util: add helper APIs for dealing with inotify in portable manner

The inotify userspace API for reading events is quite horrible, so it is
useful to wrap it in a more friendly API to avoid duplicating code
across many users in QEMU. Wrapping it also allows introduction of a
platform portability layer, so that we can add impls for non-Linux based
equivalents in future.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

1 files changed, 685 insertions, 0 deletions

diff --git a/tests/test-util-filemonitor.c b/tests/test-util-filemonitor.c
new file mode 100644
index 0000000000..5d95cea5ee
--- /dev/null
+++ b/tests/test-util-filemonitor.c
@@ -0,0 +1,685 @@
+/*
+ * Tests for util/filemonitor-*.c
+ *
+ * Copyright 2018 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/main-loop.h"
+#include "qapi/error.h"
+#include "qemu/filemonitor.h"
+
+#include <utime.h>
+
+enum {
+    QFILE_MONITOR_TEST_OP_CREATE,
+    QFILE_MONITOR_TEST_OP_APPEND,
+    QFILE_MONITOR_TEST_OP_TRUNC,
+    QFILE_MONITOR_TEST_OP_RENAME,
+    QFILE_MONITOR_TEST_OP_TOUCH,
+    QFILE_MONITOR_TEST_OP_UNLINK,
+};
+
+typedef struct {
+    int type;
+    const char *filesrc;
+    const char *filedst;
+} QFileMonitorTestOp;
+
+typedef struct {
+    const char *file;
+} QFileMonitorTestWatch;
+
+typedef struct {
+    gsize nwatches;
+    const QFileMonitorTestWatch *watches;
+
+    gsize nops;
+    const QFileMonitorTestOp *ops;
+} QFileMonitorTestPlan;
+
+typedef struct {
+    int id;
+    QFileMonitorEvent event;
+    char *filename;
+} QFileMonitorTestRecord;
+
+
+typedef struct {
+    QemuMutex lock;
+    GList *records;
+} QFileMonitorTestData;
+
+static QemuMutex evlock;
+static bool evstopping;
+static bool evrunning;
+
+/*
+ * Main function for a background thread that is
+ * running the event loop during the test
+ */
+static void *
+qemu_file_monitor_test_event_loop(void *opaque G_GNUC_UNUSED)
+{
+    qemu_mutex_lock(&evlock);
+
+    while (!evstopping) {
+        qemu_mutex_unlock(&evlock);
+        main_loop_wait(true);
+        qemu_mutex_lock(&evlock);
+    }
+
+    evrunning = false;
+    qemu_mutex_unlock(&evlock);
+    return NULL;
+}
+
+
+/*
+ * File monitor event handler which simply maintains
+ * an ordered list of all events that it receives
+ */
+static void
+qemu_file_monitor_test_handler(int id,
+                               QFileMonitorEvent event,
+                               const char *filename,
+                               void *opaque)
+{
+    QFileMonitorTestData *data = opaque;
+    QFileMonitorTestRecord *rec = g_new0(QFileMonitorTestRecord, 1);
+
+    rec->id = id;
+    rec->event = event;
+    rec->filename = g_strdup(filename);
+
+    qemu_mutex_lock(&data->lock);
+    data->records = g_list_append(data->records, rec);
+    qemu_mutex_unlock(&data->lock);
+}
+
+
+static void
+qemu_file_monitor_test_record_free(QFileMonitorTestRecord *rec)
+{
+    g_free(rec->filename);
+    g_free(rec);
+}
+
+
+/*
+ * Get the next event record that has been received by
+ * the file monitor event handler. Since events are
+ * emitted in the background thread running the event
+ * loop, we can't assume there is a record available
+ * immediately. Thus we will sleep for upto 5 seconds
+ * to wait for the event to be queued for us.
