common: compile libcompat as C++
[lttng-tools.git] / tests / unit / test_fd_tracker.cpp
diff --git a/tests/unit/test_fd_tracker.cpp b/tests/unit/test_fd_tracker.cpp
new file mode 100644 (file)
index 0000000..6df179f
--- /dev/null
@@ -0,0 +1,920 @@
+/*
+ * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ */
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdarg.h>
+#include <tap/tap.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <urcu.h>
+
+#include <common/compat/directory-handle.h>
+#include <common/compat/errno.h>
+#include <common/error.h>
+#include <common/fs-handle.h>
+#include <common/fd-tracker/fd-tracker.h>
+
+/* For error.h */
+int lttng_opt_quiet = 1;
+int lttng_opt_verbose;
+int lttng_opt_mi;
+
+/* Number of TAP tests in this file */
+#define NUM_TESTS 61
+/* 3 for stdin, stdout, and stderr */
+#define STDIO_FD_COUNT 3
+#define TRACKER_FD_LIMIT 50
+#define TMP_DIR_PATTERN "/tmp/fd-tracker-XXXXXX"
+#define TEST_UNLINK_DIRECTORY_NAME "unlinked_files"
+
+#ifdef __linux__
+#define SELF_FD_DIR "/proc/self/fd"
+#else
+/* Most Unices have /dev/fd */
+#define SELF_FD_DIR "/dev/fd"
+#endif
+
+/*
+ * Count of fds, beyond stdin, stderr, stdout that were open
+ * at the launch of the test. This allows the test to succeed when
+ * run by automake's test runner or valgrind which both open
+ * fds behind our back.
+ */
+int unknown_fds_count;
+
+const char file_contents[] = "Bacon ipsum dolor amet jerky drumstick sirloin "
+       "strip steak venison boudin filet mignon picanha doner shoulder. "
+       "Strip steak brisket alcatra, venison beef chuck cupim pastrami. "
+       "Landjaeger tri-tip salami leberkas ball tip, ham hock chuck sausage "
+       "flank jerky cupim. Pig bacon chuck pancetta andouille.";
+
+static
+void get_temporary_directories(char **_test_directory, char **_unlink_directory)
+{
+       int ret;
+       char tmp_path_pattern[] = TMP_DIR_PATTERN;
+       char *output_dir;
+
+       output_dir = mkdtemp(tmp_path_pattern);
+       if (!output_dir) {
+               diag("Failed to create temporary path of the form %s",
+                               TMP_DIR_PATTERN);
+               abort();
+       }
+
+       *_test_directory = strdup(output_dir);
+       LTTNG_ASSERT(*_test_directory);
+       ret = asprintf(_unlink_directory, "%s/%s", output_dir,
+                       TEST_UNLINK_DIRECTORY_NAME);
+       if (ret < 0) {
+               abort();
+       }
+}
+
+static
+int fd_count(void)
+{
+       DIR *dir;
+       struct dirent *entry;
+       int count = 0;
+
+       dir = opendir(SELF_FD_DIR);
+       if (!dir) {
+               perror("# Failed to enumerate " SELF_FD_DIR " to count the number of used file descriptors");
+               count = -1;
+               goto end;
+       }
+
+       while ((entry = readdir(dir)) != NULL) {
+               if (!strcmp(entry->d_name, ".") || !strcmp(entry->d_name, "..")) {
+                       continue;
+               }
+               count++;
+       }
+       /* Don't account for the file descriptor opened by opendir(). */
+       count--;
+       if (closedir(dir)) {
+               perror("# Failed to close test program's " SELF_FD_DIR " directory file descriptor");
+       }
+end:
+       return count;
+}
+
+static
+void check_fd_count(int expected_count)
+{
+       int count = 0;
+
+       count = fd_count();
+       ok(count == expected_count, "Expected %d open file descriptors (%d are open)",
+                       expected_count, count);
+}
+
+static
