diff --git a/userspace/marsadm b/userspace/marsadm
index 1acf358d..5cc6164e 100755
--- a/userspace/marsadm
+++ b/userspace/marsadm
@@ -550,20 +550,32 @@ sub get_minmax_replays {
 
 my %visited_pos;
 
+sub _visit {
+  my ($nr, $peer) = @_;
+  $nr =~ s:^0*::;
+  my $visit = "$nr,$peer";
+  $visited_pos{$visit} = 1;
+}
+
+sub _is_visited {
+  my ($nr, $peer) = @_;
+  $nr =~ s:^0*::;
+  my $visit = "$nr,$peer";
+  return $visited_pos{$visit};
+}
+
 sub _parse_pos {
   my ($pos, $do_remember) = @_;
-  $pos =~ m/((?:log|version)-([0-9]+)-([^,]+)(?:,([0-9]+))?)/ or ldie "cannot parse '$pos'\n";
-  if ($do_remember) {
-    my $visit = "$2,$3";
-    $visited_pos{$visit} = 1;
-  }
+  $pos =~ m/((?:log|version)-([0-9]+)-([^,]+)(?:,([0-9]+))?)/ or lwarn "cannot parse position info '$pos'\n";
+  _visit($2, $3) if $do_remember;
   return ($1, int($2), $3, defined($4) ? int($4) : -1);
 }
 
 sub _get_prev_pos {
-  my ($basedir, $nr, $host) = @_;
-  my $path = sprintf("$basedir/version-%09d-$host", $nr);
-  my $vers = get_link($path, 1);
+  my ($basedir, $nr, $peer, $do_remember) = @_;
+  my $path = sprintf("$basedir/version-%09d-$peer", $nr);
+  my $vers = get_link($path, 2);
+  _parse_pos($path, 1) if $do_remember && defined($vers) && $vers;
   $vers =~ s/^.*://;
   return $vers;
 }
@@ -647,30 +659,39 @@ sub detect_splitbrain {
 }
 
 sub _mark_path_backward {
-  my ($basedir, $pos) = @_;
+  my ($basedir, $pos, $peer, $skip_last) = @_;
+  my $sum = 0;
   for (;;) {
     my ($p, $nr, $from, $len) = _parse_pos($pos, 1);
-    $pos = _get_prev_pos($basedir, $nr, $from);
+    _visit($nr, $peer);
+    $pos = _get_prev_pos($basedir, $nr, $peer, 1);
     last if !$pos;
+    # optionally don't count the last versionlink, pointing into nirvana
+    if (defined($skip_last) && $skip_last && $nr > 1) {
+      my ($p, $nr, $from, $len) = _parse_pos($pos, 0);
+      last if !$p;
+      my $next = _get_prev_pos($basedir, $nr, $peer, 1);
+      last if !$next;
+    }
+    $sum += $len;
   }
+  return $sum;
 }
 
 sub _mark_path_forward {
-  my ($basedir, $pos) = @_;
+  my ($basedir, $pos, $peer) = @_;
   my @list = ($pos);
   while (@list) {
     my %next_list;
     foreach $pos (@list) {
       my ($p, $nr, $from, $len) = _parse_pos($pos, 1);
-      my $next = sprintf("$basedir/version-%09d-*", $nr + 1);
-      my @candidates = glob($next);
-      foreach my $cand (@candidates) {
-	my $vers = get_link($cand, 1);
-	$vers =~ s/^.*://;
-	my ($cp, $cnr, $cfrom, $clen) = _parse_pos($vers, 0);
-	if (int($cnr) == int($nr) && $cfrom eq $from && $clen == $len) {
-	  $next_list{$cand} = 1;
-	}
+      my $cand = sprintf("$basedir/version-%09d-$peer", $nr + 1);
+      my $vers = get_link($cand, 2);
+      next unless defined($vers) && $vers ne "";
+      $vers =~ s/^.*://;
+      my ($cp, $cnr, $cfrom, $clen) = _parse_pos($vers, 0);
+      if (int($cnr) == int($nr) && $cfrom eq $from && $clen == $len) {
+	$next_list{$cand} = 1;
       }
     }
     @list = keys(%next_list);
@@ -684,20 +705,82 @@ sub _mark_path_transitive {
 
