On Thu, Dec 18, 2025 at 04:58:33PM +0800, David Gow wrote: > 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
Hi David, Thanks for the workaround, KUNIT_CASE_PARAM_WITH_INIT() did the trick! So I'm just wondering if it makes sense to still have a placeholder test plan line in cases we can't determine the number of tests. I think something like 1..X should be enough to not throw off the parsing. (Although I think this might not be exactly compliant to KTAP). Regards, ojaswin > > > > # 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. > > >