+int noop_open(void *data, int *fds)
+{
+       *fds = *((int *) data);
+       return 0;
+}
+
+static
+int noop_close(void *data, int *fds)
+{
+       return 0;
+}
+
+static
+void track_std_fds(struct fd_tracker *tracker)
+{
+       int i;
+       struct { int fd; const char *name; } files[] = {
+               { .fd = fileno(stdin), .name = "stdin" },
+               { .fd = fileno(stdout), .name = "stdout" },
+               { .fd = fileno(stderr), .name = "stderr" },
+       };
+
+       for (i = 0; i < sizeof(files) / sizeof(*files); i++) {
+               int out_fd, ret;
+
+               ret = fd_tracker_open_unsuspendable_fd(tracker, &out_fd,
+                               &files[i].name, 1, noop_open, &files[i].fd);
+               LTTNG_ASSERT(out_fd == files[i].fd);
+
+               ok(ret == 0, "Track unsuspendable fd %d (%s)", files[i].fd,
+                               files[i].name);
+       }
+}
+
+static
+void untrack_std_fds(struct fd_tracker *tracker)
+{
+       int i;
+       struct { int fd; const char *name; } files[] = {
+               { .fd = fileno(stdin), .name = "stdin" },
+               { .fd = fileno(stdout), .name = "stdout" },
+               { .fd = fileno(stderr), .name = "stderr" },
+       };
+
+       for (i = 0; i < sizeof(files) / sizeof(*files); i++) {
+               int fd = files[i].fd;
+               int ret = fd_tracker_close_unsuspendable_fd(tracker,
+                               &files[i].fd, 1, noop_close, NULL);
+
+               ok(ret == 0, "Untrack unsuspendable fd %d (%s)", fd,
+                               files[i].name);
+       }
+}
+
+/*
+ * Basic test opening and closing three unsuspendable fds. 
+ */
+static
+void test_unsuspendable_basic(void)
+{
+       int ret;
+       struct fd_tracker *tracker;
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       tracker = fd_tracker_create(unlinked_files_directory, TRACKER_FD_LIMIT);
+       ok(tracker, "Created an fd tracker with a limit of %d simulateously opened file descriptors",
+                       TRACKER_FD_LIMIT);
+       if (!tracker) {
+               goto end;
+       }
+
+       track_std_fds(tracker);
+       untrack_std_fds(tracker);
+
+       fd_tracker_destroy(tracker);
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+end:
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+static
+int error_open(void *data, int *fds)
+{
+       return *((int *) data);
+}
+
+static
+int error_close(void *data, int *fds)
+{
+       return *((int *) data);
+}
+
+/*
+ * Validate that user callback return values are returned to the
+ * caller of the fd tracker.
+ */
+static
+void test_unsuspendable_cb_return(void)
+{
+       int ret, stdout_fd = fileno(stdout), out_fd = 42;
+       struct fd_tracker *tracker;
+       int expected_error = -ENETDOWN;
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       tracker = fd_tracker_create(test_directory, TRACKER_FD_LIMIT);
+       LTTNG_ASSERT(tracker);
+
+       /* The error_open callback should fail and return 'expected_error'. */
+       ret = fd_tracker_open_unsuspendable_fd(tracker, &out_fd,
+                       NULL, 1, error_open, &expected_error);
+       ok(ret == expected_error, "fd_tracker_open_unsuspendable_fd() forwards the user callback's error code");
+       ok(out_fd == 42, "Output fd parameter is unaffected on error of fd_tracker_open_unsuspendable_fd()");
+
+       /*
+        * Track a valid fd since we don't want the tracker to fail with an
+        * invalid fd error for this test.
