linux-kernel - Re: [PATCH 3/3] selftests: ublk: add test to verify that feat

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Message-ID: <aMsIJXDRhkRWDH1m@dev-ushankar.dev.purestorage.com>
Date: Wed, 17 Sep 2025 13:12:37 -0600
From: Uday Shankar <ushankar@...estorage.com>
To: Ming Lei <ming.lei@...hat.com>
Cc: Caleb Sander Mateos <csander@...estorage.com>,
	Shuah Khan <shuah@...nel.org>, linux-block@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] selftests: ublk: add test to verify that feat_map is
 complete

On Wed, Sep 17, 2025 at 11:52:38AM +0800, Ming Lei wrote:
> On Tue, Sep 16, 2025 at 04:05:57PM -0600, Uday Shankar wrote:
> > Add a test that verifies that the currently running kernel does not
> > report support for any features that are unrecognized by kublk. This
> > should catch cases where features are added without updating kublk's
> > feat_map accordingly, which has happened multiple times in the past (see
> > [1], [2]).
> > 
> > Note that this new test may fail if the test suite is older than the
> > kernel, and the newer kernel contains a newly introduced feature. I
> > believe this is not a use case we currently care about - we only care
> > about newer test suites passing on older kernels.
> > 
> > [1] https://lore.kernel.org/linux-block/20250606214011.2576398-1-csander@purestorage.com/t/#u
> > [2] https://lore.kernel.org/linux-block/2a370ab1-d85b-409d-b762-f9f3f6bdf705@nvidia.com/t/#m1c520a058448d594fd877f07804e69b28908533f
> > 
> > Signed-off-by: Uday Shankar <ushankar@...estorage.com>
> > ---
> >  tools/testing/selftests/ublk/Makefile           |  1 +
> >  tools/testing/selftests/ublk/test_generic_13.sh | 16 ++++++++++++++++
> >  2 files changed, 17 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/ublk/Makefile b/tools/testing/selftests/ublk/Makefile
> > index 5d7f4ecfb81612f919a89eb442f948d6bfafe225..770269efe42ab460366485ccc80abfa145a0c57b 100644
> > --- a/tools/testing/selftests/ublk/Makefile
> > +++ b/tools/testing/selftests/ublk/Makefile
> > @@ -20,6 +20,7 @@ TEST_PROGS += test_generic_09.sh
> >  TEST_PROGS += test_generic_10.sh
> >  TEST_PROGS += test_generic_11.sh
> >  TEST_PROGS += test_generic_12.sh
> > +TEST_PROGS += test_generic_13.sh
> >  
> >  TEST_PROGS += test_null_01.sh
> >  TEST_PROGS += test_null_02.sh
> > diff --git a/tools/testing/selftests/ublk/test_generic_13.sh b/tools/testing/selftests/ublk/test_generic_13.sh
> > new file mode 100755
> > index 0000000000000000000000000000000000000000..ff5f22b078ddd08bc19f82aa66da6a44fa073f6f
> > --- /dev/null
> > +++ b/tools/testing/selftests/ublk/test_generic_13.sh
> > @@ -0,0 +1,16 @@
> > +#!/bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +. "$(cd "$(dirname "$0")" && pwd)"/test_common.sh
> > +
> > +TID="generic_13"
> > +ERR_CODE=0
> > +
> > +_prep_test "null" "check that feature list is complete"
> > +
> > +if ${UBLK_PROG} features | grep -q unknown; then
> > +        ERR_CODE=255
> > +fi
> > +
> > +_cleanup_test "null"
> > +_show_result $TID $ERR_CODE
> 
> What if the ublk selftest is run on downstream kernel?
> 
> Maybe the output can changed to "unsupported" to show that ublk selftest
> code doesn't cover or use this feature.

Yes I pointed out this issue in the commit message too. But I am unsure
what you're asking for.

I think we need a failure here if this test is to fulfill its intended
purposes (catching cases where a feature is added without updating the
feat_map in kublk). This does also cause failures in cases where an old
test suite is run against a newer kernel. Since I think this is an
unusual case, perhaps I can add a log line when this test fails saying
that the failure is expected if running an old test suite against a new
kernel?