+ selftests-mm-cow-print-ksft-header-before-printing-anything-else.patch added to mm-hotfixes-unstable branch

+ selftests-mm-cow-print-ksft-header-before-printing-anything-else.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: selftests/mm: cow: print ksft header before printing anything else
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     selftests-mm-cow-print-ksft-header-before-printing-anything-else.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-cow-print-ksft-header-before-printing-anything-else.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: selftests/mm: cow: print ksft header before printing anything else
Date: Wed, 6 Dec 2023 11:35:58 +0100

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: f4b5fd6946e2 ("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>
---

 tools/testing/selftests/mm/cow.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/mm/cow.c~selftests-mm-cow-print-ksft-header-before-printing-anything-else
+++ a/tools/testing/selftests/mm/cow.c
@@ -1680,6 +1680,8 @@ int main(int argc, char **argv)
 {
 	int err;
 
+	ksft_print_header();
+
 	pagesize = getpagesize();
 	thpsize = read_pmd_pagesize();
 	if (thpsize)
@@ -1689,7 +1691,6 @@ int main(int argc, char **argv)
 						    ARRAY_SIZE(hugetlbsizes));
 	detect_huge_zeropage();
 
-	ksft_print_header();
 	ksft_set_plan(ARRAY_SIZE(anon_test_cases) * tests_per_anon_test_case() +
 		      ARRAY_SIZE(anon_thp_test_cases) * tests_per_anon_thp_test_case() +
 		      ARRAY_SIZE(non_anon_test_cases) * tests_per_non_anon_test_case());
_

Patches currently in -mm which might be from david@redhat.com are

selftests-mm-cow-print-ksft-header-before-printing-anything-else.patch