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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: YCNmbhLy-s6QMExH8r-QNmM3LVWDhq35 X-Proofpoint-ORIG-GUID: Usxyx_aXpToUZfM8V5gW_Hqd6HlYMoj6 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODIzMDA3MSBTYWx0ZWRfX5jaV89N6LQJn A11Dun0fx97w01sjRhmsOyjj7Ztb2wEY7jLqcGfJ/95KwA65BkYhW49KPlj4c/PxWFzhSAb1za4 iFj31Njn6SUQA41/TyRgpspHrnnZlnShjpFogom8KlKBFcwQMnN2j3+r0bHwJD9Y0uHyySqTNu6 Abp7AeE1WOE1nwh9q5ELKHdBDA5tggNQfv/bwx4PkI5ohTXqu/P+nPTLRkV18R7/izfv5rKKTuk Pqp9df0wHjnTqWkJz4wKrCv8m9q68EUCmXSikqT/jS4JbZg33k7JD978bQLvlaaL6qIPxPlaDvD QyHxRRrZS5T7s+EJLi9UvYhraj2LSVZIcWtLP4XgDHRLxNTc5RG9RQmKWo16Z8bpCokXC6ArUFN ICq0Rsvj X-Authority-Analysis: v=2.4 cv=RtDFLDmK c=1 sm=1 tr=0 ts=68af4866 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=VnNF1IyMAAAA:8 a=BrG3DMFQotyEFiz2VCoA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 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=2025-08-27_04,2025-08-26_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 suspectscore=0 malwarescore=0 spamscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 phishscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508230071 Hi David On 8/26/25 6:52 PM, David Hildenbrand wrote: > On 26.08.25 14:49, Donet Tom wrote: >> Add a new selftest to verify whether the `ksm_merging_pages` counter > > "to verify ... is *not* inherited" ? > I will change it in next version. > > >> 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"); > > Won't this trigger a fail in the child and a pass in the parent process? > > You should likely instead let the child return the result (or the > number) and check that here. Thanks for pointing this out. I will make the change in the next version