mount: monitor for utab changes with inotify

Parsing the mount table with libmount races against the mount command,
which will handle the actual mounting before updating utab.  This means
the poll event on /proc/self/mountinfo can kick of a reparse in systemd
before the utab information is available.

This change adds in an additional event source using inotify to watch
for changes to utab.  It only watches for IN_MOVED_TO events, matching
libmount behavior of always overwriting this file using rename(2).

This does add a second pass through the mount table parsing when utab is
updated.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/core/manager.h b/src/core/manager.h
index 02535023a3..ab75f902e5 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -182,6 +182,8 @@ struct Manager {
         /* Data specific to the mount subsystem */
         FILE *proc_self_mountinfo;
         sd_event_source *mount_event_source;
+        int utab_inotify_fd;
+        sd_event_source *mount_utab_event_source;
 
         /* Data specific to the swap filesystem */
         FILE *proc_swaps;