+ */
+static QFileMonitorTestRecord *
+qemu_file_monitor_test_next_record(QFileMonitorTestData *data)
+{
+    GTimer *timer = g_timer_new();
+    QFileMonitorTestRecord *record = NULL;
+    GList *tmp;
+
+    qemu_mutex_lock(&data->lock);
+    while (!data->records && g_timer_elapsed(timer, NULL) < 5) {
+        qemu_mutex_unlock(&data->lock);
+        usleep(10 * 1000);
+        qemu_mutex_lock(&data->lock);
+    }
+    if (data->records) {
+        record = data->records->data;
+        tmp = data->records;
+        data->records = g_list_remove_link(data->records, tmp);
+        g_list_free(tmp);
+    }
+    qemu_mutex_unlock(&data->lock);
+
+    g_timer_destroy(timer);
+    return record;
+}
+
+
+/*
+ * Check whether the event record we retrieved matches
+ * data we were expecting to see for the event
+ */
+static bool
+qemu_file_monitor_test_expect(QFileMonitorTestData *data,
+                              int id,
+                              QFileMonitorEvent event,
+                              const char *filename)
+{
+    QFileMonitorTestRecord *rec;
+    bool ret = false;
+
+    rec = qemu_file_monitor_test_next_record(data);
+
+    if (!rec) {
+        g_printerr("Missing event watch id %d event %d file %s\n",
+                   id, event, filename);
+        return false;
+    }
+
+    if (id != rec->id) {
+        g_printerr("Expected watch id %d but got %d\n", id, rec->id);
+        goto cleanup;
+    }
+
+    if (event != rec->event) {
+        g_printerr("Expected event %d but got %d\n", event, rec->event);
+        goto cleanup;
+    }
+
+    if (!g_str_equal(filename, rec->filename)) {
+        g_printerr("Expected filename %s but got %s\n",
+                   filename, rec->filename);
+        goto cleanup;
+    }
+
+    ret = true;
+
+ cleanup:
+    qemu_file_monitor_test_record_free(rec);
+    return ret;
+}
+
+
+static void
+test_file_monitor_events(const void *opaque)
+{
+    const QFileMonitorTestPlan *plan = opaque;
+    Error *local_err = NULL;
+    GError *gerr = NULL;
+    QFileMonitor *mon = qemu_file_monitor_new(&local_err);
+    QemuThread th;
+    GTimer *timer;
+    gchar *dir = NULL;
+    int err = -1;
+    gsize i, j;
+    char *pathsrc = NULL;
+    char *pathdst = NULL;
+    QFileMonitorTestData data;
+
+    qemu_mutex_init(&data.lock);
+    data.records = NULL;
+
+    /*
+     * The file monitor needs the main loop running in
+     * order to receive events from inotify. We must
+     * thus spawn a background thread to run an event
+     * loop impl, while this thread triggers the
+     * actual file operations we're testing
+     */
+    evrunning = 1;
+    evstopping = 0;
+    qemu_thread_create(&th, "event-loop",
+                       qemu_file_monitor_test_event_loop, NULL,
+                       QEMU_THREAD_JOINABLE);
+
+    if (local_err) {
+        g_printerr("File monitoring not available: %s",
+                   error_get_pretty(local_err));
+        error_free(local_err);
+        return;
+    }
+
+    dir = g_dir_make_tmp("test-util-filemonitor-XXXXXX",
+                         &gerr);
+    if (!dir) {
+        g_printerr("Unable to create tmp dir %s",
+                   gerr->message);
+        g_error_free(gerr);
+        abort();
+    }
+
+    /*
+     * First register all the directory / file watches
+     * we're interested in seeing events against
+     */
+    for (i = 0; i < plan->nwatches; i++) {
+        int watchid;
+        watchid = qemu_file_monitor_add_watch(mon,
+                                              dir,
+                                              plan->watches[i].file,
+                                              qemu_file_monitor_test_handler,
+                                              &data,
+                                              &local_err);
+        if (watchid < 0) {
+            g_printerr("Unable to add watch %s",
+                       error_get_pretty(local_err));
+            goto cleanup;
+        }