 sub log_purge_res {
   my ($cmd, $res) = @_;
+  lwarn "DANGEROUS OPERATION: $cmd on resource '$res'\n";
+  my %start_logs;
+  my $start_count = 0;
   my $basedir = "$mars/resource-$res";
-  my @files = glob("$basedir/{log,version}-*");
-  foreach my $replay (glob("$basedir/replay-*")) {
+  foreach my $data (glob("$basedir/{data,replay}-*")) {
+    $data =~ m:/(data|replay)-(.+):;
+    my $peer = $2;
+    my $replay = "$basedir/replay-$peer";
     my $target = get_link($replay, 1);
-    _mark_path_transitive($basedir, $target);
+    lprint "found replay link '$replay' -> '$target'\n";
+    $target =~ s/,.*//;
+    $start_logs{$target}++;
+    $start_count++;
+    _mark_path_transitive($basedir, $target, $peer);
   }
-  foreach my $file (@files) {
-    $file =~ m:/((log|version)-([0-9]+)-([^,]+)): or ldie "bad path '$file'\n";
-    next if (!$force && $4 ne $host);
-    my $visit = "$3,$4";
-    lprint "checking '$1'\n";
-    next if $visited_pos{$visit};
+  if (!$start_count) {
+    ldie "Resource contains no valid information - refusing to delete everything for safety reasons\n";
+  }
+  my %logs;
+  foreach my $file (glob("$basedir/version-*")) {
+    $file =~ m:/(version-([0-9]+)-([^,]+)): or ldie "bad path '$file'\n";
+    my $cand = $1;
+    my $nr = $2;
+    my $from = $3;
+    lprint "checking '$cand'\n";
+    my $vers = get_link($file, 1);
+    $vers =~ m/(log-[0-9]+-[^,:]+)/;
+    my $log = $1;
+    lprint "  corresponding logfile is '$log'\n";
+    $logs{$log}++;
+    if (_is_visited($nr, $from)) {
+      lprint "  ok '$cand'\n";
+      next;
+    }
+    if (!$force && $from ne $host) {
+      lprint "  skipping foreign object '$cand'\n";
+      next;
+    }
+    lwarn "deleting foreign object from peer '$from' because you said --force\n" if $from ne $host;
     _create_delete($file);
   }
+  foreach my $file (glob("$basedir/log-*")) {
+    $file =~ m:/(log-[0-9]+-(.*)): or ldie "bad path '$file'\n";
+    my $log = $1;
+    my $from = $2;
+    lprint "checking '$log'\n";
+    if ($logs{$log}) {
+      lprint "  ok '$log'\n";
+      $logs{$log} = -1;
+      next;
+    }
+    if ($start_logs{$log}) {
+      lprint "  ok start '$log'\n";
+      $logs{$log} = -1;
+      next;
+    }
+    if (!$force && $from ne $host) {
+      lprint "  skipping foreign object '$log'\n";
+      next;
+    }
+    lwarn "deleting foreign object from peer '$from' because you said --force\n" if $from ne $host;
+    _create_delete($file);
+  }
+  my $count = 0;
+  foreach my $log (sort(keys(%logs))) {
+    my $nr = $logs{$log};
+    next if $nr < 0 || -e "$basedir/$log";
+    lprint_stderr "info: logfile '$log' is referenced ($nr), but not present.\n";
+    $count++;
+  }
+  if ($count) {
+    lprint_stderr "  Unreferenced logfiles are not necessarily bad.\n";
+    lprint_stderr "  They can regularly appear after 'leave-resource',\n";
+    lprint_stderr "  or 'invalidate', or after emergency mode,\n";
+    lprint_stderr "  or after similar operations.\n";
+  }
   finish_links();
   _wait_delete();
 }