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Wed, 17 Sep 2025 14:46:03 GMT Received: from smtpav06.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D48C558060; Wed, 17 Sep 2025 14:46:02 +0000 (GMT) Received: from smtpav06.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A8ACA58055; Wed, 17 Sep 2025 14:45:59 +0000 (GMT) Received: from [9.109.215.183] (unknown [9.109.215.183]) by smtpav06.wdc07v.mail.ibm.com (Postfix) with ESMTP; Wed, 17 Sep 2025 14:45:59 +0000 (GMT) Message-ID: <659ba2d4-fee3-410d-b611-04a3586b5bb7@linux.ibm.com> Date: Wed, 17 Sep 2025 20:15:57 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] selftests/mm: Added fork inheritance test for ksm_merging_pages counter To: David Hildenbrand , Andrew Morton Cc: Ritesh Harjani , Xu Xin , Chengming Zhou , Wei Yang , Aboorva Devarajan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Giorgi Tchankvetadze References: <26e38fe5-e6c4-4678-8056-95c0ff4350e6@redhat.com> Content-Language: en-US From: Donet Tom In-Reply-To: <26e38fe5-e6c4-4678-8056-95c0ff4350e6@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTE2MDIwNCBTYWx0ZWRfXwnycUZ3Fld+5 2YguMIDES/qowsvDjfe2GgPNRUMYd+a7ylomoGYeDDs82zO7tkSbrFmXCBIV5cJYqoQoxNamT+l F0q5Jm28Hv92BRPZ1HRy9xYfG7qDwp73ijaOLOE5MP0bau/2VL86gKFoHsSnKGaTPbIWcvbbdjQ WbQ+lymbj7V9dYZ8xNAq1kfwveu0YegRjHPJmo5v2zZG5lWW+Fj/eT8FjjIy9yJFovAqwPJIFIZ Xf6Lp1GIgyFovlRCxZJZ/QxzBxmQYEQ6WlnqTndi1lfkJmINtOlWwspS3BE9y/PrCRt8F7PQs3h j9HQmxvgOL3HoHXTDZxrMNN7lJIwS6c4+lPp8bTm9EUD9WeOo5Ji9ITacNA2JPuRxpnbcT6aMVU RVCc6QbR X-Proofpoint-ORIG-GUID: 8VeRrE0Wp5XNH9_jmiJFajk_m7pZrsbs X-Proofpoint-GUID: cPyzT-UFtYtpAzuBmZiqRj02G87oK7XS X-Authority-Analysis: v=2.4 cv=cNzgskeN c=1 sm=1 tr=0 ts=68cac9ad cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=yJojWOMRYYMA:10 a=VnNF1IyMAAAA:8 a=20KFwNOVAAAA:8 a=Z4megsD6RVqFqqBZ_rsA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-17_01,2025-09-17_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1015 spamscore=0 bulkscore=0 malwarescore=0 adultscore=0 priorityscore=1501 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509160204 On 9/17/25 6:45 PM, David Hildenbrand wrote: > On 15.09.25 17:03, Donet Tom wrote: >> Added a new selftest to verify whether the `ksm_merging_pages` counter >> in `mm_struct` is not inherited by a child process after fork. This >> helps >> ensure correctness of KSM accounting across process creation. >> >> Signed-off-by: Donet Tom >> --- >>   .../selftests/mm/ksm_functional_tests.c       | 42 ++++++++++++++++++- >>   1 file changed, 41 insertions(+), 1 deletion(-) >> >> diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c >> b/tools/testing/selftests/mm/ksm_functional_tests.c >> index 712f43c87736..645cefba2126 100644 >> --- a/tools/testing/selftests/mm/ksm_functional_tests.c >> +++ b/tools/testing/selftests/mm/ksm_functional_tests.c >> @@ -602,6 +602,45 @@ static void test_prot_none(void) >>       munmap(map, size); >>   } >>   +static void test_fork_ksm_merging_page_count(void) >> +{ >> +    const unsigned int size = 2 * MiB; >> +    char *map; >> +    pid_t child_pid; >> +    int status; >> + >> +    ksft_print_msg("[RUN] %s\n", __func__); >> + >> +    map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, >> KSM_MERGE_MADVISE); >> +    if (map == MAP_FAILED) >> +        return; >> + >> +    child_pid = fork(); >> +    if (!child_pid) { >> +        init_global_file_handles(); >> +        exit(ksm_get_self_merging_pages()); >> +    } else if (child_pid < 0) { >> +        ksft_test_result_fail("fork() failed\n"); >> +        return; > > Probably >     goto out; > > in all these fail cases > >> +    } >> + >> +    if (waitpid(child_pid, &status, 0) < 0) { >> +        ksft_test_result_fail("waitpid() failed\n"); >> +        return; >> +    } >> + >> +    status = WEXITSTATUS(status); >> +    if (status) { >> +        ksft_test_result_fail("ksm_merging_page in child: %d\n", >> status); >> +        return; >> +    } >> + >> +    ksft_test_result_pass("ksm_merging_pages is not inherited after >> fork\n"); >> + > > And have > >     out: > > here Sure, I will send a v3 with this change. > > With that: > > Acked-by: David Hildenbrand >