+    }
+
+
+    /*
+     * Now invoke all the file operations (create,
+     * delete, rename, chmod, etc). These operations
+     * will trigger the various file monitor events
+     */
+    for (i = 0; i < plan->nops; i++) {
+        const QFileMonitorTestOp *op = &(plan->ops[i]);
+        int fd;
+        struct utimbuf ubuf;
+
+        pathsrc = g_strdup_printf("%s/%s", dir, op->filesrc);
+        if (op->filedst) {
+            pathdst = g_strdup_printf("%s/%s", dir, op->filedst);
+        }
+
+        switch (op->type) {
+        case QFILE_MONITOR_TEST_OP_CREATE:
+            fd = open(pathsrc, O_WRONLY | O_CREAT, 0700);
+            if (fd < 0) {
+                g_printerr("Unable to create %s: %s",
+                           pathsrc, strerror(errno));
+                goto cleanup;
+            }
+            close(fd);
+            break;
+
+        case QFILE_MONITOR_TEST_OP_APPEND:
+            fd = open(pathsrc, O_WRONLY | O_APPEND, 0700);
+            if (fd < 0) {
+                g_printerr("Unable to open %s: %s",
+                           pathsrc, strerror(errno));
+                goto cleanup;
+            }
+
+            if (write(fd, "Hello World", 10) != 10) {
+                g_printerr("Unable to write %s: %s",
+                           pathsrc, strerror(errno));
+                close(fd);
+                goto cleanup;
+            }
+            close(fd);
+            break;
+
+        case QFILE_MONITOR_TEST_OP_TRUNC:
+            if (truncate(pathsrc, 4) < 0) {
+                g_printerr("Unable to truncate %s: %s",
+                           pathsrc, strerror(errno));
+                goto cleanup;
+            }
+            break;
+
+        case QFILE_MONITOR_TEST_OP_RENAME:
+            if (rename(pathsrc, pathdst) < 0) {
+                g_printerr("Unable to rename %s to %s: %s",
+                           pathsrc, pathdst, strerror(errno));
+                goto cleanup;
+            }
+            break;
+
+        case QFILE_MONITOR_TEST_OP_UNLINK:
+            if (unlink(pathsrc) < 0) {
+                g_printerr("Unable to unlink %s: %s",
+                           pathsrc, strerror(errno));
+                goto cleanup;
+            }
+            break;
+
+        case QFILE_MONITOR_TEST_OP_TOUCH:
+            ubuf.actime = 1024;
+            ubuf.modtime = 1025;
+            if (utime(pathsrc, &ubuf) < 0) {
+                g_printerr("Unable to touch %s: %s",
+                           pathsrc, strerror(errno));
+                goto cleanup;
+            }
+            break;
+
+        default:
+            g_assert_not_reached();
+        }
+
+        g_free(pathsrc);
+        g_free(pathdst);
+        pathsrc = pathdst = NULL;
+    }
+
+
+    /*
+     * Finally validate that we have received all the events
+     * we expect to see for the combination of watches and
+     * file operations
+     */
+    for (i = 0; i < plan->nops; i++) {
+        const QFileMonitorTestOp *op = &(plan->ops[i]);
+
+        switch (op->type) {
+        case QFILE_MONITOR_TEST_OP_CREATE:
+            for (j = 0; j < plan->nwatches; j++) {
+                if (plan->watches[j].file &&
+                    !g_str_equal(plan->watches[j].file, op->filesrc))
+                    continue;
+
+                if (!qemu_file_monitor_test_expect(
+                        &data, j, QFILE_MONITOR_EVENT_CREATED, op->filesrc))
+                    goto cleanup;
+            }
+            break;
+
+        case QFILE_MONITOR_TEST_OP_APPEND:
+        case QFILE_MONITOR_TEST_OP_TRUNC:
+            for (j = 0; j < plan->nwatches; j++) {
+                if (plan->watches[j].file &&
+                    !g_str_equal(plan->watches[j].file, op->filesrc))
+                    continue;
+
+                if (!qemu_file_monitor_test_expect(
+                        &data, j, QFILE_MONITOR_EVENT_MODIFIED, op->filesrc))
+                    goto cleanup;
+            }
+            break;
+
