[PATCH v2] virtiofsd: use GDateTime for formatting timestamp for debug messages

["Daniel P. Berrangé" <berrange@redhat.com>]

The GDateTime APIs provided by GLib avoid portability pitfalls, such
as some platforms where 'struct timeval.tv_sec' field is still 'long'
instead of 'time_t'. When combined with automatic cleanup, GDateTime
often results in simpler code too.

Localtime is changed to UTC to avoid the need to grant extra seccomp
permissions for GLib's access of the timezone database.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 tools/virtiofsd/passthrough_ll.c | 25 ++++---------------------
 1 file changed, 4 insertions(+), 21 deletions(-)

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 49c21fd855..9858e961d9 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -3559,10 +3559,6 @@ static void setup_nofile_rlimit(unsigned long rlimit_nofile)
 static void log_func(enum fuse_log_level level, const char *fmt, va_list ap)
 {
     g_autofree char *localfmt = NULL;
-    struct timespec ts;
-    struct tm tm;
-    char sec_fmt[sizeof "2020-12-07 18:17:54"];
-    char zone_fmt[sizeof "+0100"];
 
     if (current_log_level < level) {
         return;
@@ -3574,23 +3570,10 @@ static void log_func(enum fuse_log_level level, const char *fmt, va_list ap)
             localfmt = g_strdup_printf("[ID: %08ld] %s", syscall(__NR_gettid),
                                        fmt);
         } else {
-            /* try formatting a broken-down timestamp */
-            if (clock_gettime(CLOCK_REALTIME, &ts) != -1 &&
-                localtime_r(&ts.tv_sec, &tm) != NULL &&
-                strftime(sec_fmt, sizeof sec_fmt, "%Y-%m-%d %H:%M:%S",
-                         &tm) != 0 &&
-                strftime(zone_fmt, sizeof zone_fmt, "%z", &tm) != 0) {
-                localfmt = g_strdup_printf("[%s.%02ld%s] [ID: %08ld] %s",
-                                           sec_fmt,
-                                           ts.tv_nsec / (10L * 1000 * 1000),
-                                           zone_fmt, syscall(__NR_gettid),
-                                           fmt);
-            } else {
-                /* fall back to a flat timestamp */
-                localfmt = g_strdup_printf("[%" PRId64 "] [ID: %08ld] %s",
-                                           get_clock(), syscall(__NR_gettid),
-                                           fmt);
-            }
+            g_autoptr(GDateTime) now = g_date_time_new_now_utc();
+            g_autofree char *nowstr = g_date_time_format(now, "%Y-%m-%d %H:%M:%S.%f%z");
+            localfmt = g_strdup_printf("[%s] [ID: %08ld] %s",
+                                       nowstr, syscall(__NR_gettid), fmt);
         }
         fmt = localfmt;
     }
-- 
2.31.1