+        */
+       ret = fd_tracker_open_unsuspendable_fd(tracker, &out_fd,
+                       NULL, 1, noop_open, &stdout_fd);
+       ok(out_fd == stdout_fd, "fd_tracker_open_unsuspendable_fd() sets the output fd parameter to the newly-tracked fd's value");
+       LTTNG_ASSERT(!ret);
+
+       ret = fd_tracker_close_unsuspendable_fd(tracker,
+                       &stdout_fd, 1, error_close, &expected_error);
+       ok(ret == expected_error, "fd_tracker_close_unsuspendable_fd() forwards the user callback's error code");
+       ret = fd_tracker_close_unsuspendable_fd(tracker,
+                       &stdout_fd, 1, noop_close, &expected_error);
+       LTTNG_ASSERT(!ret);
+
+       fd_tracker_destroy(tracker);
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+/*
+ * Validate that the tracker refuses to track two identical unsuspendable
+ * file descriptors.
+ */
+static
+void test_unsuspendable_duplicate(void)
+{
+       int ret, stdout_fd = fileno(stdout), out_fd;
+       struct fd_tracker *tracker;
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       tracker = fd_tracker_create(unlinked_files_directory, TRACKER_FD_LIMIT);
+       LTTNG_ASSERT(tracker);
+
+       ret = fd_tracker_open_unsuspendable_fd(tracker, &out_fd,
+                       NULL, 1, noop_open, &stdout_fd);
+       LTTNG_ASSERT(!ret);
+       ret = fd_tracker_open_unsuspendable_fd(tracker, &out_fd,
+                       NULL, 1, noop_open, &stdout_fd);
+       ok(ret == -EEXIST, "EEXIST reported on open of an already tracked file descriptor");
+
+       ret = fd_tracker_close_unsuspendable_fd(tracker,
+                       &stdout_fd, 1, noop_close, NULL);
+       LTTNG_ASSERT(!ret);
+
+       fd_tracker_destroy(tracker);
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+static
+int open_pipes(void *data, int *out_fds)
+{
+       unsigned int i;
+       const unsigned int pipe_count = TRACKER_FD_LIMIT / 2;
+
+       for (i = 0; i < pipe_count; i++) {
+               int ret = pipe(&out_fds[i * 2]);
+
+               if (ret) {
+                       return -errno;
+               }
+       }
+       return 0;
+}
+
+static
+int close_pipes(void *data, int *fds)
+{
+       int i;
+       int *pipes = fds;
+
+       for (i = 0; i < TRACKER_FD_LIMIT; i++) {
+               int ret = close(pipes[i]);
+
+               if (ret) {
+                       return -errno;
+               }
+       }
+       return 0;
+}
+
+/*
+ * Validate that the tracker enforces the open file descriptor limit
+ * when unsuspendable file descriptors are being opened.
+ */
+static
+void test_unsuspendable_limit(void)
+{
+       struct fd_tracker *tracker;
+       int ret, stdout_fd = fileno(stdout), out_fd;
+       int fds[TRACKER_FD_LIMIT];
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       /* This test assumes TRACKER_FD_LIMIT is a multiple of 2. */
+       LTTNG_ASSERT((TRACKER_FD_LIMIT % 2 == 0) && TRACKER_FD_LIMIT);
+
+       tracker = fd_tracker_create(unlinked_files_directory, TRACKER_FD_LIMIT);
+       LTTNG_ASSERT(tracker);
+
+       ret = fd_tracker_open_unsuspendable_fd(tracker, fds,
+                       NULL, TRACKER_FD_LIMIT, open_pipes, NULL);
+       ok(ret == 0, "File descriptor tracker allowed the user to meet its limit with unsuspendable file descriptors (%d)",
+                       TRACKER_FD_LIMIT);
+
+       ret = fd_tracker_open_unsuspendable_fd(tracker, &out_fd,
+                       NULL, 1, noop_open, &stdout_fd);
+       ok(ret == -EMFILE, "EMFILE reported when exceeding the file descriptor limit while opening an unsuspendable fd");
+
+       ret = fd_tracker_close_unsuspendable_fd(tracker,
+                       fds, TRACKER_FD_LIMIT, close_pipes, NULL);
+       LTTNG_ASSERT(!ret);
+
+       fd_tracker_destroy(tracker);
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+/*
+ * Validate that the tracker refuses to track two identical unsuspendable
+ * file descriptors.