+        case QFILE_MONITOR_TEST_OP_RENAME:
+            for (j = 0; j < plan->nwatches; j++) {
+                if (plan->watches[j].file &&
+                    !g_str_equal(plan->watches[j].file, op->filesrc))
+                    continue;
+
+                if (!qemu_file_monitor_test_expect(
+                        &data, j, QFILE_MONITOR_EVENT_DELETED, op->filesrc))
+                    goto cleanup;
+            }
+
+            for (j = 0; j < plan->nwatches; j++) {
+                if (plan->watches[j].file &&
+                    !g_str_equal(plan->watches[j].file, op->filedst))
+                    continue;
+
+                if (!qemu_file_monitor_test_expect(
+                        &data, j, QFILE_MONITOR_EVENT_CREATED, op->filedst))
+                    goto cleanup;
+            }
+            break;
+
+        case QFILE_MONITOR_TEST_OP_TOUCH:
+            for (j = 0; j < plan->nwatches; j++) {
+                if (plan->watches[j].file &&
+                    !g_str_equal(plan->watches[j].file, op->filesrc))
+                    continue;
+
+                if (!qemu_file_monitor_test_expect(
+                        &data, j, QFILE_MONITOR_EVENT_ATTRIBUTES, op->filesrc))
+                    goto cleanup;
+            }
+            break;
+
+        case QFILE_MONITOR_TEST_OP_UNLINK:
+            for (j = 0; j < plan->nwatches; j++) {
+                if (plan->watches[j].file &&
+                    !g_str_equal(plan->watches[j].file, op->filesrc))
+                    continue;
+
+                if (!qemu_file_monitor_test_expect(
+                        &data, j, QFILE_MONITOR_EVENT_DELETED, op->filesrc))
+                    goto cleanup;
+            }
+            break;
+
+        default:
+            g_assert_not_reached();
+        }
+    }
+
+    err = 0;
+
+ cleanup:
+    g_free(pathsrc);
+    g_free(pathdst);
+
+    qemu_mutex_lock(&evlock);
+    evstopping = 1;
+    timer = g_timer_new();
+    while (evrunning && g_timer_elapsed(timer, NULL) < 5) {
+        qemu_mutex_unlock(&evlock);
+        usleep(10 * 1000);
+        qemu_mutex_lock(&evlock);
+    }
+    qemu_mutex_unlock(&evlock);
+
+    if (g_timer_elapsed(timer, NULL) >= 5) {
+        g_printerr("Event loop failed to quit after 5 seconds\n");
+    }
+    g_timer_destroy(timer);
+
+    for (i = 0; i < plan->nops; i++) {
+        const QFileMonitorTestOp *op = &(plan->ops[i]);
+        pathsrc = g_strdup_printf("%s/%s", dir, op->filesrc);
+        unlink(pathsrc);
+        g_free(pathsrc);
+        if (op->filedst) {
+            pathdst = g_strdup_printf("%s/%s", dir, op->filedst);
+            unlink(pathdst);
+            g_free(pathdst);
+        }
+    }
+
+    qemu_file_monitor_free(mon);
+    g_list_foreach(data.records,
+                   (GFunc)qemu_file_monitor_test_record_free, NULL);
+    g_list_free(data.records);
+    qemu_mutex_destroy(&data.lock);
+    if (dir) {
+        rmdir(dir);
+    }
+    g_free(dir);
+    g_assert(err == 0);
+}
+
+
+/*
+ * Set of structs which define which file name patterns
+ * we're trying to watch against. NULL, means all files
+ * in the directory
+ */
+static const QFileMonitorTestWatch watches_any[] = {
+    { NULL },
+};
+
+static const QFileMonitorTestWatch watches_one[] = {
+    { "one.txt" },
+};
+
+static const QFileMonitorTestWatch watches_two[] = {
+    { "two.txt" },
+};
+
+static const QFileMonitorTestWatch watches_many[] = {
+    { NULL },
+    { "one.txt" },
+    { "two.txt" },
+};
+
+
+/*
+ * Various sets of file operations we're going to
+ * trigger and validate events for
+ */
+static const QFileMonitorTestOp ops_create_one[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", }
+};
+
+static const QFileMonitorTestOp ops_delete_one[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_UNLINK,
+      .filesrc = "one.txt", }
+};
+
+static const QFileMonitorTestOp ops_create_many[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "two.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "three.txt", }
