diff options
| -rw-r--r-- | libmount/src/monitor.c | 148 |
1 files changed, 75 insertions, 73 deletions
diff --git a/libmount/src/monitor.c b/libmount/src/monitor.c index 15e34f013..cf91f32c3 100644 --- a/libmount/src/monitor.c +++ b/libmount/src/monitor.c @@ -46,7 +46,7 @@ struct libmnt_monitor { struct monitor_opers { int (*op_get_fd)(struct libmnt_monitor *, struct monitor_entry *); int (*op_close_fd)(struct libmnt_monitor *, struct monitor_entry *); - int (*op_verify_change)(struct libmnt_monitor *, struct monitor_entry *); + void (*op_event_cleanup)(struct libmnt_monitor *, struct monitor_entry *); }; static int monitor_modify_epoll(struct libmnt_monitor *mn, @@ -199,8 +199,9 @@ static int userspace_monitor_close_fd(struct libmnt_monitor *mn, static int userspace_monitor_get_fd(struct libmnt_monitor *mn, struct monitor_entry *me) { - int wd, rc; + int wd, rc, dummy_fd; char *dirname, *sep; + char *filename = NULL; assert(mn); assert(me); @@ -220,72 +221,65 @@ static int userspace_monitor_get_fd(struct libmnt_monitor *mn, rc = mkdir(dirname, S_IWUSR| S_IRUSR|S_IRGRP|S_IROTH| S_IXUSR|S_IXGRP|S_IXOTH); + + if (sep && sep > dirname) + *(sep - 1) = '/'; /* set '/' back to the path */ + if (rc && errno != EEXIST) goto err; + /* + * libmount uses rename(2) to atomically update utab/mtab, monitor + * rename changes is too tricky. It seems better to monitor utab + * lockfile close. + */ + if (asprintf(&filename, "%s.lock", me->path) <= 0) + goto err; + + /* make sure the file exists */ + dummy_fd = open(filename, O_RDONLY|O_CREAT|O_CLOEXEC, + S_IWUSR|S_IRUSR|S_IRGRP|S_IROTH); + if (dummy_fd < 0) + goto err; + close(dummy_fd); + /* initialize inotify stuff */ me->fd = inotify_init1(IN_NONBLOCK | IN_CLOEXEC); if (me->fd < 0) goto err; - /* - * libmount uses rename(2) to atomically update utab/mtab, the finame - * change is possible to detect by IN_MOVE_TO inotify event. - */ - wd = inotify_add_watch(me->fd, dirname, IN_MOVED_TO); + + wd = inotify_add_watch(me->fd, filename, IN_CLOSE_NOWRITE); if (wd < 0) goto err; - if (sep && sep > dirname) - *(sep - 1) = '/'; /* set '/' back to the path */ - + free(filename); return me->fd; err: rc = -errno; + free(filename); + if (me->fd) + close(me->fd); + me->fd = -1; DBG(MONITOR, ul_debugobj(mn, "failed to create userspace monitor [rc=%d]", rc)); return rc; } - - /* - * For 'utab' changes we have to monitor all /run/mount directory, this - * function is necessary to avoid false positives. + * drain inotify buffer */ -static int userspace_monitor_verify_change(struct libmnt_monitor *mn, - struct monitor_entry *me) +static void userspace_event_cleanup(struct libmnt_monitor *mn, + struct monitor_entry *me) { - char wanted[NAME_MAX + 1]; char buf[sizeof(struct inotify_event) + NAME_MAX + 1]; - struct inotify_event *event; - char *p; - ssize_t r; - int rc = 0; - DBG(MONITOR, ul_debugobj(mn, "checking fd=%d for userspace changes", me->fd)); - - p = strrchr(me->path, '/'); - if (!p) - p = me->path; - else - p++; - strncpy(wanted, p, sizeof(wanted) - 1); - wanted[sizeof(wanted) - 1] = '\0'; - rc = 0; + if (!me || me->fd < 0) + return; - while ((r = read(me->fd, buf, sizeof(buf))) > 0) { - for (p = buf; p < buf + r; ) { - event = (struct inotify_event *) p; + DBG(MONITOR, ul_debugobj(mn, "drain userspace monitor inotify")); - if (strcmp(event->name, wanted) == 0) - rc = 1; - p += sizeof(struct inotify_event) + event->len; - } - if (rc) - break; - } - - return rc; + /* the 'fd' is non-blocking */ + while (read(me->fd, buf, sizeof(buf)) > 0); } /* @@ -294,7 +288,7 @@ static int userspace_monitor_verify_change(struct