+ */
+static
+void test_unsuspendable_close_untracked(void)
+{
+       int ret, stdout_fd = fileno(stdout), unknown_fds[2], out_fd;
+       struct fd_tracker *tracker;
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       tracker = fd_tracker_create(unlinked_files_directory, TRACKER_FD_LIMIT);
+       if (!tracker) {
+               goto end;;
+       }
+
+       ret = pipe(unknown_fds);
+       LTTNG_ASSERT(!ret);
+       ret = close(unknown_fds[0]);
+       LTTNG_ASSERT(ret == 0);
+       ret = close(unknown_fds[1]);
+       LTTNG_ASSERT(ret == 0);
+
+       ret = fd_tracker_open_unsuspendable_fd(tracker, &out_fd,
+                       NULL, 1, noop_open, &stdout_fd);
+       LTTNG_ASSERT(!ret);
+
+       ret = fd_tracker_close_unsuspendable_fd(tracker,
+                       unknown_fds, 1, noop_close, NULL);
+       ok(ret == -EINVAL, "EINVAL reported on close of an untracked file descriptor");
+
+       ret = fd_tracker_close_unsuspendable_fd(tracker,
+                       &stdout_fd, 1, noop_close, NULL);
+       LTTNG_ASSERT(!ret);
+
+       fd_tracker_destroy(tracker);
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+end:
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+static int open_files(struct fd_tracker *tracker,
+               struct lttng_directory_handle *directory,
+               unsigned int count,
+               struct fs_handle **handles,
+               char **file_paths)
+{
+       int ret = 0;
+       unsigned int i;
+
+       for (i = 0; i < count; i++) {
+               int p_ret;
+               char *file_path;
+               struct fs_handle *handle;
+               mode_t mode = S_IWUSR | S_IRUSR;
+
+               p_ret = asprintf(&file_path, "file-%u", i);
+               LTTNG_ASSERT(p_ret >= 0);
+               file_paths[i] = file_path;
+
+               handle = fd_tracker_open_fs_handle(tracker, directory, file_path,
+                               O_RDWR | O_CREAT, &mode);
+               if (!handle) {
+                       ret = -1;
+                       break;
+               }
+               handles[i] = handle;
+       }
+       return ret;
+}
+
+static int open_same_file(struct fd_tracker *tracker,
+               struct lttng_directory_handle *directory,
+               const char *file,
+               unsigned int count,
+               struct fs_handle **handles)
+{
+       int ret = 0;
+       unsigned int i;
+
+       for (i = 0; i < count; i++) {
+               struct fs_handle *handle;
+               mode_t mode = S_IWUSR | S_IRUSR;
+
+               handle = fd_tracker_open_fs_handle(tracker, directory, file,
+                               O_RDWR | O_CREAT, &mode);
+               if (!handle) {
+                       ret = -1;
+                       break;
+               }
+               handles[i] = handle;
+       }
+       return ret;
+}
+
+static
+int cleanup_files(struct fd_tracker *tracker, const char *dir,
+               unsigned int count, struct fs_handle **handles,
+               char **file_paths)
+{
+       int ret = 0;
+       unsigned int i;
+
+       for (i = 0; i < count; i++) {
+               char *file_path = file_paths[i];
+
+               if (!file_path) {
+                       break;
+               }
+               if (fs_handle_unlink(handles[i])) {
+                       diag("Failed to unlink fs_handle to file %s", file_path);
+                       ret = -1;
+               }
+               if (fs_handle_close(handles[i])) {
+                       diag("Failed to close fs_handle to file %s", file_path);
+                       ret = -1;
+               }
+               free(file_path);
+       }
+       return ret;
+}
+
+static
+void test_suspendable_limit(void)
+{
+       int ret;
+       const int files_to_create = TRACKER_FD_LIMIT * 10;
+       struct fd_tracker *tracker;
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+       char *output_files[files_to_create];
