am-utils-6.2 - fix Linux NFS recognition of umounts

From: Ian Kent <raven@themaw.net>

Recent Linux NFS uses a simulated attibute cache change detection
method based on ctime. Consequenty the amd use of mtime for this
doesn't work properly for some kernel versions.

The problem seen with some kernel versions is a failure to recognize
umounts.

Updating the parent ctime in step with mtime during umount appears
to fix the problem.

Signed-off-by: Ian Kent <raven@themaw.net>
---
 amd/autil.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/amd/autil.c b/amd/autil.c
index cd9514d..efd18ef 100644
--- a/amd/autil.c
+++ b/amd/autil.c
@@ -709,10 +709,13 @@ am_unmounted(am_node *mp)
     --mp->am_parent->am_fattr.na_nlink;
 
   /*
-   * Update mtime of parent node
+   * Update mtime and ctime of parent node (as ctime is needed for some
+   * Linux NFS kernel versions to properly recognize attribute changes).
    */
-  if (mp->am_parent && mp->am_parent->am_al->al_mnt)
+  if (mp->am_parent && mp->am_parent->am_al->al_mnt) {
     clocktime(&mp->am_parent->am_fattr.na_mtime);
+    mp->am_parent->am_fattr.na_ctime = mp->am_parent->am_fattr.na_mtime;
+  }
 
   if (mp->am_parent && (mp->am_flags & AMF_REMOUNT)) {
     char *fname = xstrdup(mp->am_name);