searchidx: disable CoW for SQLite and Xapian under btrfs

[public-inbox.git] / lib / PublicInbox / NDC_PP.pm

diff --git a/lib/PublicInbox/NDC_PP.pm b/lib/PublicInbox/NDC_PP.pm
new file mode 100644 (file)
index 0000000..0d20030
--- /dev/null
+++ b/lib/PublicInbox/NDC_PP.pm
@@ -0,0 +1,29 @@
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Pure-perl class for Linux non-Inline::C users to disable COW for btrfs
+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;
+       open my $mh, '<', '/proc/self/mounts' or return;
+       for (grep(/ btrfs /, <$mh>)) {
+               my (undef, $mnt_path, $type) = split(/ /);
+               next if $type ne 'btrfs'; # in case of false-positive from grep
+
+               # weird chars are escaped as octal
+               $mnt_path =~ s/\\(0[0-9]{2})/chr(oct($1))/egs;
+               $mnt_path .= '/' unless $mnt_path =~ m!/\z!;
+               if (index($path, $mnt_path) == 0) {
+                       # error goes to stderr, but non-fatal for us
+                       system('chattr', '+C', $path);
+                       last;
+               }
+       }
+}
+
+1;