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Tue, 26 Aug 2025 12:49:32 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7375020043; Tue, 26 Aug 2025 12:49:32 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3056920040; Tue, 26 Aug 2025 12:49:30 +0000 (GMT) Received: from li-218185cc-29b5-11b2-a85c-9a1300ae2e6e.in.ibm.com (unknown [9.109.215.183]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 26 Aug 2025 12:49:29 +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, Donet Tom Subject: [PATCH 2/2] selftests/mm: add fork inheritance test for ksm_merging_pages counter Date: Tue, 26 Aug 2025 18:19:22 +0530 Message-ID: <88d6d5f08ff119625fa9accaa7b849dd77f9df25.1756211338.git.donettom@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2e662107e01417bf9af23bc7f52863cd538419be.1756211338.git.donettom@linux.ibm.com> References: <2e662107e01417bf9af23bc7f52863cd538419be.1756211338.git.donettom@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: VkolPkvh0DsD7H5lXlA_g6Umvua8Zct4 X-Proofpoint-ORIG-GUID: vWrApFb4qKyKmWTUoxuW81NgIsitET3J X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODIzMDAyMSBTYWx0ZWRfX+VxFFVNdJwl4 2AVY4r8Aycp0hT8Fv3v5EEMog5yTYcFmj08ERY1G+7kHPoG1EOInsASwjaUgsU+RqGxjW469Qh5 BVll4w45+mDSf9l0Wk53ekNYqXfmrOOLwXEZBt/VoYKwppG0C+8Bo/W/I6uGkrRdl2n43f3P2Gw z01EpUMVkMeccByikiQHFkpNEC0kUXeXo3Z/hJebPWQSnl2i7sIMn/xphIwd9wfGu7ipWm5BO76 kKPD0KA2jEO+gXr/1EFSqjy47W8rGS7i1le/xtp9Bm7EyoQJzj3oRlVXJ5Cyt5zEd1jnT1rXdPT 6aTd/mOZP9py9TNQtjXyp26tnC6OQ+dJxbIDkQ9Wsuk/jmf4OS1skcqgg/s5Hvwn0STrI/jXiv0 nVpOhPWB X-Authority-Analysis: v=2.4 cv=A8ZsP7WG c=1 sm=1 tr=0 ts=68adad61 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=2OwXVqhp2XgA:10 a=VnNF1IyMAAAA:8 a=mq3xLqhzurGmh3fbWqMA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-26_02,2025-08-26_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 priorityscore=1501 suspectscore=0 clxscore=1015 spamscore=0 impostorscore=0 malwarescore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508230021 Add a new selftest to verify whether the `ksm_merging_pages` counter in `mm_struct` is 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..d971394c9567 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(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) { + int mpages; + + init_global_file_handles(); + mpages = ksm_get_self_merging_pages(); + if (mpages > 0) + ksft_test_result_fail("ksm_merging_page in child: %d\n", mpages); + + exit(0); + } 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; + } + + 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 = open("/proc/self/mem", O_RDWR); @@ -620,7 +659,7 @@ static void init_global_file_handles(void) int main(int argc, char **argv) { - unsigned int tests = 8; + unsigned int tests = 9; int err; 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(); err = ksft_get_fail_cnt(); if (err) -- 2.51.0