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[ Upstream commita6fcd57cf2] Doing a ksft_print_msg() before the ksft_print_header() seems to confuse the ksft framework in a strange way: running the test on the cmdline results in the expected output. But piping the output somewhere else, results in some odd output, whereby we repeatedly get the same info printed: # [INFO] detected THP size: 2048 KiB # [INFO] detected hugetlb page size: 2048 KiB # [INFO] detected hugetlb page size: 1048576 KiB # [INFO] huge zeropage is enabled TAP version 13 1..190 # [INFO] Anonymous memory tests in private mappings # [RUN] Basic COW after fork() ... with base page # [INFO] detected THP size: 2048 KiB # [INFO] detected hugetlb page size: 2048 KiB # [INFO] detected hugetlb page size: 1048576 KiB # [INFO] huge zeropage is enabled TAP version 13 1..190 # [INFO] Anonymous memory tests in private mappings # [RUN] Basic COW after fork() ... with base page ok 1 No leak from parent into child # [RUN] Basic COW after fork() ... with swapped out base page # [INFO] detected THP size: 2048 KiB # [INFO] detected hugetlb page size: 2048 KiB # [INFO] detected hugetlb page size: 1048576 KiB # [INFO] huge zeropage is enabled Doing the ksft_print_header() first seems to resolve that and gives us the output we expect: TAP version 13 # [INFO] detected THP size: 2048 KiB # [INFO] detected hugetlb page size: 2048 KiB # [INFO] detected hugetlb page size: 1048576 KiB # [INFO] huge zeropage is enabled 1..190 # [INFO] Anonymous memory tests in private mappings # [RUN] Basic COW after fork() ... with base page ok 1 No leak from parent into child # [RUN] Basic COW after fork() ... with swapped out base page ok 2 No leak from parent into child # [RUN] Basic COW after fork() ... with THP ok 3 No leak from parent into child # [RUN] Basic COW after fork() ... with swapped-out THP ok 4 No leak from parent into child # [RUN] Basic COW after fork() ... with PTE-mapped THP ok 5 No leak from parent into child Link: https://lkml.kernel.org/r/20231206103558.38040-1-david@redhat.com Fixes:f4b5fd6946("selftests/vm: anon_cow: THP tests") Signed-off-by: David Hildenbrand <david@redhat.com> Reported-by: Nico Pache <npache@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>