+};
+
+static const QFileMonitorTestOp ops_rename_one[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_RENAME,
+      .filesrc = "one.txt", .filedst = "two.txt" }
+};
+
+static const QFileMonitorTestOp ops_rename_many[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "two.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_RENAME,
+      .filesrc = "one.txt", .filedst = "two.txt" }
+};
+
+static const QFileMonitorTestOp ops_append_one[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_APPEND,
+      .filesrc = "one.txt", },
+};
+
+static const QFileMonitorTestOp ops_trunc_one[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_TRUNC,
+      .filesrc = "one.txt", },
+};
+
+static const QFileMonitorTestOp ops_touch_one[] = {
+    { .type = QFILE_MONITOR_TEST_OP_CREATE,
+      .filesrc = "one.txt", },
+    { .type = QFILE_MONITOR_TEST_OP_TOUCH,
+      .filesrc = "one.txt", },
+};
+
+
+/*
+ * No we define data sets for the combinatorial
+ * expansion of file watches and operation sets
+ */
+#define PLAN_DATA(o, w) \
+    static const QFileMonitorTestPlan plan_ ## o ## _ ## w = { \
+        .nops = G_N_ELEMENTS(ops_ ##o), \
+        .ops = ops_ ##o, \
+        .nwatches = G_N_ELEMENTS(watches_ ##w), \
+        .watches = watches_ ## w, \
+    }
+
+PLAN_DATA(create_one, any);
+PLAN_DATA(create_one, one);
+PLAN_DATA(create_one, two);
+PLAN_DATA(create_one, many);
+
+PLAN_DATA(delete_one, any);
+PLAN_DATA(delete_one, one);
+PLAN_DATA(delete_one, two);
+PLAN_DATA(delete_one, many);
+
+PLAN_DATA(create_many, any);
+PLAN_DATA(create_many, one);
+PLAN_DATA(create_many, two);
+PLAN_DATA(create_many, many);
+
+PLAN_DATA(rename_one, any);
+PLAN_DATA(rename_one, one);
+PLAN_DATA(rename_one, two);
+PLAN_DATA(rename_one, many);
+
+PLAN_DATA(rename_many, any);
+PLAN_DATA(rename_many, one);
+PLAN_DATA(rename_many, two);
+PLAN_DATA(rename_many, many);
+
+PLAN_DATA(append_one, any);
+PLAN_DATA(append_one, one);
+PLAN_DATA(append_one, two);
+PLAN_DATA(append_one, many);
+
+PLAN_DATA(trunc_one, any);
+PLAN_DATA(trunc_one, one);
+PLAN_DATA(trunc_one, two);
+PLAN_DATA(trunc_one, many);
+
+PLAN_DATA(touch_one, any);
+PLAN_DATA(touch_one, one);
+PLAN_DATA(touch_one, two);
+PLAN_DATA(touch_one, many);
+
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+
+    qemu_init_main_loop(&error_abort);
+
+    qemu_mutex_init(&evlock);
+
+    /*
+     * Register test cases for the combinatorial
+     * expansion of file watches and operation sets
+     */
+    #define PLAN_REGISTER(o, w)                                         \
+        g_test_add_data_func("/util/filemonitor/" # o "/" # w,          \
+                             &plan_ ## o ## _ ## w, test_file_monitor_events)
+
+    PLAN_REGISTER(create_one, any);
+    PLAN_REGISTER(create_one, one);
+    PLAN_REGISTER(create_one, two);
+    PLAN_REGISTER(create_one, many);
+
+    PLAN_REGISTER(delete_one, any);
+    PLAN_REGISTER(delete_one, one);
+    PLAN_REGISTER(delete_one, two);
+    PLAN_REGISTER(delete_one, many);
+
+    PLAN_REGISTER(create_many, any);
+    PLAN_REGISTER(create_many, one);
+    PLAN_REGISTER(create_many, two);
+    PLAN_REGISTER(create_many, many);
+
+    PLAN_REGISTER(rename_one, any);
+    PLAN_REGISTER(rename_one, one);
+    PLAN_REGISTER(rename_one, two);
+    PLAN_REGISTER(rename_one, many);
+
+    PLAN_REGISTER(rename_many, any);
+    PLAN_REGISTER(rename_many, one);
+    PLAN_REGISTER(rename_many, two);
+    PLAN_REGISTER(rename_many, many);
+
+    PLAN_REGISTER(append_one, any);
+    PLAN_REGISTER(append_one, one);
+    PLAN_REGISTER(append_one, two);
+    PLAN_REGISTER(append_one, many);
+
+    PLAN_REGISTER(trunc_one, any);
+    PLAN_REGISTER(trunc_one, one);
+    PLAN_REGISTER(trunc_one, two);
+    PLAN_REGISTER(trunc_one, many);
+
+    PLAN_REGISTER(touch_one, any);
+    PLAN_REGISTER(touch_one, one);
+    PLAN_REGISTER(touch_one, two);
+    PLAN_REGISTER(touch_one, many);
+
+    return g_test_run();
+}