+       struct fs_handle *handles[files_to_create];
+       struct lttng_directory_handle *dir_handle = NULL;
+       int dir_handle_fd_count;
+
+       memset(output_files, 0, sizeof(output_files));
+       memset(handles, 0, sizeof(handles));
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       tracker = fd_tracker_create(unlinked_files_directory, TRACKER_FD_LIMIT);
+       if (!tracker) {
+               goto end;
+       }
+
+       dir_handle = lttng_directory_handle_create(test_directory);
+       LTTNG_ASSERT(dir_handle);
+       dir_handle_fd_count = !!lttng_directory_handle_uses_fd(dir_handle);
+
+       ret = open_files(tracker, dir_handle, files_to_create, handles,
+                       output_files);
+       ok(!ret, "Created %d files with a limit of %d simultaneously-opened file descriptor",
+                       files_to_create, TRACKER_FD_LIMIT);
+       check_fd_count(TRACKER_FD_LIMIT + STDIO_FD_COUNT + unknown_fds_count +
+                       dir_handle_fd_count);
+
+       ret = cleanup_files(tracker, test_directory, files_to_create, handles,
+                       output_files);
+       ok(!ret, "Close all opened filesystem handles");
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+       fd_tracker_destroy(tracker);
+       lttng_directory_handle_put(dir_handle);
+end:
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+static
+void test_mixed_limit(void)
+{
+       int ret;
+       const int files_to_create = TRACKER_FD_LIMIT;
+       struct fd_tracker *tracker;
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+       char *output_files[files_to_create];
+       struct fs_handle *handles[files_to_create];
+       struct lttng_directory_handle *dir_handle = NULL;
+       int dir_handle_fd_count;
+
+       memset(output_files, 0, sizeof(output_files));
+       memset(handles, 0, sizeof(handles));
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       tracker = fd_tracker_create(unlinked_files_directory, TRACKER_FD_LIMIT);
+       if (!tracker) {
+               goto end;
+       }
+
+       dir_handle = lttng_directory_handle_create(test_directory);
+       LTTNG_ASSERT(dir_handle);
+       dir_handle_fd_count = !!lttng_directory_handle_uses_fd(dir_handle);
+
+       ret = open_files(tracker, dir_handle, files_to_create, handles,
+                       output_files);
+       ok(!ret, "Created %d files with a limit of %d simultaneously-opened file descriptor",
+                       files_to_create, TRACKER_FD_LIMIT);
+       diag("Check file descriptor count after opening %u files", files_to_create);
+       check_fd_count(TRACKER_FD_LIMIT + STDIO_FD_COUNT + unknown_fds_count +
+                       dir_handle_fd_count);
+
+       /*
+        * Open unsuspendable fds (stdin, stdout, stderr) and verify that the fd
+        * cap is still respected.
+        */
+       diag("Check file descriptor count after adding %d unsuspendable fds",
+                       STDIO_FD_COUNT);
+       track_std_fds(tracker);
+       check_fd_count(TRACKER_FD_LIMIT + unknown_fds_count +
+                       dir_handle_fd_count);
+       diag("Untrack unsuspendable file descriptors");
+       untrack_std_fds(tracker);
+       check_fd_count(TRACKER_FD_LIMIT + unknown_fds_count +
+                       dir_handle_fd_count);
+
+       ret = cleanup_files(tracker, test_directory, files_to_create, handles,
+                       output_files);
+       ok(!ret, "Close all opened filesystem handles");
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+       fd_tracker_destroy(tracker);
+       lttng_directory_handle_put(dir_handle);
+end:
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+/*
+ * Open more files than allowed by the fd tracker's cap and write,
+ * byte-by-byte, and in round-robin, a string. The goal is to force
+ * the fd tracker to suspend and resume the fs_handles often and
+ * verify that the fd cap is always respected.
