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Mon, 15 Sep 2025 15:03:20 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C08CD20043; Mon, 15 Sep 2025 15:03:20 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 01F6720040; Mon, 15 Sep 2025 15:03:18 +0000 (GMT) Received: from li-218185cc-29b5-11b2-a85c-9a1300ae2e6e.in.ibm.com (unknown [9.109.215.183]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 15 Sep 2025 15:03:17 +0000 (GMT) From: Donet Tom To: Andrew Morton , David Hildenbrand Cc: Ritesh Harjani , Xu Xin , Chengming Zhou , Wei Yang , Aboorva Devarajan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Giorgi Tchankvetadze , Donet Tom Subject: [PATCH v2 2/3] selftests/mm: Added fork inheritance test for ksm_merging_pages counter Date: Mon, 15 Sep 2025 20:33:05 +0530 Message-ID: X-Mailer: git-send-email 2.51.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=BKWzrEQG c=1 sm=1 tr=0 ts=68c82ac0 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=yJojWOMRYYMA:10 a=VnNF1IyMAAAA:8 a=kDUdi5sUuU8vu5WplE8A:9 X-Proofpoint-GUID: j3U2VRkqQn4XzAtJobpMyJIcM65S50IL X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTE1MDA4NiBTYWx0ZWRfX+owsqfDsyOJT wra/dfkNFMg0Aty67SOAVFn9WPu+ZedniDZ1oBpVSg2IO4QeaJMdd1d8CABWjTR8imZ7wyY3FNY kcDXuTvCPt7L3gvm8I079Djz4yVUEKvkTbb+Egj2wXAX6UzpJi7CuWy64jl9eLjD7RcQl8KgF0l G9gLpuM1x4xYLKWKxbfSYOdKBOw5QXqoy6Ot/oy1RURKb9a/XoI3WwlivENzn8kd1Va+wVH/+qH x5oTE/kfbFC/KThIl7iGI1heWEj7V4tBBCTRzWJFxvrYexNIW3Gu1NkowN97kE3HNURwuYdpupl 7tO2/IHhEy1CafLDNgUIlB0oPznV6OBo2rlvuO1lREtdh+4fKWDUqn2Cmiq4wxjuBqW8CXHH2VH XBCQKQj4 X-Proofpoint-ORIG-GUID: UVh9NO6MTXzI6hFy_IMba7QcotMBbCPF 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=2025-09-15_05,2025-09-12_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 malwarescore=0 priorityscore=1501 adultscore=0 suspectscore=0 impostorscore=0 bulkscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509150086 Content-Type: text/plain; charset="utf-8" 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 Acked-by: David Hildenbrand --- .../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/test= ing/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); } =20 +static void test_fork_ksm_merging_page_count(void) +{ + const unsigned int size =3D 2 * MiB; + char *map; + pid_t child_pid; + int status; + + ksft_print_msg("[RUN] %s\n", __func__); + + map =3D mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERG= E_MADVISE); + if (map =3D=3D MAP_FAILED) + return; + + child_pid =3D 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; + } + + if (waitpid(child_pid, &status, 0) < 0) { + ksft_test_result_fail("waitpid() failed\n"); + return; + } + + status =3D 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"); + + ksm_stop(); + munmap(map, size); +} + static void init_global_file_handles(void) { mem_fd =3D open("/proc/self/mem", O_RDWR); @@ -620,7 +659,7 @@ static void init_global_file_handles(void) =20 int main(int argc, char **argv) { - unsigned int tests =3D 8; + unsigned int tests =3D 9; int err; =20 if (argc > 1 && !strcmp(argv[1], FORK_EXEC_CHILD_PRG_NAME)) { @@ -652,6 +691,7 @@ int main(int argc, char **argv) test_prctl_fork(); test_prctl_fork_exec(); test_prctl_unmerge(); + test_fork_ksm_merging_page_count(); =20 err =3D ksft_get_fail_cnt(); if (err) --=20 2.51.0