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Tue, 03 Feb 2026 10:16:22 -0800 (PST) Received: from localhost.localdomain ([59.16.109.172]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35485eb8dc6sm313230a91.9.2026.02.03.10.16.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Feb 2026 10:16:22 -0800 (PST) From: Jinseok Kim To: shuah@kernel.org Cc: Jan Kara , Amir Goldstein , Matthew Bobrowski , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [RFC PATCH] selftests: fanotify: Add basic create/modify/delete event test Date: Wed, 4 Feb 2026 03:15:43 +0900 Message-ID: <20260203181549.21750-1-always.starving0@gmail.com> X-Mailer: git-send-email 2.43.0 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 Content-Type: text/plain; charset="utf-8" Hello, Currently there are almost no automated selftests for fanotify notification events in tools/testing/selftests/ (only mount namespace related tests exist). This patch adds a very basic selftest that exercises three fundamental fanotify events: - FAN_CREATE (file creation) - FAN_MODIFY (file content modification via write()) - FAN_DELETE (file removal) The test - creates a test file, appends data, and removes it - verifies that corresponding events are received and the masks contain the expected bits (0x100, 0x2, 0x200) Test TAP output: ok 1 FAN_CREATE detected ok 2 FAN_MODIFY detected ok 3 FAN_DELETE detected # PASSED: 1 / 1 tests passed. This is intentionally kept minimal as a starting point. Future work ideas (not in this patch): - Test permission events - Test rename/move events - Verify file names - Run under different filesystems Any feedback on the direction, style, or additional test cases would be greatly appreciated. Thanks, Jinseok. Signed-off-by: Jinseok Kim --- tools/testing/selftests/filesystems/Makefile | 7 + .../selftests/filesystems/fanotify_basic.c | 122 ++++++++++++++++++ 2 files changed, 129 insertions(+) create mode 100644 tools/testing/selftests/filesystems/Makefile create mode 100644 tools/testing/selftests/filesystems/fanotify_basic.c diff --git a/tools/testing/selftests/filesystems/Makefile b/tools/testing/s= elftests/filesystems/Makefile new file mode 100644 index 0000000..c0e0242 --- /dev/null +++ b/tools/testing/selftests/filesystems/Makefile @@ -0,0 +1,7 @@ +# SPDX-License-Identifier: GPL-2.0 + +CFLAGS +=3D $(KHDR_INCLUDES) +TEST_GEN_PROGS :=3D devpts_pts file_stressor anon_inode_test kernfs_test f= clog fanotify_basic +TEST_GEN_PROGS_EXTENDED :=3D dnotify_test + +include ../lib.mk diff --git a/tools/testing/selftests/filesystems/fanotify_basic.c b/tools/t= esting/selftests/filesystems/fanotify_basic.c new file mode 100644 index 0000000..4a4fbb4 --- /dev/null +++ b/tools/testing/selftests/filesystems/fanotify_basic.c @@ -0,0 +1,122 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include +#include +#include +#include +#include "../kselftest_harness.h" +#include "wrappers.h" + +static void create_file(const char *filename) +{ + int fd; + int ret; + + fd =3D open(filename, O_CREAT | O_WRONLY | O_TRUNC, 0644); + if (fd =3D=3D -1) + ksft_exit_fail_msg("(create)open failed: %s\n", strerror(errno)); + ret =3D write(fd, "create_file", 11); + if (ret =3D=3D -1) + ksft_exit_fail_msg("(create) writing failed: %s\n", strerror(errno)); + close(fd); +} + +static void modify_file(const char *filename) +{ + int fd; + int ret; + + fd =3D open(filename, O_RDWR); + if (fd =3D=3D -1) + ksft_exit_fail_msg("(modify)open failed :%s\n", strerror(errno)); + if (lseek(fd, 0, SEEK_END) < 0) + ksft_exit_fail_msg("(modify)lseek failed"); + ret =3D write(fd, "modify_file", 11); + if (ret =3D=3D -1) + ksft_exit_fail_msg("(modify)write failed :%s\n", strerror(errno)); + if (fsync(fd) =3D=3D -1) + ksft_exit_fail_msg("(modify)fsync failed: %s\n", strerror(errno)); + + close(fd); +} + +TEST(fanotify_cud_test) +{ + int fan_fd; + char buf[4096]; + int ret; + ssize_t len; + struct fanotify_event_metadata *meta; + + fan_fd =3D fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_FID, O_RDONLY); + ASSERT_GE(fan_fd, 0) + TH_LOG("fanotify_init failed: %s", strerror(errno)); + + ret =3D fanotify_mark(fan_fd, FAN_MARK_ADD, + FAN_EVENT_ON_CHILD | FAN_CREATE | + FAN_MODIFY | FAN_DELETE, + AT_FDCWD, "/tmp"); + ASSERT_GE(ret, 0) + TH_LOG("fanotify_mark failed: %s", strerror(errno)); + + // FAN_CREATE Test + create_file("/tmp/fanotify_test"); + len =3D read(fan_fd, buf, sizeof(buf)); + ASSERT_GT(len, 0) + TH_LOG("No event after create_file"); + + meta =3D (void *)buf; + if (FAN_EVENT_OK(meta, len)) { + TH_LOG("Event after create: mask =3D 0x%llx, pid=3D%d", + (unsigned long long)meta->mask, meta->pid); + if (meta->mask & FAN_CREATE) + ksft_test_result_pass("FAN_CREATE detected\n"); + else + TH_LOG("FAN_CREATE missing"); + } else + ksft_test_result_fail("Invalid event metadata after create\n"); + + // FAN_MODIFY Test + modify_file("/tmp/fanotify_test"); + len =3D read(fan_fd, buf, sizeof(buf)); + ASSERT_GT(len, 0) + TH_LOG("No event after modify_file"); + + meta =3D (void *)buf; + if (FAN_EVENT_OK(meta, len)) { + TH_LOG("Event after modify: mask =3D 0x%llx, pid=3D%d", + (unsigned long long)meta->mask, meta->pid); + if (meta->mask & FAN_MODIFY) + ksft_test_result_pass("FAN_MODIFY detected\n"); + else + ksft_test_result_fail("FAN_MODIFY missing\n"); + } else + ksft_test_result_fail("Invalid event metadata after modify\n"); + + // FAN_DELETE + ASSERT_EQ(unlink("/tmp/fanotify_test"), 0) + TH_LOG("unlink failed: %s", strerror(errno)); + + len =3D read(fan_fd, buf, sizeof(buf)); + ASSERT_GT(len, 0) + TH_LOG("No event after unlink"); + + meta =3D (void *)buf; + if (FAN_EVENT_OK(meta, len)) { + TH_LOG("Event after delete: mask =3D 0x%llx, pid=3D%d", + (unsigned long long)meta->mask, meta->pid); + if (meta->mask & FAN_DELETE) + ksft_test_result_pass("FAN_DELETE detected\n"); + else + ksft_test_result_fail("FAN_DELETE missing\n"); + } else + ksft_test_result_fail("Invalid event metadata after delete\n"); + + // Clean up + if (fan_fd >=3D 0) { + fanotify_mark(fan_fd, FAN_MARK_REMOVE, 0, AT_FDCWD, "."); + close(fan_fd); + } +} + +TEST_HARNESS_MAIN -- 2.43.0