+ *
+ * The content of the files is also verified at the end.
+ */
+static
+void test_suspendable_restore(void)
+{
+       int ret;
+       const int files_to_create = TRACKER_FD_LIMIT * 10;
+       struct fd_tracker *tracker;
+       char *output_files[files_to_create];
+       struct fs_handle *handles[files_to_create];
+       size_t content_index;
+       int handle_index;
+       bool write_success = true;
+       bool fd_cap_respected = true;
+       bool content_ok = true;
+       struct lttng_directory_handle *dir_handle = NULL;
+       int dir_handle_fd_count;
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+
+       memset(output_files, 0, sizeof(output_files));
+       memset(handles, 0, sizeof(handles));
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+
+       tracker = fd_tracker_create(unlinked_files_directory, TRACKER_FD_LIMIT);
+       if (!tracker) {
+               goto end;
+       }
+
+       dir_handle = lttng_directory_handle_create(test_directory);
+       LTTNG_ASSERT(dir_handle);
+       dir_handle_fd_count = !!lttng_directory_handle_uses_fd(dir_handle);
+
+       ret = open_files(tracker, dir_handle, files_to_create, handles,
+                       output_files);
+       ok(!ret, "Created %d files with a limit of %d simultaneously-opened file descriptor",
+                       files_to_create, TRACKER_FD_LIMIT);
+       diag("Check file descriptor count after opening %u files", files_to_create);
+       check_fd_count(TRACKER_FD_LIMIT + STDIO_FD_COUNT + unknown_fds_count +
+                       dir_handle_fd_count);
+
+       for (content_index = 0; content_index < sizeof(file_contents); content_index++) {
+               for (handle_index = 0; handle_index < files_to_create; handle_index++) {
+                       int fd;
+                       struct fs_handle *handle = handles[handle_index];
+                       const char *path = output_files[handle_index];
+
+                       fd = fs_handle_get_fd(handle);
+                       if (fd < 0) {
+                               write_success = false;
+                               diag("Failed to restore fs_handle to %s",
+                                               path);
+                               goto skip_write;
+                       }
+
+                       do {
+                               ret = write(fd, file_contents + content_index, 1);
+                       } while (ret < 0 && errno == EINTR);
+
+                       if (ret != 1) {
+                               write_success = false;
+                               PERROR("write() to %s failed", path);
+                               goto skip_write;
+                       }
+
+                       if (fd_count() > (TRACKER_FD_LIMIT + STDIO_FD_COUNT +
+                                                       unknown_fds_count +
+                                                       dir_handle_fd_count)) {
+                               fd_cap_respected = false;
+                       }
+
+                       fs_handle_put_fd(handle);
+               }
+       }
+skip_write:
+       ok(write_success, "Wrote reference string to %d files",
+                       files_to_create);
+       ok(fd_cap_respected, "FD tracker enforced the file descriptor cap");
+
+       /* Validate the contents of the files. */
+       for (handle_index = 0; handle_index < files_to_create; handle_index++) {
+               struct stat fd_stat;
+               const char *path = output_files[handle_index];
+               char read_buf[sizeof(file_contents)];
+               char *read_pos;
+               size_t to_read = sizeof(read_buf);
+               int fd;
+
+               fd = lttng_directory_handle_open_file(
+                               dir_handle, path, O_RDONLY, 0);
+               LTTNG_ASSERT(fd >= 0);
+               ret = fstat(fd, &fd_stat);
+               LTTNG_ASSERT(!ret);
+               if (fd_stat.st_size != sizeof(file_contents)) {
+                       diag("Content size of file %s doesn't match, got %" PRId64 ", expected %zu",
+                                       path, (int64_t) fd_stat.st_size,
