rewrite Linux nodatacow use in pure Perl w/o system

btrfs is Linux-only at the moment (and likely to remain that way
for practical purposes).  So rely on Linux ABI stability and use
the `syscall' and `ioctl' perlops rather than relying on Inline::C.
Inline::C (and gcc||clang) are monstrous dependencies which we
can't expect users to have.

This makes supporting new architectures more difficult, but new
architectures come along rarely and this reduces the burden for
the majority of Linux users on popular architectures (while
still avoiding the distribution of pre-built binaries).

Link: https://public-inbox.org/meta/YbCPWGaJEkV6eWfo@codewreck.org/

1 files changed, 15 insertions, 21 deletions

diff --git a/t/nodatacow.t b/t/nodatacow.t
index 19247c10..0940d908 100644
--- a/t/nodatacow.t
+++ b/t/nodatacow.t
@@ -1,48 +1,42 @@
 #!perl -w
-# Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict; use v5.10.1; use PublicInbox::TestCommon;
 use File::Temp 0.19;
-use_ok 'PublicInbox::NDC_PP';
+use_ok 'PublicInbox::Syscall';
+
+# btrfs on Linux is copy-on-write (COW) by default.  As of Linux 5.7,
+# this still leads to fragmentation for SQLite and Xapian files where
+# random I/O happens, so we disable COW just for SQLite files and Xapian
+# directories.  Disabling COW disables checksumming, so we only do this
+# for regeneratable files, and not canonical git storage (git doesn't
+# checksum refs, only data under $GIT_DIR/objects).
 
 SKIP: {
         my $nr = 2;
         skip 'test is Linux-only', $nr if $^O ne 'linux';
         my $dir = $ENV{BTRFS_TESTDIR};
         skip 'BTRFS_TESTDIR not defined', $nr unless defined $dir;
-        require_cmd('chattr', 1) or skip 'chattr(1) not installed', $nr;
+
         my $lsattr = require_cmd('lsattr', 1) or
                 skip 'lsattr(1) not installed', $nr;
+
         my $tmp = File::Temp->newdir('nodatacow-XXXX', DIR => $dir);
         my $dn = $tmp->dirname;
 
         my $name = "$dn/pp.f";
         open my $fh, '>', $name or BAIL_OUT "open($name): $!";
-        my $pp_sub = \&PublicInbox::NDC_PP::nodatacow_fd;
-        $pp_sub->(fileno($fh));
+        PublicInbox::Syscall::nodatacow_fh($fh);
         my $res = xqx([$lsattr, $name]);
+
+        BAIL_OUT "lsattr(1) fails in $dir" if $?;
         like($res, qr/C.*\Q$name\E/, "`C' attribute set on fd with pure Perl");
 
         $name = "$dn/pp.d";
         mkdir($name) or BAIL_OUT "mkdir($name) $!";
-        PublicInbox::NDC_PP::nodatacow_dir($name);
+        PublicInbox::Syscall::nodatacow_dir($name);
         $res = xqx([$lsattr, '-d', $name]);
         like($res, qr/C.*\Q$name\E/, "`C' attribute set on dir with pure Perl");
-
-        $name = "$dn/ic.f";
-        my $ic_sub = \&PublicInbox::Spawn::nodatacow_fd;
-        $pp_sub == $ic_sub and
-                skip 'Inline::C or Linux kernel headers missing', 2;
-        open $fh, '>', $name or BAIL_OUT "open($name): $!";
-        $ic_sub->(fileno($fh));
-        $res = xqx([$lsattr, $name]);
-        like($res, qr/C.*\Q$name\E/, "`C' attribute set on fd with Inline::C");
-
-        $name = "$dn/ic.d";
-        mkdir($name) or BAIL_OUT "mkdir($name) $!";
-        PublicInbox::Spawn::nodatacow_dir($name);
-        $res = xqx([$lsattr, '-d', $name]);
-        like($res, qr/C.*\Q$name\E/, "`C' attribute set on dir with Inline::C");
 };
 
 done_testing;