kqnotify|fake_inotify: detect Maildir write ops

We need to detect link(2) and rename(2) in other apps
writing to the Maildir.

We'll be removing the Filesys::Notify::Simple from -watch
in favor of using IO::KQueue or Linux::Inotify2 directly.
Ensure non-inotify emulations can support everything we
expect for Maildir writers.

2 files changed, 71 insertions, 13 deletions

diff --git a/lib/PublicInbox/FakeInotify.pm b/lib/PublicInbox/FakeInotify.pm
index b077d63a..df63173f 100644
--- a/lib/PublicInbox/FakeInotify.pm
+++ b/lib/PublicInbox/FakeInotify.pm
@@ -6,10 +6,13 @@
 package PublicInbox::FakeInotify;
 use strict;
 use Time::HiRes qw(stat);
+use PublicInbox::DS;
 my $IN_CLOSE = 0x08 | 0x10; # match Linux inotify
+# my $IN_MOVED_TO = 0x80;
+# my $IN_CREATE = 0x100;
+sub MOVED_TO_OR_CREATE () { 0x80 | 0x100 }
 
 my $poll_intvl = 2; # same as Filesys::Notify::Simple
-my $for_cancel = bless \(my $x), 'PublicInbox::FakeInotify::Watch';
 
 sub poll_once {
         my ($self) = @_;
@@ -30,8 +33,22 @@ sub new {
 sub watch {
         my ($self, $path, $mask, $cb) = @_;
         my @st = stat($path) or return;
-        $self->{watch}->{"$path\0$mask"} = [ @st, $cb ];
-        $for_cancel;
+        my $k = "$path\0$mask";
+        $self->{watch}->{$k} = [ $st[10], $cb ]; # 10 - ctime
+        bless [ $self->{watch}, $k ], 'PublicInbox::FakeInotify::Watch';
+}
+
+sub on_new_files ($$$$) {
+        my ($dh, $cb, $path, $old_ctime) = @_;
+        while (defined(my $base = readdir($dh))) {
+                next if $base =~ /\A\.\.?\z/;
+                my $full = "$path/$base";
+                my @st = stat($full);
+                if (@st && $st[10] > $old_ctime) {
+                        bless \$full, 'PublicInbox::FakeInotify::Event';
+                        eval { $cb->(\$full) };
+                }
+        }
 }
 
 # behaves like non-blocking Linux::Inotify2->poll
@@ -43,17 +60,32 @@ sub poll {
                 my @now = stat($path) or next;
                 my $prv = $watch->{$x};
                 my $cb = $prv->[-1];
-                # 10: ctime, 7: size
-                if ($prv->[10] != $now[10]) {
+                my $old_ctime = $prv->[0];
+                if ($old_ctime != $now[10]) {
                         if (($mask & $IN_CLOSE) == $IN_CLOSE) {
                                 eval { $cb->() };
+                        } elsif ($mask & MOVED_TO_OR_CREATE) {
+                                opendir(my $dh, $path) or do {
+                                        warn "W: opendir $path: $!\n";
+                                        next;
+                                };
+                                on_new_files($dh, $cb, $path, $old_ctime);
                         }
                 }
-                @$prv = (@now, $cb);
+                @$prv = ($now[10], $cb);
         }
 }
 
 package PublicInbox::FakeInotify::Watch;
-sub cancel {} # noop
+use strict;
+
+sub cancel {
+        my ($self) = @_;
+        delete $self->[0]->{$self->[1]};
+}
+
+package PublicInbox::FakeInotify::Event;
+use strict;
 
+sub fullname { ${$_[0]} }
 1;
diff --git a/lib/PublicInbox/KQNotify.pm b/lib/PublicInbox/KQNotify.pm
index 110594cc..9673b442 100644
--- a/lib/PublicInbox/KQNotify.pm
+++ b/lib/PublicInbox/KQNotify.pm
@@ -7,6 +7,11 @@ package PublicInbox::KQNotify;
 use strict;
 use IO::KQueue;
 use PublicInbox::DSKQXS; # wraps IO::KQueue for fork-safe DESTROY
+use PublicInbox::FakeInotify;
+use Time::HiRes qw(stat);
+
+# NOTE_EXTEND detects rename(2), NOTE_WRITE detects link(2)
+sub MOVED_TO_OR_CREATE () { NOTE_EXTEND|NOTE_WRITE }
 
 sub new {
         my ($class) = @_;
@@ -15,19 +20,28 @@ sub new {
 
 sub watch {
         my ($self, $path, $mask, $cb) = @_;
-        open(my $fh, '<', $path) or return;
+        my ($fh, $cls, @extra);
+        if (-d $path) {
+                opendir($fh, $path) or return;
+                my @st = stat($fh);
+                @extra = ($path, $st[10]); # 10: ctime
+                $cls = 'PublicInbox::KQNotify::Watchdir';
+        } else {
+                open($fh, '<', $path) or return;
+                $cls = 'PublicInbox::KQNotify::Watch';
+        }
         my $ident = fileno($fh);
         $self->{dskq}->{kq}->EV_SET($ident, # ident
                 EVFILT_VNODE, # filter
                 EV_ADD | EV_CLEAR, # flags
                 $mask, # fflags
                 0, 0); # data, udata
-        if ($mask == NOTE_WRITE) {
-                $self->{watch}->{$ident} = [ $fh, $cb ];
+        if ($mask == NOTE_WRITE || $mask == MOVED_TO_OR_CREATE) {
+                $self->{watch}->{$ident} = [ $fh, $cb, @extra ];
         } else {
                 die "TODO Not implemented: $mask";
         }
-        bless \$fh, 'PublicInbox::KQNotify::Watch';
+        bless \$fh, $cls;
 }
 
 # emulate Linux::Inotify::fileno
@@ -48,8 +62,15 @@ sub poll {
         for my $kev (@kevents) {
                 my $ident = $kev->[KQ_IDENT];
                 my $mask = $kev->[KQ_FFLAGS];
-                if (($mask & NOTE_WRITE) == NOTE_WRITE) {
-                        eval { $self->{watch}->{$ident}->[1]->() };
+                my ($dh, $cb, $path, $old_ctime) = @{$self->{watch}->{$ident}};
+                if (!defined($path) && ($mask & NOTE_WRITE) == NOTE_WRITE) {
+                        eval { $cb->() };
+                } elsif ($mask & MOVED_TO_OR_CREATE) {
+                        my @new_st = stat($path) or next;
+                        $self->{watch}->{$ident}->[3] = $new_st[10]; # ctime
+                        rewinddir($dh);
+                        PublicInbox::FakeInotify::on_new_files($dh, $cb,
+                                                        $path, $old_ctime);
                 }
         }
 }
@@ -59,4 +80,9 @@ use strict;
 
 sub cancel { close ${$_[0]} or die "close: $!" }
 
+package PublicInbox::KQNotify::Watchdir;
+use strict;
+
+sub cancel { closedir ${$_[0]} or die "closedir: $!" }
+
 1;