lei: propagate keyword changes from lei/store

This works with existing inotify/EVFILT_VNODE functionality to
propagate changes made from one Maildir to another Maildir.

I chose the lei/store worker process to handle this since
propagating changes back into lei-daemon on a massive scale
could lead to dead-locking while both processes are attempting
to write to each other.  Eliminating IPC overhead is a nice
side effect, but could hurt performance if Maildirs are slow.

The code for "lei export-kw" is significantly revamped to match
the new code used in the "lei/store" daemon.  It should be more
correct w.r.t. corner-cases and stale entries, but perhaps
better tests need to be written.

squashed:
  t/lei-auto-watch: increase delay for FreeBSD kevent

  My FreeBSD VM seems to need longer for this test than inotify
  under Linux, likely because the kevent support code needs to be
  more complicated.

1 files changed, 11 insertions, 13 deletions

diff --git a/lib/PublicInbox/LeiExportKw.pm b/lib/PublicInbox/LeiExportKw.pm
index 42a5ff22..78c6c6f9 100644
--- a/lib/PublicInbox/LeiExportKw.pm
+++ b/lib/PublicInbox/LeiExportKw.pm
@@ -25,12 +25,11 @@ sub export_kw_md { # LeiMailSync->each_src callback
         }
         $bn .= ':2,'.
                 PublicInbox::LeiToMail::kw2suffix([keys %$sto_kw], @$unknown);
+        return if $bn eq $$id;
         my $dst = "$mdir/cur/$bn";
-        my @fail;
         my $lei = $self->{lei};
         for my $d (@try) {
                 my $src = "$mdir/$d/$$id";
-                next if $src eq $dst;
 
                 # we use link(2) + unlink(2) since rename(2) may
                 # inadvertently clobber if the "uniquefilename" part wasn't
@@ -44,20 +43,19 @@ sub export_kw_md { # LeiMailSync->each_src callback
                         $lei->{sto}->ipc_do('lms_mv_src', "maildir:$mdir",
                                                 $oidbin, $id, $bn);
                         return; # success anyways if link(2) worked
-                }
-                if ($! == ENOENT && !-e $src) { # some other process moved it
-                        $lei->{sto}->ipc_do('lms_clear_src',
-                                                "maildir:$mdir", $id);
-                        next;
-                }
-                push @fail, $src if $! != EEXIST;
+                } elsif ($! == EEXIST) { # lost race with lei/store?
+                        return;
+                } elsif ($! != ENOENT) {
+                        $lei->child_error(1, "E: link($src -> $dst): $!");
+                } # else loop @try
         }
-        return unless @fail;
-        # both tries failed
         my $e = $!;
-        my $orig = '['.join('|', @fail).']';
+        # both tries failed
         my $oidhex = unpack('H*', $oidbin);
-        $lei->child_error(1, "link($orig, $dst) ($oidhex): $e");
+        my $src = "$mdir/{".join(',', @try)."}/$$id";
+        $lei->child_error(1, "link($src -> $dst) ($oidhex): $e");
+        for (@try) { return if -e "$mdir/$_/$$id" }
+        $lei->{sto}->ipc_do('lms_clear_src', "maildir:$mdir", $id);
 }
 
 sub export_kw_imap { # LeiMailSync->each_src callback