support setting No_COW on Perl <5.22

fileno(DIRHANDLE) only works on Perl 5.22+, so we need to use
dirfd(3) ourselves from Inline::C (or rely on chattr(1) being
installed).

While we're at it, rename `set_nodatacow' to `nodatacow_fd'
for consistency with `nodatacow_dir'.

6 files changed, 34 insertions, 20 deletions

diff --git a/lib/PublicInbox/Msgmap.pm b/lib/PublicInbox/Msgmap.pm
index eee8d6ca..e7f7e2c9 100644
--- a/lib/PublicInbox/Msgmap.pm
+++ b/lib/PublicInbox/Msgmap.pm
@@ -51,7 +51,7 @@ sub new_file {
 sub tmp_clone {
         my ($self, $dir) = @_;
         my ($fh, $fn) = tempfile('msgmap-XXXXXXXX', EXLOCK => 0, DIR => $dir);
-        PublicInbox::Spawn::set_nodatacow(fileno($fh));
+        PublicInbox::Spawn::nodatacow_fd(fileno($fh));
         my $tmp;
         if ($self->{dbh}->can('sqlite_backup_to_dbh')) {
                 $tmp = ref($self)->new_file($fn, 2);
diff --git a/lib/PublicInbox/NDC_PP.pm b/lib/PublicInbox/NDC_PP.pm
index 0d20030d..10a7ee2a 100644
--- a/lib/PublicInbox/NDC_PP.pm
+++ b/lib/PublicInbox/NDC_PP.pm
@@ -6,10 +6,8 @@ package PublicInbox::NDC_PP;
 use strict;
 use v5.10.1;
 
-sub set_nodatacow ($) {
-        my ($fd) = @_;
-        return if $^O ne 'linux';
-        defined(my $path = readlink("/proc/self/fd/$fd")) or return;
+sub nodatacow_dir ($) {
+        my ($path) = @_;
         open my $mh, '<', '/proc/self/mounts' or return;
         for (grep(/ btrfs /, <$mh>)) {
                 my (undef, $mnt_path, $type) = split(/ /);
@@ -26,4 +24,11 @@ sub set_nodatacow ($) {
         }
 }
 
+sub nodatacow_fd ($) {
+        my ($fd) = @_;
+        return if $^O ne 'linux';
+        defined(my $path = readlink("/proc/self/fd/$fd")) or return;
+        nodatacow_dir($path);
+}
+
 1;
diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index 0146414c..2b314882 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -20,10 +20,10 @@ sub dbh_new {
                 if ($rw) {
                         require PublicInbox::Spawn;
                         open my $fh, '+>>', $f or die "failed to open $f: $!";
-                        PublicInbox::Spawn::set_nodatacow(fileno($fh));
+                        PublicInbox::Spawn::nodatacow_fd(fileno($fh));
                         my $j = "$f-journal";
                         open $fh, '+>>', $j or die "failed to open $j: $!";
-                        PublicInbox::Spawn::set_nodatacow(fileno($fh));
+                        PublicInbox::Spawn::nodatacow_fd(fileno($fh));
                 } else {
                         $self->{filename} = $f; # die on stat() below:
                 }
diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index 01b9f52d..1cf3e66c 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -18,10 +18,10 @@ use PublicInbox::IdxStack;
 use Carp qw(croak);
 use POSIX qw(strftime);
 use PublicInbox::OverIdx;
-use PublicInbox::Spawn qw(spawn);
+use PublicInbox::Spawn qw(spawn nodatacow_dir);
 use PublicInbox::Git qw(git_unquote);
 use PublicInbox::MsgTime qw(msg_timestamp msg_datestamp);
-our @EXPORT_OK = qw(crlf_adjust log2stack is_ancestor check_size nodatacow_dir);
+our @EXPORT_OK = qw(crlf_adjust log2stack is_ancestor check_size);
 my $X = \%PublicInbox::Search::X;
 my ($DB_CREATE_OR_OPEN, $DB_OPEN);
 our $DB_NO_SYNC = 0;
@@ -109,12 +109,6 @@ sub load_xapian_writable () {
         1;
 }
 
-sub nodatacow_dir ($) {
-        my ($dir) = @_;
-        opendir my $dh, $dir or die "opendir($dir): $!\n";
-        PublicInbox::Spawn::set_nodatacow(fileno($dh));
-}
-
 sub idx_acquire {
         my ($self) = @_;
         my $flag;
diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index 508d43fd..cb16fcf6 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -19,7 +19,7 @@ use strict;
 use parent qw(Exporter);
 use Symbol qw(gensym);
 use PublicInbox::ProcessPipe;
-our @EXPORT_OK = qw/which spawn popen_rd/;
+our @EXPORT_OK = qw/which spawn popen_rd nodatacow_dir/;
 our @RLIMITS = qw(RLIMIT_CPU RLIMIT_CORE RLIMIT_DATA);
 
 my $vfork_spawn = <<'VFORK_SPAWN';
@@ -159,11 +159,12 @@ my $set_nodatacow = $^O eq 'linux' ? <<'SET_NODATACOW' : '';
 #include <sys/vfs.h>
 #include <linux/magic.h>
 #include <linux/fs.h>
+#include <dirent.h>
 #include <errno.h>
 #include <stdio.h>
 #include <string.h>
 
-void set_nodatacow(int fd)
+void nodatacow_fd(int fd)
 {
         struct statfs buf;
         int val = 0;
@@ -185,6 +186,19 @@ void set_nodatacow(int fd)
         if (ioctl(fd, FS_IOC_SETFLAGS, &val) < 0)
                 fprintf(stderr, "FS_IOC_SET_FLAGS: %s\\n", strerror(errno));
 }
+
+void nodatacow_dir(const char *dir)
+{
+        DIR *dh = opendir(dir);
+        int fd;
+
+        if (!dh) croak("opendir(%s): %s", dir, strerror(errno));
+        fd = dirfd(dh);
+        if (fd >= 0)
+                nodatacow_fd(fd);
+        /* ENOTSUP probably won't happen under Linux... */
+        closedir(dh);
+}
 SET_NODATACOW
 
 my $inline_dir = $ENV{PERL_INLINE_DIRECTORY} //= (
@@ -226,7 +240,8 @@ unless (defined $vfork_spawn) {
 unless ($set_nodatacow) {
         require PublicInbox::NDC_PP;
         no warnings 'once';
-        *set_nodatacow = \&PublicInbox::NDC_PP::set_nodatacow;
+        *nodatacow_fd = \&PublicInbox::NDC_PP::nodatacow_fd;
+        *nodatacow_dir = \&PublicInbox::NDC_PP::nodatacow_dir;
 }
 undef $set_nodatacow;
 undef $vfork_spawn;
diff --git a/lib/PublicInbox/Xapcmd.pm b/lib/PublicInbox/Xapcmd.pm
index 8423194f..714f6859 100644
--- a/lib/PublicInbox/Xapcmd.pm
+++ b/lib/PublicInbox/Xapcmd.pm
@@ -3,9 +3,9 @@
 package PublicInbox::Xapcmd;
 use strict;
 use warnings;
-use PublicInbox::Spawn qw(which popen_rd);
+use PublicInbox::Spawn qw(which popen_rd nodatacow_dir);
 use PublicInbox::Over;
-use PublicInbox::SearchIdx qw(nodatacow_dir);
+use PublicInbox::SearchIdx;
 use File::Temp 0.19 (); # ->newdir
 use File::Path qw(remove_tree);
 use File::Basename qw(dirname);