On Thu, 18 Dec 2025 at 15:20, Ojaswin Mujoo <[email protected]> wrote: > > On Wed, Dec 17, 2025 at 08:47:57PM +0530, Ojaswin Mujoo wrote: > > Hello, > > > > While writing some Kunit tests for ext4 filesystem, I'm encountering an > > issue in the way we display the diagnostic logs upon failures, when > > using KUNIT_CASE_PARAM() to write the tests. > > > > This can be observed by patching fs/ext4/mballoc-test.c to fail > > and print one of the params: > > > > --- a/fs/ext4/mballoc-test.c > > +++ b/fs/ext4/mballoc-test.c > > @@ -350,6 +350,8 @@ static int mbt_kunit_init(struct kunit *test) > > struct super_block *sb; > > int ret; > > > > + KUNIT_FAIL(test, "Failed: blocksize_bits=%d", > > layout->blocksize_bits); > > + > > sb = mbt_ext4_alloc_super_block(); > > if (sb == NULL) > > return -ENOMEM; > > > > With the above change, we can observe the following output (snipped): > > > > [18:50:25] ============== ext4_mballoc_test (7 subtests) ============== > > [18:50:25] ================= test_new_blocks_simple ================== > > [18:50:25] [FAILED] block_bits=10 cluster_bits=3 blocks_per_group=8192 > > group_count=4 desc_size=64 > > [18:50:25] # test_new_blocks_simple: EXPECTATION FAILED at > > fs/ext4/mballoc-test.c:364 > > [18:50:25] Failed: blocksize_bits=12 > > [18:50:25] [FAILED] block_bits=12 cluster_bits=3 blocks_per_group=8192 > > group_count=4 desc_size=64 > > [18:50:25] # test_new_blocks_simple: EXPECTATION FAILED at > > fs/ext4/mballoc-test.c:364 > > [18:50:25] Failed: blocksize_bits=16 > > [18:50:25] [FAILED] block_bits=16 cluster_bits=3 blocks_per_group=8192 > > group_count=4 desc_size=64 > > [18:50:25] # test_new_blocks_simple: EXPECTATION FAILED at > > fs/ext4/mballoc-test.c:364 > > [18:50:25] Failed: blocksize_bits=10 > > [18:50:25] # test_new_blocks_simple: pass:0 fail:3 skip:0 total:3 > > [18:50:25] ============= [FAILED] test_new_blocks_simple ============== > > <snip> > > > > Note that the diagnostic logs don't show up correctly. Ideally they > > should be before test result but here the first [FAILED] test has no > > logs printed above whereas the last "Failed: blocksize_bits=10" print > > comes after the last subtest, when it actually corresponds to the first > > subtest. > > > > The KTAP file itself seems to have diagnostic logs in the right place: > > > > KTAP version 1 > > 1..2 > > KTAP version 1 > > # Subtest: ext4_mballoc_test > > # module: ext4 > > 1..7 > > KTAP version 1 > > # Subtest: test_new_blocks_simple > > So looking into this a bit more and comparing the parameterized output > with non parameterized output, I'm seeing that the difference is that > output via KUNIT_CASE_PARAM is not printing the test plan line right > here. This plan sort of serves as divider between the parent and the 3 > children's logs and without it our parsing logic gets confused. When I > manually added a "1..3" test plan I could see the parsing work correctly > without any changes to kunit_parser.py. >
Thanks for looking into this! There's been a bit of back-and-forth on how to include the test plan line for the parameterised tests: it's not always possible to know how many times a test will run in advance if the gen_params function is particularly complicated. We did have a workaround where array parameters would record the array size, but there were a couple of tests which were wrapping the gen_params function to skip / add entries which weren't in the array. One "fix" would be to use KUNIT_CASE_PARAM_WITH_INIT() and have an init function which calls kunit_register_params_array(), and then use kunit_array_gen_params() as the generator function: this has an escape hatch which will print the test plan. Otherwise, as a hack, you could effectively revert https://lore.kernel.org/linux-kselftest/[email protected]/ — which would fix the issue (but break some other tests). Going through and fixing this properly has been on my to-do list; with some combination of fixing tests which modify the gen_params function and improving the parsing to better handle cases without the test plan. Cheers, -- David > > # test_new_blocks_simple: EXPECTATION FAILED at > > fs/ext4/mballoc-test.c:364 > > Failed: blocksize_bits=10 > > not ok 1 block_bits=10 cluster_bits=3 blocks_per_group=8192 > > group_count=4 desc_size=64 > > # test_new_blocks_simple: EXPECTATION FAILED at > > fs/ext4/mballoc-test.c:364 > > Failed: blocksize_bits=12 > > not ok 2 block_bits=12 cluster_bits=3 blocks_per_group=8192 > > group_count=4 desc_size=64 > > # test_new_blocks_simple: EXPECTATION FAILED at > > fs/ext4/mballoc-test.c:364 > > Failed: blocksize_bits=16 > > not ok 3 block_bits=16 cluster_bits=3 blocks_per_group=8192 > > group_count=4 desc_size=64 > > # test_new_blocks_simple: pass:0 fail:3 skip:0 total:3 > > not ok 1 test_new_blocks_simple > > <snip> > > > > By tracing kunit_parser.py script, I could see the issue here is in the > > parsing of the "Subtest: test_new_blocks_simple". We end up associating > > everything below the subtest till "not ok 1 block_bits=10..." as > > diagnostic logs of the subtest, while these lons actually belong to the > > first of the 3 subtests under this test. > >
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