libmnt_monitor *mn, static const struct monitor_opers userspace_opers = { .op_get_fd = userspace_monitor_get_fd, .op_close_fd = userspace_monitor_close_fd, - .op_verify_change = userspace_monitor_verify_change + .op_event_cleanup = userspace_event_cleanup }; /** @@ -600,8 +594,9 @@ err: * @mn: monitor * @timeout: number of milliseconds, -1 block indefinitely, 0 return immediately * - * Waits for the next change, after the change it's recommended to verify the - * change by mnt_monitor_next_change() or mnt_monitor_is_changed(). + * Waits for the next change, after the event it's recommended to use + * mnt_monitor_next_change() to get more details about the change or + * at least mnt_monitor_event_cleanup(). * * Returns: 1 success (something changed), 0 timeout, <0 error. */ @@ -632,6 +627,9 @@ int mnt_monitor_wait(struct libmnt_monitor *mn, int timeout) return -EINVAL; me->changed = 1; + if (me->opers->op_event_cleanup != NULL) + me->opers->op_event_cleanup(mn, me); + return 1; /* success */ } @@ -658,25 +656,6 @@ static struct monitor_entry *get_changed(struct libmnt_monitor *mn) * The function does not wait and it's designed to provide details and to avoid * false positives after detected activity on monitor file descriptor. * - * The function is mutually exclusive to mnt_monitor_is_changed(). - * - * Example: - * <informalexample> - * <programlisting> - * fd = mnt_monitor_get_fd(mn); - * - * ... <add 'fd' to your epoll> ... - * - * do { - * if (epoll_wait(efd, events, maxevents, -1) <= 0) - * break; - * - * while (mnt_monitor_next_change(mn, &filename, NULL) == 0) - * printf("%s changed\n", filename); - * } while (1); - * </programlisting> - * </informalexample> - * * Returns: 0 on success, 1 no change, <0 on error */ int mnt_monitor_next_changed(struct libmnt_monitor *mn, @@ -688,12 +667,12 @@ int mnt_monitor_next_changed(struct libmnt_monitor *mn, if (!mn || mn->fd < 0) return -EINVAL; -again: + /* * if we previously called epoll_wait() (e.g. mnt_monitor_waith()) then * info about unread change is already stored in monitor_entry. * - * We we get nothing, then ask kernel. + * If we get nothing, then ask kernel. */ me = get_changed(mn); if (!me) { @@ -715,18 +694,14 @@ again: me = (struct monitor_entry *) events[0].data.ptr; if (!me) return -EINVAL; + if (me->opers->op_event_cleanup != NULL) + me->opers->op_event_cleanup(mn, me); break; } while (1); } me->changed = 0; - if (me->opers->op_verify_change != NULL && - me->opers->op_verify_change(mn, me) != 1) { - DBG(MONITOR, ul_debugobj(mn, " *** false positive")); - goto again; - } - if (filename) *filename = me->path; if (type) @@ -736,6 +711,31 @@ again: return 0; /* success */ } +/** + * mnt_monitor_event_cleanup: + * @mn: monitor + * + * This function cleanups (drain) internal buffers. It's necessary to call + * this function after event if you do not call mnt_monitor_next_change(). + * + * Returns: 0 on success, 1 no change, <0 on error + */ +int mnt_monitor_event_cleanup(struct libmnt_monitor *mn) +{ + struct monitor_entry *me; + struct libmnt_iter itr; + + if (!mn || mn->fd < 0) + return -EINVAL; + + mnt_reset_iter(&itr, MNT_ITER_FORWARD); + while (monitor_next_entry(mn, &itr, &me) == 0) { + if (me->opers->op_event_cleanup != NULL) + me->opers->op_event_cleanup(mn, me); + } + return 0; +} + #ifdef TEST_PROGRAM static struct libmnt_monitor *create_test_monitor(int argc, char *argv[]) @@ -821,6 +821,8 @@ int test_epoll(struct libmnt_test *ts, int argc, char *argv[]) continue; printf(" change detected\n"); + mnt_monitor_event_cleanup(mn); + } while (1); rc = 0; |