From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konstantin Khorenko Date: Fri, 14 Aug 2026 18:24:25 +0200 Subject: [Devel] [PATCH RHEL10 COMMIT] selftests/core: fix unshare_test with large fs.nr_open In-Reply-To: <20260814161852.278262-2-khorenko@virtuozzo.com> Message-ID: <202608141624.67EGOP7F278691@f0.sw.ru> List-Id: The commit is pushed to "branch-rh10-6.12.0-211.39.1.16.x.vz10-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git after rh10-6.12.0-211.39.1.16.4.vz10 ------> commit cade8d2ddfe60d4ea67bc95b44ea9ed0585989ab Author: Eva Kurchatova Date: Fri Aug 14 14:35:43 2026 +0200 selftests/core: fix unshare_test with large fs.nr_open The test assumes fs.nr_open is close to the default 1048576, but some systems set it much higher (e.g. 1073741816). This is systemd's doing: since systemd v240 (2018), PID 1 bumps fs.nr_open and fs.file-max to their largest possible values on boot, as file descriptors are already accounted for by memcg [1]. In that case, dup2() to nr_open + 64 requires the kernel to allocate a file descriptor table with ~1 billion entries, which fails with ENOMEM. Cap the nr_open value used for the test's own arithmetic to a known reasonable base value (1048576) and restore the true original value once the test has completed. [1] https://github.com/systemd/systemd/commit/a8b627aaed409a15260c25988970c795bf963812 ("main: bump fs.nr_open + fs.max-file to their largest possible values") https://virtuozzo.atlassian.net/browse/VSTOR-132444 Feature: fix kselftests Signed-off-by: Eva Kurchatova Signed-off-by: Konstantin Khorenko --- tools/testing/selftests/core/unshare_test.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/core/unshare_test.c b/tools/testing/selftests/core/unshare_test.c index 7fec9dfb1b0e3..6716e0f74d7da 100644 --- a/tools/testing/selftests/core/unshare_test.c +++ b/tools/testing/selftests/core/unshare_test.c @@ -40,6 +40,14 @@ TEST(unshare_EMFILE) ASSERT_EQ(sscanf(buf, "%d", &nr_open), 1); + /* + * Cap nr_open for the duration of the test to avoid ENOMEM from a + * huge fd table allocation; buf/n keep the real original value so + * fs.nr_open can be restored to it once the test is done. + */ + if (nr_open > 1024 * 1024) + nr_open = 1024 * 1024; + ASSERT_EQ(0, getrlimit(RLIMIT_NOFILE, &rlimit)); /* bump fs.nr_open */ @@ -73,10 +81,13 @@ TEST(unshare_EMFILE) if (pid == 0) { int err; + char buf3[32]; + ssize_t n3; - /* restore fs.nr_open */ + /* restore fs.nr_open to the (possibly capped) test baseline */ + n3 = sprintf(buf3, "%d\n", nr_open); lseek(fd, 0, SEEK_SET); - write(fd, buf, n); + write(fd, buf3, n3); /* ... and now unshare(CLONE_FILES) must fail with EMFILE */ err = unshare(CLONE_FILES); EXPECT_EQ(err, -1) @@ -89,6 +100,10 @@ TEST(unshare_EMFILE) EXPECT_EQ(waitpid(pid, &status, 0), pid); EXPECT_EQ(true, WIFEXITED(status)); EXPECT_EQ(0, WEXITSTATUS(status)); + + /* restore the real fs.nr_open value */ + lseek(fd, 0, SEEK_SET); + write(fd, buf, n); } TEST_HARNESS_MAIN