+                                       sizeof(file_contents));
+                       content_ok = false;
+                       (void) close(fd);
+                       break;
+               }
+
+               read_pos = read_buf;
+               do {
+                       ret = read(fd, read_pos, to_read);
+                       if (ret > 0) {
+                               to_read -= ret;
+                               read_pos += ret;
+                       }
+               } while (to_read && (ret < 0 && errno == EINTR));
+               if (ret < 0) {
+                       content_ok = false;
+                       PERROR("Failed to read file %s", path);
+                       (void) close(fd);
+                       break;
+               }
+
+               if (strcmp(file_contents, read_buf)) {
+                       content_ok = false;
+                       diag("File content doesn't match the expectated string");
+                       (void) close(fd);
+                       break;
+               }
+               (void) close(fd);
+       }
+       ok(content_ok, "Files contain the expected content");
+       ret = cleanup_files(tracker, test_directory, files_to_create, handles,
+                       output_files);
+       ok(!ret, "Close all opened filesystem handles");
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+       fd_tracker_destroy(tracker);
+       lttng_directory_handle_put(dir_handle);
+end:
+       free(test_directory);
+       free(unlinked_files_directory);
+}
+
+static
+void test_unlink(void)
+{
+       int ret;
+       struct fd_tracker *tracker;
+       const int handles_to_open = 2;
+       struct fs_handle *handles[handles_to_open];
+       struct fs_handle *new_handle = NULL;
+       struct stat statbuf;
+       struct lttng_directory_handle *dir_handle = NULL;
+       const char file_name[] = "my_file";
+       char *test_directory = NULL, *unlinked_files_directory = NULL;
+       char *unlinked_file_zero = NULL, *unlinked_file_one = NULL;
+       int fd;
+
+       get_temporary_directories(&test_directory, &unlinked_files_directory);
+       ret = asprintf(&unlinked_file_zero, "%s/%u", unlinked_files_directory,
+                       0);
+       LTTNG_ASSERT(ret > 0);
+       ret = asprintf(&unlinked_file_one, "%s/%u", unlinked_files_directory,
+                       1);
+       LTTNG_ASSERT(ret > 0);
+
+       tracker = fd_tracker_create(unlinked_files_directory, 1);
+       if (!tracker) {
+               goto end;
+       }
+
+       dir_handle = lttng_directory_handle_create(test_directory);
+       LTTNG_ASSERT(dir_handle);
+
+       /* Open two handles to the same file. */
+       ret = open_same_file(tracker, dir_handle, file_name, handles_to_open,
+                       handles);
+       ok(!ret, "Successfully opened %i handles to %s/%s", handles_to_open,
+                       test_directory, file_name);
+       if (ret) {
+               goto end;
+       }
+
+       /*
+        * Unlinking the first handle should cause the file to be renamed
+        * to '0'.
+        */
+       ret = fs_handle_unlink(handles[0]);
+       ok(!ret, "Successfully unlinked the first handle to %s/%s",
+                       test_directory, file_name);
+
+       /*
+        * The original file should no longer exist on the file system, and a
+        * new file named '0' should exist.
+        */
+       ok(lttng_directory_handle_stat(dir_handle, file_name, &statbuf) == -1 &&
+                                       errno == ENOENT,
+                       "%s no longer present on file system after unlink",
+                       file_name);
+       ok(lttng_directory_handle_stat(
+                       dir_handle, unlinked_file_zero, &statbuf) == 0,
+                       "%s exists on file system after unlink",
+                       unlinked_file_zero);
+
+       /*
+        * It should be possible to use the file descriptors of both handles.
+        * Since only one file descriptor can be opened at once, this should
+        * force the fd_tracker to suspend and restore the handles.
