marsadm: improve primary/secondary command behaviour

Previously, the 'marsadm primary' and 'marsadm secondary' commands
were successful as soon as the target primary was successfully set
to the new primary or '(none)', respectively.  This commit appends
a check to wait until the primary is really changed (actual state).

Changes in marsadm:
- Added check_primary_settled() function
- Do not use local variable named '$host' in _primary_res() since
  a global variable with same name exists.
- Do not use/set global variable '$host' in primary_res().  Use
  local variable '$new' initially set to '$host' instead.
- Make 'secondary' command idempotent ("is already secondary")
- Call trigger() and check_primary_settled() in primary_res()

Related minor changes:
- marsadm: Added optional parameter 'sleeptime' to sleep_timeout()
- Removed debug output in check_file_aged()

Signed-off-by: Thomas Schoebel-Theuer <tst@1und1.de>

userspace/marsadm

@@ -79,13 +79,14 @@ sub mars_time {
 }
 
 sub sleep_timeout {
+  my $sleeptime = shift || 5;
   if ($timeout < 0) {
-    sleep(5);
+    sleep($sleeptime);
     return;
   }
   ldie "Timeout reached. You may retry with --timeout=-1 to ensure waiting until progress is possible.\n" if !$timeout;
   my $rest = $timeout;
-  $rest = 5 if $rest > 5;
+  $rest = $sleeptime if $rest > $sleeptime;
   sleep($rest);
   $timeout -= $rest;
 }
@@ -184,6 +185,17 @@ sub check_primary_gone {
   }
 }
 
+sub check_primary_settled {
+    my ($res) = @_;
+    my $target_primary = readlink("$mars/resource-$res/primary");
+    for (;;) {
+      my $actual_primary = _get_actual_primary($res) || '(none)';
+      last if ($target_primary eq $actual_primary);
+      lprint "waiting for primary $target_primary to be settled\n";
+      sleep_timeout(2);
+    }
+}
+
 sub check_todo {
   my ($res, $key, $val, $wait) = @_;
   for (;;) {
@@ -233,9 +245,7 @@ sub _check_file_aged {
     $reftime = time();
   }
   return 2 if (!$mtime or !$reftime);  # error -> file is aged
-  my $res = ($mtime < $reftime - $age) ? 1 : 0;
+  return ($mtime < $reftime - $age) ? 1 : 0;
-  lprint sprintf("%s: %s <=> %s ==> %s\n", $path, scalar(gmtime($mtime)), scalar(gmtime($reftime)), $res);
-  return $res;
 }
 
 #
@@ -854,40 +864,47 @@ sub fake_local_res {
 }
 
 sub _primary_res {
-  my ($res, $host, $old) = @_;
+  my ($res, $new, $old) = @_;
   my $tmp = "$mars/resource-$res/.tmp.primary";
   my $pri = "$mars/resource-$res/primary";
   system("rm -f $tmp");
-  symlink($host, $tmp) or ldie "cannot create new primary symlink\n";
+  symlink($new, $tmp) or ldie "cannot create new primary symlink\n";
   rename($tmp, $pri) or ldie "cannot install new primary symlink\n";
-  lprint "primary will change from '$old' to '$host'\n";
+  lprint "target primary changed from '$old' to '$new'\n";
 }
 
 sub primary_res {
   my ($cmd, $res) = @_;
   my $sec = ($cmd eq "secondary");
   my $old = _get_actual_primary($res) || '(none)';
+  my $new = $host;
   if ($sec) {
+    if ($old eq '(none)') {
+      lprint "resource is already secondary\n";
+      exit(0);
+    }
     ldie "for safety reasons, switching to secondary is only allowed when I ($host) am primary\n" if ($old ne $host) && !$force;
-    $host = "(none)";
+    $new = "(none)";
-  } elsif ($old eq $host) {
+  } elsif ($old eq $new) {
     lprint "I am already primary.\n";
     exit(0);
   } elsif ($force) {
     lprint "FORCING myself ($host) to primary...\n";
   } elsif (! -d "/proc/sys/mars") {
     ldie "cannot switch to primary: mars kernel module is not loaded\n";
-  } elsif (readlink("$mars/resource-$res/actual-$host/is-primary")) {
-    lwarn "I am actually primary: skipping check to set me back.\n";
   } else { # try to switch myself to primary
-    lprint "trying to switch $host to primary...\n";
+    lprint "trying to switch $new to primary...\n";
-    check_sync_finished($res, $host);
+    check_sync_finished($res, $new);
     check_todo($res, "connect", 1, 1);
     _primary_res($res, "(none)", $old) unless $old eq "(none)";
+    _trigger();
     check_primary_gone($res);
-    check_splitbrain($res, $host, -1);
+    check_splitbrain($res, $new, -1);
   }
-  _primary_res($res, $host, $old);
+  _primary_res($res, $new, $old);
+  _trigger();
+  check_primary_settled($res);
+  lprint "primary successfully changed to $new\n";
 }
 
 sub invalidate_res {