[PATCH 06/12] lei: always keep cwd fd {3} for ->fchdir

[Eric Wong]

The extra FD shouldn't cause noticeable overhead in short-lived
workers, and it lets us simplify lei->rel2abs.  Get rid of a
2-argument form of open() while we're at it, since it's been
considered for warning+deprecation by Perl for safety reasons.
---
 lib/PublicInbox/LEI.pm | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index e7f37efaf0a3..0cdcf4492885 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -77,19 +77,16 @@ sub rel2abs {
                return $p;
        }
        my $pwd = $self->{env}->{PWD};
-       my $cwd;
        if (defined $pwd) {
-               my $xcwd = $self->{3} //
-                       ($cwd = getcwd() // die "getcwd(PWD=$pwd): $!");
                if (my @st_pwd = stat($pwd)) {
-                       my @st_cwd = stat($xcwd) or die "stat($xcwd): $!";
+                       my @st_cwd = stat($self->{3}) or die "stat({3}): $!";
                        "@st_pwd[1,0]" eq "@st_cwd[1,0]" or
                                $self->{env}->{PWD} = $pwd = undef;
                } else { # PWD was invalid
                        $self->{env}->{PWD} = $pwd = undef;
                }
        }
-       $pwd //= $self->{env}->{PWD} = $cwd // getcwd() // die "getcwd: $!";
+       $pwd //= $self->{env}->{PWD} = getcwd() // die "getcwd: $!";
        File::Spec->rel2abs($p, $pwd);
 }
 
@@ -558,7 +555,8 @@ sub _lei_atfork_child {
        my ($self, $persist) = @_;
        # we need to explicitly close things which are on stack
        if ($persist) {
-               chdir '/' or die "chdir(/): $!";
+               open $self->{3}, '<', '/' or die "open(/) $!";
+               fchdir($self) or die;
                close($_) for (grep(defined, delete @$self{qw(0 1 2 sock)}));
                if (my $cfg = $self->{cfg}) {
                        delete @$cfg{qw(-lei_store -watches -lei_note_event)};
@@ -568,7 +566,7 @@ sub _lei_atfork_child {
                STDERR->autoflush(1);
                POSIX::setpgid(0, $$) // die "setpgid(0, $$): $!";
        }
-       close($_) for (grep(defined, delete @$self{qw(3 old_1 au_done)}));
+       close($_) for (grep(defined, delete @$self{qw(old_1 au_done)}));
        delete $self->{-socks};
        if (my $op_c = delete $self->{pkt_op_c}) {
                close(delete $op_c->{sock});
@@ -1190,7 +1188,7 @@ sub cfg2lei ($) {
        open($lei->{0}, '<&', \*STDIN) or die "dup 0: $!";
        open($lei->{1}, '>>&', \*STDOUT) or die "dup 1: $!";
        open($lei->{2}, '>>&', \*STDERR) or die "dup 2: $!";
-       open($lei->{3}, '/') or die "open /: $!";
+       open($lei->{3}, '<', '/') or die "open /: $!";
        my ($x, $y);
        socketpair($x, $y, AF_UNIX, SOCK_SEQPACKET, 0) or die "socketpair: $!";
        $lei->{sock} = $x;
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