>   ok 2 stats.check_fec
>   ok 3 stats.pkt_byte_sum
>   ok 4 stats.qstat_by_ifindex
>   ok 5 stats.check_down
>   # Totals: pass:5 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> v2:
> - KTAP output formatting (Jakub)
> - defer instead of try/finally (Jakub)
> - disappearing stats is an error (Jakub)
> - ksft_ge instead of open coding (Jakub)
>
> Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
> --
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Joe Damato <jdamato@...tly.com>
> Cc: Petr Machata <petrm@...dia.com>
> Cc: linux-kselftest@...r.kernel.org
> ---
>  tools/testing/selftests/drivers/net/stats.py | 25 +++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/drivers/net/stats.py b/tools/testing/selftests/drivers/net/stats.py
> index 820b8e0a22c6..93f9204f51c4 100755
> --- a/tools/testing/selftests/drivers/net/stats.py
> +++ b/tools/testing/selftests/drivers/net/stats.py
> @@ -5,6 +5,7 @@ from lib.py import ksft_run, ksft_exit, ksft_pr
>  from lib.py import ksft_ge, ksft_eq, ksft_in, ksft_true, ksft_raises, KsftSkipEx, KsftXfailEx
>  from lib.py import EthtoolFamily, NetdevFamily, RtnlFamily, NlError
>  from lib.py import NetDrvEnv
> +from lib.py import ip, defer
>  
>  ethnl = EthtoolFamily()
>  netfam = NetdevFamily()
> @@ -133,9 +134,31 @@ rtnl = RtnlFamily()
>      ksft_eq(cm.exception.nl_msg.extack['bad-attr'], '.ifindex')
>  
>  
> +def check_down(cfg) -> None:
> +    try:
> +        qstat = netfam.qstats_get({"ifindex": cfg.ifindex}, dump=True)
> +    except NlError as e:
> +        if e.error == 95:

Could you do this as if e.error == errno.ENOTSUP?

> +            raise KsftSkipEx("qstats not supported by the device")
> +        raise
> +
> +    ip(f"link set dev {cfg.dev['ifname']} down")
> +    defer(ip, f"link set dev {cfg.dev['ifname']} up")
> +
> +    qstat = qstat[0]

Consider moving the [0] inside the try to make the two qstats_get
statements obviously the same.

> +    qstat2 = netfam.qstats_get({"ifindex": cfg.ifindex}, dump=True)[0]
> +    for k, v in qstat.items():
> +        ksft_ge(qstat2[k], qstat[k], comment=f"{k} went backwards on device down")
> +
> +    # exercise per-queue API to make sure that "device down" state
> +    # is handled correctly and doesn't crash
> +    netfam.qstats_get({"ifindex": cfg.ifindex, "scope": "queue"}, dump=True)
> +
> +
>  def main() -> None:
>      with NetDrvEnv(__file__) as cfg:
> -        ksft_run([check_pause, check_fec, pkt_byte_sum, qstat_by_ifindex],
> +        ksft_run([check_pause, check_fec, pkt_byte_sum, qstat_by_ifindex,
> +                  check_down],
>                   args=(cfg, ))
>      ksft_exit()