+        */
+       fd = fs_handle_get_fd(handles[0]);
+       ok(fd >= 0, "Got fd from first handle");
+
+       fd = fs_handle_get_fd(handles[1]);
+       ok (fd < 0, "fd tracker does not allow two fds to be used at once");
+
+       fs_handle_put_fd(handles[0]);
+       fd = fs_handle_get_fd(handles[1]);
+       ok(fd >= 0, "Got fd from second handle");
+       fs_handle_put_fd(handles[1]);
+
+       /* The second unlink should fail with -ENOENT. */
+       ret = fs_handle_unlink(handles[1]);
+       ok(ret == -ENOENT,
+                       "ENOENT is reported when attempting to unlink the second handle to %s/%s",
+                       test_directory, file_name);
+
+       /*
+        * Opening a new handle to 'my_file' should succeed.
+        */
+       ret = open_same_file(tracker, dir_handle, file_name, 1, &new_handle);
+       ok(!ret, "Successfully opened a new handle to previously unlinked file %s/%s",
+                       test_directory, file_name);
+       LTTNG_ASSERT(new_handle);
+
+       /*
+        * Unlinking the new handle should cause the file to be renamed
+        * to '1' since '0' already exists.
+        */
+       ret = fs_handle_unlink(new_handle);
+       ok(!ret, "Successfully unlinked the new handle handle to %s/%s",
+                       test_directory, file_name);
+       ok(stat(unlinked_file_one, &statbuf) == 0,
+                       "%s exists on file system after unlink",
+                       unlinked_file_one);
+
+       ret = fs_handle_close(handles[0]);
+       ok(!ret, "Successfully closed the first handle");
+       ret = fs_handle_close(handles[1]);
+       ok(!ret, "Successfully closed the second handle");
+       ret = fs_handle_close(new_handle);
+       ok(!ret, "Successfully closed the third handle");
+
+       ok(lttng_directory_handle_stat(dir_handle, file_name, &statbuf) == -1 &&
+                                       errno == ENOENT,
+                       "%s no longer present on file system after handle close",
+                       file_name);
+       ok(lttng_directory_handle_stat(
+                       dir_handle, unlinked_file_zero, &statbuf) == -1 &&
+                                       errno == ENOENT,
+                       "%s no longer present on file system after handle close",
+                       unlinked_file_zero);
+       ok(lttng_directory_handle_stat(dir_handle, unlinked_file_one,
+                       &statbuf) == -1 &&
+                                       errno == ENOENT,
+                       "%s no longer present on file system after handle close",
+                       unlinked_file_one);
+
+       ret = rmdir(test_directory);
+       ok(ret == 0, "Test directory is empty");
+end:
+       fd_tracker_destroy(tracker);
+       free(test_directory);
+       free(unlinked_files_directory);
+       free(unlinked_file_zero);
+       free(unlinked_file_one);
+       lttng_directory_handle_put(dir_handle);
+}
+
+int main(int argc, char **argv)
+{
+       plan_tests(NUM_TESTS);
+       diag("File descriptor tracker unit tests");
+
+       rcu_register_thread();
+
+       unknown_fds_count = fd_count() - STDIO_FD_COUNT;
+       LTTNG_ASSERT(unknown_fds_count >= 0);
+
+       diag("Unsuspendable - basic");
+       test_unsuspendable_basic();
+       diag("Unsuspendable - callback return values");
+       test_unsuspendable_cb_return();
+       diag("Unsuspendable - duplicate file descriptors");
+       test_unsuspendable_duplicate();
+       diag("Unsuspendable - closing an untracked file descriptor");
+       test_unsuspendable_close_untracked();
+       diag("Unsuspendable - check that file descriptor limit is enforced");
+       test_unsuspendable_limit();
+
+       diag("Suspendable - check that file descriptor limit is enforced");
+       test_suspendable_limit();
+       diag("Suspendable - restoration test");
+       test_suspendable_restore();
+
+       diag("Mixed - check that file descriptor limit is enforced");
+       test_mixed_limit();
+
+       diag("Suspendable - Unlinking test");
+       test_unlink();
+
+       rcu_barrier();
+       rcu_unregister_thread();
+       return exit_status();
+}
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